燃料化学学报（中英文）

Theoretical study on the pyrolysis mechanism of the lignin dimer model compound catalyzed by alkaline earth metal ions Ca²⁺ and Mg²⁺

JIANG Xiaoyan, LI Yiming, TANG Li, DU Xiaojiao, DAI Lanhua, HU Bin

, Available online , doi: 10.1016/S1872-5813(24)60441-X

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Abstract:
It is essential to investigate the influence of alkaline earth metals on the pyrolysis mechanism and resulting products of lignin to enhance the efficient thermochemical conversion and utilization of lignin or biomass. In this study, the Density functional theory method was used to simulate the pyrolytic reaction pathways of a β-O-4 type lignin dimer model compound (1-methoxy-2-(4-methoxyphenethoxy)benzene, mc) affected by alkaline earth metal ions Ca²⁺ and Mg²⁺. The computational findings suggest that Ca²⁺ and Mg²⁺ tend to combine with the oxygen atom at the C_β position and the oxygen atom on the methoxy group of the lignin dimer model compound, forming stable complexes that modify the bond lengths of the C_α–C_β and C_β–O bonds and affect their pyrolysis energy barriers. During the catalytic pyrolysis process, the presence of Ca²⁺ and Mg²⁺ can promote the concerted decomposition reaction, leading to increased production of products like 1-methoxy-4-vinylbenzene, 2-methoxyphenol and catechol. Meanwhile, they can suppress homolytic cleavage reactions of the C_β–O and C_α–C_β bonds, thereby hindering the formation of other products such as 1-ethyl-4-methoxybenzene and 2-hydroxybenzaldehyde.

Impact of B-site cations of MgX₂O₄ (X=Mn, Fe, Cr) spinels on the chemical looping oxidative dehydrogenation of ethane to ethylene

LIANG Xiaocen, WANG Xuemei, XING Zifan, MAO Min, SONG Da, LI Yang, LONG Tao, ZHOU Yuchao, CHEN Peili, HE Fang

, Available online , doi: 10.1016/S1872-5813(24)60434-2

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Chemical looping oxidative dehydrogenation (CL-ODH) provides a multifunctional conversion platform that can take advantage of the selective oxidation of lattice oxygen in oxygen carrier to achieve high-valued ethane to ethylene conversion. In this study, we explored the effect of B-site element in MgX₂O₄ (X=Cr, Fe, or Mn) spinel-type oxygen carriers on the performance of ethane CL-ODH. The properties test and characterization of MgX₂O₄ spinel were tested by fixed bed and H₂-TPR, O₂-TPD, TG, in-situ Raman, SEM, and TEM. The results showed that because MgCr₂O₄ only released a small amount of adsorbed surface oxygen, it tended to catalyze the conversion of ethane to coke and hydrogen. MgFe₂O₄ facilitated the deep oxidation of ethane into CO₂ by providing more surface lattice oxygen. Meanwhile, since a significant amount of bulk lattice oxygen was released by the MgMn₂O₄ oxygen carrier, it could burn hydrogen in a targeted manner to advance the reaction and increased ethylene's selectivity. Thereby, MgMn₂O₄ achieved an ethane conversion of 73.7% with an ethylene selectivity of 81.46%. Furthermore, the MgMn₂O₄ catalyst demonstrated stable reactivity and an ethylene yield of about 62% in ethane CL-ODH over the 30 redox cycles. The screening tests indicated that the B-site elements in MgX₂O₄ spinel oxides could significantly influence their ability to supply lattice oxygen, thereby affecting their performance in ethane CL-ODH reaction.

Recent contributions of photoionization mass spectrometry in the study of typical solid fuel pyrolysis

SHEN Yang, CUI Cunhao, LIU Haoran, REN Hairong, CAI Jianghuai, ZHOU Zhongyue, QI Fei

, Available online , doi: 10.1016/S1872-5813(23)60411-6

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Pyrolysis, an economically viable method, thermochemically converts solid fuel into transportation fuels and value-added chemicals, such as clean gas, liquid fuels, and chemicals, alongside undesirable by-products. Photoionization mass spectrometry (PIMS) is a versatile technique for real-time process analysis, offering ‘soft’ ionization for complex analytes, detecting and analyzing ions during in-situ pyrolysis. This review focuses on recent applications of PIMS during pyrolysis of solid fuels (i.e. coal, biomass and energetic materials). It summarizes studies on mass spectrometric analysis combined with different reactors and highlights the benefits othrough online PIMS as a diagnostic tool for in situ analysis. It provides an overview of interplay between experimental advancements and models and discusses future perspectives, potential applications in support of mechanistic studies.

CO₂ Assistant Oxidative Dehydrogenation of Isobutane to Isobutene Catalyzed by ZnCaZr Solid Solution

LIU Yupeng, LIU Lingji, YU Xiaosheng, WANG Yongzhao, LI Guoqiang, LI Lei, WANG Changzhen

, Available online , doi: 10.19906/j.cnki.JFCT.2024003

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CO₂-assisted oxidative dehydrogenation of isobutane to isobutene (CO₂-BDH) is an environmentally friendly low-carbon dehydrogenation process, which can effectively utilize greenhouse gas CO₂ while producing value-added product isobutylene. Besides, the soft oxidizing property of CO₂ can break the thermodynamic limitation of dehydrogenation reaction and avoid the problem of deep oxidation, which makes isobutylene highly selective. However, its industrialization is still challenged by the lack of green and efficient catalysts. In this work, xZn-CaZr solid solution catalysts was prepared by one-pot co-precipitation method and applied to CO₂-BDH reaction. The physicochemical properties of all catalysts were investigated by various means, and the structure-activity relationship and surface redox mechanism were described in combination with catalytic performance. The results show that xZn-CaZr catalysts formed solid solution structure with Zn species (6%−12%) existing in highly dispersion state, and the "confinement effect" given by mesoporous skeleton and strong metal-support interactions contributes to the stable distribution of nanoscale sites and generates more Zn-O-Zr interfaces. When excessive Zn species (16%) is added, the ZnO crystal will have obvious phase separation from the solid solution phase. The surface chemical states of different catalysts were analyzed by XPS, and it was found that the relative content of O_β increased first and then decreased with the increase of Zn content. In addition, the surface reduction characteristics of the catalyst indicated that the promotion of an appropriate amount of Zn species can improve the mobility of lattice oxygen, thus 0.4Zn-CaZr catalyst showing the highest relative content of O_β and the best oxygen conductivity. In the activity evaluation of different xZn-CaZr catalyst, 0.4Zn-CaZr catalyst shows the best catalytic dehydrogenation activity but its stability is poor, while 0.2Zn-CaZr catalyst has the best reaction stability. Moreover, the catalytic performance of ZnCaZr catalyst under different C₄H₁₀-CO₂ ratios was also investigated, which indicated that the higher CO₂ content in the feed gas was helpful to improve the catalytic stability and isobutene selectivity. Combined with the surface chemical state and carbon deposition information of the spent catalyst, it was found that the relative content of O_β on the surface of 0.4Zn-CaZr catalyst decreases obviously, but the carbon deposition rate was slow. On the contrary, the relative content of O_β for 0.2Zn-CaZr catalyst decreased less, but its carbon deposition rate was faster. We believe that the amount and mobility of lattice oxygen over xZn-CaZr catalysts were revealed as key factors in determining the catalytic performance. Notably, higher content and superior mobility of lattice oxygen can enhance the redox function of the solid solution catalyst itself and improve the activation performance of CO₂. The strong oxygen supply capacity can ensure the continuous MvK catalytic cycle on the Zn-O-Zr interface, and avoid the deep accumulation of inert carbon deposits while improving the dehydrogenation activity of isobutane and selectivity of isobutene. This study shed lights on the further design and development of green and efficient CO₂-BDH catalysts.

Research on coking performance of ethylene residue pitch components

ZHANG Tongtong, ZHU Huihui, ZHU Yaming, HU Chaoshuai, LV Jun, CHENG Junxia, BAI Yonghui, ZHAO Xuefei

, Available online , doi: 10.1016/S1872-5813(24)60435-4

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Ethylene residue pitch (the heavy component in ethylene residue tar) was widely used as the preferred raw material for preparing petroleum based artificial carbon materials with the characteristics of high carbon content, high aromaticity, and low heteroatom (S, N) content. In order to a detailed study on the coking properties of ethylene residue pitch, 8 components of ethylene residue pitch (four soluble and four insoluble components) were obtained by extraction and separation method. Factually, methanol, n-butanol, n-hexane, and dimethyl sulfoxide were selected as the solvents to extract and separate the ethylene residue pitch. A series of petroleum based pitch coke were gained by the thermal conversion and carbonization treatment (thermal conversion temperature and carbonization temperature were 500 and 1400 ℃, respectively) of each pitch components. The basic physical properties of ethylene residue pitch components were studied using infrared spectroscopy, thermogravimetric analysis, and ¹H-NMR. The micro-structure of a series of petroleum based pitch coke was studied by polarizing microscopy, X-ray single crystal diffraction, Raman spectroscopy, scanning electron microscopy. The results shown that: The aromaticity of insoluble components in ethylene residue pitch is slightly higher than that of soluble components, and the branching chains of insoluble components are slightly less than those of soluble components. The microstrength of ethylene residue pitch coke obtained by thermal conversion and carbonization of insoluble components is higher than that of ethylene residue pitch coke obtained by soluble components, and the true density of ethylene residue pitch coke HS-C is as high as 2.0554 g/cm³.

Preparation of Co_0.5Cu_0.5/CNR catalyst and its performance in hydrogen production by hydrolysis of ammonia borane

ZUO Youhua, LI Rong, HUA Junfeng, HAO Siyu, XIE Jing, XU Lixin, YE Mingfu, WAN Chao

, Available online , doi: 10.1016/S1872-5813(24)60442-1

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Solution A was prepared with cobalt nitrate and copper nitrate, and solution B was prepared with phenyldicarboxylic acid(PTA) and N,N-dimethylformamide(DMF), and the two solutions were used to prepare Co/Cu Lavashield skeleton series materials(Co/Cu-MIL precursors) by solvothermal method, and the further direct carbonization of the precursor system prepared the MOFs derivatives, i.e., bimetallic carbon nanorods(Co_xCu_1−x/CNR) catalyst. The morphology and composition were explored by SEM, TEM, XRD, XPS and other characterization means. The results showed that Co_xCu_1−x/CNR was successfully obtained after Co/Cu-MIL was roasted at high temperature, and the catalytic activity of the catalyst obtained was optimal when x=0.5, the solvent heat temperature was 120°C, and the roasting temperature was 650 ℃. The TOF value of the Co_0.5Cu_0.5/CNR catalyst catalyzed the hydrolysis of ammonia borane (AB) for the production of hydrogen was 2718.21 h⁻¹, and the reaction The activation energy was 51.64 kJ/mol, and the catalyst had good cycling stability, and the catalytic activity decreased after 10 cycles, but still maintained 100% conversion of AB.

Role of interfacial effects in the oxidation of toluene by MnO_x-modified CeO₂ nanocubes

YE Peng, WU Qilong, TIAN Xi, SONG Hua, GAN Lina

, Available online , doi: 10.19906/j.cnki.JFCT.2024010

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Toluene, a common volatile organic compounds (VOCs), can have adverse effects on the natural environment as well as on human health. Catalytic oxidation technology can remove toluene economically and efficiently, and the key to this technology is the development of efficient catalysts. In order to improve the oxidation efficiency of toluene, it is of great significance to explore and study new efficient catalysts. In this study, binary xMn/Ce (xMnO_x/CeO₂) catalysts with different Mn loadings were successfully prepared by a two-step hydrothermal-impregnation method, and the performance of these catalysts was evaluated in the catalytic oxidation reaction of toluene. The results showed that the introduction of MnO_x significantly increased the toluene oxidation activity of the catalysts. In particular, when the Mn loading was 10% (10Mn/Ce), the t₉₀ (temperature at which toluene conversion reached 90%) was only 233 ℃ at gas hourly space velocity of 60000 mL/(g·h), showing optimal toluene catalytic oxidation activity. This result suggests that the addition of moderate amount of MnO_x can significantly improve the catalytic performance of the catalysts. By characterization means such as X-ray diffraction (XRD), Raman, transmission electron microscopy (TEM), programmed temperature-raising reduction (H₂-TPR), and X-ray photoelectron spectroscopy (XPS), we found that the incorporation of MnO_x creates an interfacial effect between MnO_x and CeO₂, which significantly alters the physicochemical properties of the Mn/Ce catalysts. Due to the interfacial effect, the concentration of Ce³⁺ and Mn³⁺ ions and the oxygen vacancy in the 10Mn/Ce catalyst were not only increased, but also the strength of Ce−O bond on the catalyst surface was reduced, which made it easier for surface lattice oxygen to participate in the catalytic oxidation of toluene, and enhanced the redox performance of the catalyst, thus promoting the catalytic oxidation of toluene. In this study, we not only successfully prepared Mn/Ce catalysts with excellent toluene oxidation activity, but also revealed the mechanism of interfacial effect behind it, which provides a simple and effective method and idea for the design and preparation of efficient oxidation catalysts for VOCs.

Refined Ni, Co-Induced Synthesis of NiCoP Nanoparticles Uniformly Embedded in NCNTs: A Robust Dual-Functional Electrocatalyst for Water Splitting

ZHANG Xupeng, ZHAN Junling, WANG Ying, LIU Qun, ZHANG Yu, WANG Jiabo, CHEN Li

, Available online , doi: 10.1016/S1872-5813(24)60446-9

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Ni, Co-induced highly distributed NiCoP nanoparticles embedded nitrogen-doped carbon nanotubes (NCNTs) (NiCo/NiCoP-NCNTs) were directly synthesized by a one-step phosphorization and carbonization process. As a bifunctional electrocatalyst for water splitting, NiCo/NiCoP NCNTs show impressive catalytic performance with an overpotential of only 206 mV for the hydrogen evolution reaction and 360 mV for the oxygen evolution reaction in 0.5 M H₂SO₄ and 1 M KOH solutions, respectively. In addition, NiCo/NiCoP NCNTs maintain a stable cell voltage of 1.68 V at 10 mA cm^-2 with only a 10% decrease in current density over 48 hours, showing remarkable stability. The improved catalytic activity can be attributed to the integration of NiCoP nanoparticles and the synergies between NCNTs and NiCo alloy. Additionally, the improved electrocatalytic performance can be attributed to the increased electrochemically active surface area and the reduced electron transfer resistance of the NiCo/NiCoP-NCNTs. Overall, the NiCo/NiCoP-NCNTs demonstrated significant performance for advanced water electrolysis applications.

The promotional effects of ZrO₂ modification on the activity and selectivity of Co/SiC catalysts for Fischer-Tropsch synthesis

WANG Min, GUO Shupeng, XU Jinshan, LI Liuzhong, CHEN Congbiao, MA Zhongyi, JIA Litao, HOU Bo, LI Debao

, Available online , doi: 10.1016/S1872-5813(24)60439-1

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Co/SiC catalysts have exhibited excellent performance in Fischer-Tropsch synthesis reaction.,However, few research focuses on investigating the effect of SiC supports surface properties of on catalyst performance. In this study, ZrO₂ was utilized to modify the SiC surface,leading to the preparation of a series of Co-ZrO₂/SiC catalysts. The physicochemical properties of the catalyst were comprehensively analyzed by using N₂ adsorption, XRD, H₂-TPR, XPS analyses. Catalytic performance was evaluated using a fixed bed reactor, shedding light on the effect of ZrO₂ modified SiC support on cobalt-based Fischer-Tropsch synthesis catalysts. The results indicated that ZrO₂ surface modification on SiC resulted in an enhanced reduction degree of Co/SiC catalysts. Additionally, ZrO₂ exhibited strong interaction with the amorphous phase on the SiC surface, thereby weakening the interaction between Co and the amorphous phase., This led to an increase in the electron density of cobalt species, consequently improving the selectivity of Co/SiC catalysts towards long-chain hydrocarbons.

Theoretical Calculations of Pyridine Adsorption on the Surfaces of Ti, Zr, N Doped Graphene

WANG Jucai, TANG Ke, SUN Xiaodi, HONG Xin

, Available online , doi: 10.1016/S1872-5813(24)60440-8

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The removal of nitrides from diesel fuel has important significance for the environment and human health. The adsorption behaviour of Ti, Zr and N-doped and intrinsic graphene on pyridine, a typical basic nitride in diesel fuel, has been investigated by density functional methods in this paper. the corresponding adsorption energy, adsorption configurations, Mulliken charge transfer, differential charge density, and density of states were discussed. The results show that metal Ti and Zr doping can significantly enhance the adsorption energy between pyridine and graphene surfaces, and non-metal N doping can slightly increase the adsorption energy between pyridine and graphene surfaces. The magnitude of the adsorption energy of pyridine on the surface of graphene modified with different atoms was in the order of Ti doped graphene > Zr doped graphene > N doped graphene > intrinsic graphene, Pyridine could undergo N-Ti, N-Zr and π-π interactions with Ti and Zr doped graphene, and N-N, C-N and π-π interactions with N doped graphene and intrinsic graphene. Further analysis reveals that there are obvious electron transfer and chemical bond formation between pyridine and metallic Ti, Zr-doped graphene surfaces, while there is no chemical bond formation with non-metallic N-doped graphene and intrinsic graphene. Chemical adsorption interaction of pyridine with Ti, Zr-doped graphene, physical adsorption interaction with N-doped graphene and intrinsic graphene. Pyridine was more stable adsorption on the surface of Ti Zr-doped graphene.

Density functional theory study of adsorption of As₂O₃ on CeO₂ surface by Fe, La doping and oxygen defects

LU Kunpeng, ZHANG Kaihua, ZHANG Kai

, Available online , doi: 10.19906/j.cnki.JFCT.2024005

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Density functional theory (DFT) was used to study the adsorption behavior of As₂O₃ (g) on iron and lanthanum doped CeO₂ (110) and oxygen-deficient LaCeO (110) surfaces, and the reasons for the arsenic adsorption capacity of LaCeO surface was significantly higher than that of FeCeO surface was explored. The results show that the adsorption effect of As₂O₃ (g) is closely related to the number of adsorption sites, adsorption energy, bond length and charge transfer amount. Ce and O atoms on the surface of pure CeO₂ are both active sites, and the adsorption is mainly chemisorption, the absolute adsorption energy is greater than −4.22 eV, and the charge transfer amount is −0.19− −0.31 e. As₂O₃ has a negative charge and acts as a surface accepter, while CeO₂ loses electrons and has a positive charge on the surface, which acts as a surface donor. The number of free electrons in the CeO₂ conduction band gradually decreases, the conductivity decreases, and it is difficult to provide more electrons continuously, so the adsorption amount is small. Two adsorption sites are added on the surface of FeCeO (110): Fe top site and Bridge-2 Bridge site, where Fe top site is chemical adsorption and Bridge-2 Bridge site is physical adsorption. The gap doping of Fe changes the electron distribution and lattice structure on the surface of FeCeO, resulting in obvious deformation of the lattice and reducing the difficulty of bonding, thus increasing the configurational adsorption energy of some configurations. However, it does not change the charge transfer direction between As₂O₃ and FeCeO, thus not changing the surface adsorption form of As₂O₃. As₂O₃ is still adsorbed in the form of negative ions, which plays the role of surface acceptor, and the adsorption amount is small. LaCeO (110) has three new adsorption sites: La top site, Bridge-3 Bridge site and Hollow-2 vacancy, among which the La top site and Bridge-3 Bridge site are chemical adsorption. La doping changes the charge transfer direction between As₂O₃ and LaCeO, resulting in positive ion adsorption of As₂O₃ with electron loss and surface donor function. The electrons on the surface of LaCeO play the role of surface acceptor. With the progress of adsorption, the number of free electrons in the conduction band increases, and the conductivity increases. Therefore, the adsorption capacity of As₂O₃ on the surface of LaCeO increases. In the absence of O₂, the number of chemical bonds and bond energy formed on the surface of LaCeO (110) with single O defect are smaller than those on the surface of LaCeO, and the charge transfer on the surface of the defect is less, so the adsorption energy decreases. In this case, As₂O₃ obtains electrons and acts as the surface donor, and the adsorption capacity is lower than that on the complete LaCeO surface. In the presence of O₂, the adsorption energy and charge transfer number increase in the ortho-configuration after O₂ supplementation with O defect. As₂O₃ is positively adsorbed in ionic form, and the adsorption energy is also higher than that on the intact LaCeO surface. The adsorption capacity of As₂O₃ is better than that on the LaCeO surface, indicating that O defect is conducive to the adsorption of As₂O₃ in the presence of O₂.

Research progress of chemical catalysis for biomass-based furfural to nitrogen-containing compounds

CHEN Jiayue, LI Keming, HUANG Yaobing, LU Qiang

, Available online , doi: 10.19906/j.cnki.JFCT.2024007

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The utilization of biomass holds a great promise to partially replace the non-renewable fossil resources for the production of chemicals and materials for daily use, which could effectively mitigate the challenges associated with global resource scarcity. Furfural, a prominent biomass-derived platform compound derived from the dehydration of xylose in hemicellulose, which is widely used as the key intermediate or solvent in the petrochemicals, coating, pesticides, medicine, synthetic rubber, etc. At the same time, furfural can be converted into a series of high value-added chemicals and fuel, such as alcohols, acids, esters, nitriles, amines, and others due to its active C=O bonds and furan rings. Typical chemical reactions, such as reduction, oxidation, etherification, ammonia oxidation, reduction amination, ring rearrangements and others, are frequently used for the above conversions. Among various chemicals obtained from furfural conversions, nitrogen-containing compounds have attracted considerable attention, owing to the wide applications of such type molecules in the synthesis of drug molecules, bioplastics, and other functional materials. Therefore, using furfural as a raw material to synthesize bio-based nitrogenous compounds represents a cutting-edge research direction. In the presence of nitrogen sources, furfural can be transformed into diverse nitrogen-containing compounds through different reactions, such as reduction amination, ammonia oxidation, oxidative coupling, etc. Varied nitrogen sources (e.g. NH₃, N₂H₄·H₂O, NH₄HCO₂, CH₃COONH₄, (NH₄)₂CO₃ and others), catalysts, reaction atmospheres, and temperatures can result in distinct target products during furfural conversions. Currently, domestic and foreign research groups have made significant progress on furfural conversions to different nitrogen-containing compounds. Therefore, this review aims to briefly outline the recent achievements in the synthesis of high-value nitrogen-containing compounds from furfural through catalytic conversions over different catalysts. The main content includes: (1) synthesizing amines by reduction aminations, e.g. primary, secondary, and tertiary amines; (2) nitriles production by ammonia oxidation; (3) producing amides by amidation; (4) preparing heterocyclic compounds, such as benzoheterocyclic, thiazole, pyrrole, indole, piperidine and pyridine via oxidative cyclization, decarbonylation-amination, reduction amination, hydrogenation, ring rearrangements. The influences of synthesis methods, catalyst types, reaction pathways, mechanisms, as well as the nitrogen sources, on product distributions were discussed in detail. Considering the pathways and products potentially affected by different nitrogen sources and reaction conditions, future breakthroughs in the synthesis of nitrogen-containing compounds from furfural can be anticipated from the following aspects: (1) By systematically considering the reaction processes and mechanisms, the construction of composite catalysts and precise adjustment of reaction conditions to integrate multiple reaction steps into one is a trend in this research area to attain more efficient and green conversion processes; (2) Combined experimental with theoretical investigations to comprehensively reveal the reaction pathways during the reaction of different nitrogen sources with furfural; (3) Exploration of new chemical conversion routes and catalysts for the production of more novel nitrogen-containing compounds, to further broaden the application areas of furfural based chemicals. In brief, this review provides a systematical review on the production of furfural based nitrogen-containing chemicals, which would benefit the communities working in biomass utilization areas, and also contribute to the establishment of knowledge of the furfural chemical family.

Experimental study on alkali lignin enhanced chemical looping gasification of pulverized coal char

GAO Xinglong, AN Fengxia, HU Yun, CHEN Guoqing, YI Qun, WU Xiaoyan, CAO Jinzeng, YAO Weishan, WEI Guoqiang

, Available online , doi: 10.19906/j.cnki.JFCT.2023078

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The pulverized coal char from the byproduct of China's coal coking industry has high yield and low activity, which is difficult to be directly recycled. The conventional thermochemical utilization method has harsh reaction conditions, catalyst deactivation and kinetic limitations. By using the alkali lignin from paper-making as a disposable catalyst, an alkali lignin enhanced chemical looping gasification method was constructed to treat coal coke powder, which can realize the collaborative resource utilization of industrial by-products. In this study, the reaction process of alkali lignin and coal char powder was studied by thermogravimetry and kinetic analysis. The thermal transformation experiment and kinetic analysis showed that alkali lignin could strengthen the chemical looping gasification process of pulverized coal char and promote the pyrolysis peak to move to low temperature. When the mass ratio of pulverized coal char to alkali lignin was 1∶3, the activation energy was 87.56% lower than that of coal coke powder alone, indicating that there was a synergistic effect between the two in the co pyrolysis process. The experiments in fixed bed reactor verified that the carbon conversion rate and the selectivity of syngas increased as the increasing of temperature and the content of alkali lignin and oxygen carrier, which effectively promoted the gasification reaction. However, excessive oxygen loading led to combustion reaction between syngas and lattice oxygen and reduce syngas selectivity. Under the optimal reaction conditions of 950 ℃, the mass ratio of coal char powder to alkali lignin is 1∶2, and the mass ratio of oxygen carrier to pulverized coal char/alkali lignin is 1∶1, the selectivity of syngas of alkali lignin/coal char powder in chemical looping gasification was 82.85%. This study provides a scientific basis for the resource utilization of alkali lignin and coal char powder.

Research on the 9,10-dihyroanthrancene assisted catalytic pyrolysis of pine over nitrogen-doped activated carbon for preparation of alkoxyphenols

LI Wentao, ZHANG Chengbo, LI Kai, NIU Qi, LI Jihong, LU Qiang, JIA Bao, GAO Lijuan

, Available online , doi: 10.19906/j.cnki.JFCT.2023081

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In this study, nitrogen-doped activated carbon (NAC) was prepared from walnut shell and applied to the catalytic pyrolysis of pine for selective preparation of alkoxyphenols with 9,10-dihyroanthrancene (DHA) as the hydrogen donor. The effects of ammonia concentration on the physicochemical properties of NAC were investigated. The regulatory functions of DHA/pine ratio, pyrolysis temperature, and NAC/pine ratio on the generation of alkoxyphenols were revealed. The results showed that the pore structure and active sites distribution of NAC could be improved by proper ammonia concentration. The NAC prepared at ammonia concentration of 15% was the best for the production of alkoxylphenols. The yield of alkoxylphenols reached its maximum value of 5.27% at DHA/pine ratio of 3, pyrolysis temperature of 550 ℃, and NAC/pine mass ratio of 3, which was much higher than that from catalytic pyrolysis of pure pine (1.74%).

The effect of alkali and alkaline earth metals in biomass ash on the bio-oil components derived from biomass fast pyrolysis

DING Zixia, CAI Bo, CEN Kehui, CHEN Dengyu, MA Zhongqing

, Available online , doi: 10.19906/j.cnki.JFCT.2023076

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The alkali and alkaline earth metals (AAEMs) in biomass ash have a significant impact on the yield and component distribution of rapid plytic biooil. In this paper, corn straw is selected as the raw material. First, the effect of cascade deash removal pretreatment (distillation water, ammonium acetate and hydrochloric acid) on the selective removal of AAEMs and its biological oil components is studied, and then the effect of the type of AAEMs (K, Ca, Na and Mg), the concentration of chloride salt (0.5%, 2.5% and 5%), and the acid radical in metal salt（${\rm{SO}}_4^{2-} $, ${\rm{NO}}_3^- $, ${\rm{CO}}_3^{2-} $, ${\rm{HCO}}_3^- $, AC⁻ and ${\rm{PO}}_4^{3-} $）on the compound distribution of bio-oil was systematically investigated. The results show that in the process of ash removal pretreatment, with the deepening of the acidity of the ash removal solution, the removal rate of AAEMs gradually increases. According to the selective removal law of AAEMs in the process of cascade ash removal, their morphology in biomass can be divided into the following three groups, namely the water-soluble metal (K), the ion-exchanged metals (Ca and Mg), the acid-soluble metal (Na). The removal of AAEMs promoted the formation of levoglucosan (LG), while restrained the formation of ketones and furans. However, the incorporation of AAEMs in biomass presented an opposite variation trend. The AAEMs would act as catalyst during biomass pyrolysis which promoted the secondary cracking of LG, leading to the reduction of LG and increase of ketones and furans. In addition, different acid roots in potassium salt also have remarkable influence on the secondary cracking reaction of LG and the rupture of the aryl ether bond and the phenolic hydroxyl group in lignin. The influence of the acid roots on the secondary cracking reaction of LG was in the order of ${\rm{HCO}}_3^- $>${\rm{CO}}_3^{2-} $>AC⁻>${\rm{PO}}_4^{3-} $>Cl⁻>${\rm{NO}}_3^- $>${\rm{SO}}_4^{2-} $, while the influence of acid roots on the rupture of the aryl ether bond and the phenolic hydroxyl group was in the order of ${\rm{CO}}_3^{2-} $>Cl⁻>${\rm{HCO}}_3^- $>${\rm{PO}}_4^{3-} $≈AC⁻>${\rm{SO}}_4^{2-} $≈${\rm{NO}}_3^- $.

Catalytic pyrolysis of waste biomass to produce hydrogen-rich gas:Influence of catalyst performance

LI Xueqin, LIU Peng, LU Yan, WANG Zhiwei, WU Youqing, LEI Tingzhou

, Available online , doi: 10.19906/j.cnki.JFCT.2024011

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Abstract:
Catalytic pyrolysis of waste biomass is a promising method for the production of hydrogen-rich gas. HZSM-5 carrier is the premise of ensuring the thermal stability and long life of catalytic materials, and plays a mechanical role in bearing the active component nickel（Ni）. At the same time, aluminum ash, as an important waste in the production process of aluminum industry, is mainly composed of Al₂O₃ and a large number of heavy metal oxides such as Na₂O, CaO, MgO, Fe₂O₃ and so on. In this study, aiming at the technical bottleneck problems such as the low performance of traditional HZSM-5 molecular sieve and the difficulty of resource utilization of aluminum ash, the active component nickel (Ni) and promoter iron (Fe) were combined with HZSM-5 molecular sieve by ultrasonic-assisted excessive impregnation to improve the yield of hydrogen-rich gas. Furthermore, waste aluminum ash (ASA) and HZSM-5 molecular sieve were used as co-carriers to prepare aluminum ash co-supported Ni-Fe catalyst with HZSM-5 molecular sieve, and it was used to enhance the process of hydrogen-rich gas production by the catalytic pyrolysis of biomass. The results showed that the heat transfer efficiency decreased with the increase of heating rate during pyrolysis of biomass. After compensation, the apparent kinetic parameters (E and A) of pyrolysis of different biomass were obtained. At the pyrolysis temperature of 700 ℃, Ni-Fe/HZSM-5 catalyst increases the yield of hydrogen-rich gas to 56.49% (about 230.59 mL/g), hydrogen yield to 63.12%, hydrogen production efficiency to 0.71%, and CO yield to 65.77 mL/g. Sufficient amount of Ni-Fe/HZSM-5 catalyst enhanced the pathway of hydrogen production by the catalytic pyrolysis of biomass, promoted the gasification reaction of carbon deposition, and played a dual role in increasing the yield of H₂ and CO. The synergism between HZSM-5 and ASA carriers enhanced the reforming process of CH₄ and CO₂, inhibited the reverse water vapor shift reaction, obtained 53.37% and 41.56% gas and tar yields. At the same time, the gasification reaction of carbon deposition was also accelerated, reduced the char yield to 5.07%, and obtained the carbon deposition of 0.05 g/g. Ni-Fe/ASA@HZSM-5 has good thermal cracking ability and deoxidization ability, which is helpful to promote the formation of hydrogen-rich gas on HZSM-5 as a base catalyst. From the point of view of proximate analysis and chemical composition of biomass, the composition of different kinds of biomass varies greatly, and the product distribution of catalytic pyrolysis also has a great influence. The order of gas yield of pyrolysis of biomass catalyzed by Ni-Fe/HZSM-5 was PR (74.21%)>WSt (54.71%)>CR (53.5%)>MCh (52.47%)>WSh (52.10%)>CS (46.49%)., which provides theoretical support for the development of deep purification and efficient utilization of high temperature pyrolysis gas, and effectively guides the development of a new double catalytic bed for multi-stage catalytic reforming.

Study on pyrolysis mechanism and kinetics of two of spiro [4,5] decane and spiro [5,6] dodecane

WANG Hongyan, SUN Xinyue, ZHOU Yurou, LIU Guozhu, WANG Yutong, CAO Jingpei

, Available online , doi: 10.19906/j.cnki.JFCT.2024001

Abstract(48) HTML (30) PDF 2109KB(14)

Abstract:
Active cooling with high-energy-density liquid hydrocarbon fuel is one of promising techniques for the thermal protection of hypersonic aircrafts. To extend the flight range and increase the payload of volume-limited aerospace vehicles, high-energy-density liquid hydrocarbon fuel is directly used as an energetic additive or liquid propellant. Among them, biomass derived spiro-fuels, shown high density, low freezing point and high net heat of combustion due to compact molecular structures, are a kind of significant high-density fuel. The investigation of thermal pyrolysis of these spiro-fuels not only significantly improves the heat sink through the endothermic reaction, but also brings the new challenges of ignition and combustion of the cracked hydrocarbon fuel. The detailed theoretical calculations and molecular dynamics simulations of spiro [4,5] decane (C₁₀H₁₈) and spiro [5,6] dodecane (C₁₂H₂₂) initial pyrolysis were performed to explore the ring-size effect on the consumption of fuels and formation of primary products. The results show that the initial decomposition paths of the two spiro-fuels are very similar, mainly consumed by the open-ring isomerization via the unimolecular C−C dissociations of the six membered ring structure and H-abstractions by small radicals attacking the fuel parents. Due to the lower C−C and C−H bond dissociation energies caused by large tension of the seven membered ring structure, C₁₂H₂₂ may exhibit the lower initial decomposition temperature and higher reaction activity than C₁₀H₁₈. The differences of simultaneously formed fuel radicals during C₁₀H₁₈ and C₁₂H₂₂ initial pyrolysis further affect the formation pathways of C1−C7 small products, cycloalkenes and monocyclic aromatics. Among them, ethylene are the most important products. Due to the presence of inherent six membered rings in two spiro-fuels, monocyclic aromatics mainly originate from multi-step dehydrogenation reactions of fuel radicals, involving benzene, toluene, styrene and ethylbenzene. Notably, the size effect of spiro-ring in two fuels leads the obvious structural differences of the formation of chain hydrocarbons and cycloalkenes. For C₁₀H₁₈, a large number of penta- cycloalkenes may be generated, including cyclopentadiene, cyclopentene, fulvene, methylcyclopentadiene and methylcyclopentene, whereas the seven-membered ring structure of C₁₂H₂₂ may produce corresponding seven-membered products (cyclohexene and methylene cycloheptane). Moreover, the pyrolysis behaviors of these two spiro-fuels at 2000 K based on the ReaxFF molecular dynamics simulation were explored and show well consistent with the main products derived from DFT theoretical calculations. This work performs the DFT theoretical calculations and ReaxFF molecular dynamics simulation on the pyrolysis kinetic mechanisms of two representative high-density biomass fuels of spiro fuels, providing a possible initial pyrolysis path and laying a theoretical foundation for their practical application in engines. However, the complex working environment of the cooling channel poses more challenges to the actual pyrolysis process of the new high-density hydrocarbon fuels. In future research, pyrolysis experiments will be conducted under high temperature and high pressure conditions, and the detailed pyrolysis kinetics models with excellent predictive performance over a wide operating range will be constructed. At the same time, research will be conducted on the subsequent ignition and combustion process of the engine combustion chamber, exploring the impact mechanism of catalysts and fuel additives on this process, assisting in the practical application of fuel, improving fuel combustion efficiency, and effectively controlling pollutant emissions.

Study on the effects of Rh loading on the selectivity to methanol and ethanol in CO₂ hydrogenation reaction over Rh/CeO₂ catalyst

ZHENG Ke, LIU Bing, XU Yuebing, LIU Xiaohao

, Available online , doi: 10.1016/S1872-5813(24)60450-0

Abstract(9) HTML (5) PDF 1365KB(2)

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The capture and hydrogenation of carbon dioxide (CO₂) into high-value chemicals such as alcohols is one of the important ways to reduce CO₂ emissions and achieve the circular economy. This study investigated the catalytic performance of Rh/CeO₂ catalysts with different Rh loadings in the range of 0.1−2.0% in the CO₂ hydrogenation reaction. Various characterizations including XRD, Raman, H₂-TPR, CO₂-TPD, CO-DRIFTS, and XPS were employed to reveal the influence of Rh loading on the catalytic activity and product selectivity. The results showed that ethanol was the major product for CO₂ hydrogenation reaction at 250 ℃ and 3.0 MPa over 0.1% Rh/CeO₂ catalyst. With the increase of Rh loading, CO₂ conversion increased along with the decline in ethanol selectivity. When Rh loading reached 2.0%, the main product shifted to methanol. The difference in product selectivity over Rh/CeO₂ catalysts with changed Rh loadings is related to the different structure and electronic properties of Rh. Atomically dispersed Rh⁺ species favor the stabilization of CO* and its subsequent C-C coupling with CH₃* to form ethanol, while metallic Rh clusters facilitate the hydrogenation of CO* to form methanol.

Study on catalytic conversion of biomass pyrolysis volatiles over composite catalysts of activated carbon and HY zeolite

XU Ji, WU Bowen, HAN Zhen, HU Haoquan, JIN Lijun

, Available online , doi: 10.1016/S1872-5813(24)60447-0

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Biomass pyrolysis tar has complex compositions and high oxygen content, which restricts its high-value utilization. In this paper, commercial activated carbon (AC) and HY zeolite were used as composite catalysts to study the effect on the pyrolysis volatiles from rice straw and poplar sawdust by changing the mixing models of two catalysts. The results showed that the loading models of AC and HY zeolite obviously affected the products distribution from biomass pyrolysis and tar components. The lowest yield of bio-oil was obtained when HY zeolite and AC were mechanically mixed at a mass ratio of 1/1 (YACM). The layered model with upper AC and lower HY zeolite (ACTYL) and YACM are beneficial to the deoxidation and aromatic hydrocarbon generation of bio-oil. Under YACM, the aromatics content in rice straw and poplar sawdust pyrolytic tar can be increased from 13.8% and 8.0% without catalyst to 56.4% and 53.1%, respectively. However, the layered loading with upper HY zeolite and lower AC (YTACL) is favorable for the formation of phenolic compounds. The selectivity to monocyclic aromatic hydrocarbons follows the order of YTACL> ACTYL>YACM, and the selectivity to bicyclic aromatic hydrocarbons is in the order of YACM> ACTYL>YTACL. AC catalyst possesses smaller pore size and fewer acidity compared with HY zeolite. The active sites of AC are conducive to the rearrangement of furan compounds to generate cyclopentanone, 2-cyclopentenone and methyl-cyclopentenone, and further rearrangement to form phenol. Therefore, the loading model of YTACL exhibits a promotion effect on the formation of phenol, cresol, toluene, ethylbenzene and p-xylene. The strong acidic sites of HY zeolite are favorable for the aromatization, so the loading model of ACTYL has good selectivity to the formation of naphthalene, methylnaphthalene, anthracene and pyrene. This work will provide a guide for the products regulation from biomass pyrolysis and enriching the aromatics and phenols in bio-oil.

Preparation of Ultra-microporous Waste Paper Carbon Aerogel and its CO₂ Adsorption Performance

Gu Jinyang, Zhang Xiong, Zhang Junjie, Shao Jingai, Zhang Shihong, Yang Haiping, Chen Hanping

, Available online , doi: 10.19906/j.cnki.JFCT.2024016

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The intensification of climate change requires the development of greener and more efficient carbon abatement technologies and products. Conventional CO₂ carbonaceous adsorbent materials derived from solid waste and biomass feedstocks are poorly adsorbed and often require additional activation pore making and functional group introduction to enhance the adsorption performance of the porous carbon, which inevitably results in further growth of the process and further increase in energy consumption. In the work carried out in this paper, different kinds of waste paper were used as raw materials, and after a simple pretreatment and sol-gel carbonization process, highly developed microporous hierarchical porous carbon aerogels were prepared; moreover, KOH could be introduced in situ and activation pore-making could be accomplished synchronously during pyrolysis, which avoided the additional energy consumption of the two-step method. Thermogravimetric (TG), scanning electron microscopy (SEM), specific surface area and pore size analyzer (BET), Fourier transform infrared spectrometer (FT-IR) and fixed bed adsorption rig were used to characterize and test the thermal weight loss properties of the waste paper aerogels, the physicochemical properties of the waste paper carbon aerogels and the CO₂ adsorption properties, respectively, and the results show that the main thermal weight loss process of the waste paper aerogels occurs at around 300 ℃. and is accompanied by the appearance of miscellaneous peaks of heat loss in the low pyrolysis temperature region, and the final mass residual rate is slightly higher than that of cellulose. Scanning electron microscopy showed that the pore structure was well developed and relatively homogeneous, and the surface openings showed a honeycomb-like structure. The printing paper carbon aerogel DYZ-800 prepared at a pyrolysis temperature of 800 ℃ has an ultra-high specific surface area of 1369.94 m²/g (94.28% of microporous specific surface area), a pore volume of 0.59 cm³/g (85.34% of microporous pore volume), and a pore-size distribution that is close to the kinetic diameter of CO₂ molecules (0.4-0.8 nm and containing a large number of super-micropores with a size of 0.7 nm). The results of FT-IR tests revealed the effects of different waste paper types and pyrolysis temperatures on the carbon aerogel skeleton and chemical groups of waste paper, with sample DYZ-800 having a more stable carbon skeleton and a relatively high content of carbon-oxygen (C-O) groups. The maximum CO₂ adsorption capacity of DYZ-800 without modification was 247 mg/g at 0 ℃ (1 bar) and 151 mg/g at 25 ℃ (1 bar), and the CO₂/N₂ adsorption selectivity was 11. The average fluctuation after 7 adsorption and desorption cycles was less than 5%, which showed good regeneration stability. The capture of CO₂ at 10% flue gas concentration on a fixed-bed adsorption bench could also reach 42 mg/g (25 ℃, 1 bar). Among the three different adsorption kinetic models selected, the Bangham pore diffusion model had an excellent fit, demonstrating the great contribution of the well-developed pore structure of waste paper carbon aerogels in the CO₂ kinetic adsorption process. Taken together, these results show that the waste paper carbon aerogel possesses excellent physicochemical properties, and the presence of a large number of micropores (especially ultra-micropores) enables it to exhibit excellent CO₂ adsorption performance, which is superior to that of conventional solid waste and biomass-based carbon materials. All these indicate that the carbon aerogel prepared in this work has great advantages in carbon capture and potentials for further improvement, and this work also provides new ideas for solid waste disposal and resource utilization.

Dehydration of Sugar Mixtures to 5-Hydroxymethylfurfural Catalyzed by Modified Tin-Mordenite

ZHANG Ruonan, LI Gang, MA Zhongmin, LÜ Qiang

, Available online , doi: 10.19906/j.cnki.JFCT.2024018

Abstract(8) HTML (5) PDF 1084KB(0)

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5-hydroxymethylfurfural (HMF) is a versatile compound that has great market potential in the future chemical industry. HMF production from fructose has a problem of higher cost, while HMF production from glucose has a problem of lower yield. Therefore, the use of relatively inexpensive biomass-derived syrup to produce HMF in order to achieve industrial production is currently a research hotspot. A series of Sn-MOR catalysts were prepared by using mordenite zeolite (H-MOR) as a carrier, which was modified with acid treatment and adding tin to remove Al and replenish Sn. The Sn-MOR catalysts were characterized by X-ray diffraction (XRD), diffuse reflectance ultraviolet-visible spectra (UV-Vis), ammonia temperature programmed desorption (NH₃-TPD), and X-ray fluorescence spectroscopy (XRF). The characterization results showed that the Sn-MOR still maintained the crystal structure of mordenite, with changes in strength and content of acid centers , and Sn was inserted into the zeolite skeleton. Glucose and fructose were used as substrates in the catalytic reaction of unmodified H-MOR and modified Sn-MOR, and the experimental results showed that H-MOR catalyzed the dehydration reaction of glucose poorly, with a HMF yield of only 7.08%, but its catalytic performance in dehydration of fructose was better, with a HMF yield of 76.78%. The modified Sn-MOR possessed isomerization activity, which improved the reactivity of glucose dehydration with a HMF yield of 38.65%, while the modified Sn-MOR still maintained the high catalytic activity of MOR for fructose dehydration to HMF. Using sugar mixtures (m _{hydrated glucose}: m _fructose = 1:1) as the substrate, the reaction performance of the catalysts with different tin metal additions to H-MOR was firstly investigated, and the results showed that 3.76-Sn-MOR with 3.76 w% tin addition catalyzed the dehydration of the sugar mixtures better. The reaction performance of the catalyst prepared by adding tin after H-MOR acid treatment was further investigated, and the results showed that the 3.76-Sn-MOR_1MHCl prepared by acid treating H-MOR using 1mol/L hydrochloric and adding tin could obtain better HMF yield (49.37%) and selectivity (58.09%) in dehydration of sugar mixtures. The reaction conditions were further optimized through orthogonal experiments using a 3.76-Sn-MOR_1MHCl catalyst in terms of sugar concentration, reaction temperature, catalyst dosage, and reaction time. The results showed that neither too high nor too low sugar concentration was conducive to HMF formation, and increasing temperature and catalyst dosage were conducive to HMF formation, but increasing temperature reduced the selectivity of HMF. Prolongating reaction time had little effect on improving the yield of HMF, but decreased the selectivity of HMF. The optimal reaction conditions were as follows: 1.5 g of sugar mixtures, reaction temperature of 170 ℃, catalyst dosage of 0.3 g, and reaction time of 3 h. Under the above optimal reaction conditions, the superior catalyst 3.76-Sn-MOR_1MHCl was finally applied to F55 fructose syrup, which has a dry matter ratio of glucose and fructose similar to that of sugar mixtures, and the HMF yield was 63.76%, the HMF selectivity was 69.43%, and the fructose syrup conversion was 91.82%. The catalyst was recycled five times and the HMF yield reduced to 49.50%, which still maintained a certain catalytic activity.

Direct liquefaction behavior of Shenhua coal under CO containing atmosphere

TANG Bowen, ZHANG Rui, LIU Haiyun, JIN Lijun, HU Haoquan

, Available online , doi: 10.1016/S1872-5813(24)60451-2

Abstract(7) HTML (6) PDF 2299KB(0)

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Direct coal liquefaction (DCL) under CO or syngas atmosphere is beneficial to reduce the cost of hydrogen production. In this paper, the effects of CO on the liquefaction process of Shangwan coal were investigated by comparing the liquefaction behavior in three atmospheres of CO, H_2, and N₂. Then, the effects of different CO/H₂ ratios and catalysts on the liquefaction process in syngas were investigated. The results indicated that the oil yield under the CO atmosphere reached 43.1%, which was 4.2% lower than that under H₂, but 10.2% higher than that under N₂. The liquefaction performance was further improved by adding the Shenhua 863 catalyst. It is analyzed that CO promoted liquefaction in two ways: water-gas shift reaction and the reaction between CO and organic structures of coal. Through the characterization of the products by GC-MS and FI-TR, it was found that CO makes the benzenes, aliphatics, and oxygen-containing compounds in liquefied oil simultaneously increased, the effect on functional groups and free radicals concentration in the solid products was not obvious. The experimental results under syngas showed that the highest oil yield, 57.4%, can be obtained in DCL with 20%CO syngas, and further improved by increasing the moisture content of coal appropriately. In addition, it was found that the Shenhua 863 catalyst has a good catalytic effect on the liquefaction process and also water-gas shift reaction. The research work provides a theoretical basis for the direct liquefaction of coal under syngas.

Study on the catalytic performance of fe in situ modified small crystallite silicalite-1 zeolite in chichibabin condensation reaction

TAO Jinquan, JIA Yijing, BAI Tianyu, HUANG Wenbin, CUI Yan, ZHOU Yasong, WEI Qiang

, Available online , doi: 10.1016/S1872-5813(24)60443-3

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Pyridine and its derivatives, collectively referred to as pyridine bases, find extensive applications in fields such as pesticides and pharmaceuticals, serving as crucial intermediates in the chemical industry. In recent years, with the development of the pesticide and pharmaceutical industries, the demand for pyridine bases has rapidly increased. The Chichibabin condensation reaction is the most widely used route for industrial production of pyridine bases. Currently, the most commonly used ZSM-5 zeolite catalyst is limited by the instability of its silicon-aluminum framework structure, resulting in a short active reaction cycle (5 hours). In response to this issue, this study selected the thermally stable and hydrothermally stable Silicalite-1 zeolite. Polyvinylpyrrolidone (PVP) was employed as a colloidal dispersant using a hydrothermal synthesis method. In situ modification was utilized to introduce Fe into the MFI framework during zeolite synthesis. The influence of PVP dosage, template agent dosage, and other crystallization conditions on the crystallinity, pore structure, and acidity of Silicalite-1 zeolite products was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TG), and BET surface area analysis. The acidity of Fe-modified Silicalite-1 zeolites was characterized using NH₃-temperature programmed desorption (NH₃-TPD), pyridine infrared (Py-FTIR) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). Experimental results indicated that the addition of seed crystals effectively reduced the particle size of the molecular sieve to approximately 200 nm. Fe-modified Silicalite-1 exhibited a disk-like morphology with good crystal dispersion. The highest relative crystallinity of the product reached 103% with a seed crystal input of 15% and PVP addition of 3.75%. Fe-modified Silicalite-1 possessed a greater abundance of both Lewis (L) and Brønsted (B) acid sites. The modified Silicalite-1 exhibits a higher abundance of B and L acid sites, resulting in an increase in the initial activity for the pyridine bases synthesis with Chichibabin condensation from 66% to 85%. Compared to ZSM-5, Fe-modified Silicalite-1 exhibited superior catalytic stability, maintaining the conversion rates and yields of pyridine bases above 66% and 40%, respectively, over a 15 hour reaction period. Finally, the strategy proposed in this study, which utilizes polyvinylpyrrolidone as a colloidal stabilizer to modify Silicalite-1 zeolite, significantly broadened the application prospects of weakly acidic pure silica zeolites in the field of acid catalysis. This approach has demonstrated significant scientific value and industrial potential.

Effect of ZSM-5@Silicalite-1 zeolites prepared by solid phase epitaxial growth method on CO₂ hydrogenation and toluene alkylation reactions

JIA Yimin, NIU Pengyu, JIA Litao, LIN Minggui, GUO Heqin, XIAO Yong, HOU Bo, LI Debao

, Available online , doi: 10.19906/j.cnki.JFCT.2024012

Abstract(22) HTML (12) PDF 6765KB(3)

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CO₂ hydrogenation to synthesize high value-added aromatics is of great significance to alleviate the energy climate problem caused by CO₂ emission. It is generally believed that the reaction course of CO₂ hydrogenation of toluene coupled with alkylation to produce xylenes is as follows: firstly, CO₂ reacts with H₂ to produce methanol intermediates, and then the methanol intermediates react with toluene on zeolite catalysts to produce para-xylene (PX) by alkylation. According to the reaction pathway, it is necessary to construct a bifunctional catalyst with synergistic matching of the two process conditions to simultaneously realize the hydrogenation of CO₂ to methanol intermediate and the alkylation of the intermediate and toluene to generate para-xylene. The ZnZrO_x/ZSM-5 catalytic system, in which the ZnZrO_x has strong thermal stability and CO₂ activation ability, and the ZSM-5 has a good morphology selectivity for PX, is considered to be a promising CO₂ hydrogenated toluene coupled alkylation catalyst. However, this system still suffers from low PX selectivity, mainly due to the presence of non-selective acidic sites on the outer surface of the zeolite or near the pore orifice, which leads to the generation of side reactions, such as deep methylation and toluene isomerization, and reduces the selectivity. In this paper, ZSM-5@Silicalite-1 zeolites were prepared by epitaxial growth of Silicalite-1 on the surface of ZSM-5 using solid-phase synthesis. At the same time, the highly active oxide ZnZrO_x was prepared and physically mixed with ZSM-5@Silicalite-1 to form a ZnZrO_x/ ZSM-5@Silicalite-1 bifunctional catalyst to study the catalytic performance of CO₂ hydrogenation coupled with toluene alkylation. Compared with the ZnZrO_x/ZSM-5 catalyst, the modified zeolite improved the para-xylene (PX) selectivity. The effect of crystallization conditions (silicon source, crystallization process, and number of crystallizations) on the epitaxial growth of Silicalite-1 from ZSM-5 was investigated, as well as the effect of the thickness of the Silicalite-1 passivation layer on the performance of the reaction between carbon dioxide hydrogenation and toluene alkylation. The ZZO/1:3.5Z5-Na-SiO₂ catalyst showed a toluene conversion of 12.0%, a xylene selectivity of 77.4%, and a PX selectivity of 73.4% in xylene under 400 ℃ and 3 MPa reaction conditions. The structure and acid properties of the zeolites were investigated in detail by SEM, XRD, N₂ adsorption-desorption, XPS, NH₃-TPD and Py-FTIR characterization, and the results show that the selectivity of para-xylene (PX) can be effectively improved by solid-phase epitaxial growth to extend the pore channels of ZSM-5, increase the diffusion resistance of m-xylene (MX) and o-xylene (OX), and passivate the acidity of the outer surface at the same time. This method abandons the disadvantage of previous modification of molecular sieves by blocking the pores to narrow the orifice, and upgrades the product selectivity while ensuring the catalyst activity.

Study on gas phase reaction mechanism of HCN and H₂/H₂O based on density functional theory

SUN Mingzhe, XU Jianliang, HOU Qiushi, DAI Zhenghua, WANG Fuchen

, Available online , doi: 10.19906/j.cnki.JFCT.2024004

Abstract(36) HTML (9) PDF 9238KB(7)

Abstract:
HCN is a highly toxic substance that can enter the human body through the skin and respiratory system, and in severe cases, cause death. HCN can achieve partial conversion under high-temperature gasification conditions, mainly by reacting with H₂ and H₂O. In order to further explore the micro reaction mechanism of HCN with H₂ and H₂O during gasification, and to investigate the effects of temperature and pressure changes on the reaction, this paper uses quantum chemical simulation methods to study the reaction path, reaction thermodynamics, and kinetics of the above reactions, and quantitatively analyzes the changes in thermodynamic parameters and reaction rate constants with temperature, fitting the Arrhenius equation related to the reaction. Calculate the distribution of Fukui functions for various reactants and intermediates in the reaction process of HCN with H₂ and H₂O using Multiwfn, and speculate on possible reaction pathways. The transition state search and single point energy calculation of the reaction process between HCN and H₂ and H₂O were carried out using Gaussian & Gaussian View. Similarly, using the wave function program Multiwfn to calculate the Mayer bond order. The analysis of the bond order curve during the reaction process can reveal the changes in the strength of chemical bonds and the situation of bond formation and breaking. Use the Shermo program to calculate the thermodynamic parameters of each stagnation point at different temperatures, including enthalpy, entropy, Gibbs free energy, and partition function. Finally, the KiSThelP program was used to calculate the reaction rate constants for each step of the reaction based on classical transition state theory at different temperatures. The results show that the relatively optimal path for the reaction between HCN and H₂ is as follows: three H₂ molecules are added in three steps on C≡N to obtain the product CH₄+NH₃; The relatively optimal path for the reaction between HCN and H₂O is as follows: H₂O molecules attack C atoms, and the H of O and C atoms are transferred to N atoms to obtain the product CO+NH₃. The first step of reaction between HCN and H₂ is R1→IM1 which is below 534 K with ΔG<0. After exceeding this temperature, ΔG>0 becomes a reverse spontaneous reaction. It can be considered that an increase in temperature is not conducive to the electrophilic addition reaction of the first H₂ on C≡N. The second step is IM1→IM2, with ΔG below 1103 K less than 0 and above greater than 0, indicates that the spontaneity of the second step H₂ addition reaction is inhibited as the temperature gradually increases. The third step is IM2→P1. Within the set temperature range, its ΔG is always less than 0, and the reaction can always proceed spontaneously. The ΔG of the first step reaction R2→IM5 in Path 3 is only less than 0 at room temperature, indicating that this step is difficult to occur spontaneously at high temperatures. Path 3 second step reaction IM5→IM6 ΔG is always less than 0 within the set temperature range. The third step of the reaction is IM6→P2, and the temperature of ΔG below 958 K is greater than 0, making it difficult to occur spontaneously. The research results on changes in pressure and free energy show that pressure can increase the upper temperature limit for spontaneous reaction.The reaction rates of HCN with H₂ and HCN with H₂O are relatively fast at high temperatures. The rate determining steps for Path 1 and Path 3 at high temperatures are R1 → IM1, R2 → IM5, respectively. The rate constants for the two reaction steps above 1473 K are 9.57×10⁻⁴ and 1.71 mol/(L·s), respectively. The pre-exponential factors for these two reactions were calculated to be 4.45×10⁹ and 4.68×10⁸ s⁻¹, and the activation energies were 357.62 and 239.30 kJ/mol, respectively.

Preparation of silicon foam supported CoMn catalysts and their catalytic performances in higher alcohol synthesis via syngas

DU Xin, ZHANG Mingwei, FANG Kegong

, Available online , doi: 10.1016/S1872-5813(24)60444-5

Abstract(21) HTML (14) PDF 3655KB(6)

Abstract:
A series of silicon foam supported CoMn catalysts were prepared using impregnation, precipitation, and hydrothermal methods. Combining the characterization techniques such as XRD, H₂-TPR, N₂ physical adsorption, TEM, and XPS, the effect of different catalyst preparation methods on the catalytic performance in the synthesis of higher alcohols from syngas was investigated. Research has shown that there are Co²⁺(Co₂C) and Co⁰ species on the surface of the catalyst. The active sites of Co₂C-Co⁰ on the surface of the catalyst prepared by hydrothermal synthesis have a good synergistic effect, which is conducive to the generation of alcohols. A higher proportion of Co₂C also promotes the associative adsorption and insertion of CO, resulting in the highest alcohol selectivity. Under the reaction conditions: t=260 ℃, p=5.0 MPa, GHSV=4500 h⁻¹, H₂/CO(volume ratio)=2∶1, the catalyst exhibited the best reaction performance to achieve CO conversion of 11.1%, total alcohol selectivity of 34.7%, and C₂₊OH selectivity of 34.5%.

Effect of metal support interaction in Cu/ZnO catalyst on the hydrogenation of furfural to furfuryl alcohol

YU Xinrui, ZHANG Jinyu, YANG Haixing, CHONG Siying, LIU Guoguo, ZHANG Yajing, WANG Kangjun

, Available online , doi: 10.1016/S1872-5813(24)60445-7

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Abstract:
Cu/ZnO catalysts were prepared by coprecipitation method and the effect of Cu/Zn ratio on the strong metal support interaction was investigated. The effect of SMSI on the performance of furfural hydrogenation to furfuryl alcohol was also studied. The Cu/ZnO catalysts were characterized by H₂-TPR, XRD, SEM, TEM and XPS. The results showed that there is strong metal-support interaction (SMSI) in the Cu/ZnO catalyst, which changes the microstructure of the catalyst. ZnO support played the role of geometric modification on the active metal Cu particles, and it changed electronic state of the Cu on the surface. SMSI was affected by the change of Cu/Zn ratio, the order of SMSI action is 20Cu/ZnO> 40Cu/ZnO> 60Cu/ZnO> 80Cu/ZnO. Under the same reaction conditions, the furfural conversion rate of the 20Cu/ZnO was higher than 80% catalyst for only 5 h, while the time of the 60Cu/ZnO catalyst reached 28 h. The results show that the activity of the Cu/ZnO catalyst in the furfural hydrogenation reaction was inhibited by the over-strong SMSI action, and the stability of catalysts in the reaction was improved by appropriate SMSI effect.

Preparation of PdAg/CDs-ZSM-5 catalyst and performance study on furfural aqueous phase hydrogenation-rearrangement to cyclopentanone

LIU Li, BAO Guirong, LUO Jia, GAO Peng, JI Xuewu, DENG Wenyao

, Available online , doi: 10.19906/j.cnki.JFCT.2024014

Abstract(8) HTML (7) PDF 14796KB(1)

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With the huge demand for fossil resources and increasing energy consumption, the utilization of biomass as a renewable alternative to the production of chemicals and fuels has attracted much attention. Furfural (FFA), as an important biomass-based derived carbonyl compound, can be industrially produced on a large scale from lignocellulosic biomass feedstocks and converted into various high-value chemicals, liquid fuels, and functional materials through a variety of pathways, which is crucial for alleviating the global fossil resource crisis and achieving carbon peaking and carbon neutrality goals. Carbon dots (CDs) are a new type of zero-dimensional carbon-based nanomaterials with particle size usually less than 10 nm, whose core is usually composed of sp² hybridized carbon, and whose surface contains abundant functional groups such as hydroxyl, amino, and carboxyl groups, which have excellent UV-visible absorption, strong proton adsorption, and good stability and hydrophilicity. The high electron-transferring property of the surface functional groups of CDs makes them excellent electron carriers and donors, especially under UV light irradiation. Especially under the irradiation of ultraviolet light, CDs can be used as a reducing agent and stabilizer to reduce metal ions to metal monomers. Zeolite molecular sieves can effectively promote the diffusion of reactants and products in the pores and improve the catalytic activity due to their highly ordered pores, large specific surface area, suitable pore size and good hydrothermal stability. Therefore, molecular sieves can be a good choice of carrier in multiphase catalysis, and their unique domain-limited environment can provide spatial confinement for metal particles to improve the resistance of metals to sintering and prevent the leaching of active metal substances during the catalytic process. Based on this, in this paper, bimetallic PdAg/CDs-ZSM-5 catalysts were prepared by reduction with zeolite molecular sieve ZSM-5 as the carrier and CDs as the reducing and stabilizing agents via UV irradiation and applied to the aqueous-phase hydrogenation-rearrangement of FFA for the preparation of cyclopentanone (CPO) reaction. The CDs and composite catalysts were characterized by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and pyridine infrared (Py-FTIR). The results showed that the CDs had good reducibility and abundant Lewis acidic sites, and were able to reduce Pd²⁺ and Ag⁺ to metal monomers and form PdAg nano-alloy structures. The effects of reaction temperature, reaction time and hydrogen pressure on the reaction performance of the aqueous-phase selective hydrogenation-rearrangement of FFA to produce CPO were investigated using PdAg/CDs-ZSM-5 as catalyst. It was shown that the synergistic effect between the suitable acidic sites on the composite catalyst and the PdAg alloy greatly promoted the rearrangement of the reaction intermediate FAL, thus selectively controlling the hydrogenation of FFA to produce FAL first and then further rearrangement to obtain CPO. 100% conversion of FFA was achieved at the reaction temperature of 160 ℃, 2 MPa H₂, and the target product CPO under the reaction conditions of 4 h. The selectivity of the target product CPO was 92.6%. selectivity was 92.6%. After reusing the catalyst for 5 times, the conversion of FFA was basically unchanged, and the selectivity of CPO only decreased by 3.6 %.

Study on the antioxidant property of calixarene in high density hydrocarbon fuel JP-10

YANG Yuxin, LEI Quan, CHEN Xinyang, DAI Yitong, FANG Wenjun, GUO Yongsheng

, Available online , doi: 10.19906/j.cnki.JFCT.2024002

Abstract(33) HTML (18) PDF 1312KB(8)

Abstract:
Since the 21st century, hypersonic flight technology has attracted much attention. When the aircraft is flying at a high Mach number, a large amount of aerodynamic heat is generated between the air and the aircraft due to friction, resulting in a rapid increase in the temperature of the aircraft subsystem, exceeding the range that the material can withstand, affecting the flight safety of the aircraft. In order to meet the thermal management needs, an integrated cooling approach combining heat transfer and combustion has been introduced. This method utilizes hydrocarbon fuels both as propellants and coolants to absorb the excess heat from the aircraft's high-temperature components, thereby enhancing energy efficiency and managing the thermal conditions of high-speed aircraft. Fuels that satisfy this concept are called endothermic hydrocarbon fuels. However, these fuels are prone to oxidation due to heat, oxygen, and catalysis during storage and use, leading to the formation of insoluble gums and degraded performance, which may even clog the fuel system, endangering flight safety. Thus, suppressing the oxidation process of high-density endothermic hydrocarbon fuels is crucial for fuel storage and usage. Common methods to improve the oxidation stability of fuels include surface treatment, fuel deoxidation, and the addition of antioxidants to the fuel. Among these methods, adding antioxidants is one of the most commonly used methods. Hindered phenolic antioxidants are favored for their cost-effectiveness, but small molecule antioxidants like tert-butylhydroquinone (TBHQ) and butylated hydroxytoluene (BHT) suffer from sublimation at high temperatures, resulting in poor oxidation resistance. Conversely, commercial macromolecular antioxidants, such as L-1010 and L-1076, fall short of the antioxidant needs of hydrocarbon fuels due to their limited properties. In order to make up for the shortage of commercial hindered phenolic antioxidants, researchers have focused on the development of new antioxidants with high temperature resistance and significant antioxidant effect. Calixarenes, with their structural features of hindered phenols, are seen as potential antioxidants, Especially, the calixarene synthesized with resorcinol as monomer has high phenolic hydroxyl content, which can quench the oxygen free radicals produced in the process of fuel oxidation by providing more abundant hydrogen free radicals, thus has better oxidation resistance. However, reports on using calixarenes for enhancing the oxidation resistance of high-density hydrocarbon fuels remain scarce. In this paper, C-undecylcalix[4]resorcinarene(C₁₁-C[4]R) was synthesized by using resorcinol and dodecanal, and its oxidation resistance in high-density hydrocarbon fuel JP-10 was investigated.and compared with several commercial antioxidants:2,6-di-tert-butyl-4-methylphenol, tetra [β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid] pentaerythritol ester and β-(3,5-di-tert-butyl-4-hydroxyphenyl) propionic acid octadecyl ester. The results of high pressure differential scanning calorimeter (PDSC) showed that the effect of four antioxidants ranked as follows: C₁₁-C[4]R > BHT > L-1010 > L-1076. In addition, the oxidation consumption process of four hindered phenolic antioxidants in JP-10 was analyzed from the perspective of kinetics, and the oxidation consumption rate constant was calculated. The results showed that the reaction rate constant of C₁₁-C [ 4 ] was the smallest and the consumption rate in JP-10 was the slowest. Besides, the oxidation reaction process of JP-10 was also studied using the static kettle accelerated oxidation method. Based on these findings, a potential antioxidant mechanism of C₁₁-C[4]R in JP-10 was proposed.

Mechanism of catalytic decomposition of NO by Cu-ZSM-5

ZHANG Huan, LIU Liang, SHI Yilin, QIAO Xiaolei, JIN Yan

, Available online , doi: 10.1016/S1872-5813(23)60408-6

Abstract(35) HTML (20) PDF 5388KB(4)

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Catalytic decomposition of NO by Cu-ZSM-5 has potential application. In order to reveal the catalytic decomposition mechanism of NO over Cu-ZSM-5, the adsorption of NO over short-range Cu⁺ pairs in Cu-ZSM-5 was simulated based on density functional theory. The reaction pathways of NO decomposition assisted by the by-products N₂O and NO₂ were also proposed. The results showed that the double nuclear copper-oxygen species was an important active centre. During the reaction, the highest activation energy (171.39 kJ/mol) was required for the decomposition of the by-product NO₂ on the binuclear copper-oxygen species. While that for the decomposition of N₂O was 86.92 kJ/mol, suggesting that the decomposition of NO₂ was more difficult. The desorption energy of N₂ and O₂ were 28.43 and 100.78 kJ/mol, respectively. The rate determining step was O₂ desorption. NO acted both as a reactant and a key reductant for the redox cycle of the active centre of Cu-ZSM-5 during the process.

Multi-site Co₂P catalyst derived from soybean biomass for dehydrogenation of formic acid

WANG Bixi, LIU Zeyu, WU Yabei, YANG Yanyan, YANG Song, WANG Xun, YE Zi, DONG Hongliang, ZHU Feng, YU Huanhuan, LÜ Yingying, YU Zhongliang

, Available online , doi: 10.1016/S1872-5813(23)60410-4

Abstract(28) HTML (15) PDF 5673KB(5)

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Formic acid (FA) is a sustainable liquid organic hydrogen carrier and the catalyst for hydrogen production from FA has received significant attention. However, the development of efficient non-noble metal catalysts still remains challenges. In this work, we provide a technologically rather simple and environmental-friendly strategy to synthesize Co₂P catalyst for dehydrogenation of FA by pyrolyzing soybean powder and cobalt salt. The K-containing solid bases in catalyst could act as Lewis acid sites for the HCOO⁻ intermediate adsorption while the self-doped N could act as Lewis base sites to enhance the H⁺ adsorption. The P contained in soybean could combine with Co to form Co₂P for H−C bond cleavage of HCOO⁻. At a Co(NO₃)₂·6H₂O/soybean mass ratio of 1∶15, the as prepared Co₂P catalyst demonstrated a gas production rate of 237.47 mL/(g·h) and a good stability. This study provides a novel strategy to develop non-noble metal heterogeneous catalysts for FA dehydrogenation.

Effects of preparation methods on the performance of InZr/SAPO-34 composite catalysts for CO₂ hydrogenation to light olefins

GUO Shuai, FENG Likui, YU Zhiyong, XU Di, LIU Kaidi, SONG Xiaoning, CHENG Yijie, CAO Qiuyang, WANG Guanghui, DING Mingyue

, Available online , doi: 10.1016/S1872-5813(24)60433-0

Abstract(15) HTML (20) PDF 3781KB(9)

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Light olefins are of great importance as chemical raw materials, and ethylene is a crucial symbol to evaluate the development level of petrochemical industry. Catalytic hydrogenation of CO₂ to light olefins is one of the most vital approaches to utilize CO₂with high added valued. InZr/SAPO-34 composite catalyst shows prominent potential in research and application because of their high light olefins selectivity and high stability in CO₂ hydrogenation. In this study, the effects of different preparation methods of InZr/SAPO-34 composite catalyst for CO₂ hydrogenation to light olefins were studied in depth. The catalyst prepared by co-precipitation method showed the highest catalytic activity, and the catalyst prepared by sol-gel-precipitation method showed the highest light olefins selectivity. The structure-activity relationship of InZr/SAPO-34 catalysts were revealed by various characterization methods.

Surface reaction and lattice oxygen transfer in chemical looping oxidative coupling of methane: Molecular dynamics simulations

LI Wanying, CHEN Liangyong

, Available online , doi: 10.1016/S1872-5813(23)60412-8

Abstract(68) HTML (15) PDF 1890KB(9)

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Chemical looping oxidative coupling of methane (CL-OCM) is a promising methodology for ethylene production from methane. This article utilizes molecular dynamic (MD) simulation to assess the performance of eight metal oxide catalytic oxygen carriers in CL-OCM reactions. It also investigates the impact of reaction time and particle size on the efficiency of the most effective Mn₂O₃COC. The results indicate that extending the reaction time appropriately enhances C₂H₄ selectivity and a C/O ratio of 1 is found to be the optimal size for Mn₂O₃-based CL-OCM. Furthermore, surface reactions and lattice oxygen transfer are analyzed by MD simulation in Mn₂O₃-based CL-OCM, providing deeply insights into the reaction mechanism. The findings reveal that the gas-phase dimerization of CH₃ ^* to form C₂H₆ serves as the primary carbon coupling pathway in CL-OCM. In addition, there are two other carbon coupling pathways, both initiated by CH₂ ^*. Methanol formation through surface combination of CH₃ ^* and OH^* represents an initial step in CL-OCM side reactions. Therefore, inhibiting methanol formation is crucial for enhancing C₂ selectivity in CL-OCM. There exists a transformation of lattice oxygen and surface lattice oxygen plays a key role in methane activation. The quantity of lattice oxygen and difference in bulk lattice oxygen migration resistance are major factors influencing variations CH₄ conversion and C₂ selectivity. This study provides a new way to reaction mechanism exploration related to CL-OCM catalytic oxygen carriers.

Hydrothermal flowthrough pretreatment of biomass and pyrolysis characteristics of residual solid

LIU Tianlong, LI Qi, LI Zhonghong, YANG Peiyan, PANG Xinbo, HUANG Xin, ZHAO Xiaoyan, Cao Jingpei

, Available online , doi: 10.19906/j.cnki.JFCT.2023082

Abstract(73) HTML (29) PDF 4266KB(19)

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The sophisticated multi-components and densed cross-link chemical structures of lignocellulosic biomass are important bottlenecks restricting its value-added utilization. The pre-fractionation of lignocellulose components is of great significance for the fractional conversion of biomass. The present study subjected rice husk (RH) to hydrothermal treatment in a flowthrough mode and investigated the effects of hydrothermal temperature and water flowrate on the decomposition rate of RH, chemical components of residual solids and their pyrolysis characteristics. It is shown that the decomposition of RH under hydrothermal conditions conformed well to the unreacted shrinking core model with phase boundary reactions rate-controlling. The pretreatment at 180 ℃ removed 95% alkali and alkaline-earth metallic species, 92% hemicellulose and 59% lignin from RH and selectively retained most of the cellulose components. As a result of the pretreatment, the relative content of anhydrosugar (mainly levoglucosan) from pyrolysis of RH at a curie-point temperature of 445 ℃ was increased from 9.9% up to 48.2%.

Photocatalytic promotion of benzylamine C-N coupling by oxygen vacancies in bismuth oxychloride@nanocellulose composites

WANG Xiaoxia, SUN Long, QIN Li, SU Jing, WANG Jiajia

, Available online , doi: 10.1016/S1872-5813(24)60437-8

Abstract(27) HTML (9) PDF 3943KB(4)

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In this study, a composite photocatalyst BiOCl@CNC was prepared by simple stirring with BiOCl at room temperature using nanocellulose (CNC) as a carrier. Comprehensive characterizations (XRD, FT-IR, SEM, TEM, XPS) reveal that the abundant hydroxyl groups in CNC can form strong hydrogen bonds with BiOCl, leading to the creation of numerous oxygen vacancies in the material and thereby significantly enhancing its visible light-driven photocatalytic performance. The performance of the BiOCl@CNC was evaluated using the C-N coupling reaction of benzylamine as the target reaction under visible light, and the underlying mechanism was investigated. The results show that the optimal reaction process is that 1.0 mmol of benzylamine and 20 mg of BiOCl@CNC are added to CH₃CN under an oxygen atmosphere to react for 20 hours using a 30 W white LED lamp as the light source. In the substrate expansion experiments, the BiOCl@CNC exhibits remarkable adaptability and exceptional stability towards reactants with diverse substituents. The free radical capture experiments demonstrate that the electrons can effectively generate superoxide radicals in the presence of oxygen vacancies and subsequently form the ultimate product through amine cation radical intermediates. This study not only expands the application potential of Bi-based composite semiconductors but also presents novel insights for synthesizing N-benzylene butylamine.

Effect of Al source on the physicochemical properties of Cu-Al spinel catalysts and the catalytic performance for reverse water gas shift

LIU Yajie, KANG Hefei, LU Ye, ZHANG Peng, GE Hui

, Available online , doi: 10.19906/j.cnki.JFCT.2024013

Abstract(11) HTML (6) PDF 1621KB(3)

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The excessive of fossil fuels has caused a swift rise in global carbon dioxide levels, resulting in severe climate change and environmental pollution. The research on the conversion of CO₂ into high value-added chemicals is of great significance for CO₂ reduction. Due to the high chemical activity of CO, a first conversion of CO₂ to CO is meaningful, which makes the subsequent conversions become easier. Therefore, the reverse water gas shift reaction is considered to be an important intermediate step of CO₂ hydrogenation to methanol, ethanol and other carbon-containing high value-added industrial products. For the reverse water gas shift reaction, several catalyst systems were researched, including supported catalysts, mixed metal oxide catalysts and transition metal carbide catalysts. Among these catalysts, Cu-based catalysts were widely reported owing to the high activity and CO selectivity. Recently, we found that Cu-Al spinel catalysts can be used as the efficient sustained release catalysts for reverse water gas shift reaction. High surface area pseudo-boehmite acts as an appropriate Al source for the synthesis of Cu-Al spinel catalysts by the mechanochemical method. However, the impurity elements in pseudo-boehmites showed significant influence on the formation and properties of Cu-Al spinel, and the catalytic performance for reverse water gas shift reaction. To unravel this point, four pseudo-boehmites with unequal contents of impurity elements (Na, Fe, Si, and S) and copper hydroxide were used for the synthesis of Cu-Al spinel solid solution catalysts by both high-energy ball milling and solid-phase calcination procedures. The physicochemical properties of the catalysts were characterized by ICP-AES, TG, XRD, H₂-TPR, and BET methods, and the catalytic performances were investigated in reverse water gas shift reaction. The results showed that impurity elements in pseudo-boehmite samples had significant effects on the crystal property, reducibility, texture property and catalytic performance of the Cu-Al spinel catalysts. Specifically, Si facilitated the synthesize of high specific surface area catalysts but was detrimental to the formation of Cu-Al spinel, thus leading to a low catalytic activity. Cu-Al spinel catalysts with a small amount of Na and Fe also showed low catalytic activities. S species would be decomposed and removed during the precursor calcination step at high temperature of 950 ℃, thus giving little effect on the catalytic activity. Importantly, the catalyst synthesized based on the pseudo-boehmite with the lowest content of impurity elements had the highest content of hardly-reducible spinel, and exhibited the highest catalytic activity for CO₂ hydrogenation to CO. In addition, the Cu-Al spinel catalyst with the highest catalytic activity was selected for the in-situ DRIFTS and CO₂-TPD-MS characterizations. The results showed that the formate species, including monodentate formate on Al, bidentate formate on Al, and bidentate formate on Cu, were intermediate species of CO₂ hydrogenation to CO over Cu-Al spinel catalysts. Notably, low peak intensities were detected with monodentate formate on Al and bidentate formate on Cu, but the bidentate formate on Al showed higher peak intensity. Especially, the content of bidentate formate on Al was in line with the catalytic activity at different reaction time, implying that the bidentate formate on Al was the main intermediate. This work provides guidance to catalyst synthesis using pseudo-boehmite as raw material.

Synthesis and hydrocracking performance of small crystal NiY zeolites

SUN Jinxiao, WANG Xiaohan, WEI Qiang, ZHOU Yasong

, Available online , doi: 10.1016/S1872-5813(24)60432-9

Abstract(42) HTML (18) PDF 3877KB(9)

Abstract:
A series of small crystal Y-xNi zeolites with different amounts of Ni doping were synthesized by an in situ synthesis method, in which Ni precursors were introduced during the synthesis of small crystal Y zeolites. The active metal Ni was pre-impregnated into the framework of the Y zeolite. Y-xNi series zeolite and ASA were mechanically mixed as support and loaded with Ni and W to prepare Cat-xNi series hydrocracking catalysts. The hydrocracking performance was investigated using n-hexadecane as the reactant. The effects of Ni doping on the physicochemical properties of Y zeolite and catalysts were analyzed by means of characterization such as scanning electron microscopy (SEM), X-ray diffraction (XRD), N₂-adsorption desorption, NH₃ temperature programmed desorption (NH₃-TPD), H₂ temperature programmed reduction (H₂-TPR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The results show that Ni mainly replaces Al into the framework of Y zeolite. The appropriate incorporation of Ni into Y zeolite increases the relative crystallinity of Y zeolite and the number of Brønsted and Lewis acid sites. However, excessive Ni incorporation is detrimental to the crystallization of Y zeolite and excessive non-framework Ni species will cover the surface Brønsted acid sites. Ni doping weakened the metal-support interactions, increased the sulfation of the active metal, the stacking number and dispersion of NiWS, and modified the matching between the metal and acid sites on the catalyst. The results of the catalyst evaluation showed that the introduction of Ni was favorable to improve the selectivity and yield of the middle distillate products (C₈−C₁₂). That is, increasing the number of Brønsted acid sites and NiWS active sites at the same time, improving the synergistic effect between the metal sites and the acid sites, improving the conversion while avoiding over-cracking, and increasing the yield of the middle distillate products. The catalyst Cat-0.2Ni had a higher n-C₁₆ conversion and C₈−C₁₂ product yield at the reaction temperature of 360 ℃, with the n-C₁₆ conversion increased by 10.2 percentage points compared with that of Cat-0Ni, and the C₈−C₁₂ product yield was 65.4%. Therefore, the pre-impregnation of active metal Ni on Y zeolite can effectively regulate the balance between the Hydrogenation and cracking performance to improve the catalytic activity and the yield of middle distillate products.

In situ reduction and carbonation of organogel containing Fe and Mn and their catalytic performance in Fischer-Tropsch synthesis

LI Changxiao, LI Jie, LU Qichao, LIU Jianchao, LIU Lei, DONG Jinxiang

, Available online , doi: 10.19906/j.cnki.JFCT.2024015

Abstract(25) HTML (9) PDF 10071KB(3)

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Light olefins constitute crucial chemical commodities primarily obtained from petroleum through naphtha cracking processes. Given China's energy landscape, characterized by a scarcity of oil, limited natural gas resources, and substantial coal reserves, leveraging coal for synthesizing light olefins emerges as a strategic pathway. This approach not only reduces reliance on petroleum resources but also enhances the value proposition of coal reservoirs. Coal-to-olefin conversion pathways encompass both direct (FTO) and indirect (MTO) methodologies. Notably, the FTO route stands out as a more efficiently and economically viable strategy for coal resource utilization. Fischer-Tropsch synthesis relies on iron carbides as active sites, posing a challenge in elucidating the distinct roles of single-phase iron carbide species within catalysts derived from CO or syngas. To address this challenge, we synthesized a range of organogel precursors incorporating Fe and Mn species. Subsequent in-situ reduction and carbonization of Fe species within the gel matrix under high-temperature conditions in an argon environment yielded Fischer-Tropsch catalysts featuring varying contents of θ-Fe₃C species. The structural composition, surface properties and electronic valence states of the active species of the catalysts were systematically characterised and analysed by XRD, N₂ adsorption, Raman spectroscopy, CO-TPD, CO₂-TPD, XPS, and TEM measurements. The resulting catalysts exhibited a composite composition comprising graphitic carbon, θ-Fe₃C, Fe⁰, and (FeO)_0.497(MnO)_0.503 phases. Catalysts lacking Mn promoter demonstrated superior catalytic activity (91.4%) but lower selectivity towards light olefins (16.0%), with the emergence of the χ-Fe₅C₂ phase post-reaction. This was attributed to the χ-Fe₅C₂ species had higher intrinsic catalytic activity than θ-Fe₃C species. For the catalysts with Mn promoter, the structure of the catalysts and the species of the physical phase remained stable after the Fischer-Tropsch reaction. We believed that Mn promoter played the role of structural promoter and displayed a stabilizing role in the phase structure of the catalysts. Fine-tuning the content of θ-Fe₃C within the catalysts by varying Mn promoter addition enabled a deeper exploration of the correlation between catalytic performance and content of θ-Fe₃C. Fine-tuning the content of θ-Fe₃C within the catalysts by varying Mn promoter addition enabled a deeper exploration of the correlation between catalytic performance and content of θ-Fe₃C. Quantification of θ-Fe₃C content via XRD revealed that content of θ-Fe₃C of the FeMn10 catalysts exhibited approximately 54.5%, resulting in a CO conversion rate of 57.3% and light olefins selectivity of 37.1%. In contrast, content of θ-Fe₃C of the FeMn2 catalysts displayed roughly 19.3%, yielding a CO conversion rate of 10.7% and light olefins selectivity of 24.1%. These findings underscored the pivotal role of θ-Fe₃C as the catalytic core in Fischer-Tropsch reactions, positively correlating with both CO conversion and light olefins selectivity. In addition, the FeMn catalysts exhibited low CO₂ selectivity attributed to the hydrophobic nature of carbon material generated from organic gel pyrolysis. This phenomenon curbed iron carbide oxidation by water, thereby reducing the formation of Fe₃O₄ species and exerting a suppressive effect on the water-gas shift (WGS) reaction. θ-Fe₃C catalysts exhibited excellent light olefins selectivity and low CO₂ selectivity in Fischer-Tropsch synthesis, and had potential for industrial applications.

Effect of zinc content on the structure of Zn species and catalytic properties over Zn/ZSM-5

GENG Rui, LIU Yacong, NIU Xianjun, DONG Mei, FAN Weibin, QIN Zhangfeng, WANG Jianguo

, Available online , doi: 10.19906/j.cnki.JFCT.2023089

Abstract(70) HTML (5) PDF 2321KB(10)

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Studying the status and distribution of Zn species on Zn/ZSM-5 zeolite catalysts were of great significance for determining the active centers and establishing structure-activity relationships in the ethylene aromatization process. The effect of zinc contents of Zn/ZSM-5 zeolites prepared by incipient-wetness impregnation method on catalytic performances in ethylene aromatization were investigated. The structures and acidic properties of the catalyst were studied through X-ray powder diffraction (XRD), N₂ adsorption/desorption, and infrared spectra for pyridine adsorption (Py-FTIR). Besides, inductively coupled plasma-atomic emission spectrum (ICP), diffuse reﬂectance ultraviolet-visible spectrum (UV-vis DRS), extended X-ray absorption fine structure (EXAFS) and linear combination fitting (LCF) analysis on X-ray Absorption near edge spectra (XANES) had finely analyzed the structure and transition of Zn species and the losing rate of Zn species on HZSM-5 molecular sieve catalyst during ethylene aromatization process. The results showed that the introduction of Zn was advantage to improve the selectivity of aromatics hydrocarbon, and Zn contents of the catalyst had obvious influence on the structures, acidic properties, and the status of Zn species, as well as the catalytic performance of Zn/ZSM-5 catalysts. At low zinc loading, 1.5%-Zn(IM)/Z5 catalyst with more active 6-fold coordinated ZnOH⁺ species (55%) showed the highest selectivity to aromatics and catalyst stability. With the increase of zinc amount, the excessive Zn contents not only covered the acid sites and blocked the pore channel, but also changed the local coordination structure and state of Zn species. It was confirmed that the oxidizability of Zn species and the coordination number around Zn sites decreased, accompanied by a weakening of the interaction between Zn and zeolite, leading to the formation of large amounts of 4-fold coordinated ZnO clusters and ZnO crystallites. In the 4%-Zn(IM)/Z5 catalyst, Zn species composed of multi characteristics from ZnOH⁺, ZnO clusters inside the pores, and ZnO crystals on the external surface with relative contributions of 23.5%, 56.1%, and 20.4%, respectively. It meant that ZnO clusters and ZnO crystallites became the main component at the high Zn content. Furthermore, ZnO species located on the outer surface of Zn/ZSM-5 catalysts were easily reduced by H₂ and then transported as zinc vapor to the outer surface, which eventually lead to the loss of Zn species from the catalyst and the decline of the catalytic performance of Zn/ZSM-5 catalyst. The relative proportion of ZnOH⁺ decreased with that of ZnO clusters and ZnO crystallites correspondingly increased considerably with the increase of Zn loading on ZSM-5, accompanied with the elevated rate for Zn losing, and shortened catalyst life. Therefore, a positively correlated between the content of ZnOH⁺ obtained through the UV-vis DRS and LCF analysis on XANES and the rate of aromatics formation was established, further confirming the catalytic nature of ZnOH⁺ as the active center, which played an important role in the aromatization reaction that enhancing the formation of aromatic hydrocarbons. Meanwhile, ZnO on the outer surface of Zn/ZSM-5 catalysts was the main species that losing from catalyst, and influenced the catalytic properties on a certain degree.

Promoted stability of Cu/ZnO/Al₂O₃ catalysts for methanol production from CO₂ hydrogenation by La modification

NIU Mengmeng, JIANG Yanan, ZHANG Xian, ZHANG Cuijuan, LIU Yuan

, Available online , doi: 10.1016/S1872-5813(24)60438-X

Abstract(47) HTML (26) PDF 3064KB(18)

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Deactivation of Cu/ZnO/Al₂O₃ catalysts in CO₂ hydrogenation to methanol reaction is one of the main reasons limiting their application. We synthesized a series of La modified Cu/ZnO/Al₂O₃ catalysts by adding different contents of La to improve the stability. In the 100 h short-term stability test at 200 ℃ under 3 MPa with a GHSV of 12000 mL/(g·h), the unmodified Cu/ZnO/Al₂O₃ catalysts degraded obviously over 100 h. In sharp contrast, the stability was significantly promoted by the addition of La. The best activity was achieved with 5% La added samples (4% CO₂ conversion and 85% methanol selectivity). Which also showed impressive stability over 1000 h except about17% deactivation during the initial 190−220 h. The X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) results revealed that the addition of 5% La improved the dispersion of Cu and Zn , inhibited the sintering of Cu, stabilized the Cu^0/+ species and retarded oxidation of Cu in catalysts, which attributed to the high stability of the catalysts.

Study on the enhancement mechanism of low-temperature SCR performance of ammonium persulfate coupled transition metal oxides modified carbon-based catalysts

XIAO Ling, HUANG Yan, QIAO Shufang, ZHAO Lingkui, LI Simi

, Available online , doi: 10.19906/j.cnki.JFCT.2024006

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In recent years, carbon-based catalysts have received extensive attention in the field of NH₃-SCR due to their unique advantages. In order to improve the performance of low-temperature NH₃-SCR of carbon-based catalysts, V/OAC, Fe/OAC, Mn/OAC and Cu/OAC carbon-based catalysts were prepared by oxidizing and coupling transition metal oxides with ammonium persulfate. The mechanism of SCR performance enhancement of modified carbon-based catalysts was investigated by means of catalytic activity test, Physical adsorption, FT-IR, XPS, NH₃-TPD, H₂-TPR, EPR and other characterization methods. The results show that ammonium persulfate oxidation can introduce a large number of acidic oxygen-containing functional groups to the surface of activated carbon support, promote the formation of oxygen vacancy in transition metal oxides, and improve the surface acidity and redox performance of carbon-based catalysts, therefore the low temperature NH₃-SCR performance of the carbon-based catalyst was improved. In particular, we found that oxidation of ammonium persulfate can induce the formation of lower valence states of transition metal elements (V, Fe, Mn,Cu ). Therefore, after oxidative modification of ammonium persulfate, the performance of V/OAC and Fe/OAC catalysts with low-priced metals in active components conducive to NH₃-SCR reaction is significantly improved, the NO conversion of VO_x/OAC and FeO_x/OAC catalysts at 100 ℃ increased from 18.2% to 34.8% and from 34.2% to 55.6%, respectively; while the performance of Mn/OAC and Cu/OAC catalysts with high-priced metals in active components conducive to NH₃-SCR reaction is limited, the conversion of NO at 100 ℃ only increased from 61.4% to 70.4% and from 61.3% to 69.7%. This work summarized the regulatory effect of ammonium persulfate oxidation modification on the surface metal states of carbon-based catalysts, which is helpful to deeply understand the regulation law of physical and chemical properties of carbon-based catalysts by oxidative modification of ammonium persulfate, and provide guidance and reference for the development of high-efficiency carbon-based denitrification catalysts.

Study on the impact of using decarbonized gasification slag for CO₂ mineralization and storage to prepare calcium carbonate

LI Xiangyu, LI Xu, FAN Panpan, BAO Weiren, CHANG Liping, WANG Jiancheng

, Available online , doi: 10.19906/j.cnki.JFCT.2024008

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Abstract:
The gasification slag after carbon separation is difficult to realize effective utilization because of its high content of water and the presence of a small amount of residual carbon. To address these problems, a mineralization based on indirect carbonation to sequester CO₂ and recycle calcium extraction to prepare nano-calcium carbonate process is proposed. The gasification slag after carbon separation mainly consists of CaO, Al₂O₃, Fe₂O₃, MgO, as well as some non-metallic components such as SiO₂. Most of the metal components exist in amorphous form. After preliminary screening of acidic leaching agents, it was found that hydrochloric acid can effectively destroy the structure of gasification slag and dissolve the metal components in gasification slag. In this paper, the effects of leaching agent type, concentration, reaction time, temperature and liquid-solid ratio on the leaching rate of calcium from decarbonized gasification slag were investigated in detail. The results showed that the highest calcium leaching rate of 98.79% was achieved under the leaching conditions of 2 mol/L HCl, liquid-to-solid ratio of 20 mL/g, reaction temperature of 50 ℃ and reaction time of 90 min. Meanwhile, the effects of CO₂ flow, temperature and time on the carbonation efficiency and precipitated calcium carbonate (PCC) crystal structure were investigated. In the carbonation stage, the main factor affecting carbonation efficiency is CO₂ flow. This is because excessive CO₂ will cause carbonic acid to form in the solution and partially dissolve the precipitated CaCO₃, resulting in a sharp decrease in carbonation efficiency. And the carbonation efficiency gradually increases with the increase of reaction temperature. Generally speaking, increasing the temperature is beneficial for chemical reactions. However, owing to the exothermic nature of the carbonation reaction, the positive promotion effect of high temperature on the reaction process is weakened, and the solubility of CO₂ in water is reduced, resulting in a slow decrease in carbonation efficiency. The effect of reaction time on carbonation process has the same trend as the change in reaction temperature. The highest carbonation efficiency could reach 99.59% by optimizing the carbonation reaction conditions. In addition, the reaction temperature and time significantly affected the calcium carbonate crystal structure and micromorphology. The formation of calcium carbonate crystals mainly goes through three stages. In the first stage, as the reaction time prolongs, disordered amorphous calcium carbonate rapidly dehydrates to form ordered calcium carbonate crystal structure. At high supersaturation, vaterite begins to nucleate and undergoes spherical growth through nucleation at the growth front. Gradually, the solubility of amorphous calcium carbonate gradually decreases, and vaterite continues to grow into polycrystalline spheres composed of roughly equal sized crystals. In the second stage, vaterite is formed under equilibrium conditions, and its crystal size almost no longer increases, leaving part of the remaining amorphous calcium carbonate dissolution and crystallization process. In the third stage, vaterite begins to decompose and forms calcite or aragonite through dissolution-recrystallization process. Experiments result have shown that vaterite and calcite are formed at low temperatures, and aragonite is formed when heated to a certain temperature. As the reaction time increases, the particle size of calcium carbonate gradually increases. Therefore, lowering the reaction temperature and time is more favorable to the formation of vaterite type calcium carbonate.

Study on copper-based oxygen carrier catalytic power plant flue gas deoxidation

SIMA Hao, WANG Xuefeng, DENG Cunbao

, Available online , doi: 10.1016/S1872-5813(23)60409-8

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Abstract:
The main components of power plant flue gas are N₂, CO₂ and part O₂. Injecting power plant flue gas into mine goaf can achieve CO₂ storage and replace nitrogen injection to prevent spontaneous combustion of left coal. However, O₂ in flue gas is one of the factors causing spontaneous combustion of left coal. Therefore, it is urgent to develop an economical and effective catalyst to remove O₂ from power plant flue gas. In this study, four types of copper-based catalysts were prepared using a controllable modulating carrier and loading capacity through co-precipitation method. Additionally, a series of xCuO/CeO₂ catalystswere synthesized. The catalysts were characterized using BET analysis, XRD analysis, ICP analysis, TEM analysis, H₂-TPR and XPS analysis to establish a structure-activity relationship between catalyst structure and deoxidation performance for catalytic power plant flue gases. The results showed that the addition of CeO₂ improved the dispersion of CuO, increased the oxygen vacancy of the catalyst, and improved the activity and reduction oxidation performance of the catalyst. Moreover, the synergistic effect of Cu-Ce interface structure promoted the reduction oxidation process, showing good activity and cycle stability. Among xCuO/CeO₂ catalysts, 30CuO/CeO₂ showed the best catalytic deoxidation performance due to its smallest CuO particle size, highest dispersion and highest oxygen vacancy concentration. The results of this study provide a reference for the development of low cost, recyclable, high activity and high stability deoxidation catalysts.

Preparation of Ni_0.6Cu_0.4O/NC catalyst and its catalytic performance for hydrogen production from hydrolysis of ammonia borane

LI Rong, ZUO Youhua, HUA Junfeng, HAO Siyu, XU Lixin, YE Mingfu, WAN Chao

, Available online , doi: 10.1016/S1872-5813(24)60436-6

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Abstract:
Ammonia borane (NH₃BH₃, AB) is an ideal feedstock for hydrogen production with high hydrogen storage capacity. In this paper, a nitrogen-containing carbon material (Ni_0.6Cu_0.4O/NC) catalyst was prepared by high-temperature carbonization of Ni/Cu-ZIF precursor under nitrogen atmosphere, and the microstructure as well as the composition of the prepared catalyst were investigated by various characterization methods. In addition, the catalytic performance of the catalyst and the variation rule were investigated by the controlled variable method. The results showed that the activation energy (E_a) of Ni_0.6Cu_0.4O/NC catalyzed hydrolysis of AB for hydrogen production was 56.8 kJ∙mol⁻¹, and the TOF value was as high as 1572.2 h⁻¹. The rate of hydrogen production from AB hydrolysis catalyzed by this catalyst could be approximated as a zero-order reaction with respect to the concentration of AB itself, and a one-order reaction with respect to the amount of catalyst. The catalyst still maintained good catalytic activity after ten cycles, indicating its good stability.

Progress in application of binary composite oxides as supports for hydrodesulfurization catalysts

ZHOU Wenwu, HE Xinxin, TANG Xiaoyuan, ZHOU Anning, CHEN Zhiping, HUANG Zhihao, BAI Yexing

, Available online , doi: 10.19906/j.cnki.JFCT.2024019

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Abstract:
Hydrodesulfurization (HDS) technique has been considered to play a crucial role in the clean, low-carbon, and diverse effective utilization of inferior crude distillates. The key to this technology is the development of catalyst with excellent catalytic performance. After decades of development, although the HDS performances for most sulfides of the non-noble metal supported catalysts have been greatly improved, but their catalytic activities for highly refractory sulfides are still limited due to the over-strong metal and support interaction (MSI), insufficient acidity, poor textural properties and damnable surface environments. Researches across the world made a lot of efforts to solve the above problems and the developing of novel support candidates is considered as the most efficient solution. In this review, we summarized the developments for the applications of binary Al₂O₃ based composite oxides and binary TiO₂ based composite oxides as support for hydrodesulfurization catalyst and systematically analyzed the effect of the second component on both the properties of the catalyst, mainly focused on the acidity property, MSI, pore structures and the catalytic performances, and the applications of the corresponding catalysts in thiophene, dibenzoethiophene, 4,6-dimethyldibenzothiophene and inferior diesel fuels. It was concluded that both the MSI and the acidity can be effectively modulated after incorporation of appropriate amount of SiO₂ into Al₂O₃ support, which can be attributed to the successful formation of Al-OH-Si linkages over the support surface and thus prevented the formation of excessive Mo-O-Al bonds, resulted in the enhanced hydrogenation activity of the corresponding catalyst which further contributed to the excellent HDS performance. The introduction of ZrO₂ into Al₂O₃ support can also modulate the MSI and the acidity due to the similar reasons, except for that, researchers also found that the reducibility of the active phase precursors can be effectively enhanced, which is favorable for the formation of more active phases. Introducing small amounts of MgO into Al₂O₃ can effectively enhance the dispersion of active metals over the support surface and promote the formation of Ni(Co)-O-Mo(W) precursors, then acquiring more Ni(Co)Mo(W)S active phases. The introducing of B₂O₃ can effectively lower the density of hydroxyls and promote the formation of octahedral coordinated Mo species which can be easily sulfided. In summary, the introduction of the second component into Al₂O₃ successfully overcame the disadvantages such as the solely acid type and the strong interaction between the metal and the support materials over Al₂O₃ based hydrodesulfurization catalyst, and the advantage of high specific surface area remained. The addition of SiO₂ into TiO₂ support can effectively improve both the acidity property and the stability of the catalyst, moreover, the specific surface area of the catalyst can also be enlarged after SiO₂ addition. After introduction of ZrO₂ into TiO₂, the density of hydroxyl groups over the support surface decreased, the dispersion of active metals improved and the high stacking Mo(W)S₂ slabs formed, thus enhanced the direct desulfurization pathway selectivity. Addition of basic MgO into TiO₂ support can enhance the MSI and thus improve the dispersion of active metals over the support surface due to the strong interaction between the basic-acidic pairs. In summary, the introduction of the second component not only improved the thermal stability and the specific surface area, but also modulated the acidity properties. The main factor causing these changes is that the introduction of the second component profoundly changed the hydroxyl environments. Which further improved the anchorage and dispersion of the precursors over the support surface and promoted the formation of more NiMo(W)S active phase, resulted in the enhanced hydrodesulfurization performances of the corresponding catalysts.

The research progress of formation and control on the N-containing compound of biomass pyrolysis gas

WANG Fengchao, ZHU Hongyu, YIN Xiuli, XU Bin, LI Weizhen, LIU Huacai

, Available online , doi: 10.19906/j.cnki.JFCT.2023090

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Abstract:
Biomass energy plays an important role in combating global warming and the depletion of fossil energy sources. Although different recovery technologies of biomass energy were utilized industrially, the development level of different recovery technologies varies. The application of biomass energy includes technologies such as combustion, pyrolysis, gasification, and fermentation. The pyrolysis technology is an efficient and economical method to utilize biomass energy, which combines the advantage of energy recovery and product diversification. However, the N-containing compounds in the biomass pyrolysis gas make the pyrolysis gas of low quality, which combustion leads to secondary pollution of air. This review summaries the research status of N-containing compounds in the biomass pyrolysis gas, mainly reviewing the differences in the thermos-gravimetric behavior of typical biomass and the four compositions in biomass (cellulose, hemicellulose, lignin, and proteins). There were significant differences in the thermos-gravimetric behavior of biomass with different material compositions, but the whole TG curve can be divided into three stages: in the first stage, the pyrolysis of easily decomposable components in biomass releases small molecule gases and steam; in the second stage, the pyrolysis of cellulose, hemicellulose, and lignin in biomass released a large amount of O-containing bio-oil; in the third stage, the volatile components attached to the surface of the bio-char were cracked again and condensation reaction occurs. The nitrogen content in biomass was high, and during the pyrolysis process, nitrogen migrated into the solid-liquid-gas three-phase, and the migration transformation process was extremely complex. This review also discussed the generation mechanism of N-containing compounds in biomass pyrolysis gas and analyzed the distribution and control research of N-containing compounds. The NH₃ in the low-temperature pyrolysis gas was mainly derived from the direct pyrolysis of protein in biomass. With the increase of pyrolysis temperature, the biomass pyrolysis volatiles were cracked secondly to generate N-containing heterocyclic substances, nitriles, and cyclic amides, and further cracked to produce HCN. Under the high-temperature atmosphere, partial HCN reacts with ·H and generates NH₃ with the biomass char catalysis, leading to a decrease in the concentration of HCN. The N-containing heterocyclic substances from the second cracking of volatiles were the main resource of HCNO, and HCNO has a relatively lower concentration and is easily reduced to HCN and NO. Thus, with the pyrolysis temperature increase, the main components of N-containing compounds in the pyrolysis gas were gradually converted from NH₃ and HCNO to NO and HCN. When the temperature was 800 ℃, the concentration of NO accounted for 40% of the N-containing compounds in pyrolysis gas. While, at 900 ℃, NH₃ and HNCO were barely detectable. At the same time, it pointed out the difficulties and challenges faced in the practical application of N-containing compound removal. It is necessary to establish a generalized mechanism for nitrogen conversion during the thermal conversion of biomass. The nitrogen transport and control mechanisms during biomass pyrolysis need to be further improved. And, the key research directions in the process optimization and economic analysis of N-containing control are further anticipated. This review aims to provide a theoretical basis and technology support for biomass pyrolysis gas purification.

Recent advances in the preparation of high-value-added chemicals by catalytic hydrogenolysis of lignin

LIU Juping, TANG Ziyue, CHEN Yingquan, WANG Xianhua, CHEN Hanping, YANG Yang, YANG Haiping

, Available online , doi: 10.19906/j.cnki.JFCT.2024009

Abstract(60) HTML (7) PDF 7951KB(12)

Abstract:
The development and utilization of renewable biomass resources is an effective way to achieve CO₂ reduction. Biomass, on the other hand, has a complex structure with low overall reactivity and utilization. Lignin is the only renewable aromatic polymer with high energy density in nature, and its conversion and utilization have attracted much attention worldwide. However, the complexity of the lignin structure, the uncertainty of the linkages, the stability of the side-chain connections, and the inevitable recondensation of the reactive fragments make the depolymerization of lignin into biofuels or aromatic chemicals a formidable challenge. Catalytic hydrogenolysis technology converts lignin into highly selective, high-yield phenolic monomers with high heating value, low oxygen content, and high carbon utilization of the product. However, the mechanism of the conversion between products and structures remains unclear with respect to the directed bond shearing during the catalytic depolymerization of lignin. In this paper, in view of the latest research progress on the catalytic hydrogenolysis of lignin for the production of high-value chemicals. We focus on the catalytic hydrogenolysis of lignin to summarize the coupling correlation between the catalysts and their products of high-value chemicals and focus on the influence of different catalyst systems on the process mechanism of lignin depolymerization products. For metal-based catalysts in particular, a detailed review of recent advances in the effects of noble metal-based catalysts, transition metal-based catalysts, hydrotalcite catalysts, and metal-organic framework catalysts on product distribution is presented. And further summarized the problems and conversion mechanisms of different catalysts. Meanwhile, the solvent in the lignin catalytic hydrogenolysis cracking process is the key to promote lignin dissolution, accelerating the heat and mass transfer, and promoting the homogeneous dispersion of reactants and catalysts in the reactor. In this paper, the main solvents for lignin liquefaction, such as water, alcohol, and new solvent systems, are reviewed for their depolymerization impact on lignin. And further, outline the effect of the solvent system on the properties of lignin conversion products. Nevertheless, there are still many difficulties in the catalytic hydrogenolysis of lignin for the preparation of high-value chemicals. The complexity of the macromolecular structure of lignin, the directed depolymerization of the C−O and C−C structures is still difficult, and the preparation of efficient catalysts as well as the mechanism of directional regulation of the products are still to be further investigated. Due to the insolubility of lignin, no solvent system that can completely dissolve lignin has been found yet; secondly, the research on the solvent effect is still only in the preliminary exploration stage. Novel technology for favorable conversion of lignin is still only at the stage of laboratory research. And the efficient conversion of renewable lignin into valuable chemicals and fuels is of great significance in solving the energy crisis and slowing down global warming, and at the same time, it will help our country to realize the energy-dependence transition from oil to renewable biomass. So finally, the opportunities and challenges facing the field are summarized and outlooked, providing a theoretical reference for efficient targeted conversion and high-value utilization of lignin.

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