Abstract: In supercritical water (SCW) condition, the gasification of biomass to H2 or CH4 has been studied extensively and proves to be critical in realising the upgrading of carbonaceous fuels. Given the extreme conditions of water at high pressure and temperature, along with the complex structure of biomass, the development of such a process still remains a challenge. In order to realize the complete decomposition of biomass and a high yield of desired products, such as CH4 and H2 at relatively milder conditions, various catalysts were synthesized and practiced. Different metals (such as Cr, Ni, Zn, Ru and Rh) were incorporated into various supports, such as mineral compounds of Al2O3, SiO2, TiO2, ZrO2, MgO, Y2O3, CeO2, silica-alumina, zeolites and carbon based supports of carbon nanotube, activated carbon. As a result, the long term stability of catalys is critical in the gasification of carbonaceous fuel in supercritical water condition. Therefore, this work focused on the stability of various support materials and deactivation of active metal components in supercritical water conditions with the purpose of choosing robust catalysts. In supercritical water condition, the effect of catalyst on carbonaceous fuels cracking, methanation reaction and water gas shift reaction determines the gasification efficienty as a whole. Unfortunately, the mechanism of methanation reaction is still unclear. Therefore, the CH4 formation mechanism and the effect of catalyst on CH4 conversion are emphasized in this work.
Abstract: Biomass can be converted into high-value nitrogen-containing chemicals and nitrogen-containing carbon materials by pyrolysis technique, which significantly increases the value of biomass and lowers the risk of environmental pollution by nitrogen-containing pollutants. Therefore, a good understanding of the migration and conversion mechanisms of nitrogen during pyrolysis is critical for the advancement of biomass pyrolysis technique. Herein, the forms and contents of nitrogen in biomass were first summarized. Afterward, the transformation process of nitrogen from biomass to pyrolysis products was discussed based on the distribution of nitrogen in the solid, liquid, and gaseous pyrolysis products. Finally, the effects of fuel properties, pretreatment methods and pyrolysis conditions on the migration and transformation of nitrogen were discussed carefully. In addition, an outlook for future research on nitrogen migration in biomass pyrolysis process was provided.
Abstract: Co-gasification of coal and biomass, as one of the means to achieve efficient and clean utilization of coal, has a positive contribution to achieving carbon neutrality and carbon peaking. Co-gasification not only helps to overcome a series of problems derived from coal gasification alone, reduces the emission of SOx, NOx and other harmful substances, and improves coal reactivity but also helps to overcome the problems of low energy density, poor gasification efficiency and high tar yield existing in biomass gasification alone. Based on this, the progress in the research of influencing factors and synergetic reaction mechanism is reviewed in this work. The effects of feedstock type and pretreatment method, process parameters and gasifier type on the co-gasification process are summarized, the catalytic synergistic mechanism in the co-gasification process of coal and biomass is systematically described, the synergistic mechanism of non-catalytic factors in the co-gasification process is briefly outlined, and new methods to study the co-gasification process are comprehensively discussed. The main concern of the co-gasification process is sorted out, and prospects are made for constructing the synergistic pathway with the help of the new in situ technique and revealing the reaction mechanism in coupling the chemical reaction system with the combination of density functional theory and gasification dynamics models.
Abstract: Catalytic pyrolysis technology can convert waste plastics into high-quality carbon nanotubes (CNTs), achieving the recycling and high-value utilization of waste plastics. However, the process of plastic catalytic pyrolysis is complex, with numerous influencing factors, and the growth mechanism of carbon nanotubes is unclear. Therefore, this article elaborates on the influence of plastic structure and pyrolysis process on the growth process and structural characteristics of carbon nanotubes from the perspectives of plastic type, temperature, catalyst, etc., and analyzes the nucleation and growth mechanism of carbon nanotubes. It is found that the type and temperature of volatile matter will affect the structure of CNTs, while the performance of the catalyst will affect the diameter and growth mode of carbon nanotubes. The force between the catalyst and CNTs depends on the type of catalyst, and the carbon diffusion intensity at the boundary of CNTs is influenced by reaction conditions, catalyst and carbon source types. The relative size between the two determines the specific process of CNTs nucleation and growth.This review provides theoretical reference for the understanding of the process of preparing carbon nanotubes from waste plastic pyrolysis and the development of waste plastic resource utilization technologies.
Abstract: Lignin is a natural and renewable resource with aromatic structure. It can be converted into bio-oil by hydrothermal liquefaction. Due to the complex structure of wood fiber, the structural characteristics and reactivity of different kinds of lignin are different. Therefore, three typical lignin (kraft lignin (KL), enzymatic hydrolysis lignin (EHL) and ethanol lignin (OL)) were selected as raw materials. Firstly, physical and chemical properties of the raw materials were analyzed. Secondly, effects of reaction conditions on characteristics of their hydrothermal liquefaction bio-oil were investigated. Among them, EHL and OL are guaiacyl units. OL has the highest content of carbon and hydrogen elements, and its higher heating value reaches 23.54 MJ/kg. The aromatic characteristics are more obvious, and the phenolic hydroxyl content is relatively high. KL is mainly syringyl unit with less methoxy and phenolic hydroxyl groups. The results of liquefaction experiment show that when the reaction temperature was 300 ℃, yield and energy recovery rate of lignin bio-oil were the highest. The bio-oil yield ranked in the order of OL>KL>EHL. H/C ratio of bio-oil was concentrated within 1.0-1.4. Chemical composition of the three bio-oils was different. OL bio-oil contains 9.14% aromatic hydrocarbons, EHL bio-oil contains 41.34% phenolic species, and KL bio-oil has a higher acid content.
Abstract: Mono-aromatic hydrocarbons (MAHs) are important basic raw materials for organic chemicals industry. Catalytic pyrolysis of lignin can produce MAHs. However, the complicated components of pyrolysis vapours can result in rapid coke deactivation of the catalyst and the lower yields of mono-aromatic hydrocarbons. The lignin pyrolysis vapours were upgraded to MAHs by Ni or Ga modified hierarchical zeolite (HZSM-5@Al-SBA-15). The distribution of catalytic pyrolysis products and the coke deposition behavior of catalysts were investigated in a fixed bed reactor. Results showed that the hierarchical zeolites had the developed pore structure, which could effectively improve the mass transfer and diffusion performance of lignin pyrolysis vapours. Moreover, the introduction of metal elements and mesoporous shell modulated the acidity distribution of the catalysts. Compared with the pure HZSM-5, the relative content of MAHs (78.63%), Ga/HS (77.15%) and Ni-Ga/HS (72.44%) were increased, and the content of poly-aromatic hydrocarbons was effectively inhibited. The content of CO2 in the gas products increased, indicating that the catalyst could promote the decarboxylation reaction. In addition, the content of coke deposition with supported hierarchical zeolite catalysts was significantly reduced, which were Ni/HS (7.79%), Ga/HS (6.37%) and Ni-Ga/HS (6.63%), respectively. This indicated that the introduction of metal components improved the anti-coke performance of the catalysts. Therefore, the supported hierarchical zeolite based on metal modification and pore optimization could upgrade the lignin pyrolysis vapours into high quality aromatic hydrocarbons. This study provides a basic reference for the high value utilization of lignin waste.
Abstract: This study investigated the effects of decoupled temperature and pressure on lignin during the hydrothermal process. The effect of hydrothermal treatment on the lignin structure was evaluated, and the effects of decoupling temperature and pressure on the liquid products of the lignin were assessed under decoupling conditions. The results showed that lignin was composed almost entirely of the G-type monomer of coniferyl alcohol. After hydrothermal treatment, C–O bonds such as β–O–4 ester bonds in lignin were broken. Methoxy and aliphatic structures linked to oxygen-containing structures were converted into aliphatic carbon skeletons. The liquid phase products were initially vanillin and 3-(4-hydroxy-3-methoxyphenyl)-1-propanol, which were subsequently converted to guaiacol mainly by inter-monomer conversion and cleavage of the β–O–4 bond of the terminal guaiacyl unit of lignin. The decoupled high pressure inhibited the production of lignin liquid products and decreased the selectivity of isoeugenol in the products. The results of this paper are expected to provide more fundamental knowledge and understanding for the optimization of hydrothermal conversion process conditions of lignin.
Abstract: The effects of K2CO3 (PC) and K2FeO4 (PF) on the catalytic pyrolysis of herb residue were investigated by using a thermogravimetric analyser, online mass spectrometry and a fixed-bed reactor, using herb residue as the raw material and loaded with PF and PC catalysts respectively by impregnation. The results showed that both PC and PF lowered the pyrolysis reaction temperature of the herb, enhanced the water vapour reforming reaction and significantly increased the pyrolysis gas yield and H2 content. At 500 ℃, the catalyst promoted the production of H2 and increased the H2/CO ratio of the pyrolysis gas from 0 to 1.29 and 1.92, respectively; at 700 ℃, PC and PF can significantly reduce the liquid-phase yield and increase the H2/CO of the gas product, with PF being more effective, reducing the liquid-phase yield by 30.9% and increasing the H2/CO increased by 38.5%. However, PF will decompose and release oxygen during the pyrolysis process, which makes NO emissions increase.
Abstract: Light aromatics are extremely important building blocks in the chemical industry which can be produced from the catalytic fast pyrolysis (CFP) of biomass. In this work, wet torrefaction pretreatment (WTP) was employed to improve the quality of poplar wood (PW) in terms of the synergetic deoxygenation and demineralization. Then, metal-modified hierarchical HZSM-5 was prepared by the combined approach of NaOH desilication pretreatment and metal (Zn, Ga, and Fe) modification. At last, the CFP of torrefied PW was carried out by using the metal-modified hierarchical HZSM-5 as catalyst to produce light aromatics. Results showed that the deoxygenation and demineralization rates gradually increased with the increase of WTP temperature from 180 to 260 ℃, the maximum removal rates of oxygen, K, Mg, Ca, and Na were 47.96%, 90.99%, 86.65%, 66.09%, and 36.29%, respectively. NaOH desilication pretreatment and metal modification on HZSM-5 promoted the formation of light aromatics. The Zn-modified hierarchical HZSM-5 presented the highest yield of light aromatics. The yield of aromatics increased first with the raise of catalyst-to-torrefied PW ratio from 1:1 to 1∶3, then decreased slightly at the highest catalyst-to-torrefied PW ratio of 1∶5. At last, the operation parameter of WTP and CFP was optimized which the maximum yield of light aromatics was 7.83 × 107 p.a./mg at WTP temperature of 220 ℃, catalyst-to-biomass ratio of 3∶1, and CFP temperature of 850 ℃.
Abstract: In this study, the thermal degradation mechanism of avermectin (AVM) was analyzed via experiments and density functional theory calculations (DFT). The experimental results of AVMD pyrolysis indicated that the removal rate of AVM residues reached peak value of 99.88% above 250 °C. The main product of AVM pyrolysis was alcohols. Based on the C−O bonds breaking, four potential degradation pathways were proposed. The findings of the calculations were in agreement with those of the experiments. These results provide theoretical and empirical guidance for the development of safe antibiotic disposal technology.
Abstract: Plastics as co-feeding can effectively improve the quality of microalgae pyrolysis oil. The effects of co-pyrolysis of microalgae and polyethylene (PE), polystyrene (PS) and polypropylene (PP) on pyrolysis characteristics and kinetics were investigated by TG-FTIR. There is an interaction between microalgae and plastic, which increases the pyrolysis temperature of plastic and inhibits the formation of coke. PE can effectively reduce the residual yield, while the pyrolysis temperature of PS obviously transfers to high temperature during co-pyrolysis. In addition, co-pyrolysis reduces the average activation energy, especially low proportion of plastic. Besides, the co-pyrolysis of microalgae with PE promotes C−C fracture to release CO2 and −CH3 and C=C−H. However, the co-pyrolysis of microalgae and PP inhibits the release of CO2, and intensifies the formation of aromatic hydrocarbon C−H from polypropylene. Moreover, the co-pyrolysis of microalgae and PS can slightly promote the formation of C=O and NH3, and aggravate the hydrogen transfer of microalgae to break aromatic ring of polystyrene and release CH3.
Abstract: A bifunctional carbon-based solid acid catalyst was prepared by sulfonation of sulfuric acid to using gelatin and phytic acid (PA) as carbon sources and doping with FeCl3·6H2O and ZnCl2, which was used to efficiently catalyze the preparation of furfural from xylose. The catalysts prepared at different carbonization temperatures were characterized by SEM, BET, FT-IR and STEM-EDS techniques, and the physicochemical properties of the catalysts were revealed. The effects of carbonization temperature of the catalyst, molar ratio of FeCl3·6H2O to ZnCl2, reaction temperature, reaction time, volume ratio of γ-valerolactone (GVL) to H2O and catalyst dosage on the conversion of xylose to furfural (FF) were investigated. The results showed that the catalytic activity of CNPS600-Fe4-Zn2 was higher when the carbonization temperature was 600 ℃. The xylose conversion rate was 99.6%, and the molar yield of FF reached 85.8% when the reaction was carried out at 170 ℃ for 120 min using 0.03 g CNPS600-Fe4-Zn2 (the molar ratio of FeCl3·6H2O to ZnCl2 was 4∶2) as catalyst, 3 mL GVL/H2O (the volume ratio of was 9∶1) as solvent and 0.06 g xylose as raw material. In addition, the cyclic performance of the catalyst was tested. The FF molar yield and xylose conversion rate remained above 80% after 5 cycles, indicating that the catalyst had higher catalytic activity and better hydrothermal stability.
Abstract: The carbon and nitrogen content of township waste is high, and direct combustion causes a large amount of CO2 and NOx emissions. The biomass carbon after pyrolysis can reduce the NO in the combustion flue gas to N2, which can reduce NOx emissions while using carbon resources. Using 6 typical components in 4 kinds of rural solid waste (including paper, plastic, wood and textile) as experimental materials, the pyrolysis and decoupling combustion experiments are carried out in a fixed-bed reactor to investigate the effect of decoupling combustion on NOx emission. The experimental results showed that when the pyrolysis temperature was 700 ℃ and the particle size were 1.6–2.5 mm, the concentration of reducing gas in pyrolysis gas was higher and the reduction rate of NO in the char reached over 60%. By comparing the N conversion of decoupling combustion with that of normal combustion and air staged combustion, the NOx emission reduction rates of the decoupling combustion were 44.1% and 18.1%, respectively. Therefore, the decoupling combustion of rural solid waste based on pyrolysis is an effective way to control NOx emission, which is conducive to the clean and efficient transformation and utilization of rural solid waste.
Abstract: In this study, density functional theory was used to explore the effects of different nitrogenous biochars and CaO-coupled nitrogen-doped biochar on the adsorption performance of NO. The theoretical calculation results showed that nitrogen-doped biomass char had a better adsorption effect on NO under N-down adsorption mode, and the adsorption energy of N-5 biomass char (CN-5) was higher than that of nitrogen-containing biochar, and its adsorption energy was −41.22 kJ/mol. CaO significantly improved the adsorption capacity of biochar to NO, and CaO coupled with the substrate containing N-5 biochar (CaO/CN-5) as an electron donor provides more charge for NO, and its adsorption energy was 216.862 kJ/mol higher than that of CN-5, and the adsorption performance of biochar was significantly improved under the coupling of CaO and N-5 groups. The adsorption capacity of NO on the surface of biochar decreased with the increase of temperature, and increasing the amount of biochar containing N-5 was more conducive to the adsorption of NO, while the coupling of CaO further increased the adsorption capacity of NO-5 surface NO, and the adsorption capacity of CaO/CN-5 system reached 2.846 mmol/g at 273 K.
Abstract: In this study, density functional theory was used to study the influence mechanism of pyrroleaze-containing biochar (CN5) and its coupling of different metal oxides (ZnO, CaO, Na2O) on the adsorption characteristics of CO2. Calculating the adsorption capacity of CO2 on different metal oxides coupled with pyrrole nitrogen-containing biochar (CN5@MOx∶CN5@ZnO, CN5@CaO, CN5@Na2O), and analyzing the difference in adsorption capacity combined with adsorption heat, it was found that CO2 multi-layer adsorption occurred on the CN5@Na2O surface, compared with CN5@ZnO and CN5@CaO, CO2 adsorption heat and adsorption capacity on CN5@Na2O were higher, reaching 6.11 mmol/g at 100 kPa and 20 ℃, with stronger interaction and more utilization of adsorption. The CN5@MOx adsorption energy was further investigated, and the calculation results showed that the CN5@Na2O adsorption energy for CO2 was higher than that of CN5@CaO and CN5@ZnO, which was consistent with the adsorption capacity. The charge differential density and state density analysis were carried out, and the charge differential density showed that due to the participation of Na in Na2O in adsorption, charge transfer occurred between O in CO2, and the state density analysis showed that CO2 was more stable adsorption on the CN5@Na2O surface.
Abstract: Highly efficient and environmentally friendly utilization of coal gasification slag is a hot research subject in the coal chemical industry at present. The preparation of activated carbon with a flotation refined carbon from gasification slag, a long flame coal, a high temperature coal tar containing 70% asphalt and an active agent in proper proportion was carried out. The influence of activation temperature and time on the surface properties and compressive strength of the produced activated carbon was investigated in a tube furnace. The oxygen functional group, pore structure and absorption performance of the produced activated carbon were characterized by FT-IR, N2 adsorption-desorption, SEM and iodine adsorption. The COD removal from biochemical waste water by the produced activated carbon was verified. The results show that the key factors for the effective formation and expansion of pore are the suitable activation temperature and time for the floatation refined carbon from gasification slag as the feedstock. The activated carbon prepared by carbonization at 550 ℃ for 30 min and steam activation at 950 ℃ for 2 h exhibits a crisscross morphology of organic carbon components and minerals. The surface area, pore capacity and average pore diameter are 566 m2/g, 0.5611 mL/g and 5.1 nm, respectively, with the characteristics of a concentrated pore distribution and a certain quantity of mesopore. Both iodine value (650 mg/g) and methylene blue value (128 mg/g) meet the requirements of the Chinese standard “Technical Specifications and Test Methods of Activated Carbon for Purification of Industrial Wastewater”. The COD in biochemical waste water treated by the activated carbon for 60 min with a solid-to-liquid ratio of 0.6 g/L can be reduced to lower than 30 mg/L, meeting the B class water quality of the Chinese standard “Integrated Discharge Standard of Water Pollutants” (DB11/307—2013).
Abstract: An efficient dehydrogenation catalyst is crucial for the application of ammonia borane (NH3BH3, AB) as a solid chemical hydrogen storage material. In this work, a kind of nitrogen-doped rice husk activated carbon (N-RHC) was prepared by roasting melamine and rice husk at high temperature under nitrogen atmosphere. With N-RHC as the support, the rice husk-based carbon supported ruthenium catalyst (Ru/N-RHC) was prepared through impregnation with the RuCl3 solution and its catalytic performance in the hydrolysis of ammonia borane to produce hydrogen was investigated. The results indicate that the Ru/N-RHC catalyst with a Ru loading of 5% performs excellently in the hydrolysis of ammonia borane; the reaction turnover frequency (TOF) reaches 83.71 min−1 and the apparent activation energy decreases from 88.9 to 64.9 kJ/mol under light irradiation. In addition, the hydrogen production rate is positively correlated with the content of ammonia borane and catalyst.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
