Abstract: "Thermal Dissolution based Carbon Enrichment" (TDCE) is the thermal extraction of lignocellulosic biomass wastes using non/weak polar organic solvents under mild conditions (350 °C, nitrogen atmosphere). After a series of deoxygenation and aromatization reactions, the obtained target solid products Soluble and Deposit have the advantages of anhydrous, ashless, high calorific value, etc. At the same time, this technology also has the advantages that the solvent does not participate in the chemical reaction and can be recycled and reused. Therefore, thermal solution carbon enrichment is one of the effective ways to realize biomass energy conversion. This paper firstly introduces various ways of biomass utilization at present; and then focuses on the factors affecting carbon-enrichment, reaction mechanism and product utilization pathways of biomass thermal solution. Under the background of the national strategy of "carbon neutrality", biomass thermal solution carbon-enriching technology has obvious economic value and social significance.
Abstract: Combining with the characteristics of high yield of mineral humic acid (HA) and high activity of biochemical HA, co-thermal oxidation of low rank coal and biomass to produce complex HA (MIXHA) was newly proposed. The mixture (MIX) of Heilongjiang lignite (HL) and wheat straw (WS) was co-thermally oxidized in 10% HNO3 solution to prepare MIXHA. This work focused on comparison of the macro morphology and microstructure of MIXHA between HLHA and WSHA by SEM, FT-IR and 13C NMR analyses, and explored the synergistic effect between HL and WS during the co-thermal oxidation process. The results show that MIXHA content is higher than the theoretical value. Decomposition of HNO3 molecular produces active oxygen atoms and nitrogen oxides to attack the molecular structure of WS and HL. Due to hydrogen bond rearrangement, glycosidic bond rupture, and crosslinking, plenty of alkyl radicals generated in WS are combined with the condensation aromatic ring in HL. Thus, the protonated aromatic carbon is changed into aliphatic substituted aromatic carbon. The obtained MIXHA is rich in oxygen-containing functional groups, and has high activity. Obvious characteristic peaks are observed in FTIR spectra of MIXHA. This work would provide a new idea for classification and resource utilization of low-rank coal and agricultural and forestry wastes.
Abstract: In this study, a series of catalysts with different Fe3O4 to iron carbide ratios were obtained by carburizing the α-Fe2O3 precursor prepared by co-precipitation method, under various carburization conditions. XRD, Mössbauer spectroscopy, XPS, and Raman spectroscopy were used to characterize the bulk and surface phase compositions of the Fe-based catalysts. The results show that increasing the carburization temperature and prolonging the carburization time lead to higher iron carbide concentration. To explore the active phase of CO2 formation, the catalysts were tested under different reaction conditions by tuning either CO conversion or H2O partial pressure. It turns out that the catalytic performance of the Fe-based catalyst in the FTS and water-gas shift (WGS) reactions is influenced by both the content of iron carbide and the degree of carbon deposition. Under typical Fischer-Tropsch reaction condition, the CO2 selectivity is determined by the CO conversion rather than the Fe3O4 content in the catalyst, meaning that the WGS reaction is here limited by the kinetic factors. On the contrary, adding H2O to the reaction gas results in the trend that higher CO2 selectivity is promoted by higher content of Fe3O4 in the Fe-based catalyst. It seems that Fe3O4 is the main active phase for the WGS reaction in the iron-based catalyst for FTS. These results provide a new insight into the active phase of CO2 generation on the Fe-based catalysts, which could be the theoretical basis for the design of new industrial FTS catalysts with low CO2 selectivity.
Abstract: The NiMo catalysts were prepared using the mechanical ball milling method, and their structures were characterized by XRD and XPS to investigate the effects of the Ni/(Ni+Mo) ratio on catalyst composition and structure, as well as the performance of phenanthrene hydrogenation. The results show that the catalysts prepared by this method have good dispersion of active components Ni and Mo, and are mesoporous catalysts with a concentrated pore size distribution in the range of 2−10 nm. The specific surface area and MoIV content of the catalysts increase first and then decrease as the Ni/(Ni+Mo) ratio increases, both reaching maximum values at 0.33. The moderate amount of Ni promotes Mo sulfidation to form the NiMoS active phase, while the excessive amount of Ni forms NixSy, which covers active sites and reduces the hydrogenation activity. When the Ni/(Ni+Mo) ratio maintains at 0.33, the specific surface area of the catalyst decreases as Ni and Mo content increases, while MoIV content shows an increase trend. Raising the amount of sulfurizing agent ammonium thiosulfate (ATS) could increase both the specific surface area and MoIV content of the catalyst. It is observed that the effect of the Ni/(Ni+Mo) ratio on phenanthrene conversion is consistent with the MoIV content of catalyst, and the maximum value of 74.7% is obtained at the Ni/(Ni+Mo) ratio of 0.33. This further rises to 96.5% when the Ni and Mo contents and S/Mo ratio increase to 4.8%, 16% and 4.5, respectively. Meanwhile, the total selectivity and yield of octahydrophenanthrene and perhydrophenanthrene reach 83.9% and 80.9%, respectively. Furthermore, perhydrophenanthrene is mainly formed by hydrogenation of side ring of phenanthrene.
Abstract: ZSM-23 zeolite was successfully synthesized in a dual-template system, and ZSM-23-Al2O3 composites with different ratios were also prepared. The hydroisomerization performance of Pt/ZSM-23 catalyst was manipulated by introducing Al2O3, and the influence of Al2O3 on physicochemical properties was investigated by XRD, SEM, TEM, N2 physical adsorption-desorption and NH3-TPD characterizations. The results showed that Al2O3 improved the dispersion of Pt, significantly reduced the acid sites concentration of the catalyst, and regulated the metal-acid balance in quantitative. The suitable metal-acid balance concentration could improve the selectivity of isomers and suppress the cracking reactions. Meanwhile, Al2O3 dispersed the ZSM-23 grains, which improved the dispersion and increased the number of exposed pores in ZSM-23. Thus the diffusion efficiency of reactants and intermediates could be promoted and the isomer products selectivity could be improved. All composite catalysts showed high selectivity of isomer products, among which, Pt/(9Z-1Al) had the highest yield of isomer products due to its suitable metal-acid concentration balance, reached 60% at 340 ℃, which was a significant improvement compared with Pt/ZSM-23 (42%). When the reaction temperature was lower than 310 ℃, the pore mouth mechanism dominated in Pt/ZSM-23, while the key-lock mechanism was significantly strengthened at higher reaction temperature. After the introduction of Al2O3, more adjacent pores in ZSM-23 were exposed and the key-lock mechanism became the domination, which led to a large number of 7/8Me-C15 isomers.
Abstract: A highly efficient cerium-modified Cu/hexagonal mesoporous silica (xCe-Cu/HMS) catalyst for the vapor-phase hydrogenation of dimethyl oxalate (DMO) into ethylene glycol (EG) was prepared using an ammonia evaporation method. The Ce promoter can significantly improve the performance of the catalyst, and the best catalytic performance was obtained after the introduction of 1.2% Ce promoter on Cu/HMS. The DMO conversion and EG selectivity got to 99.6% and 96.3%, respectively, under moderate conditions (200 °C, 2.0 MPa, H2/DMO = 100 and LHSVDMO = 1.2 h−1). Characterization results revealed that Ce modification can enhance the interaction between Cu and the support, improve the dispersion of Cu on HMS, and maintain the appropriate ratio of Cu+/(Cu++Cu0). In this study, a simple and low-cost method was used to synthesize Ce-modified Cu-HMS catalysts, which showed excellent catalytic performance in conversion of DMO to EG under moderate conditions.
Abstract: Hydrogen production from electrolyzed water driven by sustainable energy is an effective way to achieve the hydrogen economy with zero carbon emission. Alkaline electrocatalytic hydrogen evolution reaction (HER) is one of the main energy transforming processes in the field of electrolytic water technology. The development of active and cost-effective nonprecious catalytic electrodes is of great importance to alkaline hydrogen evolution reaction. Amorphous nanosized nickel-boron alloy particles (NiB-COS) have been obtained by using chitosan oligosaccharides (COS) as a stabilizer via chemical reduction method. The as-prepared electrocatalysts have been used for the hydrogen evolution reaction (HER). The electrocatalysts have been characterized by using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma analysis (ICP) and X-ray photoelectron spectroscopy (XPS). NiB-COS displays a significant increase in hydrogen evolution reaction properties in alkaline media, affording low overpotentials of 49.4 mV at 10 mA/cm2 and 15.1 mV onset overpotential for the hydrogen evolution reaction. Tafel slope of NiB-COS is 86.1 mV/dec. Remarkably, the formation of a nickel-boron alloyed phase and the decrease of particle size are helpful to improve HER activity of NiB-COS. The experimental data indicated that the NiB-COS showed excellent long-term stability as a very active electrocatalyst.
Abstract: In this work we report the feasible modification of graphitic carbon nitride (g-C3N4) polymer through a post-functionalization progress. The resultant photocatalyst exhibits boron doping and mesoporous structure with a high surface area of 125 m2/g, leading in an increased surface activity for photocatalytic water splitting reaction. X-ray diffraction, X-ray photoelectron spectroscopy, PL emission spectra and UV-Vis spectra were used to detect the properties of as-prepared samples. Based on X-ray photoelectron spectroscopy analysis, boron is proposed to dope in the g-C3N4 lattice. Optical studies indicated that boron doped g-C3N4 exhibits enhanced and extended light absorbance in the visible-light region and a much lower intensity of PL emission spectra compared to pure g-C3N4. As a result, boron doped g-C3N4 shows activity of 10.2 times higher than the pristine g-C3N4 for photocatalytic hydrogen evolution. This work may provide a way to design efficient and mesoporous photocatalysts through post modification.
Abstract: In this experiment, a Z-scheme nitrogen-deficient graphite-phase carbon nitride (LaFeO3/CQDs-g-C3Nx) composite photocatalyst was prepared. The catalyst was characterized by X-ray diffraction (XRD), ultraviolet-visible diffuse reflection (UV-Vis DRS), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the introduction of nitrogen defects and CQDs enhanced the migration efficiency of photogenerated carriers. The photocatalytic degradation rate of LaFeO3/CQDs-g-C3Nx composites for rhodamine B (RhB) was 3.98 times higher than that of pure g-C3N4, and had good photocatalytic stability. It also showed good degradation of antibiotics and other organic pollutants.
Abstract: Mn-Fe/HAC carbon-based catalysts was prepared by equivalent-volume impregnation with coconut shell activated carbon as carrier and Mn(NO3)2 and Fe(NO3)3·9H2O as active components. NO reduction and Hg0 removal of carbon-based catalysts was carried out in a fixed-bed reactor. The effects of reaction temperature, gas hourly space velocity (GHSV) and flue gas components (O2, CO, Hg0 and SO2) on NO reduction and Hg0 removal were analyzed. The mechanisms of NO reduction and Hg0 removal over carbon-based catalysts were discussed based on the results of N2 adsorption-desorption, NH3-TPD, H2-TPR, Hg-TPD and transient response experiment. The obtained results indicate that NO reduction over carbon-based catalyst at low temperature can be enhanced significantly by Mn/Fe load, and Fe addition can increase the number of acid sites and the reducing capacity, which can improve NO reduction activity and further widen its temperature window on NO reduction. NO removal efficiency of 7Mn0.5Fe/HAC can reach 95% at 160−220 ℃, and Hg0 removal efficiency of carbon-based catalysts modified by Fe/Mn oxides is basically stable at 100% at 100−220 ℃. NO removal efficiency decreases and Hg0 removal efficiency is almost stable with increasing GHSV. A low NO removal efficiency of about 50% was obtained in absence of O2, however, high NO removal efficiency of more than 95% was present in the presence of more than 6% O2 in flue gas. Hg0 concentration has little effect on NO reduction of carbon-based catalyst modified by Mn/Fe, CO has a certain inhibitory effect, while high concentration SO2 has a significant inhibitory effect, and Mn/Fe co-loaded carbon-based catalyst improves tolerance to SO2. The NO removal efficiency of 7Mn0.5Fe/HAC can reach more than 80% at 180 ℃, 150 μL/L SO2. Carbon-based catalyst by loaded Mn/Fe for NO reduction follows E-R mechanism, i.e., NH3 first adsorbs on the active site, then reacts with gaseous NO, and finally reduces NO to N2. However, Hg0 removal follows L-H mechanism, i.e., Hg0 is first absorbed on the active site and forms absorbed Hg0, then reacts with reactive oxygen species and absorbed NO2 and SO2 to form HgO, Hg(NO3)2 and HgSO4, respectively.
Abstract: In this paper, the adsorption performance of NaHCO3 on SeO2 at 140−220 ℃ is investigated by adsorption experiments, and the total amount, valence and morphology of selenium in the adsorbed samples are resolved by series characterization, and the adsorption mechanism of NaHCO3 on SeO2 is discussed in depth by combining with density functional theory calculations. The results show that the adsorption performance of NaHCO3 on SeO2 increases with the increase of temperature, and the thermal decomposition reaction of NaHCO3 to Na2CO3 occurs simultaneously during the adsorption process, and the Na2CO3 produced after the thermal decomposition has stronger adsorption activity. The SeO2 adsorption process belongs to the chemical adsorption of Se atoms in SeO2 bonded to O atoms on the surface of Na2CO3, and the adsorption products are mainly selenite.
Abstract: In this work, a series of CuNH4Y-x zeolite adsorbents were prepared by ion exchange with different concentrations of CuCl2 and NH4Y zeolite. The effects of the valence and loading of Cu on the adsorption and separation of ethylene and ethane were investigated by fixed bed breakthrough adsorption experiment based on a series of characterization methods. The results of breakthrough adsorption experiments show that the ethylene adsorption capacity of Cu(I)NH4Y0.10 is significantly higher than that of Cu(II)NH4Y0.10, and the ethylene adsorption capacity of Cu(I)NH4Y series adsorbents increases first and then decreases with the increase of loading of Cu species. H2-TPR and HRTEM results show that monatomic Cu(I) species in the supercages of zeolite Y should be the effective active site when the loading amount of Cu is low. With the increase of Cu loading amount, the aggregation of Cu species results in the reduction of adsorption capacity of ethylene. The results of DFT calculation also confirm that the ethylene adsorption capacity of Cu(I)NH4Y adsorbent is significantly stronger than that of Cu(II)NH4Y adsorbent. These results can provide important theoretical basis and guidance for the development of high-efficiency Cu ion modified zeolite adsorbent for ethylene separation.
Abstract: Chain hydrocarbons cracking always occurs in pyrolysis/gasification. Among them, the reaction time of light chain hydrocarbons is short and they have many reaction paths, which make it difficult to accurately detect and analyze each evolution path by experiment. In this study, Gaussian and its related software were employed to predict the reaction sites and to study the chain cracking mechanism of C2 chain hydrocarbons (including ethane, ethylene and acetylene) under the action of H/OH/O radicals or H2O. According to the results, radicals can both attack the C and H atoms of ethane, while the C atoms of ethylene and acetylene are the main attack sites. Among the above radicals, OH radical is the best for unsaturated hydrocarbons cracking, while H radical is the best for saturated hydrocarbons, showing that the steam is conducive to the cracking of C2 chain hydrocarbons in actual process. In addition, comparing the optimal path of the reaction of ethylene or acetylene with OH radical, it can be found that CH2CH2OH radicals are easier to crack than CH2CHO radicals below 1200 K, while CH2CHO radicals are easier to crack above 1200 K, inferring the better response speed of aldehyde groups for temperature than alcohol groups.
Abstract: The structure-sensitive of Cu catalyst for furfural hydrogenation to furfuryl alcohol was explored by employing Cu(111) and Cu(211) model systems. Herein, the adsorption behavior of reactants and intermediates, and the possible reaction mechanism of furfuryl alcohol formation were investigated. For furfuryl alcohol formation, the preferred pathway is F-CHO + 2H→F-CH2O + H→F-CH2OH, in which the second H addition is the rate-determining step. Meanwhile, Cu(211) surface exhibits higher activity to furfuryl alcohol formation than that on Cu(111) surface. According to our analysis, the undercoordinated sites on the Cu(211) surface could facilitate H2 dissociation and stabilize the adsorbed furfural, thereby promoting the furfural hydrogenation and the furfuryl alcohol formation. This work provides a feasible approach for regulating the catalytic activity and selectivity in furfural conversion.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
