Abstract: The direct coal hydrogenation is a clean and efficient utilization of low rank coal for preparing high quality liquid fuels and chemicals. The isotope tracer technology has been widely used in the mechanism of direct coal hydrogenation. The isotope tracer technology is briefly introduced and the progress of its application in the reaction mechanism of coal hydrogenation liquefaction, coal hydropyrolysis and other direct coal hydrogenation is reviewed in this paper.
Abstract: Tar deposition is one of the obstructions which limits the large scale use of biomass gasification. Catalytic reforming is the most available and efficient technology for which the investigation of a high and stable catalyst is of great significance. Great attention has been paid to the char supported metal catalysts for their simple preparation, low cost and easy recovery of active metals. In this work, based on the origin and preparation of char-supported metal catalysts, we firstly reviewed its performance for the steam reforming of tar model compound, especially for the high activity and stability of highly-dispersed metal under low temperature. Additionally, we also reviewed biomass tar reforming over the char supported metal catalyst, compared their performance with traditionally tar reforming catalysts, and summarized the relevant catalytic reaction mechanism. It can be concluded that the catalysts have good application advantages and prospects. At first, char supports are favor to disperse active metal sites, thus the prepared nano catalysts are active for tar reforming into H2-rich syngas at mild conditions. Furthermore, energy and metal oxides can be obtained by burning spent catalysts. However, more researches are necessary to deeply reveal the mechanism for tar reforming and improve the stability of char supported metal catalysts.
Abstract: Low-rank coal is rarely used in the industry of carbonized briquette due to its poor cohesiveness. In order to replace lump coal and utilize low-rank pulverized coal as much as possible in a carbonized briquette process, washing oil residue (WOR) was used as an enhanced binder to enhance the bonding strength of resulted carbonized briquette. The effects of blending ratio and carbonization temperatures on binding strength were investigated, and moreover, a reasonable bonding mechanism was deduced. The results showed that the best crushing strength was obtained when the weight ratio of WOR and low-rank coal is 3∶7 at 800 °C, and its crushing strength of M25 (M25) can reach to 97%, while the thermoplastic properties of WOR is thought to be responsible for the obtained good crushing strength, where WOR can be softened and coated on the surface of coal particles during carbonization, and then a coal-binder interface can be formed, resulting in the loose inert coal particles can be combined and the strength of coke is improved significantly.
Abstract: Although alkali metal promoters have a considerable effect on the product distribution of CO2 hydrogenation over Fe-based catalysts, the mechanism of the active phase transformation is uncertain. The effects of Na modification and pretreatment atmosphere on phase evolution of Fe2O3 sample and the synergistic effect between iron oxides and carbides were investigated using in-situ X-ray diffraction ( in-situ XRD). The physiochemical properties of catalyst were characterized by H2-TPR and CO+H2-TPSR-MS. When the reducing environment is H2, Na promoter inhibited the reduction of Fe2O3. However, when the reducing atmosphere is syngas (CO/H2 = 1:2), a suitable amount of Na promoter decreased the reduction and activation temperatures, and increased the iron carbide concentration. The selectivity of light olefins increased from 0.3% to 20.2%, and CO2 conversion increased from 7.3% to 25.8% when syngas was used as the reducing gas compared to using H2 as the reducing gas. Compared with pure Fe2O3, the CH4 selectivity of Na modified Fe2O3 decreased from 43.2% to 14.9%, while the selectivity of C5+ increased from 7.8% to 37.0%, owing to the fact that the Fe5C2 content increased from 8.5% to 38.4%. The ratio of Fe3O4 to Fe5C2 in the catalyst could be effectively controlled by changing the reducing atmosphere and the amount of Na promoter, thereby improving the CO2 hydrogenation activity and target product selectivity.
Abstract: In this paper, ordered mesoporous HZSM-5 zeolite with different particle sizes (20, 30 and 40 nm) and the Si/Al ratio of 50 was successfully prepared by the hydrothermal method. The structure, morphology and surface acidity of the synthesized samples were characterized by XRD, SEM, TEM, N2 isothermal adsorption/desorption and Py-FTIR, and their catalytic activities were tested in the methanol to aromatics process on a fixed-bed reactor. The experimental results showed that the catalytic performance of ordered mesoporous HZSM-5 zeolite with different particle sizes was different for the methanol to aromatics reaction. The ordered mesoporous HZSM-5 zeolite of 20 nm exhibited excellent catalytic performance with the selectivity of light aromatics up to 60.0% and no significant deactivation of the catalyst after 51 h of continuous operation.
Abstract: In the process of direct synthesis of ethanol from syngas, rhodium-based catalysts continue becoming a hot topic because of their high selectivity for C2 oxygen-containing compounds such as ethanol. In this work, UiO-66 was used as a support to introduce the metal Ce4 + species into the [Zr6O4(OH)4] metal node of UiO-66-Zr to replace some of the metal Zr4 + species formation [Zr6−xCexO4(OH)4] metal nodes, so as to accurately study the problem of ethanol activity sites for the preparation of syngas. The characterization results of XRD, TG, Raman, BET, H2-TPR, XPS, and in-situ DRIFTS showed that with the introduction of metal Ce4 + species at the UiO-66 [Zr6O4(OH)4] node, -(Zr-O)-Rh-(O-Ce)-sites were formed on the catalyst, and -(Zr-O)-Rh-(O-Zr)-sites were formed on the Rh/UiO-66-Zr catalyst. Combined with the evaluation results of the catalytic reaction, the number of ethanol active sites was significantly increased. Because of the interaction between Rh species and -(O-Zr)-species is stronger than Rh species with -(O-Ce)- sites, the potential difference of this interaction favors the efficient transport of electrons. On the other hand, -(Zr-O)-Rh-(O-Ce)- can stabilize the key intermediates for the preparation of ethanol from syngas, which can promote the formation of ethanol.
Abstract: The control of copper species on the surface of CuY catalyst is the key to improve the performance of methanol oxidation carbonylation to dimethyl carbonate. In this work, a series of CuY catalysts with different copper loads were prepared by solution ion exchange method, and the N2-physisorption, XRD, TEM, H2-TPR, XPS, NH3-TPD and CH3OH-TPD were used to characterize the microstructure of the catalyst. The effects of Cu-ammonia solution concentration and activation temperature for structure and properties of CuY surface copper were investigated. The results indicated that although the porosity of the catalyst was reduced by increasing the concentration of solution, the amount of copper was significantly increased from 2.11% to 9.95%, and the high dispersion of copper species was maintained, with the particle size less than 4 nm. The high concentration of solution exchange reduced the weak acid sites on the surface and inhibited side reactions to improve the selectivity of DMC. The copper species of low loading catalysts were mainly ionic copper. Increasing the content of copper increased the content of ionic copper, but also significantly increases the amount of CuOx, which could rapidly improve the catalytic performance, methanol conversion and DMC yield reached 9.07% and 396.27 mg/(g·h), respectively. The activation at suitable temperature promoted the diffusion of copper species from the external surface to the internal pores, increasing the exchange of Cu species with NaY and weakening the adsorption strength of methanol, which was conducive to the improvement of catalytic performance. Compared with low loading catalysts, high loading catalysts could be activated to obtain more Cu+ and CuOx at low temperature, thus showing higher catalytic performance. The results of this work provided a theoretical basis for the design and preparation of high-performance CuY catalysts.
Abstract: Because there were much more oxygen-containing functional groups for low-rank coal, a large amount of CO and CO2 were produced during the pyrolysis process. Catalytic hydrogenation of CO or CO2 to light aromatics could be realized by supplying active hydrogen from methanol. Density functional theory (DFT) was used to investigate the mechanism of CO hydrogenation to aromatics via olefins intermediates over Fe/HZSM-5 catalyst under methanol atmosphere. The results showed that light olefins were formed by CO hydrogenation on Fe5C2 (510) surface. C−C bond coupling and chain propagation were achieved through multiple processes such as methylation and deprotonation. Methylation required a high activation energy among these processes. The aromatization of ${\rm{C}}^+_6 $ to benzene was carried out by reactions of hydrogen transfer, deprotonation and cyclization. Hydrogen transfer was the most difficult to happen. In the whole process of CO hydrogenation to aromatics, the energy barrier of methylation was the highest, which was the rate-determining step.
Abstract: Sorption-enhanced steam methane reforming achieves one-step production of high purity hydrogen by in-situ removal of CO2. However, the volume change of the adsorption component CaO in the composite catalyst during the adsorption and desorption of CO2 generally caused the structure collapse of the composite catalyst. At the same time, the active component Ni would also be embedded by the generated CaCO3, resulting in the decline of catalytic and adsorption performance and seriously affecting the purity of hydrogen production. How to prepare bifunctional composite catalyst with high stability is one of the key problems to be solved in the industrial application of this technology. In this work, CaO-Ca3Al2O6@Ni-SiO2 composite catalyst was prepared by the self-template approach using the cationic surfactant-assisted etching mechanism. In the experiment of hydrogen production by adsorption enhanced CH4/H2O reforming, the hydrogen production concentration over the composite catalyst reached 99.6%, and it still remained 97.3% after 10 cycles, which was closely related to the special structure of the prepared CaO-Ca3Al2O6@Ni-SiO2 composite catalyst. When the reaction was proceeded, the repeated expansion and contraction of CaO-Ca3Al2O6 volume in the composite catalyst was performed in the SiO2 cavity and would not cause the structure collapse of the composite catalyst. At the same time, the SiO2 coating on catalytic component Ni could prevent its agglomeration and deactivation during the decarburization and regeneration process. However, it was found that only part of the catalytic component Ni possessed a core-shell structure with Ni as the core and SiO2 as the shell, and there were some Ni directly loaded on the shell SiO2, leading to CH4 conversion dropping from 99.5% to 91.8% in 10 cycles.
Abstract: The steam cracking of Fischer-Tropsch refined wax from the coal-to-oil process for producing linear α-olefin (LAO) was carried out on a fixed bed reactor. The effects of feedstock composition, cracking temperature, contact time, water-to-wax ratio and cyclic process on the feed conversion and products distribution were investigated and optimized. The factors such as cracking temperature and contact time have significant influence on conversion and LAO yield, and cyclic process can further improve the LAO yield. However, excess high cracking temperature and longer contact time result in the second reactions, which are unfavorable for the LAO production. Under the suitable process conditions 53% of LAO yield are obtained.
Abstract: g-C3N4, ZIF-8 and ZIF-8/g-C3N4 composite photocatalysts with different mass ratios were prepared by thermal polymerization method and in-situ deposition method, respectively. The structural properties of prepared samples were characterized by using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS), etc. The results showed that the ZIF-8/g-C3N4 composite did not destroy the original crystal structure and morphology of ZIF-8 and g-C3N4, and ZIF-8 formed a heterojunction with g-C3N4. The BET specific surface area of ZIF-8/g-C3N4 was improved more than 30 times compared with g-C3N4. The results of photocatalytic oxidation of NO showed that 12.5%-ZIF-8/g-C3N4 exhibited the best removal efficiency of NO and no toxic intermediate NO2 production, and it had the most excellent photocatalytic activity with the nitric oxide removal efficiency of 55.1%. The mechanism study showed that the formed heterostructure not only inhibited the recombination of photogenerated charge carriers, but also promoted the absorption of visible light and the adsorption of reactant molecular NO due to the synergy between ZIF-8 and g-C3N4, thus improving the photocatalytic oxidation performance of NO.
Abstract: Hydrogen energy is recognized as the most potential energy carrier in the 21st century. Reversible solid oxide cells (RSOCs) have attracted more and more attention due to their efficient use of hydrogen for power generation and efficient hydrogen production from water electrolysis. Numerous studies have shown the polarization loss and decay of oxygen electrodes are the technical bottlenecks hindering RSOCs development. In this work, 10% mol Sc-doped La0.6Ca0.4Fe0.7Sc0.1Ni0.2O3−δ (LCFSN) material was prepared, and the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) of this material were studied in detail by half cell. It is found that ORR catalytic activity of LCFSN is better than the OER. The Ni-YSZ/YSZ/GDC/LCFSN full cells were assembled and their electrochemical performances in fuel cell mode (SOFC) and electrolysis cell mode (SOEC) were investigated in detail. The maximum power density can reach 1.471 W/cm2 at 800 ℃ with H2 as fuel. And the hydrogen production rate is as high as 627 mL/(cm2·h) at 750 ℃, 50 %H2O and 1.3 V. In addition, the cell has no obvious degradation in the 100 h stability test and has good stability. These results prove that LCFSN is a promising oxygen electrode material.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
