Abstract: In order to improve the tar quality by decreasing the heavy tar content and ensuring high tar yield, in-situ catalytic upgrading of tar from the integrated process of coal pyrolysis coupled with steam reforming of methane was conducted over carbon (KD-9) based Ni catalyst. The results show that at 650 °C, the tar yield of CP-SRM over 5Ni/KD-9 is 24.4%, which is a little lower than that of without catalyst, while the light tar yield (i.e.,18.9%) is 1.4 times higher than that of without catalyst, and the content of C2, C3 and C4 alkyl used as a substitute for benzene significantly increases tar yields by 0.5, 0.6 and 4.0 times, respectively. The content of phenols and naphthalenes in tar also increases dramatically after upgrading. Isotope tracer approach combined with the mass spectra of typical components was employed in exploring the mechanism of the upgrading process. The results show that 5Ni/KD-9 catalyzes coal tar cracking and SRM at the same time. Small free radicals such as ·CHx, ·H and ·OH generated by SRM can combine with free radicals from tar cracking, thus avoiding excessive cracking of tar.
Abstract: In the present work, the effects of iron-based catalysts from coal liquefaction on the coal structure and gasification reactivity were studied using the Hami raw coal and demineralized coal. The surface morphology, element distribution and mesoporous characteristics of coal char were investigated by SEM-EDS and physical adsorption analyzer. The gasification reactivity was performed in a thermogravimetric analyzer. The gasification kinetics was studied through the model-fitting and model-free methods. The results showed that the demineralization and catalyst loading had more obvious effect on the surface attachments than the carbon matrix. The coal char with catalyst loading had significant larger specific surface area (SSA). The reactivity improvement by iron-based catalyst was attributed to the enrichment of Fe and AAEMS and increase of SSA for coal char. More pronounced relative catalytic activity was observed for the catalytic gasification of demineralized coal char, and its activity was not sensitive to the change of heating rate and carbon conversion. The gasification characteristics difference decreased with the increase of heating rate. The iron-based catalyst increased the pre-exponential factor A for the demineralized coal char gasification, and reduced the activation energy Ea for the raw coal char gasification. Under the non-isothermal conditions, the Ea decreased with conversion. According to fitting performance and kinetic compensation effect, the random pore model was the best model to describe gasification, especially for the (catalytic) gasification of the demineralized coal char.
Abstract: The oxy-fuel co-combustion of coal gangue and semicoke and the pollutants emission characteristics were studied by thermogravimetric analyzer and tube furnace experiments. The effects of semicoke blending ratios, O2 concentration and temperature were investigated. The results showed that the combustion performance of blended fuel could be improved with the addition of semicoke and the increase of O2 concentration. The maximum ignition and burnout index were obtained when semicoke blending ratio was 75%. The xCO and ${x_{{\rm{S}}{{\rm{O}}_{\rm{2}}}}} $ gradually decreased with the increase of semicoke blending ratios. As the increase of temperature, the xCO decreased, ${x_{{\rm{S}}{{\rm{O}}_{\rm{2}}}}} $ increased while xNO firstly increased then decreased or slowly grew. The NO emission could be reduced with the addition of semicoke when the temperature was 900 ℃. However, it would aggravate NO emission at other temperatures. With the increase of O2 concentration, the xCO decreased, xNO increased while ${x_{{\rm{S}}{{\rm{O}}_{\rm{2}}}}} $ firstly decreased and then increased. The minimum ${x_{{\rm{S}}{{\rm{O}}_{\rm{2}}}}} $ was obtained when O2 concentration was 20%.
Abstract: The batch distillation experiments of bio-oil model compounds were carried out in a pilot rectification column. The distilled fractions of bio-oil model compounds at atmospheric pressure and vacuum distillation were compared by changing the vacuum degree in the system, and the variations of each component in the fractions were analyzed and summarized. The results show that the total distillate rate of bio-oil model compounds increases, the coking rate decreases, the moisture is more likely to be evaporated, the initial distillation temperature of organics in the fraction decreases, and the distillate rate increases with the rise in the vacuum degree of the system. Therefore, increasing the vacuum degrees can effectively separate the components of the bio-oil model compounds and reduce the energy loss. When the vacuum degree is −0.08 MPa, the distillation effect of the bio-oil model compounds is optimum. The distillate rate of acetic acid and furfural can reach 99.50% and 65.88%, respectively, and the distillate rates of phenol and guaiacol are both over 25%.
Abstract: The carbonylation reaction of dimethyl ether is an important carbon addition reaction with directed insertion of carbon monoxide into dimethyl ether molecule, which is of great significance in industrial production. In recent years, it has been found that inexpensive mordenite has higher activity and very excellent carbonylation product selectivity for catalyzing the carbonylation reaction of dimethyl ether, hence widely studied. This review surveys researches on mordenite catalyzed carbonylation of dimethyl ether, introduces the mechanism of carbonylation reaction, and summarizes the various methods of controlling the acidic sites inside mordenite and their effects on the carbonylation reaction.
Abstract: Large amounts of methane are emitted from coal mining and industrial applications such as gas turbines or mobile sources which also have the characteristics of low concentration and huge volume, and the traditional high temperature incineration method leads to secondary pollution. Therefore, the efficient conversion of methane at low temperature has become an urgent problem. From the perspectives of energy utilization and environmental protection, the catalytic combustion technology is a valid measure to achieve efficient and clear utilization of methane. In this paper, a systematic review of recent research advances in catalytic mechanisms and catalysts is presented. Firstly, the mechanism of methane oxidation is summarized and outlined based on experiments and theories, with emphasis on the "Two-term" model. Secondly, the performance advantages and disadvantages of each catalyst and modification techniques are systematically introduced. Lastly, the perspectives for the future research are proposed, for instance, the use of structural optimization methods to expose more active sites or generate multi-component synergistic catalytic effects, the use of non-noble metal doping and other enhancements to prepare highly efficient catalysts, and the further co-excitation of catalytic performance by multiple external fields. In addition, the improvement of various catalytic mechanisms themselves and the development of new mechanism descriptors are also important directions for the future research.
Abstract: With the rapid development of modern society, the demand for energy is increasing. Currently, fossil fuel is still the dominant energy in developing countries. Moreover, the greenhouse effect and environmental problems result from excessive emission of carbon dioxide by the combustion of fossil resources have arouse worldwide concern. Therefore, utilization of carbon dioxide has attracted much attention. Among the paths, the preparation of polymers from carbon dioxide could not only realize the carbon fixation, but also provide a new approach for the green production of polymer. This review aims to summarize the progress on the synthesis of polyurethane from carbon dioxide, which mainly focuses on its physical and chemical applications in materials and the preparation technologies.
Abstract: H-[B,Al]-ZSM-5 zeolites were synthesized with glucose as assistant template to catalyze methanol converting toward propylene. The superior catalytic performance in terms of the propylene selectivity and the activity longevity was related to high ratio of weak acid to strong acid for favorable production of propylene and to high mesoporosity for improved diffusion of reactants and prevention from fast coking. More framework Al siting in the straight or sinusoidal channels of the MFI zeolite could also enhance the propylene/ethylene ratio due to the promotional effect on propylene formation. Low weak acid density was conducive to the production of high propylene/ethylene ratio. With the B/Al ratio of 2 and the (Al2+B2)/Si ratio of 0.01, HZ5-G-2B was applied in the methanol to propylene reaction at CH3OH/H2O (1∶1.2) WHSV of 1.8 h−1 and 480 °C. Propylene selectivity of 51.6%, the ${\rm{C}}_{{2-4}}^ {=} $ selectivity of 83.7% and complete conversion of methanol were achieved. The propylene/ethylene ratio was 2. The catalytic activity kept stable for 580 h.
Abstract: Different sizes of γ-Fe2O3 nanoparticles (4−19 nm) were prepared by thermal decomposition of iron oleate and carburized in three different gas atmosphere of 5%CO/He, 5%CO/10%H2/He and 5%CO/20%H2/He at 350 ℃. The carburization process and phase transformation of γ-Fe2O3 nanoparticles were investigated by in situ XRD, Raman spectroscopy, CO-TPR and TEM. The results showed that χ-Fe5C2 and θ-Fe3C phases with a stable ratio were formed after carburization. The time to complete carburization was shortened for increasing sizes of γ-Fe2O3 particles under the same carburization atmosphere. While the smaller γ-Fe2O3 particles showed more residual carbon on the surface, which could inhibit the carburization process. The relative content of θ-Fe3C increased with the increase of the size of γ-Fe2O3 nanoparticles. For γ-Fe2O3 nanoparticles with the same sizes, the time to complete carburization in different atmospheres was firstly shortened and then slightly lengthened with the increase of H2 partial pressure, while the relative content of θ-Fe3C increased with the increase of H2 partial pressure. By adjusting the particle size of γ-Fe2O3 and the carburization atmosphere, the mixed phases of χ-Fe5C2 and θ-Fe3C can be optimized.
Abstract: The dehydrogenation performance of vanadyl catalysts was closely related to the form of surface vanadyl species. To enhance the vanadium dispersion, phosphorus was adopted to modify V-MCM-41 catalysts by using organic vanadium and phosphorus precursors. The influence of phosphorus introduction to the mesoporous structure and vanadyl species were investigated by various characterization techniques. The results showed that the catalysts could maintain ordered hexagonal mesoporous structures though the specific surface area slowly decreased along with the increase of phosphorus content. Both the reducibility and dispersion of the surface vanadyl species were improved. The proportion of polymerized vanadyl species obviously decreased due to the presence of phosphorus species. The propane dehydrogenation reaction results showed that both the catalytic performance and the catalyst stability were improved. Both the maximum surface vanadyl site density and optimum propane dehydrogenation performance were obtained over the sample with Si/P molar ratio of 30.
Abstract: Using 1,3,5-triisopropylbenzene (1,3,5-TIPB) and n-octane as the catalytic cracking feedstocks and 1-hexene as the oligomerization feedstock, the coupling mechanism of catalytic cracking reaction and olefin oligomerization reaction over the synthesized hierarchical ZSM-5 zeolite catalyst was evaluated. The results of catalytic cracking reaction of model compounds showed that the catalytic cracking performance of molecules with different sizes was inhibited on the synthesized hierarchical ZSM-5 zeolite. The cracking activity of 1,3,5-TIPB decreased, and the initial activity of n-octane reduced from 70% to 20%. However, enhanced 1-hexene oligomerization activity was observed over the hierarchical ZSM-5 zeolite, with dimer as the main product. The reduction of the strong acid sites in the zeolite can inhibit the catalytic cracking reaction and promote the oligomerization of C6 olefin into dimer and trimer (ideal components of jet fuel). Therefore, the designing of the catalyst from the perspective of inhibiting the activity of catalytic cracking can effectively improve the oligomerization performance of the catalyst.
Abstract: Recently, a new carbon nitride (C3N5) photocatalyst has attracted much attention due to its excellent light harvesting and unique 2D structure. However, high recombination rates of electron-hole pairs of bulk C3N5 serious affect the photocatalytic performance. Herein, nickel oxide (NiO) modified C3N5p-n junctions photocatalyst was synthesized by a facile hydrothermal method. Results indicated that the 9-Ni/C3N5 nanosheet photocatalyst showed excellent hydrogen production efficiency under visible light. The hydrogen production rate reached 357 μmol/(g·h), which was 107-fold higher than that of pristine C3N5. The high catalytic performace was attributed to the 9-Ni/C3N5p-n junctions which could efficiently promote photogenerated electron-hole pair separation and thus promote the hydrogen evolution reaction.
Abstract: BiOBr, Bi3O4Br and Bi4O5Br2 were prepared by hydrothermal and solvothermal methods. Their structural composition, surface morphology, chemical states and optical properties were characterized by XRD, SEM, XPS and UV-vis. The band structure and density of states of the photocatalysts were calculated by density functional theory (DFT). The photocatalytic activity was evaluated by degradation of RhB. The results show that band gap and the position of conduction band is affected by Bi content. The Bi4O5Br2 photocatalyst can completely degrade RhB in 50 min. Radical-trapping experiments proves that ·$ {\rm{O}}_2^- $ is the main active species in photocatalytic degradation of RhB.
Supervisor：Chinese Academy of Sciences
Sponsors by：Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences Chinese Chemical Society
