It is a big challenge to improve the stability and anti-coking abilities of catalyst in high temperature CO methanation reaction. To address the issue, SiC was chose as the support, and Ce was used as a promoter to prepare supported Ni catalysts for CO methanation. A long-term high temperature stability evaluation experiment was carried out at 600 °C for 100 h in comparison with Ni/Al 2 O 3 catalyst. The catalysts were characterized by a combination of characterization techniques for understanding the catalytic performance and carbon deposition behaviors in CO methanation. The life test result indicates that, compared to Ni/Al 2 O 3 , Ni/SiC is thermally stable and highly resistant to carbon deposition . Improved cataytic activity and stability was further reached by introduce of Ce promoter into Ni/SiC, which can be attributed to the enhanced interaction between Ni and SiC and improved dispersion of Ni active species.
The effective and selective conversion of cellulose to valuable fuels and chemicals is highly attractive. In this paper, we prepared a catalyst with the adjacent surface Cu° and oxygen-deficient WO x (2 < x < 3) species by reduction of CuWO 4 precursor, and such catalyst coupled with Ni/activated carbon (AC) attained high yield (71 wt%) and good cycling performances in catalyzing one-step hydrothermal conversion of cellulose to ethylene glycol (EG), highly superior to the performances on physically mixed Ni/C, Cu/C and WO 3 . The increased Cu doping amounts led to a higher ratio of the lower valence state W (V or IV) to the high valence W(VI) as indicated by XPS, XRD, and TPR-H 2 analyses. The oxygen vacancies on the hydrogen-reduced CuWO 4 sample dramatically increased, probably due to the benefits from the substantial dissociated H• on the neighboring Cu° center. The EG yields from cellulose are shown to be proportional to the concentrations of oxygen vacancies on WO x , which catalyzes the important elementary retro-aldol step reaction via adsorbing C 6 sugar intermediates in a specific way. It is inferred that Cu introduction is mainly used to create more oxygen vacancies on the WO x surface that helps adsorbing oxygenates, while Ni fast hydrogenates of hydroxyacetaldehyde to EG and avoids coking, constructing a multi-functional synergistic catalytic process from converting of cellulose to EG in the high-temperature water
J. He,X.-H. Lu,Y. Shen,R. Jing,R.-F. Nie,D. Zhou,Q.-H. Xia
Cyclohexanol is an excellent starting material for fuel production, but direct selective hydrogenation of phenol to cyclohexanol under mild conditions is a challenge. Herein we report a catalyst made of Ni nanoparticles supported on high-surface silica, which is highly active for selective formation of cyclohexanol under 1.0 Mpa pressure of hydrogen in aqueous medium without additives. Conversion of 100 mol% and selectivity up to 100% are achieved within 4 h and 1.0 MPa H 2 . Some factors such as the type of the source of silica, the loading of Ni, the reaction temperature and time, the H 2 pressure play important roles in controlling the selective hydrogenation. The generality of the 10%Ni/SiO 2 -1 catalyst for this reaction is demonstrated by selective hydrogenation of other hydroxylated aromatic compounds as well.
Chemical looping redox cycle of oxygen storage materials offers a versatile platform to convert methane to value-added products in a clean and efficient manner. However, the highly dynamic nature of the oxygen diffusion process restrains the selective formation of the target products over a long reaction period. In this work, we show the oxygen storage materials-comprising of iron oxides and zirconium oxide support, with the nickel catalyst controllably deposited—that significantly enhanced the syngas selectivity. Mechanistic study indicated the oxygen releasing rate can be well controlled within a long reaction period by the specific spatial structure, demonstrating a new strategy to tune the oxygen diffusion in chemical looping process. Through the observed spatial effects, this work can be also extended to develop more oxygen storage materials for the other chemical looping applications, e.g. methane reforming, methane oxidative coupling, ethane oxidative dehydrogenation, etc .
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