Pengchao Ren,Zhenzhou Zhang,Tingting Hu,Zhihui Fan,Shanshan Dang,Sifan Cheng,Weifeng Tu,Yi-Fan Han
Graphical The apparent rate coefficients for CH 3 OH synthesis from CO hydrogenation are a single-valued function of the CO 2 -to-CO ratio in the contacting gas phase, because this ratio determines the extent of surface oxidation of Ce 2 O 3 to CeO 2 , the relative abundance of surface Ce 3+ , and in turn the density of Cu 0 -Ce 3+ sites pair on the working Cu/CeO 2 catalyst. This study investigated the dynamic structure of a working Cu/CeO 2 catalyst and its catalytic consequences for CH 3 OH synthesis via CO hydrogenation by kinetics, high-precise chemical titration, and a series of in situ X-ray spectroscopies. We have revealed that the apparent rate coefficients for CH 3 OH synthesis from CO hydrogenation are a single-valued function of the CO 2 -to-CO ratio in the contacting gas phase. This ratio determines the extent of surface oxidation of Ce 2 O 3 to CeO 2 , the relative abundance of surface Ce 3+ and Ce 4+ sites, and in turn, the density of Cu 0 -Ce 3+ sites pair on the working Cu/CeO 2 catalyst, although the chemical state of Cu and elemental distribution of both Cu and Ce were insensitive to the ratio. The reactivity of CH 3 OH formation and the Cu 0 -Ce 3+ sites decrease monotonously with an increase in the CO 2 -to-CO ratio. The direct connection of the reactivity and the oxidant-to-reductant ratio appears to be general for heterogeneous catalysis, for which the oxidant oxidizes metal atoms. In contrast, the reductant scavenges surface oxygen atoms, thus dictating the density of surface sites and their thermodynamic activities.
Mingsheng Luo,Chenmeng Li,Qinglong Liu,Zhi Yang,Yatao Wang,Hongjuan Li
Direct hydrogenation of CO to alcohols through Fischer-Tropsch reaction process is taken great interest in recent years. In this study, a series of β-Mo 2 C/γ-Al 2 O 3 catalyst are prepared to investigate the influence of carbon and molybdenum precursor, calcination temperature, as well as the molar ratio of the carbon precursor to molybdenum precursor compounds on catalyst microstructures and the catalytic performance. The microstructure characteristics of the catalysts were examined with XRD, BET, ICP, SEM and CO-TPD. The performance test of the catalysts for syngas-to-alcohol was investigated in a fixed-bed reactor. Properly excessive amount of hexamethylenetetramine as carbon precursor calcined at a high temperature (≥700 ℃) favors the formation of high crystalline β-Mo 2 C on γ-Al 2 O 3 carrier. Catalysts with different amount of Mo were prepared to study the effect of active metal loading on microstructure and catalytic performance. The results show that the particle size of β-Mo 2 C and CO dissociation adsorption capacity, as well as the CO conversion increases with raised Mo loading. The selectivity of all higher alcohols reached the maximum when 25 % of Mo was loaded.
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