活化气氛对钼基合成醇催化剂的结构和性能的影响

Activated carbon supported Mo-based catalysts were prepared and reduced under different activation atmospheres, including pure H₂, syngas (H₂/CO=2/1), and pure CO. The catalysts structures were characterized by X-ray diffraction, X-ray absorption fine structure, and in situ diffuse reflectance infrared Fourier transform spectroscopy. The catalytic performance for the higher alcohol synthesis from syngas was tested. The pure H₂ treatment showed a high reduction capacity. The presence of a large amount of metallic Co⁰. and low valence state Mo^φ+ (0<φ<2) on the surface suggested a super activity for the CO dissociation and hydrogenation, which promoted hydrocarbons formation and reduced the alcohol selectivity. In contrast, the pure CO-reduced catalyst had a low reduction degree. The Mo and Co species at the catalyst mainly existed in the form of Mo⁴⁺ and Co²⁺. The syngas-reduced catalyst showed the highest activity and selectivity for the higher alcohols synthesis. We suggest that the syngas treatment had an appropriate reduction capacity that is between those of pure H₂ and pure CO and led to the coexistence of multivalent Co species as well as the enrichment of Mo^δ+ on the catalyst''s surface. The synergistic effects between these active species provided a better cooperativity and equilibrium between the CO dissociation, hydrogenation and CO insertion and thus contributed beneficially to the formation of higher alcohols.

Effects of Activation Atmospheres on Structure and Activity of Mo-based Catalyst for Synthesis of Higher Alcohols