Reaction stability and structure studies of sulfided K-MoO3/gamma-Al2O3 catalyst for the synthesis of mixed alcohols

A sulfided K-MoO3/gamma-Al2O3 catalyst with excellent activity for the synthesis of mixed alcohols was prepared. By a durability test of 1300 h, it was found that the initial reaction activity over the catalyst is quite low and the activity increases obviously with reaction time in the first 15 h, then the increase of the activity becomes rather slow and the activity curve becomes horizontal after reaction for 200 h. Tn the whole process of 1300 h reaction the activity for alcohol synthesis did not show any sign of decrease. So the catalyst possesses excellent reaction stability, According to the structural. studies, the major component of the fresh sulfided sample is an MoS2-like structure, accompanied by a small amount of Mo-S species with different valences of Mo and S atoms. In the catalytic reaction process, some of the sulphur species including that coordinated with Mo atoms is lost, The Mo-S and Mo-Mo coordination number for the post-reaction sample decreases notably compared to that for the fresh sulfided sample; and some highly coordinated unsaturated sites are formed, which may be favourable for the formation of catalytic active centers for the synthesis of mixed alcohols. The existence of these coordinated unsaturated sites may be the reason for the fact that a part of the Mo4+ species is oxidized and converted to Mo5+ and Mo6+ species while contacting with air in the short time for structural measurements.