HIGHER ALCOHOL SYNTHESIS FROM SYNGAS OVER K_2CO_3/MoS_2-BASED CATALYSTS: THE ROLE OF NICKEL PROMOTER

摘要

For ADM catalyst Ni showed an excellent enhancement on the activity especially C_(2+)OH selectivity. Contrary to the linear distributions for both alcohols and hydrocarbons over traditional ADM catalyst, the remarkable deviations of C_1OH and C_3H over Ni/ADM catalyst suggested a unique reaction mechanism different from the classical CO insertion mechanism. There were two types of Ni species in Ni/ADM catalyst, namely, separated pure phase of NiS_x and mixed phase of Ni-Mo-S. TPSR tests confirmed the strong ability of Ni promoter for the formation of C_(2+)OH, however, separated NiS_x phase showed the ability to produce only CH_4 and CO_2 via dissociation of CO. In Ni/ADM catalyst, the simultaneous presences of NiS_x phase and Ni-Mo-S phase resulted in a bi-functionality for C_(2+)OH formation, namely, NiS_x phase was favor to the formation of CH_x~* precursor due to the suppression of hydrogenation by the presence of K and S, while phase of Ni-Mo-S exerted a function of CO insertion in process of CO hydrogenation.