K-promoted Ni-Mo Catalysts Derived From Phyllosilicates For The Synthesis Of Higher Alcohols From Syngas

The resource conditions of China:"rich coal,less gas and lack oil",determine its energy structure is mainly relied on coal.But the extensive use of coal has diretly led to smog and ecological damage.Hence,it is imperative to develop clean energy.Catalytic conversion of syngas to higher alcohols?HAs?has drawn much attention owing to the potential use as environmentally friendly oil additive,clean fuels and chemical products and raw materals.Numerous works have been conducted for the synthesis of HAs.Mo-based catalyst has become a research hotspot due to its unique sulfur resistance and high C₂₊-OH selectivity in products.In this dissertation,a series of K-promoted Ni-Mo catalysts derived from phyllosilicates?K-?NiMo?Si-PS?are synthesized by an ammonia evaporation method,and their catalytic performance are systematically tested in the CO hydrogenation to higher alcohols.The optimal K0.5-(Ni₁Mo_0.25)Si-PS catalyst exhibits an excellent catalytic performance compared with the K0.5-(Ni₁Mo_0.25)Si-DP catalyst prepared by a deposition-precipitation method and the Ko.5Mo_0.25/Ni₁Si-PS catalyst prepared by the ammonia evaporation-impregnation method.The structure-performance relationship has been investigated by various characterizations.The results indicated that the C₂₊-OH selectivity showed a volcanic type variation with an increase in K content and Mo content.The catalyst with optimal performance was composed of K/Ni/Mo=0.5/1/0.25.The optimal reaction conditions for the syngas to HAs were determined as follows:reduction temperature:500 ?;reaction conditions:P = 3.0 MPa,T = 240 ?,GHSV = 3000 mL/?g-h?,and H2/CO =1.Under these conditions,the K0.5-?Ni1Mo0.25?Si-PS catalyst displayed the highest performance of 43.8%selectivity to total alcohol,65.4%selectivity to C₂₊-OH,and 6.6%CO conversion,whereas the catalysts K0.5-?Ni1Mo0.25?Si-DP and Ko.5Moo.25/NiSi-PS showed much worse activities.Further,the K0,5-?Ni1Mo0,25?Si-PS catalyst also demonstrated the superior long-term stability for 200 h.A series of characteristic studies revealed that the unique structure of phyllosilicate enhanced the metal-metal and metal-support interactions,which were in favor of the higher metal dispersion.A portion of the Ni and Mo species in the catalyst was in form of positive charge,which was favorable for the non-dissociative adsorption of CO and promoted CO insertion to form the alcohols.The rest portion of Ni and Mo species in the metallic state benefited the dissociative adsorption of CO and facilitated the growth of carbon chains.In addition,the introduction of alkali metal K ion to the catalysts strengthed the basicity of the catalysts,which was conducive to the non-dissociative adsorption of CO to form alcohols.