Contrallable Preparation Of Molybdenum-based Catalysts And Their Performance Of Catalytic Syngas To Higher Alcohols

Syngas is a mixed gas composed of CO and H₂and almost all organic resources（such as biomass,coal,oil and natural gas）can be easily converted into syngas through gasification or reforming.After the industrialization of syngas conversion into methanol,the technology of using syngas as the raw material to prepare higher alcohols has received widespread attention.In general,higher alcohol refers to a mixture of C1-C5 alcohols.which has a wide range of applications,such as being used as high-quality fuels and the intermediates or raw materials of pharmaceuticals,cosmetics,etc.In particular,rational design and preparation of high-efficiency catalysts play the crucial role in conversion of syngas to higher alcohols.Molybdenum carbide has a Pt-like d-electron structure,and exhibits catalytic properties similar to noble metals in reactions such as catalytic hydrogenation,catalytic reforming,and hydrocarbon isomerization.Therefore,this paper employed metal organic framework materials and lignin as carbon sources to prepare supported molybdenum carbide catalysts by the"solid-solid"method,and investigated the relationship between the properties and structure of the catalysts as well as their catalytic performance towards conversion of syngas into higher alcohols.The research results provide a reference for the development of high-efficiency catalysts for syngas conversion into higher alcohol.The main findings are summarized as follows:1.The Ni-based metal organic framework（Ni-MOF）was prepared by hydrothermal method,which was used as the carbon source.The catalyst precursor was prepared by impregnating Mo salt on Ni-MOF by the impregnation method.Then,the influence of additives and adding ways of additives,the content of molybdenum,and the calcination atmosphere on the performance of the catalyst were investigated.After preparing molybdenum carbide in a syngas environment at 700°C,the K promoter was impregnated on the molybdenum carbide with a Mo:K molar ratio of5:1 and a highly active catalyst(₃₀Mo₂C@Ni-MOFs_sK_j)was obtained with a Mo content of 30%.The catalyst ₃₀Mo₂C@Ni-MOFs_sK_jshowed excellent performance under the conditions of 380℃,7 MPa,and a space velocity of 5000 h^-1,by which the CO conversion rate,total alcohol selectivity,C₂₊alcohol selectivity and space-time yield reached 45.6%,20.0%,86.39%and 0.340 g/g_cat/h,respectively.According to the activity testing results,the optimal reaction conditions were explored and the relevant catalysts were characterized in detail.Finally,the catalytic performance of the catalyst was linked with the physicochemical performance,and its structure-activity relationship was subjected into in-depth investigation.2.Using lignin and lignin carbon obtained after calcination as the carbon source,the Mo salt was impregnated on the carrier by the impregnation method,and the influence of the carbon source,adding ways of additives,the carbonization method on the catalytic performance were investigated.Using the lignin carbon pickled with nitric acid as the carbon source,molybdenum carbide is prepared by high-temperature carbothermal reduction,followed by impregnating the K and Ni additives on molybdenum carbide.After repeated carbonization,the molybdenum carbide catalyst(₂₀Mo₂CKNi@mzsx)with excellent catalytic performance was obtained.It showed the best performance under the conditions of 380℃,7 MPa,and a space velocity of 7000h^-1,by which the CO conversion rate,total alcohol selectivity,C₂₊alcohol selectivity and space-time yield reached 34.4%,50.4%,82.9%and 0.455 g/g_cat/h,respectively.Finally,the surface structure and physiochemical properties of the catalyst were characterized and analyzed.Combined with the testing results of catalyst activity,the reaction mechanism of syngas conversion into higher alcohols by the catalyst was elucidated.