Modified Of Cobalt-molybdenum Bimetallic Nitride Catalyst And Its Application In CO Hydrogenation To Higher Alcohol

Syngas to higher alcohol is an important means to create clean and green energy,which is of great significance in dealing with the crisis of non-renewable energy and improving environmental problems in China.At present,the development and research of catalyst system is the focus in the field of energy catalysis.Although the novel bimetallic Co₃Mo₃N catalyst has little research in this field,it has great research value because of its adjustable dual active sites.In this thesis,the catalyst system was optimized from cation doping modification,building interface interaction modification,anion partial substitution modification and carrier loading modification aspects to achieve the purpose of improving the catalytic activity of the catalyst.（1）Co₃Mo₃N catalyst was optimized and modified by introducing rare earth additives La,Ce and Y.The changes of catalysts before and after doping promoters were analyzed by XRD,SEM,TEM,XPS and CO-TPD.The catalytic performance of the catalysts for syngas to higher alcohols was investigated.The results showed that the addition of promoter improved the dispersion of the catalyst,adjusted and balanced the content of the double active sites of the catalyst,promoted the non-dissociation ability of the catalyst.Under the optimal ratio of rare earth and potassium promoters,La promoter was the best.At K/Mo=0.9,T=300℃,the total alcohol,methanol and C₂₊OH selectivity of 50.4%,10.6%and 89.4%,respectively.Space time yield to total alcohols of 173mg/g/h.（2）Co₃Mo₃N/MoS₂ catalysts with different proportions were prepared by physical mixing of Co₃Mo₃N and MoS₂ tandem catalysts.The catalytic performance of the catalysts for syngas to higher alcohols was investigated.The results show that the adding of MoS₂ catalyst increases the content of double activity sites(Mo⁴⁺and Co⁰)of Co₃Mo₃N catalyst,and improves the non-dissociative adsorption capacity to CO.At Co₃Mo₃N/MoS₂=3:1、T=350℃,the CO conversion,total alcohol selectivity,ethanol selectivity,C₂₊alcohol selectivity and space time yield to total alcohols of 33.0%,53.6%,32.0%,72.9%,255.2mg/g/h,respectively.Compared with pure Co₃Mo₃N catalyst,the catalytic performance was improved obviously.In addition,considering the contact degree of the active site of the catalyst,the MoS₂ catalyst was grown on the Co₃Mo₃N catalyst by the in-situ method to prepare the complex catalyst.The results showed that the total alcohol selectivity was significantly improved（at T=350℃,reached 63.6%）.（3）The N-S co-doped Co-Mo-based catalyst was prepared by sulfurizing the Co3Mo3N catalyst.The results showed that the adding of heteroatoms changed the chemical environment of the catalyst,and further improved the catalytic performance by adjusting the performance of the dual active sites.At Co₃Mo₃N/S=1/4、T=350℃,the total alcohol selectivity and ethanol selectivity of the co-doped catalyst was 64.1%and 43.2%,respectively.However pure Co₃Mo₃N was 39.9%and 36.0%,respectively.（4）In order to expose more active sites,using sol-gel method to prepare small particles CA-Co₃Mo₃N catalyst,and its performance was analyzed and evaluated.The results showed that the catalyst with smaller particle size had higher dispersion.At T=350℃,the CO conversion can reach 80.4%,the selectivity of C₂₊alcohol and the space-time yield of total alcohol are 89.2%and 469.8mg/g/h,respectively.And then we add S to partially replace N.The results showed that at T=350℃,the selectivity of total alcohol was significantly improved（72.4%）,but the CO conversion was greatly reduced.The supported CA-Co₃Mo₃N/kaolin catalyst was prepared by the impregnation method,and the influence of the supporting on the catalytic performance was explored.It was found that at T=300℃,the total alcohol selectivity of the CA-Co₃Mo₃N/kaolin catalyst was increased to 81.2%,but the CO conversion was greatly reduced（less than 1%）.