Preparation And Properties Of CoMn-Based Catalysts For Olefin Synthesis From Syngas

Low carbon olefins,represented by ethylene,propylene,and butene,are important basic chemical raw materials.With the development of China’s modern chemical industry,the demand for low carbon olefins is increasing day by day.The synthesis of low-carbon olefins from syngas through Fischer-Tropsch synthesis has received special attention due to its simple technical route and no intermediate reactions,and is also an important way to solve the shortage of domestic chemical raw materials.This experiment focuses on the preparation of cobalt based catalysts for olefins prepared by solvothermal method,coprecipitation and hydrothermal method.The purpose is to synthesize highly active catalysts with low methane selectivity,high olefin selectivity and low carbon dioxide selectivity.Preparation of Co Mn based catalysts using solvothermal method,and investigation of the effects of factors such as the molar ratio of ethylene glycol to Co（EG/Co）,the molar ratio of Co to Mn（Co/Mn）,and the solvothermal reaction temperature on the morphology,crystal structure,and FTO performance of Co Mn based catalysts.From the characterization results and experimental data obtained from the experiment,it can be concluded that the Co Mn based catalyst prepared at EG/Co=6,Co/Mn=1:2,and a solvothermal reaction temperature of 180℃has the best performance in synthesizing gas to olefins（FTO）.At this time,the conversion rate of CO in the prepared catalyst can reach11.1%,the selectivity of C_2-4olefins can reach 43.2%,the olefin to alkane ratio of C_2-4can reach 2.15,and the selectivity of methane can be reduced to 17.5%,CO₂selectivity is as low as 17.5%.Similarly,Co Mn based catalysts were prepared by coprecipitation method,and their FTO was investigated.The results showed that the Co Mn based catalyst prepared when Co/Mn=2,Co/Fe=8,precipitant（NH₄）₂CO₃,and precipitation method of coprecipitation+hydrothermal had the best FTO performance.At this time,the CO conversion of the prepared catalyst could reach 14.4%,the C_2-4olefin selectivity could reach 38.1%,the C_2-4olefin to alkane ratio could reach 2.78,and the methane selectivity could be reduced to 15.6%,and the CO₂selectivity could be as low as 5.6%.