Study Of Preparation And Catalytic Performance Of Modified Cu-Fe Based Catalysts For Synthesis Of Lower Alcohols From Syngas

Coal gives the first place to chinese energy structure,and the technology of synthesizing syngas from coal has been industrialized application.The lower alcohols synthesized by syngas have a very broad application prospect,which can be used as raw material directly used as chemical products,also can be used as chemical raw materials or high-quality additives for gasoline.Therefore,it is meaningful to research the preparation of low carbon alcohols from coal based syngas for the rational exploitation and utilization of coal resources in China.The effect of promoters,preparation methods and supports on the catalytic property of Cu-Fe based catalyst for mixed alcohol synthesis by synthetic gas were studied.The structure and surface properties of the catalysts were characterized by nitrogen adsorption,XRD,H₂-TPR,CO-TPD,SEM and XPS,and their catalytic performances of the catalysts for preparation of lower alcohols by synthetic gas were investigated using a continuous flow fixed bed reactor.Then based on CuFeNiCr/CNTs catalyst,the effect of reaction temperature and reaction pressure for synthesis of lower alcohols from syngas were studied.The addition of promoters significantly increased the dispersion of the components in the catalyst,which resulted in the increase of the specific surface area of the catalysts,provided more active sites for the synthesis reaction,and facilitated the synthesis of low carbon alcohols.The catalysts modified by Ni or Ce had higher CO conversion,however,the proportion of C₂₊OH on CuFeNi catalyst?modified by Ni?accounted for the largest,indicating that the addition of Ni was more conducive to the growth of the carbon chain,while Cr modified Cu-Fe catalyst inhibited the formation of hydrocarbons,alcohol selectivity was higher,but the CO was conversion lowest.Compared with the single promoter,the addition of Ni-Ce or Ni-Cr to the catalyst improved the catalytic activity.Furthermore,the the content of methanol in the liquid products decreased significantly,and converted to more C₂₊OH,especially the ratio of C₂₊OH to CH₃OH of CuFeNiCr catalyst reached 1.82.A series of CuFeNiCr catalyst were prepared by the novel solid state impregnation method,ultrasonic-impregnation method,cis-plus coprecipitation method and parallel flow coprecipitation method,and their catalytic performances for CO hydrogenation to lower alcohols were investigated.The results indicated that:compared with the other three methods,the catalyst prepared by ultrasonic-impregnation method had the largest specific surface area,the best dispersion of active components and CO conversion was up to 43.2%,the selectivity of alcohols and the distribution ratio of higher alcohols were higher.Besides,After the catalytic reduction,the crystalline phase of Cu and FexC is formed on the surface,which is the active site for the synthesis of low carbon alcohols.The addition of supporters Cu-Fe based catalysts could increase the s pecific surface area obviously,promote the dispersion and reduction of the active components and improve the adsorptive capacity of the catalyst on CO.Although the BET surface area of the CuFeNiCr/AC catalyst was 311.58m²·g^-1,the selectivity of C₂₊OH was lower.The CO conversion of CuFeNiCr/ATP catalyst was lowest,and ethanol was the mainly product.In comparison,The CuFeNiCr/CNTs catalyst had the higher BET surface area,the strong capability for CO adsorption and the active components CuO could be easily reduced;Moreover,The catalyst possessed the higher CO conversion,the highest selectivity of higher alcohols?46.0%?,lowest selectivity of hydrocarbons and CO₂,and the content of C₂₊OH was maximum in the liquid product.Based on CuFeNiCr/CNTs catalyst,the effect of reaction temperature and reaction pressure for synthesis of lower alcohols from syngas were studied.When the reaction temperature was 340?and the reaction pressure was 6 MPa at the synthesis of lower alcohols with CuFeNiCr/CNTs catalyst with GHSV=5000 h^-11 and H₂/CO=2,which was beneficial to the formation of C₂₊OH,especially,the selectivity of propanol was higher.