Studies On The Performance Of Mesoporous Foam Silicon Supported Iron Catalysts For Fischer-Tropsch Synthesis

With the development of global economy,fossil energy was consumed and will be run out in near future.In order to deal with the energy crisis caused by excessive consumption,the sustainable clean energy should be urgently developed.China is an oil shortage country and has relatively abundant carbon-bearing resources such as coal,natural gas and biomass.Conversion of carbon-containing resources into sustainable clean energy and related high value-added chemicals via Fischer-Tropsch synthesis?FTS?is a feasible way to guarantee energy security.Development of FTS catalysts with high activity,high selectivity and good stability is of importance.In this paper,mesoporous silicon foams?MCFs?supported highly dispersed iron-based catalysts were prepared by impregnation method.The effect of 3types with impregnating solvents,contents of Mn promoter and modification of support by Cr,Mo,W?group VI elements?on FTS performance of iron-based catalyst were investigated.The major research contents and conclusions are as following:?1?Mixed solution with deionized water and ethyl alcohol,acetic acid,citric acid or glucose were used as impregnation solvents,to impregnate iron nitrate nonahydrate on MCFs.Due to the difference of complexing ability for iron ion in different organic component,the dispersion of iron species on support were significantly different.Ethyl alcohol and acetic acid were able to promote dispersion of iron species on support and the catalysts could be reduced during calcinations at nitrogen with the glucose and citric acid.But,because of strong complexing ability between iron species and glucose or citric acid,which resulted the suppression of reduction and carbonization for catalysts that decreased catalytic activity.Small iron particles were easily formed when ethyl alcohol and acetic acid were used as the impregnation solvents that could promote the reduction and carbonization of iron species.Small size iron particles could form more Fe₂C phase and improved the catalytic performance.?2?The catalysts with different atom ratios of Fe:Mn were prepared by using co-impregnation method with ethanol-deionized water mixed solvent.The results showed that the iron dispersion was decreased with the increase of Mn content,the interaction between iron and support was strengthened,iron reducibility was also decreased,and thus FTS activity was diminished.But Mn promoter could contribute to the formation of long-chain hydrocarbon.?3?The group VI elements such as Cr,Mo,W were applied to modify MCFs support,then the FTS iron catalysts were prepared by using modified MCFs supports,studying the effect of Cr,Mo,W in FTS iron catalysts.The results showed that Cr2O3and MoO₃ promoted reduction and carbonization of catalysts and then the cooperation between catalysts and Cr₂O₃ or MoO₃ could strengthen the catalytic performance.Furthermore,Cr₂O₃ had stronger cooperation with iron carbide than MoO₃ and WO₃,and alkene could easily form for Cr₂O₃.MoO₃ and WO₃ had higher C₅₊selectivity and C₂-C₄ alkene selectivity at 290^°C.