As one of the basic chemical raw materials in the chemical industry,propylene can be used to produce many downstream products of polypropylene,acrylonitrile,isopropanol,acetone and propylene oxide.As one of the propylene production methods,the propane dehydrogenation process has a single raw material and a high propylene yield,which is a good propylene production process.PtSn catalyst is widely used in propane dehydrogenation process because of its high activity and high selectivity.However,this kind of catalyst is expensive and the utilization rate of Pt is low,which restricts its use in the propane dehydrogenation process.In this paper,a low Pt loading PtSn catalyst was prepared by the carbonyl synthesis impregnation,and the catalyst preparation method,preparation conditions,influence of additives and propane dehydrogenation kinetics were studied.The effect of the preparation method and preparation conditions of the PtSn catalyst on the performance of the PtSn catalyst for propane dehydrogenation was investigated.When the Pt loading is 0.5wt%,the propane conversion rate of ice-phase reduction impregnation is slightly higher than that of carbonyl synthesis impregnation and carbonyl synthesis dropwise impregnation,but the stability is poor.The selectivity of propylene is always higher than that of ice-phase reduction impregnation and incipient wetness co-impregnation.When the Pt loading is 0.1wt%,the catalytic dehydrogenation activity of the PtSn catalyst prepared by carbonyl synthesis impregnation is much higher than that of the catalyst prepared by incipient wetness co-impregnation.The study on the preparation conditions of carbonyl synthesis impregnation showed that the PtSn catalyst with a Pt loading of 0.5wt%had the highest propane conversion and propylene yield,while The TOF value of the PtSn catalyst with Pt loading of 0.1wt%is about 5 times that of the PtSn catalyst with Pt loading of 0.5wt%;Pt/Sn molar ratio is 1:2;40℃is the best carbonyl synthesis temperature among the studied temperature;CH3COONa·3H2O/Pt4+=14 is an appropriate amount of sodium acetate.Among all the PtSn catalysts introduced with the second promoter,the PtSn catalyst with Ba has the highest propylene conversion rate and propylene yield,and also has good stability.The appropriate addition amount of Ba is 0.25wt%,and the better way of adding Ba is to add Ba during the carbonyl synthesis process.The effects of different reaction conditions on the catalytic dehydrogenation performance of PtSn catalysts were investigated.The current best operating conditions were reaction temperature of 590℃,propane mass space velocity 4 h-1,and C3H8:H2ratio 5:1.The PtSn catalyst with a Pt loading of 0.1wt%can maintain its catalytic dehydrogenation activity for a long time(1310 min)at a relatively low temperature(530℃),while it will have a shorter time(170 min)at a higher temperature(580℃).After that,it is largely inactivated.The kinetics of propane dehydrogenation on a PtSn catalyst with a Pt loading of 0.1wt%was studied,and first C–H cleavage in propane molecule is identified as the rate-determining step,and the activation energy was 90.09k J/mol. |