Modification Of Pt Catalyst For Propane Dehydrogenation

Propylene is an important basis of numerous chemical products in the field of low carbon olefin.With the increasing demand of propylene and the exploitation of shale gas,direct dehydrogenation of propane to propylene as an alternative way has drawn great attention.The Pt based catalyst is the most widely used catalyst in the reaction of propane dehydrogenation.Industrial propane dehydrogenation catalysts generally suffer from low catalytic stability due to coke deposition and metal sintering.At present,the way of improving the stability of the catalyst is doping Sn promoters.The presence of Sn can supperss metal sintering and promote the diffusion of coke species from the metal surface to the support,thus improving the stability of the catalyst.However,it is difficult to ensure metal ion accurate coordination and co-location on the surface of the support by impregnation method.If prepare the highly-dispersed Pt-Sn cluster with subnanmetre size and metal character for minimizing the flat site of platinum,the resultant catalyst should present not only high activity,but also an improved stability.Herein,we have starting from the innovation of active component precursor and additive.Firstly,the binary Pt-Sn metal cluster was prepared dy SnCl₂ inserting Pt-Cl bond reaction process using quaternary ammonium salt as stabilizer.The hydrolysis of SnCl₂ is inhibited by multistep feeding.The product was filtered,and then it washed by using 3 mol/L hydrochloric solution.The binary Pt-Sn metal cluster is obtained by dried at vacuum drier?0.01 MPa?.After that,the binary Pt-Sn metal cluster is obtained by low temperature recrystallization process in hydrochioric/ethanol mixture.Using technical method of NMR,UV-vis,single crystal diffraction to analyze metal cluster structure.Secondly,the binary Pt-Sn metal cluster supported catalyst on Al₂O₃ is prepared by an impregnation method.We futher regulate and control the support material and impregnating solution.The as-prepared supported Pt-Sn catalyst is denoted as PtSn-C/Al₂O₃.Compared with co-impregnation of PtSn/Al₂O₃ catalyst found that under the same reaction conditions,PtSn-C/Al₂O₃ catalyst has better propane dehydrogenation activity and stability.Finally,we tried to improve the activity and stability of Pt catalyst in propane dehydrogenation by doping non-metallic additives?B?P?Si?.It was found that doping B,P and Si with appropriate content was conducive to improving the propane dehydrogenation activity of Pt catalyst.