Platinum Tin Nanoparticle Alloy Catalyst In Propane Dehydrogenation Synthesized By Carbonylation Method

Propylene is an important petrochemical intermediates can be used to produce synthetic resin,synthetic rubber and a variety of fine chemicals,and with the growing demand for propylene,the dehydrogenation of propane to propylene is a hot research topic at present.In this paper,platinum tin nanoparticle alloy catalysts were prepared by a novel carbonylation method.Using sodium chloroplatinate,tin chloride and sodium acetate as chemical precursors,carbonyl compound were synthesized under a carbon monoxide atmosphere.The prepared platinum tin nanoparticle alloy catalysts had high purity,single crystal phase,high activity and stability.In order to explore the internal relations between catalytic performance and structure of platinum tin nano-clusters including particle size,shape and crystallization state,several techniques were used to characterize the catalyst.The optimal preparation conditions were investigated,followed by the effects of second additives and optimal reaction conditions in propane dehydrogenation.Firstly,the synthesis process of platinum tin nanoparticle alloy catalyst was studied.The optimal content of platinum was 0.5w%.With the Pt/Sn molar ratio of 3:1,Pt₃Sn alloy with high purity,single crystal phase and small particle size was obtained.Pural SB could be the best alumina precursor,calcinating at 500?lasting for 4 hour.Constant stirring at 25?for 12hour were the optimal loading conditions.The decarbonylation process implemented at 200?for 1 hour in flowing hydrogen,removing carbonyl completely while ensuring the high catalytic activity.For Pt₃Sn/Al₂O₃ catalyst,filtration was the necessary part of the catalyst preparation process and the removal of nitrate ion and chloridion would weaken negative affect on the catalytic performance of catalyst.Filtration should be done at last with a view to the balance of the loss of tin and the perniciousness of chloridion.In order to explore the effects of second additives,six additives including K,Na,Mg,Zn,Ce and In were introduced.Na,Mg and Ce had a positive effect on the performance of Pt₃Sn/Al₂O₃ catalyst while the addition of K,Zn and In decreased the propane conversion significantly.For sodium,the best content was 1.0w%and the optimal adding time was together with Al₂O₃ at the beginning of loading section,obtained 31.3%propane conversion and 92.6%propylene selectivity.Using Na-Al₂O₃ obtained by overloading impregnation method as supporter,the initial propane conversion and propylene selectivity of Pt₃Sn/Na-Al₂O₃ catalyst were as high as 32%and 95.8%respectively.Sodium oxide had tiny effect on subsequent loading and elevated the function of active component and supporter after calcination under550?for 4 hour,which could be good for the improvement of catalytic performance.Finally,a series of reaction conditions such as reaction temperature,weight hourly space velocity of propane and feed ratio of propane to hydrogen were optimized on fix bed reactor.The optimal reaction conditions were as follows:reaction temperature of 580?,atmospheric pressure,weight hourly space velocity of 4h^-1,the feed ratio of propane to hydrogen of 4:1.The BET and TEM data before and after reaction were analyzed and Pt₃Sn/Al₂O₃ possessed excellent activity and stability in propane dehydrogenation.