Studies Of Preparation And Process Of Isobutane Dehydrogenation Catalysts

As an important organic chemical raw material,isobutene is used as the basic feedstock of producing MTBE,butyl rubber,polyisobutylene and methyl methacrylate.China owns rich resources of C4,generally as fuel,which caused a great waste of resources.Dehydrogenation of isobutane to isobutene can ease the contradiction between supply and demand of isobutene.In this thesis,the catalysts were prepared by liquid-reduction method.The preparation conditions of Pt-Sn-K/?-Al₂O₃ catalyst were optimized by desiging orthogonal experiments.Effects of Fe,Sn and In on isobutane dehydrogenation over platinum based catalysts were investigated.The results showed that the addition of Fe can intensify cracking and isomerization reactions.While In can suppress these side reactions.Sn can improve the isobutane conversion,but the selectivity of isobutene decreased,which is due to the acidity of catalyst.The processs of isobutane dehydrogenation also was studied in the thesis.The experimental results showed that when isobutane flow rate was greater than 38 m L/min,there were no external mass transfer limitations.There were no internal mass transfer limitations when the size of the catalyst pellet was 60-80 mesh.The best dehydrogenation performance of isobutane was obtained when the catalyst was reduced in hydrogen atmosphere,the reduction temperature was 500?.Hydrogen can improve the stability of the catalyst.The effects of four variables,mass ratio of platinum to tin,concentration of H2PtCl6,calcination temperature and K loading?mass fraction?at four levels were investigated.The order of the influence on the initial isobutane conversion was: mass ratio of platinum to tin> K loading> calcination temperature> concentration of H2PtCl6.The four factors had little influence on isobutene selectivity except mass ratio of platinum to tin.Pt/Sn,K loading and H2PtCl6 concentration had significant influence on deactivation parameter,while calcination temperature had little influence.The best preparation conditions are: mass ratio of platinum to tin 1:1,concentration of H2PtCl6 7.72×10-4mol/L,calcination temperature 500?,K loading 1.0%.The results show that the Pt-Sn-K/?-Al₂O₃ catalysts prepared according to the selected conditions exhibit well performance and high stability.The isobutane conversion was 46.59%,and isobutene selectivity was 95.37%.The catalyst was prepared by shaping method,the initial conversion of isobutane is 46.30% and isobutene yield reached 42.60%.The catalytic activity of the catalyst recovered after regeneration.Platinum particles were sintered after repeated regeneration.