Studies On The Catalytic Cracking Of Butene Over SSZ-13 And SAPO-34

Currently,butene catalytic cracking is one of the most promising technologies.It not only solves the problem of the excess C₄ olefin in the refinery,but also produces more propene.It is important to research of catalyst for butene catalytic cracking.In our study,SSZ-13 was synthesized with benzyl trimethyl ammonium hydroxide.Effects of Si/Al₂ ratio,seed,stirring speed,crystallization condition on synthesis of SSZ-13were explored.When Si/Al₂ between 83 and 125,180℃for 24 h,300 r/min and adding the seed,SSZ-13 was successfully synthesize.Due to SSZ-13 has more acid numbers,it gets more propane on butene catalytic cracking over SSZ-13.Diethylamine（DEA）,triethylammine（TEA）,N,N-Dimethylcyclohexylamine（DMCHA）,andtetraethylammonium hydroxide（TEAOH）can be used to synthesize pure SAPO-34.Test results indicate that template has an influence on crystal size and acidity of SAPO-34.For different template has different ability of introducing Si into framework,the acidity of every SAPO-34 sample is different.And the acidity has an important influence on catalytic performance.SAPO-34 synthesized with DMCHA has appropriate acidity,selectivity of propene exceeded 59 wt%,and P/E ratio was 4.9.And the SAPO-34 synthesized with DEA has stronger acidity,it make the higher conversion of butene.The DEA/TEAOH dual-template appears“additive effect”in acidity and production distribution.On the basis of this,the effect of different Si content in initial gel of SAPO-34 on catalytic performance of SAPO-34 was furthere researched.The result showed that acidity increased with the increase of Si content.In the process of butene catalytic cracking,conversion of butene and propane yield all increased,propene and P/E have decreased.Compared with ZSM-5 molecular sieve with MFI type,CHA type molecular sieves have smaller pore size and restricted C₅⁺to diffuse leading to more ethene and propene.Meanwhile,it easily generates carbon in channel,and the stability is poor.But the SAPO-34 has the bigger cavity and appropriate pore size and acidity,it gets higher yield of propene and P/E.In the last,this article studied the effect of reaction temperature,space velocity of butene and regeneration on catalytic cracking performance of SAPO-34.These results show that in550℃,WHSV of 3.5 h^-1,SAPO-34 has better catalytic performance.After regeneration,SAPO-34 has better stability and more C₅⁺than fresh SAPO-34,but the conversion of butene and yield of propene were less.