Study On The Catalysis Cracking Reactions Of 1-Butene Over Coupled ZSM-5/SAPO-11 Catalysts

Propene is one of the most important organic chemical materials besides ethene.With the shortage of propene and little use of low-value C4/C5 resources in our country,we plan to gain more propene by catalytic cracking of C4=.According to the networks of catalytic cracking of C4=,we catch the rule that strong acid sites are helpful to produce ethene and weak acid sites are helpful to produce propene.Taking the acidic properties of catalysts into account,we make the phosphorus modified ZSM-5 coupled with SAPO-11 of weak acidic properties.By this method,we will get catalysts of lower acid amounts and weaker acid strength.It’s very helpful to produce more propene.Meanwhile we also apply some different modification methods to SAPO-11 to control its acidic properties.The main experimental results are as follows:1、For the modification of acidic properties over SAPO-11,we try to change the SiO2/Al2O3 ratios in ingredients and the sequence of calcination and ammonium exchange.With the increase of SiO2/Al2O3 ratios,the acid amounts of SAPO-11 increased firstly and then decreased,mainly related to the spread of Si islands.SAPO-11 modified by ammonium exchange before calcination is helpftul to expose its acid sites and keep the skeleton stabilized during the process of calcination.It’s great to enhance the reaction activities of catalysts.2.Through the reaction results of coupled catalysts applied to the catalytic cracking of 1-butene,we find that SAPO-11 contained in the coupled catalysts is beneficial to improve the yield of ethene and propene.And the best coupled ratio is 1:1.Only when the acid amounts and acid strength of SAPO-11 contained in the coupled catalysts is at an appropriate level,its catalytic performance will be much better.SAPO-11 modified by ammonium exchange before calcination contained in the coupled catalysts can make it more stable in the reaction.It’s beneficial to apply the samples to long term reactions.3、hrough the long term reaction results,the coupled catalysts show more excellent reaction performance and catalytic stabilization than the phosphorus modified ZSM-5 during the beginning of reactions.But with reaction time prolonged,the conversion rate of 1-butene has a little decrease,still at a stable level.Mainly related to the small pores of SAPO-11 are easy blocked by the carbon deposition.