The Research On Deactivation And Regeneration Of ZSM-35 Zeolite Catalyst During Skeletal Isomerization Of 1-butene

In this paper,small crystal grain size and large crystal size ZSM-35 zeolite catalysts were successfully prepared and studied in skeletal isomerization of 1-butene.The zeolite was characterized by XRD,SEM,BET,TG and other characterization S.The deactivation of ZSM-35 catalysts with different grain sizes was studied.The effect of deactivation on dealuminum modification with oxalic acid and citric acid based on L-ZSM-35 were studied.The effect of aluminum binder and silicon binder on the deactivation of L-ZSM-35 zeolite was investigated.The deactivation and regeneration of L-ZSM-35 zeolite under industrial conditions were also investigated.The results are as follows:(1)Small crystal grain size ZSM-35 zeolite showed better catalytic performance.In WHSV=7,atmospheric conditions,the TOS of small crystal ZSM-35 zeolite reached 146 h with the isobutene yield over 40% and isobutene selectivity over 90%.At the same time,the small crystal grain size zeolite has a lower rate of coke deposition rate and larger coke deposition capacity,the content of coke deposition was over 12%.(2)According to the characteristics of zeolite deactivation,the coke deposition system was divided into two parts: coke deposited at reaction stage I and coke deposited at reaction stage II.Although the coke deposition at reaction stage I was great,which accounts for more than 80% of the total coke deposition,they played a role of covering non-selectivity acid sites.Coke deposited at reaction stage II was primarily cause of the zeolite deactivation which accounting for about 20% of the total coke content.(3)The effect of dealuminum was better with the concentration of oxalic acid 3mol/Lor citric acid 1 mol/L.The L-ZSM-35 showd a better catalytic performance which the yield of isobutene was more than 40%,the selectivity of isobutylene was more than 90% and the TOS reached over 65 h after dealuminum treatment.Dealuminum effectively reduced the content of coke deposition and increase the carbon deposition capacity at reaction stage II.(4)L-ZSM-35 zeolite modified by bonding silica showd a better catalytic performance which the yield of isobutene was more than 40%,the selectivity of isobutylene was more than 90% and the TOS reached over 60 h.The larger external channels were,the slower L-ZSM-35 zeolite was deactivation.(5)There is some toxic substances contained in industrial 1-butene and will lead zeolite unregeneration.The longer regeneration time had,the better regeneration effect zeolite had.