The Research Of Zeolite In The Isopropylbenzene Production

Isopropylbenzene(IPB),one of the largest commercial volume derivatives of benzene,is an important intermediate in the production of phenol and acetone,acetophenone,andα-methy- lstyrene.Traditional SPA(solid phosphoric acid) and Friedal-Crafts(AlCl₃) process foe the industrial production of cumene suffer from a variety of problems,such as high environmental contamination and corrosion,Since commercialization of cumene proeesses based on zeolites in 1990s,much effort has been put into developing more environmentally friendly and more efficient zeolite-based processes,which can produce isopropylbenzene at low molar ratio of benzene to propylene.In the present work,we present a comparsion of the performance of Beta zeolite with MCM-22 zeolite in the isopropylbenzene production.MCM-22 behaves higher stability in the alkylation reaction at low temperature and low feed ratio of benzene to propylene than Beta zeolite.However its activity and stability are much lower than Beta zeolte in the transalkylation reaction of diisopropylbenzene(DIPBs) and benzene,meanwhile the molar ratio of n-propylbenze to isopropylbenze over MCM-22 zeolite is 2.5 times as that over Beta zeolite.Molded Beta catalyst in the laboratory behaves high activity and long lifetime in the alkylation reaction of benzene with propylene,and the molar ratio of n-propylbenze to isopropylbenze is about 150 ppm.But in the transalkylation reaction of diisopropylbenzene and benzene,the molar ratio is up to 9000 ppm.The molar ratio of n-propylbenzene to isopropylbenzene can fall to 300 ppm over catalysts modified with Ag,Zr,Ce,La oxides at the little expense of the diisopropylbenzene conversion.It must be pointed out that Beta zeolite catalyst in industrial scale,which is was synthesized according to the laborator patent technology shows silimar alkylation reaction activity with the imported catalyst.Citric acid treatment can wash away morphous materials between Beta zeolite partieles and dredge channel,so the modified Beta zeolites have better stability than unmodified sample in the alkylation reaction,and there are a little increase of content of n-propylbenzene. FT-IR and XRF results show that coking,arsenical and nitric poisoning cause deactivation of QZ2001-04 alkylation catalyst,the regeneration route of washing with citric acid first then calcining is very efficient.