Synthesis Of Triisopropyl Benzene By Alkylation Of Benzene With Propylene Used Chloroaluminium Molten Salts As Catalyst

In this thesis, the alkylation of benzene with propylene catalyzed by chloroaluminum molten salts was studied. Using the molten salt synthesized from triethylaminia hydrochloride and anhydrous AlCl3as the main catalyst, the catalytic properties of chloroaluminium molten salts for the synthesis of triisopropyl benzene by alkylation of benzene with propylene were investigated. The effects of the constitute of the molten salts, catalyst addition amount, temperature, feed rate on the alkylation and the reuse of the molten salts were studied. It was found that,2AlCl3/Et3NHCl exhibited good catalytic property for alkylation of benzene with propylene for the preparation of triisopropyl benzene. The separation of the product and the catalyst was convenient.At the optimal conditions, i.e.66.7%of mole fraction of A1C13in the chloroaluminium molten salts,5wt%of catalyst with respect to benzene,3.50ml/s of propylene feed rate,313K, and6.5h, the yield of1,3,5-triisopropyl benzene reached89%. The ratio of1,3,5-triisopropyl benzene to1,2,4-triisopropyl benzene can be up to80. The further alkylation of the products using some alkylating agents was the effective method to improve the ratio of1,3,5-triisopropyl benzene to1,2,4-triisopropyl benzene. The activity of2AlCl3/Et3NHCl can be basically remained after five times reuse.The crude products of alkylation were purified by distillation in rectifying column.1,3,5-Triisopropyl benzene with purity of98wt%was obtained.Moreover, the transalkylation reaction of benzene and diisopropylbenzene, triisopropylbenzene and tetraisopropyl benzene using some chloroaluminium molten salts were investigated, respectively. The effects of the reaction conditions were also studied. It was found that the molten salts of2AlCl3/Et3NHCl and2AlCl3/BmimCl both exhibited good catalytic property for the transalkylation. Using2AlCl3/Et3NHCl as the catalyst, the conversion of polyisopropyl benzene can be up to99%in60minutes.The mechanism of the alkylation of benzene with propylene was also investigated via quantum method. The energy trend of the elementary reactions and transition state of the alkylation were obtained using Hyperchem7.0software package. The results shown that, it is easier for the formation of1,3,5-triisopropyl benzene than that of1,2,4-triisopropyl benzene. However, the further alkylation of1,2,4-triisopropyl benzene was more active that that of1,3,5-triisopropyl benzene. The formation of teraisopropyl benzene from1,2,4-triisopropyl benzene increase the ratio of1,3,5-triisopropyl benzene to1,2,4--triisopropyl benzene.