KINETIC AND THEORETICAL-STUDY OF THE EFFECT OF MOLECULAR-SIEVE STRUCTURE ON THE SELECTIVITY TO PROPYLBENZENES IN ALKYLATION OF BENZENE WITHISOPROPYL-ALCOHOL

The alkylation of benzene with isopropyl alcohol was investigated over molecular sieves of different structural types and acidity by kinetic measurements and ab initio quantum chemical calculations. The formati on of n-propylbenzene occurring via bimolecular transalkylation betwee n isopropylbenzene and benzene is enhanced by the appropriate geometry of the reaction space and the acidity of molecular sieves, n-Propylbe nzene was formed over medium and large pore molecular sieves with such inner channel architecture which enables the approach of isopropylben zene and benzene to form the reaction complex. Mesoporous sieves of MC M-41 structure provided only isopropylbenzene with some amount of diis opropylbenzenes. For the fully relaxed complex consisting of protonate d isopropylbenzene and benzene, the computations verified the transfer of propyl group from one benzene molecule to another forming again is opropylbenzene. When the geometrical conditions modelling the channel intersections of ZSM-5 and ZSM-11 structures were considered n-propylb enzene was formed. The anti-Markovnikov type of proton transfer from t he arenium cation to the propene part of the complex is promoted by th e steric constraints present in the channel intersections of ZSM-5 and ZSM-11 zeolites.