Novel catalytic aspects of beta zeolite for alkyl aromatics transformation

A highly siliceous, large pore, crystalline aluminosilicate has been employed as a catalyst for several industrially important reactions. These reactions include benzene isopropylation to cumene, isopropylation of toluene to cymene, cumene alkylation to diisopropyl benzene, transalkylation and disproportionation of C-7 and Cg aromatic streams to produce xylenes and metaxylene isomerisation in the presence of ethylbenzene. Beta zeolite selectively catalyses benzene alkylation to cumene and formation of n-propyl benzene has been almost eliminated. Beta zeolite was found to be selective for cymenes and diisopropyl benzene formation. The all;ylation activity of zeolite beta for cumene isopropylation can be stabilised by steaming and treatment with (NH4)(2)SiF6 in disproportionation and transalkylation over large pore beta zeolite the xylene yields were found to be better as compared to that of medium pore zeolites. Beta zeolite appears to be quite promising a candidate for several commercial applications. (C) 1999 Elsevier Science B.V. All rights reserved.