tert-Butylation of toluene with isobutylene over zeolite catalysts:: Influence of water

tert-Butylation of toluene with isobutylene in the liquid phase was studied over large pore zeolite catalysts (H-MOR CBV 21A with Si/Al = 10.5 and H-BEA CP 814E with Si/Al = 12.5) and over cerium modified parent zeolite H-MOR with 2 wt.% of cerium. The influence of catalyst and different amount of added water on tert-butylation of toluene with isobutylene as alkylating agent on catalytic activity and para-selectivity was studied. H-MOR was slightly more active than H-BEA when tert-butylation of toluene with isobutylene in the liquid phase was carried on in the absence of water (45% and 40% conversion of toluene, respectively) at 180 degrees C after 8 h with para-selectivity for both catalysts near 68%. When different amount of water was added to the reaction mixture (0-200 mmol) the maximum conversion increased significantly in the case of both catalysts H-MOR and H-BEA and it was obtained at 120 mmol of water/40 mmol of toluene. At optimum amount of added water (120 mmol/ 40 mmol of toluene) the conversion over H-MOR and H-BEA of toluene reached 60% and 66% respectively which is maximum at given reaction conditions. Maximum constant para-selectivity for both catalysts was near 90% (93% for H-MOR and 90% for H-BEA respectively for maximum amount of added water (200 mmol/40 mmol of toluene)). The positive influence of optimal amount of added water on catalytic activity and para-selectivity in tert-butylation of toluene with isobutylene in the liquid phase over H-MOR and H-BEA is shown in this paper. para-Selectivity increased monotonically within studied range of added water. The influence of water on coke deposits on catalysts was demonstrated by TGA analyses which clearly demonstrated that added water has inhibition effect on carbon deposition. tert-Butylation of toluene with isobutylene over shape-selective zeolite catalysts H-MOR and H-BEA can be an ecofriendly process for industrial preparation of 4-tert-butyltoluene which is important intermediate product for fine chemicals. (C) 2007 Elsevier B.V. All rights reserved.