Selective p-xylene formation upon toluene disproportionation over MCM-22 and ZSM-5 zeolites modified with indium

A simple modification procedure of MCM-22 and ZSM-5 zeolites consisting in controllable alteration of the nature and concentration of the acid sites has been applied with the help of the method of reductive solid-state ion exchange with In2O3 in order to achieve selective p-xylene formation upon toluene disproportionation. The partial replacement of the zeolite protons with InO+ counter ions results in enhanced activity and p-xylene selectivity accompanied by fast deactivation in case of MCM-22. The modification procedure of ZSM-5 is more favorable in respect to the catalytic stability and also leads to increased p-xylene formation, however, in lower extent compared to MCM-22. The contribution of the InO+ Lewis-connected acid sites in regulation of the disproportionation rate, catalysts aging and p-xylene selectivation in dependence on the pore structure characteristics of the zeolites is discussed.