A catalytic process is provided for the selective production of para-xylene by disproportionation of toluene in the presence of a catalyst comprising a crystalline aluminosilicate zeolite having a silica to alumina ratio of at least about 12 and a constraint index within the approximate range of 1...http://www.google.es/patents/US4097543?utm_source=gb-gplus-sharePatente US4097543 - Selective disproportionation of toluene
