Catalysis of metal supported zeolites for dealkylation-transalkylation of alkyl-aromatics

In search for catalysts with tailorable pore structure for simultaneous dealkylation and transalkylation of C₉ aromatics to produce xylenes, the catalytic performance of layered MWW-type zeolites were compared with mordenite (MOR) in terms of the effects of zeolite topology, metal(s) incorporation and preparation method. During the catalytic reaction of trimethylbenzene (TMB)-methylethylbenzene (MEB) model feed, the ion exchanged Pt-MOR catalyzed a significantly higher MEB dealkylation than H-MOR resulting in an increase in xylene yield (from about 27 wt% to 34 wt%). Impregnation of Re into the Pt exchanged zeolite would moderate Pt hydrogenation activity and reduce MEB conversion. Compared to MOR, MCM-22 and ITQ-2 exhibited lower xylene yield and higher selectivity of C₁₀ aromatics. On the other hand, pillared MCM-36 catalyzed escalated TMB conversion and higher xylene yield at the expense of product selectivity of toluene and C₁₀ aromatics. The improvement in the catalytic performance of MCM-36 is attributed to the enlarged supercage for favorable catalysis for toluene-TMB transalkylation than TMB disproportionation.