Toluene disproportionation and methylation over zeolites TNU-9, SSZ-33, ZSM-5, and mordenite using different reactor systems

An array of zeolites varying in the channel structural design and acidity was investigated in toluene methylation with methanol, together with toluene disproportionation, using fluidized-bed and fixed-bed reactors. The conversions of toluene in the methylation and disproportionation reactions in the fixed-bed reactor were higher than those in the fluidized-bed reactor over the zeolite based catalysts at similar reaction conditions. The unique pore architecture of zeolite TNU-9, with 10-ring channel systems, being slightly larger zeolite compared with ZSM-5, can offer new opportunities for toluene disproportionation, as well as for toluene methylation. The medium pore zeolite TNU-9 was found to possess the highest conversion in toluene disproportionation as compared with other zeolite based catalysts under study. In toluene methylation, the highest toluene conversion was achieved with mordenite based catalyst (MOR-A), while the xylene selectivity follows the order: ZSM-5 > TNU-9 > MOR-A > SSZ-33 > MOR-B. This order indicates that xylene selectivity is directly related to the size of channels from medium to large pore zeolites. Using the fluidized bed, the apparent activation energies for toluene methylation follow the order: ZSM-5 (46.8 kJ/mol) > TNU-9 (33.9 kJ/mol) > MOR-B (13.9 kJ/mol) ≈ MOR-A (13.1 kJ/mol) > SSZ-33 (8.2 kJ/mol).