Influence of toluene–tetramethylbenzene transalkylation on heavy aromatics conversion to xylenes

Transalkylation of toluene–tetramethylbenzene (TeMB) over MOR and BEA was investigated at 250–400°C. Conversion of TeMB was higher than trimethylbenzene (TMB) and toluene. Xylene yield was in the following order: toluene−TMB−TeMB>toluene−TeMB>toluene−TMB≫toluene. Kinetic modeling for reaction network consisting of toluene–TeMB transalkylation; toluene disproportionation; and toluene–TMB transalkylation was carried out. Toluene–TeMB transalkylation rate was >50% higher than the toluene–TMB transalkylation while the toluene disproportionation was an order of magnitude slower than transalkylation reactions. An addition of 5–10wt.% TeMBs to the heavy reformate caused minor impact on the xylene yield but an improvement in xylene selectivity.