Transalkylation of toluene with trimethylbenzenes over large-pore zeolites

Zeolites Beta, mordenite and Y were evaluated for their activity in transalkylation reaction of toluene with trimethylbenzenes. Zeolite Beta was found to possess the highest conversion in toluene–trimethylbenzene transalkylation as well as a higher stability in time-on-stream compared with mordenite and zeolite Y. The effect of Si/Al ratio in zeolite Beta was evaluated and it was found that transalkylation activity and xylene yields increase with decreasing Si/Al ratio. Zeolite Beta with the lowest Si/Al ratio of 12.5 (the highest concentration of active sites) exhibited the highest 1,2,4-trimethylbenzene (124TMB) conversion and maximum xylene yield. The highest xylene yield was obtained at optimum equimolar ratio (1:1) of 124TMB to toluene. With increasing 124TMB concentration in the feed, the conversion of 124TMB and xylene yield decreased while toluene conversion simultaneously increased. The increase in the concentration of toluene in the feed resulted in the increase in the conversion of 124TMB. However, addition of higher concentrations of toluene led to a significant decrease in xylene yield.

The effect of channel architecture with optimized acidity of zeolite Beta to achieve high trimethylbenzene and toluene conversions and xylene yields is reported. Equimolar ratio of toluene and trimethylbenzenes was found as the optimum while any shift from this value leads to a decrease in xylene yield.Figure optionsDownload high-quality image (36 K)Download as PowerPoint slide