Shape Selective Alkylation Reactions Over Medium Pore High Silica Zeolites

The medium pore high silica zeolites Theta-1, ZSM-5 and ZSM-11 have been synthesised. Intrinsic differences in shape selectivity were determined by monitoring the formation of diisopropylbenzenes and xylenes from alkylation reactions. Theta-1 shows enhanced selectivity towards para-substitution which can be attributed to increased transition-state selectivity. Coke laydown in ZSM-5 is more severe when nonframework species, eg M+, Al2O3, are present which leads to improved selectivity and decreased conversions.