Shape-Selective Alkylation of Biphenyl over H-[Al]-SSZ-24 Zeolites with AFI Topology

H-[Al]-SSZ-24 zeolites with AFI topology were synthesized through the alumination of [B]-SSZ-24 zeolites, andapplied for the alkylation of biphenyl (BP). H-[Al]-SSZ-24 zeolites have high activity for the isopropylation. The shapeselectiveformation of 4,40-diisopropylbiphenyl (4,40-DIPB) occurred at moderate temperature; however, the selectivityfor 4,40-DIPB decreased with an increase in the reaction temperature. Isomerization of 4,40-DIPB occurred at higher temperaturesover internal and external acid sites when there are enough acid sites inside the channels. The channels candiscriminate 4,40-DIPB from the other DIPB isomers in their transition states; however, they can not prevent the isomerizationof 4,40-DIPB at higher temperatures. The selectivity for the least bulky 4,40-dialkylbiphenyl increased with thebulkiness of alkylating agents in the order: isopropylation < s-butylation < t-butylation. These results strongly supportthe shape-selective formation of the least bulky products inside the channels of H-[Al]-SSZ-24 zeolites