The Transethylation of Biphenyl with Diethylbenzenes over H-Y Zeolite

Abstract

Abstract The liquid-phase transethylation of biphenyl (BP) with diethylbenzenes (DEBZ; o-:m-:p- = 5:66:29) was investigated by the use of zeolites, Y (FAU), Beta (BEA), mordenite (MOR), and ZSM-12 (MTW). Because H-Y (H-FAU(11) with SiO2/Al2O3 = 11) was the most active among them, and we chose H-FAU(11) as a standard catalyst, and studied reaction parameters. Both the catalytic activity and the selectivity for 4,4′-diethylbiphenyl (4,4′-DEBP) were influenced by the reaction conditions. The selective formation of 4,4′-DEBP was observed at low temperatures; however, the selectivity for 4,4′-DEBP decreased with the temperature. The selectivity for 4,4′-DEBP in bulk products were lower than the case of encapsulated products. These results show that the catalysis occurred principally inside pores: 4,4′-DEBP was formed by the transethylation of BP and DEBZ inside the pores of H-Y zeolite. The resultant 4,4′-DEBP was easily isomerized to thermodynamically stable isomers, 3,4′- and 3,3′-DEBPs even at lower temperatures because the most acid sites of H-Y zeolite are inside large pores, and they are strong enough for the isomerization of 4,4′-DEBP. The shape-selective formation of 4,4′-DEBP at lower temperatures is due to the rapid diffusion of the least bulky isomer from the H-Y pores. DEBPs were polyethylated to polyethylbiphenyls (PEBPs), and deethylated to ethylbiphenyls (EBPs) by transethylation with DEBZ inside the pores.