Transalkylation of polynuclear aromatics with diisopropylbenzene over zeolite catalysts

Transalkylation of naphthalene and biphenyl with p-diisopropylbenzene has been studied over Y, Beta, mordenite and ZSM-12 zeolites. The main products of naphthalene or biphenyl interaction with p-diisopropylbenzene were mono- and diisopropylsubstituted naphthalenes or biphenyls, cumene and benzene. Polyalkylated binuclear aromatic compounds were observed only in small amounts. Among the zeolites studied, Beta catalyst was the most active, while mordenite showed the highest shape selectivity towards β,β′-diisopropylnaphthalenes and p,p′-diisopropylbiphenyls. Dealumination of mordenite led to the creation of a secondary micro/mesopore structure, providing for easier transport of the alkylaromatic compounds inside the pores and higher acid sites accessibility. Both factors led to a significant improvement of the catalytic activity, stability and selectivity. The highest conversions of naphthalene (78%) and biphenyl (57%) were obtained over mordenite dealuminated by calcination at 750 °C followed by leaching with methanesulfonic acid, while the highest selectivities to β,β′-diisopropylnaphthalene (90%) and 4,4′-diisopropylbiphenyl (79%) were observed over calcined mordenite treated with oxalic acid.