Zeolite Catalyzed Alkylation of Biphenyl. Where Does Shape-Selective Catalysis Occur?

摘要: Liquid-phase alkylation of biphenyl (BP) was studied over large-pore zeolites. Selective formation the least bulky products, 4,4′-diisopropylbiphenyl (4,4′-DIPB) occurred only in isopropylation BP one- or two-dimensional zeolites, H-mordenite (HM), ZSM-12, SSZ-24, SAPO-5, SSZ-31, and CIT-5. These shape-selective catalyses are ascribed to steric restriction transition state easiness substrates enter into pores. HM gave highest selectivity among them. The dealumination enhanced catalytic activity for 4,4′-DIPB because decrease coke deposition. Non-regioselective catalysis occurs on external acid sites with low SiO2/Al2O3 ratio severe deposition deactivates inside pores by blocking pore openings. DIPB isomers changed propylene pressure and/or reaction temperature. observed at moderate temperatures such as 250 °C, whereas higher 300 °C. yielded selectively under high (<0.3 MPa) while decreased 0.2 MPa. However, almost exclusive isomer encapsulated every temperature pressure. is due isomerization sites. deactivation examined modification cerium other rare earth metal oxide HM. Selectivities were improved modified even suppression non-regioselective ethylation ethylbiphenyls (EBPs) diethylbiphenyls (DEBPs) non-regioselective. EBPs controlled kinetically. there difference reactivities DEBPs their further ethylation. 4-EBP ethylated preferentially isomers, although 4,4′-DEBP less selective. have polyethylbiphenyls (PEBPs). results show that environments too loose 4,4′-DEBP, BP, enough space 4,4′-DEBP.