The isopropylation of biphenyl over H-mordenite: roles of 3- and 4-isopropylbiphenyls

摘要: The isopropylation of biphenyl (BP) and 3- 4-isopropylbiphenyls (3- 4-IPBPs) was examined over H-mordenites (MOR) to elucidate the mechanism shape-selective formation 4,4′-diisopropylbiphenyl (4,4′-DIPB). BP occurred predominantly form 4-isopropylbiphenyl (4-IPBP) from 4,4′-DIPB 4-IPBP. However, 3-IPBP, a minor isomer BP, cannot participate effectively in 3,4′-DIPB due steric restriction its isopropyl moiety with MOR channels. Selective observed at low moderate temperatures: 225–275 °C. selectivities for were decreased high temperatures, 300–350 °C under propene pressure, 0.8MPa, by isomerization external acid sites. pressure even 250 roles 4-IPBPs DIPB isomers their mixtures. 4-IPBP consumed much faster than 3-IPBP all cases examined. an exclusive precursor isomers, particularly 4,4′-DIPB. also found as predominant encapsulated products conditions These results show that can preferentially establish active transition state site channels, resulting selective It is concluded occurs through reactant selectivity restricted mechanism, but not product mechanism.