The isomerization of 4,4′-diisopropylbiphenyl at external acid sites of H-mordenite during the isopropylation of biphenyl

The roles of internal and external acid sites of a dealuminated H-mordenite (MOR; SiO2/Al2O3 = 128) on the selectivity for 4,4′-DIPB in the isopropylation of biphenyl (BP) are examined by changing catalyst amount. The isopropylation of BP gave high selectivity for 4,4′-DIPB at such a low temperature as 200 °C even by using large amounts of the catalyst; however, the decrease in the selectivity for 4,4′-DIPB, which accompanies the increase in the selectivity for 3,4′- and 3,3′-DIPB, occurred at such a high temperature as 300 °C, and started at lower temperatures with increasing catalyst amount. However, 4,4′-DIPB was highly selective in encapsulated products under all the conditions. These results indicate that shape-selective catalysis occurs inside MOR channels irrespective of reaction conditions, such as catalyst amount and/or reaction temperature, and that the decrease in the selectivity for 4,4′-DIPB is due to the isomerization of 4,4′-DIPB to thermodynamically stable 3,4′- and 3,3′-DIPB at external acid sites.

The roles of external and internal acid sites of H-mordenite in the isopropylation of biphenyl (BP) on selectivities for 4,4′-diisopropylbiphenyl (4,4′-DIPB) was studied by changing catalyst amount and/or reaction temperature. Shape-selective catalysis occurs inside channels irrespective of reaction conditions. The decrease in selectivities for 4,4′-DIPB occurred by using large catalyst amounts and/or at higher temperatures is due to the isomerization of 4,4′-DIPB to 3,4′- and 3,3′-DIPB at external acid sites.Figure optionsDownload as PowerPoint slide