Shape-selective isopropylation of biphenyl over CIT-5 zeolites with CFI topology

Abstract

In the isopropylation of biphenyl (BP) over a one-dimensional fourteen-membered ring (14-MR) CIT-5 zeolite with CFI topology, the selectivities for 4,4′-diisopropylbiphenyl (4,4′-DIPB) were 50–70% in the bulk and encapsulated products at moderate temperatures below 300 °C. However, they decreased at high temperatures such as 350 °C. These results mean that CIT-5 zeolites can preferentially exclude the transition state of the bulky DIPB isomers from their channels, thus resulting in the selective formation of 4,4′-DIPB. However, the isomerization of 4,4′-DIPB occurred on external and internal acid sites of the zeolite.