Environmentally clean synthesis of diphenylmethanes using silica gel-supported ZnCl2 and FeCl3

Lewis acids such as FeCl₃ and ZnCl₂ were supported on silica gel, alumina, zirconia and titania by co-grinding with anhydrous Lewis acids in appropriate proportions in an agate mortar. The catalysts have good shelf life and reusability. Synthesis of diphenylmethanes with these catalysts was studied; silica gel was the best support. © 1998 SCI