The catalytic properties of MCM-41 activated with AlCl3, ZnCl2 and other Le
wis acids, such as FeCl3, NiCl2 and CuCl2 were investigated for room temper
ature Friedel-Crafts benzylation in the liquid phase. The catalysts were st
udied under batch-wise as well as continuous operation conditions. AlCl3/MC
M-41 showed higher activity than ZnCl2/MCM-41, while FeCl3/MCM-41, CuCl2/MC
M-41 and NiCl2/MCM-41 were inactive under identical conditions. ZnCl2 offer
ed some advantages due to reduced hydrolytic sensitivity and better selecti
vity. The optimized ZnCl2 loading Of ZnCl2/MCM-41 was 4 mmol g(-1). For AlC
l3/MCM-41, the pore size of MCM-41 did not affect the activity nor the sele
ctivity in the benzylation of benzene. Very low selectivity was observed in
the benzylation of substituted aromatics using AlCl3/MCM-41 as catalyst du
e to a tendency for migration or transfer of the substituent group. With it
s inherently lower activity, ZnCl2/MCM-41 did not catalyze this reaction. I
n a continuous trickle bed reactor, sustained activity of the AlCl3/MCM-41
catalyst could be demonstrated. Hence, MCM-41 supported with AlCl3 or ZnCl2
may be promising candidates to replace AlCl3 in the industrial manufacture
of diphenylmethanes. (C) 2001 Elsevier Science B.V. All rights reserved.