Chemisorption of CH3OH and CD3OD on NaY and HY zeolites was investigat
ed by i.r. spectroscopy. The reaction ''in situ'' of methoxy groups wi
th benzene was observed. It was found that the first step of methylati
on of the benzene ring is the chemisorption of methanol on the acid si
tes of the zeolites. Then, methoxy groups react with the aromatic ring
.