The mesoporous molecular sieve Al-MCM-41 and sulfated Al-MCM-41 were prepared and characterized with various techniques: XRD, ICP-AES, BET, Al-27 and Si-29 MAS-NMR, FTIR, TPD of ammonia and N-2 adsorption isotherms. Impregnation of Al-MCM-41 with sulfuric acid results in the decrease of crystallinity, surface area, pore volume and the expelling of aluminum from the AI-MCM-41 framework, with concomitant increase of the Lewis acidity. P-Naphthyl methyl ether was synthesized from P-naphthol and methanol at 200 degrees C and 35 bar over Al-MCM-41 and sulfated Al-MCM-41 in a batch autoclave reactor. The catalytic results were compared with those obtained by using sulfuric acid, amorphous silica-alumina, gamma-alumina, USY and H-ZSM-5 zeolites. The sulfated AI-MCM-41 catalyst forms the exclusive product of beta-naphthyl methyl ether and has much higher yields than other catalysts except USY. The non-framework aluminum existing in the intrachannel space of Al-MCM-41 probably causes the enhancement of catalyst activity. The catalytic results are correlated to the acidity, the surface area and the pore size of the catalysts.