A series of Al2O3-doped (0.5-3 mol%) sulfated tin oxides have been prepared by a co-precipitation method, followed by sulfation and calcination. Textural and structural characterizations of these samples were performed by means of XRD, N-2 adsorption, XPS, DTG, Raman spectroscopy, diffuse reflectance UV-vis spectroscopy and Al-27 MAS NMR. FT-IR spectra of adsorbed pyridine were used to determine the acid properties. The addition of small amounts of Al2O3 (0.2-1.5 mol%) to sulfated tin oxide brings about a dramatic improvement of catalytic activity from 36.1 to 52.4-58.0% for acylation of 2-methoxynaphthalene with acetic anhydride.