Aluminium sulphate, sodium aluminate, aluminium oxide and pseudo-boehmite were used as sources of aluminium in the synthesis of SAPO-5. The samples were characterized using XRD, SEM, XRF, FTIR and nitrogen adsorption. The formation of SAPO-5 phase, morphology, surface area and catalytic properties were found to be influenced by the source of aluminium used in the synthesis. The sample synthesized using pseudo-boehmite as a source of aluminium showed most phase pure silicoaluminophosphate, whereas syntheses using aluminium phosphate or sodium aluminate only formed quartz and berlinite. The FT-IR spectra exhibited the presence of Bronsted and Lewis acid sites in the Pt-SAPO-5, SAPO-5, Pt-H-mordenite and H-mordenite catalysts. Modification of SAPO-5 and mordenite by Pt impregnation did not influence the structures of these catalytic materials. The Pt-H-mordenite and H-mordenite catalysts with stronger Bronsted acidity exhibited higher conversion of n-butane and yield to isobutane than Pt-SAPO-5 and SAPO-5 catalysts with weak acid sites. Introduction of Pt in SAPO-5 and mordenite played a positive role in the isomerization of n-butane to isobutane. (c) 2004 Elsevier B.V. All rights reserved.