A series of dealuminated mordenite samples was prepared and tested for their activity in n-hexane hydroisomerization reaction. The samples were thoroughly characterized by XRD, microcalorimetry, and adsorption measurement to obtain surface area, pore volume and pore size distribution. Both strong acidity (Delta H-NH3 > 100 kJ/mol) and micropore volume (0-20 angstrom) of the mordenite were increased during the initial stage of dealumination. Further dealumination caused very little or negligible improvement in the catalytic properties. Among the various catalysts prepared, the catalyst dealuminated by steaming at 673 K, followed by acid leaching with 2N HNO3 (S2-HM) exhibited highest amount of strong acidity and isomer yields in n-hexane conversion. The selectivity to di-branched isomers was continuously increased with dealumination. (c) 2006 Elsevier B.V. All rights reserved.