Propane steam reforming (PSR) for the production of H-2 was catalyzed by a NiO/K-AlSixOy catalyst synthesized with various Si/Al ratios (Si/Al = 0, 0.3, 0.5, 0.7, and 1.0). The effect of the Si/Al ratio on the acidity of the NiO/K-AlSixOy catalyst for PSR was investigated. NiO/K-AlSixOy gave a higher H-2 selectivity and stability during PSR than NiO/K-SiO2 and NiO/K-Al2O3. The NH3-TPD results showed that the acid quantity and strength of NiO/K-AlSixOy changed significantly depending on the Si/Al ratio. With an increased Si/Al ratio, the densities of both weak and strong acid sites increased. The C3H8- and CO-TPD results indicated that desorption amounts increased significantly in all NiO/K-AlSixOy catalysts relative to those of NiO/K-SiO2 and NiO/K-Al2O3, and the adsorption amount increased with the Si/Al ratio. PSR results showed that the NiO/K-AlSixOy catalyst exhibited much better stability than the NiO/K-SiO2 and NiO/K-Al2O3 catalysts. This study confirms the following facts: when the acidity is appropriately adjusted for the catalyst, adsorption of the reaction gas increases, which eventually increases the reaction rate and also inhibits strong sintering between the nickel and the Al2O3 support. As a result, deterioration of the catalyst can be reduced. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.