Calculations to study the interaction of Ga+, [GaO](+) and Ga2O with a Bronsted acid site of a SAPO-11 silicoaluminophospates were carried out using the semiempirical MSINDO approach. The SAPO-11 structure was modeled by a ring of 10 tetrahedrons and 3 rings of 10 tetrahedrons system. The calculations show that the formation of [HGaOH](+) and [GaH2](+) species by reduction with H, are thermodynamically favored. The transformation of [HGaOH](+) into Ga+ and water is highly endothermic. The Ga2O react with the Bronsted acid site to produce anchored species, which can be reduced by molecular hydrogen to give [Ga(GaH)(OH)] and [GaOGaH2]. The Ga+ and Ga2O reactions with n-butane to produces butenes are all endothermic. (c) 2005 Elsevier B.V. All rights reserved.