Theoretical study of the Ga/SAPO-11 catalyst

Calculations to study the interaction of Ga+, [GaO]+ and Ga2O with a Brönsted 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 H2 are thermodynamically favored. The transformation of [HGaOH]+ into Ga+ and water is highly endothermic. The Ga2O react with the Brönsted 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.