The active sites of microporous solid acid catalysts

There is much interest in understanding the nature of active sites in microporous catalysts and molecular adsorption at such sites. This paper describes investigation of both aluminosilicate and silicoaluminophosphate (SAPO) forms having the chabazite structure. The nature of the Brø nsted acid sites formed in these materials has been studied using first principles electronic structure calculations, working with periodic boundary conditions to represent the full framework structure. Results are presented for the energetics, geometry and charge density of such acid sites, and the implications for molecular adsorption in zeolite catalysts discussed.