Pillared clays as catalysts for cracking of c//8hydrocarbons

Solid shape-selective catalysts with well defined pores approaching 1 nm in diameter are needed for reactions involving hydrocarbons such as those found in heavy residua or in middle distillates. This pore size is greater than that encountered in zeolites but can be found in pillared clays. Clays pillared with polymeric oxoaluminium cations and having different pillar densities have been prepared. These clays, in contrast to zeolite catalysts, have been shown to possess shape selectivity in hydrocarbon cracking reactions involving molecules larger than C//6. This selectivity may be described by defining a series of constraint indices which are functions of the geometric match between the hydrocarbon reactant and the pore.