Selective Crystallization of Aluminophosphate Molecular Sieves with an AEL Structure

Abstract

The effect of the temperature and exposure time of the starting aluminophosphate gels on their chemical and phase composition was studied. When the source of aluminum is its hydrated oxide (boehmite), gels with different contents of ammonium phosphate, undissolved boehmite, and amorphous aluminophosphate can be formed. The formation of a gel with dominant amorphous aluminophosphate allows selective crystallization of AlPO₄-11 of high phase purity and ~100% crystallinity. The developed procedure for the preparation of highly dispersed aluminophosphate AlPO₄-11 molecular sieves with these properties allows a transition to crystallization of silicoaluminophosphates SAPO-11—promising domestic catalysts for industrial hydroisomerization of n-paraffins in the production of Arctic diesel fuels and group III oils and isomerization of butenes.