Synthesis and characterization of large-pore molecular sieves CoSAPO-36 and CoSAPO-46

Abstract

Two cobalt-substituted large-pore molecular sieves. CoSAPO-36 and CoSAPO-46. have been synthesised using tripropylamine and di-n-propylamine as templates. The effect of temperature, time of crystallization and concentration of various components in the initial reaction gel on the crystallinity and phase purity of these structures has been studied. Substitution of cobalt and silicon into the framework has been established using solid-state magic-angle spinning (MAS) NMR and UV–VIS spectroscopy. ²⁹Si MAS NMR of CoSAPO-46 suggests the presence of two crystallographically independent T sites and also of aluminosilicate domains in the framework. While a large concentration of strong acid sites was observed in CoSAPO-46, the number of such acid sites in CoSAPO-36 was low as revealed by temperature-programmed desorption of ammonia.