The Influence of Temperature of Gel Ageing on Synthesis and Properties of the Silicoaluminophosphate Molecular Sieve SAPO-11
The influence of temperature of ageing of the initial silicoaluminophosphate gel on crystallization of the molecular sieve SAPO-11 was studied. It was established that with pseudoboehmite used as the source of aluminum, a gel containing di-n-propylamine phosphate, non-dissolved pseudoboehmite and amorphous silicoaluminophosphate was formed. Elevation of the gel ageing temperature from 25 to 90 °C was shown to result in an increase in the proportion of the amorphous phase in the gel. Crystallization of the silicoalumophosphate gel at 90 °C allowed SAPO-11 to be crystallized at high phase purity and close to 98 % crystallinity. A high activity and selectivity (86 %) of SAPO-11 to linear dimmers was observed during dimerization of α-methylstirene.