The effect of gel pH on the crystallization of aluminophosphate molecular sieve AlPO4-5

The effect of initial gel pH on the crystallization kinetics of AlPO4-5 when synthesized from a gel containing x Pr3N : Al2O3: P2O5: 40 H2O was studied. The pH of the starting gel was varied either by taking different amine content (x varied from 0.75 to 1.75) or by the addition of aqueous ammonia and sodium hydroxide solution to the starting mixture keeping amine content at x = 1. The increase in the gel pH was observed to enhance the rate of crystallization of AlPO4-5. The role of amine in enhancing the kinetics has been discussed. (C) Elsevier Science Inc. 1997.