Molecular sieve synthesis

In the process for synthesizing a crystalline microporous molecular sieve which comprises the steps of:

• (a) forming in a reactor an aqueous reaction mixture suitable for the hydrothermal production of a crystalline molecular sieve, said reaction mixture containing at least one nitrogen-containing organic templating agent and optionally a supplemental organic base;
• (b) establishing a crystallization period by heating and maintaining said reaction mixture at a crystallization temperature of at least 100.degree. C. to from crystals of the molecular sieve product and establish an equilibrium between molecular sieve crystal formation and molecular sieve dissolution;
• and
• (c) recovering the crystallized product from the reaction mixture;
• the improvement which comprises forming the reaction mixture of step (a) to contain organic base in excess of the amount to be incorporated within the product molecular sieve crystals, and thereafter removing at least some of said excess organic base during the course of the crystallization period of step (b) whereby the said equilibrium between product formation and product dissolution of the reaction system is shifted in favor of decreased dissolution of molecular sieve product at the existing temperature conditions.