NANOMETER-SIZED MOLECULAR SIEVE CRYSTALS OR AGGLOMERATES ANDPROCESSES FOR THEIR PRODUCTION

A molecular sieve comprising crystals or agglomerates of average diameter 10 0 nanometers or less, which molecular sieve has a crystal or agglomerate size distribution such that the variance in the longest dimension is less than 15 % of the average longest dimension, and which is capable of forming a colloidal suspension, m ay be prepared by producing a boiling aqueous synthesis mixture of a silica source and an organic structure directing agent in the form of a hydroxide in an amount sufficient to cause substantially complete dissolution of the silica source, and crystallising t he solution at 120.degree.C or less. The crystal size may be controlled by selection of an appropriate crystallisation temperature.