| 摘要 |
Synthetic zeolites are prepared by treating firm calcined non-zeolite particles of fixed size and shape which have been prepared synthetically so as to comprise at least one of the oxides silica and alumina with an aqueous solution containing alkali metal cations and hydroxyl, silicate and aluminate anions, and recovering alkali metal zeolite particles from the solution. The non-zeolite particles may be spheroidal in shape and the process may comprise treating silica with alkali metal aluminate, alumina with alkali metal silicate or alumina and silica with alkali metal hydroxide. The alkali metal may be sodium, potassium or lithium and the proportions in the reaction mixture may be adjusted to give a type A or type X sieve. The alkali metal zeolites may be subjected to ion exchange to give alkaline earth metal zeolites. The non-zeolite particles are calcined at 350-700 DEG C., the temperature of the aqueous treating solution may be 25-150 DEG C. and its pH greater than 11. The silica or alumina particles may be prepared by adding hexamethylenetetramine or urea to a silica or alumina sol, dropping the mixture into an oil-bath at less than 100 DEG C., aging, washing, drying and calcining the resulting hydrogel particles. Alternatively commercial catalytic cracking catalyst may be used. The sieves produced may be impregnated with metal catalyst (e.g. Pt) and used for reforming hydrocarbons.
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