Production of X Zeolites

摘要

Sodium X zeolite containing little or no sodium A zeolite as by-product, is prepared by direct synthesis from a uniform, substantially potassium ion free aqueous reaction / mixture comprising silica, alumina and sodium ions, the concentration of the components in the reaction mixture being such that the silica/alumina molar ratio is in the range of about 2.1:1 to about 3.0:1, the sodium oxide/silica ratio is in the range of about 1.2:1 to about 2.5:1 and the water / sodium oxide molar ratio is greater than about 35:1. The crystallization step is carried out by maintaining the reaction mixture at a temperature below about 70 DEG C, but preferably equal to or above 50 DEG C for the duration of the crystallization step. Preferably, the ratios of components in the solutions used to make the reaction mixture are such that in the reaction mixture the silica/alumina molar ratio will be in the range of about 2.25:1 to about 2.4:1; the sodium oxide to silica molar ratio will be in the range 1.6:1 to about 1.9:1; and the water to sodium oxide molar ratio will be greater than about 60:1. The reaction mixture is preferably prepared as a hydrogel.