Process for preparing low silica forms of zeolites having the faujasite type structure

摘要

Low silica forms of faujasite-type zeolites are prepared from more siliceous forms of the same zeolite species by contacting the starting zeolite with a highly caustic concentrated sodium aluminate solution at elevated temperatures. In view of the fact that the process does not favor the formation of undesirable impurity phases such as zeolite A and thus does not require the presence of zeolite A nucleation inhibitors, the process is particularly advantageous in the production of forms of zeolite X having Si/Al2 molar ratios below 2.5.