Improvements in and relating to crystalline synthetic faujasites

Crystalline synthetic faujasite having the following molar ratios of constituents in its dehydrated form 1.0\sB0.2Na2O : Al2O3 : nSiO2 wherein n is from 4 to less than 8, is prepared by forming an aqueous reaction mixture containing Na2O, SiO2 and Al2O3, the molar ratios of the constituents being within one of the following ranges heating the reaction mixture from 80 DEG to 120 DEG C. and maintaining this temperature for 5 to 50 hours and then recovering the crystallized product. The temperature of the reaction mixture may be maintained above its freezing point but below 38 DEG C. until all the reactants have been combined to completethe formation of the reaction mixture which is subsequently heated to 80 DEG to 120 DEG C. The constituents may be supplied by NaOH, colloidal SiO2 sol, preferably containing 30-50 weight per cent of SiO2 and sodium aluminate especially in the form of sodium aluminate liquor prepared by the addition of alumina trihydrate to hot concentrated NaOH solution. The reaction mixture may be combined with an inert diluent liquid having heat exchange properties, a flash point above 120 DEG C. and being immiscible with water, reaction mixture and zeolites, e.g. hydrocarbon oil, before the reaction mixture is heated and subsequently heating the suspension of reaction mixture in inert diluent with agitation, agitation being discontinued just before the elevated temperature is reached.