Method for making zeolites and zeolite mixtures having enchanced cation exchange properties

Abstract

A zeolite A or an A/X mixture having an LCC>70 g liquid/100 g zeolite (hydrated) and a cold water CER>200 mg CaCO /gram anhydrous zeolite (hydrated). The zeolite product may have a crystal size of 0.1-0.7 microns, a bulk density of 0.19-0.37 g/ml, and a median particle size of 1-5 microns. A process for making zeolite A or A/X mixtures is also claimed, including mixing a sodium silicate solution, a sodium aluminate solution, and an amorphous aluminosilicate initiator gel in a mixing vessel to create an aluminosilicate synthesis gel, and crystallizing the aluminosilicate synthesis gel to form zeolite crystals. The sodium aluminate solution may be added gradually to at least the sodium silicate solution at a rate of about 1-5% of the total batch alumina per minute, and/or a percentage of the total batch alumina may be added as alumina trihydrate (ATH) powder. The amount of total batch alumina added as an undissolved source of soluble alumina and the presence or absence of initiator or “seed” gel determines whether the resulting zeolite product is an A/X mixture or only zeolite A. A process to augment the yield of a synthesis mixture is also claimed, comprising providing undissolved alumina in substantial excess of stoichiometric requirements in a primary crystallization step, yielding a slurry of crystalline zeolite A in an alumina-enriched mother liquor, and then adding soluble silicate to initiate a second stage of very rapid crystallization. Detergents containing zeolites of this invention are claimed.