Industrial process for continuous production of zeolite A
AssigneePCUK Produits Chimiques Ugine Kuhlmann
InventorJean Deabriges
Life of this patent
Estimating the term…
Abstract
A process for continuous preparation of zeolite A of constant and homogeneous quality, consisting of instantly and continously mixing a sodium silicate solution and a sodium aluminate solution in the correct proportions and at an elevated temperature followed by transfer of the resulting slurry to a crystallization reactor. The product is recovered from the crystallization reactor washed and dried.
Claims6
A process for the continuous preparation of zeolite A, suitable for use in detergents to soften calcium containing waters, having a constant homogeneity and quality wherein at least about 90 percent of the product has a granulometry within a range of 4 microns and a median diameter between about 1 and about 10 microns is characterized by:
- (a) instantaneously and continuously mixing at an elevated temperature in a reaction zone subjected to strong suction:
- (i) a sodium silicate solution prepared from silica and NaOH which contains a minimal excess of NaOH and a SiO.sub.2 /Na.sub.2 O molar ratio .gtoreq.2.8 to 1;
- and containing about 45 to 105 g/l of NaOH and about 120 to 350 g/l of SiO.sub.2 ;
- (ii) a sodium aluminate solution made from alumina and NaOH having an excess of NaOH solution, and containing about 80 to 110 g/l of NaOH and about 50 to 65 g/l of Al.sub.2 O.sub.3 ;
- (b) precipitating the zeolite while continuously stirring the resulting solution at an elevated temperature and while restricting the volume of the reaction zone to insure that there is a local excess of dissolved alumina in relation to dissolved silica in the solution;
- by:
- (i) introducing the sodium silicate and sodium aluminate solutions into the suction zone created by a rapidly rotating turbine;
- and
- (ii) adjacently surrounding the turbine with plates constructed and arranged to restrict the volume in which the above silicate and aluminate solutions are initially mixed;
- (c) continuously removing the precipitated zeolite A and resulting liquor to a crystallization zone;
- (d) continuously stirring the resultant precipitate and liquor in the crystallization zone at an elevated temperature until the desired crystallization is obtained;
- (e) maintaining the concentration of the liquor in the crystallization zone between about 2 to 10 g/l of Al.sub.2 O.sub.3 ;
- (f) removing the most dense or larger particles in suspension at the bottom of the crystallization zone;
- and
- (g) recovering the zeolite A containing at least about 90 percent of the particles within a range of about 4 microns and having a median diameter between about 1 and 10 microns and an ion exchange capacity greater than 85 mg. Ca.sup.++ /g of dry product.
The process according to claim 1 comprising a recycling of the mother liquor which is characterized by continuously:
- (a) concentrating the mother liquor sufficient to permit a replenished aluminate solution having substantially the same volume as the prior aluminate solution;
- (b) replenishing the NaOH in the mother liquor in an amount sufficient to compensate for the NaOH consumed during the prior crystallization of zeolite A;
- (c) charging the mother liquor with alumina in an amount sufficient to compensate for the alumina consumed during the prior crystallization of zeolite A;
- and
- (d) mixing the charged mother liquor with the sodium silicate solution as recited in claim 11.
Dependencies are inferred from the claim text.