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Industrial process for continuous production of zeolite A

  • US 4,314,979 A
  • Filed: 12/19/1979
  • Issued: 02/09/1982
  • Est. Priority Date: 07/29/1977
  • Status: Expired due to Term
First Claim
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1. 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 SiO2 /Na2 O molar ratio ≧

    2.8 to 1; and

    containing about 45 to 105 g/l of NaOH and about 120 to 350 g/l of SiO2 ;

    (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 Al2 O3 ;

    (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 Al2 O3 ;

    (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++ /g of dry product.

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