GB1116664A - Process for preparing a coated zeolitic molecular sieve agglomerate - Google Patents

Abstract

Molecular sieve agglomerates are coated with a finely divided silica-containing material, impregnated with an aqueous solution of an alkali metal silicate, and fired at 650-1220 DEG F. The molecular sieve may be naturally occurring (examples given) or synthetic, e.g. A, T, X, Y, and is agglomerated alone or with water and 5-35% of a binder, e.g. silicates and/or clays (examples given), to give spheres of size 8-12 mesh. The coating may be from 1 to 0.003 in. thick, and may be of clay, e.g. attapulgite (others are listed), asbestos, mica, quartz glass frits or enamels, preferably less than 300 mesh in size. It is applied to the damp agglomerates by tumbling together, or by spraying with an aqueous dispersion. The impregnant may be Na, K, Li, Rb or Cs silicate with a M2O/SiO2 weight ratio of 0.27-0.63 and a solids content of 3-35 wt. per cent, and may contain colloidal silica. Contact, with 0.07-0.73 pts. solution solids per pt. agglomerate, may be effected at below 60 DEG C. either batchwise with agitation, or continuously by percolating the solution through the agglomerates. The agglomerates may then be dried at 180-350 DEG F. to a moisture content of 15-22% b.w. before firing. The product is used as a desiccant. Reference has been directed by the Comptroller to Specification 972,833.ALSO:A desiccant material comprises molecular sieve agglomerates coated with a finely divided silica-containing material, impregnated with an aqueous solution of an alkali metal silicate, and fired at 650-1220 DEG F. The molecular sieve may be naturally occurring (exs. given) or synthetic, e.g. A, T, X, Y, and is agglomerated alone or with water and 5-35% of a binder, e.g. silicates and/or clays (exs. given), to give spheres of size 8-12 mesh. The coating may be from 1 to .003 ins. thick, and may be of clay e.g. attapulgite (others are listed), asbestos, mica, quartz glass frits or enamels, preferably less than 300 mesh (U.S.S.) in size. It is applied to the damp agglomerates by tumbling together, or by spraying with an aqueous dispersion. The impregnant may be Na, K, Li, Rb or Cs silicate with a M2O/SiO2 weight ratio of 0.27-0.63 and a solids content of 3-35 wt. %, and may contain colloidal silica. Contact, with 0.07-0.73 pts. solution solids per pt. agglomerate, may be effected at below 60 DEG C either batchwise with agitation, or continuously by percolating the solution through the agglomerates. The agglomerates may then be dried at 180-350 DEG F to a moisture content of 15-22% b.w. before firing. Reference has been directed by the Comptroller to Specification 972833.