Synthetic zeolites

摘要

Zeolite embedded in a silica gel or a silica-metal oxide cogel matrix is prepared by crystallizing the zeolite from an aqueous reaction mixture containing Na2O, SiO2 and Al2O2 to form a product slurry of zeolite and mother liquor. This slurry is then mixed with either an aqueous silica slurry or with an aqueous cogel slurry of silica and at least one other hydrano oxide of a metal of Group IIa, IIIb or IVa of the Mendelaeef Periodic Table (e.g. Al2O3) to form a fluid admixture. The latter is then subjected to a rapid drying operation (e.g. spray drying) to yield a composite material comprising the zeolite embedded in the silica gel or cogel matrix. The zeolite may have the following molar ratio of constituents: 0.9/sB0.2 Na2O: Al2O3: XSiO2 where x has a value > 3 and in which the molar ratios of the constituents are in the following ranges: .Na2O:SiO2.0.25 to 0.60 .SiO2:Al2O3.4 to less than 8 .H2O:Na2O.20 to 40 .Na2O:Al2O3.1.6 to 3.5 The initial reaction may be carried out at 180-250 DEG F. and the reaction mixture maintained at this temperature for a time sufficient to crystallize the zeolite. The dried zeolite may be subjected to base exchange with an aqueous soln. of an ion capable of reducing the Na2O content to less than 10 wt. per cent based on the weight of zeolite. Examples of such ions are hydrogen-containing cations, cations of metals of Groups II, III, IV, V, VIb, VIIb and VIII of the Periodic Table, and cations of the rare earth metals.ALSO:Cracking catalysts consist of zeolite embedded in a matrix of silica gel or in a silica-metal oxide cogel matrix. Specified oxides are those of metals of groups IIA, IIIB or IVA of the periodic table (Mendeleef) (e.g. Al2O3) to form a fluid mixture which is then subjected to a rapid drying operation (e.g. spray drying) to form a composite material comprising zeolite embedded in either a silica or silica-metal oxide cogel matrix. The Zeolite may have the following molar ration of constituents: The dried zeolite matrix may be subjected ot a base exchange with cations of metals of Groups II, III, IV, V, VI B, VIIB and VIII of the Periodic Table and cations of the rare earth metals.