Chemistry of inorganic compounds – Zeolite
Patent
1997-07-28
1999-05-18
Bell, Mark L.
Chemistry of inorganic compounds
Zeolite
423709, 4233282, C01B39/28
Patent
active
059049146
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention describes the preparation of alkali metal aluminosilicates, in particular crystalline aluminosilicates having the P-structure. These materials are of value as a component in detergent formulations in which they remove calcium and magnesium hardness ions by ion exchange. They also have other properties which provide additional benefits when used in detergent formulations. These aluminosilicates will be referred to as zeolite P in this description.
BACKGROUND OF THE INVENTION
While the utility of zeolite P in detergent formulations has been acknowledged, for example in European Patent Application 0384070 (Unilever), they must be manufactured by a commercially effective process in order to become available on the market place. Thus, while the properties of a material may make it a useful commercial commodity, its manufacture has to be optimised for large scale production. The zeolite P class includes a series of synthetic zeolite phases which may be in cubic configuration (also termed B or P.sub.c) or tetragonal configuration (also termed P.sub.1) but is not limited to these forms. The structure and characteristics of the zeolite P class are given in "Zeolite Molecular Sieves" of Donald W Breck (published 1974 and 1984 by Robert E Krieger of Florida USA). The zeolite P class has the typical oxide formula: is lithium, potassium, sodium, caesium or rubidium with sodium and potassium being preferred and sodium being the cation normally used in commercial processes.
Thus sodium may be present as the major cation with another alkali metal present in a minor proportion to provide a specific benefit.
In EP-A-384,070 is disclosed a process for manufacturing zeolite P having a silicon to aluminium molar ratio not exceeding 1.33 wherein a sodium aluminate solution, having a Na.sub.2 O:Al.sub.2 O.sub.3 molar ratio from 1.4 to 2.0, is mixed with a sodium silicate solution, having a SiO.sub.2 :Na.sub.2 O molar ratio from 0.8 to 3.4, at a temperature from 25.degree. C. to boiling point and with vigorous stirring to give a gel having the following composition: O.
The gel is then aged for 0.5 to 10 hours at a temperature above 70.degree. C., the crystalline sodium aluminosilicate thus formed being then washed and dried.
This process, with such a gel composition, even though being suitable for producing zeolite P on a bench scale, can't always be directly transposed to industrial scale.
In EP-A-565,364 is disclosed a process for industrial production of P zeolite having the oxide formula yH.sub.2 O C. is mixed with a sodium silicate solution at a temperature of at least 25.degree. C. in a stirred vessel in the presence of a slurry of P zeolite seed to form a gel having the composition, Al.sub.2 O.sub.3 :(1-3.5)(preferably 1.80-2.2)SiO.sub.2 :(1.2-7.5) (preferably 1.5-5)Na.sub.2 O: (25 to 450) (preferably 40 to 150) H.sub.2 O to maintain solids in suspension for a period of least about 0.1 hour, and
Even though satisfactory, this process is a batch process and there is therefore a need for a continuous process for the production of zeolite P.
STANDARD PROCEDURES
In the characterisation of the zeolite-P materials prepared by the present process the following methods were used. standard XRD method.
GENERAL DESCRIPTION OF THE INVENTION
It is a first object of the present invention to provide a process for manufacturing an alkali metal aluminosilicate of zeolite P type having the oxide formula continuously added together in a first reacting zone in the presence of zeolite P seeds, to produce a mixture having the general formula: a second reacting zone, the resulting product being eventually filtered, washed and dried.
Preferably, the invention relates to a process for manufacturing an alkali metal aluminosilicate of zeolite P type having the oxide formula
By reacting zone it is understood a reacting vessel or a zone of a plug flow reactor as for example marketed by Power Fluidics, AEA Technology, Risley, Warrington, U.K.
In such a process, it is necessary, in order to work under viabl
REFERENCES:
patent: 3071434 (1963-01-01), Frilette et al.
patent: 4385042 (1983-05-01), Whitehurst et al.
patent: 5560829 (1996-10-01), Adams et al.
patent: 5645811 (1997-07-01), Kuhm et al.
Bell Mark L.
Crosfield Limited
Sample David
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