Chemistry of inorganic compounds – Phosphorus or compound thereof – Oxygen containing
Patent
1996-02-12
1997-03-11
Geist, Gary
Chemistry of inorganic compounds
Phosphorus or compound thereof
Oxygen containing
4233271, 502214, 518728, C01B 2536
Patent
active
056098430
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a crystalline silico-alumino-phosphate (SAPO) with an AEI structure, which has acidic properties, and a procedure for manufacturing it. The present invention particularly concerns the manufacture of the new silico-alumino-phosphate RUW-18.
Microporous crystalline silico-alumino-phosphates and a procedure for manufacturing such products are, for example, mentioned in Norwegian patent no. 169380. These products have a three-dimensional crystal lattice built up of PO.sub.2 +, AlO.sub.2 -tetrahedron units in which SiO.sub.2 tetrahedron units are substituted for PO.sub.2 + and the empirical chemical composition of which, on a water-free basis, is: the intercrystalline pore system and m means the number of mol R which are present per mol (Si.sub.x Al.sub.y P.sub.z) O.sub.2 and has a value from 0 to 0.3. The sum of x, y and z equals 1, and the minimum value for "x" is 0.005, the minimum value for "y" and "z" is 0.01, and the maximum value for "x" is 0.98, for "y" 0.6 and for "z" 0.52.
Reaction mixtures for silico-alumino-phosphate are made by combining at least a proportion of each of the aluminium and phosphorus sources with water, where the silicon source is mainly absent. Subsequently, the resulting mixture reacts with a silicon source and then with an organic compound. The mixing sequence is critical only in some cases.
The reaction mixture is placed in a pressure container for heating under autogenous pressure to a temperature of at least 100.degree. C., preferably between 100.degree. and 260.degree. C., until a crystalline silico-alumino-phosphate is obtained. The solid substance is recovered in any appropriate way, for example by centrifuging or filtering. The recovered substance is dried and calcinated in the presence of air.
During calcination the organic template material R will be combusted and in those cases where it occurs as a charge-compensating cation, there will be an H.sup.+ ion left behind as a new charge-compensating ion. This will be the case for silico-alumino-phosphates, which will thus gain acidic properties after calcination.
Of the known silico-alumino-phosphates, molecular sieves with a three-dimensional pore structure with 8-ring pores will be the most interesting for gas separation and the production of olefins from methanol. SAPO-34 and SAPO-17 can be mentioned as known silico-alumino-phosphates (SAPO) with this structure.
The AEI structure is described by Simmen et al., 1991: Zeolites 11, 654. This structure has a three-dimensional pore network with pore openings of approximately 4-5 .ANG. and with cavities, the smallest dimensions of which are >5 .ANG.. The crystals are usually plate-shaped. The effective diameter of the crystallite is small and there will be a short diffusion path into the centre of the crystallite. Silico-alumino-phosphates with an AEI structure have not previously been known.
Crystalline alumino-phosphates with an AEI structure have previously been produced (U.S. Pat. No. 4,310,440), but they do not possess acidic properties because the crystal lattice is electrically neutral. They cannot, therefore, be used as catalysts in reactions where acidity is required, for example for converting methanol to olefins. The properties as a sorbent will also be different for molecular sieves with and without acidic properties. An acidic molecular sieve will be polarised and thus have greater sorption capacity.
The object of the present invention is to manufacture a crystalline silico-alumino-phosphate with acidic properties and with a pore structure which is made of channels with a diameter between 4 and 5 .ANG. and with "cavities", the smallest size of which is >5 .ANG.. Another object is to manufacture a material which can be used as catalysts or sorbents in a wide range of contexts, for example for the manufacture of olefins from methanol.
These and other objects of the present invention are achieved with the product and the procedure described below and the present invention is defined and characterised by the patent claims.
The presen
REFERENCES:
patent: 4310440 (1982-01-01), Wilson et al.
patent: 4440871 (1984-04-01), Lok et al.
Geist Gary
Norsk Hydro a.s
Padmanabhan Sreeni
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