Porous amorphous silica-alumina refractory oxides, their preparation and use as separation membranes
AssigneeBritish Gas Corporation
InventorsStephen David Jones, Timothy Neil Pritchard
Life of this patent
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Abstract
A process for preparing a porous amorphous silica-alumina refractory oxide is described in which a source of silica, such as tetra ethyl ortho silicate, in a non-aqueous solvent, such as an alcohol, is hydrolysed by adding an aqueous solution containing aluminum ions, in particular a solution of aluminum nitrate, thereby to form a sol and calcining the sol at, for example, 200.degree. C. to 600.degree. C. The product, which may have a microporous or mesoporous structure, is useful in the separation of fluids, especially the separation of carbon dioxide from natural gas.
Claims12
A process for preparing a porous amorphous silica-alumina refractory oxide comprising the steps of:
- (i) forming a solution of tetraethyl orthosilicate in a non-aqueous solvent selected from monohydric alcohols having from 1 to 4 carbon atoms and mixtures thereof, the volume ratio of said tetraethyl orthosilicate to said non-aqueous solvent being from 1:1 to 1:5;
- (ii) forming an aqueous solution of aluminum nitrate;
- (iii) hydrolyzing said solution of tetraethyl orthosilicate by adding thereto said aqueous solution of aluminum nitrate, thereby to form a sol having a viscosity of from 1 to 10 mPas, and
- (iv) calcining said sol at a temperature of from 200.degree. C. to 600.degree. C. to form a calcined product having a modal pore diameter of about 3 to 20 .ANG. and a porosity of between 10 and 70%,
- said aqueous solution of aluminum nitrate and said solution of tetraethyl orthosilicate being used in such concentrations and relative proportions that said calcined product contains at least 80% by weight silica, calculated as SiO.sub.2.
A process for preparing a fluid separation membrane comprising a porous amorphous refractory oxide on a porous support, comprising the steps of:
- (I) forming a solution of tetraethyl orthosilicate in a non-aqueous solvent selected from monohydric alcohols having from about 1 to 4 carbons and mixtures thereof, the volume ratio of said tetraethyl orthosilicate to said non-aqueous solvent being from 1:1 to 1:5;
- (ii) forming an aqueous solution of aluminum nitrate;
- (iii) hydrolyzing said solution of tetraethyl orthosilicate by adding thereto said aqueous solution of aluminum nitrate, thereby to from a sol having a viscosity from 1 to 10 mPas:
- (iv) coating said porous substrate with said sol, and
- (v) calcining the coated substrate at a temperature of from 200.degree. C. to 600.degree. C. to from said membrane, the sol forming a calcined product having a modal pore diameter of about 3-20 .ANG. and a porosity of between 10 and 70%,
- said aqueous solution of aluminum nitrate and said solution of tetraethyl orthosilicate being sued in such concentrations and relative proportions the said calcined product contains at least about 80% by weight silica, calculated as SiO.sub.2.
Dependencies are inferred from the claim text.