Production of porous inorganic materials

Claim 1

A method of preparing a porous material which method comprises: (a) forming hollow microspheres, each having a shell defining an internal cavity, of an aluminosilicate material having an SiO 2 : Al 2 O 3 molar ratio of at least 0.75:1; (b) calcining the hollow microspheres formed in step (a) at a temperature in the range of from 1300° C. to 1800° C. for at least one hour; (c) treating the calcined hollow units with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50° C. whereby the silica is removed to leave ceramic crystals which define between them interconnecting pores; (d) washing the alkali metal hydroxide treated hollow microspheres formed in step (c) until the washing medium is substantially free of silicate and alkali metal ions; and (e) dewatering and drying the washed product obtained in step (d) to obtain microspheres with a shell of the desired porous nature, said shell of each microsphere being pierced by at least one aperture providing access to the cavity, the or each aperture having a diameter such that the ratio of the diameter of the aperture to the diameter of the cavity into which the aperture opens is in the range of from 0.1:1 to 1:1.

Claim 2

A method of preparing a porous material which method comprises: (a) forming hollow microspheres, each having a shell defining an internal cavity, of an aluminosilicate material having an SiO 2 : Al 2 O 3 molar ratio of at least 0.75:1; (b) calcining the hollow microspheres formed in step (a) at a temperature in the range of from 1300° C. to 1800° C. for at least one hour; (c) treating the calcined hollow units with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50° C. whereby the silica is removed to leave ceramic crystals which define between them interconnecting pores; (d) washing the alkali metal hydroxide treated hollow microspheres formed in step (c) until the washing medium is substantially free of silicate and alkali metal ions; and (e) dewatering and drying the washed product obtained in step (d) to obtain microspheres with a shell of the desired porous nature, said shell of each microsphere being pierced by at least one aperture providing access to the cavity, the or each aperture having a diameter such that the ratio of the diameter of the aperture to the diameter of the cavity into which the aperture opens is in the range of from 0.1:1 to 1:1.

Claim 5

A method of preparing a porous material which method comprises: (a) forming a foam from a suspension containing from 20% to 60% by weight of solid aluminosilicate material and drying the wet foam to form a substantially rigid cellular body comprising a plurality of cavities separated by aluminosilicate walls; (b) calcining the cellular body at a temperature in the range of from 1300° to 1800° for at least 1 hour; (c) treating the calcined foam with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50° C. whereby the silica is removed to leave ceramic crystals which define them interconnecting pores; (d) washing the alkali metal hydroxide treated foam formed in step (c) until the washing medium is substantially free of silicate and alkali metal ions; and (e) dewatering and drying the washed product obtained in step (d) to obtain a cellular material with a structure of the desired porous nature in which the walls of the product are pierced by apertures providing access to the cavities, the apertures each having a diameter such that the ratio of the diameter of the aperture to the diameter of the cavity into which the aperture opens is in the range of from 0.1:1 to 1:1.

Claim 6

A method of preparing a porous material which method comprises: (a) forming a foam from a suspension containing from 20% to 60% by weight of solid aluminosilicate material and drying the wet foam to form a substantially rigid cellular body comprising a plurality of cavities separated by aluminosilicate walls; (b) calcining the cellular body at a temperature in the range of from 1300° to 1800° for at least 1 hour; (c) treating the calcined foam with a concentrated aqueous solution of an alkali metal hydroxide at a temperature of at least 50° C. whereby the silica is removed to leave ceramic crystals which define them interconnecting pores; (d) washing the alkali metal hydroxide treated foam formed in step (c) until the washing medium is substantially free of silicate and alkali metal ions; and (e) dewatering and drying the washed product obtained in step (d) to obtain a cellular material with a structure of the desired porous nature in which the walls of the product are pierced by apertures providing access to the cavities, the apertures each having a diameter such that the ratio of the diameter of the aperture to the diameter of the cavity into which the aperture opens is in the range of from 0.1:1 to 1:1.