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An apparatus and method to separate a mixture of gases--such as carbon dioxide and methane--by an inorganic membrane comprising a ceramic support and a silica layer made from a silicon elastomer sol. The apparatus and method can efficiently separate the gaseous mixture and can also cope with the ext

An apparatus and method to separate a mixture of gases--such as carbon dioxide and methane--by an inorganic membrane comprising a ceramic support and a silica layer made from a silicon elastomer sol. The apparatus and method can efficiently separate the gaseous mixture and can also cope with the extreme conditions found in e.g. hydrocarbon producing wells. A method of manufacturing the apparatus is also disclosed.

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What is claimed is: 1. An apparatus to separate at least one first gas from a mixture comprising the at least one first gas and at least one second gas, the apparatus comprising a ceramic membrane comprising: a support portion; and, a separating portion comprising a silica separation portion, the s

What is claimed is: 1. An apparatus to separate at least one first gas from a mixture comprising the at least one first gas and at least one second gas, the apparatus comprising a ceramic membrane comprising: a support portion; and, a separating portion comprising a silica separation portion, the separating portion adapted to permit passage of the at least one first gas therethrough whilst substantially preventing passage of the at least one second gas therethrough; wherein the silica separating portion has been prepared from a sol comprising a silicon elastomer by drying the sol. 2. An apparatus as claimed in claim 1, wherein the sol further comprises isopentane. 3. An apparatus as claimed in claim 1, wherein the sol further comprises a curing agent. 4. An apparatus as claimed in claim 1, wherein the ceramic membrane comprises at least one tube having a bore. 5. An apparatus as claimed in claim 4, wherein the at least one tube is corrugated or coiled. 6. An apparatus as claimed in claim 4, wherein the at least one tube comprises an inner tube provided within an impermeable second outer tube and the mixture comprising the at least one first gas and at least one second gas is injected into an annulus between the inner and outer tubes. 7. Apparatus as claimed in claim 6, wherein a graphite seal mounts the inner tube in the outer tube. 8. Apparatus as claimed in claim 1, wherein the separating portion also comprises a layer of gamma alumina. 9. Apparatus as claimed in claim 8, wherein the layer of gamma alumina is provided on the support portion and the silica separating portion is provided on the layer of gamma alumina. 10. A method of manufacturing apparatus comprising a ceramic membrane comprising a separating portion comprising a silica separation portion to separate at least one first gas from a mixture comprising the at least one first gas and at least one second gas, the method comprising providing a support portion; and forming the silica separation portion by immersing the support portion in a sol comprising a silicon elastomer, removing the support portion from the sol, and converting the silicon elastomer to silica while allowing the support to dry, the separating portion adapted to permit passage of the at least one first gas therethrough whilst substantially preventing passage of the at least one second gas therethrough. 11. A method as claimed in claim 10, wherein the sol further comprises isopentane. 12. A method as claimed in claim 10, wherein the sol further comprises a curing agent. 13. A method as claimed in claim 10, wherein the sol is permitted to age over a period of 5-30 minutes before immersing the support in the sol. 14. A method as claimed in claim 10, wherein the support is immersed in the sol for a period of approximately 20 minutes. 15. A method as claimed in claim 10, wherein the support is allowed to dry by applying heat. 16. A method as claimed in claim 15, wherein the support is dried at 65째 C. for twenty four hours. 17. A method as claimed in claim 10, wherein the following steps of the method immersing the support in a sol; removing the support from the sol; and allowing the support to dry; are repeated at least once. 18. A method as claimed in claim 10 which is repeated to coat the support with a second sol. 19. A method to separate at least one first gas from a mixture comprising the at least one first gas and at least one second gas, the method comprising the steps of bringing said mixture into contact with a ceramic membrane comprising: a support portion; and, a separating portion comprising a silica separating portion, the separating portion adapted to permit passage of the at least one first gas therethrough whilst substantially preventing passage of the at least one second gas therethrough; wherein the silica separating portion has been prepared from a sol comprising a silicon elastomer by a process that comprises forming the silica from the silicon elastomer by drying the sol; such that the at least one first gas passes through the ceramic membrane whilst passage of the at least one second gas through the ceramic membrane is substantially prevented. 20. A method as claimed in claim 19, which is performed in a downhole environment. 21. A method as claimed in claim 19, wherein the at least one first gas and the at least one second gas are recovered for subsequent use. 22. An apparatus to separate at least one first gas from a mixture comprising the at least one first gas and at least one second gas, the apparatus comprising a first tube and a second tube, the first tube comprising a ceramic membrane which comprises: a support portion; and, a separating portion comprising a silica separating portion, the separating portion adapted to permit passage of the at least one first gas through the ceramic membrane whilst substantially preventing passage of the at least one second gas through the ceramic membrane; wherein the silica separating portion has been prepared from a sol comprising a silicon elastomer by a process that comprises the silica being formed from the silicon elastomer while the sol is permitted to dry, the first tube being mounted substantially within the second tube and being sealed therein by a graphite seal.