Removal of a gas component present in a gaseous stream

Claim 2

A membrane suitable for absorbing a gas component present in a gaseous stream, which comprises: a porous layer of hydrophilic material, both faces of which are covered by a layer of a mixture of 10 to 90% by weight of a hydrophobic substance and 90 to 10% by weight of a hydrophilic substance, the hydrophilic portions of the three layers being impregnated with a catalyst which permits the conversion of carbon dioxide to bicarbonate ions and the decomposition of bicarbonate to gaseous carbon dioxide, and with an alkali metal buffer solution of 12 to 14N, said catalyst being selected from the group consisting of meta arsenites, antimonites and bismuthites, arsenious oxide, antimony oxide and bismuth oxide, potassium selenite, tellurite and metaborate, sodium selenite, tellurite and metaborate, selenious acid and a mixture of boric acid and diethanolamine, the concentration of said catalyst being 0.1 to 3M.

Claim 3

A membrane according to claim 1 wherein the layer which is a mixture of hydrophobic and hydrophilic substances is a mixture of polytetrafluoroethylene and carbon black.

Claim 4

A membrane according to claim 2 wherein the porous layer of hydrophilic material is a porous fibrous material.

Claim 5

A membrane according to claim 2 wherein the porous layer of hydrophilic material is 50 to 200 μm thick.

Claim 6

A membrane according to claim 1 wherein the amount of hydrophilic substance in the mixture of hydrophilic and hydrophobic substances is 70-90 wt.%.

Claim 7

A membrane according to claim 2 wherein the thickness of each outer layer is 25 to 200μm .

Claim 8

A membrane according to claim 1 wherein the buffer solution is KHCO 3 /K 2 CO 3 or CsHCO 3 /Cs 2 CO 3 .

Claim 9

A membrane according to claim 2 wherein the catalyst and alkali metal buffer solution are mixed with potassium or caesium fluorides.

Claim 10

A membrane according to claim 8 wherein the ratio of the molar concentration of KF to CsF to alkali metal in the buffer solution is from 4:1 to 1:2.

Claim 11

A membrane according to claim 1 wherein the catalyst is a meta arsenite.

Claim 12

A membrane according to claim 1 wherein the catalyst is a mixture of boric acid and diethanoamine.

Claim 13

A process for absorbing carbon dioxide from a gaseous stream containing it utilizing a catalyst which permits the conversion of carbon dioxide to bicarbonate ions and the decomposition of bicarbonate to gaseous carbon dioxide, which comprises: causing said gaseous stream to flow adjacent to a humidified stripping gas having a relative humidity of 0.45 to 0.95, the flows of said gaseous stream and said stripping gas being separated by a membrane comprising a porous layer of hydrophilic material, both faces of which are covered by a layer of a mixture of 10 to 90% by weight of a hydrophobic substance and 90 to 10% by weight of a hydrophilic substance, the hydrophilic portions of the three layers being impregnated with a catalyst which permits the conversion of carbon dioxide to bicarbonate ions and the decomposition of bicarbonate to gaseous carbon dioxide, and with an alkali metal buffer solution of 2 to 14N, said catalyst being selected from the group consisting of meta arsenites, antimonites and bismuthites, arsenious oxide, antimony oxide and bismuth oxide, potassium selenite, tellurite and metaborate, sodium selenite, tellurite and metaborate, selenious acid and a mixture of boric acid and diethanolamine, the concentration of said catalyst being 0.1 to 3M.

Claim 14

A process for absorbing carbon dioxide from a gaseous stream containing it utilizing a catalyst which permits the conversion of carbon dioxide to bicarbonate ions and the decomposition of bicarbonate to gaseous carbon dioxide, which comprises: causing said gaseous stream to flow adjacent to a humidified stripping gas having a relative humidity of 0.45 to 0.95, the flows of said gaseous stream and said stripping gas being separated by a membrane comprising a porous layer of hydrophilic material, both faces of which are covered by a layer of a mixture of 10 to 90% by weight of a hydrophobic substance and 90 to 10% by weight of a hydrophilic substance, the hydrophilic portions of the three layers being impregnated with a catalyst which permits the conversion of carbon dioxide to bicarbonate ions and the decomposition of bicarbonate to gaseous carbon dioxide, and with an alkali metal buffer solution of 2 to 14N, said catalyst being selected from the group consisting of meta arsenites, antimonites and bismuthites, arsenious oxide, antimony oxide and bismuth oxide, potassium selenite, tellurite and metaborate, sodium selenite, tellurite and metaborate, selenious acid and a mixture of boric acid and diethanolamine, the concentration of said catalyst being 0.1 to 3M.

Claim 15

A process according to claim 12 wherein the stripping gas is nitrogen or air.

Claim 16

A process according to claim 12 wherein the flow rate of stripping gas is 2 to 5 times that of the gaseous stream.

Claim 17

A process according to claim 12 wherein the gaseous stream is reformer gas.

Claim 18

A process according to claim 12 wherein the layer which is a mixture of hydrophobic and hydrophilic substances is a mixture of polytetrafluoroethylene and carbon black.

Claim 19

A process according to claim 16 wherein the porous layer of hydrophilic material is a porous fibrous material.

Claim 20

A process according to claim 16 wherein the porous layer of hydrophilic material is 5 to 200 μm thick.

Claim 21

A process according to claim 12 wherein the amount of hydrophilic substance in the mixture of hydrophilic and hydrophobic substances is 70-90 wt.%.

Claim 22

A process according to claim 16 wherein the thickness of each outer layer is 25 to 200 μm.

Claim 23

A process according to claim 12 wherein the buffer solution is KHCO 3 /K 2 CO 3 or CsHCO 3 /Cs 2 CO 3 .

Claim 24

A process according to claim 16 wherein the catalyst and alkali metal buffer solution are mixed with potassium or caesium fluorides.

Claim 25

A process according to claim 22 wherein the ratio of the molar concentration of KF or CsF to alkali metal in the buffer solution is from 4:1 to 1:2.

Claim 26

A process according to claim 12 wherein the catalyst is a meta arsenite.

Claim 27

A process according to claim 12 wherein the catalyst is a mixture of boric acid and diethanolamine.