Gas separation membrane
A gas separation membrane that separates, by selective transmission, carbon dioxide from a mixed gas containing the carbon dioxide and nitrogen, the gas separation membrane including: a first layer; and a second layer provided at one surface of the first layer and composed of a compound having carbon dioxide separation ability, wherein an average thickness of the second layer is smaller than an average thickness of the first layer, and the second layer satisfies 0.56<ξ 2 , where an activity coefficient of nitrogen in the second layer, calculated by the COSMO-RS method, is γ 2 N2 , an activity coefficient of carbon dioxide in the second layer is γ 2 CO2 , and a separation performance parameter of the second layer at 25° C. is ξ 2 =ln(γ 2 N2 )−ln(γ 2 CO2 ).
1 . A gas separation membrane that separates, by selective transmission, carbon dioxide from a mixed gas containing the carbon dioxide and nitrogen, the gas separation membrane comprising:
a first layer, wherein the first layer includes an organopolysiloxane; and
a second layer provided at one surface of the first layer and composed of a compound having carbon dioxide separation ability, wherein
the compound of the second layer includes one of:
a structure derived from one of polyethylene terephthalate, polyacetal polylactic acid, cellulose, a cellulose derivative, lignin, or a coupling agent, or
a polydimethylsiloxane derivative,
an average thickness of the second layer is smaller than an average thickness of the first layer, and
the second layer satisfies 0.56<ξ 2 , where an activity coefficient of nitrogen in the second layer, calculated by a COSMO-RS method, is γ 2 N2 , an activity coefficient of carbon dioxide in the second layer is γ 2 CO2 , and a separation performance parameter of the second layer at 25° C. is ξ 2 =ln(γ 2 N2 )−ln(γ 2 CO2 ).
2 . The gas separation membrane according to claim 1 , wherein
the first layer and the second layer satisfy ξ 1 <ξ 2 , where an activity coefficient of nitrogen in the first layer, calculated by the COSMO-RS method, is γ 1 N2 , an activity coefficient of carbon dioxide in the first layer is γ 1 CO2 , and a separation performance parameter of the first layer at 25° C. is ξ 1 =ln(γ 1 N2 )−ln(γ 1 CO2 ).
3 . The gas separation membrane according to claim 2 , wherein the first layer and the second layer satisfy 0.10≤ξ 2 −ξ 1 .
4 . The gas separation membrane according to claim 1 , wherein
in the polydimethylsiloxane derivative, one of hydrogen atoms of some of methyl groups included in polydimethylsiloxane is substituted with a substituent, and
the substituent is an amino group, a cyano group, or a phenyl group.
5 . The gas separation membrane according to claim 1 , wherein
in the polydimethylsiloxane derivative, one of hydrogen atoms of some of methyl groups included in polydimethylsiloxane is substituted with a substituent, and
the substituent is derived from an organic compound having a π-conjugated cyclic structure.
6 . The gas separation membrane according to claim 1 , wherein
in the polydimethylsiloxane derivative, one of hydrogen atoms of some of methyl groups included in polydimethylsiloxane is substituted with a substituent, and
the substituent includes an ester bond and an aromatic ring.
7 . The gas separation membrane according to claim 1 , wherein
the average thickness of the second layer is 1 nm or more and 100 nm or less.
8 . The gas separation membrane according to claim 1 , wherein
the average thickness of the first layer is 10 μm or more and 150 μm or less.
9 . The gas separation membrane according to claim 1 , wherein
the compound includes the polydimethylsiloxane derivative in which one of hydrogen atoms of some of methyl groups included in polydimethylsiloxane is substituted with a substituent, and
the substituent includes an ester bond and an aromatic ring.