Asymmetric hollow-fiber gas separation membrane, gas separation method and gas separation membrane module

1. An asymmetric hollow-fiber gas separation membrane comprising a polyimide, and having an improved tensile elongation at break of 15% or more as a hollow-fiber membrane itself,

the polyimide comprising a repeating unit substantially represented by the following general formula (1):

wherein,

20 to 80 mol % of A is a tetravalent unit based on the biphenyl structure represented by the formula (2),

20 to 80 mol % of A is a tetravalent unit based on the diphenylhexafluoropropane represented by the formula (3),

0 to 30 mol % of A is a tetravalent unit based on the phenyl structure represented by the formula (4),

30 to 70 mol % of R is a divalent unit represented by the formula (5) and/or formula (6),

wherein, in formula (5), each of R1 and R2 is a hydrogen atom or organic group, and n is any number of 0, 1 and 2, and in formula (6), each of R1 and R2 is a hydrogen atom or organic group, and X is —CH 2 — or —CO—, and

30 to 70 mol % of R is a divalent unit based on the biphenyl structure represented by the formula (7),

wherein, in formula (7), Y is a chlorine or bromine atom, and n is any number of 1 to 3.

2. The asymmetric hollow-fiber gas separation membrane according to claim 1 , having an oxygen gas permeation rate P′ O2 of 4.0×10 −5 cm 3 (STP)/cm 2 ·sec·cmHg or more and a gas ratio of permeation rate of oxygen to nitrogen P′ O2 /P′ N2 of 4 or more that are measured at 50° C.

3. A gas separation method comprising:

contacting a mixed gas containing oxygen gas and nitrogen gas to a gas supply side of the asymmetric hollow-fiber gas separation membrane according to claim 1 ,

selectively permeating the oxygen gas to a gas permeation side of the asymmetric hollow-fiber gas separation membrane, and

separating and recovering an oxygen-enriched mixed gas and a nitrogen-enriched mixed gas from the mixed gas.

4. The gas separation method according to claim 3 , wherein a bore-side of the asymmetric hollow-fiber gas separation membrane is selected as the gas supply side and the outside of the asymmetric hollow-fiber gas separation membrane is selected as the gas permeation side.

5. A hollow-fiber gas separation membrane module comprising:

a hollow-fiber element essentially comprising a hollow-fiber bundle formed by binding a number of the asymmetric hollow-fiber gas separation membranes according to claim 1 , the hollow-fiber element accommodated in a vessel in such a manner that a bore-side space of the asymmetric hollow fiber gas separation membrane is isolated from an outside room of the membrane, and

a tube plate embedding and fixing at least one end of the hollow-fiber bundle while each end is opened,

the vessel having an inlet for mixed gas, an outlet for non-permeated gas, and an outlet for permeated gas.

6. An asymmetric hollow-fiber gas separation membrane obtained by heating the asymmetric hollow-fiber gas separation membrane according to claim 1 at a maximum temperature in the range of 350° C. to 450° C.

7. A gas separation method comprising:

contacting a mixed gas enriched with an organic compound vapor to a gas supply side of the asymmetric hollow-fiber gas separation membrane according to claim 6 ,

permeating selectively the organic compound vapor to a gas permeation side of the asymmetric hollow-fiber gas separation membrane, and

separating and recovering the mixed gas enriched with an organic compound vapor.

8. A hollow-fiber gas separation membrane module comprising:

a hollow-fiber element essentially comprising a hollow-fiber bundle formed by binding a number of the asymmetric hollow-fiber gas separation membranes according to claim 6 , the hollow-fiber element accommodated in a vessel in such a manner that a bore-side space of the asymmetric hollow-fiber gas separation membranes is isolated from an outside room of the membrane, and

a tube plate embedding and fixing at least one end of the hollow-fiber bundle while each end is opened,

the vessel having an inlet for mixed gas, an outlet for non-permeated gas, and an outlet for permeated gas.

9. A gas separation method comprising:

contacting a mixed gas containing oxygen gas and nitrogen gas to a gas supply side of the asymmetric hollow-fiber gas separation membrane according to claim 2 ,

selectively permeating the oxygen gas to a gas permeation side of the asymmetric hollow-fiber gas separation membrane, and

separating and recovering an oxygen-enriched mixed gas and a nitrogen-enriched mixed gas from the mixed gas.

10. The gas separation method according to claim 9 , wherein a bore-side of the asymmetric hollow-fiber gas separation membrane is selected as the gas supply side and the outside of the asymmetric hollow-fiber gas separation membrane is selected as the gas permeation side.

11. A hollow-fiber gas separation membrane module comprising:

a hollow-fiber element essentially comprising a hollow-fiber bundle formed by binding a number of the asymmetric hollow-fiber gas separation membranes according to claim 2 , the hollow-fiber element accommodated in a vessel in such a manner that a bore-side space of the asymmetric hollow-fiber gas separation membranes is isolated from an outside room of the membranes, and

a tube plate embedding and fixing at least one end of the hollow-fiber bundle while each end is opened,

the vessel having an inlet for mixed gas, an outlet for non-permeated gas, and an outlet for permeated gas.

12. An asymmetric hollow-fiber gas separation membrane obtained by heating the asymmetric hollow-fiber gas separation membrane according to claim 2 at a maximum temperature in the range of 350° C. to 450° C.

13. A gas separation method comprising:

contacting a mixed gas containing an organic compound vapor to the gas supply side of the asymmetric hollow-fiber gas separation membrane according to claim 12 ,

permeating selectively the organic compound vapor to a gas permeation side of the asymmetric hollow-fiber gas separation membrane, and

separating and recovering the mixed gas enriched with an organic compound vapor.

14. A hollow-fiber gas separation membrane module comprising:

a hollow-fiber element essentially comprising a hollow-fiber bundle formed by binding a number of the asymmetric hollow-fiber gas separation membranes according to claim 12 , the hollow-fiber element accommodated in a vessel in such a manner that a bore-side space of the asymmetric hollow-fiber gas separation membranes is isolated from the outside room thereof, and

a tube plate embedding and fixing at least one end of the hollow-fiber bundle while each end is opened,

the vessel having an inlet for mixed gas, an outlet for non-permeated gas, and an outlet for permeated gas.