Process and absorbent for dehumidifying moist gas mixtures

1. A process for dehumidifying a moist gas mixture G 1 , wherein the moist gas mixture G 1 is contacted with a liquid absorption medium A 1 , which comprises a mixture of at least one trialkyl phosphate of structure (I):

and at least one salt S selected from the group consisting of Q + A − , Q + (R 1 O) 2 PO 2 − , (Q + ) 2 R 2 OPO 3 2 − , and Q + M + R 3 OPO 3 2 − , to obtain a gas mixture G 2 which has a lower water content compared to the moist gas mixture G 1 and a liquid absorption medium A 2 which has an elevated water content compared to the liquid absorption medium A 1 ; wherein:

a) Q + is a dialkylimidazolium cation;

b) A − is an anion selected from the group consisting of R*COO − , R′SO 3 − , HSO 4 − , and R″SO 4 − ;

c) R*, R′, R″, R A , R B , R C are each independently an alkyl group;

d) R 1 , R 2 , R 3 are each independently an alkyl group; and

e) M + is an alkali metal ion.

2. The process of claim 1 , wherein:

a) Q + is a dialkylimidazolium cation, in which the alkyl groups each independently have 1 to 10 carbon atoms;

b) R*, R′, R″, R A , R B , R C , R 1 , R 2 , R 3 are each independently an alkyl group having 1 to 10 carbon atoms; and

c) M + =Li + , K + or Na + .

3. The process of claim 1 , wherein:

a) salt S is selected from the group of: Q + A − , and Q + (R 1 O) 2 PO 2 − ;

b) Q + is a dialkylimidazolium cation, in which the alkyl groups each independently have 1 to 6 carbon atoms;

c) A − is an anion selected from the group consisting of R*COO − , R'SO 3 − , and R″SO 4 − ; and

d) R*, R 1 , R′, R″, R A , R B , and R C are each independently an alkyl group having 1 to 6 carbon atoms.

4. The process of claim 1 , wherein R A , R B , and R C are each independently either methyl or ethyl.

5. The process of claim 1 , wherein the liquid absorption medium A 1 is an aqueous solution.

6. The process of claim 5 , wherein, in the liquid absorption medium A 1 :

a) the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range of 65% by weight to 95% by weight, based on the total weight of the aqueous solution; or

b) the ratio of the total weight of all trialkyl phosphates of structure (I) to the total weight of all salts S is in the range from 1:9999 to 1:9.

7. An apparatus V 2 for dehumidifying a moist gas mixture, comprising the components:

(i) a liquid absorption medium A 1* , which comprises a mixture of at least one trialkyl phosphate of structure (I):

and at least one salt S selected from the group consisting of Q + A − , Q + (R 1 O) 2 PO 2 − , (Q + ) 2 R 2 OPO 3 2− , and Q + M + R 3 OPO 3 2− ;

(ii) at least one water absorption unit W abs2 set up for contacting the moist gas mixture with the liquid absorption medium A 1* ;

(iii) at least one water desorption unit W des2 which comprises a heat exchanger W x2 and is set up for at least partially removing water from a liquid absorption medium A 1* ;

(iv) and a circuit U 2 which connects the water absorption unit W abs2 with the water desorption unit W des2 and by means of which the liquid absorption medium A 1* may be circulated;

wherein:

Q + is a dialkylimidazolium cation;

A − is an anion selected from the group consisting of R*COO − , R′SO 3 − , HSO 4 − , and R″SO 4 − ;

R*, R′, R″, R A , R B , and R C are each independently an alkyl group;

R 1 , R 2 , and R 3 are each independently an alkyl group; and

M + is an alkali metal ion.

8. The apparatus V 2 of claim 7 , wherein in A 1* :

a) Q + is a dialkylimidazolium cation, in which the alkyl groups each independently have 1 to 10 carbon atoms;

b) R*, R′, R″, R A , R B , R C , R 1 , R 2 , R 3 are each independently an alkyl group having 1 to 10 carbon atoms; and

c) M + =Li + , K + or Na + .

9. The apparatus V 2 of claim 7 , wherein in A 1* :

a) salt S is selected from the group consisting of: Q + A − and Q + (R 1 O) 2 PO 2 − ;

b) Q + is a dialkylimidazolium cation, in which the alkyl groups each independently have 1 to 6 carbon atoms;

c) A − is an anion selected from the group consisting of: R*COO − , R′SO 3 − , and R″SO 4 − ; and

d) R*, R 1 , R′, R″, R A , R B , and R C are each independently an alkyl group having 1 to 6 carbon atoms.

10. The apparatus V 2 of claim 7 , wherein R A , R B , R C are mutually independently either methyl or ethyl.

11. The apparatus V 2 of claim 7 , wherein the liquid absorption medium A 1* is an aqueous solution.

12. The apparatus V 2 of claim 11 , wherein in A 1* :

a) the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range of 65% by weight to 95% by weight, based on the total weight of the aqueous solution; or

b) the ratio of the total weight of all trialkyl phosphates of structure (I) to the total weight of all salts S is in the range from 1:9999 to 1:9.

13. The apparatus V 2 of claim 7 , wherein V 2 is part of an absorption heat pump, that further comprises a condenser; an evaporator; and a coolant, wherein the coolant is water.

14. An absorption medium A 1* , comprising a mixture of at least one trialkyl phosphate of structure (I):

and at least one salt S selected from the group consisting of: Q + A − , Q + (R 1 O) 2 PO 2 − , (Q + ) 2 R 2 OPO 3 2− , and Q + M + R 3 OPO 3 2− ; wherein:

a) Q + is a dialkylimidazolium cation;

b) A − is an anion selected from the group consisting of R*COO − , R′SO 3 − , HSO 4 − , and R″SO 4 − ;

c) R*, R′, R″, R A , R B , R C , R 1 , R 2 , and R 3 are each independently an alkyl group; and

d) M + is an alkali metal ion.

15. The absorption medium A 1* of claim 14 , wherein:

a) Q + is a dialkylimidazolium cation, in which the alkyl groups each independently have 1 to 10 carbon atoms;

b) R*, R′, R″, R A , R B , R C , R 1 , R 2 , and R 3 are each independently an alkyl group having 1 to 10 carbon atoms; and

c) M + =Li + , K + or Na + .

16. The absorption medium A 1* of claim 14 , wherein:

a) salt S is selected from the group consisting of: Q + A − and Q + (R 1 O) 2 PO 2 − ;

b) Q + is a dialkylimidazolium cation in which the alkyl groups each independently have 1 to 6 carbon atoms;

c) A − is an anion selected from the group consisting of: R*COO − , R′SO 3 − , and R″SO 4 − ; and

d) R*, R 1 , R′, R″, R A , R B , and R C are each independently an alkyl group having 1 to 6 carbon atoms.

17. The absorption medium A 1* of claim 14 , wherein R A , R B , R C are mutually independently either methyl or ethyl.

18. The absorption medium A 1* of claim 14 , wherein is A 1* is an aqueous solution.

19. The absorption medium A 1* of claim 14 , in which the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range of 65% by weight to 95% by weight, based on the total weight of the aqueous solution.

20. The absorption medium A 1* of claim 14 , in which the ratio of the total weight of all trialkyl phosphates of structure (I) to the total weight of all salts S is in the range from 1:9999 to 1:9.