Process for dehumidifying moist gas mixtures

1. A process for dehumidifying a moist gas mixture G, in an apparatus (V 1 ), comprising:

(a) contacting the moist gas mixture G with an aqueous liquid absorption medium A VE 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 VE at least partially absorbs water from the moist gas mixture G,

to afford an aqueous liquid absorption medium A VE1 having an elevated water content compared to A VE and a gas mixture G 1 having a relatively low water content compared to the moist gas mixture G;

(b) partially removing water from A VE1 to obtain an aqueous liquid absorption medium A VE2 having a relatively low water content compared to the aqueous liquid absorption medium A VE1 ;

wherein the apparatus (V 1 ) at least partially comprises a surface made of a steel material of construction O st and, in the apparatus (V 1 ), at least one of the aqueous liquid absorption medium A VE , the aqueous liquid absorption medium A VE1 and the aqueous liquid absorption medium A VE2 contacts the surface made of a steel material of construction O st via at least one contact surface;

wherein:

Q + is a dialkylimidazolium cation,

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

R*, R′, R″, R A , R B , R C , R 1 , R 2 , R 3 are each independently of one another an alkyl group, and wherein M + is an alkali metal ion.

2. The process of claim 1 , wherein the gas mixture G is moist air.

3. The process of claim 1 , wherein:

a) Q + is a dialkylimidazolium cation in which the alkyl groups each independently of one another 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 of one another an alkyl group having 1 to 10 carbon atoms; and

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

4. The process of claim 1 , 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 of one another have 1 to 6 carbon atoms; and

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 , R C are each independently of one another an alkyl group having 1 to 6 carbon atoms.

5. The process of claim 1 , wherein R A , R B , R C are independently of one another selected from the group consisting of: methyl and ethyl.

6. The process of claim 1 , wherein the aqueous liquid absorption medium A VE is an aqueous solution, and the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range 65 wt % to 95 wt % based on the total weight of the aqueous solution.

7. The process of claim 1 , wherein, in the aqueous liquid absorption medium A VE , 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 1:9999 to 1:9.

8. The process of claim 3 , wherein R A , R B , and R C are independently of one another selected from the group consisting of: methyl and ethyl.

9. The process of claim 8 , wherein the aqueous liquid absorption medium A VE is an aqueous solution, and the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range 65 wt % to 95 wt % based on the total weight of the aqueous solution.

10. The process of claim 9 , wherein, in the aqueous liquid absorption medium A VE , 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 1:9999 to 1:9.

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

(i) an aqueous liquid absorption medium, A VO , 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 aqueous liquid absorption medium A VO ;

(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 an aqueous liquid absorption medium A VO ; and

(iv) 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 aqueous liquid absorption medium A VO may be circulated,

wherein at least one of the components selected from the group consisting of: the water absorption unit (W abs2 ); the water desorption unit (W des2 ); and the circuit (U 2 ), at least partially comprises a surface made of a steel material of construction O ST ;

wherein, disposed in the apparatus (V 2 ), is at least one contact surface at which the aqueous liquid absorption medium A VO contacts the surface made of a steel material of construction O st ;

and wherein:

Q + is a dialkylimidazolium cation;

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

R*, R′, R″, R A , R B , R C , R 1 , R 2 , R 3 are each independently of one another an alkyl group; and

M + is an alkali metal ion.

12. The apparatus (V 2 ) of claim 11 , wherein:

a) Q + is a dialkylimidazolium cation in which the alkyl groups each independently of one another 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 of one another an alkyl group having 1 to 10 carbon atoms; and

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

13. The apparatus (V 2 ) of claim 11 , 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 of one another have 1 to 6 carbon atoms;

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

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

14. The apparatus (V 2 ) of claim 11 , wherein R A , R B and R C are independently of one another selected from the group consisting of: methyl and ethyl.

15. The apparatus (V 2 ) of claim 11 , wherein the aqueous liquid absorption medium A VO is an aqueous solution, and, the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range 65 wt % to 95 wt % based on the total weight of the aqueous solution.

16. The apparatus (V 2 ) of 11 , wherein, in the aqueous liquid absorption medium A VO , 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 1:9999 to 1:9.

17. The apparatus of claim 12 , wherein R A , R B , R C are independently of one another selected from the group consisting of: methyl and ethyl.

18. The apparatus of claim 17 , wherein the aqueous liquid absorption medium A VO is an aqueous solution, and, the total weight of all trialkyl phosphates of structure (I) and all salts S is in the range 65 wt % to 95 wt % based on the total weight of the aqueous solution.

19. The apparatus of claim 18 , wherein, in the aqueous liquid absorption medium A VO 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 1:9999 to 1:9.

20. An absorption heat pump, comprising the apparatus (V 2 ) of claim 11 and further comprising a condenser, an evaporator and a coolant, wherein the coolant is water.