Method for dehumidifying humid gas mixtures using ionic liquids

1. A process for dehumidifying a moist gas mixture G in an apparatus V 1 , comprising the steps of:

(a) contacting the moist gas mixture G with a liquid absorption medium A VE comprising at least one salt selected from the group consisting of: Q + (RO) 2 PO 2 − ; (Q + ) 2 ROPO 3 2− ; and Q + M + ROPO 3 2− ; wherein the liquid absorption medium A VE at least partially absorbs water from the moist gas mixture G, to obtain a liquid absorption medium A VE1 having an elevated water content compared to the liquid absorption medium A VE and a gas mixture G 1 having a relatively low water content compared to the moist gas mixture G;

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

wherein the apparatus V 1 at least partially comprises a surface made of an aluminium material of construction O Al and in the apparatus V 1 , at least one of the liquid absorption media selected from the group consisting of A VE , A VE1 , A VE2 contacts the surface made of O Al via at least one contact surface;

and wherein:

Q + is a 1,3-dialkylimidazolium in which the alkyl groups are, independently of one another, unbranched or branched C 1 -C 6 alkyl groups;

R is an unbranched or branched C 2 -C 6 alkyl group;

and M + is an alkali metal ion.

2. The process of claim 1 , wherein R is selected from the group consisting of: an ethyl group and a n-butyl group.

3. The process of claim 1 , wherein Q + is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium.

4. The process of claim 3 , wherein the salt is selected from the group consisting of: 1,3-diethylimidazolium diethylphosphate; 1-ethyl-3-methylimidazolium diethylphosphate; and 1-n-butyl-3-methylimidazolium di-n-butylphosphate.

5. The process of claim 1 , wherein the liquid absorption medium A VE is an aqueous solution in which the total weight of all salts of structure Q + (RO) 2 PO 2 − , (Q + ) 2 ROPO 3 2− and Q + M + ROPO 3 2− is at least 70 wt % based on the total weight of the aqueous solution.

6. The process of claim 1 , wherein said process is carried out in continuous fashion.

7. The process of claim 2 , wherein:

a) Q + is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium; and

b) the liquid absorption medium A VE is an aqueous solution in which the total weight of all salts of structure Q + (RO) 2 PO 2 − , (Q + ) 2 ROPO 3 2− and Q + M + ROPO 3 2− is at least 70 wt % based on the total weight of the aqueous solution.

8. The process of claim 1 , wherein said process is carried out using an apparatus V 2 for dehumidifying a moist gas mixture, wherein said apparatus comprises the components:

a) a liquid absorption medium A VO comprising at least one salt selected from the group consisting of: Q + (RO) 2 PO 2 − ; (Q + ) 2 ROPO 3 2− ; and Q + M + ROPO 3 2− ;

b) at least one water absorption unit W abs2 for contacting the moist gas mixture with the liquid absorption medium A VO ;

c) 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 VO ; and

d) 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 VO may be circulated;

wherein at least one of the components W abs2 , W des2 , and U 2 at least partially comprises a surface made of an aluminium material of construction O Al ; and

wherein disposed in the apparatus V 2 is at least one contact surface at which the liquid absorption medium A VO contacts the surface made of O Al ;

and wherein:

Q + is a 1,3-dialkylimidazolium where the alkyl groups are independently of one another unbranched or branched C 1 -C 6 alkyl groups;

R is an unbranched or branched C 2 -C 6 alkyl group;

and M + is an alkali metal ion.

9. The process of claim 8 , wherein R is selected from the group consisting of: an ethyl group and a n-butyl group.

10. The process of claim 9 , wherein:

a) Q + is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium; and

b) the liquid absorption medium A VE is an aqueous solution in which the total weight of all salts of structure Q + (RO) 2 PO 2 − , (Q + ) 2 ROPO 3 2− and Q + M + ROPO 3 2− is at least 70 wt % based on the total weight of the aqueous solution.

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

a) a liquid absorption medium A VO comprising at least one salt selected from the group consisting of: Q + (RO) 2 PO 2 − ; (Q + ) 2 ROPO 3 2− ; and Q + M + ROPO 3 2− ;

b) at least one water absorption unit W abs2 for contacting the moist gas mixture with the liquid absorption medium A VO ;

c) 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 VO ; and

d) 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 VO may be circulated;

wherein at least one of the components W abs2 , W des2 , and U 2 at least partially comprises a surface made of an aluminium material of construction O Al ; and

wherein disposed in the apparatus V 2 is at least one contact surface at which the liquid absorption medium A VO contacts the surface made of O Al ;

and wherein:

Q + is a 1,3-dialkylimidazolium where the alkyl groups are independently of one another unbranched or branched C 1 -C 6 alkyl groups;

R is an unbranched or branched C 2 -C 6 alkyl group;

and M + is an alkali metal ion.

12. The apparatus V 2 of claim 11 , wherein R is selected from the group consisting of:

an ethyl group and a n-butyl group.

13. The apparatus V 2 of claim 11 , wherein Q + is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium.

14. The apparatus V 2 of claim 13 , wherein the salt is selected from the group consisting of: 1,3-diethylimidazolium diethylphosphate; 1-ethyl-3-methylimidazolium diethylphosphate; and 1-n-butyl-3-methylimidazolium di-n-butylphosphate.

15. The apparatus V 2 of claim 11 , wherein A VO is an aqueous solution in which the total weight of all salts of structure Q + (RO) 2 PO 2 − , (Q + ) 2 ROPO 3 2− and Q + M + ROPO 3 2 is at least 70 wt % based on the total weight of the aqueous solution.

16. The apparatus V 2 of claim 11 , wherein at least one of the components W abs2 , and W des2 is a falling film.

17. The apparatus V 2 of claim 11 , comprising a further heat exchanger W y2 positioned so that liquid absorption medium A VO sent from the water absorption unit W abs2 to the water desorption unit W des2 is suppliable with heat from liquid absorption medium A VO , said medium being conducted away from the water desorption unit W des2 .

18. The apparatus of claim 12 , wherein:

a) Q + is selected from the group consisting of 1,3-dimethylimidazolium, 1,3-diethylimidazolium, 1-ethyl-3-methylimidazolium, 1-n-butyl-3-methylimidazolium; and

b) the liquid absorption medium A VE is an aqueous solution in which the total weight of all salts of structure Q + (RO) 2 PO 2 − , (Q + ) 2 ROPO 3 2− and Q + M + ROPO 3 2 is at least 70 wt % based on the total weight of the aqueous solution.

19. The apparatus of claim 18 , comprising a further heat exchanger W y2 positioned so that liquid absorption medium A VO sent from the water absorption unit W abs2 to the water desorption unit W des2 is suppliable with heat from liquid absorption medium A VO , said medium being conducted away from the water desorption unit W des2 .

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