Method for Desorbing Carbon Dioxide from Polymeric Organic Anion Exchangers

Abstract

The invention relates to a process for desorbing carbon dioxide from polymeric organic anion exchangers having primary and/or secondary amine groups, to which the carbon dioxide is bound in the form of carbamate, by means of heating through microwave radiation.

Claims

1. A process comprising desorbing carbon dioxide from at least one anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) ##STR00003## where represents a polystyrene copolymer scaffold and R.sup.1 may be C.sub.1 to C.sub.6 alkyl and/or H and the methylene group in the formula (I) that is attached to the nitrogen atom is attached to an aromatic moiety in the polystyrene copolymer, wherein said desorbing comprises increasing the temperature by means of microwave radiation and optionally by reducing the pressure.

2. The process according to claim 1, wherein R.sup.1 is methyl, ethyl, n-propyl, s-propyl, n-butyl, s-butyl, t-butyl or hydrogen.

3. The process according to claim 1, wherein the polystyrene copolymer scaffold of the anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) is a crosslinked styrene/divinylbenzene copolymer.

4. The process according to claim 1, wherein the anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) comprises a bead polymer having a pore diameter of 100 to 550 angstroms.

5. The process according to claim 1, wherein R.sup.1 is hydrogen.

6. The process according to claim 1, wherein the anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) contains 0.2 to 3.0 moles of CO.sub.2 per kg of dried anion exchanger.

7. The process according to claim 1, wherein the desorbing is carried out at temperatures of from 50° C. to 180° C.

8. The process the desorbing is carried out at pressures of from 10.sup.−3 mbar to standard pressure.

9. The process according to claim 1, wherein the energy of the microwave radiation is from 1 kW to 1000 kW.

10. The process according to claim 1, wherein the anion exchanger of the formula (I) is produced by the reaction with carbon dioxide of an anion exchanger comprising polystyrene copolymers having functional groups of the formula (II) ##STR00004## where and R.sup.1 are as defined above.

11. The process according to claim 10, wherein carbon dioxide-containing gases are adsorbed.

12. The process as claimed in claim 11, wherein the gases contain 0.1% by volume to 60% by volume of carbon dioxide based on the total volume of the employed gases.

13. The process according to claim 11, wherein the water content of the gas is 0.1% by volume to 20% by volume.

14. The process according to claim 10, wherein the water content of the anion exchangers comprising polystyrene copolymers having functional groups of the formula (II) shows 1% by weight to 20% by weight based on the total mass of the anion exchangers.

15. The process according to claim 10, wherein the adsorption of carbon dioxide on the anion exchanger comprising polystyrene copolymers having functional groups of the formula (II) takes place at temperatures of from 0° C. to 30° C.

Description

EXAMPLES

Example 1

[0062] A macroporous crosslinked anion exchanger comprising styrene/divinylbenzene copolymers having functional groups of the formula (II) and having a content of primary amine groups of 1.0 to 2.5 mol/1, a degree of crosslinking of 2% to 10%, and a pore diameter of 100 to 550 angstroms was used. The anion exchanger was dried and contained 2% water when used.

[0063] In the laboratory experiment carried out, the anion exchanger having functional groups of the formula (II) was introduced into a quartz-glass column in a microwave test reactor. The microwave test reactor consisted of a hollow stainless steel cylinder in which the quartz-glass column was fitted, such that the ion exchanger could be irradiated with microwaves by means of a microwave antenna likewise fitted inside the stainless steel cylinder at a distance of 7 cm from the quartz-glass column. The assembly is additionally provided with a means of generating a vacuum inside the microwave reactor and the quartz-glass column. The quartz-glass column used shows very low microwave absorption (tan αδ×10.sup.3) within a range from 5 to 7.

[0064] 15 ml (7.5 g) of anion exchanger comprising styrene/divinylbenzene copolymers having functional groups of the formula (II) was used and contacted with a continuous stream of 50% by volume of CO.sub.2 and 50% by volume of air (input concentration) with a total throughput of 3 1/h (specific speed 200 BV/h). CO.sub.2 loading is 2.0 mol per kg of dried anion exchanger.

[0065] After loading the anion exchanger having functional groups of the formula (II) with CO.sub.2 under atmospheric conditions, the resin was then 100% regenerated by applying a vacuum of 0.1 mbar and by heating the adsorber to 90° C. using microwave radiation. Regeneration was carried out for a period of 40 min, after which no more CO.sub.2 release could be measured.

[0066] The adsorbed amount of CO.sub.2 was released again in its entirety by the ion exchanger.

[0067] The real dielectric constant ε′ and complex dielectric constant ε″ of a CO.sub.2-saturated, dried anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) was measured at room temperature according to J. Krupka, T. Zychowicz, V. Bovtun, and S. Veljko, “Complex Permittivity Measurements of Ferroelectrics Employing Composite Dielectric Resonator Technique”, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, pp. 1883-1888, vol. 53, No 10, October 2006 in order to calculate therefrom the microwave absorption coefficient (tan αδ×10.sup.3). The ratio of the two dielectric constants constitutes, as loss angle tan αδ=ε″/ε′, a measure of the ability of a bed of an anion exchanger to absorb microwave radiation and thus to be heated. This is surprisingly 34.4 tan αδ×10.sup.3 and is accordingly significantly higher than the value that would have been expected for polystyrene (0.3 tan αδ×10.sup.3, source: Meredith R. J. (1998), Engineers' Handbook of Industrial Microwave Heating, Exeter, p. 29 The Institution of Engineering and Technology, London, United Kingdom, Lightning Source UK Ltd., printed in the UK by Short Run Press Ltd.

[0068] The anion exchanger comprising polystyrene copolymers having functional groups of the formula (I) therefore allows heating and regeneration by means of microwave radiation.