Storage medium and method for separating, storing and transporting chlorine from chlorine-containing gases

Abstract

The invention relates to a storage medium and to a method for using a storage medium based on ionic compounds, which can reversibly absorb and store chlorine and chlorine from process gases, and which can release the same again by changing the ambient conditions, wherein the storage medium can be reused for this task after discharge.

Claims

1. A process for the reversible storage of chlorine from chlorine-containing gas in a storage medium, the process comprising: contacting chlorine-containing gas with a liquid storage medium in a first step to form a loaded storage medium, the liquid storage medium comprising an ionic compound (I) having the formula
NR1.sub.mR2.sub.nR3.sub.o.sup.+Cl.sub.r.sup.(I); wherein the loaded storage medium comprises chlorine from the chlorine- containing gas in an ionic compound (III) having the formula
NR1.sub.mR2.sub.nR3.sub.o.sup.+Cl.sub.(r+2).sup.(III); wherein each of R1, R2 and R3 independently comprise an alkyl radical selected from the following group: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, and 2-methylpropyl; wherein R1, R2, and R3 collectively comprise more than one type of alkyl radical: wherein m is an integer in a range of 0 to 3, n is an integer in a range of 0 to 3, o is an integer in a range of 0 to 3, and wherein a sum consisting of m, n, and o is 4; and wherein r is an odd number in a range of 1 to 7, and wherein s is an odd number in a range of 1 to 7; removing chlorine from the loaded storage medium by increasing a temperature of the storage medium and/or lowering a partial pressure above the storage medium, thereby discharging chlorine.

2. The process as claimed in claim 1, wherein removing the chlorine takes place at a temperature within a range of 40 C. to 200 C., and at a pressure within a range of 900 hPa to 1100 hPa.

3. The process as claimed in claim 1, wherein removing the chlorine is initiated through reducing the partial pressure by at least 100 hPa.

4. The process as claimed in claim 1, wherein at least 0.10 g of chlorine per g of ionic compound (III), is released from the storage medium during this process.

5. The process as claimed in claim 1, wherein m is an integer in a range of 1 to 3, n is an integer in a range of 1 to 3, and o is equal to 0.

6. The process as claimed in claim 1, wherein the ionic compound (I) comprises a compound selected from the group consisting of NEtMe.sub.3Cl.sub.r, NEt.sub.2Me.sub.2Cl.sub.r, NEt.sub.3MeCl.sub.r, NBuEt.sub.2MeCl.sub.r, NMePr.sub.3Cl.sub.r, and NBu.sub.2Me.sub.2Cl.sub.r.

7. The process as claimed in claim 1, wherein the ionic compound (I) comprises a compound selected from the group consisting of NEtMe.sub.3Cl.sub.r, NEt.sub.2Me.sub.2Cl.sub.r, and NEt.sub.3MeCl.sub.r.

8. The process as claimed in claim 1, wherein the loaded storage medium contains at least 0.65 g of chlorine per g of ionic compound (III).

9. The process as claimed in claim 1, wherein the loaded storage medium is liquid at a temperature of 25 C. and a pressure of 1000100 hPa.

10. The process as claimed in claim 1, wherein the process comprises conditioning an initial loading of a storage medium with chlorine gas, wherein the storage medium comprises the ionic compound (I), wherein the initial loading of the storage medium becomes loaded with chlorine gas only to such an extent that the storage medium liquefies.

11. The process as claimed in claim 10, wherein conditioning with chlorine takes place to such an extent that a storage medium of ionic compound (III) is obtained and the storage medium of ionic compound (III) is not fully loaded with chlorine.

12. The process as claimed in claim 10, wherein in a second step after conditioning, chlorine is removed from chlorine-containing gas through contacting with the liquid storage medium from the first step, as a result of which the storage medium becomes loaded and the compounds (I) reacts to form ionic compounds (III).

13. The process as claimed in claim 1, wherein the loading of the liquid storage medium takes place at a temperature in a range of 0 C. to 40 C. and a pressure within a range of 900 hPa to 7000 hPa.

Description

EXAMPLES

(1) In order to obtain reversible storage media, ionic compounds that are solid at room temperature and ambient pressure (e.g. corresponding to the above formula I, where r and s=1) should first be fed into an initial loading with chlorine in order to bring about liquefaction of the ionic compound and associated formation of polychlorides. The liquefied polychlorides containing ionic compounds serve thereafter as reversible storage media and are only partially unloaded through the chosen release parameters, with the result that the storage media are liquid both in the loaded and in the unloaded state. In the case of ionic compounds or liquid mixtures of different ionic compounds to be used in the chlorine storage medium that are themselves liquid at room temperature, there is no need for preloading with chlorine to achieve the liquid state.

Example 1 (Prior Art)

(2) A reactor was charged with tetrabutylammonium chloride [NBu.sub.4]Cl (100 g) and this was thermally equilibrated at 20 C. The initial loading of the ionic compound was effected by introducing chlorine at approx. 1000 hPa, which led to liquefaction of the [NBu.sub.4]Cl. This resulted in the absorption by the [NBu.sub.4]Cl of 61 g of chlorine, i.e. 0.61 g of chlorine per g of ionic compound. The loaded chlorine store was unloaded at 60 C., resulting in the release again of 23 g of chlorine, i.e. 0.23 g of chlorine per g of ionic compound. The dynamic viscosity of the unloaded chlorine store at 60 C. was 430 mPa.Math.s. The chlorine loads in the loaded and unloaded states were determined at 20 C. and 1000 hPa. The dynamic viscosity of the store in the chlorine-loaded and unloaded states was measured at 25 C. and 1000 hPa using a micro-Ubbelohde viscometer (inner diameter 0.53 mm, SI-Analytics GmbH, Mainz).

(3) The combination of high viscosity and low chlorine release of the loaded chlorine store and the more difficult handling of the initially solid storage material has proved disadvantageous for implementation of the laboratory process on an industrial scale.

Example 2 (According to the Invention)

(4) In order to obtain liquid and reversible storage media, a reactor was in a first step charged with solid triethylmethylammonium chloride [NEt.sub.3Me]Cl (100 g) and this was thermally equilibrated at 20 C. The initial loading of the ionic compound was effected by introducing chlorine at approx. 1000 hPa, as a result of which 87 g of chlorine was bound and the storage medium ([NEt.sub.3Me]Cl) liquefied. This resulted in the absorption by the [NEt.sub.3Me]Cl of 0.87 g of chlorine per g of ionic compound, the dynamic viscosity of the liquid, loaded chlorine store being 19 mPa.Math.s. Raman spectroscopy showed the loaded chlorine store to consist of a mixture of different tri- to nonachlorides, corresponding formally to [NEt.sub.3Me]Cl.sub.4.7. The loaded store was unloaded at 60 C., resulting in the release of 30 g of chlorine, i.e. 0.30 g of chlorine per g of ionic compound. The dynamic viscosity of the unloaded chlorine store was 44 mPa.Math.s.

(5) Compared to chlorine stores based on [NBu.sub.4]Cl, the viscosity of the chlorine store in the loaded and unloaded state is substantially lower, while chlorine release is higher.

(6) The liquid chlorine store could be unloaded at 60 C. to be loaded afresh with chlorine, with absorption carried out under the above-mentioned conditions (introduction of chlorine at approx. 1000 hPa and thermal equilibration of the reactor at 20 C.). In the renewed loading, 87 g of chlorine, i.e. 0.87 g of chlorine per g of ionic compound, was again absorbed and, during subsequent unloading under the above conditions (60 C.), 30 g of chlorine, i.e. 0.30 g of chlorine per g of ionic compound, was again released, with the storage medium always remaining liquid in the loaded and unloaded state. The liquid chlorine store could be loaded and unloaded more than 4 times without a decrease in the amounts of chlorine stored and released being observed.

Example 3 (According to the Invention)

(7) In order to obtain liquid and reversible storage media, a reactor was in a first step charged with solid diethyldimethylammonium chloride [NEt.sub.2Me.sub.2]Cl (100 g) and this was thermally equilibrated at 20 C. The initial loading of the ionic compound was effected by introducing chlorine at approx. 1000 hPa, as a result of which 82 g of chlorine was bound and the storage medium ([NEt.sub.2Me.sub.2]Cl) liquefied. This resulted in the absorption by the [NEt.sub.2Me.sub.2]Cl of 0.82 g of chlorine per g of ionic compound, the dynamic viscosity of the liquid, loaded chlorine store being 16 mPa.Math.s. The loaded store corresponds formally to the composition [NEt.sub.2Me.sub.2]Cl.sub.4.2. The loaded store was unloaded at 60 C., resulting in the release again of 29 g of chlorine, i.e. 0.29 g of chlorine per g of ionic compound. The dynamic viscosity of the unloaded chlorine store was 37 mPa.Math.s.

(8) Compared to chlorine stores based on [NBu.sub.4]Cl, the dynamic viscosity of the chlorine store in the loaded and unloaded state is substantially lower, while chlorine release is higher.

(9) In analogous manner to example 2, the loaded liquid chlorine store could be loaded afresh with chlorine, with absorption carried out under the above-mentioned conditions (introduction of chlorine at approx. 1000 hPa and thermal equilibration of the reactor at 20 C.). In the renewed loading, 82 g of chlorine, i.e. 0.82 g of chlorine per g of ionic compound, was absorbed and, during subsequent unloading under the above conditions, 29 g of chlorine, i.e. 0.29 g of chlorine per g of ionic compound, was again released, with the storage medium always remaining liquid in the loaded and unloaded state. The liquid chlorine store could be loaded and unloaded more than 4 times without a decrease in the amounts of chlorine stored and released being observed.