Electrochemical gas generator for ammonia with the use of ionic liquids and use of the gas generator

Abstract

An electrochemical gas generator for ammonia with the use of ionic liquids containing nitrate ions as the electrolyte and to the use of the gas generator for generating gaseous ammonia, especially for testing the function of and/or calibrating gas sensors.

Claims

1. An electrochemical test gas generator comprising: an electrolysis cell having a housing with a membrane permeable to gaseous ammonia; a liquid electrolyte disposed in the housing, the liquid electrolyte comprising at least one ionic liquid from a nitrate salt; at least two electrodes in the housing, which are in contact with the electrolyte; and a power or voltage source, which is connected to the electrodes, wherein the ionic liquid comprises a hydrocarbon-substituted ammonium nitrate compound or a hydrocarbon-substituted imidazolium nitrate compound or both a hydrocarbon-substituted ammonium nitrate compound and a hydrocarbon-substituted imidazolium nitrate compound as a gaseous ammonia source material, which is reduced into ammonia (NH.sub.3) at one of the at least two electrodes and releases NH.sub.3 continuously as a gas.

2. An electrochemical test gas generator in accordance with claim 1, wherein the ionic liquid comprises ethylammonium nitrate or ethylimidazolium nitrate or methylimidazolium nitrate or any combination of ethylammonium nitrate and ethylimidazolium nitrate and methylimidazolium nitrate.

3. An electrochemical test gas generator in accordance with claim 1, wherein the liquid electrolyte further comprises a diluent that is an organic compound that is liquid at room temperature with a boiling point above 150 C. (at 1013 mbar), having at least one hydroxyl group or at least one COC bond or both at least one hydroxyl group or at least one COC bond.

4. An electrochemical test gas generator in accordance with claim 1, wherein the liquid electrolyte further comprises a diluent selected from hydroxyalkyl ethers, glycol, diglyme, triglyme, ethylene glycol, butyl diglycol, propylene carbonate, ethylene carbonate and mixtures thereof.

5. An electrochemical test gas generator in accordance with claim 1, wherein the liquid electrolyte further comprises one or more additional ionic liquids without a nitrate group.

6. An electrochemical test gas generator in accordance with claim 5, wherein the one or more additional ionic liquids without a nitrate group comprises an alkylated imidazolium-bistrifluorosulfonylimide compound.

7. An electrochemical test gas generator in accordance with claim 1, further comprising a control unit for galvanostatic regulation of an electrolysis current or for potentiostatic control of a working potential.

8. An electrochemical test gas generator in accordance with claim 1, wherein a current of 100 A to 100 mA flows during electrolysis.

9. An electrochemical test gas generator in accordance with claim 1, further comprising at least one reference electrode in contact with the electrolyte.

10. An electrochemical test gas generator in accordance with claim 9, wherein the reference electrode comprises a metal of the group comprising Cu, Ni, Ti, Pt, Ir, Au, Pd, Ag, Ru, Sn and Rh or mixtures, alloys or oxides of one or more metals of the group.

11. An electrochemical test gas generator in accordance with claim 9, wherein the reference electrode comprises a carbon-containing material comprised of carbon nanotubes (CNT) or graphite or glassy carbon or graphene or doped diamond or any combination of carbon nanotubes (CNT) and graphite and glassy carbon and graphene and doped diamond.

12. An electrochemical test gas generator in accordance with claim 1, wherein the electrodes comprise a metal of the group Cu, Ni, Ti, Pt, Ir, Au, Pd, Ag, Ru, Sn and Rh or mixtures, alloys or oxides of one or more metals of the group, wherein the metals of the electrodes are identical or different.

13. An electrochemical test gas generator in accordance with claim 1, wherein at least one of the electrodes comprises a carbon-containing material comprised of carbon nanotubes (CNT) or graphite or glassy carbon or graphene or doped diamond or any combination of carbon nanotubes (CNT) and graphite and glassy carbon and graphene and doped diamond.

14. An electrochemical test gas generator in accordance with claim 1, wherein the electrochemical test gas generator is a test gas generator for gas sensor calibration and is configured to generate gaseous ammonia with only the liquid electrolyte and the at least two electrodes present in the housing and to direct gaseous ammonia, generated within the housing to leave the housing without any feed material being fed into the housing.

15. An electrochemical test gas generator in accordance with claim 14, further comprising another membrane configured to allow gases, that may have formed within said housing, to leave said housing wherein: said housing defines only two openings; said two openings comprise a first opening and a second opening; said first opening is fully covered by said membrane permeable to gaseous ammonia; said membrane permeable to gaseous ammonia is configured to be liquid tight; said second opening is fully covered by said another membrane; the power or voltage source is connected to the electrodes to generate the gaseous ammonia exclusively with materials within said housing, which said materials comprising the liquid electrolyte and the at least two electrodes; and gases leave the gas generator housing through said membrane permeable to gaseous ammonia and through said another membrane without any feed material being fed into the gas generator housing.

16. An electrochemical test gas generator comprising: an electrolysis cell comprising a gas barrier housing defining at least one opening closed by a gas permeable membrane permeable to gaseous ammonia; a liquid electrolyte disposed in the housing, the liquid electrolyte comprising at least one ionic liquid from a nitrate salt, wherein the ionic liquid comprises a hydrocarbon-substituted ammonium nitrate compound or a hydrocarbon-substituted imidazolium nitrate compound or both a hydrocarbon-substituted ammonium nitrate compound and a hydrocarbon-substituted imidazolium nitrate compound; at least two electrodes in the housing, which are in contact with the electrolyte; and a power or voltage source, which is connected to the electrodes, to reduce the hydrocarbon-substituted ammonium nitrate compound or a hydrocarbon-substituted imidazolium nitrate compound or both a hydrocarbon-substituted ammonium nitrate compound and a hydrocarbon-substituted imidazolium nitrate compound into ammonia at one of the at least two electrodes to continuously generate gaseous ammonia with the liquid electrolyte and the at least two electrodes, whereby gaseous ammonia generated within the gas barrier housing leaves the gas barrier housing without any feed material being fed into the gas barrier housing.

17. An electrochemical test gas generator according to claim 16, further comprising another membrane configured to allow gases, that may have formed within said housing, to leave said housing wherein: said housing defines only two openings; said two openings comprise a first opening and a second opening; said first opening is fully covered by said membrane permeable to gaseous ammonia; said membrane permeable to gaseous ammonia is configured to be liquid tight; said second opening is fully covered by said another membrane; the power or voltage source is connected to the electrodes to generate the gaseous ammonia with the liquid electrolyte and the at least two electrodes; and gases leave said housing through said membrane permeable to gaseous ammonia and through said another membrane without any feed material being fed into said housing.

18. An electrochemical test gas generator comprising: an electrolysis cell having a housing with a membrane permeable to gaseous ammonia; a liquid electrolyte disposed in the housing, the liquid electrolyte comprising at least one ionic liquid from a nitrate salt; at least two electrodes in the housing, which are in contact with the electrolyte; and a power or voltage source, which is connected to the electrodes, the electrodes powered by the power or voltage source cooperating with the liquid electrolyte disposed in the housing to generate gaseous ammonia within the housing with the liquid electrolyte providing the only source material forming the generated gaseous ammonia and wherein the housing is configured to direct gaseous ammonia, generated within the housing, out of the housing, wherein the ionic liquid comprises a hydrocarbon-substituted ammonium nitrate compound or a hydrocarbon-substituted imidazolium nitrate compound or both a hydrocarbon-substituted ammonium nitrate compound and a hydrocarbon-substituted imidazolium nitrate compound, which hydrocarbon-substituted imidazolium nitrate compound is reduced into ammonia at one of the at least two electrodes and to release ammonia continuously as a gas.

19. An electrochemical test gas generator according to claim 18, wherein the electrolyte has a melting point below 25 C.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1 is a schematic view showing the configuration of an electrolysis cell, which is used as an electrochemical gas generator for producing ammonia.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(3) Referring to the drawings, an electrolyte 3 is contained in the electrolysis cell, which comprises a non-conductive housing 1, which is closed by a gas-permeable membrane 2. The cathode 4 and the anode 5 are likewise located within the housing and are in contact with the electrolyte 3. The electrolyte is reacted electrochemically when a direct current voltage is applied to the electrodes by means of the control unit 6 or else a constant current flows over the cell in the sense of a galvanostatic operation. The gas released, NH.sub.3, is discharged through the gas-permeable but liquid-tight membrane 2. Gases that may have possibly formed at the counterelectrode can leave the gas generator housing via the optionally installed counterelectrode membrane 7.

Example

(4) A cylindrical electrolysis cell with a diameter of 1.5 cm and a height of 3 cm, made of polypropylene as the material of the housing, was provided. A PTFE membrane coated with carbon nanotubes was welded as a cathode on housing openings in the bottom surface, and a carbon nanotubes-PTFE membrane unit was likewise incorporated as the anode in the cover surface. The circular, flat electrodes had a size of 10 mm in diameter and were contacted by means of platinum wires, which made possible the electrical connection to a galvanostatic control unit. The electrolyte consisting of ethylammonium nitrate EtNH.sub.3.sup.+ NO.sub.3.sup., diluted 1:1 with ethylene glycol, was split at a constant current flow of 2.5 mA, which means that nitrate was reduced into ammonia at the working electrode and NH.sub.3 was released continuously as a gas. The gaseous ammonia formed at the cathode diffused through the permeable membrane consisting of PTFE from the housing of the electrolysis cell and was used for testing a sensor.

(5) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.