System and method for decomposing gaseous hydrogen sulfide into hydrogen gas and elementary sulfur

1. A decomposition system providing the decomposition of gaseous hydrogen sulfide into hydrogen gas and elementary sulfur, characterized by comprising

at least one pump ( 1 ) providing the supply of H 2 S gas from a source into the system in the form of bubbles;

an aqueous acidic phase with a pH below 4, providing the ionization of H 2 S gas in water and comprising at least one redox couple;

and at least one column reactor ( 2 ) comprising an organic phase ( 2 b ), which is immiscible in water, with a density above the density of water and capable to dissolve elementary sulfur, wherein the organic phase ( 2 b ) stays below the aqueous acidic phase, wherein the aqueous phase and the organic phase do not mix with each other because of density difference and thus form an interface ( 2 c ) where they contact each other; and an oxidation reaction takes place in the interface ( 2 c ) by which the H 2 S bubbles carried into the organic phase ( 2 b ) through the pump ( 1 ) are converted into elementary sulfur;

at least one cooling unit ( 3 ) to which the elementary sulfur generated in the column reactor ( 2 ) is transferred and is crystallized to be taken out of the system;

at least one photo-/electrochemical cell ( 5 ), which comprises at least one first chamber ( 5 A) comprising at least one anode electrode, at least one second chamber ( 5 B) comprising at least one cathode electrode, and at least one membrane ( 5 C) separating the first chamber ( 5 A) from the second chamber ( 5 B), and to which the aqueous acidic phase ( 2 a ) in the column reactor ( 2 ) is transferred, and in which the oxidation of the redox couple and the reduction reaction of H + to H 2 take place, wherein following the reduction reaction, the aqueous acidic phase ( 2 a ) is transferred back to the column reactor ( 2 );

and at least one energy source ( 6 ) generating the required potential difference to be conducted to at least one of the electrodes for the oxidation of the redox couple and the reduction reaction of H + to H 2 .

2. The system according to claim 1 , characterized in that said pump ( 1 ) is a micro bubble generator.

3. The system according to claim 1 , characterized by comprising at least one filter ( 4 ) by which crystallized elementary sulfur is taken from the system.

4. The system according to claim 1 , characterized in that said energy source ( 1 ) is an electrical power supply.

5. The system according to claim 1 , characterized in that said energy source ( 1 ) is a UV/visible light source.

6. The system according to claim 1 , characterized in that the redox couple is I 3 /I − , [Fe(CN) 6 ] 3− /[Fe(CN) 6 ] 4− , Co(III)(byp) 3 /Co(II)(byp)3, metal salts and/or metallocenes.

7. The system according to claim 6 , characterized in that said metal salts comprise Fe 3+ /Fe 2+ , Co 3+ /Co 2+ , Mn 3+ /Mn 2+ and Ce 3+ /Ce 4+ cations and SO 4 2— , NO 3 − , Cl − anions.

8. The system according to claim 1 , characterized in that said redox couple is Fe 2+ /Fe 3+ .

9. The system according to claim 1 , characterized in that the acid source of the aqueous acidic phase ( 2 a ) is sulfuric acid, hydrochloric acid and/or nitric acid.

10. The system according to claim 1 , characterized in that said organic phase ( 2 b ) is pure chlorobenzene, pure chlorobenzene toluene and/or a mixture thereof with benzene or carbon disulfide.

11. The system according to claim 1 , characterized in that the anode electrode and/or the cathode electrode is selected from a group comprising graphite, vitreous carbon, platinum, palladium, metals, metal oxides, metal sulfites, metal phosphites, metal selenides and semiconductors.

12. The system according to claim 11 , characterized in that said metal is Ag, Fe, Co, Ni, Mo or W.

13. The system according to claim 1 , characterized in that the surface of the anode electrode and/or of the cathode electrode is coated with SiO 2 and/or Al 2 O 3 .

14. The system according to claim 5 , characterized in that the anode electrode and/or the cathode electrode is selected from a group comprising hybrid electrodes which comprise platinum, palladium, metal sulfites, metal phosphites, metal selenides on photoactive substrates of silicon, AgS, CdSe, CdS, CdTe and Cu 2 O.

15. The system according to claim 14 , characterized in that said metal is Fe, Co, Ni, Mo or W.

16. The system according to claim 3 , characterized in that the filter ( 4 ) is a vacuum filter.

17. A decomposition method providing the decomposition of gaseous hydrogen sulfide into hydrogen gas and elementary sulfur, characterized by comprising the steps of

generating H 2 S bubbles by distributing gaseous H 2 S received from a source into an organic phase ( 2 b ) provided in a column reactor ( 2 ) through at least one pump ( 1 );

decomposing H 2 S into elementary sulfur and H + ions by oxidizing the H 2 S bubbles in an interface ( 2 c ) between an aqueous acidic phase ( 2 a ), comprising at least one redox couple and having a pH below 4 and providing the ionization of H 2 S in water, and the organic phase ( 2 b ) which has a density above the density of water and is capable to dissolve elementary sulfur;

transferring the H + ions decomposed from H 2 S into the aqueous acidic phase ( 2 a );

dissolving elementary sulfur decomposed from H 2 S in the organic phase ( 2 b );

crystallizing organic phase ( 2 b ) saturated with dissolved elementary sulfur by cooling down through a cooling unit ( 3 ) and then taken out of the cooling unit ( 3 );

supplying the organic phase ( 2 b ) purified from elementary sulfur back into the column reactor ( 2 );

passing H + ions into the aqueous acidic phase ( 2 a ) by a redox reaction in the interface ( 2 c ) of H 2 S gas with the one of the redox couple in the aqueous acidic phase that has a higher oxidation state than that of H 2 S;

transferring the aqueous acidic phase ( 2 a ) to a first chamber ( 5 A) of the photo-/electrochemical cell ( 5 );

subjecting the one of the redox couple, which is present in the aqueous acidic phase ( 2 a ) transferred to the first chamber ( 5 A), that has the lower oxidation state to oxidation regeneration;

passing the H + ions present in the aqueous acidic phase ( 2 a ) to a second chamber ( 5 B) by means of diffusion along a membrane ( 5 C) present in the photo-/electrochemical cell ( 5 );

reducing the H + ions passed to the second chamber ( 5 B) into H 2 gas;

taking the generated H 2 gas from the photo-/electrochemical cell ( 5 );

feeding back the regenerated aqueous acidic phase ( 2 a ) to the column reactor ( 2 ) to oxidize H 2 S into elementary sulfur.

18. The method according to claim 17 , characterized in that the elementary sulfur crystallized in the cooling unit ( 3 ) is passed through at least one filter ( 4 ) and removed from the cooling unit ( 3 ).