METHOD AND AGENT FOR DESULPHURISATION

Abstract: Sulphur compounds are removed from a gas and/or liquid stream by an agent comprising at least one compound of manganese and at least one compound of iron. Desulphurization agent comprising at least one compound of manganese and at least one of iron, present in relative molar proportions of about 8:1 to 1:8.

Description: METHOD AND AGENT FOR DESULPHURISATION The invention relates to desulphurisation and in particular to the purification of streams (liquid or gas or both) by the partial or complete removal of sulphur compounds, e.g. hydrogen sulphide, low molecular weight mercaptans, or the like therefrom. The invention may also be applied to the purification of air or other gas containing sulphur compounds. The invention relates to a method and a desulphurisation agent. In one aspect the invention provides a method of reducing the content of a sulphur compound in stream of gas and/or liquid, the method comprising contacting the stream with a desulphurisation agent comprising at least one compound of manganese and at least one compound of iron. The desulphurisation may be performed, for example, at a temperature from about ambient up to about 450°C, preferably from about 20°C to about 450°C, most preferably from about 40°C to about 150°C. Preferably the compounds are the oxides, hydroxides, carbonates, e.g. hydroxycarbonate or basic carbonate or the like of both manganese and iron. These active ingredients may be incorporated within a carrier of the invention by simple impregnation or impregnation/deposition, co forming, precipitation from aqueous solution or other techniques well known to those skilled in the art of catalyst preparation. The carrier may be alumina, sihca, alumino silicates or the like. The content of the carrier material will be in the range 1 to 40% by weight. Preferably the compounds are in the relative molar proportions of 8:1 to 1 :8, most preferably about 1 :1. In a preferred feature the desulphurisation agent comprises shaped particles. The particles may be presented in a variety of shapes and sizes preferably as spheres; extrudates, granules, tablets or the like. A binding agent such as cement, alumina, clay, sihca, orgamc resins or the like may be present to enhance the physical properties of the shaped material. The shaped material may require exposure to elevated temperatures to achieve the optimum bond strength. Preferably the agent includes a promoter which is one or more of potassium hydroxide, nickel hydroxide and sodium hydroxide, optionally with a derivative of zinc. The concentration of the promoter is preferably in the range of from about 1% to about 10%. The inclusion of copper or copper compounds has proved to be beneficial because it will scavenge lower concentrations of sulphur compounds and also remove arsine. In a further preferred feature the shaped desulphurisation agent is porous. The pore volume will be in the range of 0.1 to 0.6 ml/g, preferably 0.25-0.45 ml/g. It is recognised that the shaped porous materials should exhibit a significant level of macro porosity. The desulphurisation agent may be used in a fixed bed, a fluid bed or a moving bed. The choice of the reactor system will depend on generated requirements and the nature of the gas stream, e.g. sour feed. Particle sizes of about 3 to about 6mm are particularly useful in a fixed bed. In a fluid bed, the particle size is preferably in the range about 20 to about 120 microns, most preferably about 30 to about 100 microns. For the moving bed, the particle size is preferably in the range about 120 to 600 microns, most preferably about 200 to about 500 microns. The method of the invention may be enhanced by the incorporation of materials with sorption properties. Such materials may be added according to the physical form of the desulphurisation agent. They may be added on to the surface or within the pores of a porous desulphurisation agent or in the bulk phase. Such materials may be catalytically active. The materials (which may be included either singly or in combination) are preferably oxides, carbonates, sihcates, phosphates of alkah metals, alkaline earths, rare earths, Zn, Co, Ni, Mo, Cr, Cu, Ti, Zr, Si, Al, precious metals. The materials may be incorporated within the material of the invention by impregnation, deposition, coforming, precipitation techniques well known to those skilled in the art of catalyst preparation. The content of the sorption materials may range from about 0.5 to 40% by weight, preferably in the range 2 to 20% by weight. In a preferred feature of the invention, other reagents are associated with the desulphurisation agent to react with other substances present in the stream to be treated at from about ambient to about 250°C. One such reagent is an alkaline reagent such as alkah metal hydroxide or silicate, the alkah metal is preferably sodium. Such an alkaline reagent will react with halides or strongly acidic gases present in the sour feed such as SOx to form halide or sulphite respectively (which may be recovered later). The reagents may be impregnated into the desulphurisation agent or incorporated into the bulk phase by other means well known to those skilled in the art of catalyst preparation. The spent desulphurisation agent of the invention may be regenerated by exposure to an oxidising atmosphere e.g. air at elevated temperature. The presence of steam when regenerating may be beneficial. In another aspect the method of the present invention includes the further step of exposing the spent agent to oxidation at elevated temperature to remove the sulphur compounds and regenerate the agent for re-use. The sulphur compound to be removed may be hydrogen sulphide gas or a low molecular weight mercaptan such as propyl mercaptan. The hydrocarbon stream may be liquid or gas or both, examples being natural gas, town gas, industrial waste gas, coke oven gas, coal gas, liquid or gas from petroleum plant oil refinery. Effluent streams from biomass digesters, general industrial process may also be treated. The method may be performed at pressures ranging from about atmospheric to about 100 atmospheres without adverse effect. In another aspect the invention provides a desulphurisation agent comprising at least one compound of manganese and at least one compound of iron in the relative molar proportions of from about 8:1 to 1 :8 (Mn:Fe). In a further aspect the invention provides such an agent incorporating a promoter and in yet a further aspect the invention provides such an agent incorporating a sorption material. In order that the invention may be well understood it will now be described by way of illustration with reference to the following example. Example I Pellets of varying composition, as detailed below, were prepared by standard forming techniques, calcined at 450OC and allowed to cool. Component, Wt. % A B C D manganese dioxide 5 38 iron oxide 80 70 70 10 sodium hydroxide 10 5 2 binder 20 20 20 20 30 ml. of each sample were placed in a tubular reactor subjected to a flow (3 litres/hour) of nitrogen containing 20% hydrogen sulphide at ambient temperature and pressure and the time noted for 10 ppm hydrogen sulphide to be detected at the outlet of the reactor. The following results were obtained. Sample time mins A 62 B 74 C 92 D 330 It will be observed that when both Mn and Fe were present the time increased and that this increase was greatly improved when more manganese was present.

Claims: CLAIMS 1. A method of reducing the content of a sulphur compound in stream of gas and/or hquid, the method comprising contacting the stream with a desulphurisation agent comprising at least one compound of manganese and at least one compound of iron. 2. A method according to Claim 1 , wherein the contact is made at a temperature of from about ambient to about 450°C. 3. A method according to Claim 2, wherein the contact temperature is from about 20°C to about 450°C. 4. A method according to Claim 3, wherein the contact temperature is from about 40°C to 450°C. 5. A method according to Claim 4, wherein the contact temperature is from about 40°C to about 150°C. 6. A method according to any preceding Claim, wherein desulphurisation agent comprises an oxide, hydroxide or carbonate of each of manganese and iron. 7. A method according to Claim 6, wherein the relative molar proportions of manganese compound to iron compound are from 8:1 to 1 :8 (Mn:Fe). 8. A method according to Claim 7, wherein the relative molar proportions are about 1 :1. 9. A method according to any preceding Claim, wherein the manganese compound and the iron compound are presented together in the form of bonded particles. 10. A method according to Claim 9, wherein the particles are bonded by a bonding agent which is a cement, alumina or a clay; sihca; organic resin; or the like. 11. A method according to any preceding Claim, wherein the desulphurisation agent includes a promoter which is a hydroxide of a potassium, nickel and sodium, optionally with a compound of zinc. 12. A method according to any preceding Claim, wherein the desulphurisation agent includes copper or a compound thereof as a scavenger. 13. A method according to any preceding Claim, wherein a sorption material is present in or on the desulphurisation agent. 14. A method according to Claim 13, wherein the content of sorption material is from 0.5% by weight to about 40% by weight of the agent. 15. A method according to any preceding Claim, wherein the desulphurisation agent is present in the form of particles from about 3mm to about 6mm in a fixed bed. 16. A method according to any of Claims 1 to 14, wherein the desulphurisation agent is present in the form of particles from about 20 to about 120 microns in a fluid bed. 17. A method according to any of Claims 1 to 14, wherein the desulphurisation agent is present in the form of particles from about 120 microns to about 600 microns, in a moving bed. 18. A method according to any preceding Claim, wherein the desulphurisation agent is associated with an alkaline reagent to react with a hahde or strongly acidic gas in the stream. 19. A method according to Claim 18, wherein the alkaline reagent is an alkah metal hydroxide or silicate. 20. A method according to Claim 18 or 19, wherein the alkaline reagent is contacted with the stream at a temperature of from about ambient to about 250°C. 21. A method according to any preceding Claim, including the step of regenerating the spent desulphurisation agent. 22. A method according to Claim 20, wherein the spent agent is regenerated by contact with air or steam at elevated temperature. 23. A desulphurisation agent comprising at least one compound of manganese and at least one of iron, present in relative molar proportions of about 8:1 to 1 :8. 24. An agent according to Claim 23, wherein the molar proportions are about 1 :1. 25. An agent according to Claim 23 or 24, including a promoter. 26. An agent according to Claim 23, 24 or 25, including a sorption material. 27. An agent according to any of Claims 23 to 26, including an alkaline reagent.

Inventors: SAMBROOK RODNEY MARTIN, SAMBROOK, RODNEY, MARTIN
Applicants: DYTECH CORP LTD, SAMBROOK RODNEY MARTIN, DYTECH CORPORATION LTD., SAMBROOK, RODNEY, MARTIN
Application year: 1997
Main classification: B01D53
IPC codes: B01D53, B01J23, C10G25, C10K1, C10L3