Patent EA-002246-B1 (EA)
Title: Method for direct oxidation in sulphur by catalytic process and in vapour phase of low content h2s in a gas
Inventor: LEDOUX MARC
IPC: C01B17/04
Filed: 1999-09-21
Abstract: 1. A method for direct catalytic oxidation in sulphur H2S contained in low concentration in a gas comprising combining the containing H2S gas with the gas containing free oxygen in an amount to form an O2/H2S-containing gas with an O2/H2S molar ratio ranging from 0.05 to 15, contacting with a catalyst for the selective oxidation of H2S to sulphur, wherein the catalyst comprises a catalytically active phase associated with a silicon carbide support and formed by at least one compound of at least one transition metal operating at temperatures, which are higher than the dew point formed by oxidation of H2S, wherein the active phase of a catalyst is formed by at least one oxysulphide of at least one metal selected from the group consisting of nickel, iron, cobalt, copper, chromium, molybdenum and tungsten. 2. The method according to claim 1, wherein a metal, forming the active phase of a catalyst by oxysulphide, is iron or a mixture thereof with one of the following metals: copper, nickel, cobalt, chromium, molybdenum or tungsten, wherein said mixture comprises preferably iron. 3. The process according to claim 1 or 2, wherein the H2S-to-sulphur oxidation reaction is carried out at temperatures between 180 degree C and 500 degree C. 4. The process according to claim 1 or 2, wherein the H2S-to-sulphur oxidation reaction is carried out at temperatures between 190 degree C and 300 degree C and more preferably between 200 degree C and 260 degree C. 5. The process according to any of claims 1 to 4, wherein the silicon carbide support of the oxidation catalyst forms at least 40% by weight of the catalyst and more preferably at least 50% by weight of the catalyst. 6. The process according to any of claims 1 to 5, wherein the active phase of the oxidation catalyst represents, in terms of weight of metal, 0.1 to 20% of the weight of the catalyst, more preferably 0.2 to 15%, nost preferably 0.2 to 7% of the weight of the catalyst. 7. The process according to any of claims 1 to 6, wherein the specific surface area of the catalyst, determined by the BET nitrogen adsorption method, has values ranging from 0.05 m<2>/g to 600 m<2>/g, more preferably from 0.1 m<2>/g to 400 m<2>/g. 8. The process according to any of claims 1 to 7, wherein the gas containing free oxygen is used in an amount to provide an O2/H2S molar ratio ranging from 0.1 to 10, more preferably from 2.5 to 8. 9. The process according to claim 8, wherein the H2S-to-sulphur oxidation reaction is carried out at temperatures between 1200 degree C and 260 degree C, the O2/H2S molar ratio between 3 to 7. 10. The process according to any of claims 1 to 9, wherein the times during which the gaseous reaction mixture is in contact with the oxidation catalyst, under standard temperature and pressure conditions, range from 0.5 to 20 seconds, more preferably between 1 and 10 seconds. 11. The process according to any of claims 1 to 10, wherein the H2S content of the gas to be treated is between 0.001% and 20% by volume, more preferably between 0.005% to 10% and most preferably between 0.01% to 5%. 12. A process according to one of claims 1 to 11, wherein the oxidation catalyst is obtained by a method comprising: -a first step, at which an oxidized precursor of a catalyst is produced carrying an imprignation of a support of silicon carbide by solution or sol of metal(s) desirable for an active phase in the form of salts, drying the imprignated support and calcinating the dried product at temperatures between 250 degree C to 500 degree C, operating, if nesessary, in an inert atmosphere; -a second step, at which a sulfonated precursor of a catalyst is produced subjecting the oxidized precursor of the first step to sulfuration by contacting with a sulfonating agent consisting of an elementary sulfur and/or gaseous H2S mixture and an inert gas, operating at temperatures between 250 degree C to 500 degree C during time sufficient for carrying out maximum metal(s) sulfuration of the catalyst active phase, and -a third step, comprising bringing into contact the sulfonated precursor of the second step to a gaseous oxygen-containing stream formed by an inert gas-carrier, comprising from 0.1% to 40% of oxygen and from 0% to 50% of water by volume at temperatures below 500 degree C, more preferably from 250 degree C to 450 degree C during from 0.2 to 3 hours, more preferably from 0.5 to 2 hours to form a metal oxysulphide phase. 13. The process according to claim 12, wherein H2S oxidation to sulfur is carried out in one or more reaction zones the catalyst of the H2S oxidation is formed directly in each oxidation zone as an operation preceding the H2S oxidation, putting in each oxidation zone an oxidized precursor of the catalyst obtained after the first stage subjecting the oxidized precursor to sulfonating by direct effect in the oxidation zone and then carrying out oxidizing treatment of the sulfonated precursor by gaseous oxygen-containing stream to form a catalyst with an oxysulphide phase, sulfonating and oxidizing treatment are carried out according to the second and the third steps of the catalyst preparation respectively. 14. The process according to any of claims 1 to 13, wherein the activity of the oxidation catalyst drops below the predetermined threshold value in the course of the H2S oxidation, the effectiveness of said catalyst is restored by subjecting the desactivated catalyst to oxidizing treatment, which comprises bringing into contact said desactivated catalyst with gaseous oxygen-containing stream, formed by the inert gas-carrier, comprising from 0.1% to 40% of oxygen and from 0% to 50% of water by volume at temperatures below 500 degree C, more preferably from 250 degree C to 450 degree C during from 0.2 to 3 hours, more preferably from 0.5 to 2 hours to form again a metal oxysulphide phase.