CATALYST AND PROCESS FOR OXIDIZING HYDROGEN SULFIDE

Abstract: Catalysts comprising bismuth and vanadium compo­ nents are highly active and stable, especially in the presence of water vapor, for oxidizing hydrogen sulfide to sulfur or SO₂. Such catalysts have been found to be especially active for the conversion of hydrogen sulfide to sulfur by reaction with oxygen or SO₂.

Description: CATALYST AND PROCESS FOR OXIDIZING HYDROGEN SULFIDE The present Invention relates to a process for oxidizing H2S, and particularly to a process for catalytically oxidizing H2S to sulfur, S02, or both in the presence of a substantial proportion of water vapor. Current air pollution regulations arc very restrictive concerning the amount of H2S that may be dtscharged to the atmosphere. In some instances, gas streams may not be discharged to the atmosphere If they contain more than about 10ppmv of H2S. Thus, many processes have been developed to remove H25 from gas streams parlor to thelr discharge to the atmosphere. One method known In the art for removing H2S Involves catalytic oxidation, that is, a gas stream containing is Is blended with air or free oxygen, and the resulting mixture is then passed through a bed of catalyst particles under appropriate conditlons such that the H2S is converted to elemental sulfur vapor or S02, or both, as desired. One catalyst useful for the gas phase conversion of H2S to sulfur or S02 is disclosed In U.S. Patent No. 4,092,404; It comprises one or more vanadium oxides or sulfides supported on a refractory oxide such as alumina or silica-alumina. Another such catalyst is disclosed in U.S. Patent No. 4,012,486, whereln a catalyst having active components consisting of bismuth is used to catalytically incinerate H2S to S02. When compared, the bismuth catalyst of U.S. Patent No. 4, 012,486 will generally be found to be less active than the vanadla catalyst of U.S. Patent No. 4,092, 404 for oxidizing H25 to SO2. On the other hand, a bismuth catalyst Is much more stable than a vanadia catalyst at operating temperatures below about 6000 F. when H2S must be removed from a gas stream, such as an off-gas derived from a geothermal power plant, which contains water vapor at a water vapor partial pressure about 1.0 psia, usually at least 4.0 psia. In general, vanadla catalysts have satisfactory stability In the presence of water vapor at partial pressures below about 1.0 psia or at operating tem peratures above about 6000 F., but under the combined con editions of temperature below 6000 F. and water vapor pars tial pressures above about 1.0 psla, and particularly at 1.5 psla or above, vanadia catalysts deactivate rapidly. It Is belleved that the reason for this deactlvatton Is due to a compiexseries of chemical reactions involving the conversion of the vanadium oxide or sulfide active catalytic components to less active forms of vanadium, such as vanadyl sulfate $VOSO4). As stated above, vanadia catalysts are highly active for the oxidation of H2S and, as disclosed In U.S. Patent application Serial No. 700,513, filed June 28, 1976, such catalysts have proven most useful for oxidizing H2S to sulfur by reaction with either oxygen or SO2. In the presence of less than about 1.0 psia water vapor, vanadla catalysts have proven to be remarkably stable, providing high conversions of H2S to sulfur for a time period of more than I year with little If any deactivation being noticed. Despite the remarkable properties of vanadia catalysts, however, it is an object of the present invention not only to Improve the stability of vanadium-containing catalysts in the presence of water vapor but to substantially improve their activity for convertlng H2S. to sulfur. More specifically with respect to water vapor, it is an object of the invention to provlde a process for catalytically oxidizing H2S In the presence of water vapor at a partial pressure of more than about 1.0 psia, particularly above about 1.5 psla, and more particularly still, above about 2.0 psla. It Is yet another object of the invention to achieve the foregoing without oxidizing such components as H2, CO, NH3, and CH4 that might be present durlng the oxidation of the H2S. Other objects and advantages will become apparent from the following description of the invention. It has now been found that catalysts comprising bismuth and vanadium components are highly active and stable for the gas phase oxidation of hydrogen sulfide, especially In the presence of water vapor. Such catalysts combine the high activity of vanadla catalysts with the stability of bismuth catalysts. In addition, it has been found that the catalyst of the invention Is usually substantlally more stable In the presence of water vapor than catalysts comprising bismuth of vanadium alone, especially at operating temperatures below about 6000 F. The catalyst of the inv'-:ntion Is useful when H2S must be oxidized in the gas phase in the presence of water vapor at a partial pressure of more than about 1.0 psia. Because H2S produces an equivalent volume of water vapor for each volume of H2S converted to sulfur or S02, it will be understood that the invention is useful In a process whereln the water vapor partial pressure in the feed gas is less than about 1.0 psia initially but, during contact with the catalyst, increases above 1.0 psia. An advantage in the invention resides In the highly selective nature of the catalysts Components selected from the group consisting of H2, CO, NH3, and those saturated hydrocarbon gases containIng no more than 6 carbon atoms (i.e., light hydrocarbons) are not oxidized In the process of the Invention. Additionally, the oxidation of H2S, If performed at a temperature less than about 9000 F., produces essentially no S03. In addition to the foregoing, and perhaps most remarkable of all, vanadium-bismuth catalysts have been found to provide higher activity than comparable vanadia catalysts for the conversion of H2S to sulfur. This discovery came as a distinct surprlse, for vanadfa catalysts are themselves highly active for the conversion of H2S to sulfur. B@t@compa@ab@@ vanadium-bismuth.catalys@s prove not only to be more active than vanadia catalysts but substantlally more so. For example, as will be shown.hereinafter in Example VI, where prior art vanadla catalysts consisting essentially of about 10 wt.% vanadium pentoxide on silica-alumina are known to be active for lighting off the reaction between H2S and oxygen to produce sulfur at a temperature of about 3750 F., vanadium-bismuth catalysts having the same support but comprising 8.7 wt.% vanadium components and 12.9 wt.% bismuth components prove active for lighting off the converslon of H2S to sulfur at temperatures below 3000 F. All references hereln to catalysts containing vanadium and bismuth or to catalysts containing vanadium and bismuth components include within their meaning catalysts active for oxidizing H2S containing (I) elemental vanadium and elemental bismuth, (2) elemental vanadium and one or more bismuth compounds, (3) elemental bismuth and one or more vanadium compounds, (4) one or more vanadium com pounds @@d'one or more bismuth compounds, (5) one or more compounds of bismuth and vanadium (e.g., a bismuth vanadate), or (6) a combination of any of the foregoing. Active catalysts for use in the Invention com- prise vanadium and bismuth as the essential active components. The essential active components may be present as the elements V and 81, or as a mixture of individual vanadium and bismuth compounds (for example, B12S3 admixed with V2S5), or as a compound of both bismuth and vanadium, such as Bi(V03)3 or BiVO4. Alternatively, the catalyst may contain any combination of elements and compounds of vanadium and bismuth as the essentlal active components. Preferred catalysts contaln at least one vanadium oxide or sulfide (e.g., V205, V203, V2S5, and V2S3) and at least one bismuth oxide or sulfide (e.g., BiO, Bi2O3, Bi2O5, Bi2S3, and Bi2O4). The most highly preferred catalyst contains at least some bismuth vanadate (I.e., as the orthovanadate, BiVO4 or Bi2O3V2O5, metavanadate, Bl(V03)3, or pyrovanadate Bi4(V207)3). The typical catalyst contains vanadium and bismuth components in an Intimate mixture, and although the catalyst may consist essentially of such a mixture, it is highly preferred that the vanadium and bismuth components be composited, as by Impregnatlon or comulling, with a carrler materlal. The carrler (or support) materlal usually comprl- ses a porous refractory oxide, including, for example, such preferred refractory oxides as alumina-slIIca, zlrconla, titania, magnesia, slllca-alumina, silica-zirconla, sillca- titania, silica-magnesia, sillca-zlrconla-titanla, and com binations thereof. Suitable refractory oxides include acidic metal phosphates and arsenates, such as aluminum phosphate, boron phosphate, alumlnum arsenate, chromium phosphate, etc. Other sultab@e supports include the hydrophobic, crystalline silicas, such as the silicalites taught in U.S. Patent No. 4,061,724. (As used hereln, a refractory oxide Is hydrophobic if It is capable of absorbing no more than about 0.5 cc/gm of water.) Also suitable are the amorphous and crystalline aluminosil icate zeolites, whether naturally-occurring or synthetlcally made. The most useful crystalline aluminosilicate zeolites are ion-exchanged so as to remove essentially all ion-exchangeable alkall or alkaline earth components. Of particular usefulness are the crystalline alumtno-sillcate zeolites which are hydrophobic and essen tlally free of alkali and alkaline earth components. Illustrative of such zeolites are the ZSM-5 zeolite disclosed In U.S. Patent No. 3,702,886, the ZSM-II zeolite disclosed In U.S. Patent No. 3,709,979, and the several hydrophobic zeolites disclosed in U.S. Patent No. 4,019,880. Such zeolites are characterized by high ratlos of silica-to- alumina. The most highly preferred refractory oxide carrier is silica-alumina when the alumina is present In a proportion of at least 10 weight percent, preferably between about 20 and 30 weight percent. Catalysts prepared from such supports are usually more active for oxidizing H2S than are catalysts prepared from most other refractory oxides. In addition, such supports are highly resistant to sulfatlon, that is, In the presence of S03 and/or S02 plus 02, such supports are resistant to the formation of aluminum sulfate and the consequent loss of surface area, crushing strength, and activity. In general, It can be expected that catalysts prepared from silica-alumina supports containing at least 10 weight percent alumina will ex perlence little if any deactivation due to suifatlon under the conditions of the process hereinafter described. There are several methods known in the art by which the vanadium and bismuth components may be composited with a refractory oxide support. One such method involes Impregnatlon, that Is, a suitable support, such as pellets or extrudates of 75% SiO2-25% A1203 silica-alumina, Is contacted with a solution of ammonium vanadate (or other soluble vanadium compound), drled at an elevated temperature (usually about 2300 F.), and then contacted with a solution of a bismuth salt, such as an acidic solution of a bismuth nitrate or chloride. The composite may also be prepared by any of a variety of comulllng techniques. A typical procedure involes mulling silica-alumina with sold ammonium metavanadate, solid bismuth nitrate, and sufficient water to create a past suitable for extrusion through a dle. More preferably, either or both of the vanadium and bismuth salts may be added to the mulling mixture in solution form. In a preferred embodiment, a mixture of silica-alumina, a solutlon of bismuth nitrate in dllute nitric acid, and an aqueous solutlon of ammonium metavanadate are comulled. Alternatively, a silica-alumina or other refractory oxide Is comulled, for example, with an ammonium metavanadate solutlon, then drled or calcined at an elevated temperature, and then comulled with an aqueous solution of a bismuth salt, such as a solutlon of bismuth nitrate In dilute nitric acid. Comulilng may also be accomplished by mixing silica-alumina with one or more bismuth vanadates In the presence of water. Alternatively still, the composite may be prepared by a combination of impregnation and compiling techniques, as by impregnating silica-alumina with ammonium vanadate, calcining, and then comulllng with an acidic solu tlon of bismuth nitrate or chloride. After a composite is prepared by one of the foregoing impregnation and/or compiling methods or thelr equivalents, the composite Is calcined, usually at a temperature between about 7000 and about 16000 F., preferably 900 -1200 F. Calcination produces a catalyst containing vanadium and bismuth largely In the form of the oxides thereof, but usually the 700 -1600 F. calcination also produces sufficient bismuth vanadate, usually in the form of monoclinic bismuth orthovanadate (BiVO4), to be detected by X-ray diffraction analysis. Blsmuth orthovanadate and other bis. muth vanadates are usuaily produced even when impregnation or comulling Is accomplished wlthout the dellberate addition of a bismuth vanadate. For example, when sillca-alumina Is comulled (as In Example I herelnafter) with ammonium metavanadate, then further comulled with an acidic solution of bismuth nitrate, extruded cut Into particulate form, and then calclned at 900 -1000 F., the flnal product contalns sufficient bismuth orthovanadate to be detected by X-ray diffraction analysis. Although the invention is not to be so limited, it Is belleved that catalysts containing bismuth vanadate are more active and more stable-than catalysts containing no bismuth vanadate. Such is especially believed to be the case with respect to bismuth orthovanadate (BiVO4) It is also belleved that the reason the catalyst usually demonstrates higher stability in the presence of water vapor than Is the case for catalysts containing only vanadium components or only bismuth components is due to the presence of bismuth vanadate. Hence, catalysts containing a bismuth vanadate, and particularly bismuth orthovanadate, are preferred in the invention. Flnished catalysts hereln should contaln at least 5.0 weight percent of vanadium and 5.0 weight percent of bismuth, calculated as V205 and Bi203, respectively. It has been found that catalysts containing less than 5.0 weight percent of either metal, while more active or stable than catalysts containing either vanadium components or bismuth components alone, are somewhat less active and less stable than catalysts containing at least 5.0 weight percent of each component. Preferably, the catalyst contains between 5 and 15 weight percent of each components, but it may, If desired, contain up to 40 weight percent of each component. A highly preferred catalyst contalns between about 7 and 15 weight percent vanadium as V205 and between about 8 and 20 weight percent bismuth as Bi2O3, with the most highly preferred catalyst containing at least 8.0 weight percent vanadium components as V205 and at least 10 weight percent bismuth components as Bi2O3. (All calcu latins hereln with respect to the proportions of active metal components on the catalyst are reported as the weight percent of vanadium and bismuth as V205 and Bi2O3, respectively. Thus, a catalyst particle weighing 5 grams and containing elemental vanadium, elemental bismuth, bismuth sulfide (B12S3), vanadium sulfide (V2S5), and bismuth ortho vanadate (BIV04), each In a weight of 0.1 grams, contatns vanadium components In a proportion of 5.52 weight percent as V205 and bismuth components In a proportion of 5.48 weight percent as Bi2O3.) The following two Examples demonstrate preferred procedures for preparlng catalysts useful in the invention. EXAMPLE I Four hundred twenty-one grams of 75% 5102 25% Al2O3 silica-alumina, commercially sold by the Davlson Chemical Divislon of W. R. Grace & Co. as high alumina cracking catalyst, were placed In a steel muller, to which was added 44.2 grams of ammonium metavanadate (NH4VO3) and 6 grams of powdered methylated cellulose. The mixture was mulled for 45 minutes. A solution was then prepared by dis- solving 88.8 grams of bismuth nitrate (Bl(N03)35H20) in a liquid consisting of 200 cc. water and 32 cc. concentrated nitric acid. The solution was added to the previously mul- led mixture, and mulling was continued for 15 minutes. An extrudable paste was then formed by mulling with 71 cc. of water for 15 minutes. The resulting paste was then extruded through a 1/8 Inch dlameter die and cut Into particles having lengths between about 1/8 and 1/2 Inch. The extrudates were then allowed to dry overnight at 2300 F. The extrudates were then calcined in the presence of air at 9320 F. for 2 hours. The resulting catalyst contacted 9.1 weight percent vanadium components (as V205) and 11.2 weight percent bismuth components as Bi2O3. The catalyst contained an X-ray detectable proportion of bismuth orthovanadate. EXAMPLE II Sufficient ammonium metavanadate (NH4V03) was mulled with the high alumina silica-alumina described in the preceding Example so that1 after extrusion and cutting Into 1/8 inch dlameter by 1/16-1/2 inch cylindrical extrudates and calcinatlon at a temperature of about 9320 F. for 2 hours in air, the resulting product contained 10 weight per cent vanadium components as V205. One hundred grams of such product were then contacted with a solutlon prepared by dissolving 35 grams of bismuth nitrate (Bi(N03)3 5H20) in a mixture of 100 cc. water and 15 cc. concentrated nitric acid to which was added sufficient water to provide a solution of 120 cc. volume. The solution was allowed to contact the extrudate material for two hours to insure full tmpreg- natlon. The extrudate material was then filtered, drled overnight at 2300 F., and calcined at 9320 F. for two hours In the presence of air. The resulting catalyst contacted an X-ray detectable proportion of bismuth orthovanadate-and further contained 8.63 weight percent vanadium components as V205 and 11.6 weight percent bismuth components as By203. Catalysts prepared by the foregoing methods or their obvious equivalents have been found to be highly active for the gas phase oxidation of H2S to elther S02, sulfur, or some percentage combination of both, as desired. In additlon, such catalysts are highly selective throughout the temperature range of 2500-9000 F., oxidizing H2S with out forming essentially any SO3 and without oxidizing any H2, CO, NH3, or light hydrocarbons which may also be present with the H2S. Of particular Importance is the fact that the catalyst Is remarkably stable In the presence of water vapor. The life of the catalyst for oxidizing H2S at temperatures below about 6000 F. In the presence of water vapor at a partial pressure of more than about 1.0 psla Is at least 90 days, usually at least one year. The catalyst Is especially useful for oxidizing H2S in the presence of water vapor at a partial pressure of at least 1.5 psla, preferably at least 4.0 psla, and particularly at water vapor partial pressures up to about 10.0 psla. Useful results have been obtained, for example, In converting H2S to elemental sulfur by reaction with oxygen at a temperature of about 3800 F. in the presence of water-vapor at a partial pressure of about 9.0 psia. The choIce as to whether or not the H2S In a given gas stream Is to be converted to elemental sulfur or SO2 will most likely depend upon local air pollutlon regulatlons. Typically, the maximum concentration of H2S allow able for discharge to the atmosphere Is about 10 ppmv whtle S02 may be discharged In a maxlmum concentration varying between about 500 ppmv and 2.0 vol.%. Hence, in- cineratlon, i.e., conversion of H2S to S02, will usually be directed to gas streams containing between about 10 ppmv and.2.0 vol.% H2S, while the typical gas stream treated for conversion to elemental sulfur will contain at least about 500 ppmv H2S, usually 500 ppmv to 10.0 vol.% H2S, preferably 50 ppmv to 5.0 vol.% H2S, -and most preferably 500 ppmv to 2.0 vol.% H2S. Normally, the gas streams treated In the process of the invention contain, in additlon to H2S, any of such components as N2, C02, CO, H2, S02, 02' Ar, NH31 H2O, and light hydrocarbons. Typical gas streams for treatment herein Include such H2S- containing gas streams as sour natural gases, off-gases derived from geothermal steam, and high temperature, gasified coal or gasifyed residual oil. The gas stream may also contain such sulfur-contalning components as COS, CS2, and light mercaptans (i.e., saturated mercaptans containing no more than six carbon atmos). If such sulfur-contalning components are present, It is preferred that the gas stream be pretreated by the process disclosed In U.S. Patent No. 3,752,877, herein Incorporated by reference. According to this process, CS2, COS, and light mercaptans, along with SO2 if present, are simultaneously converted at elevated temperatures (usually 3000 to 9000 F.) to H2S by reaction with H2 and/or water vapor In the presence of a catalyst comprising one ore more active catalytic components of Co, Mo, Fe, W, Ni, with combinations of Co with Mo or Ni with Mo being most preferred. The pretreated gas stream will then contaln H2S as essentially the only gaseous sulfur component and may be treated by a pro- cess described hereln so that the H2S may be converted to SO2 and/or elemental sulfur as desired. A gas stream especially sulted to the foregoing pretreatment method is a Claus tail gas. Other gas streams which are preferably pretreated prlor to contact with the catalyst of the invention are those containing olefinsoraromatics. Olefins deactivate the catalyst herein by forming gums that deposit on the catalyst surfaces, and aromatics such as benzene, when present in significant proportIons, e.g., 100 ppmv, deactivate the catalyst when the operating temperature is below about 3500 F. Both types of deactivation, however, are only temporary, the oleo in deactivation being overcome by high temperature oxidation of the gum-containing catalyst and the aromatics deactiva tion by raising the operating temperature above 3500 F. Alternatively and more preferably, gas streams containing aromatic or oleo in components are pretreated so as to remove these deleterious components prlor to contact with the catalyst of the invention. One such pretreatment method, particularly suitable for gas streams containing olefines, Is catalytic hydrogenation under the conditlons and with the catalyst hereinbefore speclfled for gas streams containing S02, CS2, COS, and light mercaptans. Gas streams to be treated by Incineration should either contain sufficient oxygen or be blended with sufficlent oxygen or air so as to provide at least the stoichio- metric proportion required for: (I) 2H2S + 3 2 2S02 + 2H20. More preferably, oxygen is present in a proportion in excess of stoichiometric, usually In a proportion between about 1.1 and 2.5 times the stoichiometric proportion. Other condi- tions usually employed in incinerating H2S in an adiabatic or isothermal reactor Include (a) operating pressures between about 5 and 500 psia, with pressures of 15-75 psla being preferred, (b) Inlet operating temperatures In the range of 250 -900 F., with temperatures below about 6000 F. and especlally below about 4500 F. being preferred, and (c) space velocities between 100 and 50,000 v/v/hr, with 5005000 v/v/hr being preferred. Operating conditlons are ap proprlately adjusted so that at least 90% of the H2S is incinerated to SO2. Preferably, the operating conditions are adjusted so that essentially all the H2S is incinerated. Conditions known to produce essentially full conversion of H2S to S02 include: 4500 F., 50 psia, 2000 v/v/hr (gas volume calculated at 60 F.), 2.2 times the stoichiometric proportlon of air, and 2700 ppmv H2S in the feed gas. The following Example lll demonstrates the sultabillty of these conditions. EXAMPLE 111 A feed gas stream-having a composition shown in Table I was-blended at a rate of 460 scc/mtn (gas volume measured at 600 F.) with water vapor fed at a rate of 40 scc/ min and air fed at the rate of 19.8 scc/mln. The resultant gas mlxture,rhaving a water vapor content of 7.7 vol.% and an oxygen content of about 0.80 vol.% (2.23 times stoichio- metric) was then passed for 15 days at a pressure of 50 psig, a constant temperature of 4500 F., and a space velocity of about 2000 v/v/hr through an Isothermal catalytic reactor containing 15 cc. of catalyst particles comprising 11.6 weight percent bismuth components (as Bi2O3) and 8.6 weight percent vanadium components (as V205). The catalyst was prepared as described In Example II, and the water partial pressure within the reactor was about 5.0 psia. The product gas was analyzed on the 15th day by approprlate mass spectrometrlcal techniques, and the results are reports on an anhydrous basis In Table 1. As shown, the H2S was completely converted to S02, and no H2 or methane was oxidized. The S03 content of the effluent gas was determined to be from 3 to 5.0 ppm. TABLE I Feed Composition Product Composition Hydrogen 873 ppmv 838 ppmv Methane 1.68 vol.% 1.60 viol. Nitrogen 0 ppmv 2.77 tol. Oxygen 0 ppmv 0.43 viol. Argon 3 ppmv 365 ppmv Carbon Dioxide 97.96 vol.% 94.85 viol. Hydrogen Sulfide 2717 ppmv 0 ppmv Methyl Mercaptan 2 ppmv 0 ppmv Carbonyl Sulfide 4 ppmv 0 ppmv Sulfur Dioxide 36 ppmv 2212 ppmv Carbon Disulfide 0 ppmv 0 ppmv Total Sulfur Clom- pounds as SO2@ 2759 ppmv 2212 ppmv 1. Note: The reason a lower concentration of total sulfur compounds was found in the product gas than In the feed was due to dilution by the blend of air oxidant and also by the fact that on the 15th day of operation the H S concentratlon In the feed was somewhat lower than shown In Table I. EXAMPLE Six differently prepared catalysts were tested under the conditions of Example lll to determine how active and stable they were for IncineratIng H2S in the presence of 50 psla water vapor pressure. The six catalysts were prepared as follows: 10 weight percent V205 on silica-alumina A mixture of ammonium vanadate and the high alu mina cracking catalyst described In Example I were mulled In the presence of sufficient water to create a paste suitable for extrusion. The paste was ex truded through a 1/8 Inch die, cut into pleces about 1/16-1/2 Inch In length, drled at 230a F., and calcined in air at 9320 F. for two hours. The catalyst consisted of 10 weight percent vanadium components (calculated as V205) and silica-alumina (75% sillca-25% alumina). 36.6 weIght percent V205 on silica-alumina One hundred and eight grams of ammonium meta vanadate, 291 grams of the high alumina silica alumina described In Example I, and 7.74 grams of methylated cellulose were mulled In the pre sence of sufficient water to produce an extrud able paste. The paste was then extruded and cut into 1/8 Inch diameter by 1/16-1/2 Inch long cylindrIcal pieces. The extrudates were dried overnight at 2300 F. and calclned at 9320 F. for two hours in the presence of air. The catalyst so produced contacted 36.6 weIght percent vana dlum components (calculated as V205) on silica alumina (75% SiO2-25% A12O3). @0.2 weight percent Bi2O3 on alumina This catalyst was prepared according to a method sImilar to that taught In Example I of U.S. Patent No. 4,012,486. The procedure util sized was as follows: 17 gm BIC13 was dissolved In 40 cc. water to which was added 40 cc. concentrated hydrochloric acid. The solution was then diluted with 100 cc. water. The solution so produced was allowed to contact 100 grams of gamma alumina 1/16 inch diameter extrudates for two hours. The excess liquid was then decanted off, and the Impregnated extrudates were washed with a solutlon consisting of 30% concentrated NH4OH and 70% water until the extrudates were chloride free. The extrudates were then washed with 500 cc. water and calcaned for 2 hours at 9320 F. The catalyst contalned 102% bismuth components (calculated at Bi2O3) supported on gamma alumina. 4.5 weight percent Bi2O3-9.4 weight percent V2O5 on silica alumina This catalyst was prepared by first preparing the 10 weight percent V205 on sillcaalumina catalyst.as described above. One hundred grams of this catalyst was contacted with a solution prepared by first dissolving 11.6 gm bismuth nitrate In 100 cc. water to which was added 5 cc. concentrated nitric acid, and then further adding sufficent water to make the solutlon up to 120 cc. The contacting time was 2 hours, after which the excess liquid was decanted off. The Impregnated extrudates were then drled at 2300 F. overnlght and calcined for 2 hours at 9320 F. In the presence of air. The finished catalyst contained 4.5 weight percent bismuth components (calculated as B1203) and 9.4 weight percent vanadium components (calculated as (V2O5). By X-ray diffraction analysis, It was determined that the finished catalyst contained bismuth orthovanadate. 7.95 weight percent Bi2O3-9.0 weight percent V2O5 on silica alumina This catalyst was prepared according to the method shown above f6r the 4.5 weight per@ cent B1203-9.4 weight percent V205 catalyst except that the impregnating solutlon was pre pared as follows: 23.2 gm bismuth nitrate were dissolved in 100 cc. of water plus 10 cc. nitric acid. The solution was then sufficiently dlluted with water to provide a total volume of 120 cc. The finished catalyst contained 7.95 weight percent of bismuth components (as B1203) and 9.0 weight percent vanadium compo nents (as V205). The catalyst was found by X-ray diffraction analysis to contain bismuth orthovanadate. 11.6 weight percent Bi2O38.63 weight percent V2O on silica-alumina This catalyst was prepared according to the method shown in Example II. Each of the foregoing catalysts was utilized to incinerate H2S to SO2 under the conditions recited in Example III. The only condition was was varled for the Individual catalysts was operating temperature. After operating with the various catalysts for several days duration at temperatures varying between about 4500 and 5100 F., the stabillty of each catalyst was determined by comparlng the concentration of unreacted H2S in a sample of the product gas at a specified operating temperature early In the run versus the concentratlon of unreacted H2S in a sample of the product gas produced at the same specified temperature later In the run. The data so obtained are tabulated in Table ll, and the stabilitles of the various catalysts, in terms of the increase of unreacted H2S in the product gas per day, are also tabulated In Table II. As shown, the catalysts which proved most stable were those consIsting of bismuth components or bismuth and vanadium components as the essential active catalytic components. Catalysts containing only vanadium components as the essential active catalytic components deactivated at unacceptably high rates. The most stable catalysts were those containing bismuth and vanadium components In proportions of at least about 8.0 weight percent and 7.0 weight percent, respectively. Such catalysts proved remarkably more stable than the rok or 36.6% V205 catalyst and roughly twice as stable as the 102% Bit203 catalyst. Also significant is the fact that the two catalysts contalning at least about 8.0 weight percent bismuth components and at least about 7.0 weight percent vanadium components maintained an H2S concentration in the product below about 3.5 ppmv in comparison to about 6 ppmv for the vanadium-bismuth catalyst containing only 4.5 weight percent bismuth. Many environmental regulations permit no more than about 10 ppmv of H2S to be discharged to the atmosphere, and It can be seen that the two vanadium-bismuth catalysts contalning at least about 8.0 weight percent bismuth components provide activity and stability that will insure agalnst reaching such high levels of H2S in the product gas whereas the 4.5 weight percent bismuth-9.4 weight percent vanadium catalyst is less suitable for this purpose. Of special note is the high stability of the 11.6 weight percent bismuth-863 weight percent vanadium catalyst. Because of the high stability and high activity of this catalyst, It and other catalysts containing at least 10 weight percent bismuth components, calculated as Bi203, and at least 8.0 weight percent vanadium components, calculated as V205, are most highly preferred In the invention, EXAMPLE V To compare the Initial activities of the catalysts of the invention with those of the prlor art, data comparing the product H2S obtained at various temperatures in the runs of Example IV prlor to any significant cata TABLE II ppmv H2S in ppmv H2S in Deactivation Product at Product at Operating t2-t1 Rate , Time, t1 Time, t2 Temperature, F. Days ppmv H2S/day Catalyst 10% V2O5 1.5 46.8 500 7.5 6.04 36.6% V2O5 1.5 51.5 #450 16.9 2.96 10.2% Bi2O3 3.3 12.2 510 14.1 0.63 4.5% Bi2O3-9.4% V2O5 2.9 6.0 450 9.9 0.31 7.95% Bi2O3-9.0% V2O5 1.4 3.5 450 6.0 0.35 11.6% Bi2O3-8.63% V2O5 0.@ 3.0 450 11.0 0.23 1. Deactivation Rate = (ppmv H2S in product at t2 - ppmv H2S in product at t1) # (t2-t1) days. lyst deactivation were tabulated in Table 111. Also tabulated in Table 111 were data obtained from an experiment run under the same conditions of Example lll but using a catalyst consisting of 13.0 weight percent Bi2O3 and silica-alumina $75% SiO2-25% Al2O3), which catalyst was prepared by Impregnating silica-alumina extrudates with a bismuth nitrate solution followed by calcination at 932C F. for two hours in the presence of air. As shown In Table lll, the vanadia and vanadium bismuth catalystshad comparable activities under the condi- tions of the experiment@ leaving almost no unreacted H2S at temperatures in the 420 -450 F. range. On the other hand, the 10.2% and 13.0% bismuth catalysts were only useful at temperatures above about 500a F. At temperatures in the 490 -500 F.ranqe, the two bismuth catalysts both showed evidence of loss of activity, with unreacted H2S being as high as 5C ppmv. Thus, the vanadia and vanadium-bismuth containing catalysts exhibited substantially better activity for the conversion of H2S to SO2 than the catalysts containing only bismuth components as the essential active catalytic components. TABLE 111 Catalyst Temperature, F. ppmv H2S 10% V2O5 445 4.4 490 3.4 500 1.5 36.6% V205 400 25 410 17 420 4.8 440 1.5 10.2 Bi2O3 500 50 510 11.8-13.4 520 3.3-8.6 530 3.6 13.0% Bi2O3 490 17.1 500 1.0 510 0.9 4.5% B1203-9.4% V2O5 440-450 F. 1.7-6.0 795% Bi2O3-9.0% V2O5 450-460 F. 1.1-3.5 11.6% Bi2O3-8.63% V2O5 450-470 F. 0.3-4.5 The catalysts of the Invention may also be util- sized to oxidize H2S to elemental sulfur as well as for tn- cineration to S02. To produce elemental sulfur, conditions are usually chosen for adiabatic or isothermal reactors from the following ranges: 2500 to 900 F., 100 to 10,000 v/v/hr, and 5 to 75 psia, preferably from the following ranges: 2750 to 4750 F., 200 to 2500 v/v/hr, and 15 to 30 psia,and most preferably: 2750 to 4250 F., 500 to 1500 v/v/hr, and 15 to 20 psla. In addition, the In let temperature Is preferably malntalned below about 4000 F., most preferably below 3500 F., with at least some H2S being converted to elemental sulfur below such temperatures. An oxidant gas Is also necessary, so oxygen, usually supplled In the form of air, Is blended with the feed gas stream so as to produce sulfur vapor according to the following reaction: (ll) 2H2S + O2 2S + 2H2O Most preferably,the amount of air or oxygen so blended with the feed gas is such that oxygen is present in a proportion near or at the stoichiometric proportion for Reaction (II), usually between about 0.9 and 1.1 times the stoichiometric proportion. As is well-known, the highest possible conversions of H2S to sulfur are accomplished when oxygen is available In its stoichiometric proportion. Also contributing to high sulfur yields are low water vapor partial pressured and temperatures below about 4750 F., particularly below about 4500 F., with sulfur yields increasing with decreasing temperature and decreasing water vapor partial pressure. It is, of course, well-known that S02 may be used in place of oxygen for the conversion of H2S to sulfur, the sulfur being formed by the following reactIon: (111) 2H2S + S02 3S + 2H20 Thus, if S02 Is present in the feed gas stream in any H2S to SO2 ratio greater than 2.0, oxygen need only be added in an amount sufficient to react with the H2 S not converted by Reaction (ill). In other words, if the ratlo of H2S tc S02 is greater than 2.0 then the stoichlometric proportion of oxygen is that proportion sufficient to provide a molar or volumetric ratlo of H2S to (SO + 02) equal to 2.0. For feed gases Inherently containing H25 and SO2 In an H2S to S02 ratio less than 2.0, the highest possible conversions to sulfur are obtained by firstly pretreating the feed so as to convert the SO2 to H2S,'as by the method shown hereinbefore in U.S. Patent No. 3752,877 and then blending the pretreated gas with sufficlent oxygen or air to provide an H25 to O2 ratlo equal to 2.0. For feed gases containing H2S to 502 in a ratio equal to 20, no pretreatment or addition of oxygen Is necessary; the catalyst may be used for the direct conversion of H25 to sulfur vla Reaction (lll). In vlew of the foregoing, It should be apparent that.when elemental sulfur Is desired, SO2 may be utilized as an alternative oxidant to oxygen. That Is, for any gas stream containing H2S, elemental sulfur may be produced herein by blending either S02 or oxygen oxidant with the gas stream such that a ratio of H2S to oxidant of 2.0 is provided. However, oxygen is inherently superior to S02, not only because of Its ready avallability In the form of air but also due to the higher conversions to sulfur obtain- able therewith. A comparlson of Reactlons (ll) and (III) reveals that, for the same amount of H2S converted to sulfur, 50% more sulfur is formed by Reaction (III) with SO2 oxidant than by Reaction (II) with O2 oxidant. The formation of 50% more sulfur by Reaction (lll) necessitates higher operatng temperatures for Reaction (111) than for Reaction (II) if the sulfur vapor dew point is not to be exceeded. But at operating temperatures below 10000 F., the conver simon of H2S to sulfur decreases with Increasing temperature. Thus, because H25 can be converted to sulfur by Reaction (II) at a lower temperature than Reaction (liy) without exceeding the dew point, an inherent advantage i.e., a higher conversion - is obtained when oxygen is used as oxidant than when S02 Is utilized. Whether oxygen or S02 Is utilized as oxidant, it will be found that the catalyst of the invention is highly useful for converting H25 to elemental sulfur. The percentage conversion in any given situation, of course, will depend upon such factors as operating temperature, operat ing pressure, water vapor partial pressure, and choice of oxidant. But the vanadium-bismuth catalysts disclosed hereinbefore usually provide a conversion of H2S to elemental sulfur within 10%, often within 5%, of theoretical. And because of thelr high activity for converting H2S to sulfur, the vanadium-bismuth catalyst of the Invention provideos high converslons of H2S to sulfur under lower operating temperature and/or higher space velocity conditions than are required for comparable prior art catalysts, such as the vanadla catalyst disclosed in U.S. Patent Appllca tion Serlal No. 700,513 filed June 28, 1976. The following Example demonstrates the high activity of vanadium-bismuth catalysts for oxidizing H2S to elemental sulfur. EXAMPLE VI A catalyst was prepared containing 8.7 weight percent vanadium components, as V205, and 12.9 weight percent bismuth components, as B1203, and the balance being a support consisting of silica-alumina having a 25% by weight alumina content. The catalyst was in particulate form, had a surface area of 239 m2/gm, and a compact buik density of 0.67 g/cc. (This catalyst was prepared in a manner very similar to that described in Example 11.) The foregoing catalyst (950-gm) was charged to an geothermal reactor and utilized to treat a feed gas containing (on an anhydrous basis) about 99% CO2 and H2S In a concentration varying between about 750 ppmv and 1200 ppmv. Alr was blended with the feed gas such that stolchio- metric oxygen was available within a 10% tolerance to oxldize the H2S In the feed gas to sulfur. Elemental sulfur produced in the reactor was removed therefrom in the vapor form and recovered by condensation. The experiment was conducted over a time perlod of more than 5 months, and the data shown in Table IV were derived from analyses of samples of the feed and product gases when the operating conditions were those shown in Table IV. It is noted with respect to the foregoing exper iment that the catalyst throughout the run evinced no deactivatlon, except when the operating temperature fell below the sulfur vapor dew polnt temperature and sulfur deposited on the-catalyst. Such deactivations, however, were only temporary, elevated temperatures restoring the catalyst to full activity. As shown by the data in Table IV, the vanadium bismuth catalyst of the invention Is active for lighting offthe conversion of H2S to sulfur at temperatures below 3000 F. This result is considered surprising for a number of reasons, not the least of which Is that a comparable parlor art catalyst -- and one known to be highly active for the conversion of H25 to elemental sulfur, I.e., a 10% V205 on 75% SiO2-25% A1203 catalyst -- is active for light ing off the oxidation of H2S to sulfur In the presence of water vapor at partial pressures less than about 0.7 psia only at temperatures at or abode about 2750 F. Thus, the catalyst of the invention proves to be substantially more active than comparable vanadia catalysts for the conversion of H2S to elemental sulfur, and such is yet more surprlslng when the fact the foregoing experiments were conducted with water vapor at partial pressures between about 2.5 and 50 psia is taken into consideration. As those skilled In the art are aware, increasing the amount of water vapor tends to Increase the light-off temperature for a catalyst by Increasing the amount of water vapor absorbed on the catalytic surfaces, thereby reducing the amount of absorbed H2S and 02 (or S02). Yet despite the adverse condition of 3.0 psla water vapor, the catalyst of the invention stlil exhlbited activity for lighting off the reaction of H2 S with oxygen at about 2850 F. whereas a comparable vanadia catalyst under the more favorable condition of less than 0.7 psla water vapor is useful only at temperatures at or above about 3750 F. Another surprising aspect of the invention as shown by the data In Table IV is the high stability of the vanadium-bismuth catalyst in the presence of water vapor. As shown by the data in Table il, vanadia catalysts deactivate rapidly In the presence of water vapor at temperatures TABLE IV Sample No. 809 1232 1520 1544 1568 1716 1764 2130 2150 2322 Water Vapor Pressure, psia 3 3 3 3 3 5 5 5 2.5 5.0 Operating Pressure, psia 300 300 300 300 300 300 300 300 150 300 Operating Temperature, F. 381 334 305 295 285 310 300 410 410 410 Feed H2S, ppmv 1050 1050 852 875 875 780 890 1132 1032 1137 Product H2S, ppmv 68 48 44 29 84 111 120 143 213 162 Product SO2, ppmv 88 45 47 73 25 40 62 65 64 86 Sulfur Yield, % 77.7 83.8 82.3 81.3 77.4 75.4 75.7 77.0 70.4 68.7 GHSV (at 60 F. and 1 atm) 750 750 750 750 750 750 750 750 750 975 below about 6000 F., but the data in Table IV show that vanadium-bismuth catalysts resist such deactivation even when utilized In the presence of 2.5 to 5.0 psia water vapor for a time perlod of greater than 5 months. In a specific embodiment of the Invention par ticularly useful for treating feed gas streams containing between about 5 and 40 volume percent H2S, especially when the feed gas stream contains water vapor at relatively high partial pressures, e.g., above about 2.0 psla and, more usually, above about 4.0 psia, the feed as stream Is blended with alr, preferably In a stoichiometric amount, and the resulting blended gases are passed through an adiabatic reactor containing a particulate vanadium-bismuth catalyst under conditions described hereinbefore such that a substan tlal proportion of the H2S is converted to elemental sulfur vapor. The product gas containing elemental sulfur is passed to a sulfur condenser or other suitable means for separating sulfur from the product gas, leaving a purified product gas containing residual H2S. A portion of the pur ified product gas is then recycled and blended with the feed gas such that the blend of feed gas, air, and recycle gas entering the reactor contalns H2S in a predetermined range, such as 3 to 6 volume percent, or below a predetermined maxlmum, typically and preferably, 5 volume percent. The remaining portion of the purified product gas is treated by any of three methods. The three methods (which are applicable to any embodiment of the invention in which the H2S content of a gas stream recovered after treatment with the vanadium-bismuth catalyst is too high for discharge to the atmosphere) are: (I) If the H25 to S02 volumetric ratlo In the purified product gas stream Is about 2.0, the gas stream may be contacted with any porous refractory oxlde-contalning catalyst, such as alumina, under conditions of elevated temperature, e.g., 4000 to 9000 F., such that a substan tidal proportion of the H2S is converted by Reaction (111) to elemental sulfur, which is then recovered, as by condensation. In this embodiment of the Invention, it is most preferred that a vanadium-bismuth catalyst as described hereinbefore be utilized to carry out the conversion to sulfur such catalysts having far greater activity than typical alumina catalysts and therefore being useful for providing the same conversion of H2S to sulfur as alumina, but under the more difficult conditions of lower operating temperature and/or higher space velocity. (2) If the H2S to SO2 volumetric ratio is sub stantlally above 2.0, or if one desires to allow for fluc tuatlons In the H2S to S02 ratto In the purlfled product gas stream, the purified product gas stream Is blended with sufficient air to provide a volumetric ratio of H2S/ (SO2 + 02) of about 2.0, and the resulting mixed gases are then contacted with a vanadlum-bismuth catalyst under condl- tions herelnbefore disclosed for conversion to elemental sulfur. Alternatively but less preferably, a vanadia catalyst consisting essentially of a vanadium oxide or sul flde on a porous refractory oxide support may be substituted for the vanadium-bismuth catalyst, provided the water vapor of the mixed gases in contact therewith is at a par tidal pressure below about 1.0 psia or the operating temperature is above about 6000 F. Use of the vanadia catalyst provides less activity for the conversion of H2S to sulfur than Is the case with vanadlum-bismuth catalysts, but the lower activity may be suitable in certaln instances, as when cost of the catalyst is of special importance. (3) If the H25 content of either the purified product gas stream or the gas streams recovered after sulfur condensatlon from methods (I) and (2) above Is too high for discharge to the atmosphere, but such gas streams could be discharged to the atmosphere If the H25 were converted to sO2 (due to less astringent air pollution standards for 502 than for H2S), such gas streams are subjected to incinera tlon to convert the H25 therein to SO2. The Incineration may be accomplished thermally at temperatures above about 10000 F. In the presence of excess oxygen, but It Is preferred that the incineration be accomplished catalytically by contact with the vanadium-bismuth catalyst of the Inven tton as described herelnbefore under the range of conditions for conversion to S02 also described hereinbefore. Use of the vanadium-bismuth catalyst provides a distinct advantage over thermal incineration In that the gas stream to be treated does not require as much preheating, the vanadium bismuth catalyst being active for the conversion of H2S to SO2 at temperatures substantlatly below 5000 F. Although the invention has been described in conjunctlon with specific examples and embodiments thereof, It is evident that many alteratlons, modifications, and variations will be apparent to those skilled in the art In light of the foregoing description. For example, It should be self-evident that the catalytic process of the invention may easily be modified to oxidize H2S to any desired percentage combination of sulfur and SO2 by simply controlling the proportion of oxygen between the amount required for Reaction (I) and that required for Reaction (ll). Accordingly, It is intended in the invention to embrace these and all such alternatives, modifications, and variations as may fall wlthin the scope of the appended claims.

Claims: CLAIMS I. A process for oxidizing H25 to elemental sulfur In the gas phase by contact of a gas containing H2S with a solid catalyst in the presence of oxygen or SO2 at a temperature between 2500 and 9000 F., and whereln said catalyst comprises vanadium and bismuth components. 2. A process as defined in ClaIm I, wherein said process is conducted over a time perlod of at least 90 days without said catalyst exhibiting substantially any deactivation for oxidizing H2S to sulfur. 3. A process as defined in Clalm 1 or 2, wherein slid catalyst Is also In contact with one or more components selected from the group consisting of H2, CO, NH3, and light hydrocarbons, but essentially none of said components is oxidized during sald contacting. 4. A process as defined In Claim 1, 2 or 3 wherein oxygen is present during said' contacting In a proportion between about 0.9 and 1.1 times the stoichiometric proportion necessary for conversion of H25 to sulfur. 5. A process as defined In any one of the preceding claims, wherein the catalyst is In particulate form and consists essentially of vanadium and bismuth components on a refractory oxide, said catalyst comprising vanadium and bismuth components selected from the group consisting of the vanadium oxides and sulfides, the bismuth oxides and sulfides, and the bismuth vanadates. 6. A process for treatlng a feed gas stream containing a substantlal proportion of H2S comprising: (I) blending said feed gas stream with alr; (2) contacting the resulting blended gas stream In a reaction zone malntalned at temperatures between about 2500 and 9000 F. with a catalyst comprising catalytically active vanadium and bismuth components, said contacting being such that e substantlal proportion of the H2S In said blended gas stream Is converted to elemental sulfur vapor; (3) recoverlng a product gas stream from step (2) and separating elementa sulfur Therefrom, thereby producing a purified product gas stream; and (4) recycling a portlon of the purified product gas stream to step (i). 7. A process as defined in Clalm 6, wherein sald feed gas stream contalns between about 5 and 40 volume percent H2S and said portion of said purIfIed product gas stream recycled to step (I) Is sufficient to produce an H2S concentration In said blended gas stream at a predetermined value substantially lower than 10 volume percent and lower Than the H2S concentration of said feed gas stream. 8. A process as defined In Claim 7, wherein The initial contactlng in said reaction zone Is below about 3500 and at least some reaction of said H2S with oxygen to produce sulfur takes place below 350 F. 9. The process as defined in Claim 6 or 7, wherein at least some elemental sulfur vapor Is produced at a temperature maintained in said reaction zone between about 2500 and about 6000 F. 10. A process for oxidlzing H2S in the gas phase comprising (1) contacting H2S and free oxygen with a solid catalyst comprising catalytically active vanadium and bismuth components on a carrier materlal In a reaction zone maintained at between about 2500 and about 6000 F., said contacting being such that H2S reacts with free oxygen In said reaction zone to produce elemental sulfur and (2) removing elemental sulfur from said reaction zone. II. A process as defined in Claim 10 whereln said oxygen is supplied in the form of air. 12. A process as defined In Clalm 10 or II, wherein sald catalyst comprlses vanadium oxides or sulfides and bismuth oxides or sulfides on a refractory oxide support. 13. A process as defined In Claim 10, 11 or 12, wherein The initial contacting In said reaction zone is at a temperature below about 3500 F., with at least some of said H2S reacting with said oxygen to produce elemental sulfur at temperatures below 3500 F. 14. A process as defined In Clalm 13, wherein that proportion of said reaction zone which Is at a temper- ature below about 3500 F. contalns water vapor In contact with said catalyst at a water vapor partial pressure above about 2.0 psia with the total pressure betng between about 5 and 300 psla. 15. A process for the oxidation of H2S to elemental sulfur comprising (I) blending a feed gas stream containing H2S with air; (2) passing the resulting blend through a reaction zone containing a solid catalyst consist ing essentially of catalytically active vanadium and bismuth components on a refractory oxide support under conditions such that H2S reacts with the oxygen supplied with said air to produce elemental sulfur vapor, said reaction being Initsated at a temperature between about 2500 and about 4750 F.; and (3) withdrawing a product gas from said reaction zone containing elemental sulfur vapor produced In said reaction zone. 16. A process as defined In Claim 15, whereln the catalyst is In particulate form and contalns vanadium and bismuth components selected from the group consisting of the vanadium oxides and sulfides, the bismuth oxides and sulfides, and the bismuth vanadates. 17. A process as defined In Clalm 15 or 16, whereln said reaction ts initiated at a temperature below about 4000 F. 18. A process as defined In Clalm 15, 16 or 17, whereln the amount of air blended with said feed gas is such that the blend In step (2) oontains oxygen in essentially the stolchlometrlc proportion necessary for the converslon of said H2S to elemental sulfur vapor. 19. A process as defined In Claim 18, whereln said reaction is initiated at a temperature below about 3000 F. 20. A process for treating a feed gas stream containing one or more sulfur components selected from the group conslstlng of SO2, COS, CS2, and light mercaptans comprising: (I) simultaneously converting essentially all of said sulfur components to H25 by contacting said feed gas stream In a first reaction zone maintained at elevated temperatures between about 3000 and 12000 F. with a catalyst comprisIng one or more active catalytic components selected from the group consisting of nickel, cobalt, iron, tungsten, and molybdenum In the presence of hydrogen and water vapor; ; (2) contacting the H2S containing gas stream obtained from step (I) In a second reaction zone maintained at temperatures between about 2500 and 9000 F. and I n the presence of an oxidant gas selected from the group consist ing of oxygen and S02 with a catalyst comprlslng catalytically active vanadium and bismuth components on a refractory oxide support under conditions such that elemental sulfur vapor Is produced by the reaction of said oxidant gas and H2S; and (3) separating elemental sulfur from the gas stream produced In step (2). 21. A process as defined In Claim 20, wherein sald oxidant gas is oxygen supplled in the form of alr, said temperature In step (2) being maintained between about 2500 and 4750 F., and wherein said catalyst In said step (2) consists essentially of vanadium and bismuth components on a refractory oxide support, with at least some of said van radium components being in the form of a vanadium oxide or sulfide and at least some of said bismuth components being in the form of a bismuth oxide or sulfide. 22. A process as defined in Clalms 20 or 21, wherein said contacting In the first reaction zone is at a temperature below about 9000 F. and said catalyst In said step (I) comprises cobalt and molybdenum components. 23. A process for treating a feed gas stream containing H2S comprising: (I) blending said feed gas stream with air; (2) contacting the resulting blended gas stream In a first reaction zone maintained at temperatures between about 2500 and 9000 F. with a catalyst consisting essentially of vanadium and bismuth components on a refractory oxide support, said vanadium components comprising a vanadium oxide or sulfide and said bismuth components comprlsing a bismuth oxide or sulfide, and said contact lng being such that a substantial proportion of the H2S in the blended gas stream is converted to elemental sulfur vapor by reaction with oxygen but some residual H2S re mains; ; (3) recoverlng a first product gas stream from step (2) and separating elemental sulfur therefrom, thereby producing a first purified product gas stream, said purl fled product gas stream containing said residual H2S; (4) contactIng at least some of said purlfled product gas stream with a solid oxidation catalyst comprlstng a porous refractory oxide In a second reaction zone maintained between about 2500 and 9000 F., said contacting being In the presence of sufficient oxygen, or or both such that a substantial proportion of said residual H2S Is converted to elemental sulfur; and (5) recovering a second product gas stream containing elemental sulfur and separating elemental sulfur therefrom, thereby producing a second purl fled product gas stream. 24. A process as defined in Claim 23 wherein said second purified product gas stream contains a small proportion of H2S and wherein said second product gas stream is blended with an excess of air for the conversion of said small proportion of H25 to SO2 and then contacted with a catalyst comprlsing vanadium and bismuth active catalytic components on a porous refractory oxide support In a third reaction zone maintained at temperatures between about 2500 and 9000 F. such that essentially all of said small proportion of H2S is converted to S02. 25. A process defined in Clalm 23 or 24, whereIn said catalyst in said first and second reaction zones consists essentially of more than about 7 weight percent vanadium component calculated as V205, and more than about 8 weight percent bismuth components, calculated as B1203, on a porous refractory oxide support, and wherein air is blended In step (I) and in step (4) such that essentially the stoichiometric amount of oxygen Is avallable In said first reaction zone and essentially the stoichiometric amount of S02 plus 02 is available In said second reaction zone for the conversion of H2S to elemental sulfur in said first and second reaction zones. 26. A process as defined in Claim 23, wherein at least some of said elemental sulfur Is produced at a temperature maintained In said first reaction zone between about 2500 and about 6000 F. 27. A catalyst composition comprising supported vanadium and bismuth components catalytically active for oxidizing H2S In the gas phase, said catalyst comprising about 8 to about 20 weIght percent bismuth components, calculated as Bi2O3, and at least about 7 weight percent vanadium components, calculated as V205. 28. A catalyst composition consisting essentially of vanadium and bismuth components on a support, said catalyst being catalytically active for the oxidation of H2S, said catalyst comprising bismuth components In a proportion between about 8 and 20 weight percent, calculated as B1203, and said vanadium components comprising at least about 5 weight percent of the catalyst composition, calculated as V2O5. 29. A catalyst composition as defined In Claim 27, whereln, when contacted with a gas stream contain- ing water vapor at a partial pressure between about 2.5 and 5.0 psla and having a composition, calculated on an anhydrous basis, comprising 99% C02 and between about 750 and 1200 vppm H2S blended with air supplied at a rate such that oxygen is present In a proportion between about 0.9 and 1.1 times the stoichiometric proportion necessary for the conversion of said H2S to elemental sulfur under the following conditions: 300 psla total operating pressure and a space veloclty of 750 v/v/hr, said catalyst Is catalytically active for lighting off the reaction between said H2S and oxygen to produce sulfur at temperatures below about 3350 F. and said catalyst, under the foregoing conditions , remalns active for at least 90 days. 30. A process for the oxidation of H2S to S 2 In a feed gas stream containing H2S, oxygen in excess of that required for The e conversion of H2S to S02, and water vapor at a partial pressure of at least about 1.5 psla, said process comprising (I) Introducina, over a 90 day time period, said feed gas stream into a reaction zone wherein said feed gas stream contacts, at temperatures between about,2500 and about 6000 F., a catalyst consisting essentially of vanadium and bismuth components on a refractory oxide support, at least some of which vanadium and bismuth components are present in the form of vanadium oxides or sulfides and bismuth oxides or sulfides, respectively, said contacting being such that at. least 90 of said H2S Is converted to S02 by reaction with said oxygen In said reaction zone, said catalyst malntaln ing substantially undiminished activity for reacting H2S to S02 during said 90 day time period, and (2) removlng from said reaction zone a product gas stream containing substantially all the S02 produced In said reaction zone. 31. In a process for catalytically Incinerat ing H2S to SO2 In a reaction zone by reaction with oxygen, the Improvement whereln said incinerating comprises con tactfng In said reaction zone said H2S and said oxygen at between about 2500 and about 6000 F., in the presence of water vapor at a partial pressure of at least about 1.0 psla, with a solid catalyst comprising vanadium and bismuth as essentlal active components. 32. A process as defined In Claim 31, wherein said water vapor Is at a partial pressure above about 4.0 psla. 33. A process for removing H2S from a feed gas stream comprising: (I) contacting said feed gas stream In the presence of oxygen with a solid catalyst comprising vanadium and bismuth active catalytic components In a first reaction zone wherein temperature is maintained between about 2500 and 9000 F. under conditions such that a substantlal proportion of said H2S Is converted to elemental sulfur but a residual proportion of H2S remalns; ; (2) converting essentially all of said residual H2S present In the product gases obtained In step (I) to S02 by contacting said residual H2S In the presence of excess oxygen for the conversion of said residual H25 to S02 In a second reaction zone wherein temperature is maintained between about 2500 and 9000 F. with a solid catalyst consisting essentially of vanadium and bismuth components on a carrier selected from the group consisting of refractory oxides, hydrophobic crystalline silicas, amorphous aluminosilicate zeolftes, crystal line aluminost- locate zeolltes, and mixtures thereof, said contacting convertlng a substantlal proportion of said residual H2S to S02 with out producing essentially any SO3; and (3) recoverlng a product gas stream essentially free of SO3 but containing S02. 34. A process for removlng H2S from a feed gas stream also containing water vapor at a partial pressure greater than about 1.0 psia, which process comprises: (I) contacting said feed gas stream In the presence of oxygen with a solid catalyst comprising vanadium and bismuth active catalytic components In a first reaction zone malntalned between about 2500 and 9000 F. under conditions such that a substantial proportion of said H2S reacts with said oxygen to produce elemental sulfur but a residual proportion of H2S remains. (2) contacting said residual H2S with a catalyst comprising vanadium and bismuth components as essential active components In a second reaction zone whereln temperature is maintained between about 2500 and 6000 F. and wherein oxygen is present and water vapor Is present at a partial pressure of more than about 1.0 psia, said contacting being such that a substantial proportion of said H2S reacts with said oxygen to produce S02; and (3) recovering a S02-contaln1ng product gas stream of reduced H2S content In comparlson to said feed gas stream. 35. A process as defined In Claim 33 or 34, wherein the contacting in step (2) is accomplished at a temperature less than 6000 F. and in the presence of water vapor at a partial pressure of at least 1.5 psla, and wherein temperature is maintained in said first reaction zone between about 2500 and 4500 F. 36. A process as defined In Claim 33, 34 or 35, whereln said oxygen is supplied in steps (I) and (2) in the form of alp and the air supplied In step (I) Is such that essentially the stoichiometric proportion of oxygen necessary for the conversion of said H2S in said feed gas to elemental sulfur Is present, and wherein sa(d catalysts In steps (I) and (2) both comprlse a vanadium oxide or sulfide and a bismuth oxide or sulfide. 37. A process as defined in Clalm 36, wherein elemental hydrogen or ammonia is also present in said feed gas, said elemental hydrogen or ammonia remaining essentially completely unoxidized in steps (I) and (2) and being recovered with said product gas stream. 38. In a process for catalytically Incinerating H2S to S02 in a reaction zone by reaction with oxygen, the improvement wherein said Incinerating comprises contacting In said reaction zone said H2S and oxygen supplied in an amount In excess of that required for the conversion of said H25 to SO2 at a temperature malntalned between about 2500 and 9000 F. with a solid catalyst comprising vanadium and bismuth active catalytic components on a carrier materlal, said vanadium and bismuth components each being present in a proportion above about 5 percent by weight, calculated as V205 and B1203, respectively, under conditions such that at least 90% of said H2S is converted to S02 wlthout the formation of a substantial amount of SO3. 39. In a process for catalytically Inclner acting H2S to S02 In a reaction zone by reaction with oxygen, the Improvement whereln said Incinerating comprises contacting in said reaction zone said H2S and oxygen supplied in excess of that required for the conversion of H2S to SO2 at temperatures maintained between about 250 and 9000 F. with a solid catalyst consisting essentially of vanadium and bismuth catalytically active components on a carrier material under conditions such that a sub stantlal proportion of said H2S Is converted to S02 with- out the formatlon of essentially any SO3. 40. A process as defined In claim 38 or 39, whereln said oxygen Is supplied In the form of air and Is supplied In substantlal excess of that required for the conversion of said H25 to SO2. 41. A process as defined in Claim 38, 39 or 40, whereln water vapor is present durlng said contacting at a partial pressure above about 4.0 psia.

Inventors: HASS, ROBERT HENRY, WARD, JOHN WILLIAM
Applicants: UNION OIL COMPANY OF CALIFORNIA
Application year: 1982
Main classification: C01B17
IPC codes: C01B17