JPH04219306A - Oxidation of hydrogen sulfide - Google Patents

Abstract

PURPOSE: To oxidize H₂S into SO₂ without oxidizing H₂, CO, NH₃ and CH₄ in a gas.

CONSTITUTION: The gas containing H₂S and oxygen is contacted with a solid medium, which contains bismuth and vanadium as effective contact main components, within a reaction zone, where steam exists, with divided pressure of about 0.07 kg/cm² (about 1.0 psia) at contact temperatures of about 121 to about 816°C (about 250 to about 600°F) maintained in the reaction zone and, concerning the contact in the reaction zone, almost all the H₂S reacts with oxygen to creat SO₂. Almost all SO₂ created in the reaction zone is removed from the reaction zone. H₂S in the exhausted gas is oxidized and pollution can be prevented.

COPYRIGHT: (C)1992,JPO

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention relates to a method for oxidizing H2S, in particular to oxidizing H2S in the presence of a significant amount of water vapor.
It relates to a method of catalytic oxidation to O2.

0002

BACKGROUND OF THE INVENTION Current air pollution regulations are extremely restrictive as to the amount of H2S that can be released into the atmosphere. In some cases, the gas flow is about 10 ppmV or more of H2S.
, the gas stream cannot be released to the atmosphere. Accordingly, many methods have been developed to remove H2S from gas streams prior to release to the atmosphere.

One method known in the art for removing H2S is catalytic oxidation, in which a gas stream containing H2S is mixed with air or free oxygen, and the resulting mixture is then mixed with H2S and optionally elemental sulfur. Steam or SO2
Alternatively, it may be passed through a bed of particulate catalyst under suitable conditions to convert to both. One catalyst useful for the gas phase conversion of H2S to sulfur or SO2 is disclosed in U.S. Pat. No. 4,099.
No. 2,404. The catalyst consists of one or more vanadium oxides or vanadium sulfides supported on a refractory oxide such as alumina or silica-alumina. Another such catalyst is disclosed in U.S. Pat. No. 4,012,486, which describes the catalytic combustion of H2S to SO2 using a catalyst having an active component of bismuth. do.

By comparison, the bismuth catalyst of US Pat. No. 4,012,486 is generally found to be less active than the vanadia catalyst of US Pat. No. 4,092,404 for the oxidation of H2S to SO2. . On the other hand, about 0.07
removing H2S from a gas stream, such as off-gas discharged from a geothermal power plant, containing water vapor at a water vapor partial pressure of kg/cm2 (approximately 1.0 psia), typically at least 0.28 kg/cm2 (4.0 psia). In this case, bismuth catalysts are more stable than vanadia catalysts at operating temperatures below about 316°C (600°F). in general,
Vanadia catalyst is about 0.07kg/cm2 (about 1.0
psia) or approximately 316 °C (approximately 600
It has satisfactory stability in the presence of water vapor at operating temperatures above 316 °C (600 °F).
The following temperature and approximately 0.07 kg/cm2 (approximately 1.0
psia) or more, especially 0.105 kg/cm2 (
Conditions in combination with water vapor partial pressures of 1.5 psia) or higher rapidly deactivate the vanadia catalyst. The reason for this deactivation is believed to be due to a complex series of chemical reactions in which the vanadium oxide or vanadium sulfide active catalyst components are converted to less active forms of vanadium, such as vanadyl sulfate (VOSO4).

As mentioned above, vanadia catalysts are extremely active for the oxidation of H2S and are described in US patent application Ser. As disclosed,
Such catalysts have proven extremely useful for oxidizing H2S to sulfur by reaction with either oxygen or SO2. Approximately 0.07kg/cm2 (approximately 1
．． In the presence of water vapor below 0 psia, the vanadia catalyst is extremely stable and can convert H2S to sulfur for more than a year with only slight deactivation.

[0006]

However, despite the excellent properties of vanadia catalysts, the purpose of the present invention is not only to improve the stability of vanadium-containing catalysts in the presence of water vapor, but also to convert H2S to SO2. The objective is to significantly improve the conversion activity. More particularly in relation to water vapor,
The object of the present invention is about 0.07 kg/cm2 (about 1.0
psia) or more, particularly about 0.105 kg/cm2 (about 1.5 psia) or more, more particularly about 0.14 kg/cm
The present invention provides a method for catalytically oxidizing H2S in the presence of water vapor at a partial pressure greater than about 2.0 psia. It is also an object of the present invention to achieve said method without oxidizing components such as H2, CO, NH3 and CH4 that may be present during the oxidation of H2S.

[0007]

[Means for Solving the Problems] It has been confirmed that a catalyst containing bismuth and vanadium components is highly active and stable for gas phase oxidation of hydrogen sulfide, especially in the presence of water vapor. Such catalysts have the high activity of vanadia catalysts and the stability of bismuth catalysts. Furthermore, it has been found that the catalysts of the present invention are generally significantly more stable in the presence of water vapor than catalysts containing bismuth or vanadium alone, particularly at operating temperatures below about 316°C (600°F).

[0008] The catalyst used in the present invention weighs about 0.07 kg/
It is useful when H2S must be oxidized in the gas phase in the presence of water vapor at partial pressures greater than about 1.0 psia. Since an equal volume of water vapor is produced for each volume of H2S that is converted from H2S to sulfur or SO2, the water vapor partial pressure of the feed gas is initially about 0.07
kg/cm2 (approximately 1.0 psia) or less, but
0.07kg/cm2 (1.0p
The present invention is useful for processes that increase in number over sia).

An advantage of the present invention is the high selectivity of the catalyst. Components selected from the group consisting of H2, CO, NH3 and saturated hydrocarbon gases having up to 6 carbon atoms (ie, light hydrocarbons) are not oxidized in the process of the present invention. Additionally, the oxidation of H2S is approximately 482 °C (approximately 9
When carried out at temperatures below 00°F), very little SO3 is produced.

[0010] Furthermore, and quite remarkable, it has been discovered that vanadium-bismuth catalysts are more active than comparable vanadia catalysts for converting H2S to sulfur. This finding was surprising since the vanadia catalyst itself is highly active for converting H2S to sulfur. However, comparable vanadium-bismuth catalysts were found to have not just greater activity, but significantly greater activity than vanadia catalysts. For example, as shown in Example VI below, a prior art vanadia catalyst based on about 10% by weight vanadium pentoxide supported on silica alumina has a
Active to initiate the reaction between H2S and oxygen to produce sulfur at a temperature of 91 °C (approximately 375 °F) but with the same carrier but with a vanadium component of 8.7% by weight and 12.9% by weight Vanadium-bismuth catalysts containing % bismuth components are found to be active to initiate the reaction to convert H2S to sulfur at temperatures below 300 DEG F. (149 DEG C.).

[0011] Here, the catalyst containing vanadium and bismuth or the catalyst containing vanadium and bismuth components is (1)
Vanadium element and bismuth element, (2) vanadium element and one or more bismuth compounds, (3) bismuth element and one or more vanadium compounds, (4
) one or more vanadium compounds and one or more bismuth compounds, (5) one or more bismuth and a vanadium compound (e.g. bismuth vanadate), or (6) any of the above. H containing the combination of
Includes catalysts effective for oxidizing 2S.

The active catalyst used in the present invention contains vanadium and bismuth as essential active components. The essential active ingredients are present as elements V and Bi or as mixtures of individual vanadium and bismuth compounds (e.g. V2S
Bi2S3 mixed with 5) or compounds of bismuth and vanadium, such as Bi(VO3)3 or BiVO4
may exist as Alternatively, the catalyst includes any combination of the elements and compounds of vanadium and bismuth as essential active ingredients. Preferred catalysts include at least one vanadium oxide or vanadium sulfide (e.g. V2O5, V2O3, V
2S5, and V2S3), and at least one bismuth oxide or bismuth sulfide (e.g., BiO, B
i2O3, Bi2O5, Bi2S3 and Bi2O
4). The most preferred catalyst is at least some bismuth vanadate (i.e., as orthovanadate,
BiVO4 or Bi2O3V2O5, metavanadate Bi(VO3)3, or pyrovanadate Bi
4(V2O7)3).

Typical catalysts contain vanadium and bismuth components in an intimate mixture, and although the catalyst can consist primarily of such a mixture, the vanadium and bismuth components are mixed with a carrier material, such as by impregnation or kneading. It is highly preferable to do so. Usually the carrier (or support) material is a preferred refractory material such as alumina-silica, zirconia, titania, magnesia, silica-alumina, silica-zirconia, silica-titania, silica-magnesia, silica-zirconia-titania and combinations thereof. It consists of a porous refractory oxide containing a polyhydric oxide. Suitable refractory oxides include acidic metal phosphates and arsenates such as aluminum phosphate, boron phosphate, aluminum arsenate, chromium phosphate, and the like. Other suitable supports include hydrophobic crystalline silica, such as U.S. Pat.
No. 1,724 (as used herein, about 0.5 c
A refractory oxide is hydrophobic if it can absorb less than c/g of water). Also suitable are natural or synthetic amorphous and crystalline aluminosilicate zeolites. The most useful crystalline aluminosilicate zeolites are ion-exchange treated to remove nearly all ion-exchangeable alkali or alkaline earth components. Particularly useful are hydrophobic crystalline alumino-silicates containing almost no alkali or alkaline earth components. Examples of such zeolites include the ZSM-5 zeolite disclosed in U.S. Pat. No. 3,702,886 and the ZS zeolite disclosed in U.S. Pat. No. 3,709,979.
M-11 Zeolite and U.S. Patent No. 4,019,88
There is a hydrophobic zeolite disclosed in No. 0 specification. This type of zeolite is characterized by a high silica to alumina ratio.

The most preferred refractory oxide support contains at least 10% by weight alumina, preferably about 20-30% by weight alumina.
silica-alumina when present in weight percent proportions. Catalysts prepared from this type of support typically have greater activity for oxidizing H2S than catalysts prepared from most other refractory oxides. Furthermore, such carriers are highly resistant to sulfation, i.e. SO3 and/or SO3
In the presence of 2 and O2, such supports are less susceptible to the formation of aluminum sulfate and the resulting loss of surface area, crushing force and activity. In general, catalysts prepared using silica-alumina supports containing at least 10% by weight alumina are expected to experience little if any deactivation due to sulfation under the processing conditions described below.

Several methods are known in the art for combining vanadium and bismuth components with refractory oxide supports. One such method is impregnation. That is, 75% SiO2-
Ammonium vanadate (
or other soluble vanadium compounds) solution;
Dry at high temperatures (usually around 110 °C (230 °F)
It is then contacted with a bismuth salt solution, for example an acidic solution of bismuth nitrate or bismuth chloride. The composite can also be prepared by any of a variety of kneading techniques. A typical method is to knead silica alumina with solid ammonium metavanadate, solid bismuth nitrate, and sufficient water to create a paste suitable for extrusion through a mold. More preferably, one or both of the vanadium and bismuth salts can be added to the kneaded material in the form of a solution. In a preferred embodiment, a silica-alumina mixture, a dilute nitric acid solution of bismuth nitrate, and an aqueous solution of ammonium metavanadate are kneaded. Alternatively, the silica-alumina or other refractory oxide is kneaded with, for example, an ammonium metavanadate solution, then dried or calcined at high temperature, and then kneaded with an aqueous solution of a bismuth salt, such as bismuth nitrate in dilute nitric acid. Further, kneading can be performed by mixing silica-alumina and one or more types of bismuth vanadate in the presence of water. Furthermore,
Composites can be prepared by a combination of impregnation and kneading techniques, such as impregnating silica-alumina with ammonium vanadate, calcination, and then kneading with an acidic solution of bismuth nitrate or bismuth chloride.

[0016] After the composite is prepared by any of the impregnation and/or kneading methods described above or a method equivalent thereto, it is usually heated at a temperature of about 371° to about 871°C (about 700°C).
482° to about 1600°F), preferably 482° to 64°
Calcinate at a temperature of 900° to 1200°F. Calcination produces a catalyst containing vanadium and bismuth mostly in oxide form, usually at temperatures between 371° and 871°C (
Calcination (700 DEG -1600 DEG F.) produces sufficient bismuth vanadate, usually in the form of monoclinic bismuth orthovanadate (BiVO4), to be detected by X-ray diffraction analysis. Bismuth orthovanadate and other bismuth vanadates are commonly formed even when impregnating or kneading without careful addition of bismuth vanadate. For example, silica-alumina is kneaded with ammonium metavanadate (Example I), then further kneaded with an acidic solution of bismuth nitrate, extruded, cut into particles, and 482°
When calcined to 900° to 1000° F., the final product contains enough bismuth orthovanadate to be detected by X-ray diffraction analysis.

[0017] The present invention is not limited to the fact that catalysts containing bismuth vanadate are more active and stable than catalysts that do not contain bismuth vanadate. This applies in particular to bismuth orthovanadate (BiVO4). Further, the reason why the stability of the catalyst is higher in the presence of water vapor than in the case of a catalyst containing only a vanadium component or only a bismuth component is considered to be due to the presence of bismuth vanadate. Catalysts containing bismuth vanadate, especially bismuth orthovanadate, are therefore preferred in the present invention.

[0018] The finished catalyst has at least 5.0
Contains wt.% vanadium and 5.0 wt.% bismuth. Catalysts containing less than 5.0% by weight of either metal are more active or stable than catalysts containing only either vanadium or bismuth components, but more active or stable than catalysts containing at least 5.0% by weight of each component. Somewhat less activity and stability. The catalyst preferably contains 5 to 15% of each component, and can contain up to 40% by weight of each component as required. A highly preferred catalyst is about 7 as V2O5.
~15 wt.% vanadium and about 8-20 wt.% bismuth as Bi2O3, with the most preferred catalyst comprising at least 8.0 wt.% vanadium component as V2O5 and at least 10 wt.% bismuth component as Bi2O3. All calculations regarding the proportions of active metal components are V2O5 and Bi2O3, respectively.
The weight percentages of vanadium and bismuth were recorded as . Therefore, the element vanadium, with a weight of 0.1 g each,
Catalyst particles weighing 5 g containing the element bismuth, bismuth sulfide (Bi2S3), vanadium sulfide (V2S5), and bismuth orthovanadate (BiVO4) are
Contains a vanadium component in a proportion of 5.52% by weight as V2O5, and a bismuth component in a proportion of 5.48% by weight as Bi2O3).

[0019]

EXAMPLES The following two examples illustrate preferred methods of preparing catalysts useful in the present invention.

EXAMPLE I 75% SiO, commercially available from Davison Chemical Division of W. R. Grace and Company, as a high alumina cracking catalyst.
421 g of 2-25% Al2O3 silica-alumina was placed in a Steel Muller and to this was added 44.2 g of ammonium metavanadate (NH4VO3) and 6 g of powdered methyl cellulose. The mixture was kneaded for 45 minutes. Next, a solution was prepared by dissolving 88.8 g of bismuth nitrate (Bi(NO3)35H2O) in a liquid consisting of 200 cc of water and 32 cc of concentrated nitric acid. Add this solution to the previously kneaded mixture,
Kneading continued for 15 minutes. It was then mixed with 71 cc of water for 15 minutes to produce an extrudable paste. The resulting paste was then extruded through a 3.2 mm (1/8 inch) diameter die to form approximately 3.2 to 12.7 mm.
(approximately 1/8 to 1/2 inch) long particles. The extrudates were dried overnight at a temperature of 110°C (230°F). It was then calcined in air at a temperature of 500°C (932°F) for 2 hours. The catalyst obtained contained 9.1% by weight of vanadium component as V2O5 and Bi2O3.
It contained 11.2% by weight of bismuth component. The catalyst contained X-ray detectable amounts of bismuth orthovanadate.

Example II Sufficient amount of ammonium metavanadate (NH4VO
3) was mixed with the high alumina silica-alumina described in the previous example. After extrusion 3.2 mm (1/8 inch) diameter, 1.6 ~ 12.7 mm (1/16 ~ 1/2 inch) diameter
2 inch) cylindrical extrudates and calcined in air for 2 hours at a temperature of about 500°C (932°F). The product obtained contained a vanadium content of 10% by weight as V2O5. 35g of bismuth nitrate (Bi(N)
O3)3.5H2O) with 100cc of water and 15cc
Dissolved in a mixture of concentrated nitric acid and added water to make 120
The cc solution was contacted with 100 g of the above product. The solution was left in contact with the extrudate for 2 hours to ensure complete impregnation. The extrudates were then filtered and heated to 110°C (230°C).
(°F) overnight and calcined at 500°C (932°F) for 2 hours in the presence of air. The resulting catalyst contained an amount of bismuth orthovanadate detectable by X-rays, and further contained a vanadium component of 8.63% by weight as V2O5 and a bismuth component of 11.6% by weight as Bi2O3.

Catalysts prepared by the above-mentioned methods or methods clearly corresponding thereto can be prepared by converting H2S to optionally SO2
It was found to be highly active against gas phase oxidation to oxidize to , sulfur, or a combination of both. Furthermore, such a catalyst is 121
Over a temperature range of 250° to 900°F (° to 482°C), it produces little SO3 and H2
, selectively oxidizes H2S without oxidizing lower hydrocarbons that may coexist with CO, NH3 or H2S. Of particular importance is that the catalyst is extremely stable in the presence of water vapor. Approximately 0.07kg/cm2 (approximately 1
．． Water vapor is present at a partial pressure greater than or equal to 0 psia).
Catalysts that oxidize H2S at temperatures below 16°C (about 600°F) have a lifetime of at least 90 days, and usually at least one year. In particular, the catalyst has at least 0.105
kg/cm2 (1.5 psia), preferably at least 0.28 kg/cm2 (4.0 psia)
In particular, at a water vapor partial pressure of about 0.7 kg/cm2 (1
It is effective in oxidizing H2S at water vapor partial pressures up to 0.0 psia). For effective results, for example, a temperature of about 193 °C (380 °F) in the presence of water vapor at a partial pressure of about 0.63 kg/cm2 (about 9.0 psia).
H2S is converted to elemental sulfur by reacting with oxygen at a temperature of .

The choice of whether to convert H2S in a given gas stream to elemental sulfur or SO2 depends in large part on local air pollution regulations. Typically, the maximum concentration of H2S that can be emitted into the atmosphere is about 10 ppmV
However, SO2 is about 500 ppmV~2.0
It can be discharged at maximum concentrations varying in % by volume. Therefore, the combustion of H2S, that is, the SO2 of H2S
The conversion to is typically about 10 ppmV to 2.0% by volume.
Typical gas streams treated for conversion to elemental sulfur contain at least about 500 ppmV of H2S, typically 500 ppm
V ~ 10.0% by volume H2S, preferably 50 pp
mV ~5.0% by volume H2S, optimally 500
Contains ppmV~2.0% by volume H2S.

That is, the gas stream treated in the method of the invention is
In addition to H2S, N2, CO2, CO, H2,
Contains any of the components such as SO2, O2, Ar, NH3, H2O and lower hydrocarbons. Typical gas streams processed here are sour natural gas, geothermal steam offgas, and H2S-containing gas streams such as hot-gasified coal or gasified residues. The gas stream may also contain sulfur-containing components, such as COS, CS2, and light mercaptans (ie, saturated mercaptans containing 6 or fewer carbon atoms). If such sulfur-containing components are present, it is preferred to pretreat the gas stream by the method disclosed in U.S. Pat. No. 3,752,877. According to this method, CS2, COS and light mercaptans are
together with O2 at high temperatures (typically 149 ° to 538 °C (3
Co, Mo, Fe at 00° to 900°F)
, W, Ni, preferably a combination of Co and Mo or Ni and Mo, and simultaneously converted to H2S by reacting with H2 and/or water vapor. do. This pretreated gas stream contains H2S as almost the only gaseous sulfur component;
H2S can be treated by the method to convert it to the desired SO2 and/or elemental sulfur.

A particularly suitable gas stream for the pretreatment method is Claustail gas. Other gas streams which are preferably pretreated before contacting with the catalyst used in the present invention are gas streams containing olefins or aromatic hydrocarbons. The olefin deactivates the catalyst by forming a gum that precipitates on the catalyst surface.
Aromatics such as benzene can be present in significant amounts (e.g. 100
ppmV), the operating temperature is approximately 177 °C (
The catalyst is deactivated when the temperature is below about 350°F. However, these two types of deactivation are only temporary, with olefin deactivation being overcome by high temperature oxidation of the gum-containing catalyst and aromatic deactivation at 177 °C (350 °F).
This can be overcome by increasing the operating temperature above this point. Also,
Preferably, the gas stream containing aromatic or olefinic components is preheated before contacting with the catalyst of the invention in order to remove these harmful components. One pretreatment method particularly suitable for gas streams containing olefins is SO2, CS2,
Catalytic hydrogenation with the catalyst and conditions specified for the gas stream containing COS and light mercaptans.

The gas stream to be combusted is processed according to the following reaction equation (1
) 2H2S + 3O2 → 2SO2 +2
It should contain enough oxygen or be admixed with enough oxygen or air to provide at least the stoichiometric amount required for the reaction expressed as H2O. Additionally, it is preferred that oxygen be present in excess of the stoichiometric amount, typically about 1.1 to 2.5 times the stoichiometric amount. Other conditions typically used to combust H2S in an adiabatic or isothermal reactor are: (a) 0.35-35.15 kg/cm2;
(5-500 psia), preferably 1.05-5
．． 27 kg/cm2 (15-75 psia) operating pressure, (b) 121°-538°C (250°-9
00 °F), preferably about 316 °C (600 °F
), particularly preferably about 232°C (450°F)
Inlet operating temperature below, (c) 100 ~ 50,0
00v/v/hr, preferably 500 to 5000v/hr
Space velocity in v/hr. The operating conditions are suitably adjusted to convert at least 90% of the H2S to SO2. Preferably, operating conditions are adjusted to convert substantially all of the H2S. The conditions for converting almost all H2S to SO2 are 232 °C (450 °F) and 3.5 kg/cm2.
(50 psia), 2000v/v/hr (16
(gas volume calculated at 60°F), 2.2 stoichiometric air and 2700 ppmV H in the feed gas.
It is 2S. The following Example III shows that these conditions are appropriate.

EXAMPLE III A feed gas stream of the composition shown in Table 1 was fed at a rate of 460 scc/min (1
The mixture was mixed at a rate of 6° C. (gas volume measured at 60° F.). Water vapor content 7.7% by volume and oxygen content approx. 0.
The resulting gas mixture containing 80% by volume (2.23 times the stoichiometric amount) was heated at 3.5 kg/cm2 for 15 days.
(50 psia) pressure, 232 °C (450 °
11.6% by weight of bismuth component (as Bi2O3) and 8.6% by weight of vanadium component (as V2O5) at a constant temperature of F) and a space velocity of about 2000 v/v/hr.
15 cc of catalyst particles consisting of 150 ml of catalytic catalytic converter (as 100 ml). The catalyst was prepared as described in Example II, and the water pressure in the reactor was 3.5 kg/cm2 (50 ps
ia). The product gas was analyzed on day 15 by a suitable mass spectrometry technique and the results are shown in Table 1 on an anhydrous basis. As shown in Table 1, H2S is completely converted into SO2
H2 or methane is not oxidized. The SO3 content of the effluent gas was 3-5.0 ppm.

[0028]
Table 1
Feed composition Product composition

──────── ────────
hydrogen
873 ppmV
838 ppmV methane
1.68 vo
l. % 1.60 vol. %
nitrogen
0 ppmV
2.77 vol. % oxygen

0 ppmV 0.43v
ol. % Argon
3ppmV
365 ppmV carbon dioxide 97.96
vol. % 94.85 vol
．． % 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 0pp
Total sulfur compounds as mV SO2
2759 ppmV
2212 ppm V1: The product has lower total sulfur compounds than the feed due to the mixing of air oxidants and the fact that the H2S concentration in the feed on day 15 of operation is slightly lower than shown in Table 1. be.

Example IV The six catalysts prepared were tested under the conditions of Example III.
H2S was burned at a water vapor pressure of 3.5 kg/cm2 (50 psia) to measure its activity and stability. Six catalysts were prepared as follows.

10% by weight V2 supported on silica alumina
A mixture of the high alumina cracking catalyst and ammonium vanadate described in O5 Example I was kneaded with sufficient water to form a paste suitable for extrusion. This paste was extruded into a 3.2 mm (1/8 inch) die, cut into approximately 1.6 to 12.7 mm (1/16 to 1/2 inch) lengths, and heated to 110 °C (230 °F). and calcined in air at 500°C (932°F) for 2 hours. The catalyst contained 10% by weight vanadium component (V2
(calculated as O5) and silica-alumina (75% silica-25% alumina).

36.6 wt% V2O5 on Silica-Alumina 291 g of high alumina silica-alumina, 108 g of ammonium metavanadate, and 7.74 g of methylcellulose as described in Example I were mixed with a sufficient amount of water. A paste that can be kneaded and extruded was created. The paste was then extruded into 3.2 mm (1/8 inch) diameter, 1
．． 6 ~ 12.7mm (1/16 ~ 1/2 inch)
Cut into cylindrical pieces of length. Leave this in the air for 2 hours.
Calcined at 10°C (230°F). The catalyst thus produced was silica-alumina (75% SiO2-2
It contained 36.6% by weight vanadium content (calculated as V2O5) on 5% Al2O3).

10.2% by weight Bi2 supported on alumina
O3 This catalyst was prepared in a manner similar to that described in Example I of US Pat. No. 4,012,486. The method used is as follows. 17g BiC
13 was dissolved in 40 cc of water and 40 cc of concentrated hydrochloric acid was added. The solution was then diluted with 100 cc of water. The solution thus obtained was contacted with 100 g of gamma alumina 1/16 inch diameter extrudate for 2 hours. Decant and remove excess solution;
Washed until free of chloride with a solution of 30% concentrated NH4OH and 70% water. then 500
cc of water and heated to 500 °C (932 °F) for 2 hours.
). The catalyst is 10 supported on gamma alumina.
．． It contained 2% bismuth component (calculated as Bi2O3).

4.5% by weight supported on silica alumina
Bi2O3 -9.4 wt% V2O5 This catalyst was obtained by first preparing 10 wt% V2O5 supported on silica-alumina as described above. First, 100 g of this catalyst was mixed with 100 g of 100 g of this catalyst to which 5 cc of concentrated nitric acid was added.
The sample was contacted with a solution prepared by dissolving 11.6 g of bismuth nitrate in cc of water and adding enough water to bring the solution to 120 cc. Contact time was 2 hours after which excess liquid was decanted off. The impregnated extrudates were then dried at 110°C (230°F) overnight and calcined at 500°C (932°F) for 2 hours in air. The final catalyst contained 4.5% by weight of bismuth component (Bi2O3
) and 9.4% by weight vanadium content (V
(calculated as 2O5). The final catalyst was determined to contain bismuth orthovanadate by X-ray diffraction analysis.

7.95% by weight supported on silica alumina
Bi2O3 -9.0 wt% V2O5 This catalyst was prepared using the above 4.5 wt% Bi2O3 -9.4 wt% V2O3, except that the impregnation solution was prepared as follows.
Prepared in the same manner as the 2O5 catalyst. 23.2 g of bismuth nitrate was dissolved in 100 cc of water to which 10 cc of nitric acid had been added. The solution was then sufficiently diluted with water to bring the total volume to 12
It was set to 0cc. The final catalyst contained 7.95% by weight bismuth component (as Bi2O3) and 9.0% by weight vanadium component (as V2O5). The catalyst contained bismuth orthovanadate by X-ray diffraction analysis.

11.6% by weight supported on silica alumina
Bi2O3 - 8.63% by weight V2O5 This catalyst was prepared by the method shown in Example II.

H2S was combusted to SO2 using each of the catalysts described above under the conditions listed in Example III. The only condition that varied for each catalyst was the operating temperature. Approximately 232
After operating with various catalysts for several days at varying temperatures in the range of 450° to 510°F, the concentration of unreacted H2S in the gas sample produced at a particular operating temperature at the beginning of the experiment and The stability of each catalyst was determined by comparing the concentration of unreacted H2S in a gas sample produced at the same specific temperature later in the experiment. The data thus obtained are summarized in Table 2. The stability of various catalysts with respect to the increase in unreacted H2S in the product gas per day is also summarized in Table 2. The most stable catalysts consist of bismuth components or bismuth and vanadium components as the main active catalyst components. Catalysts containing only a vanadium component as the major active catalyst component deactivated at an unacceptably high rate. The most stable catalysts are at least about 8.0
% bismuth and at least 7.0% vanadium. This type of catalyst is 10% or 36.6
% V2O5 catalyst and 10% B
It was found to be twice as stable as the i2O3 catalyst.

Two catalysts containing at least about 8.0% by weight bismuth component and at least about 7.0% by weight vanadium component reduce the H2S concentration in the product to 4.0% by weight.
about 3.5 ppmV compared to about 6 ppmV for a vanadium-bismuth catalyst containing only 5 wt% bismuth.
The fact that it remains below pmV is important. H2S emitted into the atmosphere due to many environmental controls is 10 ppmV
Two vanadium-bismuth catalysts containing at least about 8.0 wt% bismuth provide activity and stability such that H2S in the product gas reaches high levels; .5 wt% bismuth - 9.4
It turns out that wt% vanadium catalysts are not suitable for this purpose. In particular, the stability of the 11.6% bismuth-8.63% vanadium catalyst is high. Due to the high stability and high activity of this catalyst, this catalyst and other catalysts containing at least 10% by weight bismuth component calculated as Bi2O3 and at least 8.0% by weight vanadium component calculated as V2O5 is most preferred in the present invention.

[0038]
Table 2
Time t1 Time t2
Live at Live at
In the composition In the composition
Deactivation rate
H2S of H2S of
S Operating temperature t2-t1 p
pmV
ppmV of ppmV °F
Number of days H2S/day────────────
──── ─── ──────── ─────
---10% V2O5 (comparative example) 1.
5 46.8 260 (500)
7.5 6.04 36.6%V2O5
(Comparative example) 1.5 51.5
~232 (~450) 16.9 2.
96 10.2%Bi2O3 (comparative example) 3
．． 3 12.2 266 (510)
14.1 0.63 4.5 %Bi2
O3 -9.4 %V2O5 2.9 6.
0 232 (450) 9.9
0.31 7.95%Bi2O3 -9.0
%V2O5 1.4 3.5 23
2 (450) 6.0 0.35
11.6%Bi2O3 -8.63%V2O5
0.3 3.0 232 (450)
11.0 0.23 ────────
──────────────────────────
─── 1. Deactivation rate = (H2 in the product at t2
ppm of H2S in the product at V - ppm of H2S in the product at t1
V) ÷ (t2-t1) number of days

EXAMPLE V Comparing the initial activity of the catalyst used in the present invention with the prior art, the H2S produced was compared at various temperatures in the experiment of Example IV prior to critical catalyst deactivation. The data are summarized in Table 3. The data summarized in Table 3 are from Example I
II, but with 13.0 wt% Bi2O3 and silica-alumina (75% SiO2).
-25% Al2O3) was used. The catalyst was obtained by impregnating a silica-alumina extrudate with a bismuth nitrate solution and then calcining it in air at 500°C (932°F) for 2 hours.

[0040]
Table 3
Temperature, °C (°
F) ppmV H2S ────
───────── ────────────
────────10%V2O5 (comparative example)
230 (445)
4.4

254 (490)
3.4
26
0 (500) 1
．． 5 36.6%V2O5 (comparative example)
204 (400)
25
210
(410) 17

216 (420)
4.8

227 (440)
1.5 10.2%Bi2O3 (comparative example)
260 (500)
50

266 (510) 11
．． 8-13.4
271 (52
0) 3.3-8.6

277 (530)
3.6 13.0%Bi2O3
(Comparative example) 254 (
490) 17.1

260 (500)
1.0

266 (510)
0.9 4.5%Bi2O3 -9.4%V
2O5 227~232 (440~45
0) 1.7-6.0 7.95%Bi
2O3 -9.0%V2O5 232~
238 (450~460) 1.1~
3.5 11.6%Bi2O3 -8.63%V2O5
232-243 (450-470)
0.3～4.5 ──────────
──────────────────────────

As shown in Table 3, vanadia and vanadium-bismuth catalysts have a temperature of 216° to 232°C (420°C).
Activities were compared under experimental conditions with little unreacted H2S at temperatures ranging from 450 °F to 450 °F. On the other hand, 10.2% and 1
3.0% bismuth catalyst at approximately 260 °C (500 °F)
It was effective only at temperatures above. 254°～260
At temperatures between 490° and 500°F, both bismuth catalysts produce unreacted H2S as high as 50 ppmV.
showed no activity. Therefore, vanadia and vanadium-bismuth-containing catalysts contain substantially H2S
It has been shown that the activity is superior to catalysts containing only bismuth components as the main active catalyst component in converting SO2 to SO2.

The catalyst used in the present invention can also be used to oxidize H2S to elemental sulfur and burn it to SO2. Conditions for producing elemental sulfur are selected from the following ranges, usually for an adiabatic or isothermal reactor: 121
°~482 °C (250 °~900 °F), 10~
10,000 v/v/hr, 0.35-5.27kg
/cm2 (5-75 psia), preferably 13
5° to 246°C (275° to 475°F), 2
00 to 2500v/v/hr and 1.05 to 2.1
1 kg/cm2 (15-30 psia), optimally 135-218°C (275°-425°F)
, 500 ~ 1500v/v/hr, and 1.05~
1.41 kg/cm2 (15-20 psia). Additionally, it is preferable to maintain the inlet temperature below about 204°C (400°F), optimally 177°C (300°F).
50° F.) to convert at least some H2S to elemental sulfur below that temperature. An oxidant gas is also required, in which oxygen, usually supplied in air, is mixed with the feed gas stream to form the formula (2) 2H2S + O2
→ Sulfur vapor is produced by the reaction represented by 2S + 2H2O. The amount of air or oxygen mixed with the feed gas is most preferably such that oxygen is present in a stoichiometric amount or a near stoichiometric amount for reaction equation (2), and usually a stoichiometric amount of oxygen is present. It is about 0.9 to 1.1 times. As is well known, maximum conversion of H2S to sulfur is possible when oxygen is available in stoichiometric amounts. High yields of sulfur are provided by low water vapor pressure and temperatures below about 246 °C (475 °F), especially about 232 °C.
(450° F.) and sulfur yield increases with decreasing temperature and decreasing water vapor partial pressure.

Of course, to convert H2S to sulfur, SO
2 can be used in place of oxygen, and sulfur is produced by the following reaction equation. (3) 2H2S + SO2 → 3S +
2H2O Therefore, if SO2 is present in the feed gas stream where the H2S to SO2 ratio is greater than 2.0, the reaction equation (
3) Add the required amount of oxygen in an amount sufficient to react with the H2S not converted by step. That is, H2S
When the ratio of H2S to SO2 is greater than 2.0, the stoichiometric amount of oxygen is equal to 2.0 H2S to (SO2 +
O2) in an amount sufficient to provide a molar or volumetric ratio of

[0044] When the H2S to SO2 ratio is 2.0 or less, H2S
For a feed gas stream naturally containing 2S and SO2,
In order to achieve high conversion to sulfur, first U.S. Patent No. 3,752
, No. 877, SO2 is converted into H2
Pretreating the feed gas to convert it to S and then
Pretreated gas equal to 2.0 H2S vs. SO2
Mix with sufficient oxygen or air to give the ratio. 2
．． For feed gas containing an H2S to O2 ratio equal to 0, no pretreatment or oxygen addition is required. A catalyst can be used to convert H2S directly to sulfur according to reaction equation (3).

In view of the foregoing, SO2 can be used as the oxidizing agent in place of oxygen if elemental sulfur is desired. That is, mixing either SO2 or an oxygen oxidizer with a gas stream containing H2S, here giving an H2S to oxide ratio of 2.0, to produce elemental sulfur. I can do it. but,
Oxygen is inherently superior to SO2 because of its ready availability in the form of air and its high conversion to sulfur. Comparing reaction equations (2) and (3), the amount of H2S converted to sulfur is the same, but equation (3) using an SO2 oxidant is more effective than equation (2) using an O2 oxidant.
produces 50% more sulfur. For equation (3) to produce 50% more sulfur, equation (3) requires a higher operating temperature than equation (2), provided the sulfur vapor dew point is not exceeded. However, at operating temperatures below 538°C (1000°F), the conversion of H2S to sulfur decreases with increasing temperature. Therefore, without exceeding the dew point, the formula (3
) H2S can be converted to sulfur according to equation (2) at lower temperatures than the oxidizing agent, so there is an inherent advantage when using oxygen as the oxidant over using SO2, namely a higher conversion rate.

When oxygen or SO2 is used as the oxidizing agent, the catalyst of the present invention is highly useful for converting H2S to elemental sulfur. The conversion rate at a given condition is
This will, of course, depend on factors such as operating temperature, operating pressure, water vapor partial pressure and the choice of oxidizing agent. However, the vanadium-bismuth catalysts described above usually convert H2S to elemental sulfur within 10% of the theoretical amount, often within 5%. Also H2S
The vanadium-bismuth catalyst of the present invention has a higher activity than the prior art catalysts, e.g.
U.S. Patent Application No. 700,5 filed June 28, 1976
No. 13 (U.S. Pat. No. 4,243,647) converts H2S to sulfur at higher conversions at lower operating temperatures and/or higher space velocities than the vanadia catalyst disclosed in U.S. Pat. No. 4,243,647.

The following example demonstrates the high activity of vanadium-bismuth catalysts for the oxidation of H2S to elemental sulfur.

Example VI 8.7% by weight of vanadium component as V2O5 and B
Silica containing 12.9% by weight of bismuth component as i2O3 and the balance containing 25% by weight of alumina.
A catalyst was prepared with a support made of alumina. The catalyst was in particulate form with a surface area of 239 m2/g and a compact bulk density of 0.67 g/cc. (This catalyst was prepared in a manner very similar to that described in Example II).

The catalyst (950 g) was charged into an isothermal reactor for treating a feed gas containing about 99% CO2 (on an anhydrous basis) and H2S at concentrations varying from about 750 ppmV to 1200 ppmV. Using. Elemental sulfur produced in the reactor was removed in vapor form and recovered by condensation. Experiments were conducted for a period of more than 5 months, and sample analyzes of feed gas and produced gas were conducted under the operating conditions shown in Table 4, and the data are summarized in Table 4. Regarding the experiment,
It is noteworthy that the catalyst shows no deactivation during the experiment, except when the operating temperature drops below the sulfur vapor dew point temperature and sulfur precipitates on the catalyst. However, this type of deactivation is only temporary, and the activity of the catalyst is fully restored by high temperatures.

As shown in the data in Table 4, the vanadium-bismuth catalyst of the invention has a temperature of 149°C (300°F).
It is active to initiate the conversion of H2S to sulfur at temperatures below: This result is surprising for many reasons. Comparable prior art catalysts---and catalysts known to convert H2S to elemental sulfur with high activity, i.e. 7
10 supported on a 5% SiO2-25% Al2O3 carrier
%V2O5-- is approximately 0.05 kg/cm2 (0.7
psia) at a hydrogen partial pressure of less than approximately 135 °C (275
It is not at all surprising that H2S is active, since it begins to oxidize H2S to sulfur only in the presence of water vapor at temperatures above 100°F (°F). Thus, the catalyst of the present invention proves to be significantly more active than a comparable vanadia catalyst in converting H2S to elemental sulfur, and further improves the aforementioned experiments by approximately 0.18
~． 035kg/cm2 (2.5~5.0psia)
It is surprising when one considers the fact that this was done with water vapor at a partial pressure of . An increase in the amount of water vapor tends to increase the amount of water vapor adsorbed on the catalyst surface, thereby reducing the amount of H2S and O2 (or SO2) adsorption and increasing the onset temperature for the catalyst. However, 0.21kg/cm
Despite the conflicting conditions of 3.0 psia of water vapor, the catalyst used in the present invention has a
It is still active to initiate the reaction between H2S and oxygen at 5 °F), whereas 0.05 kg/cm2
(0.7 psia) Comparable vanadia catalysts at more favorable conditions of water vapor below about 191 °C (375 °
F) or above.

Another surprising aspect of the present invention, as shown by the data in Table 4, is the high stability of the vanadium-bismuth catalyst in the presence of water vapor. As shown in the data in Table 2, vanadia catalysts are rapidly deactivated in the presence of water vapor at temperatures below about 316 °C (600 °F), but the data in Table 4 shows that the ranging from 0.18 to 0.
Vanadium-bismuth catalysts have been shown to resist this type of deactivation even when used in the presence of 2.5-5.0 psia of water vapor.

[0052]

[Table 4]

In a particular embodiment of the present invention, the present invention is particularly useful for treating feed gas streams containing about 5-40% by volume H2S, particularly when the feed gas stream has a relatively high partial pressure, e.g. Approximately 0.14kg/cm2 (2.0psi
a) Above and more usually about 0.28 kg/cm
2 (4.0 psia) or more and contains water vapor,
mixing the feed gas stream with air, preferably in stoichiometric amounts;
The resulting gas mixture is passed through an adiabatic reactor containing a granular vanadium-bismuth catalyst under the conditions described above such that a significant amount of H2S is converted to elemental sulfur vapor. passing the product gas containing elemental sulfur through a sulfur condenser or other suitable means for separating sulfur from the product gas;
The purified product gas containing residual H2S is vented. A portion of the purified product gas is then recycled to a predetermined range, e.g. 3-6% by volume, or below a predetermined maximum.
The recycle gas entering the reactor, typically and preferably containing 5% by volume H2S, is mixed with a feed gas such as a mixture of air and feed gas. The remainder of the purified product gas is treated in one of three ways. These three methods are described below (these methods are applied in embodiments of the present invention in which the H2S content of the gas stream recovered after treatment with the vanadium-bismuth catalyst is too high to be discharged to the atmosphere). can).

(1) H2S in the purified product gas stream
When the volumetric ratio of SO2 to SO2 is about 2.0, the gas stream is heated to a high temperature, e.
900 °F) with a porous refractory oxide-containing catalyst, such as alumina, and
A significant amount of sulfur is converted to elemental sulfur according to reaction equation (3) and recovered, for example, by condensation. In this embodiment of the invention, vanadium-bismuth catalysts, such as those described above, are most preferably used to effect the conversion to sulfur, and such catalysts require lower operating temperatures and/or or under more difficult conditions of high space velocities, H2S is highly active and therefore the same as alumina.
of sulfur.

(2) If the H2S to SO2 volume ratio is substantially greater than 2.0, or if it is desired to vary the H2S to SO2 ratio in the purified product gas stream, is mixed with a sufficient amount of air to give a volume ratio of H2S/(SO2 + O2) of about 2.0 and the resulting gas is contacted with a vanadium-bismuth catalyst under the conditions described above to convert it to elemental sulfur. Alternatively, less preferably, a vanadium-bismuth catalyst may be substituted with a vanadium-bismuth catalyst containing vanadium oxide or vanadium sulfide as a main component supported on a porous refractory oxide support.
sia) at partial pressures below or operating temperatures of approx.
Contact with the mixture at temperatures above 600° F. provides water vapor in the gas mixture. The use of vanadium catalyst is vanadium-
Although it provides a lower activity for converting H2S to sulfur than when using a bismuth catalyst, the lower activity may be appropriate in some cases, for example when the price of the catalyst is particularly important.

(3) Methods (1) and (2) above
If the H2S content of the recovered gas stream after condensing the sulfur or the purified product gas stream is too high to be discharged to the atmosphere, and such gas stream is
2 (because air pollution standards are less stringent for SO2 than for H2S), such a gas stream can be combusted to convert the H2S contained therein to SO2 if it can be discharged into the atmosphere. . Combustion is carried out by heating to temperatures above about 538°C (1000°F) in the presence of excess oxygen and in contact with the vanadium-bismuth catalyst of the present invention described above within the conversion conditions to SO2 described above. It is preferable to do so. The use of vanadium-bismuth catalysts has distinct advantages over thermal combustion; the gas streams to be treated do not require much preheating, and vanadium-bismuth catalysts mostly produce H2S at temperatures below 260 °C (500 °F). It has activity for converting SO2 into SO2.

[0057] The present invention is not limited to the above embodiments, but
For example, by modifying the catalytic process of the present invention, the reaction equation (1
) It is also possible to oxidize H2S to a combination of sulfur and SO2 in a predetermined amount by simply controlling the amount of oxygen between the amount required for (2) and the amount required for reaction equation (2).

Claims (9)

[Claims] Claim 1: In catalytically burning H2S into SO2 by reaction with oxygen in the reaction zone, the combustion is performed in the reaction zone by heating the H2S and oxygen at a temperature of 121° to 316°C (250° to 600°C). °F)
at least 0.07kg/cm2 (1.0ps
ia) A method for oxidizing hydrogen sulfide, characterized in that it is brought into contact with a solid catalyst supporting vanadium and bismuth as main active ingredients in the presence of steam at a partial pressure of: [Claim 2] The water vapor is 0.28 kg/cm2.
2. The method of claim 1, wherein the method is at a partial pressure greater than or equal to (4.0 psia). Claim 3: The above H2S is (a) SO
(b) at least 0.105 kg/cm2 (1.5 psia)
(a) for a period of 90 days, said feed gas stream is introduced into a reaction zone in which said feed gas stream is
at a temperature of 316° C. (250° to 600° F.), comprising a vanadium component and a bismuth component supported as main components on a refractory oxide carrier, with at least some of the vanadium and bismuth components being vanadium oxide or sulfide, respectively. A catalyst present in the form of vanadium and bismuth oxide or bismuth sulfide is contacted in such a way that at least 90% of the H2S is converted to SO2 by reaction with oxygen in the reaction zone, and the catalyst is exposed to H2S for 90 days.
(b) Almost all of the SO generated in the reaction zone is
2. The method of claim 1, wherein a product gas stream containing 2 is removed from the reaction zone. 4. The partial pressure of the water vapor is at least 0.
2. The method of claim 1, wherein the pressure is 1.5 psia. 5. When H2S is catalytically burned by reaction with oxygen in the reaction zone and converted into SO2, the combustion causes the hydrogen sulfide and 121
The vanadium and bismuth active catalyst components are supported on a support material, and the oxygen is supplied in an amount greater than or equal to that required to convert the H2S to SO2 at temperatures maintained between 250° and 900°F. and the vanadium and bismuth components are V2O5 and B, respectively.
a solid catalyst present in a proportion of not less than 5% by weight calculated as i2O3 and at least 90% of the above H2S as SO3
A method for oxidizing hydrogen sulfide, characterized in that it comprises contacting it under conditions such that it is converted to SO2 with almost no formation. [Claim 6] In converting H2S into SO2 by catalytically burning it by reaction with oxygen in the reaction zone,
The combustion occurs between 121° and 482° in the reaction zone.
The above-mentioned H2S and oxygen supplied in quantities in excess of that required to convert the H2S to SO2 are added to a carrier material at a temperature maintained between 250° and 900°F (250° to 900°F), a component effective as a catalyst for vanadium and bismuth. A solid catalyst supported as a main component, and almost all of the above H2S
A method for oxidizing hydrogen sulfide, characterized in that it is converted into SO2 with almost no formation of SO3. 7. A method according to claim 5 or 6, wherein said oxygen is supplied in the form of air and in a substantially excess amount than required to convert said H2S to SO2. Claim 8: The amount of water vapor in the catalyst is 0.28 kg/c.
8. A method according to claim 5, 6 or 7, wherein the partial pressure is greater than or equal to 4.0 psia. 9. The carrier material is a refractory oxide, a hydrophobic crystalline silica, an amorphous aluminosilicate zeolite,
7. The method of claim 6, comprising an element selected from the group consisting of crystalline aluminosilicate zeolites and mixtures thereof.