JPH0558774B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL FIELD OF APPLICATION The present invention relates to a method for recovering elemental sulfur from hydrogen sulfide-containing gases, in particular hydrocarbons, hydrogen, carbon monoxide,
This invention relates to a method for directly recovering elemental sulfur by treating a relatively low concentration hydrogen sulfide-containing gas that coexists with carbon dioxide and the like. Prior Art Conventional methods for recovering elemental sulfur from hydrogen sulfide-containing gases include:
First, use a suitable absorption liquid, such as hot potassium carbonate solution,
Absorb hydrogen sulfide using an amine-based absorption liquid,
By regenerating the solution, a relatively high concentration of hydrogen sulfide gas is obtained, a portion of which is combusted to produce sulfur dioxide gas, and the sulfur dioxide gas is reacted with the remaining hydrogen sulfide to recover elemental sulfur through the so-called Claus reaction. are doing. This Claus reaction consists of thermal conversion, which progresses at high temperatures by burning part of the hydrogen sulfide, and then catalyst conversion, in which it is brought into contact mainly with an alumina catalyst.The sulfur recovery rate varies depending on the conditions, but 95
reaching ~97%. In this conventional Claus method, the solution that has absorbed hydrogen sulfide must be regenerated as a treatment before introducing the gas into the Claus apparatus, which requires a large amount of thermal energy, and in particular, carbon dioxide gas is also present in the raw material gas. If the absorbent contains hydrogen sulfide, carbon dioxide gas is also absorbed at the same time as hydrogen sulfide, so the regeneration energy of the absorption liquid increases further. In addition, when carbon dioxide gas coexists, the carbon dioxide gas entrained in the gas supplied to the Claus device reacts with the sulfur produced during the thermal conversion process of hydrogen sulfide, producing organic sulfur compounds such as COS and _CS2 . This results in a decrease in sulfur recovery rate. Furthermore, if the hydrogen sulfide concentration in the gas supplied to the Claus device is about 30% or less, auxiliary fuel is required to supplement the combustion heat when hydrogen sulfide is partially combusted. In recent years, as a means of improving the drawbacks of the conventional Claus process, a method has been disclosed in which hydrogen sulfide-containing gas is directly catalytically oxidized in the presence of a catalyst to convert it into elemental sulfur. Specifically, JP-A-56-169396 discloses a method of oxidizing in a liquid phase using an alumina catalyst, but in this method, the activity of the catalyst is low, and liquid sulfur is circulated to carry out the reaction in a liquid phase. There is a problem with the circulation method used to advance the process. Furthermore, JP-A-55-51816 uses V ₂ O ₅ /carrier, and JP-A-58-156508 uses V 2 O 5 /carrier.
V ₂ O ₅ −Bi ₂ O ₃ /carrier are used as catalysts, but these have insufficient activity unless the V ₂ O ₅ content is high, and V ₂ O ₅
If the carrier contains alumina or an alumina component, it may become sulfated during operation, causing a decrease in activity. Problems to be Solved by the Invention The present invention solves the drawbacks of the conventional method as described above, and also realizes that the Claus reaction is equilibriumally advantageous under pressure, and that the separation and collection of produced sulfur is effective under pressure. Focusing on the fact that the sulfur recovery rate can be improved due to the fact that it can be carried out in a practical manner, the present invention was completed as a result of intensive research. (Structure of the Invention) Means for Solving the Problems The present invention provides an oxide or sulfide of vanadium and one or more oxides or sulfides selected from the group consisting of tungsten, phosphorus, and uranium. The vanadium content in _the catalyst is 1 to 10% by weight as _V2O5 , and the atomic ratio of M/V (where M represents tungsten, phosphorus, or uranium) is 0.1. Gas containing hydrogen sulfide is heated to a temperature of 120 to 450 in the presence of a catalyst that is ~1.0
℃ and a pressure of 1 to 100 atmospheres, reacts with the amount of molecular oxygen required to stoichiometrically oxidize 1/3 of hydrogen sulfide to sulfur dioxide gas, selectively oxidizing hydrogen sulfide and converting it to elemental sulfur. A method for recovering elemental sulfur from a hydrogen sulfide-containing gas. The present invention can be applied to any gas containing hydrogen sulfide, including natural gas,
Particularly suitable for processing gases that have relatively low concentrations of hydrogen sulfide, such as partial oxidation of heavy oil or crude oil, gas produced by pressurized gasification of quartz, etc., where the gas itself has pressure and the content of hydrogen sulfide is 20% by volume or less. Are suitable. The catalyst, which is most important in the present invention, will be explained in detail below. This catalyst supports a composition consisting of a vanadium oxide or sulfide as an active factor and one or more oxides or sulfides selected from the group consisting of tungsten, phosphorus, and uranium as a promoter. This is what I did. The vanadium content is suitably in the range of 1 to 10% by weight as V ₂ O ₅ . If the content is less than 1%, the activity is low;
Above this level, the activity is saturated. Furthermore, the atomic ratio of M/V (where M represents tungsten, phosphorus, or uranium) is adjusted to be in the range of 0.1 to 1.0. If this atomic ratio is less than 0.1, the addition effect will be insufficient, and if it is more than 1.0, it will promote the oxidation of hydrocarbons coexisting in the raw material gas, such as hydrogen and carbon monoxide, which is not preferable. A composition consisting of these two components exhibits activity by itself, but this activity and stability can be further improved by supporting it on a carrier such as TiO ₂ . In addition to TiO ₂ , ZrO ₂ , SiO _{2 ,} etc. can be used as the carrier, but Al ₂ O ₃ , MgO, etc. are not preferred because they undergo sulfation during use. The addition of oxides or sulfides of tungsten, phosphorus, or uranium contributes to improving catalyst activity, stability, and selective oxidation properties, because, for example, WO ₃ forms a solid solution with V ₂ O ₅ , The purpose is to improve the catalytic activity by changing the electronic state of V ₂ O ₅ , and V ₂ Q ₅ has a melting point of 690°C and is a compound that is prone to sintering at high temperatures, but WO ₃ It has the function of suppressing the sintering of V ₂ O ₅ by forming a solid solution or compound with V ₂ O ₅ . The metal used in the catalyst is in the form of carbon dioxide or sulfide. The catalyst may be prepared by either an impregnation method or a kneading method, but a co-impregnation method or a co-kneading method is preferred in order to produce a solid solution or compound of V ₂ O ₅ and a promoter such as WO ₃ . It is not preferable to add them separately. The temperature conditions for the reaction can be selected over a wide range from 120°C to 450°C. The lower the temperature, the better in terms of the equilibrium of the Claus reaction, but temperatures below 120°C are disadvantageous because the liquid sulfur produced becomes solid. Further, operation at a temperature higher than 450° C. is not preferable, both from the viewpoint of the equilibrium of the Claus reaction and from the standpoint of accelerating the oxidation of accompanying hydrocarbons, hydrogen, and the like. The appropriate reaction pressure is normal pressure (1 atm) to 100 atm. Although a higher pressure is more advantageous in terms of the Claus reaction, it is preferable from an economic standpoint to select the actual pressure at the pressure possessed by the feedstock gas. The molecular oxygen supplied as an oxidizing agent can be either oxygen or air. If air is used, nitrogen will be accompanied, and the size of the equipment will need to be increased accordingly, so consider the hydrogen sulfide concentration and the amount of gas to be treated.
Care must be taken to enrich oxygen or use highly purified oxygen. i.e. PSA
(Pressed Swing Adsorption) or membrane separation method, or use high purity oxygen obtained by air separation. The amount of oxygen added is such that the ratio of hydrogen sulfide to sulfur dioxide gas is 2:1, that is, the amount of oxygen required to stoichiometrically oxidize 1/3 of hydrogen sulfide to sulfur dioxide gas. Effects According to the present invention, only hydrogen sulfide is selectively oxidized, and oxidation reactions to hydrocarbons, hydrogen, etc. are suppressed, so that it is possible to purify hydrocarbon raw materials containing a small amount of hydrogen sulfide, such as natural gas, and to process elemental sulfur. Collection can be performed at the same time. Example 1 Catalyst Preparation Ammonium metavanadate was used as the raw material V, ammonium salt was used as W, phosphoric acid was used as P, and uranyl nitrate was used as U. An example of the preparation of V ₂ O ₅ -WO ₃ /TiO ₂ catalyst is shown below.
Ammonium metavanadate is suspended in water, and oxalic acid solution is gradually added to it to obtain a blue solution. Add ammonium tungstate to this and dissolve it, V
- A mixed solution of W is prepared. When supporting on a carrier, a method was used in which the above solution corresponding to the pore volume of the carrier was dropped onto the carrier (pore filling method), or a method was used in which the carrier was added to the above solution, kneaded well, and then evaporated to dryness. Drying was carried out at 110°C for 12 hours, and baking was carried out in air at 500°C for 4 hours. Reaction test method A quartz reaction tube with an inner diameter of 10 mm was filled with 2 c.c. of catalyst crushed and sized into 3 to 16 meshes, and the raw material gas was
The reaction was carried out at SV=7000h ^-1 and normal pressure. Gas analysis is performed using gas chromatography for 0.1vol.% or more.
% or less, a detection tube was used. Test results Effect of V content As raw materials: H ₂ S: 2.5 vol.%, O ₂ : 1.25 vol.%
Sulfurization of the above composition using N ₂ gas containing N 2 gas, with the W/V atomic ratio fixed at 0.5, and in the presence of a catalyst in which the V content was varied between 0.5 and 20 wt% as V ₂ O ₅ . Hydrogen-containing gas was reacted at 250°C. From the start of the reaction
The reaction results after 10 hours are shown in Table 1.

[Table] Effect of W/V atomic ratio As raw materials: H ₂ S: 2.5 vol.%: O ₂ : 1.25 vol.%,
_N2 gas containing _CH4 :10vol.% was used. 10% from the start of the reaction at 450℃ when the content of V ₂ O ₅ was fixed at 5 wt% and the content of WO ₃ was changed.
The reaction results after time are shown in Table 2.

[Table] While W has the effect of improving activity, too much W causes CH ₄ oxidation. Effect of accelerator As raw materials: H ₂ S: 2.5 vol.%, O ₂ : 1.25 vol.%
Table 3 shows the reaction results 10 hours after the start of the reaction at 250° C. when N ₂ gas containing WO 3 was used and a promoter other than WO ₃ was used.

[Table] Effect of carrier As raw materials: H ₂ S: 2.5 vol.%, O ₂ : 1.25 vol.%
Table 4 shows the reaction results at 250°C when N ₂ gas containing TiO 2 was used and a carrier other than TiO ₂ was used.
It has been shown that in the case of using an Al ₂ O ₃ carrier, the H ₂ S conversion rate deteriorates significantly over time.

[Table] Effect of additives on deterioration As raw materials: H ₂ S: 2.5 vol.%, O ₂ : 1.25 vol.%
Using _N2 gas containing and _V2O as an additive to ₅
Table 5 shows the change over time in the H ₂ S addition rate of the catalyst to which WO ₃ was added (reaction temperature: 450° C.). When only V ₂ O ₅ was used, the H ₂ S conversion rate decreased significantly 50 hours after the start of the reaction, but when WO ₃ was added, there was almost no change. (Application example)

[Table] Explains the case where natural gas containing hydrogen sulfide is completely desulfurized. As an example, _CH4 : 80vol%,
_H2S : 10vol%, _CO2 : 10vol%, pressure: 60Kg/ ^cm2
G. Temperature: Natural gas at 40℃ is used as a raw material. In FIG. 1, 1 is a Claus reactor filled with the above-mentioned catalyst. Hydrocarbon gas containing hydrogen sulfide is supplied under pressure to the reactor 1 from the raw material supply line 2 and reacts with oxygen supplied from the line 3 to produce elemental sulfur. The generated sulfur is condensed and separated in a condenser 4 and recovered in liquid form through a recovery line 5. A plurality of stages of the reactor and condenser are provided in series as necessary. (Claus process) In the gas in which most of the hydrogen sulfide contained is separated as elemental sulfur, sulfur and sulfur oxides such as SO ₂ that could not be separated and recovered remain, and COS due to side reactions remains. Since organic sulfur compounds such as , CS ₂ , etc. are present, this is led to the hydrogenation tower 6 and treated with a hydrogenation catalyst (Co-Mo type or Ni-Mo type).
The remaining sulfur and sulfur oxides are converted into hydrogen sulfide by reacting with hydrogen supplied from line 7 in the presence of hydrogen. (Reduction process) The gas from the reduction process is led to the absorption tower 8, and trace amounts of hydrogen sulfide and carbon dioxide in the gas are completely absorbed and removed using an appropriate collected liquid (absorption process). The hydrocarbon gas that has been purified by completely removing hydrogen sulfide and carbon dioxide gas by the method of the present invention described above is
Although it may be used as raw material or fuel for the next process as it is, in FIG.
The figure shows the case where the gas is shipped as liquefied gas. The absorption liquid that has sufficiently absorbed hydrogen sulfide and carbon dioxide gas in the absorption tower 8 is led to the regeneration tower 12 through a line 11, heated, releases hydrogen sulfide and carbon dioxide gas, and then is circulated and supplied to the absorption tower 8 through a line 13. . This absorption and regeneration step is the same process used in conventional methods, but whereas conventional methods had to treat the entire amount of hydrogen sulfide present in the feedstock hydrocarbon gas, this process In this case, most of the hydrogen sulfide is recovered as elemental sulfur, and then only a trace amount of hydrogen sulfide can be treated, which greatly reduces the load. The hydrogen sulfide and carbon dioxide gas discharged from the regeneration tower 12 can also be circulated and supplied to the Claus reactor 2 via the line 14. In this way, almost all of the hydrogen sulfide in the raw material gas can be recovered as elemental sulfur. With conventional catalysts, the oxidation reaction of hydrocarbons proceeds at the same time as the oxidation reaction of hydrogen sulfide, so it is difficult to selectively oxidize hydrogen sulfide contained in hydrocarbons and recover it as sulfur. However, by using the catalyst according to the present invention, it is possible to simultaneously purify hydrocarbon gas and recover elemental sulfur. By carrying out the above process using a catalyst with V ₂ O ₅ : 5.0%, W/V atomic ratio: 0.5, and TiO ₂ carrier, CH ₄ in the raw material gas is converted into high purity CH ₄ without virtually any loss. It will be collected. (Effects of the invention) By directly oxidizing hydrogen sulfide-containing gas, it is possible to perform pretreatment using the conventional Claus method, that is, absorption and regeneration operation of hydrogen sulfide using an amine solution, etc., a combustion furnace for partially combusting hydrogen sulfide, There is no need for waste heat boilers, etc., and construction costs and utilities can be reduced. Since the catalyst is highly active and can be operated under high pressure, reactors and the like can be made with a small capacity, and a high sulfur recovery rate can be obtained. Therefore, even when installing tail gas treatment equipment, it is economical as it requires a smaller capacity than conventional equipment. There is little deterioration of the catalyst even at high temperatures, and the reaction temperature range can be widened. Since only hydrogen sulfide is selectively oxidized and the oxidation reaction of hydrocarbons, hydrogen, etc. is suppressed, it is possible to simultaneously refine hydrocarbon raw materials that contain small amounts of hydrogen sulfide, such as natural gas, and recover elemental sulfur. .

[Brief explanation of drawings]

FIG. 1 shows a process flow sheet in which the present invention is used to completely desulfurize natural gas containing hydrogen sulfide and simultaneously recover elemental sulfur.

Claims (1)

[Claims] 1. A composition comprising a vanadium oxide or sulfide and one or more oxides or sulfides selected from the group consisting of tungsten, phosphorus, and uranium, supported on a carrier. Vanadium content in the catalyst is 1 to 10% by weight as V ₂ O ₅ , M/V
In the presence of a catalyst with an atomic ratio of 0.1 to 1.0 (where M represents tungsten, phosphorus, or uranium), a gas containing hydrogen sulfide is heated at a temperature of 120 to 450°C and a pressure of 1.
It consists of selectively oxidizing hydrogen sulfide and converting it to elemental sulfur by reacting it with the amount of molecular oxygen required to stoichiometrically oxidize 1/3 of hydrogen sulfide to sulfur dioxide gas at ~100 atmospheres. A method for recovering elemental sulfur from hydrogen sulfide-containing gases. 2 A composition consisting of a vanadium oxide or sulfide and one or more oxides or sulfides selected from the group consisting of tungsten, phosphorus, and uranium is supported on a carrier, and Vanadium content is 1-10% by weight as _V2O5 , _M /
A catalyst for selectively oxidizing hydrogen sulfide and converting it into elemental sulfur, in which the atomic ratio of V (where M represents tungsten, phosphorus, or uranium) is 0.1 to 1.0.