JPH0475057B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECT OF THE INVENTION INDUSTRIAL APPLICATION The present invention relates to a catalyst and method for the recovery of elemental sulfur from hydrogen sulfide-containing gases, in particular hydrocarbons, hydrogen,
The present invention relates to a catalyst and method for directly recovering elemental sulfur by treating a relatively low concentration hydrogen sulfide-containing gas that coexists with carbon monoxide, carbon dioxide, etc. 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 method consists of thermal conversion, which occurs at high temperatures by burning part of the hydrogen sulfide, and then chimeratile conversion, in which the Claus reaction mainly occurs through contact with an alumina catalyst, i.e., 2H ₂ S + SO ₂ → 3S + 2H ₂ O. The sulfur recovery rate varies depending on the conditions, but
It is about 95-97%. In this conventional method, the solution that absorbed hydrogen sulfide in the previous stage must be regenerated as a treatment before introducing the gas into the Claus reactor, so it requires a lot of thermal energy, especially when the raw material gas also contains carbon dioxide gas. In this case, carbon dioxide gas is also absorbed at the same time as sulfur and hydrogen, so the regeneration energy of the absorption liquid further increases. In addition, if carbon dioxide gas coexists in the raw material gas,
The carbon dioxide gas reacts with sulfur produced during the thermal conversion process, producing organic sulfur compounds such as COS and _CS2 , resulting in a decrease in sulfur recovery rate. Furthermore, if the hydrogen sulfide concentration in the gas supplied to the Claus device is approximately 30% or less, auxiliary fuel is required to compensate for the combustion heat when partially combusting the hydrogen sulfide. Furthermore, although the Claus reaction has an equilibrium advantage at low temperatures, its equilibrium constant Kp is relatively small, so even if three reactors are installed as described above, the sulfur recovery rate is still 97%.
%, and as a countermeasure against sulfur dioxide gas pollution.
It is necessary to install tail gas processing equipment such as the SCOT method and Bevon method. In recent years, as a means of improving the drawbacks of such conventional methods, 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-57-129807 discloses a method of converting elemental sulfur by oxidation in the liquid phase using an alumina catalyst, but this method has low catalyst activity and requires circulation of liquid sulfur. Since the reaction proceeds in the liquid phase, there is a problem with the circulation method. Also, JP-A-58
−161908, JP-A-58-36906, JP-A-58-
Methods of catalytically oxidizing H ₂ S are also disclosed in No. 156508, but all of these require the installation of tail gas treatment equipment. In addition, in order to omit the tail gas treatment process, a method of carrying out the Claus reaction at low temperatures (temperatures below the dew point of sulfur) is disclosed in JP-A-59-11523.
These methods are disclosed in JP-A No. 58-45720, etc., but since the reaction is carried out near the dew point of sulfur, the activity of the catalyst decreases due to the attachment of elemental sulfur to the catalyst. A regeneration process is required, and the catalyst cannot be expected to have a long service life. Problems to be Solved by the Invention In order to solve the above-mentioned conventional drawbacks, hydrogen sulfide is directly oxidized to elemental sulfur without using the reaction 2H ₂ S + SO ₂ → 3S + 2H ₂ O, that is, Noting that the reaction 2H ₂ S+O ₂ →2S+2H ₂ O is extremely advantageous in terms of equilibrium and reaction conditions, the present invention was completed as a result of intensive research. Means for Solving the Constituent Problems of the Invention That is, the first invention is a hydrogen sulfide direct oxidation catalyst containing bismuth oxide or sulfide and antimony oxide or sulfide as catalytically active components; In the invention, a gas containing hydrogen sulfide is heated at a temperature of 200°C in the presence of a catalyst containing bismuth oxide or sulfide and antimony oxide or sulfide as catalytically active components.
This is a method for recovering elemental sulfide directly from a hydrogen sulfide-containing gas by reacting it with molecular oxygen at ~350°C to selectively oxidize hydrogen sulfide and convert it to elemental sulfide. The present invention can be applied to any gas containing hydrogen sulfide, including off-gas from oil refining, purification of gas produced by partial oxidation of coal and heavy oil, and tail gas from Claus sulfur recovery equipment. It is particularly suitable for processing gases with relatively low concentrations of hydrogen sulfide, such as those containing less than 20% by weight. The catalyst will be explained in detail below. This catalyst contains bismuth and antimony components as active factors. Although each of the bismuth component and the antimony component has the activity of oxidizing hydrogen sulfide when used alone, the activity and selectivity are improved by having both components coexisting. The content of the bismuth component is preferably such that the atomic ratio of Sb/(Sb+Bi) is in the range of 0.1 to less than 1.0. If this atomic ratio is less than 0.1, the added effect will be insufficient. When using the catalyst of the present invention consisting of Sb and Bi, it may be in the form of an oxide or a sulfide. Even if the reactor is filled in the form of an oxide, part or all of it acts as a sulfide in a reaction atmosphere containing sulfur compounds and oxygen. The catalyst may be prepared by any method as long as bismuth and antimony easily interact with each other, but by mixing bismuth nitrate dissolved in a nitric acid solution and antimony hydrochloride hydrolyzed, A method of evaporating to dryness and then firing in air at 350 to 700°C is preferred. However, the raw materials are not limited to those mentioned above. That is, bismuth trichloride may be used as a raw material for bismuth, and tartarite K(SbO) C ₄ H ₄ O ₆ may be used as a raw material for antimony. The preparation method is also not limited to the above. In the first step, both components and the carrier are mixed and evaporated to dryness.
Methods such as hydrolyzing both salts and then mixing them, mixing them in a solution, or neutralizing them and then mixing them can be adopted. When bismuth nitrate is used as a bismuth raw material, it may be used as a nitric acid solution as described above,
Alternatively, it may be precipitated with caustic soda and then washed with water, or hydrolyzed and then washed with water. Also, when bismuth trichloride is used, it may be used as a hydrochloric acid solution, or it may be washed with water after hydrolysis. When tartarite is used as an antimony raw material, it is best to precipitate it with dilute hydrochloric acid or dilute nitric acid and then wash it with water. When antimony trichloride is used, it is simply washed with water after hydrolysis. Since the composition consisting of these two components itself has sufficiently high activity, natural products such as zeolite, borosodite, faujasite, and mordenite may be used as carriers. _Al2O3 , _TiO2 , _{ZrO2 , SiO2}
etc. have oxidizing activity and promote the by-production of SO ₂ , making it undesirable to use them as carriers. The temperature conditions for the reaction can be selected over a wide range of 200°C to 350°C. The activity of this catalyst for the reaction of 2H ₂ S + SO ₂ →2S + 2H ₂ O is sufficiently high even at 200°C, and the generated sulfur does not condense on the catalyst surface, making it possible to maintain stable activity for a long period of time. Furthermore, the equilibrium constant of the above reaction is much larger than that of the Claus reaction, so a sufficient desulfurization rate can be achieved even at high reaction temperatures; Operation at temperatures higher than this is not preferable because a side reaction occurs in which SO ₂ is produced and oxidation of accompanying hydrocarbons is promoted. Since the direct oxidation reaction of hydrogen sulfide using the catalyst of the present invention easily proceeds even at normal pressure, there is no need to carry out the reaction under high pressure, and it is economically advantageous to carry out the reaction at the pressure possessed by the supplied raw material gas. preferred. 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
Oxygen enriched with (Pressured Swing Adorption) or membrane separation method, or high purity oxygen with air separation is used. The amount of oxygen to be added is determined by considering the processing purpose and use of the hydrogen sulfide-containing gas to be treated, and the ratio of hydrogen sulfide to oxygen is easily 2:1 to 1:1.
Adjust so that the ratio is about 1. The reactor may be either an isothermal reactor or an adiabatic reactor. Depending on the concentration of hydrogen sulfide contained in the gas to be treated, the amount of gas to be treated, the composition of the accompanying gas, etc., one or more reactors are installed in series. When two or more reactors are installed, multiple stages of combinations of reactors and condensers for the sulfur produced therein are installed in series. Effect According to the present invention, a high desulfurization rate can be achieved even with a low concentration of hydrogen sulfide-containing gas. In addition, it selectively oxidizes only hydrogen sulfide and suppresses the oxidation reaction of hydrocarbons, hydrogen, etc., so it can be used for offgas from oil refining that contains small amounts of hydrogen sulfide, gas produced by partial oxidation of coal and heavy oil, natural gas, etc. Tail gas and the like from the sulfur recovery device can be processed more effectively. Example 1 Catalyst Preparation A predetermined amount of antimony trichloride was hydrolyzed with a 1/2 diluted solution of concentrated nitric acid, followed by aqueous ammonia (28%).
Add 300 ml of the solution, leave it for 30 minutes while stirring, then pass through a sieve, mix the washed product with a predetermined amount of bismuth nitrate dissolved in a 1/3 diluted solution of concentrated nitric acid, and evaporate to dryness. , and calcined in air at 600°C for 5 hours. Reaction test method A quartz reaction tube with an inner diameter of 10 mm was filled with 4 c.c. of catalyst crushed and sized into 8 to 16 meshes.
SV _N2 gas containing _H2S0.5vol %, _O2 0.5vol%
= 2000h ^-1 , supplied at normal pressure, and compared the activity and selective products at 250 to 350°C. Gas analysis is 0.1vol%
The above was carried out using a gas chromatograph, and the following was carried out using a detection tube. Test results The reaction test results are shown in Table 1.

[Table] Example 2 Catalyst Preparation The atomic ratio of Sb/(Sb+Bi) was fixed at 0.5,
After performing the first step of evaporation to dryness using the method shown in Example 1, Sb and Bi were converted into oxides (Sb ₂ O ₃ and
Zeolite was mixed to a predetermined content (Bi ₂ O ₃ ), evaporated to dryness, and then calcined in air at 600° C. for 4 hours. Reaction test method The reaction test was conducted in the same manner as in Example 1. Test results The reaction test results are shown in Table 2.

[Table] From this table, it can be seen that if Sb and Bi are contained as oxides at 50% or more, the activity is sufficient even if a carrier such as zeolite is used. Example 3 When targeting hydrogen sulfide contained in natural gas, coal gas, etc., loss due to combustion of hydrocarbons, H ₂ , CO, etc. becomes a problem, so a catalyst with catalyst number 10 is used to convert H ₂ S Hydrocarbons, _H2 and CO in coexistence
The flammability of this material was investigated. A quartz reaction tube with an inner diameter of 10 mm was filled with 4 c.c. of catalyst crushed and sized into 8 to 16 meshes, and H ₂ S 2.5 vol%,
N ₂ gas containing 2.5 vol% of O ₂ is mixed with any one of CH ₄ , H ₂ , or CO to a concentration of 2 vol%, and the mixture is supplied at SV=2000 h ^-1 and normal pressure, The combustion onset temperature of CH ₄ , H ₂ , and CO at ~400°C was investigated. Gas analysis was performed using a gas chromatograph. The test results are shown in Figure 1. When using the catalyst of the present invention, hydrogen is below 250℃, CO is below 300℃,
It can be seen that _C4 hydrocarbons do not burn below 320℃, and _CH4 does not burn below 400℃. Example 4 In order to find out the optimum temperature for use, the reaction temperature was determined to be active and selective by the test method described in Example 1 using the catalyst No. 4 mentioned above (atomic ratio of Sb (Sb + Bi) 0.5). The impact of this study was examined. The relationship between reaction temperature and H ₂ S conversion rate is shown in FIG. 2, and the relationship between reaction temperature and outlet SO ₂ is shown in FIG. 3. It has been shown that the optimal temperature for use of a catalyst with this composition is preferably 200 to 300°C, since sufficient activity cannot be obtained at temperatures below 200°C, and selectivity decreases at temperatures above 300°C. Application example 1 As an example of processing gas containing hydrogen sulfide at a low concentration, H ₂ S: 1 vol%, SO ₂ : 0.5 vol%, COS and
The case where it is applied to the tail gas treatment of a Claus method sulfur recovery device containing 0.06 vol% of CS ₂ is shown. In FIG. 4, the Claus process tail gas having the above composition is supplied from the supply line 4 to the water point column 1 filled with a water point catalyst such as Co-Mo or Ni-Mo, and _SO2 , COS, CS2 _, etc. in the tail gas are It reacts with hydrogen supplied from line 5 and is converted into H ₂ S. The gas that has undergone the above reduction step is supplied to a reactor 2 filled with an Sb-Bi catalyst, and reacts with oxygen in the air supplied from a line 6 to produce elemental sulfur. The generated elemental sulfur is condensed and separated in a condenser 3 and recovered through a recovery line 7. The gas that has been separated and recovered with most of the H ₂ S as elemental sulfur is led directly to the incinerator through line 8, where the H ₂ S is converted to SO ₂ and released into the atmosphere. According to the method of the present invention, which uses an Sb-Bi catalyst to recover elemental sulfur directly from _H2S -containing gas, unreacted
Since the amounts of H ₂ S and by-product SO ₂ are extremely small, they can be converted into SO ₂ using an incinerator and then released directly into the atmosphere. Effects of the invention By directly oxidizing hydrogen sulfide-containing gas, it is possible to eliminate the pretreatment in the conventional Claus method, i.e., the absorption and regeneration operation of hydrogen sulfide using an amine solution, etc., the combustion furnace for partially combusting hydrogen sulfide, and the waste heat. There is no need for boilers, etc., and construction costs and utilities can be reduced. Equilibrium constant for the reaction 2H ₂ S + SO ₂ → 3S + 2H ₂ O
Since Kp is extremely large and the catalyst according to the present invention has excellent activity and selectivity for this reaction,
Hydrogen sulfide can be converted to elemental sulfur with extremely high recovery rates. Therefore, there is no need for tail gas processing equipment or a catalyst regeneration process using low-temperature operation, which is required in the conventional Claus method, and construction costs can be significantly reduced. There is no catalyst deterioration even at high temperatures, the reaction temperature range can be widened, a decrease in catalyst activity due to generated sulfur, etc. can be avoided, and high activity can be maintained for a long period of time. Since it selectively oxidizes only hydrogen sulfide and suppresses the oxidation reaction of hydrocarbons and hydrogen, it can be produced by partial oxidation of hydrocarbon raw materials containing a small amount of hydrogen sulfide, such as oil refinery offgas, coal, oil, etc. It can be effectively used in a wide range of applications, including the purification of raw material gas for chemical industries, and the treatment of tail gas from conventional sulfur recovery equipment.

[Brief explanation of drawings]

Figure 1 shows the results of measuring the flammability of hydrocarbons, H ₂ , CO, etc. The vertical axis is the conversion rate (%) of each, the horizontal axis is the temperature (°C), ○ is CH ₄ , △ The mark is C ₄
Hydrocarbons, ▽ mark indicates H ₂ , □ mark indicates CO (corresponding to Example 3). Figure 2 shows the atomic ratio of Sb/(Sb+Bi)
This is a diagram showing the relationship between reaction temperature and H ₂ S conversion rate when using a catalyst of 0.5%. The vertical axis is the H ₂ S conversion rate (%),
The horizontal axis indicates temperature (°C) (corresponding to Example 4). Third
The figure shows the relationship between reaction temperature and outlet SO ₂ , and the vertical axis indicates the SO ₂ concentration (ppm) at the reactor outlet (corresponding to Example 4). FIG. 4 shows a process flow sheet for treating gas containing low concentration hydrogen sulfide, such as the tail gas of a Claus process sulfur recovery device.

Claims (1)

[Claims] 1. A hydrogen sulfide direct oxidation catalyst comprising bismuth oxide or sulfide and antimony oxide or sulfide as catalytically active components. 2 The atomic ratio of Sb/(Sb+Bi) in the catalyst is 0.1 to
1. The catalyst according to claim 1, wherein the catalyst is less than 1.0. 3. In the presence of a catalyst containing bismuth oxide or sulfide and antimony oxide or sulfide as catalytically active components, a gas containing hydrogen sulfide is heated at a temperature of 200 to 350.
A method for recovering elemental sulfide directly from a hydrogen sulfide-containing gas by selectively oxidizing hydrogen sulfide and converting it to elemental sulfur by reacting it with molecular oxygen at ℃. 4 The atomic ratio of Sb/(Sb+Bi) in the catalyst is 0.1 to
3. The method according to claim 3, which is less than 1.0.