JPS6161638A - Catalyst and method for recovering directly elemental sulfur from hydrogen sulfide-containing gas - Google Patents

Abstract

PURPOSE:To enhance the activity and selectivity of the catalyst and to convert hydrogen sulfide into elemental sulfur in extremely high yield by incorporating a bismuth component and an antimony component in a specified ratio to form the catalyst for directly oxidizing hydrogen sulfide. CONSTITUTION:The material obtained by dissolving the nitrate of bismuth into an aq. nitric acid soln. and the material obtained by hydrolyzing the hydrochloride of antimony are mixed. The mixture is evaporated to dryness, and calcined in an air current at 350-700 deg.C to obtain a catalyst for oxidizing directly hydrogen sulfide having 0.1-1.0 atomic ratio of Sb/(Sb+Bi). A hydrogen sulfide-contg. gas is allowed to react with molecular oxygen at 200-350 deg.C in the presence of said catalyst for oxidizing directly hydrogen sulfide, and the hydrogen sulfide is selectively oxidized to elemental sulfur which is recovered. The off-gas from petroleum refineries, the partially oxidized gas of coal and heavy oil, natural gas, etc., can be exemplified as said hydrogen sulfide-contg. gas.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a catalyst and method for recovering elemental sulfur from hydrogen sulfide-containing gases, particularly hydrocarbons, hydrogen.

- This invention relates to a catalyst and method for directly recovering elemental sulfur by treating a relatively low concentration hydrogen sulfide-containing gas in which carbon oxide, carbon dioxide, etc. coexist.

[Construction and addition] The conventional and common methods for recovering elemental sulfur from such hydrogen sulfide-containing gases are:

First, use a suitable absorbing liquid 1, such as a mature acid potassium solution.

Hydrogen sulfide is absorbed 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. Elemental sulfur is recovered by the so-called Claus reaction. This method consists of thermal conversion, which progresses at high temperatures by burning part of the hydrogen sulfide, and then catalytic conversion, in which the Claus reaction mainly occurs through contact with an alumina catalyst, that is, 2H2S+SO2 → 3S+, 2H20, and sulfur The recovery rate varies depending on the conditions, but is approximately 95 to 97%.

In this conventional method, the solution that has absorbed hydrogen sulfide must be regenerated as a treatment before introducing the gas into the Claus reactor, which requires a large amount of thermal energy.
In particular, when the raw material gas also contains carbon dioxide gas, the carbon dioxide gas is also absorbed at the same time as hydrogen sulfide, so the regeneration energy of the absorption liquid further increases.

Furthermore, when carbon dioxide gas coexists in the raw material gas, the carbon dioxide gas reacts with sulfur produced in the thermal conversion process to produce organic sulfur compounds such as COS and CSz, resulting in a decrease in sulfur recovery rate.

In addition, the hydrogen sulfide concentration in the gas supplied to the Claus device is approximately 3
Below 0%, auxiliary fuel is required to compensate for the heat of combustion when hydrogen sulfide is partially combusted.

Furthermore, the Claus reaction is more advantageous in terms of equilibrium at lower temperatures, but its average and constant Kp are relatively small, so even if three stages of reactors are installed as described above, the sulfur recovery rate is about 97%, and the sulfur dioxide As a countermeasure against gas pollution, it is necessary to install tail gas processing equipment such as the 5COT method and the Be-Pon 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. That is, JP-A-57-
No. 129807 discloses a method of converting elemental sulfur by oxidation in the liquid phase using an alumina catalyst, but in this method, the activity of the catalyst is low, and the reaction is carried out in the liquid phase by circulating liquid sulfur. There is a problem with the circulation method used to advance the process. Also, JP-A-58-161908, JP-A-58-36906
Methods of catalytically oxidizing H2S are also disclosed in Japanese Patent Application Laid-Open No. 156508, but all of these methods require the installation of till gas processing equipment.

In addition, for the purpose of omitting the tail gas treatment step, methods of carrying out the Claus reaction at low temperatures (temperatures near or below the dew point of sulfur) are disclosed in JP-A-59-11523 and JP-A-58-4.
No. 5720, etc., but these methods carry out the reaction near the dew point of sulfur, so a catalyst regeneration step is required because elemental sulfur attaches to the catalyst and the activity of the catalyst decreases. You cannot expect a long lifespan.

Let's see the light. In order to eliminate the drawbacks of the conventional method as mentioned above, we
+ Focusing on the fact that the reaction of directly oxidizing hydrogen sulfide to elemental sulfur, i.e., the reaction of 2H2S+02→2S+2H20, is extremely advantageous in terms of equilibrium and reaction conditions, without relying on the reaction of S 02 → 3S + 2H20, we conducted extensive research. As a result, the present invention was completed.

That is, the first invention is a hydrogen sulfide direct oxidation catalyst containing a bismuth component and an antimony component, and the second invention is
By reacting a gas containing hydrogen sulfide with molecular oxygen at a temperature of 200 to 350°C in the presence of a catalyst containing a bismuth component and an antimony component to selectively oxidize hydrogen sulfide and convert it to elemental sulfur. This method recovers elemental sulfur directly from hydrogen sulfide-containing gas.

The present invention can be applied to any gas containing hydrogen sulfide, such as off-gas from oil refining, purification of gas produced by partial oxidation of coal◆heavy oil, etc., and treatment of still gas from Claus sulfur recovery equipment. It is particularly suitable for treating gases with a relatively low concentration of hydrogen sulfide, such as 20% by volume or less.

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 O21, the effect of addition is insufficient.

When using a wood-based catalyst 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 preferred method is to evaporate to dryness and then sinter in air at 350 to 700°C.

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 (S bo) C4 can be used as a raw material for antimony.
You may use 40g of H.

The preparation method is not limited to the above. In the first stage of mixing the zero image component and the carrier and evaporating to dryness, the image border may be mixed after hydrolysis, mixed in a solution, or mixed after neutralization, etc. method can be adopted. When bismuth nitrate is used as the bismuth raw material, it may be used as a nitric acid solution as described above.

Alternatively, it may be precipitated with sodium hydroxide and washed with water, or hydrolyzed and then washed with water. Also, when using bismuth trichloride, it may be used as a hydrochloric acid solution or washed with water after hydrolysis. When tartarite is used as an antimony raw material, it may be precipitated with dilute hydrochloric acid or dilute nitric acid and then washed with water. When antimony trichloride is used, it is simply hydrolyzed and then washed with water.

Since the composition consisting of this image component itself has a sufficiently high activity, natural products such as stone, borosodite, faujasite, and mordenite may be used as carriers.
Since 120a, TiO2, Zr0z, 5iOz, etc. have oxidizing activity, they promote the by-production of SO2, and are therefore not preferable to be used as extrusions.

The temperature conditions for the reaction can be selected over a wide range from 200'C to 350'O.
The activity for the reaction of 2S+02 and 2S+2H20 is sufficiently high even at 200"O, and the produced sulfur does not condense on the catalyst surface, making it possible to maintain stable activity for a long period of time.

Furthermore, since the equilibrium constant of the above reaction is much larger than that of the Claus reaction, a sufficient desulfurization rate can be achieved even at high reaction temperatures; Operation at temperatures higher than this is not preferred because a side reaction of reacting with oxygen to produce SO2 occurs and also promotes oxidation of accompanying hydrocarbons.

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. 9 if using air
Since the hydrogen sulfide concentration and the amount of gas to be treated must be taken into consideration, oxygen enrichment or high-purity oxygen should be used. It is necessary to take precautions such as: That is, P, S
,A.

(Pressured 5w1n8Adsorptio
Oxygen enriched by the 119 separation method or high purity oxygen obtained by 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 hydrogen sulfide to oxygen ratio is 2:1 to 1:1 by volume.
Adjust so that the ratio is about l.

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, a combination of one reactor and a condenser for the sulfur produced therein is installed in series.

According to the present invention, a high deMization rate can be achieved even with a gas containing hydrogen sulfide at a low concentration. In addition, it selectively oxidizes only sulfide water and hydrogen, suppressing the oxidation reaction of hydrocarbons and hydrogen, so it can be used for off-gas from petroleum refining that contains small amounts of hydrogen sulfide, gas produced by partial oxidation of coal and heavy oil, etc. Gas, tail gas, etc. of the sulfur momme recovery device can be processed more effectively.

Catalyst preparation Hydrolyze a specified amount of antimony trichloride with a 1/2 diluted solution of concentrated nitric acid, add 300ml of ammonia water (28%), leave for 30 minutes with stirring, then filter and wash. and a predetermined amount of bismuth nitrate dissolved in a l/3 diluted solution of concentrated nitric acid, and after evaporating to dryness,
5 hours at ℃.

Baked in air.

■Reaction test method ``A quartz reaction tube with an inner diameter of 10 mm was filled with 4 cc of catalyst crushed and sized into 8 to 16 meshes, and H2SO, 5 vol.
, 5v=zooo of N2 gas containing 020.5VO1%
The activity and selectivity were compared between 250 and 350° C. by supplying h-t and normal pressure. Gas analysis is 0. An IV of 91% or higher was performed using a gas chromatograph, and an IV of 91% or higher was performed using a detection tube.

(◇Examination results The reaction test results are shown in the IT table.

Table 1 ■ Catalyst preparation S b/ (S b + B i) +7) Atomic ratio 0.5
After fixing to After drying, it was fired in air at 600″C for 14 hours.

■Reaction test method The same method as in Example 1 was used.

■Exam results The reaction test results are shown in Table 2.

Table 2 From this table, it can be seen that if sb and Bi are contained in an amount of 50% or more as oxides, the activity is sufficient even if a carrier such as zeolite is used.

When dealing with hydrogen sulfide contained in natural gas, coal gas, etc., loss due to combustion of hydrocarbons, H2, Go, etc. becomes a problem, so a catalyst with catalyst number 1o is used to treat hydrogen sulfide in the coexistence of H2S. The combustibility of hydrocarbons, H2 and CO was investigated.

A quartz reaction tube with an inner diameter of 10 mm was filled with 4 cc of catalyst crushed and sized into 8 to 16 meshes, and 2.5 vol. of H2S was added.
, CH4, H2, to N2 gas containing Oz2.5vo1%,
Mix any one type of Co gas to 2vo 1% and supply it at 5v = 2000h-1 at normal pressure,
250~400'C! The combustion start temperatures of CH4, H2, and Co were 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 does not burn at 250°C or below, CO does not burn at 300'0 or below, 04 hydrocarbons do not burn at 320'0 or below, and CH4 does not burn at 400°C or below. Recognize.

"Support 1" In order to know the optimum temperature for use, use the catalyst number 4 mentioned above (S
Atomic ratio of b / (Sa, b + B i ) 0.5
), the effect of reaction temperature on activity and selectivity was investigated using the test method described in Example 1.
The relationship between reaction temperature and H2S conversion rate is shown in Figure 2, and the relationship between reaction temperature and outlet 502 is shown in Figure 3. Below 200°C, sufficient activity cannot be obtained, and above 300°C, selectivity is poor. The optimum operating temperature for a catalyst with this composition is 20
It has been shown that the temperature is preferably 0 to 300°C.

[As an example of processing gas containing hydrogen sulfide at a low concentration, H2
A case is shown in which the present invention is applied to tail gas treatment of a Claus process sulfur recovery device containing 01% S:IV, 1% 302:0.5VO, 1% cos and C52:0.06VO.

In FIG. 4, the Claus process tail gas having the above composition is supplied from a supply line 4 to a hydrogenation column 1 filled with a hydrogenation catalyst such as 0-Mo or N1-Mo.

502, CO3, C52, etc. in the tail gas are on line 5.
It reacts with hydrogen supplied from the source and is converted to H2S.

The gas that has undergone the reduction step h is supplied to a reactor 2 filled with 5b-Bi contactors, 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.

) 125, most of which was separated and recovered as elemental sulfur, was directly led to the incinerator through line 8.
H2S is converted to 502 and released into the atmosphere.

According to the method of the present invention in which elemental sulfur is directly recovered from H2S-containing gas using a 5b-Bi catalyst, the amount of unreacted H2S and by-product 502 is extremely small.
After converting to 02, it is possible to release it directly into the atmosphere.

11th Emperor ■By directly oxidizing hydrogen sulfide-containing gas.

Pretreatment in the conventional Claus method, that is, absorption and regeneration of hydrogen sulfide using an amine solution, a combustion furnace for partially burning the hydrogen sulfide, a waste heat boiler, etc. are no longer required, and construction costs and
Utilities can be saved. (1) The equilibrium constants K and p of the reaction 2H2S+SO2→3S+2H20 are 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.

(2) There is little deterioration of the catalyst even at high temperatures, allowing a wide reaction temperature range, avoiding deterioration of catalyst activity due to bacterial growth, and maintaining high activity for a long period of time.

■It selectively oxidizes only hydrogen sulfide and suppresses the oxidation reaction of hydrocarbons and hydrogen, so it is produced by partial oxidation of hydrocarbon raw materials containing small amounts of hydrogen sulfide, such as oil refinery offgas, coal, oil, etc. Purification of chemical industry raw material gas and treatment of tail gas from conventional sulfur recovery equipment, etc.
Can be used effectively over a wide range

[Brief explanation of drawings]

Figure 1 shows the results of measuring the combustibility of hydrocarbons, H2, CO, etc., where the vertical axis is the conversion rate (%) of each, the horizontal axis is the temperature (1), the O mark is CH4, and the Δ mark is C4. Hydrocarbons, black marks indicate H2, and 0 marks indicate CO (corresponding to Example 3). Figure 2 is a diagram showing the relationship between reaction temperature and H2S conversion rate when a catalyst with an atomic ratio of Sb/(Sb+Bi) of 0°5 is used, and the vertical axis is the H2S conversion rate (%). The horizontal axis indicates temperature (°C) (corresponding to Example 4). FIG. 3 is a diagram showing the relationship between reaction temperature and outlet SO2, and the vertical axis shows the SOz concentration (ppm) at the reactor outlet (corresponding to Example 4). FIG. 1 shows a process flow sheet for treating low concentration hydrogen sulfide-containing gas such as till gas in a Claus method sulfur recovery device. Applicant JGC Co., Ltd. Company Agent
Patent Attorney Masaji Aoma 200 250 “JOO350400” C No. 1

Claims (1)

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