Selective reduction catalysts for sulfur production from sulfur dioxide and their application methods

Abstract

This invention belongs to the field of catalyst technology, specifically relating to a selective reduction catalyst for the production of sulfur from sulfur dioxide and its application method. The selective reduction catalyst for sulfur production from sulfur dioxide contains 1-2 wt% cobalt (CoO), 4-10 wt% molybdenum (MoO3), and 2-4 wt% zinc (ZnO), with TiO2-Al2O3 as the support. This invention exhibits good wide-temperature reaction performance, heat resistance, and water vapor resistance; the single-pass yield of elemental sulfur is higher than 80%, and the reaction process has high efficiency, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a selective reduction catalyst for producing sulfur from sulfur dioxide and its application method. Background Technology

[0002] Sulfur dioxide is a major air pollutant. With the improvement of treatment technology, capturing and utilizing most of the sulfur dioxide in exhaust gas is an inevitable choice for many industries, such as various non-ferrous metal smelting enterprises. Generally, it is made into sulfuric acid for self-use and / or for sale. However, the sale and transportation of sulfuric acid is not easy in many cases, and is greatly restricted by geographical location and transportation conditions. It is necessary to convert this part of sulfur dioxide into other easily marketable or harmless sulfur-containing substances.

[0003] Many non-ferrous metal smelting concentrates contain sulfides as their active ingredient. These concentrates are roasted in an aerobic environment, such as in a rotary kiln, to convert the sulfides into oxides for further processing and utilization. The flue gas emitted from the roasting furnace typically contains 0.1-15% SO2. Currently, this flue gas is generally treated first by cooling and dust removal, and then absorbed by a circulating working fluid (lean solution) with alkaline organic amines as the main component at a low temperature, such as 30-42℃, until the SO2 content is below 100 mg / Nm³. 3 Even below 50 mg / Nm 3 Then, the SO2 is discharged in compliance with emission standards; the circulating working fluid (rich fluid) that absorbs SO2 is then treated by steam at a pressure of 0.35 MPa to release a high-concentration sulfur dioxide gas stream containing saturated water vapor (SO2 content 99.9%, dry basis); among these sulfur dioxide capture processes, the Cansolv process or its modified version is the most widely used.

[0004] The sulfur dioxide gas stream containing saturated water vapor obtained by the Cansolv process or its improved process can be used to produce sulfur through a Claus unit. Two-thirds of the sulfur dioxide gas stream needs to be converted into hydrogen sulfide gas stream by hydrogen reduction, and then mixed with the remaining one-third of the sulfur dioxide gas stream stream before being used to produce sulfur through the Claus process. This method has a relatively long and immature process, is not technically reasonable, and has low development and utilization value.

[0005] The high-concentration sulfur dioxide gas stream containing water vapor obtained by the Cansolv process or its modified process may be a reasonable option for directly producing sulfur through a hydrogen selective reduction process, but so far there is no publicly available information on specific research and development and application.

[0006] In existing technologies, the selective conversion of sulfur dioxide in a low-concentration gas stream containing 0.2-0.8 v% SO2 into elemental sulfur via hydrogenation is a known process. For example, selective reduction of Claus tail gas streams containing approximately 0.5-1 v% H2S and 0.2-0.8 v% SO2 under reaction conditions such as cobalt-molybdenum catalysts and 180-250℃ with approximately 1.5-4 v% H2, effectively converting the sulfur dioxide into elemental sulfur, is widely used and yields good results. However, in this reaction, the contents of SO2 and H2 are both low, the water vapor content is below 30 v%, and the adiabatic temperature rise is below 50℃.

[0007] Chinese patent CN101745399A discloses several catalysts for selective reduction sulfur recovery. Example 1 describes the preparation process of a cobalt-molybdenum / titanium oxide catalyst: titanium tetrachloride is hydrolyzed to obtain a suspension, which is then washed, filtered, and dried. The resulting TiO2 dry powder is thoroughly mixed with carboxymethyl cellulose and water, extruded, and the extruded strips are dried and calcined at 450°C for 4 hours to obtain support 1 (specific surface area 135 m²). 2 / g, pore volume 0.32mL / g); then, a multiple impregnation method was used, impregnating 180g of carrier 1 with 150mL of impregnation solution prepared by dissolving 29g of ammonium heptamolybdate and 28g of cobalt nitrate in 25% ammonia water and 1.4ml of ethylenediamine. After impregnation, the residual liquid was discarded, and the sample was naturally dried at room temperature for 24 hours, then dried at 110℃ for 24 hours, and calcined at 500℃ for 4 hours to obtain catalyst sample A. Example 14 also disclosed the microreactor evaluation method and effect of the prepared catalyst: 5ml of catalyst sample pulverized to 20-40 mesh was filled into a stainless steel tubular reactor with an inner diameter of 5mm. Quartz sand of the same particle size was filled on the top of the catalyst for mixing and preheating. The reactor was heated by electricity. The hydrogenation activity of the catalyst was investigated using SO2 + H2 = S + H2O and SO2 + 3H2 → H2S + 2H2O as index reactions. The inlet gas composition was: H2S 1%, SO2 1%, H2O 30%, with the remainder being N2, and the gas hourly space velocity was 5000 h⁻¹. -1 The reaction temperature was 160-300℃. The initial activity evaluation results specifically included: For the cobalt-molybdenum / titanium oxide catalyst A in Example 1, the SO2 conversion and elemental sulfur yield were both 95% at a reaction temperature of 160℃, and the elemental sulfur selectivity was 100%; the SO2 conversion was 100% at reaction temperatures above 180℃, with elemental sulfur selectivity and yield both being 100% at 180℃ and 200℃, decreasing to 45% at 220℃, and no elemental sulfur being generated above 260℃ (only H2S was generated).

[0008] A high-concentration sulfur dioxide gas stream containing saturated water vapor, obtained from the Cansolv process or its modified version, is directly converted into elemental sulfur via selective hydrogen reduction. The sulfur is then cooled and condensed in stages, separating liquid sulfur and condensate. The gas stream separating the liquid sulfur and condensate (which may contain water vapor and small amounts of SO2, H2S, and byproducts such as COS and CO2 when the feed hydrogen contains small amounts of CO and CH4) is entirely or mostly returned to the gas stream mixer before the reactor for recycling. The separated liquid sulfur is further used to produce sulfur. The advantages of this process are… The reaction is relatively simple and the process is short. The products other than sulfur are water or mainly water. When using high-purity hydrogen, almost no tail gas is produced. When using hydrogen with a purity of 96% or higher, the amount of tail gas produced is also very small, meaning the tail gas treatment burden is relatively light. Therefore, this process is competitive in terms of economy. One feature of this reaction is that the reaction releases a large amount of heat and the adiabatic temperature rise is high. Under the gas flow conditions of 200-300℃, the adiabatic temperature rise of each 1v% SO2 reacting with 2v% H2 to produce elemental sulfur and 2v% water vapor is above 40℃. Therefore, in the reaction of producing sulfur from sulfur dioxide gas containing water vapor and the required amount of hydrogen through selective reduction, the catalyst and reactor are key, and the following characteristics and requirements are required in terms of engineering economy to reduce the scale and investment of heating equipment: (a) the pressure of the sulfur dioxide gas flow is only slightly higher than atmospheric pressure, the temperature should not be lower than 60°C, and the water vapor partial pressure is 20-35 kPa; (b) the inlet gas flow of the catalytic reactor should have the lowest possible temperature and the SO2 content should be appropriately high; (c) the gas flow of the separated liquid sulfur and condensate after the reaction is recycled and used as reaction dilution gas. When reused, the temperature and water vapor partial pressure should be appropriately balanced, that is, the temperature should be appropriately high and the water vapor partial pressure should be appropriately low. Therefore, the technical requirements for the catalyst in this process include: (1) It needs to have sufficiently high and stable reaction performance under a wide range of water vapor content of 15-60v%, so as to use a higher temperature such as 60-70℃ for sulfur dioxide feed gas flow and recycled gas flow (the water vapor saturation partial pressure at 60℃ is 19.9kPa and the water vapor saturation partial pressure at 70℃ is 31.2kPa), and be able to convert a higher SO2 content such as 5-15v% in a single pass, so as to have a higher reaction process efficiency; (2) The catalyst has good wide-temperature reaction performance and heat resistance to reduce the temperature control requirements of the reactor. It has good low-temperature reaction performance, and the reactor can use a lower inlet gas flow temperature such as below 200℃ to raise the temperature of the gas flow and catalyst bed in the reaction inlet section. It can also obtain a higher sulfur dioxide conversion rate and elemental sulfur selectivity in the middle and outlet sections of the catalyst bed under a suitable higher temperature such as 280-320℃, that is, obtain a suitable higher single-pass yield of elemental sulfur such as more than 80%; (3) It has sufficiently stable reaction performance.

[0009] However, among the various catalysts available or that can be prepared in the existing technology for the selective reduction of sulfur dioxide to elemental sulfur using hydrogen, it is not yet possible to select a catalyst that can simultaneously meet the above technical requirements. Summary of the Invention

[0010] The purpose of this invention is to provide a selective reduction catalyst for the production of sulfur from sulfur dioxide, which has good wide-temperature reaction performance, heat resistance, and water vapor resistance. The single-pass yield of elemental sulfur is higher than 80%, and the reaction process has high efficiency and good application prospects. This invention also provides a method for applying the selective reduction catalyst for the production of sulfur from sulfur dioxide.

[0011] The selective reduction catalyst for producing sulfur from sulfur dioxide described in this invention contains 1-2 wt% cobalt (based on CoO), 4-10 wt% molybdenum (based on MoO3), and 2-4 wt% zinc (based on ZnO), with TiO2-Al2O3 as the support; it is prepared through the following steps:

[0012] (A) The dry powder of metatitanic acid was calcined at 550-570℃ for 3-5 hours to obtain TiO2 powder; the dry powder of boehmite was calcined at 750-800℃ for 3-5 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill to obtain TiO2-Al2O3 mixed powder;

[0013] (B) In a kneader, add metatitanic acid powder and pseudoboehmite powder, mix evenly to obtain powder; spray acetic acid aqueous solution into the powder through an atomizing nozzle, continue mixing after the acetic acid aqueous solution is added, stop mixing and cover and seal; then add zinc compound powder, TiO2-Al2O3 mixed powder from step (A) and organic pore-forming agent powder, mix evenly, spray water through an atomizing nozzle, knead until the material is uniform, then discharge, extrude, granulate, dry, and calcine under air conditions to obtain a TiO2-Al2O3 carrier containing ZnO;

[0014] (C) In the spray drum, the TiO2-Al2O3 support containing ZnO obtained in step (B) is added, and the cobalt-molybdenum ammonia solution is sprayed into it through the atomizing nozzle. After the cobalt-molybdenum ammonia solution is sprayed, it is placed in a sealed container for homogenization treatment, then discharged, dried, and calcined to obtain a selective reduction catalyst for the production of sulfur from sulfur dioxide.

[0015] In step (A), the weight ratio of TiO2 powder to Al2O3 powder is 1:(2-3), the fineness of both metatitanic acid dry powder and pseudoboehmite dry powder is -600 mesh, and the fineness of TiO2-Al2O3 mixed powder is -200 mesh.

[0016] In step (B), the concentration of the acetic acid aqueous solution is 18-30 wt%, and the weight ratio of pseudoboehmite dry powder to acetic acid aqueous solution is 1:(0.5-0.8); the mixing time is 40-60 min, and the standing time is 15-20 h; the calcination temperature is 450-480℃, and the calcination time is 2-4 h; the zinc compound dry powder is zinc hydroxide dry powder or basic zinc carbonate dry powder; the organic pore-forming agent powder is made by mixing guar gum powder and polyacrylamide in a weight ratio of 1:(2-4), and the molecular weight of polyacrylamide is 10 million-20 million; the organic pore-forming agent powder is burned off during the calcination process at 450-480℃ and in air.

[0017] In step (B), the weight ratio of the total amount of water contained in the metatitanic acid powder, pseudoboehmite powder, zinc compound powder, TiO2-Al2O3 mixed powder, organic pore-forming agent powder, and acetic acid aqueous solution, plus the injected water, is (20-30):(15-25):(2-5):(45-65):(2-4):(95-140), where the metatitanic acid powder is calculated as TiO2, the pseudoboehmite powder as Al2O3, and the zinc compound powder as... The dry powder is calculated as ZnO; the fineness of the metatitanic acid dry powder and the pseudoboehmite dry powder is -600 mesh, and the fineness of the zinc compound dry powder is -200 mesh (which can be observed through an optical microscope) to obtain uniform mixing; the shape of the ZnO-containing TiO2-Al2O3 support is one of cylindrical, clover-shaped or tetraclover-shaped, and the equivalent external dimensions of the ZnO-containing TiO2-Al2O3 support are Φ(2.5-4)×(3-8)mm.

[0018] The parameters of the metatitanic acid powder in both steps (A) and (B) are: SO4 2- With a content ≤0.5%, after calcination at 450℃, it has a purity ≥130m 2 The specific surface area is ≥0.25 mL / g and the pore volume is ≥0.25 mL / g; metatitanic acid dry powder is prepared by the following method: using SO4 2- Using industrial metatitanic acid produced by the sulfuric acid process with a content of 1.5-5 wt% (on a dry basis) and an average particle size (outer diameter, the same below) ≤1 μm as raw material, the mixture is pulped with a washing solution containing 1-3 wt% ammonia for 3-10 hours. The pulp is filtered, washed with water, dried, and pulverized to obtain metatitanic acid dry powder. In steps (A) and (B), the pseudoboehmite dry powder is calcined at 450℃ and has a particle size of 300-350 μm. 2 The specific surface area is 0.75-0.9 mL / g and the pore volume is 0.75-0.9 mL / g. Among the indicators of the metatitanic acid powder and pseudoboehmite powder, the specific surface area and pore volume were determined by low-temperature nitrogen adsorption method.

[0019] In step (C), the amount of cobalt-molybdenum ammonia solution added is 95-100% of the saturated water absorption volume of the ZnO-containing TiO2-Al2O3 support; the cobalt-molybdenum ammonia solution is prepared from raw materials, including ammonium molybdate, cobalt nitrate and ammonia, wherein the ammonium molybdate is heptamolybdate or tetramolybdate, the concentration of ammonia is 15-20 wt%, the concentration of ammonium molybdate in the cobalt-molybdenum ammonia solution is 143-316 g / L, and the concentration of cobalt nitrate in the cobalt-molybdenum ammonia solution is 78-166 g / L.

[0020] The raw materials also include ethylenediamine. The concentration of ethylenediamine in the cobalt-molybdenum ammonia solution is 6-10 g / L. Ethylenediamine is added to the cobalt-molybdenum ammonia solution to improve the distribution of cobalt and molybdenum.

[0021] In step (C), the homogenization time is 10-15 h, the calcination temperature is 450-480 ℃, and the calcination time is 2-4 h.

[0022] The selective reduction catalyst for sulfur production from sulfur dioxide described in this invention is applied by mixing a sulfur dioxide gas stream, a hydrogen gas stream, and a dilution gas stream to obtain a mixed gas stream. The mixed gas stream is preheated to 160-180°C and reacted in a fixed-bed reactor or multiple fixed-bed reactors connected in series with the selective reduction catalyst for sulfur production from sulfur dioxide to obtain elemental sulfur, hydrogen sulfide, and water vapor. Each fixed-bed reactor is provided with one or more catalyst beds.

[0023] The total volumetric flow rate of hydrogen gas is 1.9-2.1 times that of sulfur dioxide gas. The maximum temperature of each catalyst bed is controlled at 220-320℃. Hydrogen gas is added to the process gas flow between catalyst beds and / or between fixed-bed reactors. In the inlet gas flow of each catalyst bed, the volume ratio of SO2 to H2 is 1:(0.5-1), and the H2 content is 6-10 v%. The gas hourly space velocity of each catalyst bed is 500-6000 h⁻¹. -1 The dilution gas stream contains water vapor and / or N2, and the upper limit of water vapor content in the outlet gas stream of the fixed bed reactor is 60 v% (volume percentage).

[0024] The principle of this invention is as follows:

[0025] (1) A portion of the TiO2 and Al2O3 contained in the catalyst were obtained and introduced in step (A) by calcining metatitanic acid powder at 550-570℃ and pseudoboehmite powder at 750-800℃, respectively. The remaining TiO2 and Al2O3 were obtained and introduced in step (B) by calcining metatitanic acid powder, pseudoboehmite powder and their acetic acid gel at 450-480℃, respectively, and have different surface properties such as acidity. The CoO and MoO3 loaded and introduced in step (C) are distributed in the pores and on the surface of the TiO2 and Al2O3 particles, wherein the distribution is... The CoO and MoO3 (sulfided state) on the inner and outer surfaces of TiO2 and Al2O3 particles calcined at 450-480℃ exhibit stable reactivity under the reaction conditions, such as the lower temperature range of 160-250℃ and the water vapor content range of 30-50v%. The CoO and MoO3 (sulfided state) on the inner and outer surfaces of TiO2 particles calcined at 550-570℃ and Al2O3 particles calcined at 750-800℃ exhibit stable reactivity under the reaction conditions, such as the higher temperature range of 230-320℃ and the water vapor content range of 40-60v%.

[0026] (2) The zinc hydroxide powder or basic zinc carbonate powder added during the mixing of materials in step (B) generates zinc oxide during the calcination of the support; the zinc oxide is dissolved by ammonia water during the impregnation of cobalt-molybdenum ammonia solution in step (C), and forms highly dispersed and uniformly distributed ZnO during the subsequent drying and calcination at 450-480℃, and is mixed with highly dispersed CoO and MoO3; ZnO, CoO, MoO3 or their sulfide products in the catalyst are bound to the support components TiO2 and Al2O3 to a certain extent. The stability of ZnO sulfide products is much higher than that of CoO sulfide products and MoO3 sulfide products, which plays a role in modifying the inner surface of the TiO2-Al2O3 support, and also improves the dispersion state of CoO, MoO3 and their sulfide products and the binding state with the support components. Thus, without reducing the wide-temperature reaction effect of the catalyst, the reaction performance stability of the catalyst under high water vapor content conditions is significantly improved. In addition, if the catalyst is prepared by impregnation with a zinc-containing solution, such as impregnating a cobalt-molybdenum-zinc ammonia solution, it is difficult to achieve the high cobalt-molybdenum-zinc loading of the present invention because the water absorption rate or pore volume of the support is not high enough.

[0027] (3) In the process of material mixing in step (B), the first added titanium dioxide powder and pseudoboehmite powder are mixed evenly, and then an acetic acid aqueous solution with a concentration of 18-30wt% is sprayed in through an atomizing nozzle. Since the amount of acetic acid aqueous solution is small, the fluidity of the powder is very good during the mixing process and after being covered and sealed for 15-20 hours. However, aluminum glue, which is the main adhesive component of the carrier, is generated. It can be basically mixed with other powders added later. During the process of spraying water and kneading, the material blocks can be gradually kneaded evenly and are suitable for extrusion. Among the organic pore-forming agents used, polyacrylamide with a molecular weight of 10 million to 20 million is used. It has a certain effect on the formation of mesopores and macropores in the carrier and has the functions of bonding, lubrication and pore-forming. Guarantee powder mainly plays a lubricating role.

[0028] (4) In the inlet gas flow of each catalyst bed, the purpose of controlling the volume ratio of SO2 to H2 to 1:(0.5-1) is to control the intensity of the reaction and the temperature rise. The purpose of controlling the H2 content to 6-10v% is to avoid irreversible reduction of the active components (it is generally believed that the H2 content is 12v% as the upper limit).

[0029] The beneficial effects of this invention are as follows:

[0030] The catalyst of this invention exhibits good wide-temperature reaction performance, heat resistance, and water vapor resistance in the selective reduction reaction of sulfur from sulfur dioxide and hydrogen. It maintains high and stable reaction performance under conditions of relatively low inlet gas flow temperature of 160-180℃, maximum bed temperature of 280-320℃, and water vapor content as high as 60v%, with a single-pass yield of elemental sulfur exceeding 80% and high reaction efficiency. The catalyst shows promising application prospects in the reaction of sulfur from sulfur dioxide and hydrogen. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the sulfur recovery catalyst evaluation device;

[0032] In the diagram: 1. Tubular stainless steel reactor; 2. Two-stage electric heating furnace; 3. Sulfur collection cylinder; 4. First-stage catalyst loading and unloading pipe; 5. Thermocouple sheath; 6. Second-stage gas supply pipe; 7. N2 inlet pipe; 8. H2 inlet pipe; 9. SO2 inlet pipe; 10. Gas mixer; 11. Deionized water storage bottle; 12. Horizontal flow pump; 13. Water vaporizer; 14. Refrigerator; 15. Water vapor condenser separator; 16. Dryer; 17. Gas chromatograph; 18. Desulfurization tank. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments.

[0034] Example 1

[0035] The selective reduction catalyst for sulfur production from sulfur dioxide is prepared through the following steps:

[0036] (A) Prepare metatitanic acid dry powder (-600 mesh, SO4) 2- With a content of 0.21 wt%, after calcination at 450℃ for 3 hours, it has a content of 146 m 2 TiO2 powder was obtained by calcining (specific surface area of ​​0.29 mL / g and pore volume of 0.29 mL / g) at 560℃ for 4 h; pseudoboehmite dry powder (-600 mesh, after calcination at 450℃ for 3 h, has a specific surface area of ​​335 μm / g and a pore volume of 0.29 mL / g) was further obtained by calcination at 560℃ for 4 h. 2 The TiO2 powder was calcined at 775℃ for 4 hours with a specific surface area of ​​0.84 mL / g and a pore volume of 0.84 mL / g to obtain Al2O3 powder. The obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill at a weight ratio of 1:2 to obtain TiO2-Al2O3 mixed powder of -200 mesh.

[0037] (B) Add metatitanic acid dry powder (-600 mesh, SO4) to a small kneader. 2- With a content of 0.21 wt%, after calcination at 450℃ for 3 hours, it has a content of 146 m 2 The specific surface area ( / g) and pore volume (0.29mL / g) of pseudoboehmite dry powder (-600 mesh, after calcination at 450℃ for 3h, it has 335m) 2 The specific surface area (g) and pore volume (0.84 mL / g) were mixed evenly to obtain a powder. A 25 wt% acetic acid aqueous solution was sprayed into the powder through an atomizing nozzle. The weight ratio of the pseudoboehmite dry powder to the acetic acid aqueous solution was 1:0.65. After the acetic acid aqueous solution was added, mixing continued for 60 min. Mixing was stopped, and the mixture was covered and sealed for 15 h to obtain a powder with good flowability. Basic zinc carbonate dry powder (-200 mesh), the TiO2-Al2O3 mixed powder from step (A), and the organic pore-forming agent powder were then added and mixed evenly. Water was sprayed into the mixture through an atomizing nozzle, and the mixture was kneaded until the material was uniform. The mixture was then discharged, extruded, and granulated, and dried at 120℃ for 10 minutes. h, calcined at 465℃ and in air for 3h, to obtain a clover-shaped TiO2-Al2O3 carrier containing ZnO with equivalent external dimensions of Φ(3.1-3.2)×(4-6)mm; the total amount of water contained in the acetic acid aqueous solution and the injected water added to the mixed powder of TiO2-Al2O3, the organic pore-forming agent powder, and the acetic acid aqueous solution were 2.5kg, 2kg, 0.22kg, 5.5kg, 0.3kg, and 12kg, respectively, where the amount of the mixed powder of TiO2, the amount of the mixed powder of boehmite, the amount of the basic zinc carbonate, and the amount of the basic zinc carbonate were ZnO.

[0038] (C) In a small spray drum, 5000g of TiO2-Al2O3 support containing ZnO obtained in step (B) (with a saturated water absorption rate of 0.55mL / g) was added. 2613mL of cobalt-molybdenum ammonia solution was sprayed through an atomizing nozzle for 26min. After spraying, the drum continued to rotate for 8min until the support surface dried. Then the drum was stopped and placed in a sealed container for homogenization treatment for 12h. The material was discharged, dried at 120℃ for 6h, and calcined at 465℃ for 3h to obtain a selective reduction catalyst for sulfur production from sulfur dioxide.

[0039] In steps (A) and (B), the metatitanic acid powder is prepared by the following method: using SO4 2- Using wet metatitanic acid from the sulfuric acid process with a content of 3.7 wt% (on a dry basis) and an average particle size of 0.65 μm as raw material, a washing solution (aqueous solution) containing 2 wt% ammonia was added at a weight ratio of 1:3 and the mixture was pulped for 8 hours. The pulp was then filtered, washed with water, dried, and pulverized to obtain dry metatitanic acid powder.

[0040] In step (B), the organic pore-forming agent powder is made by mixing guar gum powder (-600 mesh) and polyacrylamide (-200 mesh, molecular weight 12 million) in a weight ratio of 1:3.

[0041] The cobalt-molybdenum ammonia solution in step (C) is prepared by the following method: 143.4 g of ammonium tetramolybdate and 78.4 g of cobalt nitrate are added to a 1000 mL volumetric flask, and then ammonia water (concentration of 15 wt%) is added to a total volume of 850 mL. The mixture is shaken until completely dissolved, and then ammonia water is added again to a total volume of 1000 mL. The mixture is shaken well and left to stand for 15 h to obtain the cobalt-molybdenum ammonia solution. This solution is prepared in multiple batches for use.

[0042] The selective reduction catalyst for sulfur production from sulfur dioxide contains 1 wt% cobalt (CoO), 4 wt% molybdenum (MoO3), and 2 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.51 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 193 m² / g. 2 / g and 0.42mL / g indicate that the volume of macropores in the catalyst is above 0.09mL / g.

[0043] Example 2

[0044] The selective reduction catalyst for the production of sulfur from sulfur dioxide in Example 2 was prepared by basically following steps (A)-(C) of Example 1, with the main difference being:

[0045] In step (B), the amount of basic zinc carbonate dry powder, calculated as ZnO, is changed to 0.34 kg;

[0046] The cobalt-molybdenum ammonia solution in step (C) is prepared by the following method: 302.9 g of ammonium tetramolybdate and 165.6 g of cobalt nitrate are added to a 1000 mL volumetric flask, then ammonia water (concentration of 18 wt%) is added to a total volume of 900 mL, 8 g of ethylenediamine is added, and the mixture is shaken until a solution is formed. Ammonia water is added to a total volume of 1000 mL, the mixture is shaken well, and the solution is left to stand for 15 h to obtain the cobalt-molybdenum ammonia solution, which can be prepared multiple times for use.

[0047] The selective reduction catalyst for sulfur production from sulfur dioxide contains 2 wt% cobalt (CoO), 8 wt% molybdenum (MoO3), and 3 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.46 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 170 m² / g. 2 / g and 0.37mL / g indicate that the volume of macropores in the catalyst is above 0.08mL / g.

[0048] Example 3

[0049] The selective reduction catalyst for the production of sulfur from sulfur dioxide in Example 3 was prepared by basically following steps (A)-(C) of Example 1, with the main difference being:

[0050] In step (A), the obtained TiO2 powder and Al2O3 powder are mixed and ball-milled in a ball mill at a weight ratio of 1:3 to obtain a TiO2-Al2O3 mixed powder of -200 mesh.

[0051] In step (B), the amounts of basic zinc carbonate dry powder (calculated as ZnO), organic pore-forming agent powder, water contained in acetic acid aqueous solution, and sprayed water are changed to 0.47 kg, 0.40 kg, and 13.5 kg, respectively.

[0052] In step (C), the saturated water absorption rate of the TiO2-Al2O3 support containing ZnO was measured to be 0.64 mL / g. 100% of the saturated water absorption volume of the support was sprayed into a cobalt-molybdenum ammonia solution. The cobalt-molybdenum ammonia solution was prepared as follows: 315.9 g of ammonium tetramolybdate and 138.2 g of cobalt nitrate were added to a 1000 mL volumetric flask, followed by the addition of ammonia water (concentration of 20 wt%) to a total volume of 950 mL. 10 g of ethylenediamine was added, and the mixture was shaken until a solution was formed. Ammonia water was added to a total solution volume of 1000 mL, and the mixture was shaken well and allowed to stand for 15 h to obtain the cobalt-molybdenum ammonia solution, which was prepared multiple times for use.

[0053] The selective reduction catalyst for sulfur production from sulfur dioxide contains 2 wt% cobalt (CoO), 10 wt% molybdenum (MoO3), and 4 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.51 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 155 m² / g. 2 / g and 0.43mL / g indicate that the volume of macropores in the catalyst is above 0.08mL / g.

[0054] Example 4

[0055] The selective reduction catalyst for the production of sulfur from sulfur dioxide in Example 4 was prepared by basically following steps (A)-(C) of Example 1, with the main difference being:

[0056] In step (A), the metatitanic acid powder was calcined at 570℃ for 3 hours to obtain TiO2 powder; the pseudoboehmite powder was calcined at 800℃ for 3 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder were mixed and ball-milled in a ball mill at a weight ratio of 1:3 to obtain a TiO2-Al2O3 mixed powder of -200 mesh.

[0057] In step (B), the amounts of basic zinc carbonate dry powder (calculated as ZnO), organic pore-forming agent powder, water contained in acetic acid aqueous solution, and sprayed water are changed to 0.34 kg, 0.40 kg, and 13 kg, respectively.

[0058] In step (C), the saturated water absorption rate of the TiO2-Al2O3 support containing ZnO was measured to be 0.62 mL / g. 95% of the saturated water absorption volume of the support was sprayed into a cobalt-molybdenum ammonia solution. The cobalt-molybdenum ammonia solution was prepared by the following method: 237.0 g of ammonium tetramolybdate and 108.9 g of cobalt nitrate were added to a 1000 mL volumetric flask, and ammonia water (concentration of 15 wt%) was added to a total volume of 900 mL. 6 g of ethylenediamine was added, and the mixture was shaken until a solution was formed. Ammonia water was added to a total solution volume of 1000 mL, and the mixture was shaken well and allowed to stand for 10 h to obtain the cobalt-molybdenum ammonia solution, which was prepared multiple times for use.

[0059] The selective reduction catalyst for sulfur production from sulfur dioxide contains 1.5 wt% cobalt (CoO), 7.5 wt% molybdenum (MoO3), and 3 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.53 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 179 m² / g. 2 / g and 0.42mL / g indicate that the volume of macropores in the catalyst is above 0.11mL / g.

[0060] Example 5

[0061] The selective reduction catalyst for the production of sulfur from sulfur dioxide in Example 5 was prepared by basically following steps (A)-(C) of Example 4, with the main difference being:

[0062] In step (A), the metatitanic acid powder is calcined at 550℃ for 5 hours to obtain TiO2 powder; the pseudoboehmite powder is calcined at 750℃ for 5 hours to obtain Al2O3 powder; the obtained TiO2 powder and Al2O3 powder are mixed and ball-milled in a ball mill at a weight ratio of 1:2 to obtain a TiO2-Al2O3 mixed powder of -200 mesh.

[0063] In step (B), the total amount of water contained in the metatitanic acid dry powder, pseudoboehmite dry powder, basic zinc carbonate dry powder, TiO2-Al2O3 mixed powder, organic pore-forming agent powder, and acetic acid aqueous solution and sprayed water added are 2 kg, 2.5 kg, 0.34 kg, 5.5 kg, 0.4 kg, and 14 kg, respectively. Among them, the metatitanic acid dry powder is calculated as TiO2, the pseudoboehmite dry powder is calculated as Al2O3, and the basic zinc carbonate dry powder is calculated as ZnO.

[0064] In step (C), the saturated water absorption rate of the TiO2-Al2O3 support containing ZnO was measured to be 0.58 mL / g. 95% of the saturated water absorption volume of the support was sprayed into a cobalt-molybdenum ammonia solution. The cobalt-molybdenum ammonia solution was prepared by the following method: 253.3 g of ammonium tetramolybdate and 116.4 g of cobalt nitrate were added to a 1000 mL volumetric flask, ammonia water (concentration of 18 wt%) was added to a total volume of 900 mL, 8 g of ethylenediamine was added, and the mixture was shaken until a solution was formed. Ammonia water was added to a total solution volume of 1000 mL, the mixture was shaken well, and the solution was left to stand for 10 h to obtain the cobalt-molybdenum ammonia solution, which was prepared multiple times for use.

[0065] The selective reduction catalyst for sulfur production from sulfur dioxide contains 1.5 wt% cobalt (CoO), 7.5 wt% molybdenum (MoO3), and 3 wt% zinc (ZnO). The catalyst has a saturated water absorption rate of 0.49 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 161 m² / g. 2 / g and 0.40mL / g indicate that the volume of macropores in the catalyst is above 0.09mL / g.

[0066] Comparative Example 1

[0067] The catalyst of Comparative Example 1 was prepared by basically following steps (A)-(C) of Example 5, the main difference being that: in step (B), basic zinc carbonate dry powder was not added.

[0068] Comparative Example 2

[0069] The catalyst of Comparative Example 2 was prepared by basically following steps (B)-(C) of Example 5, the main difference being that TiO2-Al2O3 mixed powder was not used. The specific steps are as follows:

[0070] (1) In a small kneader, add metatitanic acid powder and pseudoboehmite powder, mix evenly to obtain powder; spray 1.95 kg of acetic acid aqueous solution with a concentration of 25 wt% into the powder through an atomizing nozzle. After the acetic acid aqueous solution is added, continue mixing for 60 min, stop mixing and cover and seal for 15 h to obtain powder with good flowability; then add basic zinc carbonate powder (-200 mesh) and organic pore-forming agent powder, mix evenly, spray water through an atomizing nozzle, knead until the material blocks are uniform, discharge, extrude, and granulate, dry at 120℃ for 10 h, and then dry at 465℃ in air. Under the given conditions, a clover-shaped TiO2-Al2O3 carrier containing ZnO with an equivalent external size of Φ(2.8-3.0)×(4-6)mm was obtained after calcination for 3 hours. The total amount of water contained in the metatitanic acid powder, pseudoboehmite powder, basic zinc carbonate powder, organic pore-forming agent powder, and acetic acid aqueous solution, as well as the amount of water injected, were 3.8kg, 6.2kg, 0.34kg, 0.4kg, and 12.8kg, respectively. Among them, the metatitanic acid powder was calculated as TiO2, the pseudoboehmite powder as Al2O3, and the basic zinc carbonate powder as ZnO.

[0071] (2) In a small spray drum, 5000g of TiO2-Al2O3 support containing ZnO obtained in step (B) (with a saturated water absorption rate of 0.62mL / g) was added. 2945mL of cobalt-molybdenum ammonia solution (accounting for 95% of the saturated water absorption volume of the support) was sprayed into the drum through an atomizing nozzle. The spraying time was 26min. After the spraying was completed, the drum continued to rotate for 8min until the surface of the support dried. Then the drum was stopped and placed in a sealed container for homogenization treatment for 12h. The material was discharged, dried at 120℃ for 6h, and calcined at 450℃ for 3h to obtain the catalyst.

[0072] In step (2), the cobalt-molybdenum ammonia solution is prepared by the following method: 237.0g of ammonium tetramolybdate and 108.9g of cobalt nitrate are added to a 1000mL volumetric flask, ammonia water (concentration of 15wt%) is added to a total volume of 900mL, 8g of ethylenediamine is added, and the mixture is shaken until a solution is formed. Ammonia water is added to a total volume of 1000mL, the mixture is shaken well, and the solution is left to stand for 10h to obtain the cobalt-molybdenum ammonia solution, which is then prepared multiple times for use.

[0073] The catalyst contains 1.5 wt% cobalt (CoO), 7.5 wt% molybdenum (MoO3), and 3 wt% zinc (ZnO). Its saturated water absorption rate is 0.48 mL / g, and its specific surface area and pore volume, determined by low-temperature nitrogen adsorption, are 168 m² / g. 2 / g, 0.45mL / g.

[0074] Evaluation Example 1

[0075] like Figure 1As shown, the sulfur recovery catalyst evaluation device used in Example 1 employs a tubular stainless steel reactor 1 with two reaction sections. The tubular stainless steel reactor 1 is vertically installed in a two-stage electric heating furnace 2. The upper section (first stage) of the tubular stainless steel reactor 1 is a low-temperature reaction section (a quartz sand preheating section is provided above the first stage catalyst bed), and the lower section (second stage) is a high-temperature reaction section (a gas mixing space is left above the second stage catalyst bed). Both reaction sections are respectively equipped with tightly nested brass homogenizing sleeves (between the upper and lower homogenizing sleeves). (Each heat-spreading sleeve is composed of two semi-cylindrical cylinders joined together.) The upper and lower sections of the brass heat-spreading sleeves are also in close contact with the upper and lower sections of the electric heating sleeves of the two-stage electric heating furnace 2 (the upper and lower sections of the electric heating sleeves are also not in contact, and each electric heating sleeve is also composed of two silicon carbide semi-cylindrical cylinders with internal and external insulating heating wires joined together.) Through the temperature control of the upper and lower sections of the electric heating sleeves of the two-stage electric heating furnace 2, the maximum temperature of the upper and lower sections of the catalyst bed in the tubular stainless steel reactor 1 can be basically controlled to the required level. The specific structure of the tubular stainless steel reactor 1 includes: a catalyst loading and unloading pipe 4 at the upper end, two gas supply pipes 6 on the middle side wall, which also serve as catalyst loading and unloading pipes; a sulfur collection cylinder 3 connected at the lower end (which condenses and collects elemental sulfur by cooling through heat dissipation from the outer wall); and a thermocouple sheath 5 (the central axis of the thermocouple sheath coincides with the central axis of the reactor) extending downwards from the top of the tubular stainless steel reactor 1, through a quartz sand preheating section, a first catalyst bed (i.e., a first low-temperature reaction bed), to a second catalyst bed (i.e., a second high-temperature reaction bed). The thermocouple sheath 5 contains multiple K-type armored thermocouples (the thermocouples that measure the highest temperature of the first bed can move vertically within the height range of the bed, while the other thermocouples are fixed in the vertical position).

[0076] The air intake method of the tubular stainless steel reactor 1 is as follows: the air intake of the first low-temperature reaction bed is a mixed gas flow containing SO2, H2, N2 and water vapor. The water vapor is generated and introduced from deionized water in deionized water storage bottle 11 by a horizontal flow pump 12 and in water vaporizer 13 (i.e., water vapor generator). (The upper part of the tubular stainless steel reactor 1, which is not covered by the two-stage electric heating furnace 2, and the water vapor connecting pipe between water vaporizer 13 and tubular stainless steel reactor 1 are all equipped with an external heat insulation layer to prevent water vapor condensation.) The gas flow from the first low-temperature reaction bed is mixed with the supplementary gas flow containing SO2, H2 and optional H2S in the mixing space between the two catalyst beds and then enters the second high-temperature reaction bed. The N2 gas flow, H2 gas flow and SO2 gas flow enter the gas mixer 10 respectively, and the resulting mixed gas flow enters the tubular stainless steel reactor 1 (the valve is opened periodically to take gas for gas chromatograph 17 to detect the sulfide composition and content).

[0077] The gas stream discharged from the tubular stainless steel reactor 1 (with elemental sulfur removed by the sulfur collection tube 3) is mostly dehydrated by the water vapor condenser 15 located in the freezer, and then deeply dehumidified by the dryer 16 containing anhydrous calcium chloride. The gas is periodically taken out by the valve and sent to the gas chromatograph 17 to detect the sulfide composition and content. The remaining gas stream is treated by the desulfurization tank 18 and then discharged into the air.

[0078] In the tubular stainless steel reactor 1, the first catalyst bed contains 20 mL of catalyst (bed height-to-diameter ratio of approximately 2), and the second catalyst bed contains 100 mL of a mixture of catalyst and quartz sand (volume dilution ratio of 1:4) (bed height-to-diameter ratio of approximately 10). Therefore, the total catalyst loading in both reaction sections is 40 mL (20 mL each). The catalyst (pre-crushed and sieved) and quartz sand are both 1.1-1.3 mm in size. In the preheating section above the first catalyst bed, the quartz sand loading is 170 mL.

[0079] Using the sulfur recovery catalyst evaluation device, performance evaluation tests were conducted on the catalysts prepared in the above embodiments under fixed-bed conditions for the reaction of sulfur production from sulfur dioxide and hydrogen. The purity of the sulfur dioxide, hydrogen, and nitrogen used was 99.9 v, and the water was deionized water. After the catalyst was loaded and the tubular stainless steel reactor 1 was tested for tightness, the catalyst was pre-sulfurized. The pre-sulfurization process of the catalyst was as follows: the two reaction sections were heated simultaneously, with gas introduced through the first stage at a flow rate of 80 NL / h; after purging the bed with nitrogen for 15 min at a bed temperature of 150°C, the gas composition was controlled to be 2 v% H2S, 6 v% H2, and the balance of N2, with a heating rate of 10°C / min. The sulfurization operation was completed after holding the temperature at 250°C for 2 h; under the condition of a gas flow rate of 30 NL / h and a gas composition of 0.5 v% H2S and the balance of N2, the temperature of the catalyst bed was adjusted to 160-170°C for the first stage and 280-290°C for the second stage before the activity evaluation test was conducted.

[0080] During the evaluation process, the pressure inside the tubular stainless steel reactor 1 was 5-10 kPa (gauge pressure). The initial activity of each catalyst was evaluated according to the following order and reaction conditions: SO2 conversion rate was calculated based on the SO2 content in the exhaust gas measured by gas chromatography (at least 3 valid measurements per hour) and the SO2 10v% content in the first-stage inlet gas; elemental sulfur selectivity was calculated based on the SO2 and H2S content in the exhaust gas measured by gas chromatography and the SO2 10v% content in the first-stage inlet gas; elemental sulfur yield was the product of SO2 conversion rate and elemental sulfur selectivity.

[0081] Reaction Condition 1: The first stage inlet gas flow rate is 80 NL / h, and the composition of the first stage inlet gas is 10 v% SO2, 10 v% H2, 30 v% water vapor, and the balance N2. The temperature at the bottom of the quartz sand preheating section is controlled at 160-162℃ by controlling the external heating temperature of the first stage at 165-175℃ and adjusting it appropriately within this range (the temperature measuring point is close to the outer wall of the brass heat spreader). The highest temperature of the first stage bed is measured by a thermocouple that can move vertically within the height range of the bed. The second stage inlet is hydrogen, with a flow rate of 8 NL / h. The temperature at the vertical center of the second stage catalyst bed is used as the control temperature for the external heating of the second stage and set at 300℃. The total space velocity (total inlet gas flow rate 88 NL / h and total catalyst volume 40 mL) is abbreviated as 2200 h⁻¹. -1 Steady-state evaluation time: 2-4 hours.

[0082] Reaction condition two: Based on condition one, the composition of the first-stage inlet gas is controlled to contain 10v% SO2, 10v% H2, 40v% water vapor and the balance N2 (the water vapor content is adjusted from 30v% to 40v%), while other conditions remain unchanged (the temperature at the vertical center of the second-stage catalyst bed is controlled at 300℃), and steady-state evaluation is continued for 2-4 hours.

[0083] Reaction condition 3: Based on condition 2, the temperature at the vertical center of the two-stage catalyst bed is controlled at 320℃, while other conditions remain unchanged, and steady-state evaluation is continued for 8-10 hours.

[0084] Reaction condition four: Based on condition three, the composition of the first-stage inlet gas is controlled to contain approximately 10v% SO2, 10v% H2, 43v% water vapor, and the balance N2 (the water vapor content is adjusted from 40v% to approximately 43v% and further adjusted according to the reaction effect, so that the calculated water vapor content in the reactor outlet gas flow is 60v%). Other conditions remain unchanged (the temperature at the vertical center of the second-stage catalyst bed is controlled at 320℃), and steady-state evaluation continues for 8-10 hours.

[0085] Reaction condition 5: Based on condition 3, the composition of the first-stage inlet gas is controlled to contain 10v% SO2, 10v% H2, 54v% water vapor, and the balance N2 (the water vapor content is adjusted from 40v% to 54v% so that the water vapor content in the reactor outlet gas flow is about 70v%), while other conditions remain unchanged (the temperature at the vertical center of the second-stage catalyst bed is controlled at 320℃), and the evaluation continues for 8-10 hours.

[0086] The evaluation of the reaction effects of each catalyst in Examples 1-5 includes the following: the effects under reaction conditions one and two are listed in Tables 1 and 2 respectively. The effects under reaction conditions three and four are similar to those listed in Table 2. All catalysts are very stable, and the yield of elemental sulfur is higher than 81%.

[0087] However, during the evaluation under reaction condition five (water vapor content of 54 vol%, resulting in a water vapor content of approximately 70 vol% in the reactor outlet gas stream), the stability of the catalyst reaction effect in Examples 1 and 5 decreased slightly, with the elemental sulfur yield repeatedly falling below 80%. The catalysts in Examples 2-4 showed better reaction stability, with elemental sulfur yields consistently above 80%. The catalyst in Example 4 was further evaluated under reaction condition five for 100 hours, and the reaction effect remained very stable, with the elemental sulfur yield consistently maintained between 80.5% and 81%.

[0088] Table 1. Evaluation of the initial activity of the catalyst under the reaction conditions.

[0089]

[0090] Table 2 Evaluation of the initial activity of the catalyst under reaction condition 2

[0091]

[0092] The above evaluation results demonstrate that the catalyst exhibits good wide-temperature reaction performance, heat resistance, and water vapor resistance in the selective reduction reaction of sulfur from sulfur dioxide and hydrogen. It maintains high and stable reaction performance under conditions of relatively low inlet gas flow temperature (160-180℃), maximum bed temperature (300℃, 320℃), and water vapor content as high as 60% v%. The single-pass yield of elemental sulfur exceeds 80%, indicating high reaction efficiency. The catalyst shows promising application prospects in the reaction of sulfur from sulfur dioxide and hydrogen.

[0093] Evaluation Example 2

[0094] In the sulfur recovery catalyst evaluation apparatus used in Evaluation Example 1, the catalysts prepared in Comparative Examples 1 and 2 above, as well as commercially available hydrogenation catalysts that react sulfur dioxide with hydrogen to produce elemental sulfur and / or hydrogen sulfide, such as catalysts with active components of cobalt, nickel, molybdenum, and tungsten supported on titanium oxide and / or alumina, including retained samples of catalyst AM prepared in each example of CN101745399A, and catalysts prepared using the raw materials and equipment conditions used in Example 1 of the present invention according to the method of Example 10 of CN101745399A (with indicators similar to those of catalyst J in CN101745399A), were evaluated for activity under reaction conditions one to four according to the catalyst loading, sulfidation, gas mixing, and temperature control methods of Evaluation Example 1. When the highest temperature of a bed section is below 200°C, the total yield of elemental sulfur in the reactor is below 65%, or the performance is not stable enough, the evaluation is stopped and the catalyst is unloaded. The results showed that no catalyst was found that could achieve a yield of elemental sulfur exceeding 75% and maintain stable performance during the evaluation process under reaction conditions one through four.

[0095] The evaluation results of the catalysts prepared in Examples 1-5, the catalysts prepared in Comparative Examples 1-2, and catalyst J in CN101745399A illustrate that the catalysts prepared in this invention, including TiO2 obtained by calcining metatitanic acid powder at 550-570℃ and TiO2 obtained by calcining below 480℃, Al2O3 obtained by calcining pseudoboehmite powder at 750-800℃ and Al2O3 obtained by calcining below 480℃, and the contained ZnO, all played a significant role after combining with the active components Co and Mo. This ensured the low-temperature reaction performance at 160-180℃ and significantly improved the reaction performance and stability of the catalyst at 300℃, 320℃, and with a water vapor content as high as 50-60v%, and achieved a single-pass yield of over 80% elemental sulfur.

Claims

1. A selective reduction catalyst for producing sulfur from sulfur dioxide, characterized by 1-2wt% CoO, 4-10wt% MoO3 and 2-4wt% ZnO, carrier is TiO2-Al2O3; it is made by following steps: (A) calcining metatitanic acid dry powder at 550-570℃ for 3-5h to obtain TiO2 powder; calcining pseudo-boehmite dry powder at 750-800℃ for 3-5h to obtain Al2O3 powder; mixing and ball milling the obtained TiO2 powder and Al2O3 powder in a ball mill to obtain TiO2-Al2O3 mixed powder; (B) adding metatitanic acid dry powder and pseudo-boehmite dry powder in a kneader, mixing uniformly to obtain powder; spraying acetic acid aqueous solution into the powder through an atomizing nozzle, continuing mixing after the acetic acid aqueous solution is added completely, stopping mixing and placing in a sealed state; adding zinc compound dry powder, TiO2-Al2O3 mixed powder of step (A) and organic pore-forming agent powder, mixing uniformly, spraying water through an atomizing nozzle, discharging after kneading uniformly, extruding and cutting, drying, calcining in air to obtain TiO2-Al2O3 carrier containing ZnO; (C) adding the TiO2-Al2O3 carrier containing ZnO obtained in step (B) in a spray-impregnation drum, spraying cobalt-molybdenum ammonia aqueous solution through an atomizing nozzle, placing in a sealed state after spraying cobalt-molybdenum ammonia aqueous solution is completed, homogenizing, discharging, drying and calcining to obtain a selective reduction catalyst for preparing sulfur from sulfur dioxide; The cobalt-molybdenum ammonia aqueous solution in step (C) is prepared from raw materials, which include ammonium molybdate, cobalt nitrate and ammonia water, wherein the concentration of ammonia water is 15-20wt%.

2. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, characterized by The weight ratio of TiO2 powder and Al2O3 powder in step (A) is 1: (2-3), the fineness of metatitanic acid dry powder and pseudo-boehmite dry powder is -600 mesh, and the fineness of TiO2-Al2O3 mixed powder is -200 mesh.

3. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The concentration of acetic acid aqueous solution in step (B) is 18-30wt%, the weight ratio of pseudo-boehmite dry powder to acetic acid aqueous solution is 1: (0.5-0.8); the time for continuing mixing is 40-60min, and the placing time is 15-20h; the calcining temperature is 450-480℃, and the calcining time is 2-4h; the zinc compound dry powder is zinc hydroxide dry powder or basic zinc carbonate dry powder; the organic pore-forming agent powder is a mixture of sesbania powder and polyacrylamide at a weight ratio of 1: (2-4), and the molecular weight of polyacrylamide is 10-20 million.

4. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The weight ratio of the metatitanic acid dry powder, the pseudo-boehmite dry powder, the zinc compound dry powder, the TiO2-Al2O3 mixed powder, the organic pore-forming agent powder and the water contained in the acetic acid aqueous solution and the water sprayed in the step (B) is (20-30):(15-25):(2-5):(45-65):(2-4):(95-140), wherein the metatitanic acid dry powder is calculated based on TiO2, the pseudo-boehmite dry powder is calculated based on Al2O3, and the zinc compound dry powder is calculated based on ZnO; the fineness of the metatitanic acid dry powder and the pseudo-boehmite dry powder is both-600 mesh, and the fineness of the zinc compound dry powder is-200 mesh; the shape of the TiO2-Al2O3 carrier containing ZnO is one of a cylindrical shape, a trilobal shape or a quadrilobal shape, and the equivalent external size of the TiO2-Al2O3 carrier containing ZnO is Φ(2.5-4)×(3-8) mm.

5. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The index of the metatitanic acid dry powder in step (A) and step (B) is: SO4 2- content ≤0.5%, after calcination at 450℃, has a specific surface area ≥130m 2 / g and a pore volume ≥0.25mL / g; the metatitanic acid dry powder is made by the following method: using industrial metatitanic acid by sulfuric acid method with SO4 2- content 1.5-5wt%, average particle size ≤1μm as raw material, treating with a washing liquid containing ammonia 1-3wt% for 3-10h, filtering the slurry, washing with water, drying, and crushing to obtain the metatitanic acid dry powder; the pseudo-boehmite dry powder in step (A) and step (B) has a specific surface area 300-350m 2 / g and a pore volume 0.75-0.9mL / g after calcination at 450℃.

6. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The adding amount of the cobalt-molybdenum ammonia aqueous solution in the step (C) is 95-100% of the saturated water absorption volume of the TiO2-Al2O3 carrier containing ZnO; the ammonium molybdate is ammonium heptamolybdate or ammonium tetramolybdate, the concentration of the ammonium molybdate in the cobalt-molybdenum ammonia aqueous solution is 143-316 g / L, and the concentration of the cobalt nitrate in the cobalt-molybdenum ammonia aqueous solution is 78-166 g / L.

7. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The raw material further includes ethylenediamine, and the concentration of the ethylenediamine in the cobalt-molybdenum ammonia aqueous solution is 6-10 g / L.

8. The selective reduction catalyst for producing sulfur from sulfur dioxide according to claim 1, wherein The homogenization treatment time in the step (C) is 10-15 h, the calcination temperature is 450-480 ℃, and the calcination time is 2-4 h.

9. A method for using the selective reduction catalyst for producing sulfur from sulfur dioxide according to any one of claims 1 to 8, characterized in that The sulfur dioxide gas stream, the hydrogen gas stream and the dilution gas stream are mixed to obtain a mixed gas stream, the mixed gas stream is preheated to 160-180 ℃, and then is reacted in a fixed bed reactor or a plurality of fixed bed reactors connected in series in sequence, which is filled with a selective reduction catalyst for preparing sulfur from sulfur dioxide, to obtain elemental sulfur, hydrogen sulfide and water vapor; one or more catalyst beds are arranged in each fixed bed reactor.

10. The method of claim 9, wherein the selective reduction catalyst for producing sulfur from sulfur dioxide is used in a process for producing sulfur from sulfur dioxide. The total volume flow of the hydrogen stream is 1.9-2.1 times the total volume flow of the sulfur dioxide stream, the maximum temperature of each catalyst bed is controlled to be 220-320°C; hydrogen stream is supplemented in the process gas stream between the catalyst beds and / or between the fixed bed reactors; the volume content ratio of SO2 to H2 in the inlet gas stream of each catalyst bed is 1:(0.5-1), the H2 content is 6-10v%; the gas hourly space velocity of each catalyst bed is 500-6000h -1 , the dilution gas stream contains water vapor and / or N2, and the upper limit of the water vapor content in the outlet gas stream of the fixed bed reactor is 60v%.

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