A catalyst for preparing sulfur by catalytic reduction of SO2 with CO and its preparation method

Abstract

The present invention provides a method for preparing a catalyst for catalytically reducing SO2 to sulfur with CO. The method first uses a hydrothermal method to prepare Co3O4 nanorods. Ce(NO3)3·6H2O and Gd(NO3)3·6H2O are fully loaded onto the Co3O4 nanorods using dimethyl sulfoxide (DMSO) as a solvent. After drying and calcining, an oxidized catalyst with the Co3O4 nanorods as a carrier and a cerium-gadolinium composite oxide as an active component is obtained. The catalyst is then pre-sulfurized with 1% SO2 and 2% CO to obtain a final sulfurized catalyst. The catalyst has high reaction activity, can achieve high sulfur conversion efficiency at relatively low temperatures, has strong sulfur selectivity, and has a high sulfur recovery rate.

Description

Technical Field

[0001] The present invention relates to the field of air purification, and in particular to a catalyst for preparing sulfur by catalytic reduction of SO2 by CO and a preparation method thereof. Background Art

[0002] Sulfur dioxide, a colorless gas with a strong, pungent odor, is a major atmospheric pollutant. Most of the SO2 in the air comes from the combustion of sulfur-containing fuels in power generation and industrial processes, negatively impacting human health and the environment. Currently, the most widely used flue gas desulfurization process is limestone / lime-gypsum wet flue gas desulfurization. While highly efficient, this method requires anti-corrosion treatment of chimneys, increasing operating costs. The byproduct, desulfurization gypsum, is produced excessively, requiring extensive storage and disposal, and can easily cause secondary pollution if not handled properly.

[0003] Direct catalytic reduction desulfurization is the process of reducing SO2 to sulfur for recovery using a reducing agent (C, H2, CH4, CO, etc.) in the presence of a catalyst. Sulfur is a scarce and important industrial raw material in my country, which can compensate for the high cost of desulfurization to a certain extent. Compared with wet desulfurization, direct catalytic reduction desulfurization has a high product utilization rate and a small footprint. Therefore, this method will have great application prospects. In the direct catalytic reduction method, compared with other reducing agents, CO has an abundant source, is easy to transport, has a low catalytic temperature, and produces high-purity sulfur. Therefore, the development of efficient catalysts for the catalytic reduction of SO2 to sulfur by CO is a research hotspot. Summary of the Invention

[0004] The present invention provides a method for preparing a catalyst for catalytic reduction of SO2 to produce sulfur by CO. The method comprises the following steps: using a hydrothermal method to prepare Co3O4 nanorods as a carrier; the Co3O4 nanorods have a high specific surface area and can increase the loading amount of active components; using an impregnation method to impregnate the Co3O4 nanorods into DMSO dissolved with cerium and gadolinium to fully load the catalyst; and calcining and pre-sulfiding to obtain the final sulfurized catalyst.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for preparing a catalyst for catalytic reduction of SO2 to produce sulfur by CO, the method comprising the following steps:

[0007] a. Add Co(NO3)2·6H2O to a mixed solution 1 of ethylene glycol and water, stir evenly to obtain a mixed solution 2, and pour the mixed solution 2 into a reactor for a hydrothermal reaction;

[0008] b. Cooling the mixture after the hydrothermal reaction in step (a) to room temperature, washing with deionized water and ethanol, and centrifuging to collect the precipitate, and drying to obtain Co3O4 nanorods;

[0009] c. Weigh Ce(NO3)3·6H2O and Gd(NO3)3·6H2O in a beaker, add dimethyl sulfoxide, and stir evenly to obtain a mixed solution 3. Immerse the Co3O4 nanorods prepared in step (b) in the mixed solution 3 for 1 to 3 hours, fully load, dry, and then calcine to obtain an oxidized catalyst with Co3O4 nanorods as a carrier and cerium-gadolinium composite oxide as an active component;

[0010] d. The oxidized catalyst in step (c) was placed in a mortar, ground and sieved, and the oxidized catalyst was placed in an 8 mm quartz tube and fixed. The tube furnace was connected and pre-sulfurized at 400-500° C. to obtain the final sulfurized catalyst.

[0011] In the technical solution of the present invention, the volume ratio of ethylene glycol to water in the mixed solution 1 of step (a) is 1:2-6, and the molar concentration of cobalt ions in the mixed solution 2 is 0.6-1 mol / L.

[0012] In the technical solution of the present invention: the hydrothermal reaction temperature of step (a) is 140-160° C., and the reaction time is 12-24 hours.

[0013] In the technical solution of the present invention: in step (c), the mass ratio of dimethyl sulfoxide, Ce(NO3)3·6H2O and Co3O4 nanorods is 40-60:2-9:5-10.

[0014] In the technical solution of the present invention: in step (c), the molar ratio of Ce(NO3)3·6H2O to Gd(NO3)3·6H2O is 10:0.5-1.

[0015] In the technical solution of the present invention: after sufficient load drying in step (c), the calcination temperature is 400-500° C. and the calcination time is 3-4 hours.

[0016] In the technical solution of the present invention: the catalyst particle size in step (d) is 20 to 40 meshes.

[0017] In the technical solution of the present invention: in step (d), the total flow rate of the presulfurization gas is 400-500 mL / min, which contains 0.5-1% SO2, 1-2% CO, and the rest is N2, and the presulfurization time is 1-2 hours.

[0018] A catalyst for catalytic reduction of SO2 with CO to produce sulfur is prepared by the above method.

[0019] In the technical solution of the present invention, the catalyst is used in the preparation of sulfur.

[0020] In the above application, the catalyst dosage is 0.5-1 mL, the total flow rate of the flue gas desulfurization reaction gas is 400-500 mL / min, containing 0.25-1% SO2, 0.5-2% CO, and the rest N2. The reaction temperature is 250-400°C. A heating belt is set at the tail end of the quartz tube, with a constant temperature of 120°C. The sulfur vapor passes through the heating belt along with other exhaust gases and enters the cold hydrazine to become solid, and the sulfur is collected.

[0021] Beneficial effects of the present invention:

[0022] Because currently widely used industrial flue gas desulfurization processes generate acid mist, severely corrode equipment, are difficult to handle, consume high energy and water resources, and require complex systems, this invention innovatively proposes using CO in the presence of a catalyst to reduce SO₂ and convert it into elemental sulfur. Using DMSO as a solvent, the active component, a cerium-gadolinium composite oxide, is fully loaded onto the Co₃O₄ nanorod support, increasing the active component loading and thus improving catalytic performance. The unique valence electron configuration of rare earth elements offers advantages unmatched by ordinary elements, enhancing the activity and selectivity of the active component and extending its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a scanning electron microscope image of the catalyst prepared in Example 2;

[0024] Figure 2 The sulfur product generated by the catalytic reduction reaction of the catalyst prepared in Example 2;

[0025] Figure 3 Figure 1 is a graph of the SO2 conversion efficiency of the catalysts prepared in Examples 1 to 3; DETAILED DESCRIPTION

[0026] The present invention will be further described below with reference to the following examples, but the scope of protection of the present invention is not limited thereto: Example 1

[0027] (1) Prepare 50 mL of a mixed solution containing 10 mL of ethylene glycol and 40 mL of deionized water. Weigh 8.73 g of Co(NO3)2·6H2O and dissolve it in the mixed solution. The molar concentration of cobalt ions is 0.6 mol / L. Stir well and pour into a hydrothermal reactor. React at 160°C for 12 h.

[0028] (2) After the hydrothermal reaction, the mixture was cooled to room temperature, washed with deionized water and ethanol, and centrifuged three times. The precipitate was collected and dried to obtain Co3O4 nanorods.

[0029] (3) Weigh 2.525g of Ce(NO3)3·6H2O and 0.1312g of Gd(NO3)3·6H2O and dissolve them in 50g of DMSO solvent, where the molar ratio of Ce(NO3)3·6H2O to Gd(NO3)3·6H2O is 10:0.5. Stir well and weigh 5g of Co3O4 nanorods and immerse them in the mixed solution for 2h. After being fully loaded, place them in a muffle furnace and calcine them at 400℃ for 4h to obtain an oxidized catalyst with Co3O4 nanorods as the support and cerium-gadolinium composite oxide as the active component.

[0030] (4) The oxidized catalyst was ground and sieved in a mortar. 0.5 mL of the 20-40 mesh catalyst was measured and placed in an 8 mm quartz tube, fixed. The tube furnace was connected and pre-sulfurized at 500 ° C for 2 h. The total flow rate of the pre-sulfurization gas was 400 mL / min, containing 1% SO2, 2% CO, and the rest N2, to obtain the final sulfurized catalyst.

[0031] (5) The sulfided catalyst obtained by the above method is used in the catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 0.5 mL, the total gas flow rate is 400 mL / min, and the gas contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250-400°C. A heating belt is set at the tail end of the quartz tube and the temperature is kept at 120°C. The sulfur vapor passes through the heating belt along with other exhaust gases and enters the cold hydrazine to become solid, and the sulfur is collected.

[0032] Example 2

[0033] (1) Prepare 50 mL of a mixed solution containing 12.5 mL of ethylene glycol and 37.5 mL of deionized water. Weigh 13.095 g of Co(NO3)2·6H2O and dissolve it in the mixed solution. The molar concentration of cobalt ions is 0.9 mol / L. Stir well and pour into a hydrothermal reactor. React at 140°C for 24 h.

[0034] (2) After the hydrothermal reaction, the mixture was cooled to room temperature, washed with deionized water and ethanol, and centrifuged six times. The precipitate was collected and dried to obtain Co3O4 nanorods.

[0035] (3) Weigh 5.05g of Ce(NO3)3·6H2O and 0.525g of Gd(NO3)3·6H2O and dissolve them in 50g of DMSO solvent, where the molar ratio of Ce(NO3)3·6H2O to Gd(NO3)3·6H2O is 10:1. Stir well and weigh 5g of Co3O4 nanorods and immerse them in the mixed solution for 2h. After being fully loaded, place them in a muffle furnace and calcine them at 500℃ for 4h to obtain an oxidized catalyst with Co3O4 nanorods as the support and cerium-gadolinium composite oxide as the active component.

[0036] (4) The oxidized catalyst was ground and sieved in a mortar. 1 mL of the catalyst with a mesh size of 20-40 was measured and placed in an 8 mm quartz tube. The tube furnace was connected and pre-sulfurized at 500°C for 2 h. The total flow rate of the pre-sulfurization gas was 400 mL / min, containing 1% SO2, 2% CO, and the remainder N2, to obtain the final sulfurized catalyst.

[0037] (5) The sulfided catalyst obtained by the above method is used in the catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, and the gas contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250-400°C. A heating belt is set at the tail end of the quartz tube and the temperature is kept at 120°C. The sulfur vapor passes through the heating belt along with other exhaust gases and enters the cold hydrazine to become solid, and the sulfur is collected.

[0038] Example 3

[0039] (1) Prepare 50 mL of a mixed solution containing 15 mL of ethylene glycol and 35 mL of deionized water. Weigh 8.73 g of Co(NO3)2·6H2O and dissolve it in the mixed solution. The molar concentration of cobalt ions is 0.6 mol / L. Stir well and pour into a hydrothermal reactor. React at 160°C for 24 h.

[0040] (2) After the hydrothermal reaction, the mixture was cooled to room temperature, washed with deionized water and ethanol, and centrifuged six times. The precipitate was collected and dried to obtain Co3O4 nanorods.

[0041] (3) Weigh 5.05g of Ce(NO3)3·6H2O and 0.2625g of Gd(NO3)3·6H2O and dissolve them in 50g of DMSO solvent, where the molar ratio of Ce(NO3)3·6H2O to Gd(NO3)3·6H2O is 10:0.5. Stir well and weigh 10g of Co3O4 nanorods and immerse them in the mixed solution for 2h. After being fully loaded, place them in a muffle furnace and calcine them at 500℃ for 4h to obtain an oxidized catalyst with Co3O4 nanorods as the support and cerium-gadolinium composite oxide as the active component.

[0042] (4) The oxidized catalyst was ground and sieved in a mortar. 0.5 mL of the 20-40 mesh catalyst was measured and placed in an 8 mm quartz tube. The tube furnace was connected and pre-sulfurized at 500 ° C for 2 h. The total flow rate of the pre-sulfurization gas was 400 mL / min, containing 0.5% SO2, 1% CO, and the rest N2, to obtain the final sulfurized catalyst.

[0043] (5) The sulfided catalyst obtained by the above method is used in the catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, and the gas contains 1% SO2, 2% CO, and the rest is N2. The reaction temperature is 250-400°C. A heating belt is set at the tail end of the quartz tube and the temperature is set at 120°C. The sulfur vapor passes through the heating belt along with other exhaust gases and enters the cold hydrazine to become solid, and the sulfur is collected.

[0044] Comparative Example 1

[0045] The catalyst was prepared under the same conditions as in Example 1 except that DMSO was replaced with deionized water in step (3). The obtained sulfide catalyst was used in the catalytic reduction of SO2 to produce sulfur by CO. The catalyst dosage was 1 mL, the total gas flow rate was 400 mL / min, containing 1% SO2, 2% CO, and the remainder N2. The reaction temperature was 250-400°C. A heating zone was set at the tail end of the quartz tube and kept at 120°C. The sulfur vapor passed through the heating zone along with the other tail gases and entered the cold hydrazine to become solid, and the sulfur was collected. The SO2 conversion rate comparison effect is shown in FIG. Figure 3 As shown in the figure, the catalytic performance decreased due to insufficient catalyst loading due to the solvent being changed to deionized water.

[0046] Comparative Example 2

[0047] During the catalyst preparation, except that Gd(NO3)3·6H2O is not added in step (3), other conditions are the same as those in Example 2; the obtained sulfide catalyst is used in the catalytic reduction of SO2 to sulfur by CO, the catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, containing 1% SO2, 2% CO, and the rest N2, the reaction temperature is 250-400°C, a heating zone is set at the tail end of the quartz tube, and the temperature is set at 120°C. The sulfur vapor passes through the heating zone along with other tail gases and enters the cold hydrazine to become solid, and the sulfur is collected. The comparison effect of SO2 conversion rate is shown in FIG. Figure 3 As shown in the figure, due to the single active component, the catalyst is easily deactivated, resulting in a decrease in catalytic performance.

Claims

1. A method for preparing a catalyst for catalytic reduction of SO2 with CO to produce sulfur, characterized by: The method comprises the following steps: a. Add Co(NO3)2·6H2O to a mixed solution 1 of ethylene glycol and water, stir evenly to obtain a mixed solution 2, and pour the mixed solution 2 into a reactor for a hydrothermal reaction; b. Cooling the mixture after the hydrothermal reaction in step (a) to room temperature, washing with deionized water and ethanol, and centrifuging to collect the precipitate, and drying to obtain Co3O4 nanorods; c. Weigh Ce(NO3)3·6H2O and Gd(NO3)3·6H2O in a beaker, add dimethyl sulfoxide, and stir evenly to obtain a mixed solution 3. Immerse the Co3O4 nanorods prepared in step (b) in the mixed solution 3 for 1-3 h, fully load, dry, and then calcine to obtain an oxidized catalyst with Co3O4 nanorods as a support and cerium-gadolinium composite oxide as an active component; d. Grind and sieve the oxidized catalyst in a mortar, place the oxidized catalyst in an 8 mm quartz tube, and secure it in place. Connect the tube furnace and pre-sulfurize it at 400-500° C. to obtain the final sulfurized catalyst.

2. The preparation method according to claim 1, characterized in that: The volume ratio of ethylene glycol to water in the mixed solution 1 of step (a) is 1:2-6, and the molar concentration of cobalt ions in the mixed solution 2 is 0.6-1 mol / L.

3. The preparation method according to claim 1, characterized in that: The hydrothermal reaction temperature of step (a) is 140-160° C., and the reaction time is 12-24 hours.

4. The preparation method according to claim 1, characterized in that: In step (c), the mass ratio of dimethyl sulfoxide, Ce(NO3)3·6H2O and Co3O4 nanorods is 40-60:2-9:5-10.

5. The preparation method according to claim 1, characterized in that: In step (c), the molar ratio of Ce(NO3)3·6H2O to Gd(NO3)3·6H2O is 10:0.5~1.

6. The preparation method according to claim 1, characterized in that: After sufficient loading and drying in step (c), the calcination temperature is 400-500° C. and the calcination time is 3-4 h.

7. The preparation method according to claim 1, characterized in that: The catalyst particles in step (d) have a size of 20-40 mesh.

8. The preparation method according to claim 1, characterized in that: In step (d), the total flow rate of the presulfurization gas is 400-500 mL / min, containing 0.5-1% SO2, 1-2% CO, and the remainder N2, and the presulfurization time is 1-2 h.

9. A catalyst for catalytic reduction of SO2 with CO to produce sulfur, characterized by: The catalyst is prepared by the method according to any one of claims 1 to 8.

10. Use of the catalyst prepared by the method of claim 1 in the preparation of sulfur.

11. The use according to claim 10, characterized in that The catalyst dosage is 0.5~1 mL, the total flow rate of flue gas desulfurization reaction gas is 400~500 mL / min, which contains 0.25~1% SO2, 0.5~2% CO, and the rest is N2. The reaction temperature is 250~400℃. A heating belt is set at the tail end of the quartz tube with a constant temperature of 120℃. The sulfur vapor passes through the heating belt with other exhaust gases and enters the cold hydrazine to become solid, and the sulfur is collected.

Images