A nanosheet catalyst, its preparation method and application

Abstract

The present invention discloses a nano-sheet catalyst, a preparation method thereof and an application thereof. The catalyst uses nickel-zirconium composite oxide as a catalytic active component, scandium-yttrium composite oxide as a co-catalytic active component, ammonia water as a precipitant, sodium dodecyl aminopropionate as a surface activator, and octadecylamine as a morphology control agent, and is prepared by a hydrothermal-calcination method. The catalyst has the advantages of a nano-scale sheet stacking structure, a large specific surface area, high catalytic activity, a long service life, etc., and is particularly suitable for catalytic reduction of SO2 to sulfur by CO in blast furnace gas, metallurgical flue gas, synthetic ammonia feed gas and yellow phosphorus production tail gas in the iron and steel industry.

Description

Technical Field

[0001] The present invention provides a nano-sheet catalyst, a preparation method thereof and an application thereof, belonging to the fields of environmental protection catalytic materials and air pollution control. Background Art

[0002] SO2 has a strong pungent smell. Long-term contact with the human body will cause respiratory diseases. At the same time, it is also the main cause of acid rain in China. Acid rain has become one of the most serious environmental pollution problems in the world. At present, the conventional treatment technologies generally adopt wet, semi-dry and dry desulfurization of flue gas after combustion. Although the conventional desulfurization process has a high desulfurization rate and stable operation, the utilization rate of the by-products generated is low, occupying a large amount of land area and easily causing secondary pollution. The resource-based flue gas desulfurization process can solve the environmental problems caused by it. The resource-based flue gas desulfurization process is to convert SO2 in the flue gas into by-products with higher added values such as sulfuric acid and sulfur. According to different reducing agents, it can be divided into hydrogen reduction method, carbon reduction method, methane reduction method, carbon monoxide reduction method, ammonia reduction method, etc. Compared with other reducing agents such as H2, CH4, and NH3, CO has a wide source, is easy to transport and store, and the reaction temperature is relatively low. The by-products generated in the reaction are less, and the purity of the sulfur product obtained is higher. The selection of the catalyst is the core of this process.

[0003] Patents at home and abroad have disclosed catalysts for catalytic reduction of SO2 by CO to sulfur and preparation methods. The invention patent "A method for preparing a composite catalyst for catalytic reduction of SO2 by CO and recovering sulfur" (publication number CN 107497453A) provides a method for preparing a composite catalyst for catalytic reduction of SO2 by CO and recovering sulfur. This method uses microwave-assisted in-situ carbon template stabilization method to prepare perovskite-type La 1-x Ce x CoO3 (0≤x≤1) composite catalyst. This composite catalyst has good activity stability and can produce sulfur with higher purity. However, in this method, sulfur is mixed with the catalyst and then sulfur is extracted, and the process is relatively cumbersome and complex. The invention patent "A catalyst for catalytic reduction of carbon monoxide to sulfur dioxide and a preparation method thereof" (publication number: CN115282958A) provides a catalyst for catalytic reduction of carbon monoxide to sulfur dioxide and a preparation method thereof. The catalyst is composed of a carrier and an active component; the carrier is one or two of Al2O3 and CeO2; the active component is one or two of Ag2O and IrO2. The catalyst prepared by the method of the present invention has a higher conversion rate of carbon disulfide and higher sulfur selectivity at a lower temperature (350°C). When this catalyst catalyzes the reduction of SO2 by CO, the conversion rate of SO2 is 81-96%, and the selectivity for sulfur is 75-95%. However, this catalyst uses Ag and Ir noble metals as active components, increasing the cost of using the catalyst. Summary of the Invention

[0004] The object of the present invention is to propose a nano-sheet catalyst in view of the problems existing in the existing catalysts for catalytic reduction of SO2 by CO. Another object of the present invention is to provide a preparation method of the above catalyst.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] The technical solution of the present invention is as follows: The catalyst of the present invention uses nickel-zirconium composite oxide as the catalytic active component, scandium-yttrium composite oxide as the co-catalytic active component, ammonia water as the precipitating agent, sodium dodecyl aminopropionate as the surface activator, and octadecylamine as the morphology control agent, and is prepared by a hydrothermal-calcination method. The advantages of this catalyst are as follows: The preparation process of the catalyst is simple and easy to implement; the catalyst has a nano-layered stacked structure, which gives the catalyst a large specific surface area, exposes more active sites, is conducive to the full contact between the reactants and the catalyst, and improves the catalytic activity of the catalyst; the performance is stable, and the service life of the catalyst is extended.

[0007] The specific technical solution of the present invention is as follows:

[0008] A nano-sheet catalyst, wherein the catalyst uses nickel-zirconium composite oxide as the catalytic active component, scandium-yttrium composite oxide as the co-catalytic active component, ammonia water as the precipitating agent, sodium dodecyl aminopropionate as the surface activator, and octadecylamine as the morphology control agent; wherein, the mass ratio of the catalytic active component: co-catalytic active component: precipitating agent: surface activator: morphology control agent is 10:(1-3):(20-40):(2-4):(1-2).

[0009] In the technical solution of the present invention: the mass ratio of nickel oxide to zirconium oxide in the catalytic active component is 1:(3-5), and the mass ratio of scandium oxide to yttrium oxide in the co-catalytic active component is 1:(1-2)

[0010] In the technical solution of the present invention: the catalyst is prepared by the following method:

[0011] (1) Preparation of the precursor solution of the active component

[0012] Nickel salt, zirconium salt, scandium salt and yttrium salt are added to deionized water and stirred evenly to obtain the precursor solution of the active component;

[0013] (2) Preparation of the catalyst

[0014] The precipitating agent, surfactant and morphology control agent are sequentially added to the precursor solution prepared in step (1), and then a hydrothermal reaction is carried out. The hydrothermal product is washed with water until neutral, dried and then placed in a muffle furnace for calcination to obtain the catalyst.

[0015] In the technical solution of the present invention: in step (1), the nickel salt is nickel nitrate hexahydrate, the zirconium salt is zirconium oxychloride octahydrate, the scandium salt is scandium nitrate hexahydrate, and the yttrium salt is yttrium nitrate hexahydrate.

[0016] In the technical solution of the present invention: in step (2), the concentration of ammonia water is 25% - 28 wt%.

[0017] In the technical solution of the present invention: in step (2), the hydrothermal temperature is 160 - 180 °C, and the hydrothermal time is 6 - 10 h;

[0018] In the technical solution of the present invention: in step (2), the drying temperature is 80 - 100 °C, and the drying time is 2 - 4 h.

[0019] In the technical solution of the present invention: in step (2), the calcination temperature is 500 - 600 °C, and the calcination time is 4 - 6 h.

[0020] A sulfided catalyst, which is obtained by pre-sulfiding the above catalyst at 500 °C for 2 h. The total flow rate of the pre-sulfiding gas is 300 - 500 mL / min, including 0.5 - 5% SO2, 1 - 5% CO, and the rest is N2.

[0021] In the technical solution of the present invention, the application of the sulfided catalyst in sulfur production.

[0022] The catalytic reaction conditions and results of the present invention: Take 1 mL of 20 - 40 mesh catalyst and place it in an 8 mm quartz tube. Place the quartz tube in a tube furnace; pre-sulfide it at 500 °C for 2 h. The total flow rate of the pre-sulfiding gas is 400 mL / min, including 1% SO2, 2% CO, and the rest is N2 to obtain the final sulfided catalyst; the total flow rate of the flue gas desulfurization reaction gas is 400 - 500 mL / min, including 0.25 - 1% SO2, 0.5 - 2% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, conduct an activity test. Set a heating tape at the end of the quartz tube at a constant temperature of 120 °C. Sulfur vapor and other tail gases pass through the heating tape and turn into solids in the cold trap to collect sulfur.

[0023] Beneficial effects:

[0024] A nanoscale flaky catalyst prepared by the present invention can catalyze the reduction of SO2 by CO at a lower temperature. The catalyst of the present invention has a low applicable temperature, high conversion efficiency, and the SO2 conversion efficiency is greater than 90% within 250 - 500 °C. It has high selectivity, a simple preparation process, and low cost, and has broad market application prospects. It is especially suitable for catalytic reduction of SO2 to sulfur in blast furnace gas, metallurgical flue gas, synthetic ammonia feed gas, and tail gas from yellow phosphorus production in the steel industry.

[0025] The catalytic active component zirconia has a stable tetragonal crystal structure, with advantages such as high catalytic activity, high selectivity, and high stability, which can improve the low-temperature catalytic performance of the catalyst; nickel oxide has small particle size, uniform distribution, low loose bulk density, and is easy to disperse, and can be fully combined with zirconia to improve the catalyst performance; the co-catalytic active component yttrium oxide has good thermal stability, and scandium oxide has high strength and corrosion resistance, which can keep the catalyst stable under high-temperature conditions and extend the service life of the catalyst; octadecylamine can enter the tiny pores of the catalyst, regulate the catalyst to form a nano-sheet structure, expose more reactive sites, enhance the adsorption effect on SO2 and improve the catalyst performance. Description of the Drawings

[0026] Figure 1 SEM image of the catalyst prepared in Example 1;

[0027] Figure 2 Activity diagrams of the catalysts prepared in Examples 1-3 and Comparative Examples 1-2. Detailed Embodiments

[0028] The present invention will be further described below in conjunction with examples, but the protection scope of the present invention is not limited thereto:

[0029] Example 1 (1) Weigh 4.87 g of nickel nitrate hexahydrate, 9.81 g of zirconium oxychloride octahydrate, 1.23 g of scandium nitrate hexahydrate, and 0.85 g of yttrium nitrate hexahydrate, and add 50 mL of deionized water to obtain a precursor solution;

[0030] (2) Add the precursor solution prepared in step (1) to 10 g of ammonia water solution, transfer it to a hydrothermal reaction kettle, add 1 g of sodium dodecylaminopropionate and 1 g of octadecylamine. Transfer it to a blast drying oven for hydrothermal reaction at 160 °C for 10 h. After the hydrothermal reaction, the mixture is allowed to cool to room temperature, washed with deionized water until neutral, dried at 80 °C for 4 h, and transferred to a muffle furnace for calcination at 500 °C for 6 h to obtain a flaky catalyst;

[0031] (3) Grind and sieve the above-mentioned oxidized catalyst in a mortar, measure 1 mL of the catalyst with a particle size of 20-40 mesh and load it into an 8 mm quartz tube for fixation, connect a tube furnace, and pre-sulfurize it at 500 °C for 2 h. The total flow rate of the pre-sulfurization gas is 400 mL / min, including 1% SO2, 2% CO, and the rest is N2, to obtain the final sulfided catalyst;

[0032] (4) The sulfided catalyst obtained by the above method is applied to the reaction of catalytic reduction of SO2 with CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, which contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, an activity test is carried out. 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 with other tail gases and turns into a solid in the cold trap, and sulfur is collected. As Figure 2 shown, the test results show that the SO2 conversion efficiency is greater than 95% above 350 °C.

[0033] Example 2

[0034] (1) Weigh 3.23 g of nickel nitrate hexahydrate, 10.91 g of zirconium oxychloride octahydrate, 1.23 g of scandium nitrate hexahydrate, and 1.7 g of yttrium nitrate hexahydrate, and add 50 mL of deionized water to obtain a precursor solution;

[0035] (2) Add the precursor solution prepared in step (1) to 20 g of ammonia water solution, transfer it to a hydrothermal reaction kettle, and add 2 g of sodium dodecylaminopropionate and 1 g of octadecylamine. Transfer it to a blast drying oven for hydrothermal reaction at 180 °C for 6 h. After the hydrothermal reaction, the mixture is allowed to cool to room temperature, washed with deionized water until neutral, dried at 100 °C for 2 h, and then transferred to a muffle furnace for calcination at 600 °C for 4 h to obtain a flaky catalyst;

[0036] (3) Grind and sieve the above-mentioned oxidized catalyst in a mortar, measure 1 mL of the catalyst with a particle size of 20 - 40 mesh and place it in an 8 mm quartz tube for fixation. Connect the tubular furnace, and pre-sulfurize it at 500 °C for 2 h. The total flow rate of the pre-sulfurization gas is 400 mL / min, which contains 1% SO2, 2% CO, and the rest is N2, to obtain the final sulfided catalyst;

[0037] (4) The sulfided catalyst obtained by the above method is applied to the reaction of catalytic reduction of SO2 with CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, which contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, an activity test is carried out. 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 with other tail gases and turns into a solid in the cold trap, and sulfur is collected. As Figure 2 shown, the test results show that the SO2 conversion efficiency is greater than 82% above 350 °C.

[0038] Example 3

[0039] (1) Weigh 3.89 g of nickel nitrate hexahydrate, 10.46 g of zirconium oxychloride octahydrate, 0.81 g of scandium nitrate hexahydrate, and 1.13 g of yttrium nitrate hexahydrate, and add 50 mL of deionized water to obtain a precursor solution;

[0040] (2) Add the precursor solution prepared in step (1) to 15 g of ammonia water solution, transfer it to a hydrothermal reaction kettle, add 1.5 g of sodium dodecylaminopropionate and 0.5 g of octadecylamine. Transfer it to a forced air drying oven and carry out hydrothermal reaction at 170 °C for 8 h. After the hydrothermal reaction is completed, let the mixture cool to room temperature, wash it with deionized water until neutral, dry it at 90 °C for 3 h, and transfer it to a muffle furnace to calcine at 550 °C for 5 h to obtain a flaky catalyst;

[0041] (3) Grind and sieve the above-mentioned oxidized catalyst in a mortar, measure 1 mL of the 20 - 40 mesh catalyst and fix it in an 8 mm quartz tube, connect the tubular furnace, and pre-sulfurize it at 500 °C for 2 h. The total flow rate of the pre-sulfurization gas is 400 mL / min, which contains 1% SO2, 2% CO, and the rest is N2, to obtain the final sulfided catalyst;

[0042] (4) The sulfided catalyst obtained by the above method is applied to the reaction of catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, which contains 1% SO2, 2% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, carry out an activity test. Set a heating belt at the end of the quartz tube, keep the temperature at 120 °C, and the sulfur vapor passes through the heating belt with other tail gases and turns into a solid in the cold trap to collect sulfur. As Figure 2 shown, the test results show that the SO2 conversion efficiency is greater than 86% above 350 °C.

[0043] Comparative Example 1

[0044] Preparation of the catalyst

[0045] (1) Except that nickel nitrate hexahydrate is not added in step (1) during the catalyst preparation, other conditions are the same as in Example 1;

[0046] (2) Grind and sieve the above-mentioned oxidized catalyst in a mortar, measure 1 mL of the 20 - 40 mesh catalyst and fix it in an 8 mm quartz tube, connect the tubular furnace, and pre-sulfurize it at 500 °C for 2 h. The total flow rate of the pre-sulfurization gas is 400 mL / min, which contains 1% SO2, 2% CO, and the rest is N2, to obtain the final sulfided catalyst;

[0047] (3) The sulfided catalyst obtained by the above method is applied to the reaction of catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, which contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, an activity test is carried out. A heating belt is set at the tail end of the quartz tube, with a constant temperature of 120 °C. Sulfur vapor passes through the heating belt with other tail gases and turns into a solid in the cold trap, and sulfur is collected. As Figure 2 shown, the test results show that under all temperature conditions, the SO2 conversion rate is lower than 60%.

[0048] (4) Comparative effect

[0049] Compared with Example 1, when preparing the catalyst, nickel nitrate hexahydrate is not added in step (1). The active component of the catalyst is zirconia, not nickel-zirconium composite oxide, and the redox performance and activity of the catalyst decrease.

[0050] Comparative Example 2

[0051] Preparation of the catalyst

[0052] (1) Except that the morphology control agent octadecylamine is not added in step (2) when preparing the catalyst, other conditions are the same as in Example 2;

[0053] (2) The above-mentioned oxidized catalyst is put into a mortar, ground and sieved. 1 mL of the catalyst with a particle size of 20 - 40 meshes is taken and fixed in an 8 mm quartz tube. The tube furnace is connected, and pre-sulfidation is carried out at 500 °C for 2 h. The total pre-sulfidation gas flow rate is 400 mL / min, which contains 1% SO2, 2% CO, and the rest is N2, to obtain the final sulfided catalyst;

[0054] (3) The sulfided catalyst obtained by the above method is applied to the reaction of catalytic reduction of SO2 by CO to produce sulfur. The catalyst dosage is 1 mL, the total gas flow rate is 400 mL / min, which contains 0.25% SO2, 0.5% CO, and the rest is N2. The reaction temperature is 250 - 400 °C, with each 25 °C as a temperature point. After reacting for 10 min at each temperature point, an activity test is carried out. A heating belt is set at the tail end of the quartz tube, with a constant temperature of 120 °C. Sulfur vapor passes through the heating belt with other tail gases and turns into a solid in the cold trap, and sulfur is collected. As Figure 2 shown, the test results show that under all temperature conditions, the SO2 conversion rate is lower than 57%.

[0055] (4) Comparative effect

[0056] Compared with Example 2, when preparing the catalyst, octadecylamine, a morphology control agent, is not added in step (2). Although the catalyst forms a layered structure, the thickness of the catalyst is large, agglomeration occurs and it cannot reach the nanoscale. The specific surface area of the catalyst becomes smaller and the catalytic activity decreases.

Claims

1. A preparation method of a nano-sheet catalyst, characterized in that: The catalyst described above uses nickel-zirconium composite oxide as the catalytic active component, scandium-yttrium composite oxide as the co-catalytic active component, ammonia water as the precipitant, sodium dodecyl aminopropionate as the surface activator, and octadecylamine as the morphology control agent; among them, the mass ratio of the catalytic active component: co-catalytic active component: precipitant: surface activator: morphology control agent is 10: (1-3): (20-40): (2-4): (1-2); The catalyst described above is prepared by the following method: (1) Preparation of the precursor solution of the active component Add nickel salt, zirconium salt, scandium salt and yttrium salt to deionized water and stir evenly to obtain the precursor solution of the active component; (2) Preparation of the catalyst Add the precipitant, surfactant and morphology control agent to the precursor solution prepared in step (1) in sequence, then carry out hydrothermal reaction, wash the product after hydrothermal treatment to neutrality, dry it and place it in a muffle furnace for calcination to obtain the catalyst.

2. The preparation method of the nano-sheet catalyst according to claim 1, characterized in that: In the catalytic active component described above, the mass ratio of nickel oxide to zirconium oxide is 1: (3-5), and in the co-catalytic active component, the mass ratio of scandium oxide to yttrium oxide is 1: (1-2).

3. The preparation method of the nano-sheet catalyst according to claim 1, characterized in that: In step (1), the nickel salt is nickel nitrate hexahydrate, the zirconium salt is zirconyl oxychloride octahydrate, the scandium salt is scandium nitrate hexahydrate, and the yttrium salt is yttrium nitrate hexahydrate.

4. The preparation method of the nano-sheet catalyst according to claim 1, wherein: In step (2), the hydrothermal temperature is 160-180 °C and the hydrothermal time is 6-10 h.

5. The preparation method of the nanosheet catalyst according to claim 1, wherein: In step (2), the drying temperature is 80-100 °C and the drying time is 2-4 h.

6. The preparation method of the nano-sheet catalyst according to claim 1, wherein: In step (2), the calcination temperature is 500-600 °C and the calcination time is 4-6 h.

7. A sulfided catalyst, characterized in that: The sulfided catalyst obtained after pre-sulfiding the nano-sheet catalyst prepared by the method described in claim 1 at 500 °C for 2 h, wherein the total flow rate of the pre-sulfiding gas is 300-500 mL / min, containing 0.5-5% SO2, 1-5% CO, and the rest is N2.

8. Application of the sulfided catalyst described in claim 7 in the production of sulfur.

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