High-strength V2O5-based catalyst for oxidizing SO2 through low-temperature dry method and preparation method of high-strength V2O5-based catalyst

Abstract

The invention relates to the technical field of industrial catalysis and environmental protection, in particular to a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 and a preparation method thereof.The high-strength V2O5-based catalyst is prepared from, by mass, 5-10% of vanadium pentoxide, 1-5% of a cesium compound, 0.5-3% of a phosphorus compound, 0-5% of a potassium compound and the balance modified diatomite. The catalyst provided by the invention has good mechanical strength, low-temperature activity, loading capacity and catalytic performance.

Description

Technical Field

[0001] This invention relates to the fields of industrial catalysis and environmental protection technology, and in particular to a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 and its preparation method. Background Technology

[0002] Sulfur dioxide (SO2) is one of the major air pollutants, primarily originating from the combustion of fossil fuels and the smelting of non-ferrous metals. Catalytic oxidation of SO2 to sulfur trioxide (SO3) is a core step in sulfuric acid production and a crucial link in the resource utilization of flue gas desulfurization. Currently, vanadium-based catalysts, using V2O5 as the active component, alkali metal sulfates (mainly K2SO4) as co-catalysts, and diatomaceous earth as the support, are widely used in industry.

[0003] However, traditional V2O5-K2SO4 / SiO2 catalysts have some inherent drawbacks: Poor low-temperature activity: Its optimal activity temperature window is usually high (400-600℃). When the reaction temperature is below 400℃, the catalytic activity decreases significantly, resulting in a sharp decrease in SO2 conversion rate, which limits its application in low-temperature flue gas treatment and causes energy waste.

[0004] Insufficient mechanical strength: During transportation, loading and use, the catalyst is easily broken and pulverized, which leads to an increase in pressure drop in the reaction bed and affects the long-term stable operation of the unit.

[0005] To improve low-temperature activity, existing technologies typically employ the addition of multiple additives. For example, some studies have mentioned that adding elements such as Cs and Rb can lower the ignition temperature of the catalyst. However, simple addition often fails to simultaneously achieve both activity and strength, sometimes even sacrificing mechanical stability in pursuit of activity. Furthermore, process parameters (such as pH and temperature) have a decisive influence on the distribution of active components, the interactions between additives, and the final microstructure and performance of the catalyst, but this aspect is often overlooked in existing technologies, lacking systematic optimization and control.

[0006] Therefore, there is an urgent need to develop a catalyst that is highly active at low temperatures, has high mechanical strength, and is stable. Summary of the Invention

[0007] The purpose of this invention is to provide a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 and its preparation method, so as to solve the problems of low activity, poor mechanical properties and instability of current supported catalysts at low temperatures.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of this invention provides a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2, comprising the following raw materials in 100% by mass: 5-10% vanadium pentoxide, 1-5% cesium compound (Cs2O), 0.5-3% phosphorus compound (P2O5), 0-5% potassium compound (K2O), and the balance being modified diatomaceous earth.

[0009] The catalytic oxidation of SO2 is a core process in the industrial sulfuric acid production process. This reaction is reversible and exothermic, making the selection of the catalyst extremely crucial. Traditional catalysts for SO2 oxidation to sulfuric acid mainly include vanadium catalysts, platinum catalysts, and iron catalysts.

[0010] Most catalysts use diatomaceous earth as a carrier, but such catalysts often have poor mechanical properties. During transportation, filling and use, the catalyst is prone to breakage and pulverization, which leads to an increase in pressure drop in the reaction bed and affects the long-term stable operation of the device.

[0011] The catalyst of the present invention is prepared by loading vanadium pentoxide, cesium compounds, phosphorus compounds and potassium compounds as active components onto modified diatomaceous earth. This catalyst not only improves the loading rate of the active components, but also has higher mechanical properties and is not easily broken or pulverized.

[0012] In addition, vanadium pentoxide, as the core active phase in catalytic oxidation reactions, can increase the content of active centers by adjusting its addition amount, while also preventing overloading of the support surface and preventing a decrease in mechanical strength.

[0013] In some embodiments, the cesium compound is any one or more of cesium sulfate, cesium carbonate, and cesium nitrate.

[0014] cesium ion (Cs) + Because it has the largest ionic radius and the lowest electronegativity among all alkali metals, it can most effectively embed and modify the crystal structure of V₂O₅. Its mechanism of action is: strong polarization and weakening of the V=O double bond, thereby significantly reducing the V₂ content in the SO₂ oxidation reaction. 5+ / V 4+ The activation energy barrier of the redox cycle. This allows the catalyst to start up and perform catalytic cycling efficiently at relatively low temperatures.

[0015] In some embodiments, the phosphorus compound is any one or more of phosphoric acid, ammonium phosphate, and ammonium dihydrogen phosphate.

[0016] Phosphorus species can modify acidic sites on the catalyst surface, reducing excessive adsorption of SO3 at strong acid sites and promoting product desorption, thereby alleviating blockage of active sites and increasing reaction rates. Furthermore, Phosphorus can form more complex, thermally stable composite oxide phases or glassy molten phases with V and Cs, maintaining the stability of the active structure at operating temperatures.

[0017] There is a significant synergistic effect between phosphorus (P) and cerium (Cs). P species may act as a "bridge," promoting the uniform distribution and fixation of Cs around the active phase of V₂O₅, preventing the migration and volatilization of Cs during high-temperature calcination or reaction processes. This strong interaction between Cs and phosphorus (PV) constitutes a more stable and efficient active center than the traditional VK system or the addition of Cs or P alone.

[0018] In some embodiments, the potassium compound is any one or more of potassium sulfate, potassium carbonate, and potassium nitrate.

[0019] Potassium compounds, as auxiliary agents, K + Can be used with Cs + The formation of a composite alkali metal effect further optimizes the viscosity and fluidity of the molten phase, and in some cases can further fine-tune the activity and thermal stability.

[0020] In some embodiments, the method for preparing the modified diatomaceous earth includes the following steps: (1) Calcined diatomaceous earth is obtained by calcining it at 650~750℃ for 3~5h; (2) Mix the calcined diatomite from step (1) with deionized water and stir to disperse it evenly. Then add aniline, heat to 30~40℃, stir vigorously, then add dilute hydrochloric acid to adjust the pH to 3~4, continue stirring for 25~35min, then heat to 110~130℃ and stir for 25~28h, then cool to room temperature, wash with deionized water and ethanol, and dry to obtain modified diatomite.

[0021] This invention uses aniline as the main raw material to modify diatomaceous earth, resulting in a polyaniline intercalated modified diatomaceous earth. This modified diatomaceous earth serves as a carrier, where the aniline structure expands the spacing between the diatomaceous earth intercalations, thereby improving the load-bearing capacity of the modified diatomaceous earth. In addition, the π-π conjugation effect between the benzene rings improves the mechanical properties between the intercalations.

[0022] In some embodiments, the particle size of the diatomaceous earth is 800 nm to 1 μm.

[0023] In some embodiments, in step (2), the mass-to-volume ratio of the calcined diatomaceous earth to aniline is 1 g:(0.3~0.4) ml.

[0024] This invention improves the load-bearing capacity of modified diatomaceous earth by adjusting the mass-volume ratio of calcined diatomaceous earth to aniline.

[0025] Another aspect of the present invention provides a method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂, comprising the following steps: S1. Dissolve vanadium pentoxide in an aqueous oxalic acid solution and heat to 60~100℃ until clear to obtain a vanadium salt precursor solution; S2. Dissolve cesium compound, phosphorus compound and potassium compound in deionized water to obtain a composite additive solution; S3. Add the modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat and stir vigorously, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 1.5~2.5, continue stirring for 1~3 hours, concentrate under reduced pressure after completion to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 100~200℃ for 4~8 hours to obtain the catalyst.

[0026] In some embodiments, in step S3, the temperature of the heating is 80~85°C.

[0027] In some embodiments, in step S3, the stirring speed is 2000~3000 r / min.

[0028] Compared with the prior art, the present invention has the following beneficial effects: (1) The catalyst of the present invention is prepared by loading vanadium pentoxide, cesium compound, phosphorus compound and potassium compound as active components onto modified diatomite. The catalyst can not only improve the loading rate of active components, but also has higher mechanical properties and is not easy to break or pulverize.

[0029] (2) In this invention, aniline is used as the main raw material to modify diatomite, and a polyaniline intercalated modified diatomite is obtained. The modified diatomite is used as a carrier, wherein the aniline structure expands the spacing between the diatomite intercalation layers, thereby improving the load-bearing capacity of the modified diatomite. In addition, the π-π conjugation effect between benzene rings improves the mechanical properties between the intercalation layers.

[0030] (3) The present invention can improve the load-bearing capacity of modified diatomite by adjusting the mass-volume ratio of calcined diatomite to aniline.

[0031] (4) This invention introduces cesium (Cs) and phosphorus (P) as key synergistic co-catalysts to construct a V2O5-Cs-P-(K) multi-component synergistic active system. By precisely and narrowly controlling the key process parameters of the co-precipitation stage in the preparation process, the optimal distribution, combination and anchoring of active components on the diatomaceous earth support are achieved, thereby simultaneously realizing the low-temperature high activity and high strength performance of the catalyst. Attached Figure Description

[0032] Figure 1 The conversion rates of sulfur dioxide of the catalysts prepared in Examples 1-4 of this application at different temperatures are shown. Figure 2 The conversion rates of sulfur dioxide of the catalysts prepared in Examples 1 and 5-8 of this application at different temperatures; Figure 3 The conversion rates of sulfur dioxide of the catalysts prepared in Example 1 and Comparative Examples 1-2 of this application at different temperatures are shown. Detailed Implementation

[0033] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0034] Unless otherwise specified, the post-processing operations described below, such as "calcination", "stirring", "washing", "drying", "heating", and "depressurized concentration", can be selected by those skilled in the art based on actual conditions, and are not further limited.

[0035] Preparation Example 1 The preparation method of modified diatomaceous earth includes the following steps: (1) Calcine diatomaceous earth with a particle size of 900 nm was placed at 700℃ for 4 h to obtain calcined diatomaceous earth; (2) Mix 10g of calcined diatomaceous earth from step (1) with 200ml of deionized water and stir to disperse evenly. Then add 3ml of aniline, heat to 35℃, stir vigorously, then add 1mol / L dilute hydrochloric acid to adjust the pH to 3, continue stirring for 30min, then heat to 120℃ and stir for 27h, then cool to room temperature, wash with deionized water and ethanol, and dry to obtain modified diatomaceous earth.

[0036] Preparation Example 2 The preparation method of modified diatomaceous earth is the same as that in Preparation Example 1, except that the amount of aniline added is 2 ml.

[0037] Preparation Example 3 The preparation method of modified diatomaceous earth is the same as that in Preparation Example 1, except that the amount of aniline added is 5 ml.

[0038] Example 1 A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ includes the following steps: S1. Dissolve 7g of vanadium pentoxide in 70ml of 5wt% oxalic acid aqueous solution, heat to 80℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 3g of cesium sulfate, 2g of phosphoric acid and 2g of potassium sulfate in 105ml of deionized water to obtain a composite auxiliary solution; S3. Add 86g of modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 83℃ and stir at 2500r / min, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 2 with 10wt% ammonia water, continue stirring for 2h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 150°C for 6 hours to obtain the catalyst.

[0039] The modified diatomaceous earth was prepared by Preparation Example 1.

[0040] Example 2 A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ includes the following steps: S1. Dissolve 5g of vanadium pentoxide in 50ml of 5wt% oxalic acid aqueous solution, heat to 60℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 5g of cesium sulfate, 3g of phosphoric acid and 1g of potassium sulfate in 135ml of deionized water to obtain a composite auxiliary solution; S3. Add 86g of modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 80℃ and stir at 2000r / min, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 1.5 with 10wt% ammonia water, continue stirring for 3h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 100°C for 8 hours to obtain the catalyst.

[0041] The modified diatomaceous earth was prepared by Preparation Example 1.

[0042] Example 3 A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ includes the following steps: S1. Dissolve 10g of vanadium pentoxide in 100ml of 5wt% oxalic acid aqueous solution, heat to 100℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 1g of cesium sulfate, 0.3g of phosphoric acid and 5g of potassium sulfate in 90ml of deionized water to obtain a composite auxiliary solution; S3. Add the modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 85℃ and stir at 3000r / min, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 2.5 with 10wt% ammonia water, continue stirring for 1h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 200°C for 4 hours to obtain the catalyst.

[0043] The modified diatomaceous earth was prepared by Preparation Example 1.

[0044] Example 4 A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ includes the following steps: S1. Dissolve 7g of vanadium pentoxide in 70ml of 5wt% oxalic acid aqueous solution, heat to 80℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 3g of cesium sulfate and 2g of phosphoric acid in 75ml of deionized water to obtain a composite auxiliary solution; S3. Add 88g of modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 83℃ and stir at 2500r / min, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 2 with 10wt% ammonia water, continue stirring for 2h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 150°C for 6 hours to obtain the catalyst.

[0045] The modified diatomaceous earth was prepared by Preparation Example 1.

[0046] Example 5 A method for preparing a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 is described. The specific implementation method is the same as in Example 1, except that the modified diatomaceous earth is prepared in Example 2.

[0047] Example 6 A method for preparing a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 is described. The specific implementation method is the same as in Example 1, except that the modified diatomaceous earth is prepared in Example 3.

[0048] Example 7 A method for preparing a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2, the specific implementation method is the same as in Example 1, except that the temperature in step S3 is 90℃.

[0049] Example 8 A method for preparing a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2, the specific implementation method is the same as in Example 1, except that the preparation method includes the following steps: S1. Dissolve 7g of vanadium pentoxide in 70ml of 5wt% oxalic acid aqueous solution, heat to 60℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 3g of cesium sulfate, 2g of phosphoric acid and 2g of potassium sulfate in 105ml of deionized water to obtain a composite auxiliary solution; S3. Add 86g of modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 80℃ and stir at 2500r / min, add the composite auxiliary agent solution in step S2, continue stirring for 3h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 100°C for 8 hours to obtain the catalyst.

[0050] The modified diatomaceous earth was prepared by Preparation Example 1.

[0051] Comparative Example 1 A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ includes the following steps: S1. Dissolve 8g of vanadium pentoxide in 80ml of 5wt% oxalic acid aqueous solution, heat to 80℃ until clear, and obtain vanadium salt precursor solution; S2. Dissolve 4g of potassium sulfate in 60ml of deionized water to obtain the auxiliary agent solution; S3. Add 88g of modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat to 83℃ and stir at 2500r / min, add the auxiliary agent solution in step S2, adjust the pH of the system to 2 with 10wt% ammonia water, continue stirring for 2h, and concentrate under reduced pressure to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 150°C for 6 hours to obtain the catalyst.

[0052] The modified diatomaceous earth was prepared by Preparation Example 1.

[0053] Comparative Example 2 A method for preparing a high-strength V2O5-based catalyst for low-temperature dry oxidation of SO2 is described. The specific implementation method is the same as in Example 1, except that diatomaceous earth is used instead of modified diatomaceous earth.

[0054] Performance testing: (1) Compressive strength: The radial compressive strength of the catalyst was tested using a particle strength tester; (2) Sulfur dioxide conversion rate: The test was conducted in accordance with the People's Republic of China Chemical Industry Standards HG / T2089-2014 (Experimental Method for Activity of Catalyst for Sulfur Dioxide Oxidation to Sulfuric Acid) and HG / T2086-2013 (Catalyst for Sulfur Dioxide Oxidation to Sulfuric Acid).

[0055] The catalysts of each embodiment and comparative example were tested according to the above test methods, and the test results are shown in Table 1.

[0056] Table 1 See Figures 1-3 According to the data in Table 1, the catalysts prepared in Examples 1-3 have good compressive strength and sulfur dioxide catalytic efficiency; the catalyst prepared in Example 4 has good catalytic effect at high temperature, but low catalytic efficiency at low temperature; in Example 5, due to the change in the mass-volume ratio of calcined diatomaceous earth to aniline, the decrease in aniline content led to a decrease in the intercalation support strength of diatomaceous earth and insignificant pore expansion, resulting in a decrease in compressive strength, catalyst loading, and conversion rate; in Example 6, due to the change in the mass-volume ratio of calcined diatomaceous earth to aniline, the catalytic performance did not improve with the increase of aniline addition. Significant changes were observed, but the mechanical properties actually decreased slightly due to the excessive expansion of the intercalation structure, and the catalytic efficiency was low at low temperatures. In Example 7, the compressive strength decreased slightly due to changes in the temperature control in the preparation method, and the catalytic efficiency was low at low temperatures. In Example 8, the conversion rate and compressive strength of sulfur dioxide decreased due to the lack of pH control in the preparation method. In Comparative Example 1, the conversion rate and compressive strength of sulfur dioxide decreased due to changes in the raw materials of the active component. In Comparative Example 2, the conversion rate and compressive strength of sulfur dioxide decreased due to the use of diatomaceous earth instead of modified diatomaceous earth.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂, characterized in that, The composition comprises, by mass percentage, 5-10% vanadium pentoxide, 1-5% cesium compounds (Cs₂O), 0.5-3% phosphorus compounds (P₂O₅), 0-5% potassium compounds (K₂O), and the balance being modified diatomaceous earth.

2. The high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 1, characterized in that, The cesium compound is any one or more of cesium sulfate, cesium carbonate, and cesium nitrate.

3. The high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 1, characterized in that, The phosphorus compound is any one or more of phosphoric acid, ammonium phosphate, and ammonium dihydrogen phosphate.

4. The high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 1, characterized in that, The potassium compound is any one or more of potassium sulfate, potassium carbonate, and potassium nitrate.

5. A high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 1, characterized in that, The method for preparing the modified diatomaceous earth includes the following steps: (1) Calcined diatomaceous earth is obtained by calcining it at 650~750℃ for 3~5h; (2) Mix the calcined diatomite from step (1) with deionized water and stir to disperse it evenly. Then add aniline, heat to 30~40℃, stir vigorously, then add dilute hydrochloric acid to adjust the pH to 3~4, continue stirring for 25~35min, then heat to 110~130℃ and stir for 25~28h, then cool to room temperature, wash with deionized water and ethanol, and dry to obtain modified diatomite.

6. A high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 5, characterized in that, The particle size of the diatomaceous earth is 800 nm to 1 μm.

7. A high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 5, characterized in that, In step (2), the mass-to-volume ratio of calcined diatomaceous earth to aniline is 1 g:(0.3~0.4) ml.

8. A method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. Dissolve vanadium pentoxide in an aqueous oxalic acid solution and heat to 60~100℃ until clear to obtain a vanadium salt precursor solution; S2. Dissolve cesium compound, phosphorus compound and potassium compound in deionized water to obtain a composite additive solution; S3. Add the modified diatomaceous earth to the vanadium salt precursor solution in step S1, stir evenly, heat and stir vigorously, add the composite auxiliary agent solution in step S2, adjust the pH of the system to 1.5~2.5, continue stirring for 1~3 hours, concentrate under reduced pressure after completion to obtain a paste. S4. The paste from step S3 is extruded into a mold and then calcined at 100~200℃ for 4~8 hours to obtain the catalyst.

9. The method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 8, characterized in that, In step S3, the temperature for heating is 80~85℃.

10. The method for preparing a high-strength V₂O₅-based catalyst for low-temperature dry oxidation of SO₂ according to claim 8, characterized in that, In step S3, the stirring speed is 2000~3000 r / min.

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