Vanadium-based catalyst for conversion of sulfur dioxide in waste acid treatment and preparation method thereof

Abstract

The present application relates to the technical field of catalyst, in particular to a vanadium-based catalyst for conversion of sulfur dioxide in waste acid treatment and a preparation method thereof, the vanadium-based catalyst comprises vanadium pentoxide, potassium sulfate, sodium sulfate, an auxiliary agent, a low-temperature promoter and a carrier, wherein the carrier is functionally modified diatomite, the vanadium-based catalyst prepared by the present application has high activity, high stability and strong anti-pulverization, and has excellent applicability in the conversion process of sulfur dioxide in waste acid treatment.

Description

Technical Field

[0001] This invention relates to the field of catalyst technology, and in particular to a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method. Background Technology

[0002] In industrial production, the large quantities of waste acid generated pose a serious threat to the environment. Taking alkylation processes as an example, the waste sulfuric acid produced after the reaction of the sulfuric acid catalyst contains 8%-14% polymeric oil and water, is a dark reddish-brown gel, is unstable, and has a foul odor. A medium-sized alkylation unit can generate thousands to tens of thousands of tons of this type of waste acid annually. Similar situations are common in industries such as oil refining, chemicals, and metallurgy. For example, the pickling process in petroleum refining and the acid leaching process in non-ferrous metal smelting both produce complex waste acids containing impurities.

[0003] Currently, there are various methods for treating waste acid, but each has its limitations. For sulfuric acid alkylation waste acid, high-temperature thermal cracking is widely used, but it has drawbacks such as high requirements for equipment materials and complex processes; a single unit with an annual processing capacity of 10,000 tons often requires an investment exceeding 100 million yuan, hindering its widespread adoption. Alternative methods using waste acid to produce silica, rust inhibitors, or ammonium sulfate, while relatively simpler and with lower investment, can lead to secondary pollution due to the difficult-to-treat polymeric oils. Most refineries choose to introduce waste acid into sulfur recovery units for treatment; however, the organic matter and iron ions in the waste acid can cause catalyst carbon buildup, decreased activity, and accelerated equipment corrosion.

[0004] The development of the semiconductor industry, accompanied by the shrinking of device size and the increase in integration, has led to a sharp increase in the generation of SPM waste acid (sulfuric acid content 40%-85%, hydrogen peroxide content 3%-10%). Residual hydrogen peroxide poses challenges for subsequent treatment. Existing treatment technologies, such as adding metal ion catalysts, suffer from high costs for subsequent impurity removal and difficulties in catalyst recovery; using reducing agents easily generates sulfur dioxide pollution and is costly; activated carbon methods face challenges of limited catalytic activity and susceptibility to poisoning and deactivation; and photocatalysis technology has a long processing cycle and low efficiency.

[0005] In the field of chemical synthesis, waste sulfuric acid containing large amounts of residual organic matter after reactions is classified as hazardous waste, and its treatment is costly. Evaporation and concentration of dilute sulfuric acid for reuse is one feasible approach, but during the evaporation process, low-boiling-point organic compounds volatilize and require additional treatment, while high-boiling-point organic compounds may carbonize, affecting the quality of the sulfuric acid. Other methods, such as catalytic oxidation to decompose organic matter followed by evaporation, may produce harmful gases; neutralization followed by calcination has high energy consumption and low product added value; while methods such as incineration absorption, dilution hydrolysis, rising film evaporation separation, autocatalytic oxidation, or the production of polyferric sulfate generally suffer from complex processes, high reagent consumption, high energy consumption, or limited value of recovered products, thus limiting their application potential.

[0006] With increasingly stringent environmental protection requirements, the "Emission Standard of Pollutants for Petroleum Refining Industry (GB31570-2015)," implemented in 2015, clearly stipulates that the sulfur dioxide emission concentration limit for flue gas from sulfur recovery units in general areas is below 400 mg / Nm³, and in key areas it is below 100 mg / Nm³. The total emission amount is also included in environmental verification indicators. Newly built units must comply with the standard from the date of its promulgation, while existing units must comply from July 1, 2017. In traditional waste acid treatment processes, the iron-removing scale-holding agent loaded to protect the Claus catalyst reduces the amount of main catalyst used, leading to a decrease in overall conversion rate (especially organic sulfur conversion rate), making it difficult to meet sulfur dioxide emission standards. Furthermore, this protective agent has limited scale-holding capacity; high impurity content can easily cause it to fail, affecting the stable operation of the unit and even triggering unplanned shutdowns. Since it is loaded inside the reactor, any problems require shutdown for maintenance, posing operational risks. Invention patent CN111065458B discloses a vanadium-based catalyst, comprising: an active phase supported on a support, the active phase including vanadium oxide, potassium sulfate, sodium sulfate, and additives; the support including macroporous silica and diatomaceous earth; the macroporous silica having an average pore size of 100-500 nm; and the diatomaceous earth being refined diatomaceous earth with a silica content of over 85%. The vanadium-based catalyst achieves a maximum SO2 conversion rate of 67.8% at 440℃. However, facing the multiple challenges of complex industrial waste acid composition, high treatment costs, low efficiency, and stringent environmental regulations, it is still necessary to develop vanadium-based catalysts with higher activity. In particular, when facing complex working conditions such as airflow impact and sudden temperature changes in waste acid treatment, higher requirements are placed on the catalyst's resistance to pulverization and stability. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention prepares a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment, which has excellent properties such as high activity, high stability and strong resistance to pulverization, and has excellent applicability to sulfur dioxide conversion processes in waste acid treatment.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention provides a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment. The vanadium-based catalyst includes vanadium pentoxide, potassium sulfate, sodium sulfate, additives, low-temperature promoters and a support, wherein the support is functionally modified diatomaceous earth.

[0010] In some embodiments of the present invention, based on the total mass of the vanadium-based catalyst (100%), the amount of vanadium pentoxide is 6.5~8.0 wt%; the molar ratio of potassium to vanadium in potassium sulfate (K2O / V2O5) is (3.0~3.5):1; the amount of sodium sulfate is 3.0~5.0 wt%; the amount of additives is 0.5~3.0 wt%; the amount of low-temperature accelerator is 4~15 wt%; and the balance is a carrier.

[0011] This invention ensures that the vanadium-based catalyst has sufficient active centers by controlling the vanadium pentoxide content, thereby reducing costs and avoiding adverse effects on the performance of other components. At the same time, potassium sulfate is generated, and by adjusting the molar ratio of potassium to vanadium, excellent synergistic catalytic performance between potassium sulfate and vanadium pentoxide is achieved. The addition of sodium sulfate helps to regulate the acidity and thermal stability of the catalyst, maintaining the stability of the catalyst structure in the complex environment of waste acid treatment.

[0012] In some embodiments of the present invention, the auxiliary agent is phosphorus oxide and / or cesium sulfate.

[0013] Preferably, the additive is a mixture of phosphorus oxide and cesium sulfate.

[0014] In some embodiments of the present invention, the low-temperature accelerator is at least one of sodium salt, phosphorus-containing compound, and soluble cesium compound.

[0015] Preferably, the sodium salt is sodium carbonate.

[0016] Preferably, the soluble cesium compound is a 50 wt% CsOH solution.

[0017] Preferably, the phosphorus-containing compound is phosphoric acid.

[0018] This invention preferably incorporates phosphorus oxide and cesium sulfate as additives. Phosphorus oxide improves the acidity distribution on the catalyst surface, enhancing its adsorption and conversion capacity for sulfur dioxide. Cesium sulfate enhances the low-temperature activity of the catalyst, lowers the ignition temperature, and enables the catalyst to effectively catalyze the conversion of sulfur dioxide at lower temperatures. Simultaneously, the addition of the low-temperature promoter synergistically improves the low-temperature activity of the catalyst, lowers the ignition temperature, and broadens the applicable temperature range of the catalyst. This allows the vanadium-based catalyst to maintain high activity over a wide temperature range of 380–600°C, and especially achieves rapid and efficient conversion of low-concentration sulfur dioxide in waste acid to sulfur trioxide in the low-temperature range of 380–450°C, significantly improving conversion efficiency.

[0019] In some embodiments of the present invention, the method for preparing the functionally modified diatomite includes the following steps:

[0020] (1) Spray aluminate evenly onto diatomaceous earth, let it stand for 1 to 1.5 hours, and then transfer it to 120 to 140°C for 0.5 to 1 hour to obtain pretreated diatomaceous earth;

[0021] (2) Mix isooctyltrichlorosilane and water, treat at 20~30℃ for 1~2h, then add hexadecylpyridine bromide and mix, continue heating to 30~35℃ and stirring for 0.5~1h to obtain the modifier;

[0022] (3) Add the pretreated diatomaceous earth from step (1) and the modifier from step (2) into an ethanol solution, stir at 30-40°C for 3-5 hours, and then wash and dry to obtain the functional modified diatomaceous earth.

[0023] In some embodiments of the present invention, the mass ratio of aluminate to diatomite in step (1) is (0.08~0.1):1.

[0024] In some embodiments of the present invention, the mass ratio of the pretreated diatomaceous earth, isooctyltrichlorosilane, and hexadecylpyridine bromide is 1:(0.2~0.4):(0.08~0.1).

[0025] This invention first pre-treats diatomaceous earth, which may cause the amorphous SiO2 in the pre-treated diatomaceous earth to undergo a crystal transformation into stable crystalline SiO2, thereby improving the hydrothermal stability of the support. On the other hand, the introduction of more micropores and mesopores may not only improve the structural stability of diatomaceous earth but also increase its specific surface area, promoting the dispersion of catalyst active components such as vanadium pentoxide, potassium sulfate, and sodium sulfate on the support, thus improving catalytic activity. Furthermore, this invention also prepares a modifier by using hexadecylpyridine bromide and isooctyltrichlorosilane, and then mixes it with the pre-modified diatomaceous earth to obtain functional modified diatomaceous earth with excellent flowability, dispersibility, and hydrothermal stability. The applicant speculates that the agglomeration of the support may be reduced, and during high-temperature calcination, the disappearance of organic matter on its surface forms a "pore-forming + nitrogen and carbon doping" effect, which further promotes the catalytic activity and structural stability of the vanadium-based catalyst. When facing complex working conditions such as airflow impact and sudden temperature changes in waste acid treatment, it avoids the pulverization and loss of vanadium-based catalyst due to mechanical damage, ensuring stable and reliable performance in long-term operation.

[0026] A second aspect of the present invention also provides a method for preparing a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment, comprising the following steps:

[0027] S1: Mix potassium hydroxide, vanadium pentoxide, and water to obtain vanadium water, then add sulfuric acid to react and obtain a mixture of vanadium pentoxide and potassium sulfate;

[0028] S2: Mix the low-temperature accelerator and the mixture from step S1 again to obtain a second mixture;

[0029] S3: The second mixture from step S2, sodium sulfate, additives, and carrier are thoroughly mixed to obtain a homogeneous plastic, which is then extruded, dried at 100-120°C for 2-3 hours, and calcined at 550-650°C for 3-4 hours to obtain the vanadium-based catalyst.

[0030] In some embodiments of the present invention, the extruded strip is cylindrical with a diameter of 3-5 mm and a length of 5-10 mm.

[0031] In some embodiments of the present invention, steam is introduced during the roasting process, and the steam flow rate is 0.5~1.0L / min.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The vanadium-based catalyst prepared by the present invention has high activity, high stability and strong resistance to pulverization, and has excellent applicability in the sulfur dioxide conversion process in waste acid treatment.

[0034] (2) By controlling the vanadium pentoxide content, the present invention ensures that the vanadium-based catalyst has sufficient active centers, reduces costs, and avoids adverse effects on the performance of other components. At the same time, potassium sulfate is added and the molar ratio of potassium to vanadium is adjusted by controlling the mass ratio, so that potassium sulfate and vanadium pentoxide can exert excellent synergistic catalytic performance. The addition of sodium sulfate helps to adjust the acidity and thermal stability of the catalyst and maintain the stability of the catalyst structure in the complex environment of waste acid treatment.

[0035] (3) In this invention, phosphorus oxide and cesium sulfate are preferably added as additives. Phosphorus oxide can improve the acidity distribution on the catalyst surface and enhance the adsorption and conversion capacity of sulfur dioxide. Cesium sulfate can enhance the low-temperature activity of the catalyst and reduce the ignition temperature, so that the catalyst can effectively catalyze the conversion of sulfur dioxide at a lower temperature. At the same time, the addition of the low-temperature promoter also synergistically improves the low-temperature activity of the catalyst, reduces the ignition temperature, and broadens the applicable temperature range of the catalyst.

[0036] (4) In this invention, diatomaceous earth is first pretreated to form a solid framework from crystalline SiO2. Then, a modifier is prepared by hexadecylpyridine bromide and isooctyltrichlorosilane and mixed with the pre-modified diatomaceous earth. The resulting functional modified diatomaceous earth has excellent fluidity, dispersibility and hydrothermal stability, which further enhances the catalytic activity and structural stability of vanadium-based catalysts. When facing complex working conditions such as airflow impact and sudden temperature changes in waste acid treatment, the vanadium-based catalyst is prevented from being pulverized and lost due to mechanical damage, ensuring stable and reliable performance during long-term operation. Detailed Implementation

[0037] The present invention will be described below with reference to specific embodiments. It should be noted that the following embodiments are examples of the present invention and are used only to illustrate the invention, not to limit it. Other combinations and various modifications within the scope of the present invention can be made without departing from its spirit or scope.

[0038] Unless otherwise specified, the compound raw materials and related reagents used in the following specific embodiments can be purchased from the market. The auxiliary agent used is a mixture of phosphorus oxide and cesium sulfate in a mass ratio of 1:4; the low temperature accelerator used is a mixture of sodium carbonate and 50wt% CsOH solution in a mass ratio of 1.5:1.

[0039] Preparation Example 1

[0040] The preparation method of functionally modified diatomaceous earth includes the following steps:

[0041] (1) Spray 150 mL of an aqueous solution containing 8.5 g of sodium aluminate evenly onto 100 g of diatomaceous earth, let it stand for 1.2 h, and then transfer it to 130 °C for 0.8 h to obtain pretreated diatomaceous earth;

[0042] (2) Mix 6g of isooctyltrichlorosilane and 4g of water, treat at 25°C for 1.5h, then add 1.8g of hexadecylpyridine bromide and mix by shaking, continue heating to 32°C and stirring for 0.8h to obtain the modifier;

[0043] (3) Add 20g of the pretreated diatomaceous earth from step (1) and all the modifiers from step (2) to 50mL of 65wt% ethanol solution, stir at 30℃ for 1.2h, and then wash and dry to obtain the functional modified diatomaceous earth.

[0044] Preparation Example 2

[0045] The preparation method of functional modified diatomite is the same as that in preparation example 1, except that the amount of sodium aluminate added in step (1) is 10.5g.

[0046] Preparation Example 3

[0047] The preparation method of functional modified diatomite is the same as that in preparation example 1, except that the amount of isooctyltrichlorosilane added in step (2) is 9g.

[0048] Preparation Example 4

[0049] The preparation method of functional modified diatomaceous earth is the same as that in preparation example 1, except that the modifier added in step (3) is 1.8g of hexadecylpyridine bromide.

[0050] Preparation Example 5

[0051] The preparation method of functionally modified diatomaceous earth includes the following steps:

[0052] 150 mL of an aqueous solution containing 8.5 g of sodium aluminate was evenly sprayed onto 100 g of diatomaceous earth, left to stand for 1.2 h, and then transferred to 130 °C for 0.8 h to obtain functional modified diatomaceous earth.

[0053] Example 1

[0054] A method for preparing a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment includes the following steps:

[0055] S1: Dissolve potassium hydroxide with steam, mix it with vanadium pentoxide and water, and boil it at 85°C for 2.5 hours to obtain vanadium water. Then add 1+1 sulfuric acid solution to react and obtain a mixture of vanadium pentoxide and potassium sulfate.

[0056] S2: Mix the low-temperature accelerator and the mixture from step S1 again to obtain a second mixture;

[0057] S3: The second mixture from step S2, sodium sulfate, additives, and functionally modified diatomaceous earth are thoroughly mixed to obtain a homogeneous plastic, which is then extruded, dried at 110°C for 2.5 hours, and calcined at 600°C for 3.5 hours to obtain the vanadium-based catalyst.

[0058] Of which, the total mass of the vanadium-based catalyst is 100g, the amount of vanadium pentoxide is 7.5wt%; the molar ratio of potassium to vanadium in potassium sulfate is 3.2:1 (K2O / V2O5); the amount of sodium sulfate is 4wt%; the amount of additives is 2.5wt%; the amount of low-temperature accelerator is 8wt%; and the balance is functional modified diatomaceous earth.

[0059] The extruded shapes are all cylindrical with a diameter of 4mm and a length of 8mm;

[0060] Steam is introduced during roasting at a flow rate of 0.7 L / min.

[0061] The functionally modified diatomaceous earth in this embodiment was obtained from Preparation Example 1.

[0062] Example 2

[0063] A method for preparing a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment includes the following steps:

[0064] S1: Dissolve potassium hydroxide with steam, mix it with vanadium pentoxide and water, and boil it at 85°C for 2.5 hours to obtain vanadium water. Then add 1+1 sulfuric acid solution to react and obtain a mixture of vanadium pentoxide and potassium sulfate.

[0065] S2: Mix the low-temperature accelerator and the mixture from step S1 again to obtain a second mixture;

[0066] S3: The second mixture from step S2, sodium sulfate, additives, and functionally modified diatomaceous earth are thoroughly mixed to obtain a homogeneous plastic, which is then extruded, dried at 110°C for 2.5 hours, and calcined at 600°C for 3.5 hours to obtain the vanadium-based catalyst.

[0067] Of which, the total mass of the vanadium-based catalyst is 100g, the amount of vanadium pentoxide is 6.5wt%; the molar ratio of potassium to vanadium in potassium sulfate is 3.2:1 (K2O / V2O5); the amount of sodium sulfate is 3.0wt%; the amount of additives is 0.5wt%; the amount of low-temperature accelerator is 4wt%; and the balance is functional modified diatomaceous earth.

[0068] The extruded shapes are all cylindrical with a diameter of 4mm and a length of 8mm;

[0069] Steam is introduced during roasting at a flow rate of 0.7 L / min.

[0070] The functionally modified diatomaceous earth in this embodiment was obtained from Preparation Example 1.

[0071] Example 3

[0072] A method for preparing a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment includes the following steps:

[0073] S1: Dissolve potassium hydroxide with steam, mix it with vanadium pentoxide and water, and boil it at 85°C for 2.5 hours to obtain vanadium water. Then add 1+1 sulfuric acid solution to react and obtain a mixture of vanadium pentoxide and potassium sulfate.

[0074] S2: Mix the low-temperature accelerator and the mixture from step S1 again to obtain a second mixture;

[0075] S3: The second mixture from step S2, sodium sulfate, additives, and functionally modified diatomaceous earth are thoroughly mixed to obtain a homogeneous plastic, which is then extruded, dried at 110°C for 2.5 hours, and calcined at 600°C for 3.5 hours to obtain the vanadium-based catalyst.

[0076] Of which, the total mass of the vanadium-based catalyst is 100g, the amount of vanadium pentoxide is 8.0wt%; the potassium and vanadium elements of potassium sulfate are calculated as K2O / V2O5 with a molar ratio of 3.2:1; the amount of sodium sulfate is 5.0wt%; the amount of additives is 3.0wt%; the amount of low-temperature accelerator is 15wt%; and the balance is functional modified diatomaceous earth.

[0077] The extruded shapes are all cylindrical with a diameter of 4mm and a length of 8mm;

[0078] Steam is introduced during roasting at a flow rate of 0.7 L / min.

[0079] The functionally modified diatomaceous earth in this embodiment was obtained from Preparation Example 1.

[0080] Example 4

[0081] A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the functionally modified diatomaceous earth in this example is obtained from Preparation Example 2.

[0082] Example 5

[0083] A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the functionally modified diatomaceous earth in this example is obtained from Preparation Example 3.

[0084] Example 6

[0085] A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the functionally modified diatomaceous earth in this example is obtained from Preparation Example 4.

[0086] Example 7

[0087] A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that the functionally modified diatomaceous earth in this example is obtained from Preparation Example 5.

[0088] Comparative Example 1

[0089] A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment and its preparation method are disclosed. The specific implementation method is the same as that in Example 1, except that conventional diatomaceous earth is used to replace the functional modified diatomaceous earth in an equal amount in this comparative example.

[0090] Performance testing

[0091] The vanadium-based catalysts prepared in each example and comparative example were used to simulate the reaction of sulfur dioxide to sulfur trioxide under a waste acid environment. The specific tests are as follows:

[0092] (1) Sulfur dioxide conversion rate: Refer to the Chinese chemical industry standard "HG / T 2089" The method specified in "Experimental Method for Activity of Catalyst for Oxidation of Sulfur Dioxide to Sulfuric Acid (2014)" involves preparing vanadium-based catalysts obtained in each example into samples with a particle size of φ5×5~8mm and loading them into the reactor (sample volume: 30mL). After ensuring airtightness, the reactor is turned on for the experiment. The temperature is initially increased at a rate of 3°C per minute. After 60 minutes, dry air is introduced, and the space velocity is controlled at approximately 3600 h⁻¹. -1After another 45 minutes, high-purity sulfur dioxide was introduced, controlling the sulfur dioxide volume fraction to approximately 10%. The temperature was then increased to 600℃ at a rate of 3℃ per minute for 5 hours. After reaching the heat resistance time, the temperature was decreased to the activation temperature of 410℃ at a rate of 200℃ / h and stabilized for 1 hour. The concentrations of SO2 at the inlet and outlet were measured using iodometric titration. Finally, the SO2 conversion rate (E) was calculated using the following formula: where Vin is the SO2 inlet volume fraction and Vout is the SO2 outlet volume fraction.

[0093] E=(Vin-Vout) / (Vin×(1-0.015Vout))

[0094] (2) Wear rate: The wear rate of fertilizer catalysts was determined in accordance with the HG / T 2976 method for determining wear rate.

[0095] The test results are shown in Table 1 below:

[0096] Table 1

[0097]

[0098] As shown in Table 1, the vanadium-based catalysts obtained in Examples 1-3 of this invention have significant advantages in terms of sulfur dioxide conversion rate and attrition rate. A comparison between Example 4 and Example 1 shows that changing the amount of sodium aluminate added in step (1) may lead to excessive occupation of the macropores in the diatomaceous earth, resulting in a decrease in the catalytic activity of the vanadium-based catalyst. A comparison between Example 5 and Example 1 shows that changing the amount of isooctyltrichlorosilane may lead to changes in structural strength, making the vanadium-based catalyst prone to pulverization and reducing its attrition resistance. Furthermore, improper coverage of active sites also negatively impacts catalytic activity. The conversion rate of sulfur dioxide decreased; a comparison between Example 6 and Example 1 shows that when hexadecylpyridine bromide is used as a modifier, the vanadium-based catalyst may be affected by the dispersion uniformity and modification effect, which in turn affects the catalytic activity and stability, and the wear rate decreased significantly; a comparison between Example 7 and Example 1 shows that when the pretreated diatomaceous earth is not further modified with a modifier, the catalytic activity and stability of the vanadium-based catalyst decreased to varying degrees due to the influence of the framework structure strength and dispersion; a comparison between Comparative Example 1 and Example 1 shows that using only conventional diatomaceous earth as a support results in insufficient catalytic activity and stability.

[0099] The above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment, characterized in that, The vanadium-based catalyst comprises vanadium pentoxide, potassium sulfate, sodium sulfate, additives, a low-temperature promoter, and a support, wherein the support is functionally modified diatomaceous earth. The auxiliary agent is phosphorus oxide and / or cesium sulfate; The low-temperature accelerator is at least one of sodium carbonate, phosphoric acid, and 50 wt% CsOH solution; The preparation method of the functionally modified diatomite includes the following steps: (1) Spray aluminate evenly onto diatomaceous earth, let it stand for 1 to 1.5 hours, and then transfer it to 120 to 140°C for 0.5 to 1 hour to obtain pretreated diatomaceous earth; (2) Mix isooctyltrichlorosilane and water, treat at 20~30℃ for 1~2h, then add hexadecylpyridine bromide, continue heating to 30~35℃ and stirring for 0.5~1h to obtain the modifier; (3) Add the pretreated diatomaceous earth from step (1) and the modifier from step (2) into an ethanol solution, stir at 30-40°C for 3-5 hours, and then wash and dry to obtain the functional modified diatomaceous earth.

2. The vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to claim 1, characterized in that, Based on the total mass of the vanadium-based catalyst (100%), the amount of vanadium pentoxide is 6.5~8.0 wt%; the molar ratio of potassium to vanadium in potassium sulfate (K2O / V2O5) is (3.0~3.5):1; the amount of sodium sulfate is 3.0~5.0 wt%; the amount of additives is 0.5~3.0 wt%; the amount of low-temperature accelerator is 4~15 wt%; and the balance is the carrier.

3. The vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to claim 1, characterized in that, The mass ratio of aluminate to diatomite in step (1) is (0.08~0.1):

1.

4. The vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to claim 1, characterized in that, The mass ratio of the pretreated diatomaceous earth, isooctyltrichlorosilane, and hexadecylpyridine bromide is 1:(0.2~0.4):(0.08~0.1).

5. A method for preparing a vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to any one of claims 1-4, characterized in that, Includes the following steps: S1: Mix potassium hydroxide, vanadium pentoxide, and water to obtain vanadium water, then add sulfuric acid to react and obtain a mixture of vanadium pentoxide and potassium sulfate; S2: Mix the low-temperature accelerator and the mixture from step S1 again to obtain a second mixture; S3: The second mixture from step S2, sodium sulfate, additives, and carrier are thoroughly mixed to obtain a homogeneous plastic, which is then extruded, dried at 100-120°C for 2-3 hours, and calcined at 550-650°C for 3-4 hours to obtain the vanadium-based catalyst.

6. The vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to claim 5, characterized in that, The extruded strip is cylindrical with a diameter of 3-5 mm and a length of 5-10 mm.

7. The vanadium-based catalyst for sulfur dioxide conversion in waste acid treatment according to claim 5, characterized in that, Steam is introduced during the roasting process, with a steam flow rate of 0.5~1.0 L / min.

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