A catalyst for sulfuric acid production

Abstract

The present invention belongs to the field of chemical technology, and specifically relates to a catalyst for sulfuric acid production. By doping samarium into a vanadium catalyst, the present invention effectively improves the vanadium catalyst's ability to absorb oxygen, which is beneficial for improving the catalytic activity and low-temperature activity of the vanadium catalyst. Modified diatomaceous earth and a mesoporous material are used to form a carrier, which can improve the dispersion of active components on the catalyst, thereby improving the catalytic activity of the catalyst. The diatomaceous earth is modified using a dilute sulfuric acid solution under ultrasonic conditions to increase the specific surface area of ​​the diatomaceous earth, thereby improving the catalytic activity of the vanadium catalyst. The vanadium catalyst is prepared by an impregnation method, which effectively avoids the problem of uneven dispersion of active components caused by the mixing and grinding method, thereby improving the catalytic activity of the catalyst.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical industry, and particularly relates to a catalyst for sulfuric acid production. Background Art

[0002] Vanadium catalyst is an indispensable chemical material in the contact process of sulfuric acid production. With the acceleration of my country's industrialization process, the scale and capacity of sulfuric acid production have increased rapidly. At the same time, as environmental protection requirements are becoming increasingly stringent, reducing the emission of SO2 in sulfuric acid production tail gas has become a focus of attention and research. This has also led to increasing performance requirements for vanadium catalysts used in sulfuric acid production.

[0003] The existing method for preparing vanadium catalysts involves dissolving potassium hydroxide in a reactor using steam, adding vanadium pentoxide to produce vanadium water, and then neutralizing it with dilute sulfuric acid to prepare the catalyst active material. This is then mixed and dispersed with diatomaceous earth, alkali metal sulfates, sulfur powder, and other materials, extruded into strips, and dried and calcined to produce the final vanadium catalyst product. However, vanadium catalysts only exhibit high catalytic activity above 430°C. This is because at low temperatures, the active components in the vanadium catalyst react with SO2, and too low a temperature prevents the side reaction product, vanadyl sulfate, from decomposing into pentavalent vanadium compounds, sulfur dioxide, and sulfur trioxide. This contributes to the high ignition temperature and poor low-temperature activity of traditional vanadium catalysts. Furthermore, impurities such as Al, Fe, and Ca in the diatomaceous earth are distributed on its surface and within its pores, blocking some of the pores. This hinders the adsorption and diffusion of active components on the surface and within its pores during the catalyst manufacturing process. The clogged pores in the catalyst reduce the utilization rate of the internal surface. When participating in the reaction, SO2 and O2 cannot diffuse into the channel for deep oxidation reaction. At the same time, the formed SO3 cannot be removed in time. The obstruction of gas inlet and outlet directly leads to a decrease in catalytic activity.

[0004] Chinese patent application publication number CN111036242A discloses a vanadium-based catalyst for wet-process sulfuric acid production. The catalyst comprises vanadium oxide, potassium sulfate, sodium sulfate, and an auxiliary agent supported on a carrier, wherein the auxiliary agent is selected from at least one of phosphorus oxide and cesium sulfate, and the carrier comprises diatomaceous earth. The catalyst is prepared by adding the auxiliary agent to the diatomaceous earth and subjecting it to hydrothermal treatment, causing the amorphous SiO2 in the diatomaceous earth to undergo a crystal transformation, converting it into a crystalline SiO2 with good stability, thereby obtaining a synthetic carrier with hydrothermal stability. However, at low temperatures, the active component of this vanadium-based catalyst reacts with SO2, which is detrimental to the decomposition of vanadyl sulfate, a side reaction product, resulting in poor low-temperature activity. Chinese patent application publication number CN110624570A discloses a method for preparing a low-temperature catalyst for wet-process vanadium sulfate production. Specifically, silica sol is added to the catalyst active phase, which is then mixed with an alkali metal sulfate, auxiliary agent, and refined diatomaceous earth in a roller, uniformly mixed, and compacted. The catalyst is then extruded, dried, and calcined to form a finished catalyst. The catalyst prepared by this method has the characteristics of resistance to pulverization, high strength, and stable activity. However, the structure of diatomaceous earth will be destroyed during the rolling process, and the impurities in the diatomaceous earth will block the pore structure of the diatomaceous earth, resulting in a sharp decrease in the amount of active ingredients adsorbed by the diatomaceous earth, so the catalytic activity of the catalyst is low. Summary of the Invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art such as poor low-temperature activity and low catalytic activity of the catalyst, the purpose of the present invention is to provide a catalyst for sulfuric acid production.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows:

[0007] A catalyst for sulfuric acid production is prepared by the following steps:

[0008] S1: Dissolve potassium hydroxide in deionized water, stir well, heat, add vanadium pentoxide and sodium sulfate, stir well, and obtain solution I;

[0009] S2: Add concentrated sulfuric acid to the solution I obtained in step S1 under stirring, adjust the pH value of the solution to 2-4, and add Sm(NO3)3·6H2O to obtain solution II;

[0010] S3: Add modified diatomaceous earth and mesoporous material to solution II obtained in step S2, stir evenly, ultrasonicate, shape, dry, and calcine to obtain a catalyst for sulfuric acid production; the mesoporous material is composed of mesoporous silica and mesoporous carbon in a mass ratio of 9-12:4-7.

[0011] The main role of vanadium catalyst in the catalytic oxidation reaction of sulfur dioxide is to act as a bridge by absorbing oxygen and sulfur dioxide, so that sulfur dioxide and oxygen react. The key role is played by V 5+ And surface chemical adsorption of oxygen. The present invention dopes samarium element into the vanadium catalyst. Samarium element is a variable valence element. Its oxide has a good oxygen storage capacity when it is rich in oxygen and can release oxygen when it is poor in oxygen. Therefore, the use of samarium element for doping can effectively improve the ability of the vanadium catalyst to adsorb oxygen, which is beneficial to improving the catalytic activity of the vanadium catalyst. In addition, samarium element has excellent activity at low temperatures. The doping of samarium element can also solve the technical problem of low low-temperature activity of vanadium catalyst. The present invention uses modified diatomaceous earth and mesoporous material to form a carrier, which can improve the dispersion of active components on the catalyst. The vanadium catalyst is prepared by impregnation method, which effectively avoids the problem of uneven dispersion of active components caused by the mixing and grinding method, thereby improving the catalytic activity of the catalyst.

[0012] Furthermore, the preparation method of the modified diatomaceous earth in step S3 is: adding dry diatomaceous earth to a dilute sulfuric acid solution, performing ultrasonic treatment under stirring, filtering, drying, and grinding to obtain the modified diatomaceous earth.

[0013] In the present invention, diatomaceous earth is modified by using a dilute sulfuric acid solution under ultrasonic conditions. Studies have found that under ultrasonic conditions, the dilute sulfuric acid solution can react with iron impurities in the diatomaceous earth to expand the pores, thereby increasing the specific surface area of ​​the diatomaceous earth. The vanadium catalyst prepared by using the modified diatomaceous earth has an increased adsorption capacity for active ingredients, and the catalytic activity of the vanadium catalyst is improved.

[0014] Furthermore, in the preparation method of modified diatomaceous earth, the mass ratio of diatomaceous earth to dilute sulfuric acid solution is 1:4-6, the concentration of the dilute sulfuric acid solution is 3-4 mol / L; the frequency of the ultrasonic treatment is 500-550 kHz, and the ultrasonic treatment time is 30-40 min.

[0015] Furthermore, the preparation method of the mesoporous silica in step S3 is: dissolving tetramethylammonium hydroxide in amyl alcohol, adding ammonia water and ether, stirring evenly, adding tetramethyl silicate dropwise, stirring to react, filtering, drying, and calcining to obtain mesoporous silica.

[0016] In the present invention, tetramethylammonium hydroxide is used as a template and tetramethyl silicate is used as a silicon source. Mesoporous silica with a connected pore structure is prepared by a sol-gel method. The active components in the vanadium catalyst can diffuse into the mesoporous silica through the connected pores, thereby increasing the active sites of the vanadium catalyst and further improving the catalytic activity of the vanadium catalyst.

[0017] Furthermore, the weight proportions of the components in the preparation method of mesoporous silica are: 5-8 parts of tetramethylammonium hydroxide, 30-40 parts of amyl alcohol, 8-10 parts of ammonia water, 15-20 parts of ether, and 25-30 parts of tetramethyl silicate.

[0018] Furthermore, in the preparation method of mesoporous silica, the stirring reaction time is 4.2-4.5 hours, the calcination temperature is 500-550° C., and the calcination time is 3.5-4 hours.

[0019] Furthermore, the preparation method of the mesoporous carbon in step S3 is: roasting the dried wheat bran under a nitrogen atmosphere, mixing it evenly with potassium hydroxide after cooling, continuing to roast it under a nitrogen atmosphere, grinding it after cooling, washing it with a hydrochloric acid aqueous solution until it is neutral, and drying it to obtain mesoporous carbon.

[0020] In the present invention, carbonized biomass material (wheat bran) is mixed with an activator, potassium hydroxide, and then calcined to prepare a porous carbon material with different pore structures and morphologies. The porous carbon material, together with modified diatomaceous earth and mesoporous silica, forms a carrier of the vanadium catalyst, effectively increasing the active sites of the vanadium catalyst and thereby improving the activation performance of the catalyst.

[0021] Furthermore, in the preparation method of mesoporous carbon, the calcination temperature is 750-800°C, and the calcination time is 0.8-1.2h; the continued calcination temperature is 800-850°C, and the continued calcination time is 4.2-4.5h; the mass ratio of wheat bran to potassium hydroxide is 1:2-3; and the concentration of the hydrochloric acid aqueous solution is 0.5-0.8mol / L.

[0022] Furthermore, the heating temperature in step S1 is 70-75°C; the ultrasonic frequency in step S3 is 200-250kHz, the ultrasonic time is 10-12h, the drying temperature is 90-100°C, the drying time is 20-24h, the roasting temperature is 550-600°C, the heating rate during roasting is 5-10°C / min, and the roasting time is 5.5-6h.

[0023] Furthermore, the weight proportions of the components are: 15-20 parts of potassium hydroxide, 35-40 parts of deionized water, 5-10 parts of vanadium pentoxide, 2-3 parts of sodium sulfate, 1-2 parts of Sm(NO3)3·6H2O, 25-30 parts of modified diatomaceous earth, and 10-15 parts of mesoporous material.

[0024] Compared with the prior art, the catalyst for sulfuric acid production provided by the present invention has the following technical advantages:

[0025] (1) The present invention uses samarium as a doping element to effectively improve the catalytic activity and low-temperature activity of the vanadium catalyst, so that it has good catalytic activity in a wide temperature range;

[0026] (2) The present invention uses modified diatomaceous earth and mesoporous materials to form a carrier, which effectively improves the dispersion of active components on the catalyst and is beneficial to improving the catalytic activity of the catalyst;

[0027] (3) In the present invention, diatomaceous earth is modified by using a dilute sulfuric acid solution under ultrasonic conditions to increase the specific surface area of ​​the diatomaceous earth, thereby improving the catalytic activity of the vanadium catalyst;

[0028] (4) The catalyst for sulfuric acid production provided by the present invention has the advantages of resistance to pulverization, high strength, low ignition temperature, and good activity stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a self-made activity evaluation device;

[0030] Figure 2 is a scanning electron microscope image of the catalyst prepared in Example 3;

[0031] Figure 3 is the XRD pattern of the catalyst prepared in Example 3;

[0032] Figure 4 This is the pore size distribution diagram of the catalyst prepared in Example 3;

[0033] Figure 5 This is the adsorption-desorption curve of the catalyst prepared in Example 3.

[0034] Figure 1 Among them, 1-1, 1-2, and 1-3 are buffer bottles, 2-1 and 2-2 are drying bottles, 3-1 and 3-2 are flow controllers (display instruments), 4 is a reactor, 5 is a collecting bottle, 6-1 and 6-2 are SO2 absorption tubes, 7-1 and 7-2 are gas cylinders (tubes), 8-1 is a level bottle, and 9 is an absorption bottle. DETAILED DESCRIPTION

[0035] The following will be further described in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Those skilled in the art can make various modifications based on the basic concept of the present invention, but as long as they do not deviate from the basic concept of the present invention, they are all within the scope of the present invention.

[0036] Example 1

[0037] A catalyst for sulfuric acid production is prepared by the following steps:

[0038] S1: Dissolve 15 g of potassium hydroxide in 40 g of deionized water, stir well, heat to 70°C, add 5 g of vanadium pentoxide and 2 g of sodium sulfate, stir well to obtain Solution I;

[0039] S2: Add concentrated sulfuric acid to the solution I obtained in step S1 under stirring to adjust the pH value of the solution to 2, and add 1 g of Sm(NO3)3·6H2O to obtain solution II;

[0040] S3: Add 25 g of modified diatomaceous earth and 10 g of mesoporous material to solution II obtained in step S2, stir evenly, and then ultrasonicate at 200 kHz for 10 h, shape, dry at 90°C for 20 h, and calcine at 550°C for 5.5 h (heating rate of 5°C / min) to obtain a catalyst for sulfuric acid production; the mesoporous material is composed of mesoporous silica and mesoporous carbon in a mass ratio of 9:4.

[0041] The modified diatomaceous earth prepared in step S3 is as follows: adding dried diatomaceous earth to a 3 mol / L dilute sulfuric acid solution (the mass ratio of diatomaceous earth to dilute sulfuric acid solution is 1:4), performing ultrasonic treatment under stirring (ultrasonic treatment at 500 kHz for 30 minutes), filtering, drying, and grinding to obtain modified diatomaceous earth.

[0042] The preparation method of mesoporous silica in step S3 is as follows: dissolve 5g of tetramethylammonium hydroxide in 30g of amyl alcohol, add 8g of ammonia water and 15g of ether, stir evenly, add 25g of tetramethyl silicate dropwise, stir and react for 4.2h, filter, dry, and calcine at 500°C for 3.5h to obtain mesoporous silica.

[0043] The preparation method of the mesoporous carbon described in step S3 is: the dried wheat bran is roasted at 750°C in a nitrogen atmosphere for 0.8h, and after cooling, it is evenly mixed with potassium hydroxide (the mass ratio of wheat bran to potassium hydroxide is 1:2), and then roasted at 800°C in a nitrogen atmosphere for 4.2h. After cooling, it is ground, washed with a 0.5mol / L hydrochloric acid aqueous solution until neutral, and dried to obtain mesoporous carbon.

[0044] Example 2

[0045] A catalyst for sulfuric acid production is prepared by the following steps:

[0046] S1: Dissolve 20 g of potassium hydroxide in 35 g of deionized water, stir well, heat to 75°C, add 10 g of vanadium pentoxide and 3 g of sodium sulfate, stir well to obtain Solution I;

[0047] S2: Add concentrated sulfuric acid to the solution I obtained in step S1 under stirring to adjust the pH value of the solution to 4, and add 2 g of Sm(NO3)3·6H2O to obtain solution II;

[0048] S3: Add 30 g of modified diatomaceous earth and 15 g of mesoporous material to solution II obtained in step S2, stir evenly, and then ultrasonicate at 250 kHz for 12 hours, shape, dry at 100°C for 24 hours, and calcine at 600°C for 6 hours (heating rate of 10°C / min) to obtain a catalyst for sulfuric acid production; the mesoporous material is composed of mesoporous silica and mesoporous carbon in a mass ratio of 12:7.

[0049] The modified diatomaceous earth prepared in step S3 is as follows: adding dried diatomaceous earth to a 4 mol / L dilute sulfuric acid solution (the mass ratio of diatomaceous earth to dilute sulfuric acid solution is 1:6), performing ultrasonic treatment under stirring (ultrasonic treatment at 550 kHz for 40 min), filtering, drying, and grinding to obtain modified diatomaceous earth.

[0050] The preparation method of mesoporous silica in step S3 is as follows: dissolve 8g of tetramethylammonium hydroxide in 40g of amyl alcohol, add 10g of ammonia water and 20g of ether, stir evenly, add 30g of tetramethyl silicate dropwise, stir and react for 4.5h, filter, dry, and calcine at 550°C for 4h to obtain mesoporous silica.

[0051] The preparation method of the mesoporous carbon described in step S3 is as follows: the dried wheat bran is calcined at 800°C in a nitrogen atmosphere for 1.2 hours, and after cooling, it is evenly mixed with potassium hydroxide (the mass ratio of wheat bran to potassium hydroxide is 1:3), and then further calcined at 850°C in a nitrogen atmosphere for 4.5 hours. After cooling, it is ground, washed with a 0.8 mol / L hydrochloric acid aqueous solution until neutral, and dried to obtain mesoporous carbon.

[0052] Example 3

[0053] A catalyst for sulfuric acid production is prepared by the following steps:

[0054] S1: Dissolve 18 g of potassium hydroxide in 37 g of deionized water, stir well, heat to 73°C, add 8 g of vanadium pentoxide and 2.3 g of sodium sulfate, and stir well to obtain Solution I;

[0055] S2: Add concentrated sulfuric acid to the solution I obtained in step S1 under stirring to adjust the pH value of the solution to 3, and add 1.5 g of Sm(NO3)3·6H2O to obtain solution II;

[0056] S3: Add 28 g of modified diatomaceous earth and 13 g of mesoporous material to solution II obtained in step S2, stir evenly, and then ultrasonicate at 230 kHz for 11 hours, shape, dry at 98°C for 22 hours, and calcine at 580°C for 5.7 hours (heating rate of 8°C / min) to obtain a catalyst for sulfuric acid production; the mesoporous material is composed of mesoporous silica and mesoporous carbon in a mass ratio of 11:6.

[0057] The modified diatomaceous earth prepared in step S3 is as follows: adding dried diatomaceous earth to a 3.5 mol / L dilute sulfuric acid solution (the mass ratio of diatomaceous earth to dilute sulfuric acid solution is 1:5), performing ultrasonic treatment under stirring (ultrasonic treatment at 530 kHz for 35 minutes), filtering, drying, and grinding to obtain modified diatomaceous earth.

[0058] The preparation method of mesoporous silica in step S3 is as follows: dissolve 7g of tetramethylammonium hydroxide in 35g of amyl alcohol, add 9g of ammonia water and 18g of ether, stir evenly, add 28g of tetramethyl silicate dropwise, stir and react for 4.4h, filter, dry, and calcine at 530°C for 3.8h to obtain mesoporous silica.

[0059] The preparation method of the mesoporous carbon described in step S3 is: the dried wheat bran is roasted at 780°C in a nitrogen atmosphere for 1.0h, and after cooling, it is evenly mixed with potassium hydroxide (the mass ratio of wheat bran to potassium hydroxide is 1:2.5), and further roasted at 830°C in a nitrogen atmosphere for 4.3h. After cooling, it is ground, washed with a 0.7mol / L hydrochloric acid aqueous solution until neutral, and dried to obtain mesoporous carbon.

[0060] Comparative Example 1

[0061] The preparation method of the catalyst for sulfuric acid production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of CsNO3 is used instead of Sm(NO3)3·6H2O in step S2 of this comparative example.

[0062] Comparative Example 2

[0063] The preparation method of the catalyst for sulfuric acid production described in this comparative example is similar to that of Example 3. The difference between this comparative example and Example 3 is that an equal amount of La(NO3)3 is used instead of Sm(NO3)3·6H2O in step S2 of this comparative example.

[0064] Comparative Example 3

[0065] The preparation method of the catalyst for sulfuric acid production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that in step S3 of this comparative example, an equal amount of modified diatomaceous earth is used instead of the mesoporous material.

[0066] Comparative Example 4

[0067] The preparation method of the catalyst for sulfuric acid production described in this comparative example is similar to that of Example 3. The difference between this comparative example and Example 3 is that the mesoporous materials described in step S3 of this comparative example are all mesoporous silica.

[0068] Comparative Example 5

[0069] The preparation method of the catalyst for sulfuric acid production described in this comparative example is similar to that of Example 3. The difference between this comparative example and Example 3 is that the mesoporous material described in step S3 of this comparative example is composed of mesoporous silica and mesoporous carbon in a mass ratio of 2:9.

[0070] Comparative Example 6

[0071] The preparation method of the catalyst for sulfuric acid production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that an equal amount of deionized water is used instead of dilute sulfuric acid solution during the preparation of the modified diatomaceous earth in this comparative example.

[0072] Comparative Example 7

[0073] The preparation method of the catalyst for sulfuric acid production in this comparative example is similar to that in Example 3. The difference between this comparative example and Example 3 is that potassium hydroxide is not added during the preparation of the mesoporous carbon in this comparative example.

[0074] Test example

[0075] Pore ​​structure test: The pore structure parameters of the catalysts prepared in Examples 1 to 3 and Comparative Examples 3 to 7 were analyzed using an AutoPore IV9500 mercury porosimeter and an ASAP2020 physical adsorption instrument from Micromeritics, USA. The test results are shown in Table 1. The pore size distribution and adsorption-desorption curve of the catalyst prepared in Example 3 are shown in Table 1. Figure 4 and Figure 5 .

[0076] Activity test: According to the method specified in the Chinese chemical industry standard "HG / T 2089-2014 Test method for activity of catalysts for sulfuric acid production by oxidation of sulfur dioxide", the catalysts prepared in Examples 1 to 3 and Comparative Examples 1 to 7 were tested in a self-made activity evaluation device (see Figure 1 The catalyst was placed in a quartz tube and heated from room temperature to 200°C at a rate of 200°C / h. Air was introduced and the temperature was further raised to 350°C. The feed gas containing 3% SO2 was switched to a space velocity of 7200 h / h. -1 , continue to heat up to 600℃ and keep warm for 2h. After activation is completed, reduce the temperature to be tested at a rate of 100℃ / h, and determine the SO2 concentration at the inlet and outlet by iodine titration. Repeat the measurement 3 times for each temperature point and record the average value. Load the catalyst solid into the reactor, make sure there is no air leakage, and turn on the switch to conduct the experiment. Start heating at a rate of 3℃ per minute. After 60 minutes, introduce dry air and control the air velocity to be about 3600h -1After another 45 minutes, high-purity sulfur dioxide was introduced, maintaining a sulfur dioxide volume fraction of approximately 10%. The temperature was then raised at a rate of 3°C per minute to 600°C for 5 hours. After reaching the heat-resistant temperature, the temperature was lowered at a rate of 200°C / h to the active temperatures of 485°C, 440°C, 410°C, and 350°C, respectively. Each temperature range was stabilized for 1 hour. The SO2 inlet and outlet concentrations were measured using iodine titration at each temperature range. Finally, the SO2 conversion rate (E) was calculated using the following formula: Vin is the SO2 inlet volume fraction, and Vout is the SO2 outlet volume fraction. The test results are shown in Table 2.

[0077]

[0078] Scanning electron microscopy (SEM) test: The catalyst prepared in Example 3 was tested by scanning electron microscopy. The test results are shown in Figure 2 .

[0079] X-ray diffraction test (XRD): The catalyst prepared in Example 3 was subjected to X-ray diffraction analysis test. The test results are shown in Figure 3 .

[0080] Table 1 Pore structure parameters of catalysts

[0081]

[0082] As shown in Table 1, the specific surface area of ​​the catalyst for sulfuric acid production provided by the present invention is 11.34-15.67m 2 / g, pore volume is 2.63-3.29cm 3 / g, and an average pore diameter of 35.96-43.21nm, indicating that the catalyst for sulfuric acid production provided by the present invention has a rich pore structure. Among them, the catalyst prepared in Example 3 has the best pore structure parameters and is the best embodiment of the present invention.

[0083] Compared with Example 3, in step S3 of Comparative Example 3, an equal amount of modified diatomaceous earth is used instead of the mesoporous material, but the pore structure parameters of the obtained catalyst are slightly reduced, which is because the pore structure of the modified diatomaceous earth is smaller than that of the mesoporous material; in step S3 of Comparative Example 4, the mesoporous materials described are all mesoporous silica, and the mass ratio of mesoporous silica and mesoporous carbon is changed in Comparative Example 5, but the pore structure parameters of the obtained catalyst are reduced to varying degrees, which shows that the components and ratios of the mesoporous materials in the present invention have been optimized; in the preparation process of modified diatomaceous earth in Comparative Example 6, an equal amount of deionized water is used instead of dilute sulfuric acid solution, and potassium hydroxide is not added in the preparation process of mesoporous carbon in Comparative Example 7, but the pore structure parameters of the obtained catalyst are significantly reduced, which shows that in the preparation process of modified diatomaceous earth and mesoporous carbon, dilute sulfuric acid solution and potassium hydroxide are key raw materials for pore expansion.

[0084] Table 2 Activity test results

[0085]

[0086] As can be seen from Table 2, the SO2 conversion rate of the catalyst for sulfuric acid production provided by the present invention is 93.5%-98.6% at 485°C, the SO2 conversion rate is 93.0%-98.5% at 440°C, the SO2 conversion rate is 91.9%-98.0% at 410°C, and the SO2 conversion rate is 89.3%-96.8% at 350°C. This fully demonstrates that the catalyst for sulfuric acid production provided by the present invention has good catalytic activity over a wide temperature range.

[0087] Compared with Example 3, an equal amount of CsNO3 is used instead of Sm(NO3)3·6H2O in step S2 of Comparative Example 1, and an equal amount of La(NO3)3 is used instead of Sm(NO3)3·6H2O in step S2 of Comparative Example 2, but the conversion rate of the obtained catalyst SO2 is significantly reduced, which shows that not all rare earth elements can achieve the technical effect of samarium element after doping; the conversion rate of the catalyst SO2 obtained in Comparative Examples 3 to Comparative Examples 7 is reduced, which is due to changes in the pore structure of the catalyst.

[0088] Depend on Figure 2 It can be seen that the catalyst prepared in Example 3 has obvious regularly arranged pores, which is a structural characteristic of diatomite. At the same time, there is also a disordered pore structure, which is partly a structural characteristic of mesoporous silica and mesoporous carbon. There are a small amount of finer oxide particles on the surface of mesoporous silica and mesoporous carbon. This shows that the active components in the catalyst provided by this application are distributed not only inside the pores, but also around the pores. During desulfurization, the contact frequency between the active components and sulfur dioxide can be increased, greatly improving the catalytic activity. In addition, no obvious rod-shaped or granular alkali metal salt crystals are found in the mesoporous material, indicating that the active components have a high degree of dispersion in the catalyst and a high catalytic activity.

[0089] Depend on Figure 3 It can be seen that the characteristic peaks of K3Na(SO4)2 appear at 2θ of 18.04°, 21.7°, 33.52° and 45.04°, the characteristic peaks of K3V(SO4)3 appear at 2θ of 27.24° and 35.24°, the diffraction peak of SmVO2SO4 appears at 2θ of 25.76°, the characteristic diffraction peak of amorphous silica appears at 2θ of 23°, and the diffraction peak of V2O5 appears at 2θ of 26.68°.

[0090] Depend on Figure 4 It can be seen that the main pore size distribution of the catalyst prepared in Example 3 is 35-65 nm, and the pore size distribution is relatively narrow. The pore volume is calculated to be 3.29 cm3 / g, the average pore size is 43.21nm. Figure 5 It can be seen that the catalyst prepared in Example 3 has a typical type IV isotherm and an H1-type hysteresis loop, which indicates that the catalyst sample of the present application has typical mesoporous structure characteristics, that is, the loading of the active component does not destroy or block the pores of the catalyst carrier. Therefore, the catalyst provided in the present application not only has a high adsorption capacity for the active component, but also in the desulfurization process, SO2 can smoothly pass through the pore structure to react with the active component, thereby improving the desulfurization efficiency.

[0091] The above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Persons skilled in the art should not modify the above embodiments without departing from the spirit and scope of the present invention. Any equivalent modifications or alterations made by persons skilled in the art without departing from the technical spirit of the present invention are intended to fall within the scope of protection of the present invention.

Claims

1. A catalyst for sulfuric acid production, characterized in that Prepared by the following steps: S1: Dissolve potassium hydroxide in deionized water, stir well, heat, add vanadium pentoxide and sodium sulfate, stir well, and obtain solution I; S2: Add concentrated sulfuric acid to the solution I obtained in step S1 under stirring, adjust the pH value of the solution to 2-4, and add Sm(NO3)3·6H2O to obtain solution II; S3: adding modified diatomaceous earth and mesoporous material to solution II obtained in step S2, stirring evenly, ultrasonicating, shaping, drying, and calcining to obtain a catalyst for sulfuric acid production; the mesoporous material is composed of mesoporous silica and mesoporous carbon in a mass ratio of 9-12:4-7; The preparation method of the modified diatomite in step S3 is: adding dry diatomite to a dilute sulfuric acid solution, performing ultrasonic treatment under stirring, filtering, drying, and grinding to obtain the modified diatomite; The preparation method of the mesoporous silica comprises: dissolving tetramethylammonium hydroxide in amyl alcohol, adding ammonia water and ether, stirring evenly, adding tetramethyl silicate dropwise, stirring to react, filtering, drying, and calcining to obtain the mesoporous silica; The preparation method of the mesoporous carbon comprises the following steps: roasting the dried wheat bran in a nitrogen atmosphere, mixing the dried wheat bran with potassium hydroxide after cooling, further roasting the wheat bran in a nitrogen atmosphere, grinding the wheat bran after cooling, washing the wheat bran with a hydrochloric acid aqueous solution until the wheat bran is neutral, and drying the wheat bran to obtain the mesoporous carbon.

2. The catalyst for sulfuric acid production according to claim 1, wherein In the preparation method of modified diatomaceous earth, the mass ratio of diatomaceous earth to dilute sulfuric acid solution is 1:4-6, the concentration of the dilute sulfuric acid solution is 3-4 mol / L; the frequency of the ultrasonic treatment is 500-550 kHz, and the ultrasonic treatment time is 30-40 min.

3. The catalyst for sulfuric acid production according to claim 1, wherein The weight proportions of the components in the preparation method of mesoporous silica are: 5-8 parts of tetramethylammonium hydroxide, 30-40 parts of amyl alcohol, 8-10 parts of ammonia water, 15-20 parts of ether, and 25-30 parts of tetramethyl silicate.

4. The catalyst for sulfuric acid production according to claim 1, wherein In the preparation method of mesoporous silica, the stirring reaction time is 4.2-4.5 hours, the calcination temperature is 500-550° C., and the calcination time is 3.5-4 hours.

5. The catalyst for sulfuric acid production according to claim 1, wherein In the preparation method of mesoporous carbon, the calcination temperature is 750-800°C, and the calcination time is 0.8-1.2h; the continued calcination temperature is 800-850°C, and the continued calcination time is 4.2-4.5h; the mass ratio of wheat bran to potassium hydroxide is 1:2-3; and the concentration of the hydrochloric acid aqueous solution is 0.5-0.8mol / L.

6. The catalyst for sulfuric acid production according to claim 1, wherein The heating temperature in step S1 is 70-75°C; the ultrasonic frequency in step S3 is 200-250kHz, the ultrasonic time is 10-12h, the drying temperature is 90-100°C, the drying time is 20-24h, the roasting temperature is 550-600°C, the heating rate during roasting is 5-10°C / min, and the roasting time is 5.5-6h.

7. The catalyst for sulfuric acid production according to claim 1, wherein The weight proportions of the components are: 15-20 parts of potassium hydroxide, 35-40 parts of deionized water, 5-10 parts of vanadium pentoxide, 2-3 parts of sodium sulfate, 1-2 parts of Sm(NO3)3·6H2O, 25-30 parts of modified diatomaceous earth, and 10-15 parts of mesoporous material.

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