A solid superacid catalyst, its preparation method and use

Abstract

The application discloses a solid superacid catalyst and a preparation method and application thereof, and relates to the technical field of catalysts, and specifically discloses the preparation method of the solid superacid catalyst, which comprises the following steps: dissolving a zirconium source, a titanium source, silica sol, urea and hexadecyl trimethyl ammonium bromide in water to prepare a precursor solution; heating the precursor solution to react, wherein the pH value of the system is increased from acidity to alkalinity during the reaction, and a reaction slurry is obtained; performing hydrothermal aging treatment on the reaction slurry, and then collecting the obtained precipitate; treating the precipitate with a rare earth salt solution to obtain a rare earth modified product; immersing the rare earth modified product in a sulfuric acid solution; and performing calcination on the immersed product to obtain the solid superacid catalyst. The solid superacid catalyst provided by the application has a regular sheet-like morphology and a composite structure of silica-rare earth synergistically anchoring sulfate, can guarantee high catalytic activity, realize strong anchoring of active components and rapid separation of the catalyst, and significantly improves the recycling stability.

Description

Technical Field

[0001] This invention relates to the field of catalytic materials technology, specifically to a solid superacid catalyst, its preparation method, and its application. Background Technology

[0002] Solid superacid catalysts represent a core technology in modern fine chemical and petrochemical industries, with applications extending to key industrial processes such as esterification, alkylation, and isomerization. By supporting sulfate ions on metal oxide supports to form superacid centers, catalysts can achieve highly efficient acid catalysis under mild conditions at the molecular scale, ensuring both high conversion rates and selectivity while also providing the possibility of catalyst recyclability and reuse. However, existing solid superacid catalysts generally face technical bottlenecks during industrial recycling, including loss of active components, difficulties in filtration, and poor cycle stability.

[0003] Currently, commercially available acid catalysis systems are mainly based on two technical pathways: liquid inorganic strong acids and solid superacids. Liquid strong acids, represented by concentrated sulfuric acid and hydrofluoric acid, rely on free hydrogen ions to provide catalytic activity, offering advantages such as low cost and high activity. However, this system has inherent drawbacks: First, liquid acids are extremely corrosive, requiring stringent material specifications for reaction equipment and incurring high maintenance costs; second, after the reaction, the acid and product are difficult to separate, necessitating multiple post-treatment processes such as alkali neutralization and water washing. For example, producing 1 ton of esterified product generates 0.2-0.5 tons of high-salt wastewater, resulting in heavy environmental treatment costs; third, liquid acids cannot be recycled, leading to resource waste. Solid superacids, such as SO4, are... 2- / ZrO2、SO4 2- Represented by TiO2, superacid catalysts rely on the synergistic effect of sulfate ions supported on the surface of a carrier and metal oxides to generate ultra-strong acidity. While they offer advantages such as reusability, easy separation, and non-corrosiveness to equipment, existing solid superacid catalysts generally suffer from the loss of sulfate active components during recycling. Traditional solid superacids are mostly amorphous nanoparticles or spherical aggregates (particle size 20~100nm), which easily clog filter pores during filtration and recovery, making separation difficult and resulting in significant catalyst loss. Furthermore, nanoparticles tend to aggregate and settle in the reaction system, further exacerbating activity decay and severely restricting the economic viability of their industrial recycling.

[0004] To address the aforementioned problems, researchers have made numerous improvements. For example, patent CN101745420A discloses a method for preparing and molding a mesoporous solid superacid catalyst. The specific steps include: adding silane-based tetraethyl orthosilicate to an ammonia solution containing the template agent hexadecyltrimethylammonium bromide (CTAB) and stirring; then adding ZrOCl2·8H2O solution dropwise while continuing stirring; followed by crystallization, sulfuric acid impregnation, drying, and calcination to obtain powdered mesoporous SO4. 2-The / ZrO2-MCM-41 solid superacid catalyst has several drawbacks. However, as a mesoporous powder, it presents challenges in separation during filtration and recovery. Furthermore, while it loads zirconium sulfate into the pores of the MCM-41 mesoporous material, relying on the spatial confinement of the active components within these pores to mitigate sulfate loss, the confinement effect is limited. During recycling, the sulfate active components are still prone to dissolution, and the catalytic stability requires further improvement. Similarly, patent CN112916024A discloses a solid superacid catalyst, its preparation method, and its application. Using aluminum isopropoxide as the aluminum source and UiO-66 as the zirconium source, a zirconium sulfate solid superacid catalyst is prepared. Although this catalyst has a high specific surface area, the interaction between zirconium oxide and sulfate is weak, leading to easy sulfate dissolution and poor recycling performance.

[0005] In summary, existing solid superacid catalysts generally have the following technical disadvantages: (1) The catalyst particles are mostly amorphous nanoparticles or spherical aggregates, which are difficult to filter and recover, and are easy to clog the filter pores, resulting in catalyst loss; (2) The bonding strength between sulfate and the support surface is limited, and it is easy to hydrolyze and fall off during the recycling process, especially in the aqueous reaction system, resulting in rapid decay of catalytic activity; (3) There is a lack of multiple anchoring mechanisms for sulfate, resulting in poor cycle stability. Summary of the Invention

[0006] To address the aforementioned technical problems, the present invention aims to provide a solid superacid catalyst, its preparation method, and its applications. The solid superacid catalyst provided by the present invention possesses a regular plate-like morphology and a composite structure in which silica and rare earth elements synergistically anchor sulfate ions. While ensuring high catalytic activity, it achieves strong anchoring of the active components and rapid separation of the catalyst, significantly improving its stability during recycling.

[0007] To achieve the above-mentioned technical objectives and effects, the present invention is implemented through the following technical solution: This invention provides a method for preparing a solid superacid catalyst, comprising the following steps: Step 1: Dissolve zirconium source, titanium source, silica sol, urea and hexadecyltrimethylammonium bromide in water to prepare a precursor solution; Step 2: The precursor solution is heated to react. During the reaction, the pH value of the system rises from acidic to alkaline, resulting in a reaction slurry. Step 3: Perform hydrothermal aging treatment on the reaction slurry, and then collect the resulting precipitate; Step 4: Treat the precipitate with a rare earth salt solution to obtain the rare earth modified product; Step 5: Impregnate the rare earth modified product with sulfuric acid solution; Step 6: Calcine the impregnated product to obtain the solid superacid catalyst.

[0008] Preferably, in step one, the zirconium source is zirconium oxychloride octahydrate, zirconium nitrate, or zirconium sulfate; the titanium source is titanium tetrachloride, titanium sulfate, or tetrabutyl titanate; and the silica sol is a nano-silica dispersion.

[0009] Furthermore, in the precursor solution, the concentration of the zirconium source is 0.06~0.15 mol / L, the concentration of the titanium source is 0.06~0.15 mol / L, the concentration of urea is 1.0~2.5 mol / L, the concentration of hexadecyltrimethylammonium bromide is 0.5~2.5 g / L, and the amount of silica sol added is such that the mass of silica, calculated as the final oxide, accounts for 8%~15% of the total mass of silica, zirconium oxide, and titanium oxide.

[0010] Furthermore, the heating reaction temperature in step two is 80~100℃; the hydrothermal aging treatment temperature in step three is 70~100℃.

[0011] Preferably, the rare earth salt in step four is a lanthanum salt or a cerium salt; the concentration of the rare earth salt solution is 0.005~0.2 mol / L.

[0012] Furthermore, the concentration of the sulfuric acid solution in step five is 0.5~2.0 mol / L; the calcination temperature in step six is ​​500~700℃.

[0013] Another aspect of the present invention provides a solid superacid catalyst having a sheet-like structure and comprising zirconium oxide, titanium oxide, silicon dioxide, rare earth oxides and sulfate.

[0014] Furthermore, based on oxides, silicon dioxide accounts for 8% to 15% of the total mass of zirconium oxide, titanium oxide, and silicon dioxide; the average diameter of the sheet-like structure is 1 to 5 μm, and the thickness is less than 300 nm.

[0015] Furthermore, the specific surface area of ​​the solid superacid catalyst is 100~150 m². 2 / g, and the conversion rate remains no less than 95% after 20 cycles of use.

[0016] The present invention further provides the application of this solid superacid catalyst in esterification, alkylation or isomerization reactions.

[0017] The beneficial effects of this invention are as follows: This invention utilizes a uniform precipitation method with the synergistic effect of hexadecyltrimethylammonium bromide to construct catalyst particles with a regular, plate-like structure. This plate-like structure is less prone to clogging filter pores during filtration and recovery, enabling rapid solid-liquid separation and fundamentally overcoming the shortcomings of traditional nanoparticles or spherical aggregates, which suffer from difficult filtration and significant catalyst loss.

[0018] Meanwhile, this invention utilizes silica introduced by silica sol to provide abundant surface hydroxyl anchoring sites, and combines this with the stable chelate structure formed by rare earth ions and sulfate ions to synergistically construct a "silica-rare earth" dual chemical anchoring system. This system strongly anchors sulfate ions to the catalyst surface, effectively suppressing the hydrolysis loss of sulfate ions during recycling, and solving the problem of rapid loss of active components caused by the single sulfate anchoring mechanism in traditional solid superacids.

[0019] Based on the synergistic effect of the above structural design and chemical anchoring mechanism, this invention significantly improves the stability and recycling convenience of the catalyst while maintaining high catalytic activity, achieving a balance between long lifespan and easy recycling of solid superacid catalysts in industrial applications. Attached Figure Description

[0020] Figure 1 This is a scanning electron microscope image of the solid superacid catalyst of Example 1 of the present invention.

[0021] Figure 2 This is a diagram showing the average flake size distribution of the solid superacid catalyst in Example 1 of the present invention.

[0022] Figure 3 This is an atomic force microscopy (AFM) three-dimensional morphology image of the solid superacid catalyst in Example 1 of the present invention.

[0023] Figure 4 for Figure 3 The thickness profile curve along the cross-sectional direction of the sheet is shown in the figure. The horizontal axis represents the horizontal distance (μm) along the scan line, and the vertical axis represents the thickness (nm) at the corresponding position.

[0024] Figure 5 This is a comparison chart of the catalytic activity of the catalyst in Example 1 of the present invention and the catalysts in Comparative Examples 1 and 2 when recycled in the esterification reaction, where the change in citric acid conversion rate with the number of recycling cycles is expressed. Detailed Implementation

[0025] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. 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.

[0026] This invention provides a method for preparing a solid superacid catalyst, comprising the following steps.

[0027] Step 1: Preparation of precursor solution Zirconium source, titanium source, silica sol, urea and hexadecyltrimethylammonium bromide were dissolved in water and stirred until completely dissolved to prepare a precursor solution.

[0028] The zirconium source can be selected from commonly used zirconium salts in the art, such as, but not limited to, zirconium oxychloride octahydrate, zirconium nitrate, and zirconium sulfate. The titanium source can be selected from titanium tetrachloride, titanium sulfate, and tetrabutyl titanate. The silica sol is preferably a nano-silica dispersion with a solid content of 20% to 40% and a silica particle size of 10 to 100 nm. Hexadecyltrimethylammonium bromide is used as a plate-like morphology directing agent.

[0029] Preferably, in the precursor solution, the concentration of the zirconium source is 0.06~0.15 mol / L, the concentration of the titanium source is 0.06~0.15 mol / L, the concentration of urea is 1.0~2.5 mol / L, and the concentration of hexadecyltrimethylammonium bromide is 0.5~2.5 g / L. The amount of silica sol added can be adjusted according to the silica content in the target product. For example, the mass of silica accounts for 8%~15% of the total mass of silica, zirconium oxide, and titanium oxide, based on the final oxide.

[0030] Step 2: Heating reaction The precursor solution is transferred to a reaction vessel and heated and stirred at a stirring speed of 150-300 rpm. During heating, urea gradually decomposes to produce hydroxide ions, causing the pH value of the system to gradually rise from the initial acidity (approximately 2-3) to alkalinity (approximately 8-9). The preferred heating temperature is 80-100°C, and the preferred reaction time is 24-48 hours. After the reaction is complete, a milky white reaction slurry is obtained.

[0031] Step 3: Hydrothermal aging and sediment collection The reaction slurry obtained in step two is transferred to a hydrothermal reactor (60%~80% filling) for hydrothermal aging. The preferred hydrothermal aging temperature is 70~100℃, and the preferred aging time is 12~24h. After aging, the precipitate is collected by vacuum filtration (using rapid qualitative filter paper, vacuum degree -0.085~-0.095MPa) or centrifugation (5000~8000rpm, 10~15min), and washed 3~6 times with deionized water (200~500mL each time) until the filtrate is neutral (pH=7) to remove unreacted ions and byproducts.

[0032] Step 4: Rare Earth Salt Solution Treatment The precipitate collected in step three is dispersed in a rare earth salt solution for treatment. The rare earth salt is preferably a lanthanum or cerium salt, such as lanthanum nitrate, cerium nitrate, lanthanum chloride, or cerium chloride. The concentration of the rare earth salt solution is preferably 0.005–0.2 mol / L. The treatment temperature is preferably 60–90 °C, and the treatment time is preferably 2–6 h. After treatment, solid-liquid separation is performed by vacuum filtration (using rapid qualitative filter paper, vacuum degree -0.085 to -0.095 MPa) or centrifugation (4000–6000 rpm, 10 min). The product is washed 1–3 times with deionized water and then dried at 80–120 °C for 6–24 h to obtain the rare earth modified product.

[0033] Step 5: Sulfuric acid impregnation The rare earth modified product obtained in step four is impregnated in a sulfuric acid solution. The concentration of the sulfuric acid solution is preferably 0.5~2.0 mol / L, and the impregnation time is preferably 2~6 h. After impregnation, solid-liquid separation is performed by vacuum filtration. The separated sulfuric acid solution can be recycled, and the solid product is directly subjected to the next step of calcination without washing.

[0034] Step Six: Roasting The sulfation product obtained in step five is placed in a muffle furnace or tube furnace for high-temperature calcination. The preferred calcination temperature is 500~700℃, the preferred heating rate is 1~5℃ / min, and the preferred calcination time is 3~6h. After calcination, the product is naturally cooled to room temperature to obtain the solid superacid catalyst.

[0035] The solid superacid catalyst prepared by the above method has a regular plate-like structure. For example, its average plate diameter is 1~5 μm and its thickness is less than 300 nm.

[0036] In terms of composition, the catalyst comprises zirconium oxide, titanium oxide, silicon dioxide, rare earth oxides, and sulfate. Specifically, based on the oxides, silicon dioxide accounts for 8% to 15% of the total mass of zirconium oxide, titanium oxide, and silicon dioxide. The rare earth oxides are preferably lanthanum oxide and / or cerium oxide, and their content can be adjusted according to the concentration of the rare earth salt solution and the processing conditions. For example, based on the oxides, the rare earth oxides account for 1% to 5% of the total mass of rare earth oxides, zirconium oxide, titanium oxide, and silicon dioxide.

[0037] In terms of performance, the solid superacid catalyst prepared by this invention has a high specific surface area, exemplarily 100~150m². 2 / g. It exhibits excellent catalytic activity and cycling stability in acid-catalyzed reactions. Typically, in the esterification reaction of citric acid and n-butanol, the initial catalytic conversion can reach over 94%, and the conversion rate is maintained at no less than 95% after 20 cycles.

[0038] The solid superacid catalyst provided by this invention can be widely used in various acid-catalyzed reactions, including but not limited to esterification, alkylation, and isomerization reactions. For example, it can be used for esterification of carboxylic acids and alcohols, alkylation of aromatics, and isomerization of alkanes. Due to its plate-like morphology and excellent resistance to sulfate dissolution, the catalyst is particularly suitable for industrial processes requiring catalyst recycling and frequent separation of products from the catalyst.

[0039] Example 1

[0040] Step 1: Dissolve 14.49 g of zirconium oxychloride octahydrate and 8.54 g of titanium tetrachloride in 400 mL of deionized water and stir until completely dissolved. Add 3.20 g of silica sol (30% solid content, 20-50 nm particle size) and stir for 30 min. Add 54.0 g of urea and 0.66 g of hexadecyltrimethylammonium bromide, and add deionized water to a final volume of 500 mL. Stir until completely dissolved to prepare the precursor solution.

[0041] Step 2: Transfer the precursor solution to a 1L three-necked flask equipped with a reflux condenser, and stir the mixture in a 95℃ oil bath for 36 hours at a stirring speed of 180-200 rpm. During the reaction, the solution gradually changes from clear to milky white, and the pH gradually increases from approximately 2.5 to 8.5-9.0.

[0042] Step 3: Transfer the reaction slurry to a PTFE-lined stainless steel reactor and age it in a sealed container at 85°C for 18 hours. Then, use rapid qualitative filter paper to filter and collect the precipitate under vacuum of -0.095 MPa. Wash the precipitate five times with deionized water until the pH of the filtrate is 7.

[0043] Step 4: Disperse the precipitate in 200 mL of aqueous solution containing 0.97 g of lanthanum nitrate hexahydrate and stir at 80 °C for 4 h. Then filter under vacuum of -0.095 MPa using rapid qualitative filter paper, wash twice with deionized water, and dry at 110 °C for 24 h.

[0044] Step 5: Immerse the dried product in 150 mL of 1.0 mol / L sulfuric acid solution for 4 hours. Separate the sulfuric acid solution by vacuum filtration (recover the filtrate), and do not wash the solid.

[0045] Step Six: The sulfation product was placed in a muffle furnace and heated to 600℃ at a rate of 2℃ / min, then calcined at this temperature for 4 hours. After natural cooling, a solid superacid catalyst with a plate-like structure was obtained, with an average plate diameter of 1~5μm and a thickness of <300nm. The resulting catalyst had a silica content (based on oxides, accounting for 9.5% of the total mass of zirconium oxide, titanium oxide, and silica) and a rare earth oxide (lanthanum oxide) content (based on oxides, accounting for 3.49% of the total mass of rare earth oxides, zirconium oxide, titanium oxide, and silica). Figure 1The image shown is a scanning electron microscope (SEM) image of the solid superacid catalyst obtained in Example 1. It can be seen that the catalyst exhibits a regular, plate-like morphology. The average plate diameter was calculated using Nano Measurer software based on SEM images (numbering at least 100 plates), and is 1.25 μm. Figure 2 This is the corresponding average sheet diameter distribution diagram. Figure 3 This is an atomic force microscopy (AFM) three-dimensional morphology image of the solid superacid catalyst in Example 1 of the present invention. The color scale indicates the height range of -324.6 nm to 412.1 nm, and the scale bar is 2.0 μm. Figure 4 for Figure 3 The thickness profile curve along the cross-sectional direction of the sheet is shown. The horizontal axis represents the horizontal distance (μm) along the scan line, and the vertical axis represents the thickness (nm) at the corresponding position. The average thickness is 123nm, which is obtained by thickness profile analysis and statistics from AFM images using NanoScope Analysis software.

[0046] Example 2

[0047] The difference between Example 2 and Example 1 lies in the adjustment of the feed amounts in step one: zirconium oxychloride octahydrate was 13.53 g, titanium tetrachloride was 7.97 g, silica sol was 4.80 g, urea was 50.4 g, and hexadecyltrimethylammonium bromide was 0.61 g; all other operations were the same as in Example 1. The resulting catalyst had a silica content of 14.4% and a rare earth oxide (lanthanum oxide) content of 3.53%.

[0048] Example 3

[0049] The difference between Example 3 and Example 1 lies in the amount of rare earth salt used in step four: the amount of lanthanum nitrate hexahydrate is changed to 0.48 g, while the rest of the operation is the same as in Example 1. The resulting catalyst has a silica content of 9.5% and a rare earth oxide (lanthanum oxide) content of 1.76%.

[0050] Example 4

[0051] The difference between Example 4 and Example 1 is that in step four, lanthanum nitrate hexahydrate is replaced with cerium nitrate hexahydrate, with a dosage of 0.96 g. The remaining operations are the same as in Example 1. The resulting catalyst has a silica content of 9.5% and a rare earth oxide (cerium oxide) content of 3.63%.

[0052] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the urea homogeneous precipitation method and CTAB morphology guiding agent were not used; instead, the ammonia precipitation method was used. The specific steps are as follows: 14.49 g of zirconium oxychloride octahydrate, 8.54 g of titanium tetrachloride, and 3.20 g of silica sol were dissolved in 400 mL of deionized water and stirred for 30 min; 25% concentrated ammonia was added dropwise at a rate of 2 mL / min at room temperature, and the mixture was stirred vigorously for about 30 min until the pH of the system reached 9.5; after precipitation, stirring was continued for 1 h, and the mixture was allowed to stand for 2 h (without hydrothermal aging); the mixture was filtered and washed 5 times with deionized water until the pH reached 7; then, steps four to six of Example 1 (i.e., rare earth lanthanum treatment, sulfuric acid impregnation, and calcination) were performed. The resulting catalyst had a silica content of 9.5% and a rare earth oxide (lanthanum oxide) content of 3.49%, but the catalyst was an amorphous nanoparticle and did not have a plate-like structure.

[0053] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that lanthanum nitrate solution is not added in step four (i.e., the rare earth treatment step is omitted), while the rest of the operation is the same as Comparative Example 1. The obtained catalyst has a silica content of 9.5%, a rare earth oxide content of 0, and does not have a plate-like structure, but is an amorphous nanoparticle.

[0054] The performance test results of the catalysts prepared in Examples 1-4 and Comparative Examples 1-2 are shown in Table 1.

[0055] Table 1

[0056] The specific surface area was determined in accordance with the national standard GB / T 19587-2017. The specific surface area of ​​solid materials was determined by gas adsorption method to compare the adsorption sites of catalysts with different structures.

[0057] The catalytic activity test (conversion rate) used the esterification reaction of citric acid and n-butanol as a model reaction. The specific procedure was as follows: 19.2 g of citric acid, 37.0 g of n-butanol, and 1.5 g of the catalyst to be tested were added to a 500 mL three-necked flask and refluxed at 120 °C for 4 h. After the reaction, the catalyst was separated by filtration. The filter cake was washed with 10 mL of anhydrous ethanol, dried at 110 °C for 2 h, and then directly used for the next batch of reaction. This procedure was repeated 20 times or more. The conversion rate represents the catalytic efficiency and was determined using gas chromatography with internal standard method. 1 mL of the reaction solution was sampled and extracted with n-dodecane internal standard and ethyl acetate. The chromatographic conditions were: HP-5 capillary column (30 m × 0.32 mm × 0.25 μm), injection port temperature 280 °C, detector temperature 300 °C, column temperature program: 100 °C for 2 min, then increased to 280 °C at 15 °C / min and held for 5 min. The citric acid conversion rate was calculated according to the internal standard curve. Gas chromatography analysis was performed in accordance with the national standard GB / T 9722-2006, and the conversion rate of citric acid was calculated in accordance with the international standard ISO 19741:2017.

[0058] Cyclic stability was evaluated by the conversion rate after 20 cycles and its retention rate relative to the initial conversion rate, where retention rate (%) = (conversion rate after 20 cycles / initial conversion rate) × 100%.

[0059] like Figure 5 As shown, the conversion rate curve of Example 1 remained stable throughout the 20 cycles, with an initial conversion rate of 96.8% and a retention rate of 93.8% after 20 cycles, reaching 96.9%. In contrast, the curves of Comparative Examples 1 and 2 showed a rapid decline with increasing cycle count, with conversion rates dropping to 45.6% and 38.2% respectively after 20 cycles, and retention rates of only 48.3% and 40.7%. This is because Example 1 possesses a regular lamellar morphology and a composite structure of silica-rare earth synergistic anchoring of sulfate, effectively suppressing the dissolution and loss of active components. Comparative Example 1, lacking a lamellar structure, had catalyst particles that were amorphous aggregates, making them prone to aggregation and sedimentation during cycling. This resulted in the shielding of active sites, difficulty in filtration and recovery, and a weaker sulfate anchoring effect compared to the synergistic system with a lamellar structure. Comparative Example 2 lacked both a lamellar structure and rare earth anchoring, relying solely on the surface bonding of silica and sulfate, resulting in the weakest anchoring effect. Therefore, in Comparative Examples 1 and 2, the sulfate ions rapidly detached during cycling, resulting in a rapid decline in catalytic activity. The above comparisons clearly demonstrate that the catalyst of this invention possesses excellent cycling stability.

[0060] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0061] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a solid superacid catalyst, characterized in that, Includes the following steps: Step 1: Dissolve zirconium source, titanium source, silica sol, urea and hexadecyltrimethylammonium bromide in water to prepare a precursor solution; Step 2: The precursor solution is heated to react. During the reaction, the pH value of the system rises from acidic to alkaline, resulting in a reaction slurry. Step 3: Perform hydrothermal aging treatment on the reaction slurry, and then collect the resulting precipitate; Step 4: Treat the precipitate with a rare earth salt solution to obtain the rare earth modified product; Step 5: Impregnate the rare earth modified product with sulfuric acid solution; Step 6: Calcine the impregnated product to obtain the solid superacid catalyst.

2. The method for preparing the solid superacid catalyst according to claim 1, characterized in that, In step one, the zirconium source is zirconium oxychloride octahydrate, zirconium nitrate, or zirconium sulfate; the titanium source is titanium tetrachloride, titanium sulfate, or tetrabutyl titanate; and the silica sol is a nano-silica dispersion.

3. The method for preparing the solid superacid catalyst according to claim 1, characterized in that, In the precursor solution, the concentration of zirconium source is 0.06~0.15 mol / L, the concentration of titanium source is 0.06~0.15 mol / L, the concentration of urea is 1.0~2.5 mol / L, the concentration of hexadecyltrimethylammonium bromide is 0.5~2.5 g / L, and the amount of silica sol added is such that the mass of silica, calculated as the final oxide, accounts for 8%~15% of the total mass of silica, zirconium oxide and titanium oxide.

4. The method for preparing the solid superacid catalyst according to claim 1, characterized in that, The heating reaction temperature in step two is 80~100℃; the hydrothermal aging treatment temperature in step three is 70~100℃.

5. The method for preparing the solid superacid catalyst according to claim 1, characterized in that, The rare earth salt mentioned in step four is a lanthanum salt or a cerium salt; the concentration of the rare earth salt solution is 0.005~0.2 mol / L.

6. The method for preparing the solid superacid catalyst according to claim 1, characterized in that, The concentration of the sulfuric acid solution in step five is 0.5~2.0 mol / L; the calcination temperature in step six is ​​500~700℃.

7. A solid superacid catalyst prepared by the preparation method according to any one of claims 1-6, characterized in that, The solid superacid catalyst has a plate-like structure and contains zirconium oxide, titanium oxide, silicon dioxide, rare earth oxides and sulfate.

8. The solid superacid catalyst according to claim 7, characterized in that, Based on oxides, silicon dioxide accounts for 8% to 15% of the total mass of zirconium oxide, titanium oxide, and silicon dioxide; the average diameter of the sheet-like structure is 1 to 5 μm, and the thickness is less than 300 nm.

9. The solid superacid catalyst according to claim 7, characterized in that, The specific surface area of ​​the solid superacid catalyst is 100~150 m². 2 / g, and the conversion rate remains no less than 95% after 20 cycles of use.

10. The use of the solid superacid catalyst according to claim 8 or 9 in esterification, alkylation or isomerization reactions.

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