A floating catalyst and its application in the synthesis of p-hydroxyphenylhydantoin.

Abstract

This invention discloses a floating catalyst and its application in the synthesis of p-hydroxyphenylhydantoin. Copper and manganese co-doped nano-TiO2 hydrosol is loaded onto fly ash cenospheres to form a gel. The dried gel is sintered at 600-700℃ to obtain a floating catalyst with fly ash cenospheres as the support. Its chemical composition is: SO42- 2‑ / TiO2-CuO-Mn2O3 / fly ash cenospheres; its mass composition is: TiO2-CuO-Mn2O3 / 2 25%‑30%, CuO3%‑10%, Mn2O 3 6%–20%, S 0.02%–0.1%, fly ash cenospheres 50%–60%; its specific gravity is 0.6–0.90 g / cm³. 3 Specific surface area is 10-50 m² 2 / g; possesses solid superacid properties with an acid strength H0 ≤ -14.5; dissolves in acidic solvents to generate trace amounts of copper and manganese ions. The catalyst of this invention can float on the surface of aqueous solutions, solving the problem of separating solid catalysts from insoluble p-hydroxybenzylhydantoin products; it catalyzes the synthesis of p-hydroxybenzylhydantoin via two pathways, achieving a product molar yield of 68%-72%; it possesses photocatalytic functionality, allowing for the regeneration of catalysts that have lost surface catalytic activity; and it reduces the generation of organic pollutants at the source.

Description

Technical Field

[0001] This invention relates to a floating catalyst and its application in the synthesis of p-hydroxyphenylhydantoin, belonging to the fields of new materials and chemical pharmaceutical technology. Background Technology

[0002] p-Hydroxyphenylhydantoin is an important pharmaceutical and chemical intermediate. After biohydrolysis, it efficiently produces L-p-hydroxyphenylglycine, which is mainly used as a side chain compound for the antibiotics amoxicillin and amoxicillin cephalosporins, with a market demand of tens of thousands of tons.

[0003] European patent EP0001319 and US patent US4230869 disclose in detail the synthesis method of p-hydroxyphenylhydantoin. Based on glyoxylic acid as the main raw material, the molar yield of p-hydroxyphenylhydantoin can reach 65.5%. However, in industrial production, even with a significant excess of auxiliary raw materials, the actual molar yield of p-hydroxyphenylhydantoin is only around 55%, and the production process is extremely polluting, with waste residue and wastewater difficult to treat to compliance standards. The reported technical improvements have not been adopted by manufacturers due to a lack of techno-economic viability.

[0004] Patent CN110330460B discloses a method for preparing p-hydroxyphenylhydantoin, which involves condensation into a ring under the catalysis of a solid acid to obtain p-hydroxyphenylhydantoin. The solid acid is at least one of acidic ion exchange resin, heteropoly acid, metal salt, a metal salt complex supported on a carrier, or a metal oxide. However, the patent does not mention that the p-hydroxyphenylhydantoin product has very low solubility in common solvents, leading to difficulties in separating the product from the solid acid catalyst powder.

[0005] Patent CN104174436B discloses a barium sulfonate catalyst and its application in the synthesis of D,L-p-hydroxyphenylhydantoin. It uses a solvent-free method to synthesize p-hydroxyphenylhydantoin products, and then adds water to dissolve the reactants. However, it also has the problem of difficult product separation and purification. Furthermore, the high-energy-consuming ultrasonic technology used is not suitable for industrial production applications.

[0006] Patent CN112457256B discloses a method for preparing D,L-p-hydroxyphenylhydantoin. The method involves adding phenol, 98% sulfuric acid, and water to a reaction vessel. A sulfuric acid aqueous solution of a certain concentration is used to first catalyze the para-activation of phenol, followed by the addition of a catalyst. The reaction is carried out in stages with heating and feeding to effectively suppress impurity generation and improve product yield and quality. However, due to the severe foaming and impurity adsorption of the surfactant catalyst used, industrial application is difficult.

[0007] Experiments revealed that the yield of p-hydroxyphenylhydantoin synthesis is controlled by a combination of the condensation reaction of glyoxylic acid and phenol and the amidation cyclization reaction of glyoxylic acid and urea. Both condensation and amidation reactions of glyoxylic acid and urea require catalysts to accelerate the yield of p-hydroxyphenylhydantoin. However, the acid catalysts used in existing technologies are ineffective, making it difficult to improve the molar yield of p-hydroxyphenylhydantoin synthesis and resulting in the generation of large amounts of highly acidic and difficult-to-treat production wastewater. Summary of the Invention

[0008] The first objective of this invention is to provide a floating catalyst to solve the technical problems of unsatisfactory yield in the synthesis of p-hydroxyphenylhydantoin, difficulty in separating the solid acid catalyst from the product, and environmental pollution from the mother liquor; the second objective is to provide a method for preparing the above-mentioned floating catalyst; and the third objective is to provide a method for applying the above-mentioned floating catalyst in the synthesis of p-hydroxyphenylhydantoin.

[0009] To achieve the primary objective, the present invention is implemented through the following technical solution:

[0010] A floating catalyst with the chemical composition of SO4. 2- / TiO2-CuO-Mn2O3 / fly ash cenospheres; these are obtained by loading copper and manganese co-doped nano-TiO2 hydrosol onto fly ash cenospheres to form a gel, followed by sintering the dried gel at 600-700℃; the floating catalyst particles have a particle size of 30-100 mesh and a specific gravity of 0.6-0.90 g / cm³. 3 Specific surface area is 10-50 m² 2 / g; its mass composition is: TiO2 25%-30%, CuO 3%-10%, Mn2O3 6%-20%, S 0.02%-0.1%, fly ash cenospheres 50%-60%; it has the function of solid super acid, with acid strength H0≤-14.5; it can dissolve in acidic solvents to generate copper and manganese ions in a catalyst amount; it has photocatalytic function, and can regenerate catalysts that have lost surface catalytic activity by photocatalysis; it can float on the surface of aqueous solution, solving the problem of separating solid catalysts from insoluble p-hydroxyphenylhydantoin products.

[0011] The synthesis of p-hydroxybenzylhydantoin is essentially a tripolecular reaction of glyoxylic acid with phenol and urea. The reaction mechanism is not fully understood, but it is generally believed that under the catalysis of an inorganic acid, glyoxylic acid and urea react rapidly to generate an intermediate product, which then condenses and attaches to the para-position of the phenol molecule. The intermediate product then undergoes amidation and cyclization to form the p-hydroxybenzylhydantoin product. Solid superacids can replace inorganic acids to accelerate the condensation reaction of glyoxylic acid and phenol, and can also catalyze the reaction of glyoxylic acid and urea.

[0012] The floating catalyst in this invention is a multifunctional catalyst, not only possessing the function of a solid superacid catalyzing the reaction of glyoxylic acid and phenol, but also capable of producing a catalytic amount of Cu. 2+ and Mn 2++ Ions catalyze the reaction of glyoxylic acid with urea.

[0013] Fly ash cenospheres are hollow silica-alumina oxides separated from power plant coal ash. Due to their low specific gravity, the TiO2-CuO-Mn2O3 they support can float in aqueous solution. Fly ash cenospheres are rich in transition metals, and the trace transition metal ions produced when dissolved in acidic reaction solutions also act as co-catalysts.

[0014] SO4 in this invention 2- / TiO2-CuO-Mn2O3 possesses the function of a solid superacid, mainly because sulfated nano-TiO2 and its composite materials are solid superacids with an acid strength H0≤-14.5, which is hundreds of times stronger than 100% concentrated sulfuric acid. This is generally believed to be caused by the adsorption and complexation of sulfuric acid on the surface of TiO2.

[0015] Experimental studies have found that trace amounts of Cu 2+ and Mn 2+ The ions catalyze the formation of a hydantoin ring from glyoxylic acid and urea. In the acidic system of this invention, trace amounts of Cu coated with nano-TiO2 can be controlled to dissolve. 2+ and Mn 2+ As an ion, it has the function of catalyzing the amidation of glyoxylic acid and urea to form a hydantoin ring. The catalytic effect can occur both in the solution phase and on the surface of the solid catalyst.

[0016] The floating catalyst of this invention also exhibits excellent photocatalytic performance. When deactivated floating catalysts are irradiated with visible light, the organic pollutants covering their surface are photocatalytically degraded, thereby restoring their catalytic activity. During repeated use, the sulfate active component bound to the surface of the floating catalyst may be lost, leading to a decline in catalyst performance. This can be remedied by immersing it in a dilute sulfuric acid solution and then undergoing a sulfation-calcination treatment to restore the activity of the floating catalyst and extend its cycle life.

[0017] In summary, the floating catalyst of the present invention has the following six outstanding substantive features and significant technological advancements: (1) It has the function of a solid superacid and can catalyze the reaction of glyoxylic acid and phenol; (2) The amount of Cu dissolved in copper and manganese oxides to generate catalyst can be controlled in the acidic reaction solution. 2+ and Mn 2+(3) It has a floating function in aqueous solution, which can simplify the separation of catalyst particles from products; (4) TiO2-CuO-Mn2O3 loaded on fly ash carrier has a large specific surface area and can heterogeneously catalyze the synthesis reaction of p-hydroxyphenylhydantoin; (5) It has good visible light catalytic ability. Visible light irradiation can decompose organic pollutants on the catalyst surface and restore its catalytic activity; (6) It can be re-impregnated with dilute sulfuric acid and sintered to restore its catalytic activity. The floating catalyst has a long service life.

[0018] To achieve the second objective, the present invention is implemented through the following technical solution:

[0019] A method for preparing a floating catalyst includes four parts, specifically the following steps:

[0020] S1: Dissolution of catalyst components:

[0021] Measure anhydrous ethanol, add concentrated sulfuric acid hydrolysis inhibitor dropwise, and add tetrabutyl titanate under vigorous stirring to form anhydrous ethanol solution of tetrabutyl titanate; measure 70% ethanol aqueous solution separately, add copper nitrate and manganese nitrate solids respectively, and adjust the pH of the ethanol aqueous solution to 1-3 with dilute nitric acid to form ethanol aqueous solution of copper nitrate and manganese nitrate.

[0022] S2: Preparation of copper and manganese co-doped nano-TiO2 ethanol hydrosol:

[0023] An aqueous solution of copper nitrate and manganese nitrate in ethanol was added dropwise to an anhydrous ethanol solution of tetrabutyl titanate under stirring. The molar ratio of Ti, Cu, and Mn raw materials in the reactants was controlled to be 1:0.1-0.3:0.1-0.3. The tetrabutyl titanate was slowly hydrolyzed into nano-TiO2. After aging at room temperature for 8-24 hours, an ethanol hydrosol of nano-TiO2 co-doped with copper and manganese was formed.

[0024] S3: Preparation of copper and manganese co-doped nano-TiO2 gel:

[0025] Fly ash cenospheres were impregnated in copper and manganese co-doped nano-TiO2 ethanol hydrosol. As the solvent ethanol evaporated, a wet gel of copper and manganese co-doped nano-TiO2 loaded with fly ash cenospheres was formed. The wet gel was dried at 80-90℃ to obtain a dry gel of copper and manganese co-doped nano-TiO2.

[0026] S4: Sintering of floating catalyst dry gel:

[0027] The dried gel was transferred to an alumina crucible and calcined at 600-700℃ for 1-3 hours. After cooling, the product with the chemical composition SO4 was obtained. 2-A floating catalyst consisting of / TiO2-CuO-Mn2O3 / fly ash cenospheres; its particle size is 30-100 mesh, acid strength H0≤-14.5, and specific gravity is 0.6-0.90 g / cm³. 3 Specific surface area is 10-50 m² 2 / g, with a mass composition of: TiO2 25%-30%, CuO 3%-10%, Mn2O3 6%-20%, S 0.02%-0.1%, and fly ash cenospheres 50%-60%.

[0028] The preparation method of the floating catalyst of the present invention, in addition to the inventiveness of the floating catalyst product itself, also has the following four outstanding substantive features and significant technological progress in the preparation method: (1) Titanium tetrabutyl ester is selected as the titanium source, and nano-TiO2 is used as the binder of the floating catalyst; (2) Copper nitrate and manganese nitrate, which are easily soluble in ethanol and water, are selected as the copper source and manganese source, which facilitates the co-doping of nano-TiO2 by copper and manganese elements; (3) Inexpensive and readily available fly ash cenospheres are selected as the catalyst carrier, realizing the floating function of the catalyst; (4) The floating catalyst SO4 2- The formation, sintering, and sulfation of / TiO2-CuO-Mn2O3 / fly ash cenospheres are completed simultaneously, simplifying the preparation process of floating catalysts.

[0029] To achieve the third objective, the present invention is implemented through the following technical solution:

[0030] A method for the application of a floating catalyst in the synthesis of p-hydroxyphenylhydantoin includes four parts, the specific steps of which are as follows:

[0031] T1: Synthesis of p-hydroxyphenylhydantoin:

[0032] Add organic solvent, phenol, urea, and floating catalyst particles to the reactor; then add dilute sulfuric acid to make the sulfuric acid concentration in the reaction solution 0.5-1 mol / L; control the molar ratio of glyoxylic acid, phenol, and urea to 1:1-1.2:1-1.5 during feeding; the mass of the floating catalyst particles added is 5%-20% of the total mass of the reaction solution; heat the reaction solution to 60-120℃ and reflux, then slowly add a 50% glyoxylic acid aqueous solution, completing the addition in 6-9 hours, and azeotropically distill off the water introduced by the glyoxylic acid and generated in the reaction; add p-hydroxybenzenehydantoin seed crystals, and continue to keep the reaction at the temperature for 2-3 hours to ensure the reaction is complete; the organic solvent is one of methanol, ethanol, dimethylformamide, tetrahydrofuran, or petroleum ether.

[0033] T2: Solvent recovery and separation of reaction products:

[0034] The organic solvent in the reactants is recovered by vacuum distillation and recycled; 3-6 times the amount of deionized water is added to the residual solids and stirred at 30-40℃ to disperse the solids; the floating catalyst particles float on the top of the aqueous solution, the p-hydroxyphenylhydantoin product powder precipitates at the bottom of the aqueous solution, and the by-products dissolve in the aqueous solution;

[0035] T3: Recovery and activation of floating catalysts:

[0036] Filter the floating catalyst particles through a 100-mesh screen, wash off the entrained product powder with water, and the catalyst can be recycled 5 times. After 5 recyclings, the catalyst activity is greatly reduced. Irradiate it under visible light for 8-12 hours to restore the catalytic activity, and then recycle it 5 more times. After 10 recyclings, immerse it in a 0.5-1.0 mol / L sulfuric acid aqueous solution for 8-12 hours, filter, dry, and calcine at 600-700℃ for 1-3 hours to restore the catalytic activity, and then recycle it.

[0037] T4: Product Separation and Inspection

[0038] The p-hydroxyphenylhydantoin product powder was separated from the aqueous solution, washed with hot water at 40-50℃ until the surface was no longer sticky, and then dried; the liquid chromatography purity of the product was 98.5%-99.5%; the molar yield of the product was 68%-72%.

[0039] The application method of the floating catalyst in the synthesis of p-hydroxyphenylhydantoin of the present invention, in addition to the creativity of the floating catalyst product and preparation method, also has the following four outstanding substantive features and significant technological progress in the application method: (1) The molar yield of p-hydroxyphenylhydantoin product is significantly improved, reducing the generation of pollutants from the source; (2) Organic solvent is used for the synthesis of p-hydroxyphenylhydantoin, and the solvent is recycled; (3) High-concentration hydrochloric acid is no longer used as the reaction catalyst, the corrosion of the production equipment is relatively low, and the aqueous solution can also be recycled, which is a green production process; (4) Some seed crystals are added to the reaction system to induce crystallization, which can prevent the generation of large crystal particles that are difficult to separate from the catalyst particles; (5) The difference between the floating catalyst particles being easy to float, the by-products being easy to dissolve in aqueous solution and the p-hydroxyphenylhydantoin powder being easy to precipitate in aqueous solution is fully utilized to facilitate the separation and recovery of the floating catalyst; (6) Co-doping of copper and manganese elements endows nano-TiO2 with visible light photocatalytic performance, and the photocatalytic efficiency is multiplied after sulfation treatment, and the floating catalyst can be regenerated by visible light irradiation.

[0040] The raw materials used in this invention, such as glyoxylic acid, phenol, urea, sulfuric acid, hydrochloric acid, ammonia, tetrabutyl titanate, manganese nitrate, copper nitrate, and ethanol, are all chemical reagents.

[0041] The raw material, fly ash cenospheres, is an industrial product available for online purchase. Its chemical composition (by mass) is: SiO2 50%-65%, Al2O3 25%-35%, Fe2O3 4%-9%, alkali metal and alkaline earth metal oxides 2.5%-15%, particle size 20-200 mesh, and specific surface area 0.3-1 m². 2 / g, specific gravity is 0.25-0.45g / cm³ 3 .

[0042] The beneficial effects of this invention are:

[0043] (1) The floating catalyst of the present invention has the function of solid super acid and controls the dissolution of CuO-Mn2O3. It can not only catalyze the reaction of glyoxylic acid with phenol, but also catalyze the reaction of glyoxylic acid with urea, thereby increasing the synthesis yield of p-hydroxyphenylhydantoin and reducing the generation of organic pollutants from the source.

[0044] (2) The floating catalyst of the present invention can float on the aqueous solution, which solves the problem of separating the solid catalyst from the insoluble p-hydroxyphenylhydantoin product;

[0045] (3) The floating catalyst of the present invention has good visible light catalytic ability. Its catalytic activity can be restored by visible light irradiation or re-impregnation with dilute sulfuric acid followed by sintering treatment. The floating catalyst has a long service life. Detailed Implementation

[0046] Example 1

[0047] Measure 100 mL of anhydrous ethanol and add 0.5 mL of concentrated sulfuric acid hydrolysis inhibitor. Under vigorous stirring, add 34.0 g (0.1 mol) of tetrabutyl titanate solution to form an anhydrous ethanol solution of tetrabutyl titanate. Measure 50 mL of 70% ethanol aqueous solution and add 5.7 g (0.03 mol) of copper nitrate and 5.4 g (0.03 mol) of manganese nitrate, respectively. Adjust the pH of the ethanol aqueous solution to 1-3 with dilute nitric acid to form ethanol aqueous solutions of copper nitrate and manganese nitrate. Under stirring, add the ethanol aqueous solutions of copper nitrate and manganese nitrate to the anhydrous ethanol solution of tetrabutyl titanate. Tetrabutyl titanate slowly hydrolyzes into nano-TiO2. Aging at room temperature for 12 h forms a copper and manganese co-doped nano-TiO2 ethanol hydrosol.

[0048] 14.9 g of 100-mesh fly ash agar beads were impregnated in a copper- and manganese-doped nano-TiO2 ethanol hydrosol. As the ethanol solvent evaporated, a wet gel of copper- and manganese-doped nano-TiO2 supported on the fly ash agar beads was formed. This wet gel was dried at 80-90℃ to obtain a dry gel of copper- and manganese-doped nano-TiO2. The dry gel was transferred to an alumina crucible and calcined at 600-700℃ for 3 hours. After cooling, 30 g of a floating catalyst with a particle size of 50 mesh and a specific gravity of 0.70 g / cm³ was obtained. 3 Specific surface area 30m² 2 / g; its mass composition is: TiO2 26.7%, CuO 8%, Mn2 15.7%, S 0.1%, fly ash cenospheres 50%.

[0049] Example 2

[0050] Measure 200 mL of anhydrous ethanol and add 0.3 mL of concentrated sulfuric acid hydrolysis inhibitor. Add 102 g (0.3 mol) of tetrabutyl titanate solution under vigorous stirring to form an anhydrous ethanol solution of tetrabutyl titanate. Measure 50 mL of 70% ethanol aqueous solution and add 5.7 g (0.03 mol) of copper nitrate and 5.4 g (0.03 mol) of manganese nitrate, respectively. Adjust the pH of the ethanol aqueous solution to 1-3 with dilute nitric acid to form ethanol aqueous solutions of copper nitrate and manganese nitrate. Add the ethanol aqueous solutions of copper nitrate and manganese nitrate to the anhydrous ethanol transparent solution of tetrabutyl titanate under stirring. Tetrabutyl titanate slowly hydrolyzes into nano-TiO2. Aging at room temperature for 12 h forms a copper and manganese co-doped nano-TiO2 ethanol hydrosol.

[0051] 48g of 40-mesh fly ash cenospheres were impregnated with copper and manganese co-doped nano-TiO2 ethanol hydrosol. As the ethanol solvent evaporated, a wet gel of copper and manganese co-doped nano-TiO2 supported on the fly ash cenospheres was formed. This wet gel was dried at 80-90℃ to obtain a dry gel of copper and manganese co-doped nano-TiO2. The dry gel was transferred to an alumina crucible and calcined at 600-700℃ for 3 hours. After cooling, 80g of a floating catalyst with a particle size of 30 mesh and a specific gravity of 0.90 g / cm³ was obtained. 3 Specific surface area 50m² 2 / g; its mass composition is: TiO2 30%, CuO 3%, Mn2O3 5.9%, S 0.05%, fly ash cenospheres 60%.

[0052] Example 3

[0053] In a reactor, 1000 mL of anhydrous ethanol solvent, 111.6 g (1.2 mol) of phenol, 91 g (1.5 mol) of urea, 49 g (0.5 mol) of sulfuric acid, and 100 g of the floating catalyst prepared in Example 1 were added. The reaction solution was heated to 70 °C and refluxed. 148 g (1.0 mol) of a 50% glyoxylic acid aqueous solution was slowly added, and one-third of the aqueous ethanol was distilled off. Anhydrous ethanol solvent was then added, and the addition was completed in about 8 hours. Then, 1.5 g of p-hydroxyphenylhydantoin seed crystals were added, and a white crystalline precipitate of p-hydroxyphenylhydantoin was formed. The reaction was continued at this temperature for another 2 hours to ensure complete reaction. After the reaction was completed, the anhydrous ethanol solvent was recovered by vacuum distillation and recycled. 1000 mL of deionized water was added to the residual solid, and the mixture was stirred at room temperature until the solid was dispersed. The floating catalyst particles were separated by filtration, and the entrained product powder was washed with water. The p-hydroxyphenylhydantoin powder was separated from the aqueous solution, washed with hot water, and the product was dried. The liquid chromatography purity was 99.2% and the molar yield was 72%.

[0054] Example 4

[0055] In a reactor, 1000 mL of methanol solvent, 102.4 g (1.1 mol) of phenol, 91 g (1.5 mol) of urea, 25 g (0.25 mol) of sulfuric acid, and 50 g of the floating catalyst prepared in Example 2 were added. The reaction solution was heated to 65°C and refluxed. 148 g (1.0 mol) of 50% glyoxylic acid aqueous solution was added, and half of the aqueous methanol was distilled off. Anhydrous methanol solvent was added, and the reaction was completed in about 8 hours, forming a brownish-yellow organic solution. 1.5 g of p-hydroxyphenylhydantoin seed crystals were added, and a white crystalline precipitate of p-hydroxyphenylhydantoin was formed. The reaction was continued at this temperature for another 2 hours to ensure complete reaction. After the reaction was completed, the methanol solvent was recovered by vacuum distillation and recycled. 1000 mL of deionized water was added to the residual solid, and the mixture was stirred at room temperature until the solid was dispersed. The floating catalyst particles floated on the surface of the aqueous solution, and the product powder precipitated at the bottom. The floating catalyst particles were separated by filtration, and the entrained product powder was washed with water. The p-hydroxyphenylhydantoin powder was separated from the aqueous solution, washed with hot water until the surface was no longer sticky, dried, and the liquid chromatography purity of the product was 99.5%; the molar yield of the product was 68%.

[0056] Comparative Example 1

[0057] In a reactor, 600 mL of deionized water, 111.6 g (1.2 mol) of phenol, 91 g (1.5 mol) of urea, and 470 g (4 mol) of 31% hydrochloric acid were added. The reaction solution was heated to 80-90 °C and stirred. 148 g (1.0 mol) of 50% glyoxylic acid aqueous solution was slowly added over approximately 8 hours. Then, 0.5 g of p-hydroxyphenylhydantoin seed crystals were added, resulting in the formation of a white crystalline precipitate of p-hydroxyphenylhydantoin. The reaction was continued at this temperature for another 4 hours to ensure complete reaction. The p-hydroxyphenylhydantoin powder in the aqueous solution was separated, washed with hot water, and the product, after drying, had a liquid chromatography purity of 98.9% and a molar yield of 58%.

[0058] By comparing Examples 3, 4 and Comparative Example 1, it can be seen that the floating catalyst of the present invention achieves a synthesis yield of 68%-72% for p-hydroxyphenylhydantoin, which is significantly higher than the synthesis yield of p-hydroxyphenylhydantoin in Comparative Example 1 when hydrochloric acid is used as a catalyst.

[0059] The foregoing has shown and described the basic principles and main features of the present invention and its advantages. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and all variations falling within the meaning and scope of the equivalents of the claims are included within the present invention.

Claims

1. A floating catalyst, characterized in that: Its chemical composition is: SO4 2- / TiO2-CuO-Mn2O3 / fly ash cenospheres; these are produced by loading copper and manganese co-doped nano-TiO2 hydrosol onto fly ash cenospheres to form a gel, followed by sintering the dried gel at 600-700℃; the floating catalyst particles have a particle size of 30-100 mesh and a specific gravity of 0.6-0.90 g / cm³. 3 Specific surface area is 10-50 m² 2 / g; its mass composition is: TiO2 25%-30%, CuO 3%-10%, Mn2O3 6%-20%, S 0.02%-0.1%, fly ash cenospheres 50%-60%; it has the function of solid super acid, with acid strength H0≤-14.5; it can dissolve in acidic solvents to generate copper and manganese ions in a catalyst amount; it has photocatalytic function, and can regenerate catalysts that have lost surface catalytic activity by visible light photocatalysis; it can float on the surface of aqueous solution, solving the problem of separating solid catalysts from insoluble p-hydroxybenzylhydantoin products.

2. A method for preparing the floating catalyst as described in claim 1, characterized in that: It includes four parts, specifically the following steps: S1: Dissolution of catalyst components: Measure anhydrous ethanol, add concentrated sulfuric acid hydrolysis inhibitor dropwise, and add tetrabutyl titanate under vigorous stirring to form anhydrous ethanol solution of tetrabutyl titanate; measure 70% ethanol aqueous solution separately, add copper nitrate and manganese nitrate solids respectively, and adjust the pH of the ethanol aqueous solution to 1-3 with dilute nitric acid to form ethanol aqueous solution of copper nitrate and manganese nitrate. S2: Preparation of copper and manganese co-doped nano-TiO2 ethanol hydrosol: An aqueous solution of copper nitrate and manganese nitrate in ethanol was added dropwise to an anhydrous ethanol solution of tetrabutyl titanate under stirring. The molar ratio of Ti, Cu, and Mn raw materials in the reactants was controlled to be 1:0.1-0.3:0.1-0.

3. The tetrabutyl titanate was slowly hydrolyzed into nano-TiO2. After aging at room temperature for 8-24 hours, an ethanol hydrosol of nano-TiO2 co-doped with copper and manganese was formed. S3: Preparation of copper and manganese co-doped nano-TiO2 gel: Fly ash cenospheres were impregnated in copper and manganese co-doped nano-TiO2 ethanol hydrosol. As the solvent ethanol evaporated, a wet gel of copper and manganese co-doped nano-TiO2 loaded with fly ash cenospheres was formed. The wet gel was dried at 80-90℃ to obtain a dry gel of copper and manganese co-doped nano-TiO2. S4: Sintering of floating catalyst dry gel: The dried gel was transferred to an alumina crucible and calcined at 600-700℃ for 1-3 hours. After cooling, the product with the chemical composition SO4 was obtained. 2- A floating catalyst consisting of / TiO2-CuO-Mn2O3 / fly ash cenospheres; its particle size is 30-100 mesh, acid strength H0≤-14.5, and specific gravity is 0.6-0.90 g / cm³. 3 Specific surface area is 10-50 m² 2 / g, with a mass composition of: TiO2 25%-30%, CuO 3%-10%, Mn2O3 6%-20%, S 0.02%-0.1%, and fly ash cenospheres 50%-60%.

3. A method for using the floating catalyst as described in claim 1 in the synthesis of p-hydroxyphenylhydantoin, characterized in that: It includes four parts, and the specific steps are as follows: T1: Synthesis of p-hydroxyphenylhydantoin: Organic solvent, phenol, urea, and floating catalyst particles are added to the reactor; then dilute sulfuric acid is added to make the sulfuric acid concentration in the reaction solution 0.5-1 mol / L; the molar ratio of glyoxylic acid, phenol, and urea added is controlled at 1:1-1.2:1-1.5; the mass of the floating catalyst particles added is 5%-20% of the total mass of the reaction solution; the reaction solution is heated to 60-120℃ and refluxed, and then a 50% glyoxylic acid aqueous solution is slowly added dropwise over 6-9 hours, and the water introduced by glyoxylic acid and generated in the reaction is evaporated by azeotropic distillation; p-hydroxyphenylhydantoin seed crystals are added, and the reaction is continued at this temperature for 2-3 hours to ensure the reaction is complete; the organic solvent is one of methanol, ethanol, dimethylformamide, tetrahydrofuran, or petroleum ether. T2: Solvent recovery and separation of reaction products: The organic solvent in the reactants is recovered by vacuum distillation and recycled; 3-6 times the amount of deionized water is added to the residual solids and stirred at 30-40℃ to disperse the solids; the floating catalyst particles float on the top of the aqueous solution, the p-hydroxyphenylhydantoin product powder precipitates at the bottom of the aqueous solution, and the by-products dissolve in the aqueous solution; T3: Recovery and activation of floating catalysts: Filter the floating catalyst particles through a 100-mesh screen, wash off the entrained product powder with water, and the catalyst can be recycled 5 times. After 5 recyclings, the catalyst activity is greatly reduced. Irradiate it under visible light for 8-12 hours to restore the catalytic activity, and then recycle it 5 more times. After 10 recyclings, immerse it in a 0.5-1.0 mol / L sulfuric acid aqueous solution for 8-12 hours, filter, dry, and calcine at 600-700℃ for 1-3 hours to restore the catalytic activity, and then recycle it. T4: Product Separation and Inspection The p-hydroxyphenylhydantoin product powder was separated from the aqueous solution, washed with hot water at 40-50℃ until the surface was no longer sticky, and then dried; the liquid chromatography purity of the product was 98.5%-99.5%; the molar yield of the product was 68%-72%.