A metal phosphate catalyst, its preparation and application

Abstract

This invention discloses a metal phosphate catalyst, its preparation, and its application. The catalyst comprises transition metal ions and phosphate ions, wherein the molar ratio of phosphorus to transition metal ions is 1:0.5-50. The catalyst preparation method includes the following steps: titrating an aqueous solution of a soluble transition metal salt with an aqueous phosphate solution, reacting at room temperature; filtering after the reaction at room temperature, drying the solid, and calcining to obtain the metal phosphate catalyst. This invention further applies the above catalyst to a method for the oxidation preparation of benzyl ketone, including the steps of: mixing the metal phosphate catalyst with a benzyl-containing aromatic hydrocarbon in a reaction vessel; then introducing high-pressure oxygen into the reaction vessel, heating and stirring to obtain benzyl ketone. The transition metal phosphate prepared by this invention does not depend on an auxiliary catalyst to exert its catalytic activity and can exhibit high catalytic activity under simple pressurized heating conditions, effectively improving the conversion rate of the oxidation reaction of benzyl-containing aromatic hydrocarbons.

Description

Technical Field

[0001] This invention relates to a metal phosphate catalyst, its preparation and application, and more particularly to a metal phosphate catalyst for catalyzing the oxidation of benzyl-containing aromatic hydrocarbons, its preparation and application. Background Technology

[0002] Industrially, there are two main methods for the oxidative synthesis of aromatic ketones using aryl alkanes (such as ethylbenzene) as substrates: the Friedel-Kaffs acylation reaction and the direct oxidation of ethylbenzene (EB). Because the Friedel-Kaffs acylation reaction easily generates wastewater or waste acid, the former method has been gradually replaced by the latter. However, the selective oxidation of the CH bond at the benzyl position of EB is quite difficult because its activation and cleavage typically require harsh conditions such as high temperature, high pressure, and alkaline or acidic environments. Currently, cobalt and other homogeneous catalysts are mainly used industrially to catalyze the reaction of EB with oxygen.

[0003] For example, Japanese Patent JPH07196573A discloses a method for catalytic oxidation of ethylbenzene to acetophenone using cobalt acetate as the main catalyst and rhenium halide as the auxiliary catalyst in the presence of oxygen. This method relies on metal halides as auxiliary catalysts and suffers from numerous problems, including a complex catalytic system, low conversion rate, difficulty in catalyst recovery, and difficulty in product separation, which hinders its industrial application.

[0004] Furthermore, Chinese patent CN114855192A discloses a method for the electrochemical oxidation of benzyl ketones / aldehydes using a transition metal oxide catalyst. The method includes: using an electrode supported on a transition metal oxide catalyst as the anode, selectively electrochemically oxidizing the benzyl carbon-hydrogen bond to a carbonyl group in a water / organic solvent mixed solution containing an electrolyte to prepare the corresponding benzyl ketone / aldehyde compound. The transition metal is one or more selected from cobalt, nickel, tungsten, zirconium, molybdenum, lanthanum, cerium, chromium, samarium, iron, titanium, ruthenium, and vanadium. This method features mild reaction conditions, uses inexpensive transition metal oxides as recyclable heterogeneous electrocatalysts, water as the solvent and oxygen source, and does not use toxic reagents, making it safe and environmentally friendly. Simultaneously, the reaction exhibits high conversion rate and selectivity. Although the patent discloses that acetophenone can be prepared by catalyzing the oxidation of ethylbenzene using transition metal oxides as catalysts, the conversion rate of acetophenone is low. Moreover, the method relies on a complex electrochemical reaction system, involving the selection of complex electrochemical parameters and the preparation of positive and negative electrode materials. It also requires the selection of an appropriate water / organic solvent mixture containing electrolyte as an electrolyte, making the overall preparation steps cumbersome, the reaction conditions harsh, and the pollution risk and waste disposal costs significantly increased, making it difficult to apply industrially. Summary of the Invention

[0005] Objectives of this invention: The objective of this invention is to provide a metal phosphate catalyst that addresses the problems of existing catalysts relying on complex catalytic systems and exhibiting low catalytic activity and conversion rates. Another objective is to propose a method for preparing a metal phosphate catalyst, thus solving the problem of how to prepare metal phosphate catalysts. A third objective is to provide an application of a metal phosphate catalyst in the oxidation of benzyl ketones, addressing the problem of how to improve the conversion rate of benzyl-containing aromatic hydrocarbon oxidation reactions.

[0006] Technical solution: The metal phosphate catalyst of the present invention comprises transition metal ions and phosphate ions, wherein the molar ratio of phosphorus to transition metal ions is 1:0.5-50.

[0007] This invention utilizes a combination of phosphate ions and transition metal ions to obtain a catalyst that effectively improves substrate conversion under simple pressurized heating conditions without an auxiliary catalyst. Compared to other oxyacid anions such as nitrate, acetate, and sulfate ions, phosphate ions can better increase the acid content of the catalyst. Combining them with appropriate metal ions can further enhance the acid content. Since the acid content of the catalyst is positively correlated with its catalytic activity, this invention exhibits superior catalytic activity.

[0008] Preferably, the transition metal ion includes at least one of Cu, Cd, La, Cr, Mn, Al, Zr, Ni, and Co.

[0009] Preferably, the transition metal ions are Cd and Co ions in a molar ratio of 1-10:1-10 or Zr and La ions in a molar ratio of 1-10:1-10. Certain specific combinations of transition metal ions can significantly enhance the catalytic activity of the catalyst, producing synergistic effects, such as CdCoP or ZrLaP.

[0010] To obtain the above-mentioned metal phosphate catalyst, the present invention provides a method for preparing a metal phosphate catalyst, comprising the following steps:

[0011] (1) Titrate the aqueous solution of a transition metal soluble salt with an aqueous phosphate solution at room temperature;

[0012] (2) After the reaction at room temperature, filter the solid, dry it, and then calcine it to obtain the metal phosphate catalyst.

[0013] Preferably, in step (1), the transition metal soluble salt includes at least one chloride salt or oxyacid salt of a transition metal, the oxyacid salt includes at least one of nitrate, sulfate, acetate and propionate, and the phosphate contains at least one of phosphate ion, hydrogen phosphate ion and dihydrogen phosphate ion.

[0014] Preferably, the molar ratio of the phosphate to the transition metal soluble salt is 1:0.5-50; the transition metal soluble salt is cobalt chloride and cadmium chloride with a molar ratio of 1-10:1-10; or zirconium chloride and lanthanum chloride with a molar ratio of 1-10:1-10. The molar ratio is preferably 1:1.

[0015] Preferably, in step (1), the phosphate aqueous solution is used to titrate the transition metal soluble salt aqueous solution. The reaction method at room temperature is as follows: at 40-80℃, the phosphate aqueous solution is uniformly added dropwise to an equal volume and concentration of the transition metal soluble salt aqueous solution. After titration, the solution is heated under reflux for 1-3 hours and stirred at room temperature for 5-24 hours. In step (2), the solid drying conditions are drying at 60-120℃ for 1-10 hours and calcination conditions are calcination at 200-700℃ for 2-8 hours. The heating rate during calcination is 5-10℃ / min.

[0016] The present invention further applies the above-mentioned metal phosphate catalyst to the method of oxidative preparation of benzyl ketone.

[0017] The above-mentioned method for preparing benzyl ketone by oxidation includes the following steps:

[0018] (11) The metal phosphate catalyst and the benzyl-containing aromatic hydrocarbon are added into the reaction vessel and mixed;

[0019] (21) High-pressure oxygen is then introduced into the reaction vessel, and the reaction is heated and stirred to obtain benzyl ketone. The general reaction formula is as follows:

[0020]

[0021] Among them, R1 and R2 are independently selected from hydrogen and C. 1-6 alkyl, One of them, R3 is selected from C 1-6 alkyl.

[0022] Preferably, in step (21), the benzyl-containing aromatic hydrocarbon includes one or more of ethylbenzene, ethylbenzene derivatives, methyl phenylacetate, and methyl phenylacetate derivatives; the ratio of the metal phosphate catalyst to the benzyl-containing aromatic hydrocarbon is 0.01-0.1 g: 5 mL; the oxygen pressure in the reactor is 0.5-2 MPa, the reaction time is 4-18 h, the reaction temperature is 90-150 °C, and the stirring speed is 200-1000 rpm.

[0023] Beneficial Effects: Compared with existing technologies, this invention has the following significant advantages: The transition metal phosphates prepared by this invention do not depend on auxiliary catalysts to exert catalytic activity, and can exhibit high catalytic activity under simple pressure and heating conditions, effectively improving the conversion rate of oxidation reactions containing benzyl aromatic hydrocarbons. This invention solves the problem that existing catalysts depend on complex reaction systems to exert catalytic activity, greatly simplifying the method for catalytic oxidation to prepare aromatic ketones, and is conducive to the industrial application of this method. Attached Figure Description

[0024] Figure 1 The NH3-TPD characterization diagrams are for the catalysts Co-P, Cd-P, MnAlP, LaCuP, CoCdP, and ZrLaP. Detailed Implementation

[0025] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0026] Example 1: A metal phosphate catalyst CoCdP, comprising Co ions, Cd ions and phosphate ions, wherein the molar ratio of phosphorus to Co ions to Cd ions is 2:1:1.

[0027] The preparation method of CoCdP catalyst is as follows:

[0028] 0.024 mol of (NH4)3PO4·4H2O was dissolved in 20 mL of deionized water to obtain an ammonium phosphate solution. 0.012 mol of cobalt chloride and 0.012 mol of cadmium chloride were added to a 100 mL round-bottom flask and dissolved in 20 mL of deionized water. The ammonium phosphate solution was then added to a low-pressure liquid funnel at atmospheric pressure and uniformly dropped into the round-bottom flask. The mixture was heated under reflux at 50 °C for 2 h, followed by stirring at room temperature for 6 h. The mixture was filtered and washed three times, dried at 110 °C for 5 h, calcined at 300 °C for 2 h, calcined at 450 °C for 2 h, and calcined at 600 °C for 4 h, with a heating rate of 5 °C / min during calcination, to obtain a Co:Cd (1:1) phosphate catalyst.

[0029] Example 2: A metal phosphate catalyst CoCdP, comprising Co ions, Cd ions and phosphate ions, wherein the molar ratio of phosphorus to Co ions to Cd ions is 1:1:1.

[0030] The preparation method of CoCdP catalyst is as follows:

[0031] 0.012 mol of (NH4)3PO4·4H2O was dissolved in 20 mL of deionized water to obtain an ammonium phosphate solution. 0.012 mol of cobalt chloride and 0.012 mol of cadmium chloride were added to a 100 mL round-bottom flask and dissolved in 20 mL of deionized water. The ammonium phosphate solution was then added to a low-pressure liquid funnel at atmospheric pressure and uniformly dropped into the round-bottom flask. The mixture was heated under reflux at 50 °C for 2 h, followed by stirring at room temperature for 12 h. The mixture was filtered and washed three times, dried at 120 °C for 1 h, calcined at 200 °C for 2 h, calcined at 450 °C for 2 h, and calcined at 700 °C for 2 h, with a heating rate of 10 °C / min during calcination, to obtain a Co:Cd (1:1) phosphate catalyst.

[0032] Example 3: A metal phosphate catalyst CoCdP, comprising Co ions, Cd ions and phosphate ions, wherein the molar ratio of phosphorus to Co ions to Cd ions is 4:1:1.

[0033] The preparation method of CoCdP catalyst is as follows:

[0034] 0.048 mol of (NH4)3PO4·4H2O was dissolved in 20 mL of deionized water to obtain an ammonium phosphate solution. 0.012 mol of cobalt chloride and 0.012 mol of cadmium chloride were added to a 100 mL round-bottom flask and dissolved in 20 mL of deionized water. The ammonium phosphate solution was then added to a low-pressure liquid funnel at atmospheric pressure and uniformly dropped into the round-bottom flask. The mixture was heated under reflux at 50 °C for 2 h, followed by stirring at room temperature for 24 h. The mixture was filtered and washed three times, dried at 60 °C for 10 h, calcined at 300 °C for 1 h, calcined at 450 °C for 0.5 h, and calcined at 600 °C for 0.5 h, with a heating rate of 5 °C / min during calcination, to obtain a Co:Cd (1:1) phosphate catalyst.

[0035] Example 4: The rest is the same as in Example 1, except that (NH4)3PO4·4H2O is replaced with disodium hydrogen phosphate in equal molar amounts, cobalt chloride is replaced with cobalt sulfate, and cadmium chloride is replaced with cadmium sulfate.

[0036] Example 5: The rest is the same as in Example 1, except that (NH4)3PO4·4H2O is replaced with sodium dihydrogen phosphate in equal molar form, cobalt chloride is replaced with cobalt nitrate, and cadmium chloride is replaced with cadmium nitrate.

[0037] Example 6: The rest is the same as in Example 1, except that cobalt chloride is replaced with manganese chloride and cadmium chloride is replaced with aluminum chloride to prepare catalyst MnAlP.

[0038] Example 7: The rest is the same as in Example 1, except that cobalt chloride is replaced with manganese chloride and cadmium chloride is replaced with cerium chloride to prepare catalyst MnCeP.

[0039] Example 8: The rest is the same as in Example 1, except that cadmium chloride is replaced with aluminum chloride to prepare the catalyst CoAlP.

[0040] Example 9: The rest is the same as in Example 1, except that cadmium chloride is replaced with chromium chloride to prepare the catalyst CoCrP.

[0041] Example 10: The rest is the same as in Example 1, except that cobalt chloride is replaced with copper chloride and cadmium chloride is replaced with lanthanum chloride to prepare the catalyst CuLaP.

[0042] Example 11: The rest is the same as in Example 1, except that cobalt chloride is replaced with zirconium chloride to prepare the catalyst ZrCdP.

[0043] Example 12: The rest is the same as in Example 1, except that cobalt chloride is replaced with zirconium chloride and cadmium chloride is replaced with lanthanum chloride to prepare the catalyst ZrLaP.

[0044] Example 13: A metal phosphate catalyst Mn-P, comprising Mn ions and phosphate ions, wherein the molar ratio of phosphorus to Mn ions is 1:1.

[0045] The preparation method of Mn-P catalyst is as follows:

[0046] 0.024 mol of (NH4)3PO4·4H2O was dissolved in 20 mL of deionized water to obtain an ammonium phosphate solution. 0.024 mol of manganese chloride was added to a 100 mL round-bottom flask and dissolved in 20 mL of deionized water. The ammonium phosphate solution was then added to a low-pressure liquid funnel at atmospheric pressure and uniformly dropped into the round-bottom flask. The mixture was heated under reflux at 50 °C for 2 h, followed by stirring at room temperature for 6 h. The mixture was filtered and washed three times, dried at 110 °C for 5 h, calcined at 300 °C for 2 h, calcined at 450 °C for 2 h, and calcined at 600 °C for 4 h, with a heating rate of 5 °C / min during calcination, to obtain a single-metal elemental phosphate catalyst.

[0047] Example 14: The rest is the same as in Example 13, except that manganese chloride is replaced with aluminum chloride to prepare catalyst Al-P.

[0048] Example 15: The rest is the same as in Example 13, except that manganese chloride is replaced with cobalt chloride to prepare the catalyst Co-P.

[0049] Example 16: The rest is the same as in Example 13, except that manganese chloride is replaced with cerium chloride to prepare the catalyst Ce-P.

[0050] Example 17: The rest is the same as in Example 13, except that manganese chloride is replaced with lanthanum chloride to prepare the catalyst La-P.

[0051] Example 18: The rest is the same as in Example 13, except that manganese chloride is replaced with cadmium chloride to prepare the catalyst Cd-P.

[0052] Example 19: The rest is the same as in Example 13, except that manganese chloride is replaced with zirconium chloride to prepare the catalyst Zr-P.

[0053] Example 20: The rest is the same as in Example 13, except that manganese chloride is replaced with nickel chloride to prepare the catalyst La-P.

[0054] Example 21: The rest is the same as in Example 13, except that manganese chloride is replaced with copper chloride to prepare the catalyst Cu-P.

[0055] Example 22: This example examines the catalytic activity of the catalysts prepared in the above examples in catalytic oxidation reactions.

[0056] The catalytic oxidation reaction was carried out in a 50 mL high-pressure reactor equipped with a magnetic stirrer. The general reaction formula is as follows:

[0057]

[0058] The raw materials are as follows: ethylbenzene or methyl phenylacetate is a benzyl-containing aromatic substrate; the catalyst dosage is 0.03 g; and the amount of ethylbenzene or methyl phenylacetate is 5 mL. The mixture is heated in a constant-temperature oil bath at 130°C, air is purged, and oxygen is introduced at 1 MPa. The mixture is magnetically stirred at 800 r / min for 10 h. The results are as follows:

[0059] Table 1 Catalytic activity of different mono / bimetallic phosphate catalysts in catalytic oxidation reactions.

[0060]

[0061] As shown in Table 1, the conversion rate and selectivity of some bimetallic phosphates are significantly higher than those of monometallic phosphates, indicating that the catalytic activity of some bimetallic phosphates is significantly better than that of monometallic phosphates.

[0062] Further NH3-TPD characterization was performed on catalysts Co-P, Cd-P, MnAlP, LaCuP, CoCdP, and ZrLaP, such as... Figure 1 ( Figure 1(The horizontal axis represents temperature, and the vertical axis represents signal intensity.) As shown in Table 2, the Co-P curve exhibits strong acid sites near 400℃ with an acid content of 0.67 mmol / g; the Cd-P curve also shows strong acid sites near 400℃ with an acid content of 0.71 mmol / g; the MnAlP curve shows weak acid sites at 85℃ and 130℃ with an acid content of 1.42 mmol / g; the LaCuP curve shows moderately strong acid sites near 300℃ and 400℃ with an acid content of 2.14 mmol / g; and the CoCdP curve shows weak acid sites near 108℃, moderately strong acid sites near 300℃, and strong acid sites near 500℃ with an acid content of 3.23 mmol / g. It can be seen that the higher the acid content, the stronger the oxidation performance and the better the catalytic activity of the catalyst.

[0063] Table 2 Acid content of acidic sites on catalysts

[0064]

[0065] Example 23: Investigating the effect of temperature on catalytic oxidation reaction

[0066] 5 ml of ethylbenzene and 0.03 g of Co:Cd (1:1) cobalt cadmium phosphate prepared in Example 1 were sequentially added to a high-pressure reactor, and oxygen was introduced at 1 MPa. The mixture was stirred and heated to the temperature shown in Table 3 at a stirring speed of 600 rpm. The reaction was stopped after 10 h, and the reactor was cooled to room temperature. The reaction solution was centrifuged and analyzed using a gas chromatograph (GC 9560). The GC detection results are shown in Table 3.

[0067] Table 3 Effect of temperature on catalytic oxidation reaction

[0068]

[0069] Example 24: Investigating the effect of catalyst dosage on catalytic oxidation

[0070] 5 mL of ethylbenzene and the Co:Cd (1:1) phosphate prepared in Example 1 were sequentially added to a high-pressure reactor, and oxygen was introduced. The amount of catalyst used is shown in Table 4. The reaction temperature was 130 °C, the reaction pressure was 1 MPa, and the stirring speed was 600 rpm. The reaction was stopped after 10 h. The reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed by gas chromatography (GC 9560). The GC detection results are shown in Table 4.

[0071] Table 4 Effect of catalyst dosage on catalytic oxidation

[0072]

[0073]

[0074] Example 25: Effect of reaction pressure on catalytic oxidation

[0075] 5 ml of ethylbenzene and 0.03 g of the Co:Cd (1:1) phosphate prepared in Example 1 were sequentially added to a high-pressure reactor, and oxygen was introduced. The pressure was maintained as shown in Table 5 during the reaction. The reaction temperature was 130 °C, and the stirring speed was 1000 rpm. The reaction was stopped after 10 h. The reactor was cooled to room temperature, and the reaction solution was centrifuged and analyzed using a gas chromatograph (GC9560). The GC detection results are shown in Table 5.

[0076] Table 5 Effect of reaction pressure on catalytic oxidation

[0077]

[0078] Example 26: Investigating the effect of reaction time on catalytic oxidation reaction

[0079] 5 mL of ethylbenzene and 0.03 g of the Co:Cd (1:1) phosphate prepared in Example 1 were sequentially added to a high-pressure reactor, and oxygen was introduced. The reaction time is shown in Table 6. The reaction temperature was 130 °C, the reaction pressure was 1 MPa, and the stirring speed was 600 rpm. After the reaction was stopped, the reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed using a gas chromatograph (GC9560). The GC detection results are shown in Table 6.

[0080] Table 6. Effect of reaction time on catalytic oxidation reaction

[0081]

[0082] Example 27: Effect of Bimetallic Ratio on Catalytic Oxidation Reaction

[0083] 5 mL of ethylbenzene and 0.03 g of CoCdP phosphate prepared according to the method of Example 1 or ZrLaP phosphate prepared according to the method of Example 12 were sequentially added to a high-pressure reactor, and oxygen was introduced. The bimetallic ratio is shown in Table 7. The reaction temperature is 130 °C, the reaction pressure is 1 MPa, the stirring speed is 600 rpm, and the reaction is carried out for 10 h. After the reaction is cooled to room temperature, the reaction solution is centrifuged and analyzed by gas chromatography (GC9560). The GC detection results are shown in Table 7.

[0084] Table 7 Effect of Bimetallic Ratio on Catalytic Oxidation Reaction

[0085]

[0086] Comparative Example 1: The rest is the same as in Example 13, except that (NH4)3PO4·4H2O is replaced with (NH4)3NO4 in equal molar amounts to prepare Mn-N nitrate catalyst.

[0087] Comparative Example 2: The rest is the same as in Example 13, except that (NH4)3PO4·4H2O is replaced with (NH4)2C2O4 in equal molar amounts to obtain Mn-C oxalate catalyst.

[0088] Comparative Example 3: The rest is the same as in Example 13, except that (NH4)3PO4·4H2O is replaced with (NH4)2SO4 in equal molar amounts to prepare Mn-S sulfate catalyst.

[0089] Comparative Example 4: The rest is the same as in Example 13, except that (NH4)3PO4·4H2O is replaced with ammonium acetate in equal molar amounts to prepare Mn-CH acetate catalyst.

[0090] Acetophenone was prepared according to the method in Example 22, and the catalytic activity of the catalysts prepared in Comparative Examples 1-4 and Example 13 in the catalytic oxidation reaction was investigated. The results are as follows:

[0091] Table 8 Catalytic activity of different single-metal catalysts in catalytic oxidation reactions.

[0092]

[0093] As shown in Table 8, the catalyst prepared with phosphate has the best catalytic effect, and its acid content is also significantly higher than that of the catalysts prepared with the other four oxyacid salts.

[0094] Example 28: The rest is the same as in Example 1, except that cadmium chloride is replaced with manganese chloride to prepare the catalyst MnCoP.

[0095] Comparative Example 5: The rest is the same as in Example 28, except that (NH4)3PO4·4H2O is replaced with (NH4)3NO4 in equal molar amounts to prepare MnCoN nitrate catalyst.

[0096] Comparative Example 6: The rest is the same as in Example 28, except that (NH4)3PO4·4H2O is replaced with (NH4)2C2O4 in equal molar amounts to obtain the MnCoC oxalate catalyst.

[0097] Comparative Example 7: The rest is the same as in Example 28, except that (NH4)3PO4·4H2O is replaced with (NH4)2SO4 in equal molar amounts to prepare MnCoS sulfate catalyst.

[0098] Comparative Example 8: The rest is the same as in Example 28, except that (NH4)3PO4·4H2O is replaced with ammonium acetate in equal molar amounts to prepare MnCoCH acetate catalyst.

[0099] Acetophenone was prepared according to the method in Example 22, and the catalytic activity of the catalysts prepared in Comparative Examples 5-8 and Example 13 in the catalytic oxidation reaction was investigated. The results are as follows:

[0100] Table 9 Catalytic activity of different bimetallic catalysts in catalytic oxidation reactions.

[0101]

[0102]

[0103] As can be seen from the results in Table 9, the catalytic activity of the manganese-cobalt bimetallic catalysts is generally low. In particular, the catalytic effect of the catalyst prepared by phosphate is lower than that of the catalysts prepared by the other four oxyacid salts.

[0104] Example 29: 5 mL of benzyl-containing aromatic hydrocarbon and 0.03 g of Co:Cd (1:1) cobalt cadmium phosphate prepared in Example 1 were sequentially added to a high-pressure reactor, and oxygen was introduced at 1 MPa. The mixture was stirred and heated to 130 °C at a stirring speed of 600 rpm. The reaction was stopped after 10 h, and the reactor was cooled to room temperature. The reaction solution was centrifuged and analyzed using a gas chromatograph (GC 9560). The GC detection results are shown in Table 10.

[0105] Table 10. Conversion rates of catalysts for different reaction substrates

[0106]

[0107] Table 10 shows that cobalt-cadmium phosphate has a high conversion rate for various benzyl-containing aromatic hydrocarbons, indicating that the present invention has good catalytic performance for the oxidation of CH bonds at the benzyl position.

[0108] Example 30: A cobalt-cadmium phosphate catalyst was prepared using the method described in Example 1. The effect of the ratio of phosphorus to metal elements on catalyst performance was investigated, with the amounts of ammonium phosphate, cobalt chloride, and cadmium chloride as variables. The amounts of ammonium phosphate, cobalt chloride, and cadmium chloride are shown in Table 11.

[0109] Table 11 Effect of the ratio of phosphorus to metal elements on catalyst performance

[0110]

[0111]

[0112] As shown in Table 11, phosphorus can catalyze oxidation reactions when the ratio of phosphorus to metal elements is between 1:0.5 and 50.

Claims

1. A metal phosphate catalyst, characterized in that, It contains transition metal ions and phosphate ions, wherein the molar ratio of phosphorus to transition metal ions is 1:0.5-50; the transition metal ions are Cd ions and Co ions with a molar ratio of 1-10:1-10 or Zr ions and La ions with a molar ratio of 1-10:1-10.

2. The method for preparing the metal phosphate catalyst according to claim 1, characterized in that, Includes the following steps: (1) Titrate an aqueous solution of a transition metal soluble salt with an aqueous phosphate solution at room temperature; (2) After the reaction at room temperature, filter the solid, dry it, and then calcine it to obtain the metal phosphate catalyst.

3. The method for preparing the metal phosphate catalyst according to claim 2, characterized in that, In step (1), the transition metal soluble salt includes at least one chloride salt or oxyacid salt of a transition metal, the oxyacid salt includes at least one of nitrate, sulfate, acetate and propionate, and the phosphate contains at least one of phosphate ion, hydrogen phosphate ion and dihydrogen phosphate ion.

4. The method for preparing the metal phosphate catalyst according to claim 2, characterized in that, The molar ratio of the phosphate to the transition metal soluble salt is 1:0.5-50; the transition metal soluble salt is cobalt chloride and cadmium chloride with a molar ratio of 1-10:1-10; or zirconium chloride and lanthanum chloride with a molar ratio of 1-10:1-10.

5. The method for preparing the metal phosphate catalyst according to claim 2, characterized in that, In step (1), the phosphate aqueous solution is used to titrate the transition metal soluble salt aqueous solution. The reaction method at room temperature is as follows: at 40-80℃, the phosphate aqueous solution is uniformly added dropwise to an equal volume and concentration of the transition metal soluble salt aqueous solution. After titration, the solution is heated under reflux for 1-3 hours and stirred at room temperature for 5-24 hours. In step (2), the solid drying conditions are drying at 60-120℃ for 1-10 hours and calcination conditions are calcination at 200-700℃ for 2-8 hours. The heating rate during calcination is 5-10℃ / min.

6. The application of the metal phosphate catalyst as described in claim 1 in the oxidative preparation of benzyl ketone.

7. The application according to claim 6, characterized in that, Includes the following steps: (11) The metal phosphate catalyst and the benzyl-containing aromatic hydrocarbon are added into the reaction vessel and mixed; (21) High-pressure oxygen is then introduced into the reactor, and the reaction is heated and stirred to obtain benzyl ketone. The general reaction formula is as follows: R1 and R2 are independently selected from hydrogen and C. 1-6 alkyl, One of them, R3 is selected from C 1-6 alkyl.

8. The application according to claim 7, characterized in that, In step (21), the benzyl-containing aromatic hydrocarbon includes one or more of ethylbenzene, ethylbenzene derivatives, methyl phenylacetate, and methyl phenylacetate derivatives; the ratio of the metal phosphate catalyst to the benzyl-containing aromatic hydrocarbon is 0.01-0.1 g: 5 mL; the oxygen pressure in the reactor is 0.5-2 MPa, the reaction time is 4-18 h, the reaction temperature is 90-150 °C, and the stirring speed is 200-1000 rpm.

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