Metal phosphate catalyst, preparation method thereof and application of metal phosphate catalyst in Friedel-Crafts reaction

Abstract

The invention discloses a metal phosphate catalyst as well as a preparation method and application thereof in Friedel-Crafts reaction. The catalyst is composed of transition metal ions and phosphate ions, the molar ratio of phosphorus to the transition metal elements is 1: (0.5-7), the total acid amount of the catalyst is in positive correlation with the catalytic activity, and the higher the total acid amount is, the better the reaction effect is. The preparation method comprises the following steps: dissolving a transition metal soluble salt in deionized water, adding a phosphate aqueous solution, stirring to generate a precipitate, dropwise adding nitric acid to dissolve the precipitate, adding urea to obtain a mixed solution, and carrying out hydrothermal reaction, washing, suction filtration and drying to obtain a finished product. During application, the catalyst, phenol and alcohol are put into an intermittent reaction kettle, nitrogen is introduced to maintain stable pressure, heating and stirring reaction are performed, and an alkylphenol product is directly obtained. The catalyst is excellent in catalytic performance, mild in reaction condition and convenient to operate, the alcohol conversion rate and the selectivity of target alkylphenol can be effectively increased, meanwhile, the high conversion rate of acyl chloride is achieved in the acylation process, the process economy is improved, and an efficient and feasible technical scheme is provided for the Friedel-Crafts reaction.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous catalysis technology, and particularly relates to a metal phosphate catalyst, its preparation method, and its application in the Friedel-Crafts reaction. Background Technology

[0002] The Friedel-Crafts reaction, discovered in 1877, is an aromatic electrophilic substitution reaction, primarily comprising two types: alkylation and acylation. This reaction introduces alkyl or acyl groups into the aromatic ring and is one of the key methods for constructing carbon-carbon bonds. Alkylation reactions commonly use halogenated alkanes or alkenes as alkylating agents, but are prone to carbocation rearrangement and polyalkylation; acylation, on the other hand, uses acyl halides or acid anhydrides as reagents, producing ketones with well-defined structures that are less prone to rearrangement. Both methods provide fundamental pathways for aromatic ring functionalization, but both face challenges in industrial applications such as catalyst recovery and low conversion rates. These two types of reactions are widely used in the fine chemical industry. The Friedel-Crafts reaction is widely applied in pharmaceuticals, pesticides, dyes, fragrances, and other fine chemical fields, especially the Friedel-Crafts alkylation reaction, which is a key technological pathway for the synthesis of alkylphenol compounds.

[0003] Industrially, there are two main methods for synthesizing alkylphenols from phenol and alcohols via Friedel-Crafts alkylation: the traditional homogeneous acid catalysis method and the heterogeneous solid-state acid catalysis method. The traditional homogeneous acid catalysis method generates large amounts of waste acid and wastewater, and the equipment is highly corrosive. Currently, the former method is gradually being replaced by the latter. However, in the Friedel-Crafts alkylation reaction of phenol and alcohol, the electron-donating effect of the hydroxyl group on the phenol benzene ring easily leads to the formation of polyalkylation products, and the alcohol needs to undergo dehydration under catalysis to form a carbocation. This process typically requires harsh conditions such as high temperature, strong acid media, or long reaction times. Simultaneously, the carbocation is prone to rearrangement reactions, leading to a decrease in the selectivity of the target product. Chinese patent CN112320781A discloses a catalyst using mesoporous SiO2 as a support to support heteropoly acids (phosphomolybdic acid, silicotungstic acid) for the alkylation reaction of phenol and tert-butanol. Although it solves the problem of heteropoly acid desorption and loss (activity decreases by less than 20% after 150 hours of continuous operation), the weak acidity of mesoporous SiO2 results in a phenol conversion rate of only 50%-65%. Furthermore, the preparation of the mesoporous support requires the use of surfactant templates (such as hexadecyltrimethylammonium bromide), and the subsequent removal of the template requires high-temperature calcination, increasing the complexity of the process. Another literature reports the use of ion exchange resins as catalysts, which have the advantages of low corrosivity and recyclability. However, the resins are prone to swelling and framework collapse above 100°C, limiting the increase in reaction temperature and resulting in an alcohol conversion rate of less than 60%, which is difficult to meet the reaction efficiency requirements of industrial production.

[0004] Chinese patent CN102125868A discloses a method for catalyzing the Friedel-Crafts alkylation reaction of phenol and fatty alcohol using Fe-ZSM-5 molecular sieve catalyst. The method includes: using synthesized Fe-ZSM-5 microporous zeolite as a catalyst, mixing phenol and alcohol at a certain molar ratio under nitrogen protection, and reacting at 120-180℃ for 3-5 h to prepare the corresponding monoalkylphenol. This catalyst is obtained by supporting silicon atoms in the ZSM-5 molecular sieve framework with Fe, and has advantages such as recyclability, no waste acid emission, and environmental friendliness. It also inhibits carbocation rearrangement reactions to some extent. Although this patent discloses the use of molecular sieves as heterogeneous catalysts to catalyze the Friedel-Crafts alkylation reaction of phenol and alcohol to prepare alkylphenols, the phenol conversion rate is low (maximum only 12.2%). Furthermore, this method relies on a complex molecular sieve modification process (requiring precise control of the Fe / Si ratio), strict control of the nitrogen protection atmosphere and high reaction temperature, and a reaction time of several hours. This makes the overall preparation steps cumbersome, energy-intensive, and the catalyst preparation cost high, thus hindering industrial application. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the primary objective of this invention is to provide a metal phosphate catalyst that solves the problems of severe pollution, strong corrosiveness, difficulty in recovery, and low selectivity and catalytic activity of existing Friedel-Crafts alkylation reaction catalysts.

[0006] The second objective of this invention is to provide a method for preparing metal phosphate catalysts, thereby solving the problems of complex preparation processes, high costs, and poor stability of existing solid acid catalysts.

[0007] The third objective of this invention is to provide an application of metal phosphate catalysts in the Friedel-Crafts alkylation of phenols and alcohols and the acylation of aromatic compounds with acyl chlorides, thereby solving the problems of how to improve the conversion rate of alcohols or acyl chlorides, the selectivity of target alkylphenols, and the economic efficiency of the process under mild conditions.

[0008] To address the problems in the existing technology, the technical solution adopted by this invention is as follows: A method for preparing a metal phosphate catalyst involves dissolving a soluble salt of a transition metal in deionized water, adding an aqueous phosphate solution, and stirring for 10-50 min to produce a precipitate. Nitric acid solution is then added dropwise to the precipitate system to dissolve the precipitate, and after stirring for 5-30 min, urea is added to obtain a mixed solution. The mixed solution is subjected to a hydrothermal reaction, and after the reaction is completed, the catalyst is washed, filtered, and dried to obtain the metal phosphate catalyst.

[0009] Preferably, the transition metal soluble salt comprises at least one chloride salt or oxyacid salt of a transition metal, and the transition metal is one or more of Co, Cr, Mn, Ti, Fe, Ho, Zr, and Ce.

[0010] More preferably, the oxyacid salt includes at least one of nitrate, sulfate, acetate and propionate.

[0011] More preferably, the phosphate contains one or more of phosphate ions, hydrogen phosphate ions, and dihydrogen phosphate ions.

[0012] Preferably, when the transition metal soluble salt is composed of two metal salts, the molar ratio of the two metal salts is 3-8:3-8.

[0013] More preferably, the transition metal soluble salt is composed of chromium nitrate and zirconium nitrate mixed in a molar ratio of 3-8:3-8.

[0014] Preferably, the molar ratio of the transition metal soluble salt to the phosphate is 1:0.5-7.

[0015] Preferably, the concentration of the nitric acid solution is 5-20 mol / L, and the molar ratio of the nitric acid solution to the transition metal ions is 1-3:1.

[0016] Preferably, the molar ratio of urea to transition metal ions is 3-6:1.

[0017] Preferably, the hydrothermal reaction conditions are constant temperature reaction at 90-140℃ for 6-36 h, washing with water 3 times, and drying at 80-140℃ to constant weight.

[0018] A metal phosphate catalyst was prepared by the above method.

[0019] Specifically, the metal phosphate catalysts of this invention preferably contain one or more of Co, Ti, and Cr. The phosphate structures formed by these transition metal ions and phosphate ions are stable, with uniformly distributed acidic sites, exhibiting stronger catalytic targeting for the Friedel-Crafts alkylation reaction of phenols and alcohols. The Co-P, Ti-P, and Cr-P catalyst particles prepared thus exhibit spherical particle agglomerates. Furthermore, when the transition metal ion is Co or Cr, the metal phosphates formed by these two ions show superior activity and selectivity in the catalytic reaction, further improving the yield of the target product. The Fe-P catalyst particles exhibit a polymorphic composite of spherical and plate-like epicrystalline structures, while the CeZrP and CrZrP catalyst particles exhibit irregular plate-like agglomerates.

[0020] The above-mentioned metal phosphate catalysts are used in the catalytic Friedel-Crafts reaction.

[0021] Preferably, the application is the preparation of alkylphenols, comprising the following steps: S1, 0.1-0.2 g of metal phosphate catalyst, phenol and alcohol are added to a batch reactor and mixed. The ratio of phenol to alcohol mixture is 1.56-5 g: 1 mL. The alcohol includes one or more of ethanol, isopropanol, tert-butanol and butanone. S2, nitrogen gas is introduced into the reactor to maintain a pressure of 1-2 MPa, and the mixture is heated at 150-190℃ and stirred at 200-800 rpm for 8-14 h to obtain alkylphenol.

[0022] Preferably, the application is a Friedel-Crafts acylation reaction for the preparation of aromatic ketones, comprising the following steps: S1: Add 0.1-0.2 g of metal phosphate catalyst, aromatic compound and acyl chloride to a batch reactor, wherein the volume ratio of aromatic compound to acyl chloride is 2-6:1; S2: Nitrogen gas is introduced into the reactor to maintain a pressure of 1-2 MPa, and the mixture is heated at 70-140℃ and stirred at 200-800 rpm for 6-14 h to obtain aromatic ketones.

[0023] Preferably, the aromatic compound is fluorobenzene, and the acyl chloride is p-fluorobenzoyl chloride.

[0024] Preferably, the aromatic compound is isobutylbenzene, and the acyl chloride is 2-chloropropionyl chloride.

[0025] Preferably, the aromatic compound is one or more of anisole and chlorobenzene, and the acyl chloride is acetyl chloride.

[0026] This invention utilizes a combination of transition metal ions and phosphate ions to form a catalyst, enabling highly efficient catalysis of Friedel-Crafts alkylation of phenols and alcohols, as well as Friedel-Crafts acylation of aromatic compounds and acyl chlorides, under mild pressure and heating conditions. Metal phosphates possess both suitable acid strength and abundant active metal sites. The acidic environment created by phosphate ions promotes the protonation and leaving of alcohol hydroxyl groups, while transition metal ions stabilize reaction intermediates and inhibit side reactions. This synergistic effect significantly enhances catalytic activity and target product selectivity, solving the problems of difficult acid strength control and numerous side reactions associated with traditional catalysts. Beneficial effects

[0027] Compared with existing technologies, the metal phosphate catalyst and its preparation method of the present invention, along with its application in the Friedel-Crafts reaction, have the following significant advantages: The Co-P, Ti-P, and Cr-P catalyst particles prepared by the present invention exhibit spherical particle agglomeration characteristics, the Fe-P catalyst has a composite structure with spherical and plate-like epicrystalline morphology, and CeZrP and CrZrP are irregular plate-like agglomerates. The unique structure endows the catalyst with high catalytic activity, enabling efficient catalysis of the Friedel-Crafts alkylation reaction of phenol and alcohol under simple heating and pressurization conditions. Among them, the product yield of the reaction of phenol and tert-butanol catalyzed by the single metal phosphate Co-P is nearly 61%, which greatly improves the product purity and effectively solves the problem of many side reactions in traditional catalysts. On the other hand, the Co-P catalyst also performs outstandingly in the reaction of fluorobenzene and p-fluorobenzoyl chloride, with an acyl chloride conversion rate of up to 88.9%.

[0028] In addition, the catalyst is non-corrosive and can be recovered by filtration after the reaction, making it reusable. This avoids the problem of liquid acid catalysts polluting equipment, significantly improving its environmental friendliness. At the same time, it solves the problem of traditional catalysts being easily deactivated, resulting in a longer service life. Combined with its simple and easy-to-operate process characteristics, it further reduces the cost of industrial production. Attached Figure Description

[0029] Figure 1 The NH3-TPD characterization diagrams for catalysts Co-P, Cr-P, Fe-P, Ti-P, CrZrP and CeZrP are shown, where a represents monometallic phosphates and b represents bimetallic phosphates.

[0030] Figure 2 The images show the SEM characterization of catalysts Co-P, Cr-P, Fe-P, Ti-P, CrZrP, and CeZrP, where a represents Co-P, b represents Ti-P, c represents Cr-P, d represents Fe-P, e represents CeZrP, and f represents CrZrP. Detailed Implementation

[0031] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0032] Example 1

[0033] A metal phosphate catalyst Co-P contains Co ions and phosphate ions, wherein the molar ratio of phosphorus to Co is 1:1.

[0034] The preparation method of Co-P catalyst is as follows: 0.01 mol cobalt nitrate was dissolved in 10 mL of deionized water. After complete dissolution, 0.01 mol diammonium hydrogen phosphate was added, and the mixture was stirred continuously for 10 min to form a precipitate. Then, 0.8 mL of nitric acid (65 wt%) was slowly added dropwise, and the mixture was stirred for another 5 min to completely dissolve the precipitate, yielding a clear solution. Next, 0.04 mol urea was added to this solution, and after thorough mixing, the resulting solution was subjected to a hydrothermal reaction at 100 °C for 20 h. After the reaction was complete, the product was filtered, washed three times with deionized water, and finally dried at 80 °C to constant weight.

[0035] Example 2

[0036] Except that disodium hydrogen phosphate is replaced with (NH4)3PO4•4H2O and cobalt nitrate is replaced with cobalt chloride, the rest is the same as in Example 1.

[0037] Example 3

[0038] Except that cobalt nitrate was replaced with chromium nitrate, the rest was the same as in Example 1, and the catalyst Cr-P was prepared.

[0039] Example 4

[0040] Except that cobalt nitrate was replaced with manganese nitrate, the rest was the same as in Example 1, and the catalyst Mn-P was prepared.

[0041] Example 5

[0042] Except that cobalt nitrate was replaced with titanium sulfate, the rest was the same as in Example 1, and the catalyst Ti-P was prepared.

[0043] Example 6

[0044] Except for replacing cobalt nitrate with copper chloride, the process was the same as in Example 1, and the catalyst Cu-P was prepared.

[0045] Example 7

[0046] Except for replacing cobalt nitrate with iron nitrate, the rest of the process was the same as in Example 1, and the catalyst Fe-P was prepared.

[0047] Example 8

[0048] Except for replacing cobalt nitrate with holmium nitrate, the rest of the process was the same as in Example 1, and the catalyst Ho-P was prepared.

[0049] Example 9

[0050] Except that cobalt nitrate was replaced with zinc nitrate, the rest was the same as in Example 1, and the catalyst Zn-P was prepared.

[0051] Example 10 Except that cobalt nitrate was replaced with zirconium nitrate, the rest was the same as in Example 1, and the catalyst Zr-P was prepared.

[0052] Example 11

[0053] Except that the amount of diammonium hydrogen phosphate was changed to 0.02 mol, i.e. the molar ratio of phosphorus to cobalt was 2:1, the rest was the same as in Example 1.

[0054] Example 12

[0055] Except for changing the amount of urea to 0.05 mol, the rest is the same as in Example 1, that is, urea and Co 2+ The molar ratio is 5.0.

[0056] Example 13

[0057] A metal phosphate catalyst CrZrP comprises Cr ions, Zr ions and phosphate ions, wherein the molar ratio of phosphorus:Cr:Zr is 2:1:1.

[0058] The preparation method of CrZrP catalyst is as follows: 0.005 mol chromium nitrate and 0.005 mol zirconium nitrate were dissolved in 10 mL of deionized water. After complete dissolution, 0.04 mol diammonium hydrogen phosphate was added, and the mixture was stirred continuously for 10 min to form a precipitate. Then, 0.8 mL of nitric acid was slowly added dropwise, and the mixture was stirred for another 5 min to completely dissolve the precipitate, yielding a clear solution. Next, 0.04 mol urea was added to this solution, and after thorough mixing, the resulting solution was subjected to a hydrothermal reaction at 100 °C for 20 h. After the reaction was complete, the product was filtered, washed three times with deionized water, and finally dried at 80 °C to constant weight.

[0059] Example 14

[0060] Except for replacing chromium nitrate with copper chloride and zirconium nitrate with cerium sulfate, the rest is the same as in Example 13, and the catalyst CuCeP is prepared.

[0061] Example 15

[0062] Except that zirconium nitrate was replaced with cobalt nitrate, the rest was the same as in Example 13, and the catalyst CoCrP was prepared.

[0063] Example 16

[0064] Except that zirconium nitrate was replaced with copper chloride, the rest was the same as in Example 14, and the catalyst CuCrP was prepared.

[0065] Example 17

[0066] Except that chromium nitrate was replaced with cerium nitrate, the rest was the same as in Example 14, and the catalyst CeZrP was prepared.

[0067] This embodiment investigates the catalytic activity of the catalysts prepared in the above embodiments in the Friedel-Crafts reaction. The specific steps are as follows: a metal phosphate catalyst, phenol, and an alcohol are added to a batch reactor and mixed; nitrogen gas is introduced into the reactor to maintain pressure, and the reaction is heated and stirred to obtain alkylphenols. The catalytic Friedel-Crafts reaction is carried out in a 100 mL high-pressure reactor equipped with a magnetic stirrer, and the general reaction formula is as follows:

[0068] The raw materials are as follows: butanone alcohol or tert-butanol; catalyst dosage: 0.1 g; phenol dosage: 3.85 g; butanone alcohol or tert-butanol dosage: 1 mL; heating in a constant temperature oil bath at 170℃; purging air and introducing nitrogen gas at 1 MPa; magnetic stirring at 600 r / min; reaction time: 10 h. The results are shown in Table 1.

[0069] Table 1 Catalytic activity of different mono / bimetallic phosphate catalysts in Friedel-Crafts alkylation reaction

[0070] As shown in Table 1, except for the zinc and copper salts which exhibited relatively low catalytic efficiency and selectivity, the other metal-based catalysts—monometallic Cr-P, Ti-P, Co-P, Fe-P, and bimetallic CrZrP and CeZrP—all demonstrated excellent catalytic activity. Among these, the Cr-P, Ti-P, and Co-P monometallic catalysts exhibited spherical particle agglomerates, while Fe-P displayed a composite structure with spherical and lamellar appendages. CeZrP and CrZrP catalysts, on the other hand, showed irregular lamellar agglomerates. These unique structures endowed the catalysts with high catalytic activity, which determines their application in Friedel-Crafts alkylation.

[0071] Further characterization of NH3-TPD was performed on catalysts Co-P, Cr-P, Ti-P, Fe-P, CrZrP, and CeZrP, such as... Figure 1 (The horizontal axis represents temperature, and the vertical axis represents signal strength) and as shown in Table 2.

[0072] Table 2 Acid content of acidic sites on catalysts

[0073] from Figure 1As shown in Table 2, the Co-P curve exhibits weak acid sites near 195℃ with an acid content of 830 μmol / g; the Cr-P curve shows weak acid sites near 205℃ with an acid content of 750 μmol / g; the Ti-P curve shows weak acid sites near 168℃ and 245℃ with an acid content of 500 μmol / g; the CrZrP curve shows weak acid sites at 78℃ and 151℃, moderately strong acid sites near 313℃, and a strong acid site at 549℃ with an acid content of 121 μmol / g; and the CeZrP curve shows weak acid sites near 122℃ and 247℃, and moderately strong acid sites near 384℃ with an acid content of 50 μmol / g. Therefore, a higher acid content results in better catalytic activity of the catalyst.

[0074] Example 18: Investigating the effect of temperature on the Friedel-Crafts alkylation reaction The Friedel-Crafts alkylation reaction of phenol with an alcohol was carried out in a stainless steel autoclave under a nitrogen atmosphere of 1 MPa. 0.1 g of Co-P prepared in Example 1, 3.85 g of phenol, and 1 ml of butanone alcohol were added sequentially to the autoclave, followed by purging with nitrogen three times and pressurization to 1 MPa at room temperature. The mixture was stirred and heated to the temperatures shown in Table 3 for 10 h at a stirring speed of 600 r / min. After the reaction, the reaction solution was separated using a high-speed centrifuge. The separated catalyst was then tested for reusability. Experimental data were analyzed using a gas chromatograph (GC 9560), and the results are shown in Table 3.

[0075] Table 3 Effect of temperature on Friedel-Crafts alkylation reaction

[0076] Example 19: Investigating the effect of catalyst dosage on Friedel-Crafts alkylation reaction The Friedel-Crafts alkylation reaction of phenol with an alcohol was carried out in a stainless steel autoclave under a nitrogen atmosphere of 1 MPa. Co-P prepared in Example 1, 3.85 g of phenol, and 1 ml of butanone were added sequentially to the autoclave. The catalyst amounts are shown in Table 4. The autoclave was purged three times with nitrogen and pressurized to 1 MPa at room temperature. The reaction was continuously stirred in an oil bath at 170°C for 10 h at a stirring speed of 600 r / min. After the reaction, the reaction solution was separated using a high-speed centrifuge. The separated catalyst was reusable and its performance was tested. Experimental data were analyzed using a gas chromatograph (GC 9560), and the results are shown in Table 4.

[0077] Table 4 Effect of catalyst dosage on Friedel-Crafts reaction

[0078] Example 20 Effect of reaction pressure on Friedel-Crafts alkylation reaction The Friedel-Crafts alkylation reaction of phenol with alcohols was carried out in a stainless steel autoclave. 0.1 g of Co-P prepared in Example 1, 3.85 g of phenol, and 1 ml of butanone were added sequentially to the autoclave, followed by purging three times with nitrogen. The reaction was then carried out in an oil bath at 170°C with continuous stirring for 10 h at a stirring speed of 600 r / min. The pressure maintained during the reaction is shown in Table 5. After the reaction, the reaction solution was separated using a high-speed centrifuge. The separated catalyst was then tested for reusability. Experimental data were analyzed using a gas chromatograph (GC 9560), and the results are shown in Table 5.

[0079] Table 5 Effect of reaction pressure on Friedel-Crafts reaction

[0080] Example 21: Investigating the effect of reaction time on the Friedel-Crafts reaction 1 mL of butanone alcohol, 3.85 g of phenol, and 0.1 g of the Co-P catalyst prepared in Example 1 were added to a high-pressure reactor and nitrogen gas was introduced. The reaction temperature was 170 °C, the reaction time was as shown in Table 6, the reaction pressure was 1 MPa, and the stirring speed was 600 r / min. After the reaction was stopped, the reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed by gas chromatography (GC9560). The GC detection results are shown in Table 6.

[0081] Table 6 Effect of reaction time on Friedel-Crafts reaction

[0082] Example 22 Effect of the ratio of phosphorus to transition metal elements on Friedel-Crafts alkylation reaction 1 mL of butanone alcohol, 3.85 g of phenol, and 0.1 g of the Co-P phosphate catalyst prepared in Example 1 or the Cr-P phosphate catalyst prepared according to the method in Example 7 were sequentially added to a high-pressure reactor, and nitrogen gas was introduced. The reaction temperature was 170 °C, the reaction time was 10 h, the reaction pressure was 1 MPa, and the stirring speed was 600 r / min. After the reaction was stopped, the reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed by gas chromatography (GC9560). The GC detection results are shown in Table 7.

[0083] Table 7 Effect of the molar ratio of phosphorus (P) to transition metal (M) on the Friedel-Crafts reaction.

[0084] As shown in Table 7, phosphorus and metal elements in a ratio of 1:0.5-7 can catalyze Friedel-Crafts alkylation reactions.

[0085] Example 23

[0086] Except for changing the hydrothermal time to 4h, 6h, 12h, 24h, 36h, and 48h, the rest are the same as in Example 1.

[0087] Raspberry ketone was prepared from phenol and butanone alcohol according to the method in Example 19. The catalytic activity of the catalysts prepared in Comparative Examples 1-4 and Example 1 in the Friedel-Crafts reaction was investigated. The results are as follows: Table 8 Catalytic activity of different hydrothermal times in the Friedel-Crafts reaction

[0088] As shown in Table 8, hydrothermal time of 6-36 h can catalyze Friedel-Crafts alkylation reaction, and the acid content is proportional to the yield of raspberry ketone.

[0089] Example 24

[0090] Using the Co-P phosphate prepared in Example 1, the effect of the ratio of urea to metal element on catalyst performance was investigated, with the amount of urea added as the variable. The results are shown in Table 9: Table 9. Effect of the ratio of urea to metal elements on catalyst performance

[0091] As shown in Table 9, urea and metal elements in a ratio of 3-6:1 can catalyze Friedel-Crafts alkylation reactions.

[0092] Example 25 Effect of Bimetallic Ratio on Friedel-Crafts Reaction 1 mL of butanone alcohol, 3.85 g of phenol, and 0.1 g of CrZrP phosphate prepared in Example 14 or CeZrP phosphate catalyst prepared according to the method in Example 18 were sequentially added to a high-pressure reactor, and nitrogen gas was introduced. The reaction temperature was 170 °C, the reaction time was 10 h, the reaction pressure was 1 MPa, and the stirring speed was 600 r / min. After the reaction was stopped, the reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed by gas chromatography (GC9560). The GC detection results are shown in Table 10.

[0093] Table 10 Effect of bimetallic ratio on Friedel-Crafts alkylation reaction

[0094] As can be seen from the results in Table 10, the transition metal soluble salts with a molar ratio of 3-8:3-8 can all catalyze the Friedel-Crafts alkylation reaction.

[0095] Example 26

[0096] 1 mL of alcohol, 3.85 g of phenol, and 0.1 g of the Co-P phosphate catalyst prepared in Example 1 were sequentially added to a high-pressure reactor, and nitrogen gas was introduced. The reaction temperature was 170 °C, the reaction time was 10 h, the reaction pressure was 1 MPa, and the stirring speed was 600 r / min. After the reaction was stopped, the reactor was cooled to room temperature, the reaction solution was centrifuged, and analyzed by gas chromatography (GC9560). The GC detection results are shown in Table 11.

[0097] Table 11. Conversion rates of catalysts for different reaction substrates

[0098] As can be seen from the results in Table 11, the Co-P phosphate catalyst also exhibits specificity in its selection of alcohols. The results show that, except for methanol, the Co-P phosphate catalyst demonstrates good catalytic performance for a variety of alcohol substrates such as ethanol, tert-butanol, butanone, and isopropanol. It also achieves high conversion rates in the Friedel-Crafts alkylation reaction with phenol, which fully demonstrates that the catalyst of this invention has excellent catalytic performance in this type of reaction.

[0099] Example 27

[0100] To expand the application scenarios of phosphate catalysts and verify their catalytic performance in Friedel-Crafts acylation reactions, this experiment explored the catalytic effect of this catalyst on the acylation reaction of aromatic hydrocarbons with acyl chlorides. The specific experimental procedures were as follows: 4.6 mL of an aromatic compound, 1 mL of acyl chloride, and 0.1 g of the Co-P phosphate catalyst prepared in Example 1 were sequentially added to a high-pressure reactor, and nitrogen gas was introduced. The reaction temperature was 100℃, the reaction time was 10 h, the reaction pressure was 1 MPa, and the stirring speed was 600 r / min. 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 12.

[0101] Table 12 Conversion rates of catalysts for different reaction substrates

[0102] As shown in Table 12, when the Co-P phosphate catalyst is extended to the Friedel-Crafts acylation reaction of aromatic compounds with acyl chlorides, it exhibits highly efficient catalytic activity. This result overcomes the application limitations of this type of catalyst, expands the application scenarios of phosphate materials in electrophilic substitution reactions, and provides a novel and highly efficient catalytic scheme for Friedel-Crafts acylation reactions.

Claims

1. A method for preparing a metal phosphate catalyst, characterized in that, Dissolve a transition metal soluble salt in deionized water, add an aqueous phosphate solution, and stir for 10-50 min to produce a precipitate; add nitric acid solution dropwise to the precipitate system to dissolve the precipitate, stir for 5-30 min, and then add urea to obtain a mixed solution; The mixed solution was subjected to a hydrothermal reaction. After the reaction was completed, the solution was washed, filtered, and dried to obtain the metal phosphate catalyst.

2. The method for preparing a metal phosphate catalyst according to claim 1, characterized in that, The transition metal soluble salt comprises at least a chloride salt or oxyacid salt of a transition metal, and the transition metal is one or more of Co, Cr, Mn, Ti, Fe, Ho, Zr, and Ce.

3. The method for preparing a metal phosphate catalyst according to claim 1, characterized in that, The oxyacid salts include at least one of nitrates, sulfates, acetates, and propionates; the phosphates contain one or more of phosphate ions, hydrogen phosphate ions, and dihydrogen phosphate ions.

4. The method for preparing a metal phosphate catalyst according to claim 1, characterized in that, When the transition metal soluble salt is composed of two metal salts, and the molar ratio of the two metal salts is 3-8:3-8.

5. The method for preparing a metal phosphate catalyst according to claim 1, characterized in that, The molar ratio of soluble transition metal salts to phosphates is 1:0.5-7; the concentration of nitric acid solution is 5-20 mol / L, and the molar ratio of nitric acid solution to transition metal ions is 1-3:1; the molar ratio of urea to transition metal ions is 3-6:

1.

6. The method for preparing a metal phosphate catalyst according to claim 1, characterized in that, The hydrothermal reaction conditions are constant temperature reaction at 90-140℃ for 6-36 h, followed by washing with water 3 times, and drying at 80-140℃ to constant weight.

7. A metal phosphate catalyst prepared by any one of the preparation methods in claims 1-6.

8. The application of the metal phosphate catalyst according to claim 7 in the Friedel-Crafts reaction.

9. The application according to claim 8, characterized in that, The application is for the preparation of alkylphenols, including the following steps: S1, 0.1-0.2 g of metal phosphate catalyst, phenol and alcohol are added to a batch reactor and mixed. The ratio of phenol to alcohol in the mixture is 1.56-5 g: 1 mL. The alcohol includes one or more of ethanol, isopropanol, tert-butanol and butanone. S2, nitrogen gas is introduced into the reactor to maintain a pressure of 1-2 MPa, and the mixture is heated at 150-190℃ and stirred at 200-800 rpm for 8-14 h to obtain alkylphenol.

10. The application according to claim 9, characterized in that, The application is a Friedel-Crafts acylation reaction of aromatic compounds with acyl chlorides, comprising the following steps: S1, 0.1-0.2 g of metal phosphate catalyst, aromatic compound and acyl chloride are added to a batch reactor, wherein the volume ratio of the aromatic hydrocarbon to alcohol mixture is 2-6:1; S2, nitrogen gas is introduced into the reactor to maintain a pressure of 1-2 MPa, and the mixture is heated at 70-140℃ and stirred at 200-800 rpm for 6-14 h to obtain aromatic ketones.

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