Mesoporous metal phosphate catalyst as well as preparation method and application thereof

Abstract

The invention discloses a mesoporous metal phosphate catalyst as well as a preparation method and application thereof, and belongs to the technical field of p-hydroxybenzonitrile synthesis catalysis. According to the preparation method disclosed by the invention, the mesoporous metal phosphate catalyst with high crystallinity, large specific surface area and good thermal stability can be prepared by taking the metal inorganic salt as a metal source, phosphoric acid as a phosphorus source and the block polymer as a soft template agent; the catalyst is applied to continuous synthesis of p-hydroxybenzonitrile in a fixed bed reactor by taking methyl p-hydroxybenzoate and ammonia gas as raw materials, has excellent catalytic performance, and effectively solves the problem of environmental pollution caused by the existing p-hydroxybenzonitrile synthesis process.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesis catalysis of p-hydroxybenzonitrile, and particularly relates to a mesoporous metal phosphate catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] As an important fine chemical and organic synthesis intermediate, p-hydroxybenzonitrile can be used to produce pesticides such as "bromoxynil", "niclosamide", and "bromofenoxim", and can also be used to synthesize pharmaceutical products such as febuxostat and itopride. At the same time, it can be used as a polymerization monomer to synthesize liquid crystal materials. In addition, p-hydroxybenzonitrile can also be used as a corrosion inhibitor to slow down the corrosion rate of acids on metals.

[0003] Currently, the main production process of p-hydroxybenzonitrile in industry is to use p-hydroxybenzoic acid and urea as raw materials, and perform high-temperature melting dehydration in a reaction kettle to obtain the target product. During the reaction process, phosphorus pentachloride, phosphorus oxychloride, phosphorus pentoxide, phosgene, etc. are used as dehydrating agents. A large amount of hydrogen chloride (HCl) gas is released during the reaction of phosphorus pentachloride (PCl5) and phosphorus oxychloride (POCl3), and phosgene (COCl2) itself is a highly toxic gas. These gases cause serious pollution to the atmospheric environment and pose a great threat to the health of operators; at the same time, the phosphorus-containing wastewater generated during the reaction contains a large amount of phosphates and chlorides, which is difficult to treat. If it is directly discharged without proper treatment, it will lead to eutrophication of water bodies and affect the aquatic ecosystem; the phosphorus-containing waste residue generated after the reaction is difficult to treat and usually requires special chemical treatment or landfill, increasing the cost and environmental burden of waste residue treatment; this method causes relatively large environmental pollution due to the generation of a large amount of toxic and harmful gases, phosphorus-containing wastewater, waste residue, etc., and the post-treatment cost after the reaction is relatively high.

[0004] In recent years, relevant departments have paid more and more attention to environmental problems and the corresponding punishment intensity has become greater, and a clean way to produce fine chemicals is needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a mesoporous metal phosphate catalyst, a preparation method thereof, and an application thereof, so as to solve the technical problem of relatively large environmental pollution in the existing preparation process of p-hydroxybenzonitrile.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions to be realized:

[0007] The present invention discloses a preparation method of a mesoporous metal phosphate catalyst, comprising the following steps:

[0008] After mixing a metal inorganic salt, phosphoric acid, a soft template agent, and water, a mixture is obtained; subsequently, the mixture is subjected to a hydrothermal crystallization reaction to obtain a reaction product; after post-treating the reaction product, a mesoporous metal phosphate catalyst is obtained.

[0009] Among them, the soft template agent is a block polymer.

[0010] Furthermore, the metal species in the metal inorganic salt is one or more of Fe, Ti, Ce, Zr, Al, and Mg.

[0011] Furthermore, the molar concentration of the phosphoric acid is 0.1 - 1 mol / L.

[0012] Furthermore, the dosage ratio of the metal inorganic salt, phosphoric acid, soft template agent, and water is (0.1 - 10) mol : 1 mol : (1 - 10) g : (50 - 100) g.

[0013] Furthermore, the block polymer is block polymer P123; the pH value of the mixture is adjusted to 4 - 7 with ammonia water.

[0014] Furthermore, the temperature of the hydrothermal crystallization reaction is 100 - 150 °C, and the crystallization time is 1 - 7 d.

[0015] Furthermore, the post-treatment includes filtration, washing, drying, and calcination treatments carried out in sequence.

[0016] The calcination treatment is carried out in an air atmosphere, and the temperature of the calcination treatment is 400 - 700 °C, and the time is 4 - 8 h.

[0017] The present invention also discloses a mesoporous metal phosphate catalyst prepared by the above preparation method.

[0018] The present invention also discloses the application of the above mesoporous metal phosphate catalyst in the preparation of hydroxybenzonitrile, including the following steps:

[0019] Using methyl p-hydroxybenzoate and ammonia as raw materials, catalyzed by the mesoporous metal phosphate catalyst of claim 8, and reacting in a fixed-bed reactor to continuously synthesize p-hydroxybenzonitrile.

[0020] Furthermore, the ammonia gas flow rate is 0.1 - 5 L / min, and the methyl p-hydroxybenzoate is in a molten state; the space velocity of the molten methyl p-hydroxybenzoate is 0.1 - 5 h -1 ;

[0021] The reaction temperature is 300 - 500 °C, and the reaction pressure is 0.1 - 0.5 MPa.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention discloses a preparation method of a mesoporous metal phosphate catalyst. Using metal inorganic salts as the metal source, phosphoric acid as the phosphorus source, and block polymers as the soft template agent, an ordered mesoporous structure can be formed through self-assembly, and the pore size and distribution can be precisely controlled by adjusting the molecular weight and proportion of the block polymers. This ordered mesoporous structure is beneficial to the diffusion of reactants and products, improving the mass transfer efficiency of the catalyst. Using metal inorganic salts and phosphoric acid as precursors, metal and phosphorus elements can be uniformly distributed under the templating action of the block polymers to form a uniform metal phosphate structure. This uniform distribution helps to improve the stability and catalytic efficiency of the catalyst. The preparation process of this method is simple, and the obtained catalyst has high crystallinity, a large specific surface area, and good thermal stability, which can improve the mass transfer and heat transfer during the reaction process. Compared with existing catalysts, when this catalyst is applied to the continuous synthesis of p-hydroxybenzonitrile from methyl p-hydroxybenzoate and ammonia in a fixed-bed reactor, it has excellent catalytic performance and effectively solves the environmental pollution problem in the current p-hydroxybenzonitrile synthesis process.

[0024] The present invention also discloses the application of the mesoporous metal phosphate catalyst prepared by the above method in the continuous synthesis of p-hydroxybenzonitrile in a fixed-bed reactor. This catalyst not only avoids the use of dehydrating agents, reduces cumbersome post-treatment steps, simplifies the process flow, greatly reduces environmental pollution, but also improves production efficiency and reduces production costs. It is a green production process with great prospects. According to relevant experimental results, when using this catalyst for the continuous synthesis of p-hydroxybenzonitrile, the product yield can reach more than 85%, showing significant application prospects. Detailed Embodiments

[0025] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0026] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not limit the scope of the present invention in any way, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0027] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values (including integers and fractions) within the range.

[0028] In this text, unless otherwise specified, the terms "comprise", "include", "contain", "have" or similar terms cover the meanings of "consist of" and "consist essentially of". For example, "A comprises a" covers the meanings of "A comprises a and others" and "A consists only of a".

[0029] In this text, for the sake of brevity of description, not all possible combinations of all technical features in each embodiment or example are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered as falling within the scope described in this specification.

[0030] The present invention provides a method for preparing a mesoporous metal phosphate catalyst, comprising the following steps:

[0031] Using metal inorganic salts as the metal source, orthophosphoric acid as the phosphorus source, and block copolymer P123 as the soft template agent, a mesoporous metal phosphate catalyst is synthesized by hydrothermal method (hydrothermal crystallization reaction).

[0032] Preferably, the type of metal in the metal inorganic salts is one of Fe, Ti, Ce, Zr, Al, Mg, etc.

[0033] Preferably, the molar concentration of orthophosphoric acid is 0.1 - 1 mol / L; the molar ratio of metal inorganic salt to orthophosphoric acid is 0.1 - 10:1.

[0034] Preferably, the mass of block copolymer P123 is 1 - 10 g, the molecular weight of P123 is 3000 - 9000, the pH of the system is adjusted to 4 - 7 with ammonia water, the temperature of the hydrothermal crystallization reaction is 100 - 150 °C, and the time of the hydrothermal crystallization reaction is 1 - 7 d.

[0035] Preferably, after the hydrothermal crystallization reaction, the obtained reaction product needs to be post-treated, including filtration, washing, drying and calcination treatments carried out in sequence;

[0036] The calcination treatment is carried out in an air atmosphere, the temperature of the calcination treatment is 400 - 700 °C, and the time is 4 - 8 h.

[0037] The present invention also discloses a mesoporous metal phosphate catalyst prepared by the above preparation method.

[0038] The present invention also discloses the industrial application of the above mesoporous metal phosphate catalyst in the metal phosphate catalyst for synthesizing p-hydroxybenzonitrile in a fixed-bed reactor, the reaction temperature is 300 - 500 °C, the reaction pressure is 0.1 - 0.5 MPa, the ammonia gas flow rate is 0.1 - 5 L / min, and the space velocity of molten methyl p-hydroxybenzoate is 0.1 - 5 h -1 , and the amount of substance of methyl p-hydroxybenzoate and ammonia.

[0039] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0040] The following embodiments use conventional instruments and equipment in the art. The experimental methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are the conventional specifications in the art. In the specification of the present invention and the following embodiments, unless otherwise specified, "%" represents weight percentage, "parts" represents weight parts, and the ratio represents weight ratio.

[0041] Example 1

[0042] A method for preparing a mesoporous metal phosphate catalyst, comprising the following steps:

[0043] Add 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 5000) to 80 g of deionized water. After stirring for 30 min, add 18.2 g of zirconium oxychloride to obtain a mixture. Subsequently, dropwise add 30% ammonia water to adjust the pH value of the mixture to 6, and continue stirring at room temperature for 3 h. Then transfer the mixture to a hydrothermal reaction kettle lined with polytetrafluoroethylene and carry out hydrothermal crystallization reaction at 100 °C for 3 d to obtain a reaction product. Filter and wash the reaction product, dry it at 80 °C for 12 h, and finally place the precipitate in a muffle furnace and calcine it at 500 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-ZrPO-1.

[0044] Example 2

[0045] A method for preparing a mesoporous metal phosphate catalyst, comprising the following steps:

[0046] Add 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 5000) to 80 g of deionized water. After stirring for 30 min, add 9.1 g of zirconium oxychloride to obtain a mixture. Subsequently, dropwise add 30% ammonia water to adjust the pH value of the mixture to 6, and continue stirring at room temperature for 3 h. Then transfer the mixture to a hydrothermal reaction kettle lined with polytetrafluoroethylene and carry out hydrothermal crystallization reaction at 100 °C for 3 d to obtain a reaction product. Filter and wash the reaction product, dry it at 80 °C for 12 h, and finally place the precipitate in a muffle furnace and calcine it at 500 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-ZrPO-2.

[0047] Example 3

[0048] A preparation method of a mesoporous metal phosphate catalyst, comprising the following steps:

[0049] Add 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 3000) to 80 g of deionized water. After stirring for 30 min, add 18.2 g of zirconium oxychloride to obtain a mixture. Subsequently, dropwise add 30% ammonia water to adjust the pH value of the mixture to 6, and continue stirring at room temperature for 3 h. Then transfer the mixture to a hydrothermal reaction kettle lined with polytetrafluoroethylene and carry out hydrothermal crystallization reaction at 120 °C for 3 d to obtain a reaction product. Filter and wash the reaction product, dry it at 80 °C for 12 h, and finally place the precipitate in a muffle furnace and calcine it at 500 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-ZrPO-3.

[0050] Example 4

[0051] A preparation method of a mesoporous metal phosphate catalyst, comprising the following steps:

[0052] Add 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 3000) to 80 g of deionized water. After stirring for 30 min, add 18.2 g of zirconium oxychloride to obtain a mixture. Subsequently, dropwise add 30% ammonia water to adjust the pH value of the mixture to 5, and continue stirring at room temperature for 3 h. Then transfer the mixture to a hydrothermal reaction kettle lined with polytetrafluoroethylene and carry out hydrothermal crystallization reaction at 120 °C for 3 d to obtain a reaction product. Filter and wash the reaction product, dry it at 80 °C for 12 h, and finally place the precipitate in a muffle furnace and calcine it at 600 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-ZrPO-4.

[0053] Example 5

[0054] A preparation method of a mesoporous metal phosphate catalyst, comprising the following steps:

[0055] Add 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 3000) to 80 g of deionized water. After stirring for 30 min, add 9.9 g of Fe(NO)3 to obtain a mixture. Subsequently, dropwise add 30% ammonia water to adjust the pH value of the mixture to 6, and continue stirring at room temperature for 3 h. Then transfer the mixture to a hydrothermal reaction kettle lined with polytetrafluoroethylene and carry out hydrothermal crystallization reaction at 100 °C for 3 d to obtain a reaction product. Filter and wash the reaction product, dry it at 80 °C for 12 h, and finally place the precipitate in a muffle furnace and calcine it at 500 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-FePO.

[0056] Example 6

[0057] A preparation method of a mesoporous metal phosphate catalyst, comprising the following steps:

[0058] 5 g of orthophosphoric acid and 5 g of P123 (molecular weight 3000) were added to 80 g of deionized water. After stirring for 30 min, 7.6 g of Mg(NO₃)₂ was added to obtain a mixture. Subsequently, 30% ammonia water was added dropwise to adjust the pH value of the mixture to 6, and stirring was continued at room temperature for 3 h. Then the mixture was transferred to a hydrothermal reaction kettle lined with polytetrafluoroethylene and hydrothermally crystallized at 100 °C for 3 d to obtain a reaction product. The reaction product was filtered, washed, dried at 80 °C for 12 h, and finally the precipitate was calcined in a muffle furnace at 500 °C for 6 h to obtain a mesoporous metal phosphate catalyst, denoted as meso-MgPO₄.

[0059] Application Example 1

[0060] The mesoporous metal phosphate catalyst prepared in Example 1 was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The temperature of the reactor was raised to 500 °C, and N₂ was introduced for pretreatment for 3 h. Then the nitrogen valve was closed, the ammonia valve was opened, and the ammonia flow rate was set at 1.5 L / min. The molten methyl 4-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then fed into the reactor, and the liquid mass space velocity was 0.5 h⁻¹. -1 The product entered a cold trap for cooling and collection. After the reaction was completed, the product was collected and analyzed by gas chromatography. The results showed that the conversion rate of methyl 4-hydroxybenzoate was 94.7%, the selectivity for 4-hydroxybenzonitrile was 84.3%, and the product yield was 79.8%.

[0061] Application Example 2

[0062] The mesoporous metal phosphate catalyst prepared in Example 1 was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The temperature of the reactor was raised to 400 °C, and N₂ was introduced for pretreatment for 3 h. Then the nitrogen valve was closed, the ammonia valve was opened, and the ammonia flow rate was set at 2 L / min. The molten methyl 4-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then fed into the reactor, and the liquid mass space velocity was 0.5 h⁻¹. -1 The product entered a cold trap for cooling and collection. After the reaction was completed, the product was collected and analyzed by gas chromatography. The results showed that the conversion rate of methyl 4-hydroxybenzoate was 89.3%, the selectivity for 4-hydroxybenzonitrile was 96.8%, and the product yield was 86.4%.

[0063] Application Example 3

[0064] The mesoporous metal phosphate catalyst prepared in Example 1 was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The temperature of the reactor was raised to 400 °C, and N₂ was introduced for pretreatment for 3 h. Then the nitrogen valve was closed, the ammonia valve was opened, and the ammonia flow rate was set at 2 L / min. The molten methyl 4-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then fed into the reactor, and the liquid mass space velocity was 1 h⁻¹.-1 The product enters the cold trap for cooling and collection. After the reaction ends, the product is collected and analyzed by gas chromatography. The results show that the conversion rate of methyl p-hydroxybenzoate is 88.4%, the selectivity for p-hydroxybenzonitrile is 95.2%, and the product yield is 84.2%.

[0065] Application Example 3

[0066] The mesoporous metal phosphate catalyst prepared in Example 2 is tableted and granulated, and then loaded into a fixed-bed reactor together with the packing. The reactor temperature is raised to 400 °C and pretreated with N2 for 3 h. Then the nitrogen valve is closed, the ammonia valve is opened, and the ammonia flow rate is set at 1.5 L / min. The molten methyl p-hydroxybenzoate is mixed with ammonia by a diaphragm pump and then fed into the reactor. The liquid mass space velocity is 0.5 h -1 The product enters the cold trap for cooling and collection. After the reaction ends, the product is collected and analyzed by gas chromatography. The results show that the conversion rate of methyl p-hydroxybenzoate is 87.7%, the selectivity for p-hydroxybenzonitrile is 94.1%, and the product yield is 82.5%.

[0067] Application Example 4

[0068] The mesoporous metal phosphate catalyst prepared in Example 3 is tableted and granulated. The reactor temperature is raised to 400 °C and pretreated with N2 for 3 h. Then the nitrogen valve is closed, the ammonia valve is opened, and the ammonia flow rate is set at 1.5 L / min. The molten methyl p-hydroxybenzoate is mixed with ammonia by a diaphragm pump and then fed into the reactor. The liquid mass space velocity is 0.5 h -1 The product enters the cold trap for cooling and collection. After the reaction ends, the product is collected and analyzed by gas chromatography. The results show that the conversion rate of methyl p-hydroxybenzoate is 94.7%, the selectivity for p-hydroxybenzonitrile is 95.8%, and the product yield is 90.7%.

[0069] Application Example 5

[0070] The mesoporous metal phosphate catalyst prepared in Example 4 is tableted and granulated, and then loaded into a fixed-bed reactor together with the packing. The reactor temperature is raised to 400 °C and pretreated with N2 for 3 h. Then the nitrogen valve is closed, the ammonia valve is opened, and the ammonia flow rate is set at 1.5 L / min. The molten methyl p-hydroxybenzoate is mixed with ammonia by a diaphragm pump and then fed into the reactor. The liquid mass space velocity is 0.5 h -1 The product enters the cold trap for cooling and collection. After the reaction ends, the product is collected and analyzed by gas chromatography. The results show that the conversion rate of methyl p-hydroxybenzoate is 88.3%, the selectivity for p-hydroxybenzonitrile is 87.4%, and the product yield is 77.2%.

[0071] Application Example 6

[0072] The mesoporous metal phosphate catalyst prepared in Example 5 was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The reactor temperature was raised to 400 °C and pretreated with N2 for 3 h. Then the nitrogen valve was closed, the ammonia valve was opened, the ammonia flow rate was set at 1.5 L / min, and the molten methyl p-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then pumped into the reactor. The liquid mass space velocity was 0.5 h -1 , and the products were cooled and collected in a cold trap; after the reaction, the products were collected and analyzed by gas chromatography. The results showed that the conversion rate of methyl p-hydroxybenzoate was 86.3%, the selectivity to p-hydroxybenzonitrile was 82.4%, and the product yield was 71.1%.

[0073] Application Example 7

[0074] The mesoporous metal phosphate catalyst prepared in Example 6 was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The reactor temperature was raised to 400 °C and pretreated with N2 for 3 h; then the nitrogen valve was closed, the ammonia valve was opened, the ammonia flow rate was set at 1.5 L / min, and the molten methyl p-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then pumped into the reactor. The liquid mass space velocity was 0.5 h -1 , and the products were cooled and collected in a cold trap; after the reaction, the products were collected and analyzed by gas chromatography. The results showed that the conversion rate of methyl p-hydroxybenzoate was 74.3%, the selectivity to p-hydroxybenzonitrile was 86.8%, and the product yield was 64.4%.

[0075] Comparative Example 1

[0076] Compared with Example 1, in this comparative example, a phosphate catalyst was synthesized without adding the template P123 for the reaction;

[0077] First, 5 g of orthophosphoric acid was added to 80 g of deionized water, stirred for 30 min, then 18.2 g of zirconium oxychloride was added, and 30% ammonia water was added dropwise to adjust the system to 6, and stirring was continued at room temperature for 3 h. Then the whole mixture was transferred to a hydrothermal reaction kettle lined with polytetrafluoroethylene and crystallized at 100 °C for 3 days. The obtained precipitate was filtered, washed, dried at 80 °C for 12 h, and finally the precipitate was placed in a muffle furnace and calcined at 500 °C for 6 h. The obtained catalyst was denoted as ZrPO.

[0078] The catalyst prepared in this comparative example was tableted and granulated, and then loaded into a fixed-bed reactor together with a filler. The reactor temperature was raised to 400 °C and pretreated with N2 for 3 h. Then the nitrogen valve was closed, the ammonia valve was opened, the ammonia flow rate was set at 1.5 L / min, and the molten methyl p-hydroxybenzoate was mixed with ammonia by a diaphragm pump and then pumped into the reactor. The liquid mass space velocity was 0.5 h -1, the product enters the cold trap for cooling and collection. After the reaction is completed, the product is collected and analyzed by gas chromatography. The results show that the conversion rate of methyl 4-hydroxybenzoate is 67.4%, the selectivity of 4-hydroxybenzonitrile is 87.5%, and the product yield is 58.8%.

[0079] As can be seen from the above examples and comparative examples, the catalyst yield in the examples is higher. This is because the mesoporous phosphate catalyst synthesized with the block polymer as the template agent has a higher specific surface area, exposing more catalytic active sites. At the same time, the ordered mesoporous structure improves the mass transfer rate of the reactants, thereby increasing the conversion rate of the reactants and the selectivity of the products.

[0080] The above content is only to illustrate the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a mesoporous metal phosphate catalyst, characterized in that: The following steps are involved: A metal inorganic salt, phosphoric acid, a soft template and water are mixed to obtain a mixture; the mixture is then subjected to a hydrothermal crystallization reaction to obtain a reaction product; the reaction product is post-treated to obtain a mesoporous metal phosphate catalyst; Wherein, the soft template is a block polymer.

2. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The metal species in the metal inorganic salt is one or more of Fe, Ti, Ce, Zr, Al and Mg.

3. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The molar concentration of the phosphoric acid is 0.1 to 1 mol / L.

4. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The usage ratio of the metal inorganic salt, phosphoric acid, soft template agent and water is (0.1-10) mol: 1 mol: (1-10) g: (50-100) g.

5. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The block polymer is block polymer P123; and ammonia water is used to adjust the pH value of the mixture to 4-7.

6. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The temperature of the hydrothermal crystallization reaction is 100-150° C., and the crystallization time is 1-7 days.

7. The method for preparing a mesoporous metal phosphate catalyst according to claim 1, characterized in that: The post-treatment includes filtering, washing, drying and calcining in sequence; The calcination treatment is carried out in an air atmosphere at a temperature of 400 to 700° C. and a time of 4 to 8 hours.

8. A mesoporous metal phosphate catalyst, characterized in that: The preparation method is described in any one of claims 1 to 7.

9. Use of the mesoporous metal phosphate catalyst according to claim 8 in the preparation of hydroxybenzonitrile, characterized in that: The following steps are involved: Methyl p-hydroxybenzoate and ammonia are used as raw materials, the mesoporous metal phosphate catalyst of claim 8 is used for catalysis, and the reaction is carried out in a fixed bed reactor to continuously synthesize p-hydroxybenzonitrile.

10. Use of the mesoporous metal phosphate catalyst according to claim 9 in the preparation of hydroxybenzonitrile, characterized in that: The ammonia gas flow rate is 0.1 to 5 L / min, the methyl p-hydroxybenzoate is in a molten state, and the space velocity of the molten methyl p-hydroxybenzoate is 0.1 to 5 h -1 ; The reaction temperature is 300-500° C., and the reaction pressure is 0.1-0.5 MPa.