A method for preparing terephthalic acid by oxygen oxidation

Abstract

The present disclosure relates to a method for preparing terephthalic acid by oxygen oxidation, which comprises the following steps: contacting p-xylene with a catalyst for oxidation reaction in the presence of oxygen; the catalyst is a composite catalytic material, which comprises a framework heteroatom molecular sieve and a metal element M dispersed in the intracrystalline of the molecular sieve; the framework heteroatom molecular sieve is a molecular sieve in which at least part of the silicon in the full-silicon molecular sieve framework is replaced by a heteroatom element Q, and the heteroatom element Q is one or more selected from titanium, boron, zirconium, tin, aluminum, phosphorus and germanium. The method uses a metal-containing hierarchical porous molecular sieve catalytic material, the active component of which is highly dispersed and has good accessibility, high thermal stability and chemical stability, and when the p-xylene oxygen oxidation reaction is carried out, high conversion of p-xylene and selectivity of terephthalic acid can be obtained under relatively mild conditions.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of organic chemical industry, in particular, to a method for preparing terephthalic acid by oxygen oxidation. BACKGROUND

[0002] Terephthalic acid, also known as p-benzene dicarboxylic acid, is mainly prepared from p-xylene, and its application is relatively concentrated. More than 90% of terephthalic acid in the world is used to produce the most important polyester polyethylene terephthalate. Another important application of terephthalic acid is to produce plasticizers, which include two types: the first type is dioctyl terephthalate (DOTP), which is the product of esterification reaction of terephthalic acid and industrial octanol (2-ethylhexanol), and is a high-quality plasticizer with high flash point and high specific resistance, which is particularly suitable for the production of cable materials with high heat resistance and insulation requirements; the second type is polyester plasticizer, which is the product of esterification and polycondensation reaction of terephthalic acid and polyols (such as diethylene glycol, triethylene glycol, glycerol, propylene glycol, butanediol, etc.), and the relative molecular mass thereof is generally between 1000-4000 (as a plasticizer, the relative molecular mass of polyester is much smaller than that of polyester used in chemical fibers and plastic packaging).

[0003] The traditional process route for producing terephthalic acid includes p-xylene high-temperature liquid-phase oxidation method, phthalic anhydride transposition method, and toluene oxidation disproportionation method, etc. Among them, the phthalic anhydride transposition method has high raw material cost and complex technology, so it has been industrialized but not popularized; the toluene oxidation disproportionation method was stopped in 1975 due to high cost, but some companies in some countries are still researching and improving this method because the raw material toluene is much cheaper than p-xylene; the most economical and widely used method is the high-temperature liquid-phase oxidation method using p-xylene as raw material, which has high yield and short process. This process generally uses homogeneous catalysts such as cobalt acetate-manganese acetate, and the reaction temperature is high, and there is bromine (bromide as a catalyst promoter), which has strong corrosion effect. SUMMARY

[0004] The purpose of the present disclosure is to provide a method for preparing terephthalic acid by oxygen oxidation, which uses a composite catalytic material including a framework heteroatom molecular sieve and a metal element dispersed in the intracrystalline of the molecular sieve as a catalyst for p-xylene oxygen oxidation reaction, and can obtain high conversion rate of p-xylene and selectivity of terephthalic acid under relatively mild conditions.

[0005] In order to achieve the above-mentioned purpose, the present disclosure provides a method for preparing terephthalic acid by oxygen oxidation, which comprises the following steps:

[0006] contacting p-xylene with a catalyst in the presence of oxygen to perform an oxidation reaction;

[0007] The catalyst is a composite catalytic material, which includes a framework heteroatom molecular sieve and a metal element M dispersed within the crystals of the molecular sieve; the framework heteroatom molecular sieve is a molecular sieve in which at least part of the silicon in the all-silicon molecular sieve framework is replaced by a heteroatom element Q, and the heteroatom element Q is selected from one or more of titanium, boron, zirconium, tin, aluminum, phosphorus and germanium.

[0008] Optionally, the conditions for the oxidation reaction include: a reaction temperature of 150-300℃, preferably 150-250℃; a time of 1-48h, preferably 2-24h; and an oxygen pressure of 1-3MPa, preferably 1.5-3MPa.

[0009] The weight ratio of the catalyst to the p-xylene is 1:(1-20), preferably 1:(2-10);

[0010] Optionally, the reactor for the oxidation reaction is at least one of a batch reactor, a fixed-bed reactor, a moving-bed reactor, a suspended-bed reactor, and a slurry-bed reactor.

[0011] Optionally, the composite catalytic material has the following 29Si NMR characteristics:

[0012] The composite catalytic material 29 In the Si NMR spectrum, the intensity at a chemical shift of -103 ppm is denoted as Q3, and the intensity at a chemical shift of -113 ppm is denoted as Q4.

[0013] Q0, as defined in equation (1), is any value between 0.03 and 0.1;

[0014] Q0 = Q3 / Q4 (Equation 1);

[0015] Preferably, Q0 is any value between 0.05 and 0.09.

[0016] Optionally, the framework heteroatom molecular sieve in the composite catalytic material is at least one of MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, MWW structure molecular sieve, two-dimensional hexagonal structure molecular sieve, MOR structure molecular sieve, and TUN structure molecular sieve; preferably, it is selected from one or more of MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, MCM structure molecular sieve, and SBA structure molecular sieve; more preferably, it is selected from one or more of MFI structure molecular sieve, MEL structure molecular sieve, and BEA structure molecular sieve.

[0017] The metallic element M is selected from one or more of manganese, iron, cobalt, nickel, palladium, platinum, copper, and gold.

[0018] Optionally, in the composite catalytic material, the molar ratio of the framework heteroatom element to the silicon element is (0.001-0.04):1, preferably (0.002-0.035):1; and the molar ratio of the metal M element to the silicon element is (0.001-0.2):1, preferably (0.003-0.14):1.

[0019] Optionally, the BET specific surface area of ​​the composite catalytic material is 400–800 m². 2 The total pore volume is 0.3–0.65 mL / g, the micropore volume is 0.1–0.19 mL / g, and the mesopore volume is 0.20–0.46 mL / g. The metal element M in the composite catalytic material exists in the form of metal nanoparticles, and the average particle size of the metal nanoparticles is 0.5–9 nm.

[0020] Optionally, the catalyst is prepared by a method comprising the following steps:

[0021] S1. Mix the template agent, silicon source, framework heteroatom precursor, water, metal M precursor, polyhydroxy auxiliary agent and silanizing agent to obtain a reaction mixture;

[0022] S2. The reaction mixture is subjected to hydrothermal crystallization and calcination treatment;

[0023] The silanizing agent contains at least one coordinating group that complexes with the metal element M; the polyhydroxy auxiliary is a compound containing at least two hydroxyl groups.

[0024] Optionally, in step S1, the molar ratio of the silicon source (based on SiO2): template agent: framework heteroatom precursor (based on heteroatom element Q): water: metal element M: polyhydroxy auxiliary agent: silanizing agent is 1:(0.005~1):(0.001~0.04):(10~80):(0.001~0.2):(0.5~5):(0.025~0.4);

[0025] The preferred ratio is 1: (0.005~1): (0.002~0.035): (10~80): (0.003~0.14): (0.5~5): (0.025~0.3).

[0026] Optionally, step S1 includes the following steps:

[0027] a. Mix the template agent, silicon source, framework heteroatom precursor and water to obtain a silicon hydrolysis solution;

[0028] b. Add the polyhydroxy additive to the aqueous solution of the metal M precursor to obtain a first mixture; mix the first mixture with a silicon hydrolysis solution to obtain a second mixture;

[0029] c. Add the silanizing agent to the second mixture, and mix to obtain the reaction mixture;

[0030] Preferably, the mixing conditions in step c include stirring at 20–80°C for 0.5–2 hours.

[0031] Optionally, the silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol; preferably, it is selected from at least one of silicone grease, solid silica gel, and fumed silica.

[0032] A further preferred option is a silicone grease, wherein the silicone grease has the general formula shown in formula (A):

[0033]

[0034] Where R a R b R c R d Each is independently selected from alkyl groups having 1 to 6 carbon atoms, wherein the alkyl group is branched or straight-chain alkyl; preferably, R a R b R c R d Each is independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms or branched alkyl groups having 3 to 4 carbon atoms; more preferably, the R a R b R c R d Each of the following is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl; more preferably, the silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silicone grease.

[0035] Optionally, the template agent is an organic base, preferably at least one selected from quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines; more preferably, the template agent is at least one selected from quaternary ammonium bases with the structure shown in formula (B) below:

[0036] R1, R2, R3 and R4 are each selected from alkyl groups having 1 to 4 carbon atoms, preferably straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 4 carbon atoms, more preferably R1, R2, R3 and R4 are each selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and tert-butyl;

[0037] More preferably, the molecular sieve in the composite catalytic material is an MFI type molecular sieve, and the template agent is tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide; or

[0038] The molecular sieve in the composite catalytic material is a MEL-type molecular sieve, and the template agent is tetrabutylammonium hydroxide or a mixture of tetrabutylammonium hydroxide and one or more selected from tetrabutylammonium chloride and tetrabutylammonium bromide; or

[0039] The molecular sieve in the composite catalytic material is a Beta-type molecular sieve, and the template agent is tetraethylammonium hydroxide or a mixture of tetraethylammonium hydroxide and one or more selected from tetraethylammonium chloride and tetraethylammonium bromide.

[0040] Optionally, in step a, the silicon source is an organosilicon grease, and after mixing the template agent, organosilicon grease, framework heteroatom precursor and water, a hydrolysis and alcohol removal treatment is further included to obtain the hydrolysate solution;

[0041] Optionally, the conditions for the hydrolysis and alcohol removal treatment include: stirring and hydrolyzing at 0–95°C for 2–10 hours; preferably, stirring and hydrolyzing at 50–95°C for 2–8 hours.

[0042] Optionally, in step S1, the skeletal heteroatom precursor includes at least one of an organic skeletal heteroatom precursor and an inorganic skeletal heteroatom precursor; the inorganic skeletal heteroatom precursor is at least one selected from chlorides, nitrates, and sulfates containing heteroatom element Q; the inorganic skeletal heteroatom precursor is an organic ester containing heteroatom element Q, selected from at least one of the structures shown in the following formula (C):

[0043]

[0044] R5, R6, R7 and R8 are each selected from alkyl groups having 1 to 6 carbon atoms, preferably straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms, and more preferably R5, R6, R7 and R8 are each selected from straight-chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms.

[0045] Optionally, R5, R6, R7 and R8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl; preferably, each is independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.

[0046] Preferably, when the framework heteroatom is titanium, the framework heteroatom precursor is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate; when the framework heteroatom is boron, the framework heteroatom precursor is selected from one or more of boric acid and borate; when the framework heteroatom is tin, the framework heteroatom precursor is selected from one or more of tin halide, stannous halide, stannous sulfate, stannous sulfate, stannate, stannous nitrate, tin oxide, and stannous oxide; when the framework heteroatom is aluminum, the framework heteroatom precursor is selected from one or more of sodium aluminate, aluminum sulfate, boehmite, metallic aluminum, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide; when the framework heteroatom is phosphorus, the framework heteroatom precursor is selected from one or more of orthophosphoric acid, triethylphosphoric acid, and metaphosphate; when the framework heteroatom is germanium, the framework heteroatom precursor is selected from one or more of germanium oxide, germanium alkoxide, germanium chloride, and sodium germanate.

[0047] Optionally, in step S1, the metal M precursor is one or more of inorganic metal compounds and organometallic compounds; the inorganic metal compound is a water-soluble inorganic salt of metal element M; the water-soluble inorganic salt of metal element M is selected from one or more of chlorides, hydrated chlorides, sulfates, hydrated sulfates, and nitrates of metal element M; the organometallic compound is an organic ligand compound of metal element M; preferably, the metal M precursor is a water-soluble inorganic salt of metal element M.

[0048] Optionally, the metallic element M is selected from one or more of manganese, iron, cobalt, nickel, palladium, platinum, copper and gold;

[0049] Preferably, the metal M precursor is an aqueous solution of the metal M precursor, wherein the molar ratio of metal element M to water in the aqueous solution of the metal M precursor is 1:(50-500).

[0050] Optionally, in step S1, the polyhydroxy auxiliary agent is selected from one or more of polyols and sugars;

[0051] Preferably, the polyol comprises one or more of ethylene glycol, glycerol, pentaerythritol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and polyether polyols; wherein the polyether polyol comprises one or more of propylene glycol polyether, trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol; the weight-average molecular weight of the propylene glycol polyether is 800-2000, and the weight-average molecular weight of each of the trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol is independently 400-4000;

[0052] The carbohydrates include one or more of glucose, sucrose, fructose, starch, and cellulose.

[0053] Optionally, in step S1, the silanizing agent has the general formula R9Si(R 10 (R) 11 )R 12 Among them, R9 and R 10 R 11 R 12 Each can be independently a halogen, alkyl, alkoxy, aromatic, mercapto, or amino group, and R9, R 10 R 11 R 12 At least one of them is an alkyl, alkoxy, aromatic, mercapto, or amino group; the number of carbon atoms of the alkyl, alkoxy, mercapto, and amino groups is independently selected from any integer from 1 to 18, and the number of carbon atoms of the aromatic group is any integer selected from 6 to 18;

[0054] Preferably, the silanizing agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, 1,7-dichlorooctylmethyltetrasiloxane, hexadecyltrimethoxysilane, octyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane; more preferably, at least one of N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0055] Optionally, in step S2, the conditions for the hydrothermal crystallization treatment include: being carried out under autogenous pressure, with a hydrothermal crystallization time of 0.5 to 10 days and a hydrothermal crystallization temperature of 110 to 200°C; preferably, the hydrothermal crystallization time is 0.5 to 5 days and the hydrothermal crystallization temperature is 150 to 200°C.

[0056] Optionally, the calcination conditions include: a calcination temperature of 400–900°C and a calcination time of 1–16 hours; preferably, the calcination temperature is 400–800°C and the calcination time is 2–8 hours.

[0057] Through the above technical solution, this disclosure provides a method for preparing terephthalic acid by oxygen oxidation. This method uses oxygen as an oxidant to carry out a heterogeneous oxidation reaction and uses a composite catalytic material including a molecular sieve with a framework of heteroatoms and metal elements dispersed within the crystals of the molecular sieve as a catalyst for the oxygen oxidation reaction of p-xylene. The molecular sieve of this catalyst has a large specific surface area, pore volume and reaction activity, and the metal nanoparticles have a high degree of dispersion in the molecular sieve. The heteroatoms Q in the molecular sieve framework and the metal elements M outside the framework can achieve a synergistic catalytic effect, so that high conversion rate of p-xylene and high selectivity of terephthalic acid can be obtained under mild reaction conditions.

[0058] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0059] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0060] Figure 1 The cobalt-containing hierarchical porous MFI structure molecular sieve prepared in Example 1 29 Si NMR spectrum.

[0061] Figure 2 The UV-Vis image shows the framework heteroatom molecular sieve of the cobalt-containing hierarchical porous MFI structure molecular sieve prepared in Example 1.

[0062] Figure 3 The image shows the XRD pattern of the cobalt-containing hierarchical porous MFI molecular sieve prepared in Example 1.

[0063] Figure 4 The image shows a SEM image of the cobalt-containing hierarchical porous MFI molecular sieve prepared in Example 1. Detailed Implementation

[0064] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0065] This disclosure provides a method for preparing terephthalic acid by oxygen oxidation, the method comprising the following steps:

[0066] In the presence of oxygen, p-xylene is brought into contact with a catalyst to undergo an oxidation reaction;

[0067] The catalyst is a composite catalytic material, which includes a framework heteroatom molecular sieve and a metal element M dispersed within the crystals of the molecular sieve; the framework heteroatom molecular sieve is a molecular sieve in which at least part of the silicon in the all-silicon molecular sieve framework is replaced by a heteroatom element Q, and the heteroatom element Q is selected from one or more of titanium, boron, zirconium, tin, aluminum, phosphorus and germanium.

[0068] The inventors of this disclosure unexpectedly discovered that using a composite catalytic material of metal nanoparticles and molecular sieves as a catalyst to carry out the oxygen oxidation reaction of p-xylene can effectively improve the oxidation reaction rate and shorten the reaction time, achieving high conversion rate of p-xylene and high selectivity of terephthalic acid under relatively mild conditions.

[0069] Through extensive experimentation, the inventors of this disclosure have surprisingly discovered that by introducing heteroatom precursors, metal M precursors, polyhydroxy additives, and silanizing reagents (containing at least one coordinating group complexed with metal element M) into the reaction raw materials for the crystallization synthesis of molecular sieves, followed by hydrothermal crystallization and calcination, heteroatoms can be introduced into the molecular sieve framework. The resulting composite catalytic material, a heteroatom molecular sieve framework, possesses a hierarchical porous structure (micropores and mesopores) and a large specific surface area and pore volume. The metal oxide nanoparticles exhibit high uniformity in size and are evenly dispersed within the channels of the heteroatom molecular sieve framework. A certain amount of metal M nanoparticles also exist on the surface of the channels. Furthermore, the heteroatom metal sites on the molecular sieve framework and the metal sites (nanoparticles) of metal element M within the channels can achieve a synergistic catalytic effect, further enhancing the catalytic activity in the xylene oxidation reaction.

[0070] In one embodiment, the conditions for the oxidation reaction include: a reaction temperature of 150-300°C, preferably 150-250°C; a reaction time of 1-48 h, preferably 2-24 h; and an oxygen pressure of 1-3 MPa, preferably 1.5-3 MPa.

[0071] The weight ratio of the catalyst to the p-xylene is 1:(1-20), preferably 1:(2-10);

[0072] Optionally, the reactor for the oxidation reaction is at least one of a batch reactor, a fixed-bed reactor, a moving-bed reactor, a suspended-bed reactor, and a slurry-bed reactor.

[0073] Further research by the inventors revealed that this composite catalytic material 29 In the Si NMR spectrum, the ratio of the peak intensity at a chemical shift of -103 ppm (representing terminal silanols) to that at a chemical shift of -113 ppm (representing tetracoordinate silicon) is related to the catalytic activity of the composite catalyst in the co-oxidation reaction of aldehydes / olefins. The composite catalyst possesses the following characteristics:29 Si NMR characteristics: the composite catalytic material 29 The peak intensity of the highest peak at a chemical shift of -103 ppm in the Si NMR spectrum is denoted as Q3, and the peak intensity of the highest peak at a chemical shift of -113 ppm is denoted as Q4; when Q0, as defined in the following formula (1), is any value between 0.03 and 0.1, the composite catalytic material can obtain high catalytic activity.

[0074] Q0 = Q3 / Q4 Equation (1).

[0075] This disclosure provides a composite catalytic material of metal oxide nanoparticles and molecular sieves. The molecular sieve in this composite catalytic material has a hierarchical porous structure and a large specific surface area, pore volume, and high reactivity with macromolecular substrates. Furthermore, the metal oxide nanoparticles are uniformly sized and dispersed within the mesoporous channels of the hierarchical heteroatom framework molecular sieve. Significant interactions exist between the metal elements of the metal oxide particles and the heteroatoms within the framework. Introducing heteroatoms into the molecular sieve framework allows the two metal sites in the composite catalytic material to exhibit synergistic catalytic activity. Q0, any value between 0.03 and 0.1, demonstrates high catalytic activity.

[0076] This disclosure 29 In the Si NMR spectrum, the peak at a chemical shift of -103 ppm represents terminal silanol groups, whose chemical structure is shown in formula (I); the peak at a chemical shift of -113 ppm represents tetra-matched silicon, whose chemical structure is shown in formula (II). In this disclosure, Q0 is used to represent the proportion of terminal silanol groups in the total silicon species.

[0077]

[0078] In a preferred embodiment, Q0 is any value between 0.05 and 0.09. When Q0 of the composite catalytic material is within this range, the composite catalytic material exhibits higher catalytic activity, higher p-xylene conversion, and higher terephthalic acid selectivity.

[0079] In one embodiment, the framework heteroatom molecular sieve in the composite catalytic material is one or more of the following: MFI structure molecular sieve (e.g., S-1), MEL structure molecular sieve (e.g., S-2), BEA structure molecular sieve (e.g., Beta), MWW structure molecular sieve (e.g., MCM-22), two-dimensional hexagonal structure molecular sieve (e.g., MCM-41, SBA-15), MOR structure molecular sieve (e.g., MOR), TUN structure molecular sieve (e.g., TUN), and other structured silicon molecular sieves (e.g., ZSM-48, MCM-48); preferably selected from one or more of MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, MCM structure molecular sieve, and SBA structure molecular sieve; more preferably selected from one or more of MFI structure molecular sieve, MEL structure molecular sieve, and BEA structure molecular sieve, such as the silicon molecular sieve being one of S-1, S-2, and Beta; even more preferably selected from MFI structure molecular sieve, such as S-1.

[0080] In one embodiment, the metallic element M is selected from one or more of manganese, iron, cobalt, nickel, palladium, platinum, copper, and gold.

[0081] In one embodiment, the molar ratio of the framework heteroatom element to silicon element in the composite catalytic material is (0.001-0.04):1, preferably (0.002-0.035):1;

[0082] The molar ratio of metal M to silicon is (0.001-0.2):1, preferably (0.003-0.14):1.

[0083] In one embodiment, the composite catalytic material has a BET specific surface area of ​​400–800 m². 2 The composite catalytic material has a total pore volume of 0.3–0.65 mL / g, a micropore volume of 0.1–0.19 mL / g, and a mesopore volume of 0.20–0.46 mL / g. The metal element M in the composite catalytic material exists in the form of metal nanoparticles with an average particle size of 0.5–9 nm. The composite catalytic material of this disclosure has a hierarchical porous structure, which is beneficial for catalyzing reaction substrates of different sizes.

[0084] In one embodiment, the catalyst is prepared by a method comprising the following steps:

[0085] S1. Mix the template agent, silicon source, framework heteroatom precursor, water, metal M precursor, polyhydroxy auxiliary agent and silanizing agent to obtain a reaction mixture;

[0086] S2. The reaction mixture is subjected to hydrothermal crystallization and calcination treatment;

[0087] The silanizing agent contains at least one coordinating group that complexes with the metal element M; the polyhydroxy auxiliary is a compound containing at least two hydroxyl groups.

[0088] This disclosure introduces heteroatom precursors into the reaction mixture for molecular sieve synthesis. During crystallization, the heteroatoms primarily enter the molecular sieve framework. The disclosure also introduces a metal element precursor, a polyhydroxy auxiliary agent, and a silanizing agent into the reaction mixture. The polyhydroxy auxiliary agent can complex with metal M ions to fix and disperse the metal element; and the silanizing agent's coordinating groups complex with the metal to fix and disperse the metal element, while the alkyl chain's supporting layer effect expands the pores. This results in the final preparation of a framework heteroatom molecular sieve with a hierarchical porous structure, where metal M oxide nanoparticles can be uniformly dispersed within the mesoporous channels of the hierarchical framework heteroatom molecular sieve.

[0089] In one embodiment, in step S1, the molar ratio of the silicon source (based on SiO2): template agent: framework heteroatom precursor (based on heteroatom element Q): water: metal element M: polyhydroxy auxiliary agent: silanizing agent is 1:(0.005~1):(0.001~0.04):(10~80):(0.001~0.2):(0.5~5):(0.025~0.4);

[0090] The preferred ratio is 1: (0.005~1): (0.002~0.035): (10~80): (0.003~0.14): (0.5~5): (0.025~0.3).

[0091] Specifically, the water used in step S1 can be the water commonly used in the synthesis of molecular sieves, and deionized water is preferred to avoid the introduction of heteroatoms.

[0092] In a preferred embodiment, step S1 includes the following steps:

[0093] a. Mix the template agent, silicon source, framework heteroatom precursor and water to obtain a silicon hydrolysis solution;

[0094] b. Add the polyhydroxy additive to the aqueous solution of the metal M precursor to obtain a first mixture; mix the first mixture with a silicon hydrolysis solution to obtain a second mixture;

[0095] c. Add the silanizing agent to the second mixture, and mix to obtain the reaction mixture;

[0096] Preferably, the mixing conditions in step c include stirring at 20–80°C for 0.5–2 hours.

[0097] In one embodiment, the silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol; preferably, it is selected from at least one of silicone grease, solid silica gel, and fumed silica.

[0098] A further preferred option is a silicone grease, wherein the silicone grease has the general formula shown in formula (A):

[0099]

[0100] Where R a R b R c R d Each is independently selected from alkyl groups having 1 to 6 carbon atoms, wherein the alkyl group is branched or straight-chain alkyl; preferably, R a R b R c R d Each is independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms or branched alkyl groups having 3 to 4 carbon atoms; more preferably, the R a R b R c R d Each is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

[0101] In a preferred embodiment, the silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silicone grease.

[0102] According to this disclosure, in step S1, the template agent is an organic base, preferably at least one selected from quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines. The quaternary ammonium base can be an organic quaternary ammonium base; the aliphatic amine can be a compound formed by replacing at least one hydrogen atom in NH3 with an aliphatic hydrocarbon group (such as an alkyl group); the aliphatic alcoholic amine can be a compound formed by replacing at least one hydrogen atom in various NH3 groups with a hydroxyl-containing aliphatic group (such as an alkyl group).

[0103] In a further preferred embodiment, the template agent is selected from at least one of quaternary ammonium bases with the structure shown in formula (B):

[0104] R1, R2, R3 and R4 are each selected from alkyl groups having 1 to 4 carbon atoms, preferably straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 4 carbon atoms, more preferably R1, R2, R3 and R4 are each selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and tert-butyl.

[0105] In a preferred embodiment, the molecular sieve in the composite catalytic material is an MFI type molecular sieve, and the template agent is tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide; or

[0106] In another preferred embodiment, the molecular sieve in the composite catalytic material is a MEL-type molecular sieve, and the template agent is tetrabutylammonium hydroxide or a mixture of tetrabutylammonium hydroxide and one or more selected from tetrabutylammonium chloride and tetrabutylammonium bromide; or

[0107] In another preferred embodiment, the molecular sieve in the composite catalytic material is a Beta-type molecular sieve, and the template agent is tetraethylammonium hydroxide or a mixture of tetraethylammonium hydroxide and one or more selected from tetraethylammonium chloride and tetraethylammonium bromide.

[0108] In one embodiment, in step a, the silicon source is an organosilicon grease, and after mixing the template agent, organosilicon grease, framework heteroatom precursor and water, a hydrolysis and alcohol removal treatment is further included to obtain the hydrolysate solution.

[0109] The conditions for the hydrolysis-induced alcohol removal treatment include: stirring and hydrolyzing at 0–95°C for 2–10 hours; preferably, stirring and hydrolyzing at 50–95°C for 2–8 hours; wherein the hydrolysis-induced alcohol removal treatment results in the alcohol produced by the hydrolysis of the organosilicon source having a mass content of less than 10 ppm in the hydrolysis solution.

[0110] According to this disclosure, the range of types of metal precursors is relatively wide, and any substance containing the metal element (e.g., a compound containing the metal element and / or a metal element) can achieve the purpose of this disclosure.

[0111] In one embodiment, in step S1, the skeletal heteroatom precursor includes at least one of an organic skeletal heteroatom precursor and an inorganic skeletal heteroatom precursor; the inorganic skeletal heteroatom precursor is at least one of a chloride, nitrate, or sulfate of a heteroatom element; the inorganic skeletal heteroatom precursor is an organic ester containing a heteroatom element, selected from at least one structure with the general formula shown in formula (C) below:

[0112]

[0113] R5, R6, R7 and R8 are each selected from alkyl groups having 1 to 6 carbon atoms, preferably straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms, and more preferably R5, R6, R7 and R8 are each selected from straight-chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms.

[0114] Optionally, R5, R6, R7 and R8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl; preferably, each is independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.

[0115] In one optional embodiment, the skeletal heteroatom is titanium, and the skeletal heteroatom precursor is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate.

[0116] In one optional embodiment, the skeletal heteroatom is boron, and the skeletal heteroatom precursor is selected from one or more of boric acid and borate.

[0117] In one optional embodiment, the framework heteroatom is tin, and the framework heteroatom precursor is selected from one or more of tin halide, tin halide, tin sulfate, tin sulfate, stannate, stanous acid, tin nitrate, tin oxide, and tin oxide.

[0118] In one optional embodiment, the framework heteroatom is aluminum, and the framework heteroatom precursor is selected from one or more of sodium aluminate, aluminum sulfate, boehmite, metallic aluminum, aluminum nitrate, aluminum isopropoxide, and aluminum hydroxide.

[0119] In one optional embodiment, the skeletal heteroatom is phosphorus, and the skeletal heteroatom precursor is selected from one or more of orthophosphoric acid, triethylphosphoric acid, and metaphosphate.

[0120] In one optional embodiment, the framework heteroatom is germanium, and the framework heteroatom precursor is selected from one or more of germanium oxide, germanium alkoxide, germanium chloride, and sodium germanate.

[0121] In one embodiment, in step S1, the metal M precursor is one or more of inorganic metal compounds and organometallic compounds; the inorganic metal compound is a water-soluble inorganic salt of metal element M; the water-soluble inorganic salt of metal element M is selected from one or more of chlorides, hydrated chlorides, sulfates, hydrated sulfates, and nitrates of metal element M; the organometallic compound is an organic ligand compound of metal element M; preferably, the metal M precursor is a water-soluble inorganic salt of metal element M.

[0122] The metallic element M is selected from one or more of manganese, iron, cobalt, nickel, palladium, platinum, copper and gold;

[0123] Preferably, the metal M precursor is an aqueous solution of the metal M precursor, wherein the molar ratio of metal element M to water in the aqueous solution of the metal M precursor is 1:(50-500).

[0124] In one embodiment, in step S1, the polyhydroxy auxiliary agent is selected from one or more of polyols and sugars;

[0125] In a preferred embodiment, the polyol comprises one or more of ethylene glycol, glycerol, pentaerythritol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and polyether polyols; wherein the polyether polyol comprises one or more of propylene glycol polyether, trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol; the weight-average molecular weight of the propylene glycol polyether is 800–2000, and the weight-average molecular weight of each of the trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol is independently 400–4000;

[0126] The carbohydrates include one or more of glucose, sucrose, fructose, starch, and cellulose.

[0127] In one embodiment, in step S1, the silanizing agent has the general formula R9Si(R 10 (R) 11 )R 12 Among them, R9 and R 10 R 11 R 12 Each can be independently a halogen, alkyl, alkoxy, aromatic, mercapto, or amino group, and R9, R 10 R 11 R 12 At least one of them is an alkyl, alkoxy, aromatic, mercapto, or amino group; the number of carbon atoms of the alkyl, alkoxy, mercapto, and amino groups is 1 to 18, preferably 1 to 12; the number of carbon atoms of the aromatic group can be 6 to 18, preferably 6 to 12.

[0128] Preferably, the silanizing agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, 1,7-dichlorooctylmethyltetrasiloxane, hexadecyltrimethoxysilane, octyltriethoxysilane, 3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane; more preferably, at least one of N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

[0129] In this disclosure, different silanizing agents can be selected for different metal elements M. For example, when the metal element M is Co, the silanizing agent is at least one of N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane; when the metal element M is Au or Pt, the silanizing agent is at least one of 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane.

[0130] In one embodiment, in step S2, the conditions for the hydrothermal crystallization treatment include: being carried out under autogenous pressure, with a hydrothermal crystallization time of 0.5 to 10 days and a hydrothermal crystallization temperature of 110 to 200°C; preferably, the hydrothermal crystallization time is 0.5 to 5 days and the hydrothermal crystallization temperature is 150 to 200°C.

[0131] In one embodiment, in step S2, the conditions for the calcination treatment include: a calcination temperature of 400–900°C and a calcination time of 1–16 hours; preferably, the calcination temperature is 400–800°C and the calcination time is 2–8 hours.

[0132] In this disclosure, the samples were characterized using a LabRAMHR UV-NIR confocal microscope Raman spectrometer. The test conditions were: room temperature, ambient pressure, laser wavelength of 532 nm, and spectral acquisition range of 170–1200 cm⁻¹. -1 .

[0133] The UV-Vis diffuse reflectance spectra of the solid samples were measured using a SHIMADZU UV-3100 UV-Vis spectrometer, with a test range of 400–4000 cm⁻¹. -1 .

[0134] X-ray diffraction (XRD) phase diagrams of the samples were determined using a Siemens D5005 X-ray diffractometer with Kα (Cu) as the X-ray source and a test range of 2θ from 0.5° to 70°.

[0135] The scanning electron microscope (SEM) images of the samples were obtained using a Hitachi S4800 high-resolution cold field emission scanning electron microscope.

[0136] Transmission electron microscopy (TEM) images of the samples were obtained using a Tecnai G2F20S-TWIN TEM microscope manufactured by FEI. The average particle size of the metal oxide nanoparticles was determined based on TEM measurements.

[0137] The total specific surface area and total pore volume of the samples were determined using a Micromeritics ASAP245 static nitrogen adsorption analyzer according to the ASTM D4222-98 standard method. The adsorption and desorption isotherms of the samples at low temperatures were determined according to the ASTM D4222-98 standard method.

[0138] Preparation Example 1

[0139] (1) 1.6 g of 25.05% by weight tetrapropylammonium hydroxide (TPAOH, 0.002 mol) aqueous solution, 20.8 g (0.1 mol) tetraethyl silicate, 0.17 g (0.0005 mol) tetrabutyl titanate and 9 g water (0.5 mol) were added sequentially into a 500 mL beaker, placed on a magnetic stirrer with heating and stirring functions and mixed evenly. The mixture was stirred at 80 °C for 3 hours, and the evaporated water was replenished periodically to obtain a colorless and transparent silica gel solution.

[0140] (2) Stir 0.3g (0.001mol) cobalt nitrate hexahydrate and 1.8g water evenly, then add 0.5mmol of ethylene glycol to mix the aqueous solution of the metal with the hydrolysis solution of silicon obtained in step (1);

[0141] (3) Add 0.56g of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane (silane coupling agent kh-792, 0.0025mol) to the mixture in step (2) and stir for 0.5 hours;

[0142] (4) The mixture obtained in step (3) is transferred to a stainless steel sealed reactor and crystallized at 170℃ for 28 hours to obtain a sample. The obtained sample is filtered, washed, dried at 120℃ for 6 hours, and then calcined in a muffle furnace at 550℃ for 6 hours to obtain the composite catalytic material product of metal nanoparticles and molecular sieves described in this invention. The obtained product is denoted as CAT-1. Its BET specific surface area, total pore volume, micropore volume, mesopore volume, and metal nanoparticle particle size are shown in Table 2. 29 Si NMR image as shown Figure 1 As shown.

[0143] Preparation Examples 2-9

[0144] The corresponding products were prepared according to the method in Preparation Example 1. The products obtained are denoted as CAT-2 to CAT-9. The proportions, synthesis conditions, and results are shown in Table 1.

[0145] Preparation Example 10

[0146] Cobalt-containing hierarchical porous β-zeolite was prepared by referring to the method of Example 1, but changing the ratio and template agent. The resulting product was denoted as CAT-10. The template agent used was tetraethylammonium hydroxide (TEAOH). The ratio, synthesis conditions and results are shown in Table 1.

[0147] Preparation Example 11

[0148] Cobalt-containing hierarchical porous MEL molecular sieves were prepared by referring to the method of Example 1, but changing the ratio and template agent. The resulting product was denoted as CAT-11. The template agent used was tetrabutylammonium hydroxide (TBAOH). The ratio, synthesis conditions and results are shown in Table 1.

[0149] Preparation Example 12

[0150] The corresponding product was prepared according to the method of Preparation Example 1. The proportions, synthesis conditions, and results are shown in Table 1. Other conditions and operations were the same as in Preparation Example 1. The obtained product was denoted as CAT-12. The hydrothermal crystallization temperature was 120℃, the time was 8 days, the calcination temperature was 850℃, and the calcination time was 10 hours.

[0151] Preparation of Comparative Example 1

[0152] Prepared according to the method of Example 1, except that no silanizing agent is added, and the resulting product is denoted as DCAT-1.

[0153] Preparation of Comparative Example 2

[0154] 0.03 g of cobalt nitrate hexahydrate and 0.18 g of water were stirred evenly to obtain an aqueous solution of the metal. Then, 10.2 g of alumina support (Innochem catalog number A17263) was added and stirred for 4 h. The solvent was evaporated, the solid was collected and dried at 110 °C for 6 h, and then calcined in a muffle furnace at 550 °C for 6 h. The resulting product was designated as DCAT-2.

[0155] Preparation of Comparative Example 3

[0156] 0.03 g of cobalt nitrate hexahydrate and 0.18 g of water were stirred evenly to obtain an aqueous solution of the metal. Then, 6 g of titanium silicon MFI molecular sieve support was added, and the mixture was stirred for 4 h. The solvent was evaporated, and the solid was collected and dried at 110 °C for 6 h. After that, it was calcined in a muffle furnace at 550 °C for 6 h. The resulting product was designated as DCAT-3.

[0157] The titanium-silicon MFI molecular sieve carrier is prepared according to Preparation Example 1. The difference between Preparation Example 1 and Preparation Example 1 is that step (2) is not performed, that is, cobalt nitrate hexahydrate and ethylene glycol are not added in the molecular sieve synthesis. The rest of the process is the same as Preparation Example 1.

[0158] The BET specific surface area, total pore volume, micropore volume, and mesopore volume of the products obtained from the above examples and comparative examples, as well as the average particle size of the metal nanoparticles in the composite materials, are listed in Table 2 below.

[0159] Table 1

[0160]

[0161]

[0162] In Table 1, cobalt nitrate is cobalt nitrate hexahydrate; TPAOH is tetrapropylammonium hydroxide, TPABr is tetrapropylammonium bromide, TBAOH is tetrabutylammonium hydroxide, TEAOH is tetraethylammonium hydroxide; PHAPTMS is N-phenyl-3-aminopropyltrimethoxysilane, APTES is 3-aminopropyltriethoxysilane, and KH792 is silane coupling agent KH792 (a bisamino functional group silane, N-aminoethyl-γ-aminopropyltrimethoxysilane). The reagents used in this disclosure can be obtained through conventional purchasing channels.

[0163] Table 2

[0164]

[0165] Pores with a diameter less than 2 nm are classified as micropores; pores with a diameter between 2 and 50 nm are classified as mesopores.

[0166] As shown in Table 2, compared with Comparative Example 1 (without adding silanizing agent), Examples 1 to 12 of this disclosure added silanizing agent during the preparation process, and the resulting products had higher mesopore volumes, indicating that the method provided in this disclosure can effectively expand the pores of molecular sieves.

[0167] Furthermore, compared with DCAT-1 to DCAT-3, the composite catalytic materials CAT-1 to CAT-12 provided in this disclosure can simultaneously possess large mesopore volume, large specific surface area, and smaller metal nanoparticle size, indicating that the composite catalytic materials obtained in this disclosure have lower metal nanoparticle aggregation and higher dispersion.

[0168] Reaction Example 1

[0169] This is used to illustrate the effect of the oxygen oxidation of xylene provided by the present invention.

[0170] The catalysts prepared in the above preparation examples and comparative examples were used to catalyze the oxygen oxidation of p-xylene, including: contacting 1 mmol of p-xylene with 50 mg of catalyst in a slurry bed reactor (the weight ratio of catalyst to p-xylene was 1:2.12), while the reactor was simultaneously exposed to oxygen at a pressure of 2 MPa, the contact temperature was 200 °C, and the contact time was 24 h. The specific substances and results are shown in Table 3 below.

[0171] The distribution of the obtained products was determined using an HP-5 capillary column (30m × 0.25mm) on an Agilent 6890N chromatograph.

[0172] p-Xylene conversion rate (%) = number of moles of p-xylene participating in the reaction / number of moles of p-xylene added × 100%.

[0173] Selectivity of terephthalic acid (%) = number of moles of terephthalic acid / number of moles of p-xylene participating in the reaction × 100%.

[0174] Wherein, the number of moles of p-xylene participating in the reaction = the number of moles of p-xylene fed into the reaction mixture - the number of moles of p-xylene remaining in the reaction mixture.

[0175] Table 3

[0176]

[0177] According to the data in Table 3, compared with catalysts DCAT-1 to DCAT-3, the catalyst Q0 prepared according to the method of this disclosure is in the range of 0.03 to 0.1. This composite catalytic material has higher catalytic activity, better catalytic effect in the oxygen oxidation reaction of xylene, and higher xylene conversion rate and terephthalic acid selectivity.

[0178] Comparing preparation examples 1-11 with preparation example 12, the composite catalytic materials prepared in preparation examples 1-11 have a Q0 value in the range of 0.05-0.09, exhibiting better catalytic effect in the oxygen oxidation reaction of p-xylene, with higher p-xylene conversion rate and terephthalic acid selectivity.

[0179] Reaction Example 2

[0180] An oxidation reaction was carried out using CAT-1 as a catalyst and p-xylene as a raw material. The reaction effects under different oxidation conditions were tested, and the specific reaction conditions and results are listed in Table 4 below. In the table below, the mass of the catalyst is 50 mg.

[0181] Table 4

[0182]

[0183] As shown in Table 4, comparing the catalytic effects obtained by using CAT-1 in Reaction Example 2 and Reaction Example 1, it can be seen that the oxidation reaction effect is better and the conversion rate of p-xylene and the selectivity of terephthalic acid are higher when the reaction temperature is in the range of 150-250℃, the reaction time is 2-24h, the oxygen pressure is 1-3MPa, and the weight ratio of catalyst to p-xylene is in the range of 1:(2-10).

[0184] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0185] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0186] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing terephthalic acid by oxygen oxidation, characterized in that, The method includes the following steps: In the presence of oxygen, p-xylene is brought into contact with a catalyst to undergo an oxidation reaction; The catalyst is a composite catalytic material, which includes a framework heteroatom molecular sieve and a metal element M dispersed within the crystals of the molecular sieve; the framework heteroatom molecular sieve is a molecular sieve in which at least part of the silicon in the all-silicon molecular sieve framework is replaced by a heteroatom element Q, and the heteroatom element Q is selected from one or more of titanium, boron and tin; the metal element M is selected from one or more of manganese, iron, cobalt and copper. The catalyst is prepared by a method comprising the following steps: S1, a. Mix the template agent, silicon source, framework heteroatom precursor and water to obtain a silicon hydrolysis solution; b. Add a polyhydroxy auxiliary agent to the aqueous solution of the metal M precursor to obtain a first mixture; mix the first mixture with the silicon hydrolysis solution to obtain a second mixture; c. Add a silanizing agent to the second mixture and mix to obtain a reaction mixture; S2. The reaction mixture is subjected to hydrothermal crystallization and calcination treatment; The silanizing agent contains at least one coordinating group that complexes with the metal element M; the polyhydroxy auxiliary is a compound containing at least two hydroxyl groups. The composite catalytic material has the following characteristics: 29 Si NMR characteristics: The composite catalytic material 29 In the Si NMR spectrum, the intensity at a chemical shift of -103 ppm is denoted as Q3, and the intensity at a chemical shift of -113 ppm is denoted as Q4. As defined in equation (1), Q0 is any value between 0.03 and 0.1; Q0 = Q3 / Q4 (1).

2. The method according to claim 1, characterized in that, The conditions for the oxidation reaction include: a reaction temperature of 150-300℃; a time of 1-48h; and an oxygen pressure of 1-3MPa. The weight ratio of the catalyst to the p-xylene is 1:(1-20).

3. The method according to claim 1, characterized in that, The reactor for the oxidation reaction is at least one of a batch reactor, a fixed-bed reactor, a moving-bed reactor, a suspended-bed reactor, and a slurry-bed reactor.

4. The method according to claim 2, characterized in that, The conditions for the oxidation reaction include: a reaction temperature of 150-250℃; a time of 2-24h; and an oxygen pressure of 1.5-3MPa.

5. The method according to claim 2, characterized in that, The weight ratio of the catalyst to the p-xylene is 1:(2-10).

6. The method according to claim 1, characterized in that, Q0 is any value between 0.05 and 0.

09.

7. The method according to claim 1, characterized in that, The framework heteroatom molecular sieve in the composite catalytic material is at least one of MFI structure molecular sieve, MEL structure molecular sieve, BEA structure molecular sieve, MWW structure molecular sieve, two-dimensional hexagonal structure molecular sieve, MOR structure molecular sieve and TUN structure molecular sieve.

8. The method according to claim 1, characterized in that, The skeletal heteroatom molecules are selected from one or more of the following molecular sieve structures: MFI, MEL, BEA, MCM, and SBA.

9. The method according to claim 8, characterized in that, The framework heteroatom molecular sieve is one or more of MFI structure molecular sieve, MEL structure molecular sieve and BEA structure molecular sieve.

10. The method according to claim 1, characterized in that, In the composite catalytic material, the molar ratio of the framework heteroatom element to silicon element is (0.001~0.04):1; the molar ratio of the metal M element to silicon element is (0.001~0.2):

1.

11. The method according to claim 10, characterized in that, In the composite catalytic material, the molar ratio of the framework heteroatom element to silicon element is (0.002~0.035):1; the molar ratio of the metal M element to silicon element is (0.003~0.14):

1.

12. The method according to claim 1, characterized in that, The composite catalytic material has a BET specific surface area of ​​400~800 m². 2 / g, the total pore volume is 0.3~0.65mL / g, the micropore volume is 0.1~0.19mL / g, the mesopore volume is 0.20~0.46mL / g, and the metal element M in the composite catalytic material exists in the form of metal nanoparticles with an average particle size of 0.5~9nm.

13. The method according to claim 1, characterized in that, In step S1, the molar ratio of the silicon source (based on SiO2): template agent: framework heteroatom precursor (based on heteroatom element Q): water: metal element M: polyhydroxy auxiliary agent: silanizing agent is 1: (0.005~1): (0.001~0.04): (10~80): (0.001~0.2): (0.5~5): (0.025~0.4).

14. The method according to claim 13, characterized in that, In step S1, the molar ratio of the silicon source (based on SiO2): template agent: framework heteroatom precursor (based on heteroatom element Q): water: metal element M: polyhydroxy auxiliary agent: silanizing agent is 1: (0.005~1): (0.002~0.035): (10~80): (0.003~0.14): (0.5~5): (0.025~0.3).

15. The method according to claim 1, characterized in that, The mixing conditions in step c include stirring at 20~80℃ for 0.5~2 hours.

16. The method according to claim 1, characterized in that, The silicon source is selected from at least one of silicone grease, solid silica gel, fumed silica, and silica sol.

17. The method according to claim 16, characterized in that, The silicon source is selected from at least one of organosilicon grease, solid silica gel, and precipitated silica.

18. The method according to claim 17, characterized in that, The silicon source is an organosilicone grease, and the organosilicone grease has the general formula shown in formula (A): （A）； Where R a R b R c R d Each is independently selected from alkyl groups having 1 to 6 carbon atoms, wherein the alkyl group is a branched or straight-chain alkyl group.

19. The method according to claim 18, characterized in that, R a R b R c R d Each is independently selected from straight-chain alkyl groups having 1 to 4 carbon atoms or branched alkyl groups having 3 to 4 carbon atoms.

20. The method according to claim 19, characterized in that, The R a R b R c R d Each is independently selected from methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, or tert-butyl.

21. The method according to claim 18, characterized in that, The silicone grease is selected from one or more of tetramethyl silicate, tetraethyl silicate, tetrabutyl silicate, and dimethyl diethyl silicone grease.

22. The method according to claim 1, characterized in that, The template agent is an organic base.

23. The method according to claim 22, characterized in that, The template agent is selected from at least one of quaternary ammonium bases, aliphatic amines, and aliphatic alcoholic amines.

24. The method according to claim 23, characterized in that, The template agent is selected from at least one of the quaternary ammonium bases with the structure shown in formula (B) below: (B); wherein R1, R2, R3 and R4 are each selected from alkyl groups having 1 to 4 carbon atoms.

25. The method according to claim 24, characterized in that, R1, R2, R3 and R4 are each selected from straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 4 carbon atoms.

26. The method according to claim 25, characterized in that, R1, R2, R3 and R4 are each selected from at least one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl and tert-butyl.

27. The method according to claim 24, characterized in that, The molecular sieve in the composite catalytic material is an MFI type molecular sieve, and the template agent is tetrapropylammonium hydroxide or a mixture of tetrapropylammonium hydroxide and one or more selected from tetrapropylammonium chloride and tetrapropylammonium bromide; or The molecular sieve in the composite catalytic material is a MEL-type molecular sieve, and the template agent is tetrabutylammonium hydroxide or a mixture of tetrabutylammonium hydroxide and one or more selected from tetrabutylammonium chloride and tetrabutylammonium bromide; or The molecular sieve in the composite catalytic material is a Beta-type molecular sieve, and the template agent is tetraethylammonium hydroxide or a mixture of tetraethylammonium hydroxide and one or more selected from tetraethylammonium chloride and tetraethylammonium bromide.

28. The method according to claim 1, characterized in that, In step a, the silicon source is an organosilicone grease. After mixing the template agent, organosilicone grease, framework heteroatom precursor and water, the process further includes hydrolysis and alcohol removal treatment to obtain the hydrolysate solution. The conditions for the hydrolysis and alcohol removal treatment include: stirring and hydrolyzing at 0~95℃ for 2~10 hours.

29. The method according to claim 28, characterized in that, The conditions for the hydrolysis and alcohol removal treatment include: stirring and hydrolyzing at 50~95℃ for 2~8 hours.

30. The method according to claim 1, characterized in that, In step S1, the skeletal heteroatom precursor includes at least one of an organic skeletal heteroatom precursor and an inorganic skeletal heteroatom precursor; the inorganic skeletal heteroatom precursor is at least one selected from chlorides, nitrates, and sulfates containing heteroatom element Q; the organic skeletal heteroatom precursor is an organic ester containing heteroatom element Q, selected from at least one structure with the general formula shown in formula (C) below: （C）； R5, R6, R7 and R8 are each selected from alkyl groups having 1 to 6 carbon atoms.

31. The method according to claim 30, characterized in that, R5, R6, R7 and R8 are each selected from straight-chain alkyl groups having 1 to 4 carbon atoms and branched alkyl groups having 3 to 6 carbon atoms.

32. The method according to claim 30, characterized in that, R5, R6, R7 and R8 are each selected from straight-chain alkyl groups having 2 to 4 carbon atoms and branched alkyl groups having 2 to 4 carbon atoms.

33. The method according to claim 30, characterized in that, R5, R6, R7 and R8 are each selected from one of methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, isopentyl, hexyl or isohexyl.

34. The method according to claim 33, characterized in that, R5, R6, R7 and R8 are each independently selected from one of ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl or tert-butyl.

35. The method according to claim 30, characterized in that, When the framework heteroatom is titanium, the framework heteroatom precursor is selected from one or more of titanium tetrachloride, titanium sulfate, titanium nitrate, tetraethyl titanate, tetrapropyl titanate, and tetrabutyl titanate; when the framework heteroatom is boron, the framework heteroatom precursor is selected from one or more of boric acid and borate; when the framework heteroatom is tin, the framework heteroatom precursor is selected from one or more of tin halide, stannous halide, stannous sulfate, stannous sulfate, stannate, stannous nitrate, tin oxide, and stannous oxide.

36. The method according to claim 1, characterized in that, In step S1, the precursor of metal M is one or more of inorganic metal compounds and organometallic compounds; the inorganic metal compound is a water-soluble inorganic salt of metal element M; the water-soluble inorganic salt of metal element M is selected from one or more of chloride, hydrated chloride, sulfate, hydrated sulfate and nitrate of metal element M; the organometallic compound is an organic ligand compound of metal element M.

37. The method according to claim 36, characterized in that, The precursor of metal M is a water-soluble inorganic salt of the metal element M.

38. The method according to claim 36, characterized in that, The metal M precursor is an aqueous solution of the metal M precursor, wherein the molar ratio of metal element M to water in the aqueous solution of the metal M precursor is 1:(50~500).

39. The method according to claim 1, characterized in that, In step S1, the polyhydroxy auxiliaries are selected from one or more of polyols and sugars.

40. The method according to claim 39, characterized in that, The polyols include one or more of ethylene glycol, glycerol, pentaerythritol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and polyether polyols; wherein the polyether polyols include one or more of propylene glycol polyether, trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol; the weight-average molecular weight of the propylene glycol polyether is 800-2000, and the weight-average molecular weight of each of the trimethylolpropane polyether, polypropylene glycol, polypropylene triol, and polytetrahydrofuran glycol is independently 400-4000; The carbohydrates include one or more of glucose, sucrose, fructose, starch, and cellulose.

41. The method according to claim 1, characterized in that, In step S1, the general formula of the silanizing agent is R9Si(R 10 (R) 11 )R 12 Among them, R9 and R 10 R 11 R 12 Each can be independently a halogen, alkyl, alkoxy, aromatic or amino group, and R9, R 10 R 11 R 12 At least one of them is an alkyl, alkoxy, aromatic or amino group; the number of carbon atoms of the alkyl, alkoxy and amino groups is independently selected from any integer from 1 to 18, and the number of carbon atoms of the aromatic group is selected from any integer from 6 to 18.

42. The method according to claim 41, characterized in that, The silanizing agent is selected from one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, hexadecyltrimethoxysilane, octyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

43. The method according to claim 42, characterized in that, The silanizing agent is selected from at least one of N-phenyl-3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane.

44. The method according to claim 1, characterized in that, In step S2, the conditions for the hydrothermal crystallization treatment include: being carried out under autogenous pressure, a hydrothermal crystallization time of 0.5 to 10 days, and a hydrothermal crystallization temperature of 110 to 200°C. The conditions for the calcination treatment include: a calcination temperature of 400~900℃ and a calcination time of 1~16 hours.

45. The method according to claim 44, characterized in that, In step S2, the conditions for the hydrothermal crystallization treatment include: being carried out under autogenous pressure, a hydrothermal crystallization time of 0.5 to 5 days, and a hydrothermal crystallization temperature of 150 to 200°C. The conditions for the roasting treatment include: a roasting temperature of 400~800℃ and a roasting time of 2~8 hours.

Images