Heteroatom molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to a method for preparing a heteroatom molecular sieve, which comprises the following steps: mixing a silicon source, a heteroatom source, an organic template agent, graphene powder and water at a first temperature to obtain mixed slurry; carrying out hydrolysis treatment on the mixed slurry at a second temperature to obtain a hydrolysis solution; carrying out a hydrothermal reaction on the hydrolysis solution, carrying out solid-liquid separation, and roasting a recovered solid-phase product; wherein the graphene powder is prepared by a supercritical carbon dioxide stripping method. The heteroatom molecular sieve prepared by the invention has rich hierarchical pore structures, the reactivity center of the heteroatom molecular sieve is high in accessibility, the heteroatom molecular sieve has better catalytic reaction activity and activity stability, and has higher target product selectivity, and on the other hand, the heteroatom molecular sieve prepared by the invention has suitable ordered mesopores and / or macropores, and the selectivity of the heteroatom molecular sieve is improved. The phenol hydroxylation reaction is facilitated, the phenol conversion rate is high, the benzenediol selectivity is good, and the para-ortho ratio of the benzenediol is high.

Description

Technical Field

[0001] The present invention belongs to the field of heteroatom molecular sieves, and specifically relates to a heteroatom molecular sieve and a preparation method and use thereof. Background Art

[0002] Heteroatom molecular sieves such as titanium silicon molecular sieves can use pollution-free low-concentration hydrogen peroxide as an oxidant in the oxidation reaction of organic matter, and can catalyze various types of organic oxidation reactions, such as epoxidation of olefins, partial oxidation of alkanes, oxidation of alcohols, hydroxylation of phenols, etc., avoiding the problems of complex oxidation process and environmental pollution, and have the advantages of energy saving, economy and environmental friendliness that traditional oxidation systems cannot match, and have good reaction selectivity, so they have great industrial utilization prospects. However, the repeatability and stability of the current heteroatom molecular sieve synthesis method are not very ideal, especially in the preparation process, it is easy to produce heteroatom oxide crystal phases, which seriously affects the reaction activity of heteroatom molecular sieves and the selectivity of target products. Summary of the invention

[0003] The purpose of the present invention is to provide a heteroatom molecular sieve and a preparation method and use thereof. The heteroatom molecular sieve prepared by the present invention has appropriately ordered mesopores and / or macropores, the reaction active centers of the heteroatom molecular sieve are highly accessible, have good catalytic reaction activity and activity stability, and have high selectivity for target products.

[0004] In order to achieve the above object, the present invention provides a method for preparing a heteroatom molecular sieve, wherein the method comprises:

[0005] S1: mixing a silicon source, a heteroatom source, an organic template, graphene powder and water at a first temperature to obtain a mixed slurry;

[0006] S2 hydrolyzing the mixed slurry at a second temperature to obtain a hydrolyzed solution;

[0007] S3: subjecting the hydrolyzed solution to a hydrothermal reaction, and after solid-liquid separation, calcining the recovered solid phase product;

[0008] Wherein, the graphene powder is prepared by a supercritical carbon dioxide exfoliation method, and the second temperature is higher than the first temperature.

[0009] Optionally, the graphene powder has a D50 particle size of 0.2 to 5 μm, a flake diameter of 1 to 2000 nm, a number of layers of less than 10, and a specific surface area of ​​100 to 800 m 2 / g.

[0010] Optionally, the molar ratio of the silicon source calculated as SiO2, the heteroatom source calculated as heteroatom elements, the graphene powder calculated as carbon element, the organic template calculated as nitrogen element and water is 100: (0.1~5): (0.01~2): (5~50): (800~10000).

[0011] Optionally, in step S1, the silicon source is selected from an organic silicon source and / or an inorganic silicon source. Preferably, the organic silicon source is selected from one or more of methyl silicate, ethyl silicate, propyl silicate and butyl silicate; preferably, the inorganic silicon source is selected from one or more of methyl silane, ethyl silane and propyl silane;

[0012] The heteroatom source is selected from one or more of a titanium source, an iron source, a vanadium source and a tin source. Preferably, the heteroatom source is selected from one or more of compounds containing titanium, iron, vanadium and tin;

[0013] The organic template is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds.

[0014] Optionally, step S1 further includes:

[0015] a. mixing a silicon source and a heteroatom source to obtain a first mixed material;

[0016] b. mixing the organic template, graphene powder and optional water to obtain a second mixed material;

[0017] c. Mixing the first mixed material with the second mixed material to obtain the mixed slurry.

[0018] Optionally, in step S1, the first temperature is 20 to 60° C., and the mixing time is 0.1 to 6 hours;

[0019] In step S2, the second temperature is 70 to 100° C., and the stirring time of the hydrolysis treatment is 3 to 24 hours;

[0020] Wherein, the temperature difference between the second temperature and the first temperature is 10 to 80°C;

[0021] In step S3, the conditions of the hydrothermal reaction include: being carried out under autogenous pressure, the hydrothermal reaction temperature is 110-200° C., and the hydrothermal reaction time is 6-96 hours; the conditions of the calcination include: the calcination temperature is 400-800° C., and the calcination time is 1-12 hours.

[0022] The second aspect of the present invention provides a heteroatom molecular sieve prepared by the method according to the first aspect of the present invention.

[0023] Optionally, the molar ratio of the heteroatom element to the silicon element in the heteroatom molecular sieve is (0.1-8):100.

[0024] Optionally, the BET specific surface area of ​​the heteroatom molecular sieve is 300 to 700 m 2 / g; total pore volume is 0.3~0.8cm 3 / g; mesopore volume is 0.2~0.6cm 3 / g; the ratio of mesopore volume to total pore volume is (0.5-0.9):1; the average particle size of the heteroatom molecular sieve is 0.1-1 μm.

[0025] The third aspect of the present invention provides use of the heteroatom molecular sieve described in the second aspect of the present invention in a phenol hydroxylation reaction.

[0026] Through the above technical scheme, the preparation method provided by the present invention can effectively inhibit the formation of heteroatom oxide crystalline phases during the preparation of heteroatom molecular sieves by adding graphene powder prepared by supercritical carbon dioxide exfoliation method during the preparation of heteroatom molecular sieves, and at the same time, the prepared heteroatom molecular sieves have appropriately ordered mesopores and macropores, which effectively improves the accessibility of the reaction active centers of the heteroatom molecular sieves; on the other hand, adding powdered graphene during the hydrolysis process will promote the effective dispersion of titanium species and better combination with silicon species, further inhibiting the formation of heteroatom oxide crystalline phases, thereby more specifically improving the diffusion rate of materials in the catalytic reaction of heteroatom molecular sieves, further improving the reaction activity and activity stability of heteroatom molecular sieves, and selectivity for target products.

[0027] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following specific embodiments, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 UV-Vis spectra of samples prepared in Example 1 and Comparative Example 6 of the present invention. DETAILED DESCRIPTION

[0030] The specific implementation of the present disclosure is described in detail below in conjunction with the accompanying drawings. It should be understood that the specific implementation described herein is only used to illustrate and explain the present disclosure, and is not used to limit the present disclosure.

[0031] The present disclosure provides a method for preparing a heteroatom molecular sieve, wherein the method comprises:

[0032] S1: mixing a silicon source, a heteroatom source, an organic template, graphene powder and water at a first temperature to obtain a mixed slurry;

[0033] S2 hydrolyzing the mixed slurry at a second temperature to obtain a hydrolyzed solution;

[0034] S3: subjecting the hydrolysis solution to a hydrothermal reaction, and after solid-liquid separation, calcining the recovered solid phase product.

[0035] Wherein, the graphene powder is prepared by a supercritical carbon dioxide exfoliation method, and the second temperature is higher than the first temperature.

[0036] The preparation method provided by the present disclosure can effectively inhibit the formation of heteroatom oxide crystalline phases during the preparation of heteroatom molecular sieves by adding graphene powder prepared by supercritical carbon dioxide exfoliation method during the preparation of heteroatom molecular sieves, so that the prepared heteroatom molecular sieves have appropriately ordered mesopores and macropores, effectively improving the accessibility of the reaction active centers of the heteroatom molecular sieves; on the other hand, since the addition of powdered graphene during the hydrolysis process can promote the effective dispersion of titanium species and better combination with silicon species, the formation of heteroatom oxide crystalline phases is further inhibited, thereby more specifically improving the diffusion rate of materials in the catalytic reaction of the heteroatom molecular sieve, further improving the reaction activity and activity stability of the heteroatom molecular sieve, and the selectivity for the target product.

[0037] In a specific embodiment of the present disclosure, graphite is added to a reactor, the reactor is sealed, a gaseous intercalation medium is introduced into the reactor, and the pressure in the reactor is controlled at 1 to 200 atm by adjusting the gas intake of the gaseous intercalation medium. Under the pressure and stirring conditions, the system temperature is raised to 25 to 500° C. to carry out a molecular intercalation reaction. After the reaction is completed, the pressure is quickly released to quickly reduce the pressure in the reactor to half or less than half of the pressure in the reactor within 0.1 s, and then the gas is released to normal pressure, and the buffer tank is opened to obtain graphene powder.

[0038] In the above embodiment, the graphene powder prepared by supercritical carbon dioxide exfoliation method has a more uniform particle size distribution and fewer layers, which can effectively inhibit the formation of heteroatom oxide crystal phases during the preparation of heteroatom molecular sieves, and make the prepared heteroatom molecular sieves produce appropriately ordered mesopores and / or macropores. On the one hand, it can effectively improve the accessibility of the reaction active centers of the heteroatom molecular sieves; on the other hand, it can further specifically improve the diffusion rate of materials in the catalytic reaction of the heteroatom molecular sieves, thereby improving the reaction activity and activity stability of the heteroatom molecular sieves, as well as the selectivity for the target product.

[0039] In a specific embodiment of the present disclosure, the graphene powder has a D50 particle size of 0.2 to 5 μm, preferably 0.5 to 2 μm, a sheet diameter of 1 to 2000 nm, preferably 10 to 1000 nm, a number of layers of less than 10 layers, preferably less than 8 layers, and a specific surface area of ​​100 to 800 m 2 / g, preferably 150 to 600 m 2 / g.

[0040] In the above embodiment, by introducing the graphene powder prepared by the present disclosure into the reaction mixture for synthesizing the heteroatom molecular sieve, the accessibility of the reaction active centers of the heteroatom molecular sieve can be further improved, so that the heteroatom molecular sieve has better catalytic reaction activity and activity stability, as well as higher target product selectivity.

[0041] In a specific embodiment of the present disclosure, the molar ratio of the silicon source calculated as SiO2, the heteroatom source calculated as heteroatom elements, the graphene powder calculated as carbon element, the organic template calculated as nitrogen element and water is 100: (0.1-5): (0.01-2): (5-50): (800-10000), preferably 100: (0.2-2.5): (0.05-1): (10-25): (1200-5000).

[0042] In a specific embodiment of the present disclosure, in step S1, in step S1, the silicon source is selected from an organic silicon source and / or an inorganic silicon source, preferably, the organic silicon source is selected from one or more of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate; preferably, the inorganic silicon source is selected from one or more of methyl silane, ethyl silane, and propyl silane;

[0043] The heteroatom source is selected from one or more of a titanium source, an iron source, a vanadium source and a tin source. Preferably, the heteroatom source is selected from one or more of compounds containing titanium, iron, vanadium and tin. Among them, the titanium-containing compound can be selected from one or more of titanate, titanium tetrachloride and titanyl sulfate, preferably one or more of tetrabutyl titanate, tetraisopropyl titanate and titanyl sulfate; the iron-containing compound can be selected from one or more of iron nitrate, iron hydroxide, iron oxide, iron chloride, iron sulfate, iron acetylacetonate, iron isopropoxide, iron phosphate, iron acetate and iron acid and its salt, preferably one or more of iron hydroxide, iron oxide, iron chloride, iron sulfate and ferric acid; the vanadium-containing compound can be selected from one or more of vanadic acid, ammonium vanadate, sodium vanadate and vanadium oxide, preferably one or more of ammonium vanadate, sodium vanadate and vanadium oxide; the tin-containing compound can be selected from one or more of ammonium stannate, tin tetrachloride, tin sulfate and tin oxide, preferably one or more of tin tetrachloride and tin oxide;

[0044] The organic template is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds, wherein the quaternary ammonium base compound can be selected from one or more of tetraethylammonium hydroxide, tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; the fatty amine compound can be selected from one or more of ethylamine, n-butylamine, butanediamine and hexamethylenediamine; the alcohol amine compound can be selected from one or more of monoethanolamine, diethanolamine and triethanolamine.

[0045] In a specific implementation of the present disclosure, step S1 further includes:

[0046] a. mixing a silicon source and a heteroatom source to obtain a first mixed material;

[0047] b. mixing the organic template, graphene powder and optional water to obtain a second mixed material;

[0048] c. Mixing the first mixed material with the second mixed material to obtain the mixed slurry.

[0049] In the present invention, by adopting the mixing order in the above-mentioned embodiment, adding powdered graphene during the hydrolysis process can promote the effective dispersion of titanium species and better combination with silicon species, further inhibiting the formation of heteroatom oxide crystal phases, thereby more specifically improving the diffusion rate of materials in the heteroatom molecular sieve catalytic reaction, further improving the reaction activity and activity stability of the heteroatom molecular sieve, and the selectivity for the target product.

[0050] In a specific embodiment of the present disclosure, in step S1, the first temperature is 20 to 60°C, preferably 30 to 50°C, and the mixing time is 0.1 to 6 hours, preferably 0.5 to 3 hours;

[0051] In step S2, the second temperature is 70 to 100° C., preferably 75 to 95° C., and the stirring time of the hydrolysis treatment is 3 to 24 hours, preferably 6 to 12 hours;

[0052] Wherein, the temperature difference between the second temperature and the first temperature is 10 to 80°C, preferably 15 to 65°C;

[0053] In step S3, the conditions of the hydrothermal reaction include: being carried out under autogenous pressure, the hydrothermal reaction temperature is 110-200°C, preferably 130-180°C, and the hydrothermal reaction time is 6-96 hours, preferably 12-72 hours; the conditions of the calcination include: the calcination temperature is 400-800°C, preferably 500-700°C, and the calcination time is 1-12 hours, preferably 2-6 hours.

[0054] A second aspect of the present disclosure provides a heteroatom molecular sieve prepared according to the method described in the first aspect of the present disclosure.

[0055] In a specific embodiment of the present disclosure, the molar ratio of the heteroatom element to the silicon element in the heteroatom molecular sieve is (0.1-8):100, preferably (0.5-4):1.

[0056] In a specific embodiment of the present disclosure, the BET specific surface area of ​​the heteroatom molecular sieve is 300 to 700 m 2 / g, preferably 400 to 600 m 2 / g; total pore volume is 0.3~0.8cm 3 / g, preferably 0.35 to 0.7 cm 3 / g; mesopore volume is 0.2~0.6cm 3 / g, preferably 0.25 to 0.5 cm 3 / g; the ratio of mesopore volume to total pore volume is (0.5-0.9):1, preferably (0.6-0.8):1; the average particle size of the heteroatom molecular sieve is 0.1-1 μm, preferably 0.2-0.5 μm.

[0057] The heteroatom molecular sieve prepared in the present invention has a rich multi-level pore structure, which makes the reactive center of the heteroatom molecular sieve highly accessible, has good catalytic reaction activity and activity stability, and has high selectivity for the target product. On the other hand, the heteroatom molecular sieve prepared in the present invention has appropriately ordered mesopores and / or macropores, which are conducive to the phenol hydroxylation reaction, and has a high phenol conversion rate, a high ratio of ortho-benzene to diphenol, and good selectivity for diphenol.

[0058] The third aspect of the present disclosure provides use of the heteroatom molecular sieve described in the second aspect of the present invention in a phenol hydroxylation reaction.

[0059] In the present disclosure, the reaction conditions for the phenol hydroxylation reaction using the heteroatom molecular sieve as a catalyst include: a reaction temperature of 50 to 80° C. and a reaction time of 1 to 4 hours.

[0060] The present invention is further described below by way of examples, but the present invention is not limited thereto.

[0061] Example 1

[0062] a. Add 1 g of graphite into the reactor, introduce a gaseous intercalation medium (carbon dioxide) into the reactor, and control the pressure in the reactor to 1 atm by adjusting the gaseous intercalation medium intake. Under the pressure and stirring conditions, raise the system temperature to 200°C to carry out a molecular intercalation reaction. After reacting for 0.5 h, quickly release the pressure to quickly reduce the pressure in the reactor to half or less of the pressure in the reactor within 0.1 s, then release the gas to normal pressure, open the buffer tank, and obtain 0.9 g of graphene powder. The D50 particle size of the graphene powder is 2.8 μm, recorded as CUP1.

[0063] b. Mixing 30 g of ethyl silicate and an appropriate amount of tetrabutyl titanate under stirring at 30° C. for 0.5 hour at a stirring speed of 600 rpm to obtain a first mixed material;

[0064] c. stirring and mixing an appropriate amount of graphene powder CUP1 and tetrapropylammonium hydroxide aqueous solution (25% mass concentration) at 35° C. for 2 hours at a stirring speed of 300 rpm to obtain a second mixed material;

[0065] d. Mixing the first mixed material with the second mixed material, stirring and mixing at 75° C. for 2 hours at a stirring speed of 500 rpm to obtain a third mixed material, wherein the addition ratio of the above materials is: the molar ratio of silicate (in terms of SiO2), titanate (in terms of TiO2), graphene (in terms of C), tetrapropylammonium hydroxide (in terms of N) and water is 100:3:0.2:15:5000;

[0066] e After the third mixed material was mixed for 5 hours at 80°C, it was transferred to a sealed high-pressure reactor and hydrothermally treated at 170°C and autogenous pressure for 48 hours to obtain a sample. The obtained sample was filtered, washed, naturally dried, and calcined at 500°C for 3 hours to obtain a heteroatom molecular sieve, which was recorded as A1.

[0067] Example 2

[0068] The method of Example 1 is adopted, except that the molar ratio of silicate (in terms of SiO2), titanate, graphene, tetrapropylammonium hydroxide (in terms of N) and water is 100:3:0.1:20:3000; in step e, the third mixed material is further mixed at 70°C for 12 hours to obtain a heteroatom molecular sieve, which is recorded as A2.

[0069] Example 3

[0070] The method of Example 1 is adopted, except that in step c, the same amount of graphene powder CUP2 is used, and the D50 particle size of the graphene powder is 0.5 μm, to obtain a heteroatom molecular sieve, which is recorded as A3.

[0071] 5 g of graphite was added to the reactor, a gaseous intercalation medium (carbon dioxide) was introduced into the reactor, and the pressure in the reactor was controlled at 100 atm by adjusting the gas intake of the gaseous intercalation medium. Under the pressure and stirring conditions, the system temperature was raised to 200°C to carry out a molecular intercalation reaction. After reacting for 1 hour, the pressure was quickly released to quickly reduce the pressure in the reactor to half or less of the pressure in the reactor within 0.1 second, and then the gas was released to normal pressure, and the buffer tank was opened to obtain 4.6 g of graphene powder, which was recorded as CUP2.

[0072] Example 4

[0073] The method of Example 2 was adopted, except that in step c, the same amount of graphene powder CUP3 was used, and the D50 particle size of the graphene powder was 10 μm, to obtain a heteroatom molecular sieve, which was recorded as A4.

[0074] Among them, 10g of graphite was added to the reactor, and a gaseous intercalation medium (carbon dioxide) was introduced into the reactor. The pressure in the reactor was controlled at 200atm by adjusting the air intake of the gaseous intercalation medium. Under the pressure and stirring conditions, the system temperature was raised to 300°C to carry out a molecular intercalation reaction. After reacting for 4h, the pressure was quickly released to quickly reduce the pressure in the reactor to half or less of the pressure in the reactor within 0.1s, and then the gas was released to normal pressure. The buffer tank was opened to obtain 9.1g of graphene powder, which was recorded as CUP3.

[0075] Example 5

[0076] The method of Example 2 is adopted, except that in step b, stirring and mixing are performed at 60° C. for 1 hour at a stirring speed of 1000 rpm; in step c, stirring and mixing are performed at 60° C. for 0.1 hour at a stirring speed of 100 rpm; in step e, hydrothermal treatment is performed at a temperature of 140° C. and autogenous pressure for 6 hours to obtain a heteroatom molecular sieve, which is recorded as A5.

[0077] Example 6

[0078] The method of Example 2 is adopted, except that, in step b, the same amount of ethyl silicate and ferric nitrate are stirred and mixed at 80° C. for 4 hours; in step c, the same amount of graphene and tetraethylammonium hydroxide are stirred and mixed at 85° C. for 8 hours, and the stirring speed is 500 rpm; wherein the molar ratio of ethyl silicate (in terms of SiO2), ferric nitrate, graphene, tetraethylammonium hydroxide (in terms of N) and water is 100:1:0.2:40:1000, and a heteroatom molecular sieve is obtained, which is recorded as A6.

[0079] Example 7

[0080] The method of Example 1 is adopted, except that in step c, the first mixed material is mixed with the same amount of tetrapropylammonium hydroxide aqueous solution and then mixed with graphene powder CUP1 to obtain a second mixed material, thereby obtaining a heteroatom molecular sieve, which is recorded as A7.

[0081] Comparative Example 1

[0082] The method of Example 1 was adopted, except that no graphene powder was added, to obtain a heteroatom molecular sieve, which was recorded as DB1.

[0083] Comparative Example 2

[0084] The method of Example 1 was adopted, except that the same amount of graphene powder CUP4 (purchased from Changzhou Sixth Element Materials Technology Co., Ltd., product number SE1233) was prepared by redox method, the D50 particle size of the graphene powder was 9 μm, and a heteroatom molecular sieve was obtained, which was recorded as DB2.

[0085] Comparative Example 3

[0086] The method of Example 1 was adopted, except that the same amount of graphene powder CUP5 (purchased from De Chuang (Suzhou) New Material Technology Co., Ltd., product number DCRGO-200) was prepared by redox method, the D50 particle size of the graphene powder was 10 μm, and a heteroatom molecular sieve was obtained, which was recorded as DB3.

[0087] Comparative Example 4

[0088] The method of Example 1 was adopted, except that the same amount of graphene powder CUP6 (purchased from Deyang Encarbon Technology Co., Ltd., product number HE-01) was prepared by solid phase intercalation exfoliation method, and the D50 particle size of the graphene powder was 12 μm, to obtain a heteroatom molecular sieve, recorded as DB4.

[0089] Comparative Example 5

[0090] The method of Example 1 is adopted, except that in step c, the same amount of carbon nanotubes (purchased from Shandong Dazhan Nanomaterial Co., Ltd., product number GT-300) is used, the diameter of the carbon nanotubes is 10-15 nm, and the length is 3-12 μm, to obtain a heteroatom molecular sieve, recorded as DB5.

[0091] Comparative Example 6

[0092] a. Add 1 g of graphite into the reactor, introduce a gaseous intercalation medium (carbon dioxide) into the reactor, and control the pressure in the reactor to 1 atm by adjusting the gaseous intercalation medium intake. Under the pressure and stirring conditions, raise the system temperature to 200°C to carry out a molecular intercalation reaction. After reacting for 0.5 h, quickly release the pressure to quickly reduce the pressure in the reactor to half or less of the pressure in the reactor within 0.1 s, then release the gas to normal pressure, open the buffer tank, and obtain 0.9 g of graphene powder. The D50 particle size of the graphene powder is 2.8 μm, recorded as CUP1.

[0093] b. 30 g of ethyl silicate, an appropriate amount of tetrabutyl titanate and an aqueous solution of tetrapropylammonium hydroxide (25% mass concentration) were stirred and mixed at 35° C. for 2 hours at a stirring speed of 300 rpm to obtain a first mixed material;

[0094] c. After the first mixed material is continuously mixed at 80° C. for 5 hours, an appropriate amount of graphene powder CUP1 is added and stirred at 75° C. for 2 hours at a stirring speed of 500 rpm to obtain a second mixed material, wherein the molar ratio of silicate (in terms of SiO2), titanate, graphene, tetrapropylammonium hydroxide (in terms of N) and water is 100:3:0.2:15:5000;

[0095] e. The second mixed material was transferred to a sealed high-pressure reactor and hydrothermally treated at a temperature of 170°C and autogenous pressure for 48 hours to obtain a sample. The obtained sample was filtered, washed, naturally dried, and then calcined at 500°C for 3 hours to obtain a heteroatom molecular sieve, which was recorded as DB6.

[0096] Test Case

[0097] The heteroatom molecular sieves prepared in Examples 1 to 7 and Comparative Examples 1 to 6 were used as catalysts to carry out phenol hydroxylation reaction, and the specific steps are as follows:

[0098] The catalyst, solvent water, phenol and aqueous hydrogen peroxide solution (the content of H2O2 in the aqueous hydrogen peroxide solution is 30 weight %) are sealed in a high-pressure reactor according to the weight ratio of catalyst: water: phenol: aqueous hydrogen peroxide solution = 1:30:20:5, and reacted at 60°C for 3 hours.

[0099] The reagents used in this test example are all commercially available chemically pure reagents. The concentration of each substance after the reaction is measured by an Agilent 6890N gas chromatograph. The analytical chromatographic column used is a capillary column (30 m×0.25 mm) HP-1.

[0100] The raw material conversion rate and target product selectivity in the examples and comparative examples were calculated according to the following formulas (1) and (2), respectively:

[0101]

[0102]

[0103] The test results are shown in Table 1.

[0104] Table 1

[0105]

[0106]

[0107] According to the test results in Table 1, it can be seen that the reactive centers of the heteroatom molecular sieve prepared by the preparation method provided by the present disclosure are highly accessible, have good catalytic reaction activity and activity stability, and possess high selectivity for the target product.

[0108] It can be seen from the test results of Examples 1 to 4 that when the preparation method, the order of adding the components, the molar ratio of the components, and the particle size of the graphene powder are all within the specified range of the present disclosure, the performance of the product prepared by the present disclosure can be further improved; it can be seen from the test results of Examples 5 to 7 that when the particle size of the graphene powder, the reaction parameters and conditions, and the mixing order of the components are controlled within the preferred range of the present disclosure, the conversion rate of the heteroatom molecular sieve prepared by the present disclosure to phenol can be further improved, so that the heteroatom molecular sieve has better catalytic reaction activity, activity stability and higher target product selectivity.

[0109] From the test results of Comparative Examples 1 to 6, it can be seen that since no graphene powder is added during the preparation process of Comparative Example 1, the heteroatom oxides produced during the preparation process of the heteroatom molecular sieve cannot be effectively suppressed, resulting in poor accessibility of the reactive centers of the prepared heteroatom molecular sieve, and the diffusion rate of the materials in the catalytic reaction of the heteroatom molecular sieve is reduced, so that the reaction activity, activity stability and selectivity of the heteroatom molecular sieve to the target product are all worse than those of Examples 1 to 7; since the graphene powder used in Comparative Examples 2 to 3 is prepared by an oxidation-reduction method, the graphene powder used in Comparative Example 4 is The graphene powder used is prepared by solid-phase intercalation exfoliation method, so that the particle size distribution and layer number distribution of the prepared heteroatom molecular sieve are uneven, and the formation of heteroatom oxide crystal phase cannot be effectively suppressed, resulting in poor reaction activity, activity stability and selectivity for target products of the heteroatom molecular sieve; since the graphene powder is replaced by carbon nanotubes in Comparative Example 5, the prepared heteroatom molecular sieve cannot suppress the formation of heteroatom oxide crystal phase, resulting in the conversion rate of phenol and the ratio of hydroquinone to ortho-phenol of the heteroatom molecular sieve being significantly worse than those of the embodiments of the present disclosure; Figure 1As shown, due to the addition of graphene powder after the hydrolysis treatment in Comparative Example 6, the prepared molecular sieve DB6 shows a characteristic peak of heteroatom oxide at around 330 nm compared with the molecular sieve A1 prepared in Example 1, and the absorption peak intensity generated at around 210 nm is higher, resulting in the inability to effectively disperse the titanium species and effectively combine with the silicon species during the preparation process of the heteroatom molecular sieve, so that the heteroatom oxide crystal phase cannot be effectively suppressed, and the reaction activity, activity stability and target product selectivity of the heteroatom molecular sieve are poor.

[0110] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0111] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0112] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a heteroatom molecular sieve, wherein: The method includes: S1: mixing a silicon source, a heteroatom source, an organic template, graphene powder and water at a first temperature to obtain a mixed slurry; S2 hydrolyzing the mixed slurry at a second temperature to obtain a hydrolyzed solution; S3: subjecting the hydrolyzed solution to a hydrothermal reaction, and after solid-liquid separation, calcining the recovered solid phase product; Wherein, the graphene powder is prepared by a supercritical carbon dioxide exfoliation method, and the second temperature is higher than the first temperature.

2. The method according to claim 1, wherein: The graphene powder has a D50 particle size of 0.2 to 5 μm, a flake diameter of 1 to 2000 nm, a layer number of less than 10 layers, and a specific surface area of ​​100 to 800 m 2 / g.

3. The method according to claim 1, wherein: The molar ratio of the silicon source calculated as SiO2, the heteroatom source calculated as heteroatom elements, the graphene powder calculated as carbon element, the organic template calculated as nitrogen element and water is 100: (0.1-5): (0.01-2): (5-50): (800-10000).

4. The method according to claim 1, wherein: In step S1, the silicon source is selected from an organic silicon source and / or an inorganic silicon source. Preferably, the organic silicon source is selected from one or more of methyl silicate, ethyl silicate, propyl silicate and butyl silicate; preferably, the inorganic silicon source is selected from one or more of methyl silane, ethyl silane and propyl silane; The heteroatom source is selected from one or more of a titanium source, an iron source, a vanadium source and a tin source. Preferably, the heteroatom source is selected from one or more of compounds containing titanium, iron, vanadium and tin; The organic template is selected from one or more of urea, quaternary ammonium base compounds, fatty amine compounds and alcohol amine compounds.

5. The method according to claim 1, wherein: Step S1 also includes: a. mixing a silicon source and a heteroatom source to obtain a first mixed material; b. mixing the organic template, graphene powder and optional water to obtain a second mixed material; c. Mixing the first mixed material with the second mixed material to obtain the mixed slurry.

6. The method according to claim 1, wherein: In step S1, the first temperature is 20 to 60° C., and the mixing time is 0.1 to 6 hours; In step S2, the second temperature is 70 to 100° C., and the stirring time of the hydrolysis treatment is 3 to 24 hours; Wherein, the temperature difference between the second temperature and the first temperature is 10 to 80°C; In step S3, the conditions of the hydrothermal reaction include: being carried out under autogenous pressure, the hydrothermal reaction temperature is 110-200° C., and the hydrothermal reaction time is 6-96 hours; the conditions of the calcination include: the calcination temperature is 400-800° C., and the calcination time is 1-12 hours.

7. The heteroatom molecular sieve prepared by the method according to any one of claims 1 to 6.

8. The heteroatom molecular sieve according to claim 7, wherein: The molar ratio of the heteroatom element to the silicon element in the heteroatom molecular sieve is (0.1-8):

100.

9. The heteroatom molecular sieve according to claim 7, wherein: The BET specific surface area of ​​the heteroatom molecular sieve is 300 to 700 cm 2 / g; total pore volume is 0.3~0.8cm 3 / g; mesopore volume is 0.2~0.6cm 3 / g; the ratio of mesopore volume to total pore volume is (0.5-0.9):1; the average particle size of the heteroatom molecular sieve is 0.1-1 μm.

10. Use of the heteroatom molecular sieve according to any one of claims 7 to 9 in the hydroxylation reaction of phenol.

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