A method for preparing hydroxycarboxylic acid

Abstract

The present invention relates to a method for preparing a hydroxycarboxylic acid, comprising: contacting a cycloolefin with an oxidant and conducting an oxidation reaction in the presence of a catalyst, wherein the catalyst comprises a silicon-containing catalytic material; the silicon-containing catalytic material is prepared by a method comprising the following steps: mixing a nitrogen-containing carbon compound with a solution containing a silicon source and an acid, subjecting the resulting mixture to a hydrothermal treatment, and then removing a solid to obtain the silicon-containing catalytic material; wherein the nitrogen content of the nitrogen-containing carbon compound is 35-70% by weight, based on the dry weight of the nitrogen-containing carbon compound. The method of the present invention can prepare the hydroxycarboxylic acid under mild conditions and has high feedstock conversion and hydroxycarboxylic acid selectivity.

Description

Technical Field

[0001] The present invention relates to a method for preparing hydroxycarboxylic acid. Background Art

[0002] Hydroxycarboxylic acids, due to their active chemical properties and the ability to participate in both hydroxyl and carboxyl reactions, are widely used in organic chemical synthesis. However, existing processes for preparing hydroxycarboxylic acids, such as those using nitric acid oxidation, are subject to severe corrosion and pollution. Therefore, the development of new environmentally friendly methods for preparing hydroxycarboxylic acids is urgently needed. Summary of the Invention

[0003] The object of the present invention is to provide a method for preparing hydroxycarboxylic acid, which has high raw material conversion rate and high selectivity of hydroxycarboxylic acid.

[0004] To achieve the above object, the present invention provides a method for preparing hydroxycarboxylic acid, comprising: contacting a cycloolefin with an oxidant and performing an oxidation reaction in the presence of a catalyst, wherein the catalyst comprises a silicon-containing catalytic material;

[0005] The silicon-containing catalytic material is prepared by a method comprising the following steps:

[0006] A nitrogen-containing carbon compound is mixed with a solution containing a silicon source and an acid, the obtained mixture is subjected to hydrothermal treatment, and the solid is taken out to obtain the silicon-containing catalytic material; wherein, based on the dry weight of the nitrogen-containing carbon compound, the nitrogen content of the nitrogen-containing carbon compound is 35-70% by weight, and based on the dry weight of the silicon-containing catalytic material, the silicon content in the silicon-containing catalytic material calculated as silicon oxide is 1-50% by weight.

[0007] Optionally, the silicon content of the silicon-containing catalytic material calculated as silicon oxide is 2-25% by weight, with the remainder being nitrogen and carbon.

[0008] Optionally, the weight ratio of the nitrogen-containing carbon compound to the acid solution containing the silicon source is 1:(0.5-100), preferably 1:(1-50), and more preferably 1:(2-20).

[0009] Optionally, the content of the silicon source in the solution containing the silicon source and the acid is 0.1-40 wt %, preferably 1-30 wt %, more preferably 5-20 wt %; the content of the acid is 0.1-30 wt %, preferably 1-20 wt %, more preferably 2-15 wt %;

[0010] The silicon source is selected from one or more of methyl silicate, ethyl silicate, propyl silicate, butyl silicate, methylsilane, ethylsilane and propylsilane; and the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid and acetic acid.

[0011] Optionally, the nitrogen-containing carbon compound is prepared by a method comprising the following steps: calcining a precursor of the nitrogen-containing carbon compound at 400-800° C. for 1-10 hours under an inert atmosphere; wherein the precursor of the nitrogen-containing carbon compound is selected from melamine and / or melamine.

[0012] Optionally, the average particle size of the silicon-containing catalytic material is 10-1000 nm, preferably 20-500 nm;

[0013] The weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 2-60%, preferably 5-50%, and more preferably 10-30% of the total weight of the silicon-containing catalytic material.

[0014] Optionally, the conditions of the hydrothermal treatment include: a temperature of 120-300° C. and a time of 0.1-24 hours.

[0015] Optionally, the oxidation reaction conditions include: temperature of 60-150°C, pressure of 0.01-5 MPa, time of 1-24 hours, and weight hourly space velocity of cycloolefin of 0.1-100h -1 ;

[0016] Preferably, the temperature is 80-120°C, the pressure is 0.2-2 MPa, the time is 2-12 hours, and the weight hourly space velocity of the cycloolefin is 0.2-50h -1 .

[0017] Optionally, based on 100 mL of the cycloolefin, the amount of the catalyst is 5-500 mg, preferably 10-200 mg;

[0018] The cycloolefin is selected from substituted or unsubstituted cycloolefins having 5 to 10 ring carbon atoms; the substituent of the substituted cycloolefin is selected from one or more of deuterium, a halogen group, and an alkyl group having 1 to 5 carbon atoms; optionally, the cycloolefin includes one or more of cyclohexene, cyclopentene, cyclooctene, cycloheptene, methylcyclopentene, methylcyclohexene, halogenated cyclopentene, and halogenated cyclohexene;

[0019] The oxidant is a gas containing oxygen, and the molar ratio of the cycloolefin to the oxygen in the oxygen-containing gas is 1:(2-20), preferably 1:(4-10).

[0020] Optionally, the method comprises: contacting the cyclic olefin with an oxidant in the presence of a solvent and the catalyst to carry out an oxidation reaction;

[0021] The solvent is deionized water, a C1-C6 alcohol, a C3-C8 ketone or a C2-C6 nitrile, or a combination of two or three thereof;

[0022] The weight ratio of the cycloolefin to the solvent is 1:(0.1-100), preferably 1:(1-50).

[0023] Through the above technical solution, the method of the present invention can prepare hydroxycarboxylic acid under mild conditions, and has high raw material conversion rate and selectivity for hydroxycarboxylic acid.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0025] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] The present invention provides a method for preparing hydroxycarboxylic acid, comprising: contacting a cycloolefin with an oxidant and conducting an oxidation reaction in the presence of a catalyst, wherein the catalyst comprises a silicon-containing catalytic material; the silicon-containing catalytic material is prepared by a method comprising the following steps: mixing a nitrogen-containing carbon compound with a solution containing a silicon source and an acid, subjecting the obtained mixture to a hydrothermal treatment, and then removing a solid to obtain the silicon-containing catalytic material; wherein, based on the dry weight of the nitrogen-containing carbon compound, the nitrogen content of the nitrogen-containing carbon compound is 35-70% by weight; and based on the dry weight of the silicon-containing catalytic material, the silicon content of the silicon-containing catalytic material, calculated as silicon oxide, is 1-50% by weight.

[0027] In a specific embodiment of the present invention, the silicon content of the silicon-containing catalytic material calculated as silicon oxide is 2-25% by weight, more preferably 5-20% by weight, with the remainder being nitrogen and carbon.

[0028] The catalyst used in the method of the present invention contains a silicon-containing catalytic material prepared by a specific method, can prepare hydroxycarboxylic acid under mild conditions, and has a high raw material conversion rate and selectivity for the target product hydroxycarboxylic acid.

[0029] In a specific embodiment of the present invention, the method for removing the solid is not particularly limited, and methods such as filtration and centrifugation can be used. Preferably, the removed solid is dried. Drying conditions may include: a temperature of 60-200°C for 1-12 hours; preferably, a temperature of 80-180°C for 2-10 hours. Drying is a chemical operation well known to those skilled in the art, and can be performed, for example, in a constant temperature drying oven or a muffle furnace.

[0030] In a specific embodiment of the present invention, the nitrogen content of the nitrogen-containing carbon compound is 40-65% by weight. The nitrogen content of the nitrogen-containing carbon compound in the present invention can be detected by XPS method.

[0031] In a specific embodiment of the present invention, the weight ratio of the nitrogen-containing carbon compound to the acid solution containing the silicon source can vary within a large range, for example, it can be 1:(0.5-100), preferably 1:(1-50), and more preferably 1:(2-20).

[0032] According to the present invention, the content of the silicon source and the acid in the solution containing the silicon source and the acid can vary within a wide range. In one embodiment of the present invention, the content of the silicon source in the solution containing the silicon source and the acid is 0.1-40% by weight, preferably 1-30% by weight, and more preferably 5-20% by weight; the content of the acid is 0.1-30% by weight, preferably 1-20% by weight, and more preferably 2-15% by weight. When the silicon-containing catalytic material is prepared using a solution containing the silicon source and the acid within the above content ranges, the reaction raw material conversion rate and target product selectivity can be further improved.

[0033] According to the present invention, the silicon source can be selected from organosilanes and / or inorganic silanes. The organosilanes may include, but are not limited to, one or more of methyl silicate, ethyl silicate, propyl silicate, and butyl silicate. The inorganic silanes may include, but are not limited to, one or more of methyl silane, ethyl silane, and propyl silane. The acid can be selected from inorganic and / or organic acids, for example, including, but not limited to, one or more of hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid, and acetic acid. In a preferred embodiment of the present invention, the solution containing the silicon source and the acid is an aqueous solution containing the silicon source and the acid.

[0034] According to the present invention, the average particle size of the silicon-containing catalytic material can vary over a wide range, for example, from 10 to 1000 nm, preferably from 20 to 500 nm. In the present invention, "particle size" refers to the maximum three-dimensional length of the particle, that is, the distance between the two points on the particle with the largest distance between them. The average particle size in the present invention can be obtained by measuring the silicon-containing catalytic material using a transmission electron microscope and calculating the average particle size of 100 randomly selected particles. The inventors of the present application unexpectedly discovered that when the weight of the silicon-containing catalytic material with a particle size of 20 to 100 nm accounts for 2 to 60%, preferably 5 to 50%, and more preferably 10 to 30%, of the total weight of the silicon-containing catalytic material, the silicon-containing catalytic material within the above content range has better catalytic performance in cycloolefin oxidation. The silicon-containing catalytic material used in the method of the present invention has a suitable particle size and excellent catalytic performance. Using it to catalyze the oxidation reaction of cycloolefins can improve the conversion rate of the raw material and the selectivity for the target product.

[0035] According to the present invention, the nitrogen-containing carbon compound is a precursor of the nitrogen-containing carbon compound after calcination. In a specific embodiment of the present invention, the nitrogen-containing carbon compound is prepared by a method comprising the following steps: calcining the precursor of the nitrogen-containing carbon compound at 400-800°C for 1-10 hours under an inert atmosphere. Preferably, the precursor of the nitrogen-containing carbon compound is placed in a sealed heat-resistant container and calcined at 450-740°C under an inert atmosphere. The sealed heat-resistant container can be conventionally used by those skilled in the art, for example, it can be a quartz crucible (high-temperature vacuum-sealed oil ester) or a stainless steel reactor. There is no specific restriction on the type of inert gas in the inert atmosphere of calcination, and it can be argon, helium, nitrogen, etc. The inert gas content in the inert atmosphere is greater than 85% by volume, preferably greater than 90% by volume. The nitrogen-containing carbon compound prepared by the above method can be used in the oxidation process of cycloolefins to further improve the conversion rate of the raw materials and the selectivity of the target product. According to the present invention, the nitrogen content of the nitrogen-containing carbon compound precursor can be 35-70%, preferably 40-65%, and can include, but is not limited to, melamine and / or tricyanamide. Calcination is a technique well known to those skilled in the art, and can be performed, for example, in a muffle furnace or a tube furnace. The present invention does not impose any specific restrictions on the calcination atmosphere, and can, for example, be air or an inert atmosphere.

[0036] According to the present invention, hydrothermal treatment is well known to those skilled in the art. In one embodiment of the present invention, the hydrothermal treatment conditions include: a temperature of 120-300°C for 0.1-24 hours; preferably, a temperature of 150-250°C for 5-18 hours. The present invention does not impose any specific restrictions on the pressure of the hydrothermal treatment, which can be either autogenous pressure or applied pressure, and is preferably carried out under autogenous pressure.

[0037] According to the present invention, the catalyst may also contain other materials commonly used by those skilled in the art for cycloolefin oxidation, such as one or more of a transition metal oxide, a noble metal, and a heteroatom molecular sieve. In a preferred embodiment, the catalyst is 100% silicon-containing catalytic material.

[0038] In one embodiment of the present invention, the oxidation reaction conditions include: temperature of 60-150°C, pressure of 0.01-5 MPa, time of 1-24 hours, and weight hourly space velocity of cycloolefin of 0.1-100h -1 Preferably, the temperature is 80-120 ° C, the pressure is 0.2-2MPa, the time is 2-12 hours, and the weight hourly space velocity of the cycloolefin is 0.2-50h -1 In a preferred embodiment, the oxidation reaction is carried out under stirring conditions.

[0039] In a specific embodiment of the present invention, based on 100 mL of the cycloolefin, the amount of the catalyst used is 5-500 mg, preferably 10-200 mg.

[0040] According to the present invention, the cycloolefin is selected from substituted or unsubstituted cycloolefins having 5-10 ring carbon atoms; the substituent of the substituted cycloolefin is selected from one or more of deuterium, a halogen group and an alkyl group having 1-5 carbon atoms; in a specific embodiment, the cycloolefin may include one or more of cyclohexene, cyclopentene, cyclooctene, cycloheptene, methylcyclopentene, methylcyclohexene, halogenated cyclopentene and halogenated cyclohexene.

[0041] In a specific embodiment of the present invention, the oxidant is a gas containing oxygen, such as air or oxygen, and the molar ratio of the cycloolefin to the oxygen in the oxygen-containing gas is 1:(2-20), preferably 1:(4-10).

[0042] To improve the uniformity of the reaction materials, in one embodiment, the cycloolefin oxidation method may include contacting the cycloolefin and an oxidant in the presence of a solvent and a catalyst to carry out an oxidation reaction. The solvent may be any liquid that can dissolve the cycloolefin and the oxidant, promote mixing thereof, and promote dissolution of the target product, such as an organic solvent and / or deionized water. The organic solvent is well known to those skilled in the art, and may be, for example, a C1-C6 alcohol, a C3-C8 ketone, or a C2-C6 nitrile, or a combination of two or three thereof. Preferably, the solvent is one or more of methanol, acetone, and deionized water. The weight ratio of the cycloolefin to the solvent may vary over a wide range, such as 1:(0.1-100), preferably 1:(1-50), and more preferably 1:(5-25).

[0043] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto.

[0044] In the preparation example, the average particle size (particle diameter) of the sample was obtained by TECHNAIG 2 The measurement was carried out using an F20 (200kv) transmission electron microscope. The test conditions were as follows: an accelerating voltage of 20kV, sample preparation by the suspension method, the sample was placed in a 2mL glass bottle, dispersed with anhydrous ethanol, and shaken evenly. A drop was taken with a dropper and dropped onto a sample net with a diameter of 3mm. After drying, the sample was placed in a sample injector and then inserted into an electron microscope for observation. 100 particles were randomly selected for particle size statistics.

[0045] The proportion of particles with a size of 20-100 nm in the sample was calculated by using a membrane separation device (model BONA-GM-05) produced by Jinan Bona Biotechnology Co., Ltd. to separate particles with a size range of 20-100 nm. The weight proportion of particles with a size range of 20-100 nm was then calculated based on the weight of the separated particles with a size range of 20-100 nm and the total weight.

[0046] The preparation examples are used to illustrate the silicon-containing catalytic materials prepared by the method of the present invention, and the preparation comparative examples are used to illustrate the samples prepared by the method in the prior art.

[0047] Preparation Example 1

[0048] In a nitrogen atmosphere, 50 g of melamine was placed in a 100 mL crucible, covered and sealed with vacuum sealing ester, and then the crucible was placed in a muffle furnace at 450°C and calcined for 8 hours. After natural cooling at room temperature (20°C, the same below), a nitrogen-carbon compound (nitrogen content of 56 wt%) was obtained; the obtained nitrogen-carbon compound was then added to a phosphoric acid aqueous solution containing ethyl silicate (the concentration of ethyl silicate was 5 wt%, and the concentration of phosphoric acid was 5 wt%) and mixed. The weight ratio of the nitrogen-carbon compound to the phosphoric acid aqueous solution of ethyl silicate was 1:6. The mixture was hydrothermally treated at 200°C for 12 hours, taken out for washing, and then dried at 120°C for 6 hours to obtain silicon-containing catalytic material A1.

[0049] The silicon content of the silicon-containing catalytic material A1 calculated as silicon oxide is 11 wt %, and the average particle size is 220 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 30% of the total weight.

[0050] Preparation Example 2

[0051] In a nitrogen atmosphere, 40 g of melamine was placed in a 100 mL crucible, covered and sealed with vacuum sealing ester, and the crucible was placed in a muffle furnace at 550°C and calcined for 5 hours. After natural cooling at room temperature, a nitrogen-containing carbon compound (nitrogen content of 59 weight%) was obtained; then the nitrogen-containing carbon compound was added to a phosphoric acid aqueous solution containing ethyl silicate (the concentration of ethyl silicate was 10 weight%, and the concentration of phosphoric acid was 5 weight%) and mixed. The weight ratio of the nitrogen-containing carbon compound to the phosphoric acid aqueous solution containing ethyl silicate was 1:10. The mixture was hydrothermally treated at 150°C for 12 hours, taken out for washing, and then dried at 100°C for 6 hours to obtain silicon-containing catalytic material A2.

[0052] The silicon content of the silicon-containing catalytic material A2 calculated as silicon oxide is 23% by weight, and the average particle size is 150 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 16% of the total weight.

[0053] Preparation Example 3

[0054] In a nitrogen atmosphere, 100 g of melamine was placed in a 200 mL crucible, covered and sealed with vacuum sealing ester, and the crucible was placed in a muffle furnace at 420°C and calcined for 4 hours. After natural cooling at room temperature, a nitrogen-containing carbon compound (nitrogen content of 48 wt%) was obtained; then the nitrogen-containing carbon compound was added to a phosphoric acid aqueous solution containing ethyl silicate (the concentration of ethyl silicate was 5 wt%, and the concentration of phosphoric acid was 5 wt%) and mixed. The weight ratio of the nitrogen-containing carbon compound to the phosphoric acid aqueous solution of ethyl silicate was 1:20. The mixture was hydrothermally treated at 100°C for 24 hours, taken out and washed, and then dried at 120°C for 6 hours to obtain silicon-containing catalytic material A3.

[0055] The silicon content of the silicon-containing catalytic material A3 calculated as silicon oxide is 11 wt %, and the average particle size is 90 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 9% of the total weight.

[0056] Preparation Example 4

[0057] In a nitrogen atmosphere, 60 g of melamine was placed in a 100 mL crucible, covered and sealed with vacuum sealing ester, and the crucible was placed in a muffle furnace at 650°C and calcined for 2 hours. After natural cooling at room temperature, a nitrogen-containing carbon compound (nitrogen content of 66 wt%) was obtained; then the nitrogen-containing carbon compound was added to an aqueous sulfuric acid solution of ethyl silicate (the concentration of ethyl silicate was 0.5 wt%, and the concentration of sulfuric acid was 5 wt%) and mixed. The weight ratio of the nitrogen-containing carbon compound to the aqueous sulfuric acid solution of ethyl silicate was 1:15. The mixture was hydrothermally treated at 280°C for 6 hours, taken out and washed, and then dried at 150°C for 6 hours to obtain a silicon-containing catalytic material A4.

[0058] The silicon content of the silicon-containing catalytic material A4 calculated as silicon oxide is 8% by weight, and the average particle size is 50 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 5% of the total weight.

[0059] Preparation Example 5

[0060] In a nitrogen atmosphere, 20 g of melamine was placed in a crucible and sealed with a lid. The crucible was placed in a muffle furnace at 400°C and calcined for 6 hours. After natural cooling at room temperature, a nitrogen-containing carbon compound (nitrogen content of 43 weight%) was obtained; then the nitrogen-containing carbon compound was added to an aqueous phosphoric acid solution of ethyl silicate (the concentration of ethyl silicate was 8 weight%, and the concentration of phosphoric acid was 5 weight%) and mixed. The weight ratio of the nitrogen-containing carbon compound to the aqueous phosphoric acid solution of ethyl silicate was 1:25. The mixture was hydrothermally treated at 150°C for 18 hours, taken out for washing, and then dried at 120°C for 4 hours to obtain silicon-containing catalytic material A5.

[0061] The silicon content of the silicon-containing catalytic material A5 calculated as silicon oxide is 28% by weight, and the average particle size is 100 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 23% of the total weight.

[0062] Preparation Example 6

[0063] The silicon-containing catalytic material A6 was prepared by the same method as in Example 1, except that the weight ratio of the nitrogen-containing carbon compound to the phosphoric acid aqueous solution of ethyl silicate was 1:30.

[0064] The silicon content of the prepared silicon-containing catalytic material A6 calculated as silicon oxide was 21% by weight, and the average particle size was 290 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounted for 60% of the total weight.

[0065] Preparation Example 7

[0066] The silicon-containing catalytic material A7 was prepared by the same method as in Example 1, except that the concentration of ethyl silicate in the phosphoric acid aqueous solution containing ethyl silicate was 4 wt % and the concentration of phosphoric acid was 21 wt %.

[0067] The silicon content of the prepared silicon-containing catalytic material A7 calculated as silicon oxide was 5% by weight, and the average particle size was 100 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounted for 40% of the total weight.

[0068] Preparation Example 8

[0069] The silicon-containing catalytic material A8 was prepared by the same method as in Example 1, with the only difference being that 50 g of urea was placed in a 100 mL crucible, covered and sealed with vacuum sealing ester, and then the crucible was placed in a muffle furnace at 350°C and calcined for 8 hours. After naturally cooling to room temperature, a nitrogen-containing carbon compound (nitrogen content of 40 wt%) was obtained.

[0070] The silicon content of the prepared silicon-containing catalytic material A8 calculated as silicon oxide was 25% by weight, and the average particle size was 180 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounted for 42% of the total weight.

[0071] Preparation Comparative Example 1

[0072] The silicon-containing catalytic material a was prepared by the same method as in Example 1, except that the nitrogen-carbon compound was added to a mixture of ethyl silicate and water (the concentration of ethyl silicate was 5 wt%) and then the mixture was hydrothermally treated.

[0073] The silicon content of the silicon-containing catalytic material a calculated as silicon oxide is 55% by weight, and the average particle size is 420 nm, wherein the weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 1% of the total weight.

[0074] The following examples illustrate the cyclic olefin oxidation process of the present invention.

[0075] In the following examples and comparative examples, gas chromatography (GC: Agilent, 7890A) and gas chromatography-mass spectrometry (GC-MS: Thermo Fisher Trace ISQ) were used to analyze the oxidation products. The results are listed in Table 1.

[0076] The following formulas were used to calculate the conversion of raw materials and the selectivity of target products:

[0077] Cycloolefin conversion % = (molar amount of cycloolefin added before the reaction - molar amount of cycloolefin remaining after the reaction) / molar amount of cycloolefin added before the reaction × 100%;

[0078] Target product selectivity % = (molar amount of target product generated after the reaction) / molar amount of cycloolefin added before the reaction × 100%.

[0079] Example 1

[0080] 80 mL of cyclohexene and 0.25 g of silicon-containing catalytic material A1 as catalysts were added to a 250 mL autoclave to form a reaction mass, which was then sealed. Oxygen (molar ratio of oxygen to cyclohexene was 8:1) was then introduced. The mixture was stirred at 120° C. and 2 MPa (when the required oxygen was less than the reaction pressure after being introduced at one time, nitrogen was used as a balance gas to allow the reaction to reach and maintain the reaction pressure; when the required oxygen was greater than the reaction pressure after being introduced at one time, oxygen was continuously introduced to maintain the oxygen pressure at the reaction pressure. As the reaction proceeded, oxygen was continuously introduced during the reaction. If all the required oxygen was introduced, nitrogen was introduced as a balance gas to allow the reaction to continue under the reaction pressure; the same below). After the reaction was stirred for 4 hours, the catalyst was separated by centrifugation and filtration.

[0081] Examples 2-8

[0082] Cyclohexene oxidation was carried out according to the method of Example 1, except that the same amount of silicon-containing catalytic materials A2-A8 were used instead of A1 as the catalyst.

[0083] Example 9

[0084] Cyclohexene is fed into the reaction zone from the feed port at the top of the fixed bed reactor, and air is fed into the reaction zone from the feed port at the bottom of the fixed bed reactor to contact with the silicon-containing catalytic material A1 as a catalyst. The molar ratio of cyclohexene to oxygen in the air is 1:8, the reaction temperature is 90°C, the pressure is 1.5 MPa, and the weight hourly space velocity of cyclohexene is 1h -1 The reaction was continued for 1 hour and the resulting reaction mixture was analyzed by gas chromatography.

[0085] Example 10

[0086] Cyclohexene and methanol as a solvent are mixed to form a liquid mixture. This liquid mixture is then fed into the reaction zone from the feed port at the top of the fixed bed reactor, and oxygen is fed from the feed port at the bottom of the fixed bed reactor to contact the silicon-containing catalytic material A1 as a catalyst. The molar ratio of cyclohexene to oxygen is 1:4, and the weight ratio of cyclohexene to methanol is 1:10. The reaction temperature is 50°C, the pressure is 0.8 MPa, and the weight hourly space velocity of cyclohexene is 0.2 h -1 The reaction was continued for 2 hours and the resulting reaction mixture was analyzed by gas chromatography.

[0087] Example 11

[0088] Cyclohexene is fed into the reaction zone from the feed port at the top of the fixed bed reactor, and air is fed into the reaction zone from the feed port at the bottom of the fixed bed reactor to contact with the silicon-containing catalytic material A1 as a catalyst. The molar ratio of cyclohexene to oxygen in the air is 1:8, the reaction temperature is 90°C, the pressure is 1.5 MPa, and the weight hourly space velocity of cyclohexene is 1h -1 The reaction was continued for 1 hour and the resulting reaction mixture was analyzed by gas chromatography.

[0089] Comparative Example 1

[0090] Cyclohexene was oxidized according to the method of Example 1, except that no silicon-containing catalytic material was added as a catalyst.

[0091] Comparative Example 2

[0092] Cyclohexene was oxidized according to the method of Example 1, except that the silicon-containing catalytic material a prepared in Comparative Example 1 was used as the catalyst.

[0093] Table 1

[0094] Catalyst No. Cycloolefin conversion, % Hydroxycaproic acid selectivity, % Example 1 A1 65 92 Example 2 A2 51 90 Example 3 A3 54 89 Example 4 A4 49 84 Example 5 A5 52 83 Example 6 A6 50 81 Example 7 A7 53 86 Example 8 A8 51 83 Example 9 A1 50 84 Example 10 A1 31 76 Example 11 A1 44 82 Comparative Example 1 / 30 34 Comparative Example 2 a 45 41

[0095] It can be seen from the above that the method of the present invention has higher raw material conversion rate and selectivity of the target product hydroxycaproic acid.

[0096] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0097] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0098] In addition, the 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 hydroxycarboxylic acid, the method comprising: contacting the cyclic olefin with an oxidant and performing an oxidation reaction in the presence of a catalyst, wherein the catalyst comprises a silicon-containing catalytic material; The silicon-containing catalytic material is prepared by a method comprising the following steps: The silicon-containing catalytic material is obtained by mixing a nitrogen-containing carbon compound with a solution containing a silicon source and an acid, subjecting the obtained mixture to a hydrothermal treatment, and then removing the solid. The nitrogen content of the nitrogen-containing carbon compound is 35-70% by weight based on the dry weight of the nitrogen-containing carbon compound; and the silicon content of the silicon-containing catalytic material, calculated as silicon oxide, is 1-50% by weight based on the dry weight of the silicon-containing catalytic material. The cycloolefin is selected from substituted or unsubstituted cycloolefins having 5 to 10 ring carbon atoms; the substituent of the substituted cycloolefin is selected from one or more of deuterium, a halogen group, and an alkyl group having 1 to 5 carbon atoms; The silicon source is selected from one or more of methyl silicate, ethyl silicate, propyl silicate, butyl silicate, methylsilane, ethylsilane and propylsilane; The acid is selected from one or more of phosphoric acid, hydrochloric acid, sulfuric acid, nitric acid, hydrobromic acid and acetic acid.

2. The method according to claim 1, wherein The silicon-containing catalytic material has a silicon content of 2-25% by weight calculated as silicon oxide, with the remainder being nitrogen and carbon.

3. The method according to claim 1, wherein The weight ratio of the nitrogen-containing carbon compound to the acid solution containing the silicon source is 1:(0.5-100).

4. The method according to claim 3, wherein: The weight ratio of the nitrogen-containing carbon compound to the acid solution containing the silicon source is 1:(1-50).

5. The method according to claim 3, wherein: The weight ratio of the nitrogen-containing carbon compound to the acid solution containing the silicon source is 1:(2-20).

6. The method according to claim 1, wherein In the solution containing a silicon source and an acid, the content of the silicon source is 0.1-40% by weight; and the content of the acid is 0.1-30% by weight.

7. The method according to claim 6, wherein: In the solution containing a silicon source and an acid, the content of the silicon source is 1-30% by weight; and the content of the acid is 1-20% by weight.

8. The method according to claim 6, wherein: In the solution containing a silicon source and an acid, the content of the silicon source is 5-20% by weight; and the content of the acid is 2-15% by weight.

9. The method according to claim 1, wherein The nitrogen-containing carbon compound is prepared by a method comprising the following steps: calcining a precursor of the nitrogen-containing carbon compound at 400-800° C. for 1-10 hours under an inert atmosphere; wherein the precursor of the nitrogen-containing carbon compound is selected from melamine and / or melamine.

10. The method according to claim 1, wherein The average particle size of the silicon-containing catalytic material is 10-1000 nm; The weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 2-60% of the total weight of the silicon-containing catalytic material.

11. The method according to claim 10, wherein: The average particle size of the silicon-containing catalytic material is 20-500 nm; The weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 5-50% of the total weight of the silicon-containing catalytic material.

12. The method according to claim 10, wherein: The weight of the silicon-containing catalytic material with a particle size of 20-100 nm accounts for 10-30% of the total weight of the silicon-containing catalytic material.

13. The method according to claim 1, wherein The conditions of the hydrothermal treatment include: a temperature of 120-300° C. and a time of 0.1-24 hours.

14. The method according to claim 1, wherein The oxidation reaction conditions include: temperature of 60-150°C, pressure of 0.01-5 MPa, time of 1-24 hours, and weight hourly space velocity of cycloolefin of 0.1-100h -1 .

15. The method according to claim 14, wherein The oxidation reaction conditions include: temperature of 80-120°C, pressure of 0.2-2 MPa, time of 2-12 hours, weight hourly space velocity of cycloolefin of 0.2-50h -1 .

16. The method according to claim 1, wherein Based on 100 mL of the cycloolefin, the amount of the catalyst used is 5-500 mg; The cycloolefins include one or more of cyclohexene, cyclopentene, cyclooctene, cycloheptene, methylcyclopentene, methylcyclohexene, halogenated cyclopentene and halogenated cyclohexene; The oxidant is a gas containing oxygen, and the molar ratio of the cycloolefin to the oxygen in the oxygen-containing gas is 1:(2-20).

17. The method according to claim 16, wherein Based on 100 mL of the cycloolefin, the amount of the catalyst used is 10-200 mg; The oxidant is a gas containing oxygen, and the molar ratio of the cycloolefin to the oxygen in the oxygen-containing gas is 1:(4-10).

18. The method according to claim 1, wherein The method comprises: contacting a cyclic olefin with an oxidant in the presence of a solvent and the catalyst to carry out an oxidation reaction; The solvent is deionized water, a C1-C6 alcohol, a C3-C8 ketone or a C2-C6 nitrile, or a combination of two or three thereof; The weight ratio of the cycloolefin to the solvent is 1:(0.1-100).

19. The method according to claim 18, wherein The weight ratio of the cycloolefin to the solvent is 1:(1-50).