Titanium complex catalyst, preparation method thereof and application of titanium complex catalyst in anisole hydroxylation

Abstract

The invention relates to a titanium complex catalyst, a preparation method of the titanium complex catalyst and application of the titanium complex catalyst in hydroxylation of anisole. Anisole and hydrogen peroxide react under catalysis of the titanium complex catalyst to obtain o-hydroxyanisole and p-hydroxyanisole. The invention provides a novel catalyst, active titanium and reactants are in full contact, and higher reaction activity is achieved; the catalyst has a certain space effect, can achieve a shape-selective catalysis effect, can generate more para-products, and improves the para-ortho ratio of hydroxyanisole.

Description

Technical Field

[0001] The present invention belongs to the field of catalyst preparation, and particularly relates to a titanium complex catalyst, a preparation method thereof, and an application thereof in the hydroxylation of anisole. Background Art

[0002] p-Hydroxyanisole, also known as p-methoxyphenol, etc., abbreviated as MEHQ, is a white flaky or waxy crystal, and is an important chemical product. It can be used as a polymerization inhibitor for acrylonitrile, acrylic acid (AA), methacrylic acid (MAA) and other vinyl monomers, and can also be used as an intermediate for dyes and pesticides. o-Hydroxyanisole, also known as guaiacol, is an important intermediate in the fields of spices, medicine, pesticides, etc. Its main use is to synthesize vanillin. Currently, 90% of the commercially available vanillin is converted from guaiacol.

[0003] The anisole hydroxylation reaction uses anisole as a raw material and hydrogen peroxide as a hydroxylation reagent. Under the action of a catalyst, o-hydroxyanisole and p-hydroxyanisole can be obtained simultaneously. Foreign literature (Kuma R, et al, Microporpus andmesoporous materials, 1998, 21(4):497-504) uses titanium silicalite (TS-1) to catalyze the reaction of anisole and hydrogen peroxide. The conversion rate of hydrogen peroxide is about 40%, and the product is a mixture of o-hydroxyanisole and p-hydroxyanisole. The yield of this process is relatively low. CN105985226A discloses a method for the hydroxylation of anisole. Using hollow-structured TS-1 as a catalyst, high anisole conversion can be achieved in a relatively short time, and the p / o ratio of hydroxyanisole in the product is at a relatively high level. Patent CN 115490579B uses alkali-modified, copper- and chromium-loaded microsphere TS-1 as a catalyst. Under the conditions of below 150 °C and 0.1-5 MPa, the reaction of anisole and hydrogen peroxide can obtain hydroxyanisole products with a relatively high yield. At the same time, the catalyst can reach a service life of more than 2000 h, but the single-pass conversion rate of anisole in this technology is relatively low, a large amount of anisole needs to be recycled, and the energy consumption is large.

[0004] Existing anisole hydroxylation technologies all use TS-1 as a catalyst. TS-1 catalyst is commonly used in the hydroxylation reaction of phenol. Anisole is more difficult to hydroxylate than phenol. Coupled with the fact that this reaction is a solid-liquid two-phase reaction with low activity, the process conditions of this reaction are relatively harsh and the requirements for the catalyst are higher. In addition, the synthesis process of TS-1 is difficult, the production cost is high, and it is easy to deactivate, and it needs to be regenerated regularly, and the operation is cumbersome.

[0005] Developing a titanium complex catalyst with high catalytic activity for anisole hydroxylation, which is not easy to deactivate, a preparation method thereof, and an application thereof in anisole hydroxylation has very positive significance. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a new titanium complex catalyst, a preparation method thereof, and an application thereof in the hydroxylation of anisole. The catalyst of the present invention has higher reactivity towards anisole, which is beneficial to improving the para-to-ortho ratio of hydroxyanisole.

[0007] In order to achieve the above technical object, the present invention provides a titanium complex catalyst, the structure of which is shown as follows:

[0008]

[0009] In the formula, R represents hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0010] The present invention also provides a preparation method of the titanium complex catalyst, which includes the following steps:

[0011] (1) Under anhydrous and anaerobic conditions, aniline or its derivative reacts with 2-hydroxy-1-naphthaldehyde;

[0012] (2) Under a nitrogen atmosphere, titanium tetrachloride is added to the reaction product of step (1) for reaction to obtain a titanium complex.

[0013] The reaction route is schematically shown as follows:

[0014]

[0015] In step (1) of the present invention, the structure of the aniline or its derivative is: In the formula, R represents hydrogen or an alkyl group having 1 to 6 carbon atoms.

[0016] In the present invention, the reaction of step (1) is carried out in solvent A, and the solvent A is one or more of acetone, ethanol, toluene, DMF, DMAC, tetrahydrofuran, toluene, and is preferably ethanol and tetrahydrofuran.

[0017] In the present invention, the mass ratio of 2-hydroxy-1-naphthaldehyde to solvent A in step (1) is 1:(1 to 10), preferably 1:(3 to 8).

[0018] In step (1) of the present invention, the mass ratio of 2-hydroxy-1-naphthaldehyde to aniline or its derivative is 1:(0.2 to 1), preferably 1:(0.3 to 0.5).

[0019] In step (1) of the present invention, the reaction conditions are an anhydrous and anaerobic environment.

[0020] In step (1) of the present invention, the reaction temperature is 30°C to 100°C, and the preferred reaction temperature is 50°C to 80°C.

[0021] In step (1) of the present invention, the reaction time is 3 - 10 h, preferably 5 - 8 h.

[0022] In step (1) of the present invention, after the reaction, compound 1 is washed out by cooling. The temperature is cooled to -10 - 10 °C, and the preferred cooling temperature is 0 - 5 °C.

[0023] In step (1) of the present invention, the solid washed out by cooling is separated by filtration, and the filtered solid is washed three times with a solvent. The preferred solvent is an alkane with 6 - 10 carbon atoms.

[0024] Step (2) of the present invention can be carried out in solvent B. The solvent B includes one or more of methanol, ethanol, propanol, water, and acetone, and is preferably ethanol or methanol.

[0025] In step (2) of the present invention, the mass ratio of the reaction product of step (1) to solvent B is 1:(3 - 12), preferably 1:(4 - 10).

[0026] In step (2) of the present invention, the mass ratio of titanium tetrachloride to the reaction product of step (1) is (0.5 - 2):1, preferably (0.7 - 1.4):1.

[0027] In step (2) of the present invention, the reaction condition is under a nitrogen atmosphere.

[0028] In step (2) of the present invention, titanium tetrachloride is added at a low temperature, the temperature is -100 °C to -50 °C, and the preferred addition temperature is -78 °C. An acetone bath can be used. Preferably, carbon tetrachloride needs to be added slowly, preferably by dropwise addition. After the addition of titanium tetrachloride is completed, the temperature is raised to 30 - 80 °C to continue the reaction, preferably 50 - 60 °C.

[0029] In step (2) of the present invention, the addition time of titanium tetrachloride is 0.2 - 2 h, preferably 0.5 - 1 h; the reaction time after the addition of titanium tetrachloride is 3 - 10 h, preferably 5 - 8 h.

[0030] After the reaction in step (2) of the present invention is completed, water is added to the reaction solution to quench the unreacted titanium tetrachloride;

[0031] In step (2) of the present invention, after the reaction is quenched, a titanium complex is separated. Preferably, the target product can be extracted with n - hexane, and then the titanium complex catalyst is separated by rotary evaporation.

[0032] The present invention also provides the application of the titanium complex in the hydroxylation of anisole.

[0033] A method for the hydroxylation of anisole, in which anisole and hydrogen peroxide are reacted under the catalysis of the titanium complex catalyst of the present invention to obtain o - hydroxyanisole and p - hydroxyanisole.

[0034] Preferably, the mass ratio of the titanium complex, anisole, and hydrogen peroxide is (0.001 - 0.005):1:(0.1 - 0.3), where the mass fraction of hydrogen peroxide is 27.5% - 35%.

[0035] Preferably, the reaction is carried out in solvent C, and the solvent C is selected from one or more of acetone, methanol, water, and DMF. Preferably acetone and water, and the addition amount of the solvent C is 2 - 8 times the mass of anisole.

[0036] Preferably, the reaction temperature is 50 - 80 °C, and the reaction time is 1 - 5 hours.

[0037] The reactors that can be used for the hydroxylation reaction of anisole include but are not limited to batch reactors, tubular reactors, CSTR reactors, etc.

[0038] Using the method of the present invention, a Schiff base is synthesized from naphthaldehyde and aniline or its derivatives as raw materials, and then reacted with titanium tetrachloride to obtain a novel titanium complex, which is used as a catalyst in the hydroxylation reaction of anisole. This novel catalyst can dissolve into the reaction system for a homogeneous reaction, enabling the active titanium to contact the reactants more fully, having higher reaction activity. At the same time, it can also avoid operations such as catalyst separation and regeneration, which is helpful for continuous scale-up. The titanium catalyst complexed with Schiff base has a certain steric effect, can achieve the effect of shape-selective catalysis, can generate more para-products, improve the para-to-ortho ratio of hydroxyanisole, and has higher economic benefits. Specific embodiments:

[0039] The following examples will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed examples and should also include any other known changes within the scope of the rights required by the present invention.

[0040] The performance of the catalyst can be measured by the conversion rate of anisole and the selectivity of the target products o-hydroxyanisole and p-hydroxyanisole. An Agilent liquid chromatography instrument and the external standard method are used to calibrate the contents of anisole, o-hydroxyanisole, and p-hydroxyanisole in the system.

[0041] Source of raw materials: 2-hydroxy-1-naphthaldehyde, 98% purity, purchased externally from Aladdin Biochemical Technology Co., Ltd.; 3-methylaniline, 96% purity, purchased externally from Beijing Innochem Technology Co., Ltd.

[0042] The nuclear magnetic resonance hydrogen spectrum was measured using a Brucker Advance instrument with a frequency of 600 MHz, and TMS was used as the internal standard.

[0043] Example 1

[0044] Under anhydrous and anaerobic conditions, 50 g of 2-hydroxy-1-naphthaldehyde, 15 g of 3-methylaniline and 150 g of DMAC were added to a three-necked glass bottle, and the mixture was stirred and reacted at 50 °C for 6 h. The temperature of the reaction solution was lowered to 0 °C, and a large amount of solid was precipitated. The solid was filtered through a Buchner funnel and finally washed and purified with n-hexane multiple times to obtain Compound 1. Under a nitrogen atmosphere, 50 g of Compound 1 was dissolved in 200 g of ethanol, the mixture was cooled to -78 °C, and 40 g of titanium tetrachloride was slowly added dropwise within 1 h. After the addition was complete, the temperature was raised to 50 °C and the reaction was continued for 6 h. Then, 10 g of water was added to quench the reaction, and the mixture was extracted with n-hexane and rotary evaporated to obtain a titanium complex. NMR analysis: 2.33(3H), 6.83(2H), 6.99(1H), 7.32(1H), 7.36(1H), 7.52(1H), 7.82(2H), 8.05(1H), 8.36(1H). The titanium complex was mixed evenly with anisole, 27.5% hydrogen peroxide, and acetone, and the mass ratio of the four was 0.002:1:0.2:6. The mixed solution was heated to 60 °C and reacted for 3 h. The conversion rate of hydrogen peroxide was >99.5%, and the yield of the product (o-methoxyphenol + p-methoxyphenol) was 92.6%, where the ratio of p-methoxyphenol / o-methoxyphenol was 5.2.

[0045] Example 2

[0046] Under anhydrous and anaerobic conditions, 50 g of 2-hydroxy-1-naphthaldehyde, 25 g of 3-butylaniline and 200 g of acetone were added to a three-necked glass bottle, and the mixture was stirred and reacted at 80 °C for 5 h. The temperature of the reaction solution was lowered to 5 °C, and a large amount of solid was precipitated. The solid was filtered through a Buchner funnel and finally washed and purified with n-hexane multiple times to obtain Compound 1. Under a nitrogen atmosphere, 50 g of Compound 1 was dissolved in 500 g of methanol, the mixture was cooled to -60 °C, and 50 g of titanium tetrachloride was slowly added dropwise within 2 h. After the addition was complete, the temperature was raised to 80 °C and the reaction was continued for 5 h. Then, 10 g of water was added to quench the reaction, and the mixture was extracted with n-hexane and rotary evaporated to obtain a titanium complex. NMR analysis: 0.89(3H), 1.33(2H), 1.56(2H), 2.64(2H), 6.83(1H), 7.11(1H), 7.20(2H), 7.35(2H), 7.52(1H), 7.84(2H), 8.05(1H), 8.96(1H). The titanium complex was mixed evenly with anisole, 27.5% hydrogen peroxide, and water, and the mass ratio of the four was 0.003:1:0.2:8. The mixed solution was heated to 70 °C and reacted for 3 h. The conversion rate of hydrogen peroxide was >99.5%, and the yield of the product (o-methoxyphenol + p-methoxyphenol) was 93.2%, where the ratio of p-methoxyphenol / o-methoxyphenol was 5.8.

[0047] Example 3

[0048] Under anhydrous and anaerobic conditions, 50 g of 2-hydroxy-1-naphthaldehyde, 50 g of aniline, and 200 g of tetrahydrofuran were added to a three-necked glass bottle. The mixture was stirred at 32 °C for 10 h. Then, the temperature of the reaction solution was lowered to -10 °C, and a large amount of solid precipitated. The solid was filtered using a Buchner funnel and finally washed and purified with n-hexane multiple times to obtain Compound 1. Under a nitrogen atmosphere, 50 g of Compound 1 was dissolved in 180 g of acetone. The mixture was cooled to -90 °C, and 39 g of titanium tetrachloride was slowly added dropwise within 0.3 h. After the addition was complete, the temperature was raised to 40 °C and the reaction continued for 10 h. Then, 10 g of water was added to quench the reaction, and the mixture was extracted with n-hexane and rotary evaporated to obtain a titanium complex. NMR analysis: 5.14 (1H), 6.93 (2H), 7.07 (1H), 7.21 (1H), 7.35 (3H), 7.84 (2H), 8.05 (1H), 8.56 (2H). The titanium complex was mixed evenly with anisole, 27.5% hydrogen peroxide, and methanol, and the mass ratio of the four was 0.004:1:0.25:3. The mixed solution was heated to 75 °C and reacted for 2 h. The conversion rate of hydrogen peroxide was >99.5%, and the yield of the product (o-methoxyphenol + p-methoxyphenol) was 92.9%, where the ratio of p-methoxyphenol to o-methoxyphenol was 5.4.

[0049] Example 4

[0050] Under anhydrous and anaerobic conditions, 50 g of 2-hydroxy-1-naphthaldehyde, 40 g of 3-ethylaniline, and 180 g of acetone were added to a three-necked glass bottle. The mixture was stirred at 32 °C for 10 h. Then, the temperature of the reaction solution was lowered to -10 °C, and a large amount of solid precipitated. The solid was filtered using a Buchner funnel and finally washed and purified with n-hexane multiple times to obtain Compound 1. Under a nitrogen atmosphere, 50 g of Compound 1 was dissolved in 500 g of methanol. The mixture was cooled to -70 °C, and 40 g of titanium tetrachloride was slowly added dropwise within 2 h. After the addition was complete, the temperature was raised to 40 °C and the reaction continued for 9 h. Then, 10 g of water was added to quench the reaction, and the mixture was extracted with n-hexane and rotary evaporated to obtain a titanium complex. NMR analysis: 1.18 (3H), 2.72 (2H), 6.83 (1H), 7.11 (1H), 7.20 (2H), 7.35 (2H), 7.52 (1H), 7.83 (2H), 8.05 (1H), 8.86 (1H). The titanium complex was mixed evenly with anisole, 27.5% hydrogen peroxide, and methanol, and the mass ratio of the four was 0.004:1:0.25:3. The mixed solution was heated to 75 °C and reacted for 2 h. The conversion rate of hydrogen peroxide was >99.5%, and the yield of the product (o-methoxyphenol + p-methoxyphenol) was 93.5%, where the ratio of p-methoxyphenol to o-methoxyphenol was 5.0.

[0051] Comparative Example 1

[0052] Mix anisole, 27.5% hydrogen peroxide, and acetone evenly. The mass ratio of the three is 1:0.25:5. Heat the mixed solution to 70 °C and react for 3 h. The conversion rate of hydrogen peroxide is >99.5%, and the yield of the product (o-methoxyphenol + p-methoxyphenol) is 82.1%, where the ratio of p-methoxyphenol to o-methoxyphenol is 2.5.

Claims

1. A titanium complex catalyst, characterized in that, Its structure is as follows: In the formula, R represents hydrogen or an alkyl group with 1 - 6 carbon atoms.

2. A method for preparing a titanium complex catalyst, characterized in that, It includes the following steps: (1) Under anhydrous and anaerobic conditions, aniline or its derivative reacts with 2 - hydroxy - 1 - naphthaldehyde; (2) Under a nitrogen atmosphere, titanium tetrachloride is added to the reaction product of step (1) for reaction to obtain a titanium complex.

3. The preparation method according to claim 2, wherein In the step (1), the structure of the aniline or its derivative is as follows: wherein R represents hydrogen or an alkyl group having 1 to 6 carbon atoms; Preferably, the reaction in step (1) is carried out in solvent A, and the solvent A is one or more of acetone, ethanol, toluene, DMF, DMAC, tetrahydrofuran, toluene, preferably ethanol and tetrahydrofuran.

4. The preparation method according to claim 2 or 3, characterized in that, In step (1), the mass ratio of 2 - hydroxy - 1 - naphthaldehyde to solvent A is 1:(1 - 10), preferably 1:(3 - 8); Preferably, in step (1), the mass ratio of 2 - hydroxy - 1 - naphthaldehyde to aniline or its derivative is 1:(0.2 - 1), preferably 1:(0.3 - 0.5).

5. The preparation method according to any one of claims 2-4, characterized in that, In step (1), the reaction condition is an anhydrous and anaerobic environment; Preferably, in step (1), the reaction temperature is 30°C - 100°C, preferably the reaction temperature is 50°C - 80°C; Preferably, in step (1), the reaction time is 3 - 10 h, preferably 5 - 8 h; Preferably, in step (1), after the reaction, the reaction product is washed out by cooling, cooled to - 10 - 10°C, preferably the cooling temperature is 0 - 5°C; Preferably, in step (1), the reaction product washed out by cooling is separated by filtration, and the solid after filtration is washed three times with a solvent, and the preferred solvent is an alkane with C6 - C10.

6. The preparation method according to any one of claims 2-5, characterized in that, Step (2) can be carried out in solvent B, and the solvent B includes one or more of methanol, ethanol, propanol, water, acetone, preferably ethanol or methanol; Preferably, in step (2), the mass ratio of the reaction product of step (1) to solvent B is 1:(3 - 12), preferably 1:(4 - 10); Preferably, in step (2), the mass ratio of titanium tetrachloride to the reaction product of step (1) is (0.5 - 2):1, preferably (0.7 - 1.4):

1.

7. The preparation method according to any one of claims 2-6, characterized in that, The reaction condition in step (2) is under a nitrogen atmosphere; Preferably, in step (2), titanium tetrachloride is added at a low temperature, the temperature is - 100°C - - 50°C, preferably the addition temperature is - 78°C; Preferably, after the addition of titanium tetrachloride is completed, the temperature is raised to 30 - 80°C for continuous reaction, preferably 50 - 60°C; Preferably, in step (2), the addition time of titanium tetrachloride is 0.2 - 2 h, preferably 0.5 - 1 h; the reaction time after the addition of titanium tetrachloride is 3 - 10 h, preferably 5 - 8 h; Preferably, after the reaction in step (2) is completed, water is added to the reaction solution to quench the unreacted titanium tetrachloride.

8. The application of the titanium complex catalyst according to claim 1 or the titanium complex catalyst prepared by the preparation method according to any one of claims 2 - 7 in the hydroxylation of anisole.

9. A method for hydroxylation of anisole, characterized in that, Anisole and hydrogen peroxide are reacted under the catalysis of the titanium complex catalyst according to claim 1 or the titanium complex catalyst prepared by the preparation method according to any one of claims 2 - 7 to obtain o - hydroxyanisole and p - hydroxyanisole.

10. The method according to claim 9, characterized in that, The mass ratio of the titanium complex, anisole, and hydrogen peroxide is (0.001 - 0.005):1:(0.1 - 0.3); Preferably, the reaction is carried out in solvent C, and the solvent C is selected from one or more of acetone, methanol, water, and DMF, preferably acetone and water; Preferably, the addition amount of the solvent C is 2 - 8 times the mass of anisole; Preferably, the reaction temperature is 50 - 80 °C, and the reaction time is 1 - 5 hours.

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