A process for the catalytic oxidation of phenols to quinones using nanosized titanium metal carbide or nitride

Abstract

This invention discloses a process for synthesizing benzoquinone from phenol or naphthol from phenol using nano-titanium catalysis. The process includes: selective oxidation of phenol or naphthol in a solid-liquid two-phase system under the conditions of a nano-titanium metal catalyst and hydrogen peroxide oxidant to obtain benzoquinone or 1,4-naphthoquinone products. This method uses hydrogen peroxide as the oxidant, improving the selectivity of oxidation sites. The addition of the catalyst lowers the reaction temperature, avoids the high energy consumption of the original process route, and significantly reduces waste.

Description

Technical Field

[0001] This invention belongs to the field of phenol oxidation to prepare quinone compounds, specifically relating to a process for the synthesis of benzoquinone from phenol by nano-titanium catalysis or the synthesis of naphthoquinone from naphthol. Background Technology

[0002] The technical background of phenol oxidation to quinone involves fundamental theories of organic chemistry, research on reaction mechanisms, and application needs in multiple fields. From a chemical perspective, the p-π conjugation effect of the phenolic hydroxyl group (-OH) significantly increases the electron cloud density of the benzene ring, especially at the ortho and para carbon atoms of the hydroxyl group, forming highly reactive oxidation sites. This characteristic leads to phenols readily undergoing dehydrogenation reactions under oxidizing agents (such as acidic potassium permanganate or potassium dichromate) or enzyme catalysis, generating quinone compounds with a conjugated cyclohexadienedione structure.

[0003] Studies of reaction mechanisms have revealed the diversity of phenol oxidation. In the direct oxidation pathway, high temperature or strong oxidizing conditions promote the dehydrogenation of phenolic hydroxyl groups to generate free radicals, ultimately forming quinones. Enzymatic oxidation relies on electron transfer by phenol oxidases, and the activation energy is significantly reduced under pH 3-5 conditions. The wide application of this technology has further promoted research on phenol oxidation. In the food industry, the tea fermentation process catalyzes the oxidation of catechins through polyphenol oxidases to produce theaflavins and thearubigins, a mechanism similar to that of phenol oxidation. In the biopharmaceutical field, phenolic quinones, as precursors of natural antioxidants (such as vitamin K), are used in drug synthesis due to their redox properties.

[0004] Recent research breakthroughs have provided new directions for phenol oxidation technology. A team at Dalian University of Technology (CN117402050 A) developed a low-temperature thermally treated Co-NC catalyst, using molecular oxygen as the oxygen source, to achieve highly efficient and selective oxidation of 2,3,6-trimethylphenol to 2,3,5-trimethylbenzoquinone, solving the environmental problems of traditional homogeneous catalytic systems. This research revealed the dispersion mechanism of N-coordinated active Co(II) species on carbon materials, providing a theoretical basis for the design of green oxidation processes for phenolic compounds. However, this method requires high oxygen pressure or reaction temperature, and the selectivity of the reaction is not high enough. Summary of the Invention

[0005] This invention provides a process for the catalytic oxidation of phenol to quinone using nano-titanium carbide or titanium nitride. This oxidation process improves the selectivity of phenol oxidation to quinone, does not require a high reaction temperature, and the nano-titanium carbide and titanium nitride can be recovered and are not easily lost in the reaction.

[0006] The technical solution of the present invention is as follows:

[0007] A process for synthesizing quinone from phenols via catalytic oxidation using nano-titanium carbides or nitrides includes:

[0008] Under the action of a catalyst, phenolic compounds or naphthol compounds undergo an oxidation reaction with hydrogen peroxide in a solvent to obtain benzoquinone or naphthol derivatives;

[0009] The phenolic compound is a substituted or unsubstituted phenol, the naphthol compound is a substituted or unsubstituted naphthol, and the substituents on the phenol or naphthol are C1~C4 alkyl groups, with substitution positions of ortho or meta, and more preferably methyl or ethyl;

[0010] The catalyst is a titanium metal nitride or carbide;

[0011] The solvent is one or a mixture of alcohol, water, or other solvents.

[0012] The specific feeding method of this invention is as follows:

[0013] The phenolic compound (phenolic compound or naphthol compound) is dissolved in a solvent, and a catalyst is added to the organic solvent. The mixture is then placed under the temperature conditions described above and hydrogen peroxide is added dropwise until the reaction is complete.

[0014] In this invention, a catalyst is essential during the hydrogen peroxide dropwise addition process. Preferably, the catalyst is titanium carbide or titanium nitride. The concentration of the hydrogen peroxide is 27.5 wt% to 70 wt%, and the reaction can occur well within this concentration range without any particularly strict limitation.

[0015] Preferably, the amount of catalyst used is 0.1wt% to 1wt% (relative to the substrate), and more preferably 0.1wt% to 0.5wt% for better initiation effect, and even more preferably 0.3wt% to 0.5wt%.

[0016] In this invention, the hydrogen peroxide is added by dripping, and preferably, the dripping time is 8-10 hours.

[0017] Preferably, the oxidation reaction must be carried out in a solution of the phenolic compound, and a solid-liquid two-phase system is essential. More preferably, a polar organic solvent is used. Even more preferred organic solvents are methanol, ethanol, isopropanol, ethylene glycol, or mixtures thereof.

[0018] In this invention, the reaction temperature is 30-45℃, preferably 30-35℃.

[0019] In this invention, the concentration of the phenolic compound is 10wt% to 16wt%, preferably 13wt% to 14wt%.

[0020] In this invention, pressure has no effect on the conversion of phenolic compounds, and it is preferred to carry out the conversion under normal pressure.

[0021] In this invention, the oxidation reaction can be carried out in an air atmosphere or in a nitrogen atmosphere, preferably under a nitrogen atmosphere.

[0022] In this invention, the overall reaction time is controlled within the range of 10 to 15 hours, preferably within the range of 13 to 15 hours.

[0023] In this invention, after the reaction is complete, the following post-processing procedure is adopted:

[0024] The catalyst was first obtained by filtration, and then quinone was obtained by direct cooling and crystallization from the solvent. The product purity was >98.5%.

[0025] In this invention, the catalyst is washed with an alcohol solvent before being reused;

[0026] The alcohol solvent is methanol, ethanol, isopropanol, ethylene glycol, or a mixture thereof.

[0027] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0028] (1) The present invention uses hydrogen peroxide as an oxidant, and the only byproduct is water, with no additional wastewater or no heavy metal ions in the wastewater;

[0029] (2) The titanium catalytic conditions of the present invention help to reduce the reaction temperature, avoid side reactions and coking caused by disordered oxidation reaction, and make the reaction process safer. Detailed Implementation

[0030] The starting materials are phenolic compounds and naphthol compounds with a purity >98%. The catalysts, titanium carbide and titanium nitride, are commercially available, such as Aladdin's nano-titanium carbide (50nm) and nano-titanium nitride (20nm), and no further purification is required.

[0031] The hydrogen peroxide used in the procedure was a commercially available product, and unless otherwise specified, its concentration was 27.5 wt%.

[0032] The mixture was analyzed using gas chromatography, with naphthalene used as an internal standard to assess the conversion rate of phenol or naphthol, and benzoquinone or naphthoquinone confirmed by retention time comparison with standards.

[0033] Gas chromatography conditions: capillary column, 30m*0.53mm*0.25μm, detector: 230℃, column temperature: 110℃, injector temperature: 200℃, run time: 5min, injection volume: 0.22μl (using a 1ul microsyringe).

[0034] Example 1

[0035] 18.8 g of phenol was dissolved in 170 mL of isopropanol to obtain a phenol-isopropanol solution. 0.094 g of titanium carbide (0.5% by mass) was added as a catalyst to the phenol-isopropanol solution. The resulting solution was added to a round-bottom flask. The mixture was heated to 30 °C with continuous stirring, and hydrogen peroxide (61.76 g) was added dropwise over 8 hours. The reaction solution initially turned yellow, eventually becoming red. After 8 hours of hydrogen peroxide addition, the reaction was maintained at this temperature for another 2 hours until the phenol reaction was complete. Gas chromatography showed a phenol conversion rate of 98.5% and a benzoquinone yield of 96.4%. After the reaction, the solution was filtered, and the residue was titanium carbide. Isopropanol was added to wash the catalyst before reuse in the next batch. The filtrate was cooled to 0 °C, and a yellow benzoquinone solid precipitated. The benzoquinone content was 99.2%.

[0036] The same operating conditions were applied, and the results are shown in Table 1.

[0037] Table 1. Number of applications and results of Example 1

[0038]

[0039] Example 2

[0040] 14.4 g of 1-naphthol was dissolved in 100 mL of isopropanol to obtain a 1-naphthol isopropanol solution. 0.072 g of titanium carbide (0.5% by mass) was added as a catalyst to the 1-naphthol isopropanol solution. The resulting solution was added to a round-bottom flask. The mixture was heated to 30 °C with continuous stirring, and hydrogen peroxide (28.41 g) was added dropwise over 8 hours. The reaction solution initially turned yellow, eventually becoming red. After 8 hours of hydrogen peroxide addition, the reaction was maintained at this temperature for another 4 hours until the 1-naphthol reaction was complete. Gas chromatography showed a 1-naphthol conversion rate of 98.4% and a 1,4-naphthoquinone yield of 94.3%. After the reaction, the mixture was filtered, and the residue was titanium carbide. Isopropanol was added to wash the catalyst before reuse in the next batch. The filtrate was cooled to 0 °C, and a yellow solid of 1,4-naphthoquinone precipitated. The 1,4-naphthoquinone content was 99.2%.

[0041] Example 3

[0042] 18.8 g of phenol was dissolved in 170 mL of isopropanol to obtain a phenol-isopropanol solution. 0.094 g of titanium nitride (0.5% by mass) was added as a catalyst to the phenol-isopropanol solution. The resulting solution was added to a round-bottom flask. The mixture was heated to 30 °C with continuous stirring, and hydrogen peroxide (56.82 g) was added dropwise over 10 hours. The reaction solution initially turned yellow, eventually becoming red. After 10 hours of hydrogen peroxide addition, the reaction solution was kept at this temperature for another 2 hours until the phenol content no longer changed. Gas chromatography showed a phenol conversion rate of 95.6% and a benzoquinone yield of 91.5%. After the reaction, the mixture was filtered, and the residue was titanium nitride. Isopropanol was added to wash the catalyst before reuse in the next batch. The filtrate was cooled to 0 °C, and benzoquinone, a yellow solid, precipitated. The benzoquinone content was 98.7%.

[0043] Example 4

[0044] 18.8 g of o-cresol was dissolved in 170 mL of isopropanol to obtain an o-cresol isopropanol solution. 0.075 g of titanium carbide (0.4% by mass) was added as a catalyst to the o-cresol isopropanol solution. The resulting solution was added to a round-bottom flask. The mixture was heated to 30 °C with continuous stirring, and hydrogen peroxide (45.15 g) was added dropwise over 10 hours. The reaction solution initially turned yellow, eventually becoming red. After the hydrogen peroxide addition was complete for 10 hours, the reaction solution was kept at this temperature for another 4 hours until the o-cresol content no longer changed. Gas chromatography showed a conversion rate of 98.9% and a yield of 97.1%. After the reaction, the mixture was filtered, and the residue was titanium carbide. Isopropanol was added to wash the catalyst before reuse in the next batch. The filtrate was cooled to 0 °C, and a yellow solid of 2-methyl-1,4-benzoquinone precipitated. The content of 2-methyl-1,4-benzoquinone was 98.6%.

[0045] Example 5

[0046] 14.4 g of 1-naphthol was dissolved in 130 mL of ethanol to obtain a 1-naphthol ethanol solution. 0.1 g of titanium carbide (0.7% by mass) was added as a catalyst to the 1-naphthol ethanol solution. The resulting solution was added to a round-bottom flask. The mixture was heated to 30 °C with continuous stirring, and hydrogen peroxide (27.18 g) was added dropwise over 10 hours. The reaction solution initially turned yellow, eventually becoming red. After 10 hours of hydrogen peroxide addition, the reaction solution was kept at this temperature for another 4 hours until the 1-naphthol content no longer changed. Gas chromatography showed a 1-naphthol conversion of 97.5% and a 1,4-naphthoquinone yield of 87.5%. After the reaction, the mixture was filtered, and the residue was titanium carbide. Ethanol was added to wash the catalyst before reuse in the next batch. The filtrate was cooled to 0 °C, and a yellow solid of 1,4-naphthoquinone precipitated. The 1,4-naphthoquinone content was 98.5%.

[0047] The above description is only a preferred embodiment of the present invention and does not limit the present invention. All modifications and substitutions made within the scope of the present invention are included within the protection scope of the present invention.

Claims

1. A process for synthesizing quinone from phenols by catalytic oxidation using nano-titanium carbides or nitrides, characterized in that, include: Under the action of a catalyst, phenolic compounds or naphthol compounds undergo an oxidation reaction with hydrogen peroxide in a solvent to obtain benzoquinone or naphthol derivatives; The phenolic compound is a substituted or unsubstituted phenol, the naphthol compound is a substituted or unsubstituted naphthol, and the substituents on the phenol or naphthol are C1~C4 alkyl groups, with substitution positions of ortho or meta; The catalyst is a titanium metal nitride or carbide; The solvent is one or a mixture of alcohol, water, or other solvents.

2. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 1, characterized in that, The catalyst is nano-titanium carbide or titanium nitride. The feeding method is as follows: The phenolic compound or naphthol compound is added to an alcohol solvent to form a homogeneous alcohol solution. Simultaneously, nano-titanium carbide or titanium nitride is added to the alcohol solution, followed by the addition of hydrogen peroxide and heating to carry out an oxidation reaction.

3. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 2, characterized in that, The amount of catalyst used is 0.1 to 1 wt% of phenolic compounds or naphthol compounds.

4. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 1, characterized in that, The concentration of the phenolic compound or naphthol compound in the solution is 10wt%~16wt%.

5. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 1, characterized in that, The concentration of the hydrogen peroxide is 27.5wt%~70wt%.

6. The process for synthesizing quinone from phenols by catalytic oxidation using nano-titanium carbides or nitrides according to claim 1, characterized in that, The molar ratio of hydrogen peroxide to phenolic compounds or naphthol compounds is 2:1 to 2.5:

1.

7. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 1, characterized in that, The alcohol solvent is methanol, ethanol, isopropanol, ethylene glycol, or a mixture thereof.

8. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 2, characterized in that, The oxidation reaction is carried out at a temperature of 30-45°C. o C, heating time is 10 to 15 hours.

9. The process for synthesizing quinone from phenols by catalytic oxidation of nano-titanium carbides or nitrides according to claim 2, characterized in that, After the reaction is complete, the following post-processing procedure is adopted: The catalyst is first obtained by filtration, and then benzoquinone or naphthoquinone derivatives are obtained by direct cooling and crystallization from the solvent.

10. The process for synthesizing quinone from phenols by catalytic oxidation using nano-titanium carbides or nitrides according to claim 9, characterized in that, The catalyst is washed with an alcohol solvent before being reused; The alcohol solvent is methanol, ethanol, isopropanol, ethylene glycol, or a mixture thereof.

Images