A method for producing phenol and cyclohexanone from cyclohexylbenzene in a visible light mediated one-step process.

Abstract

The present invention discloses a method for preparing phenol and cyclohexanone from cyclohexylbenzene in a one-step process mediated by visible light. The method specifically involves using hydrogen bromide solution as a catalyst and oxygen as an oxidant to directly oxidize cyclohexylbenzene (CHB) in an organic solvent under visible light irradiation, and breaking the carbon-carbon bond to produce phenol and cyclohexanone. The method of the present invention avoids the process in the prior art cyclohexylbenzene process of first oxidizing cyclohexylbenzene to obtain cyclohexylbenzene-1-hydroperoxide (1-CHBHP), treating the mixture of the oxidation reaction products, and then decomposing cyclohexylbenzene peroxide under acidic conditions to obtain phenol and cyclohexanone, thereby avoiding the potential danger caused by the accumulation of peroxide. In addition, the method also has many advantages, such as simple operation, easy availability of reagents, mild reaction conditions, easy control, scalable reaction scale, and good selectivity.

Description

[Technical field]

[0001] The present invention belongs to the technical field of organic synthesis applications, and relates to a method for producing phenol and cyclohexanone from cyclohexylbenzene in a visible light-mediated one-step process. [Background technology]

[0002] Phenol and cyclohexanone are both important basic organic chemical raw materials. Phenol is an important intermediate in the production of phenolic resins, epoxy resins, polycarbonates, etc., and is also used in the fields of medicine, pesticides, dyes, etc. The global demand has reached 11 million tons / year, and it is expected that the consumption of phenol will grow at an average annual rate of 2.5% in the future. Cyclohexanone is mainly used in the production of important monomer raw materials such as caprolactam and adipic acid, which are then used in the production of polymer materials such as nylon and polyurethane. At the same time, cyclohexanone can also be used as an important industrial solvent, and the global demand has reached 4.9 million tons / year.

[0003] At present, the most important industrial method for producing phenol is the oxidative decomposition of cumene (Hock process), whose production capacity accounts for more than 90% of the total phenol production capacity. The first step of the cumene process is to produce cumene by alkylating benzene with propylene, and the supply problem of propylene raw material significantly limits the economic viability of the entire production facility. In addition, the cumene process produces a large amount of acetone as a by-product, which results in surplus acetone and low added value of the product. The cyclohexylbenzene process provides an alternative process route for phenol production, while at the same time avoiding the problem of excess acetone by-product in the cumene process, since the by-product produced by the reaction is cyclohexanone, which has high added value. The previously developed cyclohexylbenzene process for producing phenol and cyclohexanone mainly involves three reaction processes: the one-step hydroalkylation of benzene to produce cyclohexylbenzene (CHB), the oxidation of cyclohexylbenzene to produce cyclohexylbenzene-1-hydroperoxide (1-CHBHP), and the acid decomposition of cyclohexylbenzene hydroperoxide to produce phenol and cyclohexanone (Equation A). [ka]

[0004] Technology related to the cyclohexylbenzene process has been researched and developed by chemical companies and research institutes both in Japan and overseas, and has made some progress. Among them, ExxonMobil has filed a series of patent applications (e.g., CN105829273B, CN105793222A, CN105461535A, CN103664534A, CN102083777B, CN102015604A) and reported a process for cyclohexylbenzene, in which the oxidation process of cyclohexylbenzene (CHB) and the acid decomposition process of cyclohexylbenzene-1-hydroperoxide (1-CHBHP) include the use of oxygen-containing gas such as oxygen, pure air, or other oxygen-containing mixture as an oxidizing agent, the use of N-hydroxyphthalimide (NHPI) as a catalyst, the reaction temperature is 90-130 ° C, and the reaction pressure is 50-10,000 kPa. The acid decomposition reaction uses sulfuric acid as a catalyst, the reaction temperature is 40-120°C, and the reaction pressure is 100-1000kPa. However, the process flow is long, and the accumulation of alkyl peroxide in the peroxidation reaction also causes potential safety risks. In addition, in the acid decomposition reaction of cyclohexylbenzene-1-hydroperoxide (1-CHBHP), in addition to the production of phenol and cyclohexanone, other by-products are also produced, which further reduces the selectivity of the entire process and increases the difficulty of subsequent product separation. The sulfuric acid catalyst in the acid decomposition reaction causes corrosion of the equipment, and a large amount of phenol-containing wastewater is generated during the post-treatment of the reaction.

[0005] The production of cyclohexanone mainly involves the oxidation decomposition of cyclohexane and the hydration-dehydrogenation of cyclohexene. The oxidation decomposition of cyclohexane involves four reaction processes: 1. Hydrogenation of benzene to produce cyclohexane; 2. Air oxidation of cyclohexane to produce cyclohexane hydroperoxide; 3. Decomposition of cyclohexane hydroperoxide under the action of a catalyst to produce cyclohexanone and cyclohexanol; 4. Dehydrogenation of cyclohexanol to produce cyclohexanone. However, this method has the disadvantages of a long process flow, low single-pass conversion rate (3-5%), low product selectivity, and large discharge of three waste products. The hydration-dehydrogenation of cyclohexene involves the hydration reaction of cyclohexene and water under the action of a catalyst to produce cyclohexanol, which is then dehydrogenated and purified to obtain cyclohexanone as the product. However, this method has problems such as high cost of cyclohexene, low single-pass conversion rate of the reaction, and long process flow.

[0006] Visible light has the advantages of low cost, abundant storage, environmental friendliness, non-toxicity, and renewable. In recent years, visible light-mediated photocatalysis strategies have become a powerful synthetic platform that can achieve efficient activation of organic molecules under mild conditions, thus enabling several selective chemical transformations that were previously difficult (Capaldo, L.; Ravelli, D.; Fagnoni, M. Chem. Rev. 2021. doi.org / 10.1021 / acs.chemrev.1c00263; Marzo, L.; Pagire, S.K.; Reiser, O.; Konig, B. Angew. Chem. Int. Ed. 2018, 57, 10034; Shaw, M.H.; Twilton, J.; MacMillan, D.W.C.J.Org.Chem. 2016, 81, 6898.). Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the object of the present invention is to provide a method for producing phenol and cyclohexanone from cyclohexylbenzene in a simple process, under mild reaction conditions, at low cost, easy to operate, easy to control, suitable for industrial production, and environmentally friendly by using oxygen as an oxidizing agent in a light-mediated one-step process. The present invention can produce phenol and cyclohexanone from cyclohexylbenzene in a one-step process, and can avoid the process in the prior art cyclohexylbenzene process of first oxidizing cyclohexylbenzene (CHB) to obtain cyclohexylbenzene-1-hydroperoxide (1-CHBHP), treating the mixture of the oxidation reaction products, and then decomposing cyclohexylbenzene-1-peroxide under acidic conditions to obtain phenol and cyclohexanone.

[0008] The present invention provides a one-step method for preparing phenol and cyclohexanone from cyclohexylbenzene using oxygen as an oxidant, mediated by light and catalyzed by hydrogen bromide solution. Phenol and cyclohexanone are directly prepared from cyclohexylbenzene as a raw material, inexpensive and readily available hydrogen bromide solution as a catalyst, and oxygen as an oxidant in an organic solvent under the conditions of light irradiation and oxygen at atmospheric pressure. The reaction process is shown in reaction scheme (1): [ka]

[0009] Where: In the method of the present invention, the light is visible light.

[0010] In the method of the present invention, the light source used in the reaction is preferably a white LED lamp, and the output is preferably 60W.

[0011] In the process of the present invention, the catalyst is preferably an aqueous hydrogen bromide solution, and the mass fraction of the hydrogen bromide is preferably 40%.

[0012] In the method of the present invention, a phenol may be added as a reaction additive.

[0013] In the method of the present invention, the additive is phenol or a phenol having an electron-withdrawing substituent, including phenol, fluorine-substituted phenol, chlorine-substituted phenol, bromine-substituted phenol, nitro-substituted phenol, trifluoromethyl-substituted phenol, acetyl-substituted phenol, tert-butyl-substituted phenol, methyl-substituted phenol, cyano-substituted phenol, etc.; preferably, phenol, p-fluorophenol, p-chlorophenol, p-bromophenol, p-nitrophenol, p-trifluoromethylphenol, p-acetylphenol, p-cyanophenol, and more preferably, phenol.

[0014] In the method of the present invention, the molar ratio of the cyclohexylbenzene, hydrogen bromide, and additive is 100:(0.1-100):(0-100), and when the reaction scale is 1 mmol, the molar ratio of the cyclohexylbenzene, hydrogen bromide, and additive is preferably 100:(20-30):(0-7.5), and the reaction time is preferably 9-24 hours.

[0015] In the method of the present invention, the molar ratio of the cyclohexylbenzene, hydrogen bromide, and additive is 100:(0.1-100):(0-100). When the reaction scale is 36 mmol, the molar ratio of the cyclohexylbenzene, hydrogen bromide, and additive is preferably 100:(5-15):(0-3), and the reaction time is preferably 6-15 hours.

[0016] In the method of the present invention, the organic solvent is one or more mixtures of 1,2-dichloroethane, 1,1-dibromomethane, dichloromethane, chloroform, ethyl acetate, acetonitrile, acetone, etc. Preferably, the organic solvent is acetone.

[0017] In the method of the present invention, the source of oxygen is pure oxygen or oxygen in air.

[0018] In the method of the present invention, the reaction is preferably carried out at room temperature.

[0019] The advantageous effect of the present invention is to provide a method for producing phenol and cyclohexanone from cyclohexylbenzene in a simple process, under mild reaction conditions, at low cost, easy to operate, easy to control, suitable for industrial production, and in an environmentally friendly light-mediated one-step process using oxygen as an oxidant. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will be described in more detail with reference to the following specific examples. The processes, conditions, experimental methods, etc. for carrying out the present invention are common knowledge or common general knowledge in the relevant field, except for the contents specifically described below, and the contents do not particularly limit the present invention.

[0021] Examples 1 to 4 Cyclohexylbenzene (CHB, 0.17 mL, 1.0 mmol), hydrobromic acid solution (40 wt% aqueous solution, 45 μL), phenol additive (0.01 mmol) and acetone (90 μL) were added to the reaction flask in sequence. The reaction flask was capped with a flip-top stopper, an oxygen balloon was inserted, and then it was placed under the irradiation of a white LED lamp (60 W) for 24 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added to the reaction solution. After mixing, 100 μL of the mixed solution was taken into an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 1. [Table 1]

[0022] Examples 5 to 7 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 10 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the reaction was carried out under irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 2. [Table 2]

[0023] Examples 8 to 9 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, X mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the reaction was carried out under the irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 3. [Table 3]

[0024] Examples 10 to 13 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the flask was placed under the irradiation of a white LED lamp (60 W) to react for a certain period of time, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 4. [Table 4]

[0025] Examples 14 to 16 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the flask was placed under the irradiation of a white LED lamp (60 W) and reacted at a constant temperature for 12 hours. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixture was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 5. [Table 5]

[0026] Examples 17 to 18 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the flask was placed under the irradiation of a white LED lamp for 12 hours of reaction, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 6. [Table 6]

[0027] Examples 19 to 23 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and reaction solvent were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the reaction was carried out under irradiation of a white LED lamp (90 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 7. [Table 7]

[0028] Examples 24 to 27 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then it was placed under irradiation of various light sources (60 W) for 6 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 8. [Table 8]

[0029] Examples 28 to 32 Cyclohexylbenzene (CHB, 6.0 mL), lithium bromide (347.4 mg), acid additive (4 mmol), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the reaction was carried out under irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 9. [Table 9]

[0030] Examples 33 to 36 Cyclohexylbenzene (CHB, 6.0 mL), concentrated hydrochloric acid (0.34 mL), bromide (4 mmol), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the reaction was carried out under irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 10. [Table 10]

[0031] Examples 37 to 38 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. The reaction flask was placed in different air atmospheres and then placed under the irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature by a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The results are shown in Table 11. [Table 11]

[0032] Example 39 Cyclohexylbenzene (CHB, 6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg), and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with oxygen atmosphere, an oxygen balloon was inserted, and then the flask was placed in a 50 °C oil bath in the dark for 12 hours. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixture was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL), and sent to crude NMR. The yield of phenol was 4.2%, the yield of cyclohexanone was 4.0%, and the conversion of cyclohexylbenzene was 7.3%.

[0033] Example 40 Cumene (6.0 mL), hydrobromic acid solution (40 wt% aqueous solution, 0.6 mL), phenol (PhOH, 88.5 mg) and acetone (1.0 mL) were added to the reaction flask in sequence. After replacing the reaction flask with air atmosphere, an air balloon was inserted, and then the flask was placed under the irradiation of a white LED lamp (60 W) for 12 hours, and the reaction temperature was controlled at room temperature with a fan. After the reaction was completed, 0.2 mL of the reaction solution was taken and dibromomethane (35 μL, 0.5 mmol) and deuterated chloroform (0.5 mL) were added. After mixing, 100 μL of the mixed solution was taken in an NMR tube, diluted with deuterated chloroform (0.5 mL) and sent to crude NMR. The yield of phenol was 19.6%, and the conversion of cumene was 26.6%.

[0034] The protection of the present invention is not limited to the above embodiments. All modifications and advantages that can be imagined by those skilled in the art without departing from the spirit and scope of the concept of the present invention are included in the present invention and are protected by the appended claims.

Claims

1. A method for preparing phenol and cyclohexanone from cyclohexylbenzene in a light-mediated one-step process, comprising: taking cyclohexylbenzene as raw material, using hydrogen bromide solution as a catalyst and oxygen as an oxidant under light irradiation to directly oxidize cyclohexylbenzene in an organic solvent to produce phenol and cyclohexanone by breaking carbon-carbon bonds; the reaction process is as shown in reaction formula (1). 【Chemistry 3】

2. 2. The method according to claim 1, wherein the catalyst is an aqueous hydrogen bromide solution, the mass fraction of the hydrogen bromide being 40%.

3. 2. The method according to claim 1, wherein the molar ratio of hydrogen bromide to cyclohexylbenzene is (0.1-100):

100.

4. The method of claim 1 , wherein the light is visible light.

5. 2. The method of claim 1, wherein the organic solvent is one or a mixture of more of 1,2-dichloroethane, 1,1-dibromomethane, dichloromethane, chloroform, acetonitrile, ethyl acetate, and acetone.

6. 2. The method of claim 1, wherein the source of oxygen is pure oxygen or oxygen from air.

7. 2. The method of claim 1, wherein phenol may be added as a reaction additive, said additive being phenol or a phenol having a substituent, including phenol, fluorine-substituted phenol, chlorine-substituted phenol, bromine-substituted phenol, nitro-substituted phenol, trifluoromethyl-substituted phenol, acetyl-substituted phenol, tert-butyl-substituted phenol, methyl-substituted phenol, cyano-substituted phenol.

8. The method according to claim 7, characterized in that the molar ratio of the additive to cyclohexylbenzene is (0-100):

100.

9. 2. The method according to claim 1, wherein the reaction time of the reaction is 6 to 24 hours.

10. Application of the process according to any one of claims 1 to 9 in the one-step production of phenol and cyclohexanone from cyclohexylbenzene.

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