A method for solvent-free catalytic selective oxidation of cyclohexylbenzene by molecular oxygen to prepare 1-cyclohexylbenzene hydroperoxide

Abstract

The application relates to the field of thermal catalysis, and discloses a method for preparing 1-cyclohexylbenzene hydrogen peroxide by solvent-free thermal catalytic selective oxidation of cyclohexylbenzene with molecular oxygen. The method uses a metal bromide as a catalyst, azobisisobutyronitrile or t-butyl hydroperoxide as an initiator, and pure oxygen as an oxidant, and can effectively selectively oxidize cyclohexylbenzene (CHB) into 1-cyclohexylbenzene hydrogen peroxide under normal pressure, solvent-free conditions and at a temperature above 90 DEG C. The catalytic system has the advantages of low cost, simple operation process, high catalytic oxidation efficiency and high selectivity of the target oxidation product.

Description

Technical Field

[0001] This invention relates to a solventless thermocatalytic molecular oxygen selective oxidation method for producing 1-cyclohexylbenzene hydrogen peroxide. Background Technology

[0002] Industrially, phenol is an important basic organic chemical raw material, widely used in the following areas: ① Synthesizing important chemicals such as phenolic resins, bisphenol A, phenolphthalein, salicylic acid, and alkylphenols. ② As an important intermediate in the industrial production of pharmaceuticals and pesticides. ③ In addition, phenol can also be used as a solvent or disinfectant in laboratories. Currently, the world's annual demand for phenol exceeds 10 million tons, of which the production of bisphenol A consumes approximately 45% annually, making it the largest consumer of phenol. It is estimated that in the coming years, with the continued development of the electronics and information industry and the automotive industry, the global annual consumption of phenol will continue to grow, with an increase of up to 5.5%.

[0003] Cyclohexanone is also an important organic chemical raw material, and its value is mainly reflected in the following aspects: ① It is an important raw material for the production of caprolactam, adipic acid, synthetic resins, and synthetic fibers. ② In addition, cyclohexanone is also widely used in high-grade solvents, polishing agents, and adhesives. Among its many uses, caprolactam and adipic acid are the two major consumer areas of cyclohexanone, accounting for approximately 80% of the global annual production of 5 million tons of cyclohexanone.

[0004] In recent years, with the gradual maturation of benzene partial hydrogenation and alkylation technologies, the production cost of cyclohexylbenzene (CHB) has been greatly reduced. This has made it possible to co-produce phenol and cyclohexanone through CHB peroxidation-decomposition. The selective oxidation of CHB to generate 1-cyclohexylbenzene hydrogen peroxide (1-CHBHP) is the key reaction in this co-production of phenol and cyclohexanone, attracting significant attention and research from large international chemical companies and scholars both domestically and internationally. The French company Societe Des Usines Chimiques Rhone-Poulenc first applied for a patent (US:2680139, 1954-06-01) for the self-oxidation synthesis of 1-CHBHP from CHB using cumene hydroperoxide (CHP, at 2.54 wt.% of CHB) as an initiator and sodium hydroxide (0.18 wt.% of CHB) as an auxiliary agent. With only 6 hours of air blowing and stirring, the CHBHP content can reach 16.4 wt.%. Texaco, an American company, also applied for a related auto-oxidation patent (US:3846499, 1974-11-05): oxygen and nitrogen are introduced into 400 g of cyclohexylbenzene at a rate of 0.5 L / min in a 1:1 ratio, reacted at 130-150 °C for 1-3 h, and then cooled to 105-125 °C for 2-4 h, ultimately achieving a 1-CHBHP content of 25 wt.%. While the patents applied for by these two companies promoted the development of CHB oxidation to some extent, their stringent reaction conditions and low conversion and selectivity did not meet the requirements of industrial production. Therefore, subsequent research mainly focused on the catalytic oxidation of CHB. In the 1980s, Standard Oil reported in its patent application (US:0296577 A1, 2014-10-02) that using polymaleimide as a catalyst and CHP as an initiator, 1 g of both were added to 45 g of CHB in a 1:1 ratio, yielding 5.7 wt.% 1-CHBHP after reacting at 115°C for 4.5 h. Texaco, on the other hand, proposed a patent application (US:105829273B, 2014.11.14) using phenol and alkali metal or alkaline earth metal salts substituted with phenol as catalysts and CHP as an initiator, achieving approximately 15% conversion of CHB and a selectivity of 92.9% for 1-CHBHP. In its patent application (US: 4282383, 1981-08-04), Upjohn Company used 0.5 wt.% NHPI as a catalyst and 2 wt.% CHB peroxide as an initiator. Under solvent-free conditions, the reaction was carried out at 100°C for 8 hours, achieving a conversion rate of 32% and a 1-CHBHP selectivity of 97.6%. Besides NHPI, other catalysts have also been found to be effective for the catalytic oxidation of CHB.Guo Xin compared the catalytic performance of several metal oxides in the peroxidation of CHB and found that MnO2 had the highest activity. Adding 0.01 g of MnO2 to 50 g of CHB, reacting at 120 ℃, and continuously introducing oxygen at a pressure of 1 atm for 10 h resulted in a CHB conversion of 33.58% and a 1-CHBHP selectivity of 80.09% (Fine Chemicals 2010, 27, 244-247). Among the above catalytic oxidation systems for CHB, NHPI is the most effective catalyst, but it is relatively expensive and has poor recovery efficiency. MnO2 has the advantages of being inexpensive and having high catalytic oxidation activity, but it easily triggers the decomposition of peroxy products, reducing the 1-CHBHP selectivity. To address these issues, it is imperative to develop a high-efficiency and inexpensive catalytic system for the solvent-free thermal catalytic oxidation of cyclohexylbenzene to synthesize 1-CHBHP. Summary of the Invention

[0005] The purpose of this invention is to provide an efficient and inexpensive thermocatalytic system for the selective oxidation synthesis of cyclohexylbenzene into 1-CHBHP.

[0006] The present invention discloses a solventless thermocatalytic molecular oxygen selective oxidation method for producing 1-cyclohexylbenzene hydrogen peroxide, characterized in that the method comprises the following steps:

[0007] (1) Weigh the dry metal bromide catalyst, initiator and substrate cyclohexylbenzene according to the set ratio, add the three into a 50mL three-necked flask and stir to form a uniform liquid-solid mixture;

[0008] (2) Transfer the flask containing the mixture obtained in step (1) to the oil bath of the magnetic stirrer, connect the air condenser, the thermometer and the air vent, turn on the magnetic stirrer, heat the oil bath to the set temperature, and then pass pure oxygen at a speed of 20 mL / min for a certain period of time.

[0009] The metal bromide catalyst mentioned in step (1) is one of LiBr, NaBr, KBr, MgBr2, CoBr2, CuBr2, MnBr2, and FeBr2, and its amount is 6.25-18.75 mol of cyclohexylbenzene by mass.

[0010] The initiator mentioned in step (1) is one of azobisisobutyronitrile (AIBN), cumene hydroperoxide (CHP), and hydrogen peroxide (H2O2), and its amount is 0.125-1.25 mol based on the amount of cyclohexylbenzene.

[0011] The temperature of the oil bath in step (2) is 90-130℃.

[0012] The stirring time in step (2) is 8 to 16 hours.

[0013] The present invention has the following advantages:

[0014] (1) The catalyst is inexpensive and readily available, can be recycled and reused, requires less initiator, and has high thermal catalytic reaction efficiency;

[0015] (2) The catalytic reaction system is green, and the target product 1-cyclohexylbenzene hydrogen peroxide (1-CHBHP) has a high yield and excellent selectivity;

[0016] (3) Solvent-free conditions are beneficial for the separation of subsequent products and are suitable for large-scale production.

[0017] The following embodiments are further illustrations of the present invention, but are not limited to the specific embodiments described in the present invention.

[0018] Example 1: The solventless thermocatalytic molecular oxygen selective oxidation of cyclohexylbenzene to produce 1-cyclohexylbenzene hydrogen peroxide according to the present invention includes the following steps:

[0019] (1) Accurately weigh 1 mmol NaBr, 0.05 mmol AIBN and 8 mmol cyclohexylbenzene (CHB), add the three to a 50 mL three-necked flask and stir to form a homogeneous liquid-solid mixture;

[0020] (2) Transfer the flask containing the mixture obtained in step (1) to an oil bath with a magnetic stirrer, connect an air condenser, a thermometer and a vent pipe, turn on the magnetic stirrer, heat the oil bath to 110°C, and react with pure oxygen at a rate of 20 mL / min for 12 h;

[0021] (3) After the reaction was completed, the peroxide product was reduced to alcohol by triphenylphosphine. The conversion rate of CHB was 18.5 mol% and the selectivity of the target product 1-CHBHP was 92.1% by gas chromatography with internal standard method.

[0022] Comparative Example 1: The method described in Example 1 was followed, except that NaBr and AIBN were not added in the CHB oxidation reaction. Gas phase analysis showed that the conversion rate of CHB was 2.1 mol% and the selectivity of the target product 1-CHBHP was 93.2%.

[0023] Comparative Example 2: The method described in Example 1 was followed, except that AIBN was not added in the CHB oxidation reaction. Gas phase spectroscopy analysis showed that the conversion rate of CHB was 13.1 mol% and the selectivity of the target product 1-CHBHP was 86.9%.

[0024] Comparative Example 3: The method described in Example 1 was followed, except that NaBr was not added in the CHB oxidation reaction. Gas phase analysis showed that the conversion rate of CHB was 3.2 mol% and the selectivity of the target product 1-CHBHP was 80.6%.

[0025] Example 2 (2-1~2-7): The method described in Example 1 was followed, except that LiBr, KBr, MgBr2, CoBr2, CuBr2, MnBr2, and FeBr2 were used instead of NaBr as catalysts. The reaction results are shown in Table 1.

[0026] Table 1

[0027]

[0028] As shown in Table 1, NaBr exhibits the highest selectivity for 1-CHBHP among the tested metal bromide catalysts.

[0029] Example 3 (3-1~3-2): The method described in Example 1 was followed, except that cumene hydroperoxide (CHP) and hydrogen peroxide (H2O2) were used instead of AIBN as initiators. The reaction results are shown in Table 2.

[0030] Table 2

[0031]

[0032] As shown in Table 2, among the three initiators tested, AIBN had the best promoting effect on the thermal catalytic oxidation of CHB to 1-CHBHP by NaBr.

[0033] Example 4 (4-1~4-4): The method described in Example 1 was followed, except that the amount of cyclohexylbenzene (CHB) was changed to 4 mmol, 6 mmol, 10 mmol and 12 mmol respectively. The reaction results are shown in Table 3.

[0034] Table 3

[0035]

[0036] As shown in Table 3, within the tested CHB amount range (4-12 mmol), the CHB conversion rate decreased with increasing CHB dosage, accompanied by a significant initial increase in 1-CHBHP selectivity followed by a slight decrease and stabilization. The 1-CHBHP yield was also slightly affected by the substrate dosage, reaching a maximum of 1.434 mmol at 10 mmol CHB dosage.

[0037] Example 5 (5-1~5-4): The method described in Example 1 was followed, except that the amount of sodium bromide was changed to 0.5 mmol, 0.75 mmol, 1.25 mmol and 1.5 mmol respectively. The reaction results are shown in Table 4.

[0038] Table 4

[0039]

[0040] As shown in Table 4, CHB conversion initially increases with increasing NaBr dosage, reaching its maximum at 0.75 mmol NaBr. Subsequently, CHB conversion decreases with further increases in NaBr dosage. The selectivity of 1-CHBHP is less affected by the amount of NaBr, and the optimal value can be obtained at 0.75-1 mmol NaBr.

[0041] Example 6 (6-1~6-4): The method described in Example 1 was followed, except that the amount of AIBN was changed to 0.01 mmol, 0.025 mmol, 0.075 mmol and 0.1 mmol respectively. The reaction results are shown in Table 5.

[0042] Table 5

[0043]

[0044] As shown in Table 5, CHB conversion initially increases with increasing AIBN dosage, reaching its maximum at 0.025 mmol AIBN. Subsequently, CHB conversion gradually decreases with further increases in AIBN dosage. The selectivity of 1-CHBHP is less affected by AIBN dosage, and the optimal value can be obtained at 0.025-0.05 mmol AIBN.

[0045] Example 7 (7-1~7-4): The method described in Example 1 was followed, except that the reaction temperature was changed to 90 ℃, 100 ℃, 120 ℃ and 130 ℃ respectively. The reaction results are shown in Table 6.

[0046] Table 6

[0047]

[0048] As shown in Table 6, CHB conversion initially increases with increasing reaction temperature, but this causes a gradual decrease in 1-CHBHP selectivity. Based on considerations of conversion rate and selectivity, 110-120 °C is the optimal reaction temperature.

[0049] Example 8 (8-1~8-4): The method described in Example 1 was followed, except that the reaction time was changed to 8 h, 10 h, 14 h and 16 h respectively. The results are shown in Table 7.

[0050] Table 7

[0051]

[0052] As shown in Table 7, CHB conversion initially increases continuously with increasing reaction time, while 1-CHBHP selectivity initially increases with prolonged reaction time, reaching a maximum at 12 h, and then gradually decreases. Considering both conversion rate and selectivity, 14 h is the optimal reaction time.

[0053] Example 9 (9-1~9-29): Based on the single-factor experiments described above, with a fixed substrate amount of 8 mmol, four variables—temperature, time, and the amounts of NaBr and AIBN—were further investigated using response surface methodology (RSM) to explore the optimal reaction conditions, thereby obtaining a higher CHB conversion rate and 1-CHBHP selectivity. For this purpose, 29 experiments were designed using the Box-Behnken experimental method, with CHB conversion rate and 1-CHBHP selectivity as the response values. The designed variable levels and experimental results are listed in Tables 8 and 9, respectively.

[0054] Table 8

[0055]

[0056] Table 9

[0057]

[0058] Analysis of variance (ANOVA) was performed on the CHB conversion rate and 1-CHBHP selectivity in Table 9. The results of the ANOVA response surface quadratic model for CHB conversion rate and 1-CHBHP selectivity are listed in Tables 10 and 11, respectively.

[0059] The CHB conversion rate and the 1-CHBHP selectivity response variables can be represented by equations (1) and (2), respectively: where A, B, C and D represent the four response variables: reaction time, reaction temperature, NaBr and AIBN dosage, respectively.

[0060] CHB conversion rate = 33.94 + 5.44A + 9.88B - 0.17C - 0.43D + 0.96AB + 0.28AC + 1.35AD + 0.97BC + 0.13BD - 0.68CD - 1.43A 2 -11.35B 2 -4.02C 2 -4.67D 2 (Formula 1),

[0061] 1-CHBHP selectivity = 72.63 - 10.67A - 15.15B - 0.19C - 1.09D - 4.95AB + 0.4AC - 5.98AD - 2.7BC - 1.08BD + 3.42CD - 4.91A 2 -4.97B 2 +5.02C 2 +2.7D 2 (Formula 2).

[0062] Table 10

[0063]

[0064] The R² and Adj-R² values ​​in Table 10 are 0.8945 and 0.7891, respectively, indicating that the model fits well. The coefficient of variation (CV) of this model is 8.52%, which is within the acceptable accuracy range (10%). The "Pred-R²" of 0.4191 and the "Adj-R²" of 0.7891 are reasonably consistent. "Adeq Precision" is used to represent the signal-to-noise ratio. Generally, a ratio greater than 4 is considered acceptable. The ratio of this fitted model is 10.5409, indicating that the signal strength meets the requirements. In summary, this model can be used to represent the relationship between CHB conversion rate and various variables.

[0065] Table 11

[0066]

[0067] The R² and Adj-R² values ​​in Table 11 are 0.9556 and 0.9113, respectively, indicating a good model fit. The coefficient of variation (CV) of this model is 4.1%, which is within the acceptable accuracy range (10%). The Pred-R² of 0.8245 and the Adj-R² of 0.9113 are reasonably consistent. The Adeq Precision of this fitted model is 19.861, indicating that the signal strength meets the requirements. These results demonstrate that this model can be used to represent the relationship between 1-CHBHP selectivity and various variables.

[0068] The p-value of the fitted model was significant (0.0001), while the lack-of-fit term was not significant, indicating that the simulated predicted values ​​matched the test values ​​well. Based on the above analysis, the optimal conditions were predicted to be a reaction time of 9 h, a reaction temperature of 121.76 °C, a NaBr dosage of 0.77 mmol, and an AIBN dosage of 56 mmol. Under these conditions, the predicted CHB conversion rate was 31.0%, and the selectivity for 1-CHBHP was 82.6%.

[0069] Example 10 (10-1~10-3): The method described in Example 1 was followed, except that the predicted optimal conditions were used, namely, CHB dosage of 8 mmol, reaction time of 9 h, reaction temperature of 121.76℃, NaBr dosage of 0.77 mmol, and AIBN dosage of 56 mmol. Three parallel experiments were conducted, and the results are shown in Table 12.

[0070] Table 12

[0071]

[0072] As shown in Table 12, the CHB conversion rate and 1-CHBHP selectivity obtained from the three parallel experiments were slightly better than those obtained from the response surface simulation. The deviation between the three parallel experiments was less than 2%. The average CHB conversion rate and the average 1-CHBHP selectivity were 33.33 mol% and 86.47%, respectively, and the average 1-CHBHP production was 2.31 mmol.

[0073] The above description is only a preferred embodiment of the present invention. Several optimizations can be made without departing from the principle of the present invention, and these optimizations should also be considered within the scope of protection of the present invention.

Claims

1. A solventless thermocatalytic molecular oxygen selective oxidation method for producing 1-cyclohexylbenzene hydrogen peroxide, characterized in that, The method includes the following steps: (1) Weigh out the dry metal bromide catalyst sodium bromide, initiator and substrate cyclohexylbenzene according to the set ratio, add the three into a 50 mL three-necked flask, and stir to form a uniform liquid-solid mixture. The initiator is azobisisobutyronitrile, cumene hydroperoxide or hydrogen peroxide. (2) Transfer the flask containing the mixture obtained in step (1) to the oil bath of the magnetic stirrer, connect the air condenser, thermometer and vent pipe, turn on the magnetic stirrer, heat the oil bath to the set temperature, and then pass pure oxygen at a speed of 20 mL / min for a certain period of time. (3) After the reaction was completed, the peroxide product was reduced to alcohol by triphenylphosphine, and the conversion rate of cyclohexylbenzene and the yield and selectivity of the target product 1-cyclohexylbenzene hydrogen peroxide were quantitatively analyzed by gas chromatography with internal standard method.

2. The method according to claim 1, characterized in that... The amount of metal bromide catalyst used in step (1) is 6.25-18.75 mol of cyclohexylbenzene by mass.

3. The method according to claim 1, characterized in that... The initiator mentioned in step (1) is one of azobisisobutyronitrile, cumene hydroperoxide, and hydrogen peroxide, and its amount is 0.125-1.25 mol of the amount of cyclohexylbenzene used, based on the amount of the substance.

4. The method according to claim 1, characterized in that... The temperature of the oil bath in step (2) is 90-130 ℃.

5. The method according to claim 1, characterized in that... The stirring reaction time in step (2) is 8~16 h.

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