A process for the preparation of p-cresol from p-cymene

Abstract

This invention discloses a method for preparing p-cresol from p-isopropyltoluene, comprising the following steps: 1) mixing p-isopropyltoluene and carbon nanotubes to form a mixture, then passing the mixture into a multiphase multistage continuous stirred reactor, and then introducing air to carry out an oxidation reaction, obtaining a reaction solution containing isopropyl hydroperoxide; 2) mixing the reaction solution containing isopropyl hydroperoxide with a strongly acidic macroporous cation exchange resin to carry out an acid decomposition reaction, obtaining a reaction solution containing p-cresol. The method for preparing p-cresol from p-isopropyltoluene of this invention has advantages such as being environmentally friendly, having mild reaction conditions, a stable reaction system, easily separable and reusable catalyst, high reactant conversion rate, and high product selectivity, making it suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing p-cresol using p-isopropyltoluene. Background Technology

[0002] p-Cresol and its derivatives have been widely used in pharmaceuticals, pesticides, fine chemicals, and polymer materials, and their market demand continues to grow. Therefore, developing efficient, safe, and environmentally friendly p-cresol production processes is of great significance. The p-isopropyltoluene oxidation method is a recognized efficient method for preparing p-cresol. This method first reacts p-isopropyltoluene with oxygen or air to generate isopropyl hydroperoxide (TCHP) intermediate, which is then decomposed by acid catalysis to produce p-cresol. However, this method suffers from problems such as a complex reaction system, high reaction temperature, high cost and poor stability of catalysts, difficulty in catalyst separation, easy decomposition or even explosion of intermediates, and numerous byproducts (the complex interactions between reactants, oxidants, and peroxide intermediates easily lead to side reactions), which severely limit its industrial application.

[0003] Therefore, it is of great significance to develop a green and environmentally friendly method for preparing p-cresol that has mild reaction conditions, a stable reaction system, easily separable and reusable catalysts, high reactant conversion rate, and high product selectivity. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing p-cresol using p-isopropyltoluene.

[0005] The technical solution adopted in this invention is: A method for preparing p-cresol using p-isopropyltoluene includes the following steps: 1) Mix p-isopropyltoluene and carbon nanotubes to form a mixture, then pass the mixture into a multiphase multistage continuous stirred reactor, and then pass air in to carry out an oxidation reaction to obtain a reaction solution containing isopropyl hydroperoxide. 2) The reaction solution containing isopropyl hydroperoxide is mixed with a strong acid macroporous cation exchange resin and subjected to an acid decomposition reaction to obtain a reaction solution containing p-cresol.

[0006] Preferably, the ratio of p-isopropyltoluene to carbon nanotubes in step 1) is 1 mL: 5 mg to 20 mg.

[0007] More preferably, the ratio of p-isopropyltoluene to carbon nanotubes in step 1) is 1 mL: 8 mg to 14 mg.

[0008] Preferably, the carbon nanotubes (CNTs) in step 1) have undergone pretreatment, which includes the following process: the carbon nanotubes are sequentially acid-washed (to remove metal impurities), washed with water and alcohol, dried and ball-milled, and then placed in a protective atmosphere for heat treatment.

[0009] Preferably, the pickling uses a hydrochloric acid solution with a concentration of 5 mol / L to 7 mol / L.

[0010] Preferably, the pickling time is 6h to 12h.

[0011] Preferably, the ball milling time is 6h to 12h.

[0012] Preferably, the heat treatment includes the following process: controlling the heating rate to rise from room temperature to 900℃ to 1300℃ at a rate of 3℃ / min to 7℃ / min, and holding at that temperature for 2h to 5h.

[0013] Preferably, the oxygen content of the carbon nanotubes in step 1) is 0.40wt% to 0.80wt%.

[0014] Preferably, the flow rate of the mixture in step 1) in the multiphase multistage continuous stirred reactor is 0.3 mL / min to 2.5 mL / min.

[0015] More preferably, the flow rate of the mixture in step 1) in the multiphase multistage continuous stirred reactor is 0.5 mL / min to 1 mL / min.

[0016] Preferably, the air flow rate in the multiphase multistage continuous stirred reactor in step 1) is 50 mL / min to 500 mL / min.

[0017] More preferably, the air flow rate in the multiphase multistage continuous stirred reactor in step 1) is 250 mL / min to 500 mL / min.

[0018] Preferably, the multiphase multistage continuous stirred reactor in step 1) is the ACR-P200 multiphase multistage continuous stirred reactor from AM Technology, UK.

[0019] Preferably, the oxidation reaction in step 1) is carried out at a temperature of 30°C to 130°C and an air pressure of 0.1 MPa to 1.0 MPa.

[0020] More preferably, the oxidation reaction in step 1) is carried out at a temperature of 80℃~100℃ and an air pressure of 0.4MPa~0.7MPa.

[0021] Preferably, the oxidation reaction in step 1) is carried out in a multiphase, multi-stage continuous stirred reactor with a vibration frequency of 3 Hz to 9 Hz.

[0022] More preferably, the oxidation reaction in step 1) is carried out in a multiphase multistage continuous stirred reactor with a vibration frequency of 6 Hz to 9 Hz.

[0023] Preferably, the mass ratio of isopropyl hydroperoxide and strong acid macroporous cation exchange resin in step 2) is 1:0.01 to 0.07.

[0024] More preferably, the mass ratio of isopropyl hydroperoxide and strong acid macroporous cation exchange resin in step 2) is 1:0.03 to 0.07.

[0025] Preferably, the strongly acidic macroporous cation exchange resin in step 2) is at least one of Amberlyst 15 (DuPont), Amberlyst 35 (DuPont), Lewatit K2629 (Lanxess), Purolite CT-275 (Purolite), Purolite CT-269 (Purolite), and D-72 (Purolite).

[0026] More preferably, the strongly acidic macroporous cation exchange resin in step 2) is Amberlyst 15.

[0027] Preferably, the acid decomposition reaction in step 2) is carried out at a temperature of 30℃ to 130℃ for a reaction time of 0.5h to 8h.

[0028] More preferably, the acid decomposition reaction in step 2) is carried out at a temperature of 60℃~80℃ for a reaction time of 2h~5h.

[0029] The reaction principle of this invention is as follows: This invention uses carbon nanotubes as a catalyst to catalyze the oxidation of p-isopropyltoluene to prepare the intermediate isopropyl hydroperoxide (TCHP). The hollow, coiled graphene tubular structure, abundant defect sites, and high specific surface area of ​​carbon nanotubes endow them with excellent electronic conductivity and chemical activity, thereby enhancing the efficiency of oxygen molecule activation, free radical generation, and reactant adsorption, improving the selectivity and generation rate of TCHP. Moreover, carbon nanotubes are easy to separate from the reaction solution, have stable performance, and can be reused. This invention uses a strongly acidic macroporous cation exchange resin as a catalyst to decompose TCHP. The reaction is mild and easy to control, reducing the risk of thermal runaway. Furthermore, the strongly acidic macroporous cation exchange resin will not corrode production equipment and is easy to separate from the reaction solution. This invention uses a multiphase, multi-stage continuous stirred reactor as the reaction vessel, which facilitates large-scale industrial production.

[0030] The beneficial effects of this invention are: the method for preparing p-cresol using p-isopropyltoluene has the advantages of being green and environmentally friendly, having mild reaction conditions, a stable reaction system, easy-to-separate and reusable catalysts, high reactant conversion rate, and high product selectivity, making it suitable for large-scale industrial production.

[0031] Specifically: 1) This invention uses carbon nanotubes as a catalyst to catalyze the oxidation of p-isopropyltoluene to prepare the intermediate TCHP. The active sites on the surface of carbon nanotubes can effectively regulate the free radical reaction pathway, suppress side reactions, improve the selectivity of TCHP, and at the same time ensure the efficient conversion of p-isopropyltoluene. 2) This invention uses carbon nanotubes as a catalyst to catalyze the oxidation of p-isopropyltoluene to prepare the intermediate TCHP, which does not rely on metal catalysts, avoids heavy metal pollution, and the process is green and environmentally friendly. 3) This invention uses carbon nanotubes as a catalyst to catalyze the oxidation of p-isopropyltoluene to prepare the intermediate TCHP. The carbon nanotube catalyst is easy to separate, reusable, has a long service life, and low production cost, thereby reducing the production cost of p-cresol. 4) This invention uses a strong acid macroporous cation exchange resin as a catalyst to decompose TCHP. The reaction is mild and easy to control, which reduces the risk of thermal decomposition and explosion of TCHP. In addition, the strong acid macroporous cation exchange resin will not corrode the production equipment and is easy to separate from the reaction solution, thereby improving process safety. 5) This invention uses a multiphase, multi-stage continuous stirred reactor as the reaction vessel, which stabilizes the reaction system, shortens the material residence time, reduces product decomposition, and eliminates the need for additional peroxide initiators, thus shortening the induction period and enabling industrial-scale controllable production, which is beneficial for large-scale industrial production. Attached Figure Description

[0032] Figure 1 TEM images of preprocessed CNTs.

[0033] Figure 2 This is a physical image of the ACR-P200 multiphase, multistage continuous stirred reactor.

[0034] Figure 3 This is a gas chromatogram of the reaction solution containing isopropyl hydroperoxide in Example 1.

[0035] Figure 4 This is a gas chromatogram of the reaction solution containing p-cresol in Example 1. Detailed Implementation

[0036] The present invention will be further explained and described below with reference to specific embodiments.

[0037] Pretreatment of CNTs: Commercially available CNTs were immersed in a 6 mol / L hydrochloric acid solution and stirred at room temperature for 10 hours. After standing, the supernatant was removed and the mixture was filtered. The solid was washed with deionized water until the washings were neutral, then washed with anhydrous ethanol, and dried overnight at 100°C in an oven. The solid was then ball-milled for 8 hours and transferred to a tube furnace. Argon gas was introduced and the temperature was raised from room temperature to 1100°C at a rate of 5°C / min. The temperature was held for 2 hours and then allowed to cool naturally to room temperature to obtain pretreated CNTs (oxygen content of 0.63 wt%).

[0038] Transmission electron microscopy (TEM) images of pretreated CNTs are shown below. Figure 1 (a and b are TEM images at different magnifications) as shown.

[0039] Depend on Figure 1 As shown in 'a', clear parallel graphene layer stripes can be observed, and the tube wall is composed of multiple layers of graphene sheets rolled up, indicating that the pretreated CNTs have a high degree of graphitization structure. At the same time, there are certain structural defects and disordered regions at the edge of the tube wall. These defects can provide abundant edge carbon active sites, which are conducive to the adsorption and activation of oxygen molecules.

[0040] Depend on Figure 1 As can be seen from b in the figure, the pretreated CNTs exhibit a typical one-dimensional nanotube structure with a large aspect ratio, and the nanotubes are intertwined to form an open network structure.

[0041] In summary, the pretreated CNTs possess a complete tubular structure, a high degree of graphitization, and certain defect characteristics, which provide a structural basis for their catalytic performance in the selective oxidation of isopropyl toluene.

[0042] The preparation processes for pretreated DMD (diamond), pretreated CB (conductive carbon black), pretreated GR (graphene), and pretreated AC (activated carbon) are the same as those for pretreated CNTs.

[0043] The preparation process of o-CNTs-HNO3-1h (carbon nanotubes) is as follows: CNTs (commercially available) were immersed in a 6 mol / L hydrochloric acid solution and stirred at room temperature for 10 h. After standing, the supernatant was removed and the mixture was filtered. The solid was washed with deionized water until the washings were neutral, then washed with anhydrous ethanol, and dried overnight at 100°C in an oven. The mixture was then ball-milled for 4 h. 1 g of the ball-milled CNTs was mixed with 250 mL of a 9 mol / L nitric acid solution and refluxed at 85°C for 1 h. After cooling to room temperature, the mixture was filtered. The solid was washed with deionized water until the washings were neutral, and dried at 100°C in an oven for 8 h. After naturally cooling to room temperature, o-CNTs-HNO3-1h (oxygen content of 2.99 wt%) was obtained.

[0044] The preparation process of o-CNTs-HNO3-1h-1100℃ (carbon oxide nanotubes) is as follows: o-CNTs-HNO3-1h is added to a tube furnace and nitrogen gas is introduced at a flow rate of 50 mL / min. The temperature is then raised from room temperature to 1100℃ at a rate of 10℃ / min, held for 2 hours, and then naturally cooled to room temperature to obtain o-CNTs-HNO3-1h-1100℃ (oxygen content of 1.47 wt%).

[0045] The preparation process of o-CNTs-H2O2-2h (carbon nanotubes) is as follows: 0.5g of ball-milled CNTs (as above) and 50mL of 30% hydrogen peroxide solution are mixed and stirred at 60℃ for 2h. After filtration, the solid is washed several times with deionized water and alcohol, and dried in an oven at 100℃ overnight. After natural cooling to room temperature, o-CNTs-H2O2-2h (oxygen content of 1.79wt%) is obtained.

[0046] The preparation process of o-CNTs-H2O2-1h-1100℃ (carbon nanotubes) is as follows: 0.3g of o-CNTs-H2O2-1h (the preparation process is the same as o-CNTs-H2O2-2h, but the time for ball milling CNTs treated with hydrogen peroxide solution is adjusted to 1h) is added to a ceramic boat, which is then placed in a horizontally placed quartz tube and argon gas is introduced. The temperature is then raised from room temperature to 1100℃ at a controlled heating rate of 10℃ / min, held for 2h, and then naturally cooled to room temperature to obtain o-CNTs-H2O2-1h-1100℃ (oxygen content is 0.90wt%).

[0047] The preparation process of NCNTs (nitrogen-doped carbon nanotubes) is as follows: 1.2 g of ball-milled CNTs (as above) and 60 mL of formamide were mixed and reacted at 180 °C for 12 h. After naturally cooling to room temperature, the mixture was washed with deionized water and anhydrous ethanol and then filtered. The solid was placed in an oven and dried at 100 °C for 8 h. The solid was then transferred to a tube furnace and argon gas was introduced. The temperature was raised from room temperature to 800 °C at a rate of 10 °C / min and held for 2 h. After naturally cooling to room temperature, NCNTs (oxygen content of 1.91 wt% and nitrogen content of 2.79 wt%) were obtained.

[0048] Example 1: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) A mixture was prepared by ultrasonically dispersing p-isopropyltoluene and pretreated CNTs for 1 hour. The ratio of p-isopropyltoluene to pretreated CNTs was 1 mL: 8 mg. The mixture was then fed into a multiphase, multistage, continuous stirred reactor (ACR-P200, AM Technology, UK; actual image shown) at a flow rate of 0.5 mL / min. Figure 2 As shown, the vibration frequency of the reactor is 7Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90℃. Air is then introduced to control the pressure inside the reactor to 0.4MPa. The air flow rate is 300mL / min. Timing is started. The reaction liquid is transferred to the cooling device for cooling. The reactor runs continuously for 4 hours (the theoretical residence time is 100min) to obtain a reaction liquid containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0049] The gas chromatogram of the reaction solution containing isopropyl hydroperoxide in this embodiment is as follows: Figure 3 As shown, the gas chromatogram of the reaction solution containing p-cresol is as follows. Figure 4 As shown.

[0050] Depend on Figure 3 It can be seen that: 3.4 min is the peak of ethanol (solvent), 7.7 min is the peak of p-isopropyltoluene, 8.4 min is the peak of o-dichlorobenzene (internal standard), and 10.4 min and 10.6 min are the peaks of 2-(4-methylphenyl)prop-2-ol and 4-methylacetophenone, respectively, indicating that p-isopropyltoluene was indeed oxidized.

[0051] Depend on Figure 4It can be seen that: 4.4 min is the peak of acetone, 5.8 min is the peak of 1,2-dichloroethane (solvent), 9.5 min is the peak of p-isopropyltoluene, 9.9 min is the peak of o-dichlorobenzene (internal standard), 11.1 min is the peak of p-cresol, and 11.3 min and 11.5 min are the peaks of 2-(4-methylphenyl)prop-2-ol and 4-methylacetophenone, respectively, indicating that TCHP is indeed decomposed.

[0052] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 23.61%, the selectivity of isopropyl hydroperoxide was 61.61%, and the yield of p-cresol was 14.55%.

[0053] Note: Qualitative and quantitative analyses of isopropyltoluene (p-IPT), 2-(4-methylphenyl)prop-2-ol (MPP), 4-methylacetophenone (MAP), cuminaldehyde (CUM), 4-isopropylbenzyl alcohol (IPBA), p-cresol (p-cresol), and acetone (ACE) were performed using gas chromatography. Quantitative analysis of peroxides was performed using iodometric titration, and the ratio of isopropyl hydroperoxide (TCHP) to methyl hydroperoxide (DCHP) was determined using resin decomposition method.

[0054] The conversion rate of isopropyltoluene, the selectivity of isopropyl hydroperoxide, and the yield of p-cresol were all calculated by gas chromatography (GC) analysis combined with iodometric titration and resin decomposition.

[0055] Gas chromatographic detection of reaction solution containing isopropyl hydroperoxide: The reaction solution containing isopropyl hydroperoxide was filtered to remove carbon nanotubes. 1 mL of the filtrate was then added to a sample vial containing 5 mL of anhydrous ethanol. 0.1 mL of o-dichlorobenzene (as an internal standard) was added, and the solution was sonicated until homogeneous. Excess triphenylphosphine was added to reduce the peroxide. The triphenylphosphine was then filtered to remove the peroxide, yielding the test solution. Gas chromatography conditions: injector temperature 250℃, flame ionization detector (FID) temperature 280℃, column oven temperature 90℃, column type DB-1701 capillary column (30.0m×0.32mm×0.25μm); initial column temperature and hold time 90℃ and 5min, then controlled temperature ramp rate 20℃ / min to 200℃, hold for 2min, then controlled temperature ramp rate 20℃ / min to 260℃, hold for 14.5min; injection volume 0.5μL, carrier gas flow rate 20mL / min, column flow rate 1mL / min, air flow rate 400mL / min, hydrogen flow rate 40mL / min, and make-up gas N2 flow rate 15mL / min.

[0056] Gas chromatography detection of reaction solution containing p-cresol: The reaction solution containing p-cresol was filtered to remove the strongly acidic macroporous cation exchange resin Amberlyst 15. Then, 2 mL of the filtrate was diluted with 5 mL of 1,2-dichloroethane to obtain the test solution. Gas chromatography conditions: injector temperature 250℃, flame ionization detector (FID) temperature 280℃, column oven temperature 40℃, column type DB-1701 capillary column (30.0m×0.32mm×0.25μm); initial column temperature and hold time 40℃ and 3min, then controlled temperature ramp rate 20℃ / min to 200℃, hold for 2min, then controlled temperature ramp rate 20℃ / min to 260℃, hold for 14.5min; injection volume 0.5μL, carrier gas flow rate 20mL / min, column flow rate 1mL / min, air flow rate 400mL / min, hydrogen flow rate 40mL / min, and make-up gas N2 flow rate 15mL / min.

[0057] Iodometric titration: Add 2g of sodium bicarbonate powder to a 250mL iodine flask, then use a pipette to take 1mL of the filtered carbon nanotube / strong acid macroporous cation exchange resin Amberlyst. Add the reaction solution of 15 to an iodine flask and record the sample mass m (in g). Then add 20 mL of glacial acetic acid to the iodine flask, followed by potassium iodide solution (made from 4 g of potassium iodide and 10 mL of deionized water). Place the iodine flask in a 60°C oil bath for heating (initially observe the generation of numerous bubbles, the solution color changing from white to yellow, and then gradually to purple). Continue the reaction until no more bubbles are produced. Remove the iodine flask and cool it. Titrate with a 0.1 mol / L sodium thiosulfate standard solution until the solution turns pale yellow. Record the volume V1 (in mL) of sodium thiosulfate standard solution added. Add 1 mL of 0.5% (w / v) starch indicator; the solution turns blue-purple. Continue adding sodium thiosulfate standard solution until the solution turns white. Record the volume V2 (in mL) of sodium thiosulfate standard solution added. The total titration volume is V = V1 + V2. Calculate n. CHP (Unit: mol / L).

[0058] Example 2: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa. The air flow rate is 400 mL / min. Timing is started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0059] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 15.61%, the selectivity of isopropyl hydroperoxide was 58.20%, and the yield of p-cresol was 9.09%.

[0060] Example 3: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 9 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 400 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0061] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 14.96%, the selectivity of isopropyl hydroperoxide was 58.05%, and the yield of p-cresol was 8.68%.

[0062] Example 4: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 6 Hz. The temperature control system of the reactor is turned on to raise the temperature to 90°C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 400 mL / min. Timing is started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0063] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 13.01%, the selectivity of isopropyl hydroperoxide was 66.67%, and the yield of p-cresol was 8.67%.

[0064] Example 5: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 300 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0065] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 15.45%, the selectivity of isopropyl hydroperoxide was 58.18%, and the yield of p-cresol was 8.99%.

[0066] Example 6: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 500 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0067] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 15.20%, the selectivity of isopropyl hydroperoxide was 57.22%, and the yield of p-cresol was 8.70%.

[0068] Example 7: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 10 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 250 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0069] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 13.51%, the selectivity of isopropyl hydroperoxide was 62.46%, and the yield of p-cresol was 8.44%.

[0070] Example 8: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 8 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is turned on to raise the temperature to 90°C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 300 mL / min. Timing is started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0071] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 15.75%, the selectivity of isopropyl hydroperoxide was 62.92%, and the yield of p-cresol was 9.91%.

[0072] Example 9: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 14 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 300 mL / min. Timing is started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0073] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 16.26%, the selectivity of isopropyl hydroperoxide was 49.86%, and the yield of p-cresol was 8.11%.

[0074] Example 10: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 8 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 100°C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 300 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0075] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 16.23%, the selectivity of isopropyl hydroperoxide was 53.82%, and the yield of p-cresol was 8.73%.

[0076] Example 11: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 8 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is turned on to raise the temperature to 80°C. Air is then introduced to control the pressure inside the reactor to 0.1 MPa at a flow rate of 300 mL / min. Timing is started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0077] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 13.92%, the selectivity of isopropyl hydroperoxide was 64.79%, and the yield of p-cresol was 9.02%.

[0078] Example 12: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 8 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 0.5 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90°C. Air is then introduced to control the pressure inside the reactor to 0.7 MPa at a flow rate of 300 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 4 hours to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0079] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 22.34%, the selectivity of isopropyl hydroperoxide was 60.28%, and the yield of p-cresol was 13.47%.

[0080] Example 13: A method for preparing p-cresol using p-isopropyltoluene, comprising the following steps: 1) Mix p-isopropyltoluene and pretreated CNTs and ultrasonically disperse for 1 hour to prepare a mixture. The ratio of p-isopropyltoluene to pretreated CNTs is 1 mL: 8 mg. The mixture is then introduced into a multiphase multistage continuous stirred reactor ACR-P200 at a flow rate of 1 mL / min. The reactor vibration frequency is 7 Hz. The temperature control system of the reactor is then turned on to raise the temperature to 90 °C. Air is then introduced to control the pressure inside the reactor to 0.4 MPa at a flow rate of 300 mL / min. Timing is then started. The reaction solution is transferred to a cooling device for cooling. The reactor is run continuously for 2 hours (the theoretical residence time is 50 min) to obtain a reaction solution containing isopropyl hydroperoxide. 2) Mix the reaction solution containing isopropyl hydroperoxide and the strong acid macroporous cation exchange resin Amberlyst 15 evenly. The mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin Amberlyst 15 is 1:0.03. Then stir the mixture at 60°C for 3 hours to obtain the reaction solution containing p-cresol.

[0081] According to the test results, the conversion rate of isopropyl toluene in this embodiment was 8.06%, the selectivity of isopropyl hydroperoxide was 73.77%, and the yield of p-cresol was 5.95%.

[0082] Comparative Example 1: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the ratio of p-isopropyltoluene to pretreated CNTs in step 1) is adjusted from "1 mL: 8 mg" to "1 mL: 0 mg (i.e. no pretreated carbon nanotubes are added)".

[0083] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 0.55%, the selectivity of isopropyl hydroperoxide was 96.62%, and the yield of p-cresol was 0.53%.

[0084] Comparative Example 2: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1 except that the weight of "pretreated CNTs" in step 1) is replaced with "CNTs (commercially available; untreated)".

[0085] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 8.03%, the selectivity of isopropyl hydroperoxide was 85.88%, and the yield of p-cresol was 6.90%.

[0086] Comparative Example 3: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "pretreated DMD".

[0087] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 0.73%, the selectivity of isopropyl hydroperoxide was 100%, and the yield of p-cresol was 0.73%.

[0088] Comparative Example 4: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "pretreated CB".

[0089] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 1.19%, the selectivity of isopropyl hydroperoxide was 100%, and the yield of p-cresol was 1.19%.

[0090] Comparative Example 5: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "pretreated GR".

[0091] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 1.24%, the selectivity of isopropyl hydroperoxide was 100%, and the yield of p-cresol was 1.24%.

[0092] Comparative Example 6: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "pretreated AC".

[0093] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 5.65%, the selectivity of isopropyl hydroperoxide was 86.86%, and the yield of p-cresol was 4.90%.

[0094] Comparative Example 7: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "o-CNTs-HNO3-1h".

[0095] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 0.76%, the selectivity of isopropyl hydroperoxide was 100%, and the yield of p-cresol was 0.76%.

[0096] Comparative Example 8: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "o-CNTs-HNO3-1h-1100℃".

[0097] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 8.96%, the selectivity of isopropyl hydroperoxide was 83.27%, and the yield of p-cresol was 7.46%.

[0098] Comparative Example 9: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "o-CNTs-H2O2-2h".

[0099] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 2.98%, the selectivity of isopropyl hydroperoxide was 70.83%, and the yield of p-cresol was 2.11%.

[0100] Comparative Example 10: A method for preparing p-cresol using p-isopropyltoluene is identical to Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "o-CNTs-H2O2-1h-1100℃".

[0101] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 8.02%, the selectivity of isopropyl hydroperoxide was 85.36%, and the yield of p-cresol was 6.85%.

[0102] Comparative Example 11: A method for preparing p-cresol using p-isopropyltoluene is identical to that in Example 1, except that the weight of "pretreated CNTs" in step 1) is replaced with "NCNTs".

[0103] The tests showed that the conversion rate of p-isopropyltoluene in this comparative example was 29.22%, the selectivity of isopropyl hydroperoxide was 27.89%, and the yield of p-cresol was 8.14%.

[0104] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing p-cresol using p-isopropyltoluene, characterized in that, It includes the following steps: 1) Mix p-isopropyltoluene and carbon nanotubes to form a mixture, then pass the mixture into a multiphase multistage continuous stirred reactor, and then pass air in to carry out an oxidation reaction to obtain a reaction solution containing isopropyl hydroperoxide. 2) The reaction solution containing isopropyl hydroperoxide is mixed with a strong acid macroporous cation exchange resin and subjected to an acid decomposition reaction to obtain a reaction solution containing p-cresol.

2. The method for preparing p-cresol using p-isopropyltoluene according to claim 1, characterized in that: In step 1), the ratio of p-isopropyltoluene to carbon nanotubes is 1 mL: 5 mg to 20 mg.

3. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 2, characterized in that: Step 1) The carbon nanotubes have undergone pretreatment, which includes the following process: the carbon nanotubes are sequentially acid-washed, water-washed, and alcohol-washed, then dried and ball-milled, and then placed in a protective atmosphere for heat treatment.

4. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 2, characterized in that: The flow rate of the mixture in the multiphase multistage continuous stirred reactor in step 1) is 0.3 mL / min to 2.5 mL / min; and / or, the flow rate of the air in the multiphase multistage continuous stirred reactor in step 1) is 50 mL / min to 500 mL / min.

5. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 2, characterized in that: Step 1) The multiphase multistage continuous stirred reactor is the ACR-P200 multiphase multistage continuous stirred reactor from AM Technology, UK.

6. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 2, characterized in that: Step 1) The oxidation reaction is carried out at a temperature of 30℃~130℃ and an air pressure of 0.1MPa~1.0MPa.

7. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 2, characterized in that: Step 1) The oxidation reaction is carried out in a multiphase, multi-stage continuous stirred reactor with a vibration frequency of 3 Hz to 9 Hz.

8. The method for preparing p-cresol using p-isopropyltoluene according to claim 1, characterized in that: In step 2), the mass ratio of isopropyl hydroperoxide to strong acid macroporous cation exchange resin is 1:0.01 to 0.

07.

9. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 8, characterized in that: Step 2) The strongly acidic macroporous cation exchange resin is at least one of Amberlyst 15, Amberlyst 35, Lewatit K2629, Purolite CT-275, Purolite CT-269, and D-72.

10. The method for preparing p-cresol using p-isopropyltoluene according to claim 1 or 8, characterized in that: Step 2) The acid decomposition reaction is carried out at a temperature of 30℃ to 130℃ for a reaction time of 0.5h to 8h.

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