A method for photocatalytic synthesis of cumene-based cyclohexane

Abstract

This invention discloses a photocatalytic method for the coupling of cumene to form cumene sulfide. Cumene is used as the reaction substrate, and a mixed solution of acetonitrile and water is used as the solvent. In an inert atmosphere, a photocatalytic material is used under illumination at a wavelength of 380-450 nm to induce a dehydrogenation coupling reaction to generate cumene sulfide. The photocatalytic material can be any one of MoS2 / CdS, CdS, or metal-supported CdS photocatalytic materials. This invention utilizes the interaction of photogenerated holes in the photocatalytic material with cumene to induce dehydrogenation and generate a free radical intermediate, which then couples to form cumene sulfide. The method of this invention is simple to synthesize, easy to operate, and exhibits good yield, high selectivity, and cycling stability, showing promising application prospects.

Description

Technical Field

[0001] This invention belongs to the field of heterogeneous photocatalysis and organic synthesis technology, specifically relating to a method for photocatalytic coupling of cumene to form cumene. Background Technology

[0002] 2,3-Dimethyl-2,3-diphenylbutane (2,3-dimethyl-2,3-diphenylbutane) is a multifunctional polymer additive that demonstrates dual application value in the field of polymer modification: it can significantly improve the oxygen index and shorten the quenching time of materials as a fire retardant synergist, and it can also be widely used as a high-temperature crosslinking catalyst / initiator in the graft copolymerization modification of polymers such as polyolefins and polyacrylates. Currently, there are two main technical routes for industrial synthesis: ① Grignard reagent coupling method using α-methylstyrene as a raw material, which requires the conversion of halide intermediates and suffers from problems such as poor thermal stability of halides, easy polymerization of raw materials leading to separation difficulties, and high costs associated with the use of active metals; ② Free radical coupling method using cumene as a raw material, which achieves self-coupling by generating cumene free radicals through the pyrolysis of peroxides (such as di-tert-butyl peroxide). Although this route has the advantages of fewer byproducts and simpler operation, the tert-butanol generated during the reaction lowers the system temperature, leading to a decrease in initiator decomposition efficiency, and the reuse process of initiators and raw materials is complex or impossible, resulting in high costs. Therefore, a new synthetic method is needed to replace the traditional industrial methods. Semiconductor photocatalysis technology drives chemical reactions through electron-hole interactions generated by solar energy on photocatalysts. It is characterized by mild conditions, being green, and economical, making it a promising technology for achieving the coupling synthesis of cumene into methyl ethyl ether under mild conditions. However, traditional photocatalysts suffer from low photocatalytic efficiency due to their low carrier mobility and lack of dehydrogenation sites. Therefore, designing photocatalytic materials with both high carrier mobility and dehydrogenation active sites is crucial for the photocatalytic synthesis of cumene into methyl ethyl ether. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a method for photocatalytic coupling of cumene to form cumene. The method utilizes a photocatalytic material to induce a dehydrogenation coupling reaction in cumene to generate cumene. This synthesis technique is simple, easy to operate, and exhibits good yield, high selectivity, and cycling stability, showing promising application prospects. More specifically, this method uses two-dimensional (2D) CdS nanosheets as a base, fixing 2D MoS2 nanosheets onto the surface of CdS nanosheets via electrostatic self-assembly to form a 2D-2D structured MoS2 / CdS photocatalytic material. The 2D-2D structure provides a large contact area between MoS2 and CdS, resulting in excellent photogenerated carrier migration efficiency. This allows photogenerated electrons to be rapidly exported to the MoS2 surface and H2O from the solution. +The reduction generates H2; due to the rapid separation of photogenerated carriers and the timely consumption of photogenerated electrons, more photogenerated holes can interact with cumene to dehydrogenate it and generate free radical intermediates, which then couple to form cumene.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: a method for photocatalytic coupling of cumene to form cumene, using cumene as the reaction substrate and a mixed solution of acetonitrile and water as the solvent; in an inert atmosphere, a dehydrogenation coupling reaction is carried out by a photocatalytic material under illumination at a wavelength of 380~450 nm to generate cumene; the photocatalytic material is any one of MoS2 / CdS, CdS, or metal-supported CdS photocatalytic material.

[0005] Furthermore, the ratio of cumene to solvent is 0.5 mmol: 10 ml.

[0006] Furthermore, the volume ratio of water to acetonitrile is 1~2:48~49.

[0007] Furthermore, the dehydrogenation coupling reaction takes 12 to 24 hours.

[0008] Furthermore, the metal-supported CdS photocatalyst material can be any one of Ni / CdS, Pd / CdS, or Pt / CdS.

[0009] Furthermore, the preparation process of MoS2 / CdS photocatalytic material is as follows: CdS nanosheets are dispersed in ethanol to form a CdS nanosheet suspension. Then, a certain amount of MoS2 nanosheet sol is added to the CdS nanosheet suspension and stirred evenly. Subsequently, the mixture is centrifuged and dried at room temperature in a vacuum oven to finally obtain the MoS2 / CdS photocatalytic material.

[0010] Furthermore, the preparation process of the CdS nanosheets is as follows:

[0011] A certain amount of cadmium acetate and thiourea were added to a certain amount of ethylenediamine at a molar ratio of 1:3. The mixture was stirred for a period of time to make it homogeneous. The resulting mixture was subjected to a solvothermal reaction under heating conditions. The resulting mixture was centrifuged to obtain a precipitate. The precipitate was washed and dried to obtain CdS nanosheets.

[0012] Further, the preparation process of the MoS2 nanosheet sol is as follows: ammonium tetrathiomolybdate is placed in a tube furnace and heated under an inert atmosphere. After heating, it is naturally cooled to room temperature to obtain MoS2 powder. The MoS2 powder is dispersed in ethanol and ultrasonically treated to obtain MoS2 nanosheet sol. Further, the ultrasonic treatment consists of two parts: ① the mixture is ultrasonically treated for 48 hours, and then the suspension is centrifuged, and 2 / 3 of the supernatant is collected in a glass bottle; ② the obtained liquid is ultrasonically treated again, and then the treated suspension is centrifuged, and 2 / 3 of the supernatant is collected to obtain the MoS2 nanosheet sol.

[0013] Furthermore, the preparation process of the metal-supported CdS photocatalytic material is as follows: CdS nanosheets are dispersed in ethanol, and a certain amount of metal precursor solution (such as nickel nitrate hexahydrate, chloroplatinic acid, chloroauric acid, etc.) is added to the CdS nanosheet suspension. The CdS nanosheet suspension is then irradiated in an inert atmosphere, centrifuged, and dried to obtain the metal-supported CdS photocatalytic material.

[0014] The beneficial effects of this invention are as follows: The dehydrogenation coupling reaction of cumene to form cumene using photocatalytic materials is simple, easy to operate, and exhibits good yield, high selectivity, and cycling stability. This invention prepares a MoS2 / CdS photocatalytic material by electrostatic self-assembly of 2D CdS nanosheets and MoS2 nanosheets. The 2D-2D combination provides a large contact area, and the electrostatic interaction between MoS2 and CdS results in excellent carrier migration efficiency between the two semiconductors. Photogenerated electrons from CdS under photoexcitation can effectively migrate to MoS2, achieving efficient separation of photogenerated carriers. Simultaneously, MoS2 can also serve as an active site for the photocatalytic hydrogen evolution reaction. With MoS2 as a co-catalyst, MoS2 / CdS exhibits more efficient photocatalytic dehydrogenation coupling of cumene to cumene than CdS; and compared to metal-supported CdS photocatalysts, MoS2 / CdS shows higher selectivity for the target product cumene. Attached Figure Description

[0015] Figure 1 SEM image of the MoS2 / CdS photocatalytic material prepared in Example 1;

[0016] Figure 2 AFM image of the MoS2 / CdS photocatalyst material prepared in Example 1;

[0017] Figure 3 The image shows the EDX elemental distribution of the MoS2 / CdS photocatalytic material prepared in Example 1.

[0018] Figure 4XRD spectra of 2D CdS nanosheets, 2D MoS2 nanosheets and MoS2 / CdS photocatalytic materials prepared in Example 1;

[0019] Figure 5 The image shows a multi-round performance evaluation of the MoS2 / CdS photocatalyst material prepared in Example 1 for the synthesis of cumene coupling agent. Detailed Implementation

[0020] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0021] Example 1

[0022] (1) 0.533 g of cadmium acetate and 0.457 g of thiourea were added to 60 mL of ethylenediamine solvent and stirred vigorously for 30-60 minutes. The mixture was then transferred to a 100 mL high-pressure reactor lined with polytetrafluoroethylene and heated to 100 °C for 8 hours. After the reactor cooled to room temperature, the resulting suspension was centrifuged at 8000 r / min for 5 minutes to obtain a bright yellow precipitate, which was then washed several times with ethanol and deionized water. Finally, the product was dried in a vacuum drying oven at room temperature for 8 hours to obtain a 2DCdS nanosheet photocatalyst.

[0023] (2) (NH4)2MoS4 was placed in a tube furnace filled with Ar or N2 atmosphere and calcined at 800 ℃ for 5 hours at a heating rate of 5 ℃ / min. After the sample was naturally cooled to room temperature, bulk layered MoS2 powder was obtained. Then, 100 mg of layered MoS2 powder was dispersed in 50 mL of ethanol, and the resulting mixture was sonicated for 48 hours. The suspension obtained after sonication was first centrifuged at 2000 rpm for 1 hour, and then 2 / 3 of the supernatant was carefully collected in a new glass bottle with a pipette. The liquid was then sonicated again for 4 hours. Finally, the treated suspension was centrifuged at 4000 rpm for 1 hour, and then 2 / 3 of the supernatant was taken out with a pipette to obtain ultrathin 2D MoS2 nanosheet sol.

[0024] (3) 25 mg of CdS nanosheets were dispersed in 30 mL of ethanol to obtain a CdS nanosheet suspension. Then, 1 mL of MoS2 nanosheet sol was added to the CdS nanosheet suspension. After stirring for 4 hours, the mixture was centrifuged and dried in a vacuum oven at room temperature to finally obtain the MoS2 / CdS photocatalytic material.

[0025] Figure 1 This is a SEM image of the MoS2 / CdS photocatalyst material obtained in this embodiment. From... Figure 1As can be seen, the MoS2 / CdS photocatalytic material exhibits a sheet-like microstructure.

[0026] Figure 2 This is the AFM image of the MoS2 / CdS photocatalyst material obtained in this embodiment. From... Figure 2 As can be seen, the maximum thickness of the MoS2 / CdS photocatalytic material obtained by electrostatic self-assembly is about 3.94 nm, and a step change of about 2.35 nm can be clearly observed. This step change is the thickness of the 2D MoS2 nanosheet.

[0027] Figure 3 The image shows the EDX elemental distribution of the MoS2 / CdS photocatalytic material obtained in this embodiment. Mo is selectively distributed on the surface of the CdS nanosheets.

[0028] Figure 4 The images show the XRD patterns of the 2D CdS nanosheets, 2D MoS2 nanosheets, and MoS2 / CdS photocatalytic material obtained in this embodiment. It can be seen that both the CdS nanosheets and the MoS2 / CdS photocatalytic material exhibit distinct hexagonal CdS diffraction patterns, indicating that the electrostatic self-assembly process does not affect the structure of the CdS nanosheets themselves. However, the characteristic XRD peaks of MoS2 nanosheets are not observed in the MoS2 / CdS photocatalytic material. This phenomenon is due to the low concentration and good dispersion of the MoS2 nanosheets.

[0029] Example 2

[0030] 25 mg of CdS nanosheets were dispersed in 30 mL of ethanol to obtain a CdS nanosheet suspension. Then, 2 mL of MoS2 nanosheet sol was added to the CdS nanosheet suspension. After stirring for 4 hours, the mixture was centrifuged and dried at room temperature in a vacuum oven to finally obtain the MoS2 / CdS photocatalytic material.

[0031] Example 3

[0032] 50 mg of CdS nanosheets were dispersed in 50 mL of ethanol, followed by the addition of 2.5 mg of Ni(NO3)2·6H2O (Ni to CdS mass ratio approximately 1%). The reactor containing the resulting mixture was then sealed, and N2 was introduced to purge air from the reactor. The mixture was stirred under aeration for 30 min to maintain an inert atmosphere. Finally, the sealed reactor was irradiated with an LED light source for 1 hour. The solid obtained after centrifugation is the Ni / CdS photocatalytic material.

[0033] Example 4

[0034] 50 mg of CdS nanosheets were dispersed in 50 mL of ethanol, followed by the addition of 0.8 mg of PdCl2 (Pd to CdS mass ratio approximately 1%). The reactor containing the resulting mixture was then sealed, and N2 was introduced to purge air from the reactor. The mixture was stirred under aeration for 30 min to maintain an inert atmosphere. Finally, the sealed reactor was irradiated with an LED light source for 1 hour. The solid obtained after centrifugation is the Pd / CdS photocatalytic material.

[0035] Example 5

[0036] 50 mg of CdS nanosheets were dispersed in 50 mL of ethanol, followed by the addition of 1.33 mg of H₂PtCl₆·6H₂O (the mass ratio of Pt to CdS was approximately 1%). The reactor containing the resulting mixture was then sealed, and N₂ was introduced to purge air from the reactor. The mixture was stirred under aeration for 30 min to maintain an inert atmosphere. Finally, the sealed reactor was irradiated with an LED light source for 1 hour. The solid obtained after centrifugation was the Pt / CdS photocatalytic material.

[0037] Application Example 1

[0038] Ten mg of the CdS nanosheets prepared in Example 1 were added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0039] Application Example 2

[0040] 10 mg of the MoS2 / CdS photocatalyst material prepared in Example 1 was added to a reactor containing 10 mL of acetonitrile, followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0041] Application Example 3

[0042] 10 mg of the MoS2 / CdS photocatalyst material prepared in Example 1 was added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0043] Application Example 4

[0044] Ten mg of the MoS2 / CdS photocatalyst material prepared in Example 1 was added to a reactor containing 10 mL of a mixed solvent (9.6 mL acetonitrile and 0.4 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0045] Application Example 5

[0046] Ten mg of the MoS2 / CdS-2 photocatalyst material prepared in Example 2 was added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0047] Application Example 6

[0048] Ten mg of the Ni / CdS photocatalyst material prepared in Example 3 was added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0049] Application Example 7

[0050] Ten mg of the Pd / CdS photocatalyst material prepared in Example 4 was added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0051] Application Example 8

[0052] Ten mg of the Pt / CdS photocatalyst material prepared in Example 5 was added to a reactor containing 10 mL of a mixed solvent (9.8 mL acetonitrile and 0.2 mL deionized water), followed by the addition of 0.5 mmol of cumene. The reactor was then sealed, and N2 was introduced to purge the air, maintaining an inert atmosphere. Finally, the sealed reactor was irradiated with a 420 nm LED light source for 24 hours.

[0053] It should be noted that in this application, in order to compare the effects of different photocatalysts, 24 hours of light irradiation was selected. In actual experiments, the dehydrogenation coupling reaction time of 12 to 24 hours also showed good results.

[0054] The reaction process in the application example is as follows:

[0055]

[0056] The results of the photocatalyst reactivity determination in the application examples are shown in Table 1.

[0057] Table 1

[0058]

[0059] As shown in Table 1, the MoS2 / CdS photocatalytic material exhibits good conversion rate and selectivity for the coupling of cumene to methyl ethyl ether. Figure 5 The results show the cyclic stability of the MoS2 / CdS photocatalyst material obtained in Example 1 for the coupling reaction of cumene and methyl ethyl ether. Figure 5 As can be seen from Table 1, after four rounds of reaction, the catalytic performance of the photocatalytic material hardly decreased, demonstrating its excellent stability. Table 1 shows that the metal-supported CdS photocatalytic material can catalyze the coupling of cumene to methyl ethyl ether (MEE). However, with MoS2 as a co-catalyst, MoS2 / CdS exhibits more efficient photocatalytic performance for the dehydrogenation coupling of cumene to MEE than CdS. Furthermore, compared to the metal-supported CdS photocatalytic material, MoS2 / CdS shows higher selectivity for the target product MEE.

[0060] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for photocatalytic coupling of cumene to form cyclohexane, characterized in that, Using cumene as the reaction substrate and a mixed solution of acetonitrile and water as the solvent, with a water-to-acetonitrile volume ratio of 1~2:48~49, a dehydrogenation coupling reaction is carried out in an inert atmosphere by a photocatalytic material under illumination at a wavelength of 380~450 nm to generate cumene. The photocatalytic material is MoS2 / CdS, and its preparation process is as follows: CdS nanosheets are dispersed in ethanol to form a CdS nanosheet suspension, then a certain amount of MoS2 nanosheet sol is added to the CdS nanosheet suspension, stirred evenly, centrifuged, and dried at room temperature in a vacuum oven to finally obtain the MoS2 / CdS photocatalytic material.

2. The method for photocatalytic coupling of cumene to form cyclohexane according to claim 1, characterized in that, The ratio of cumene to solvent is 0.5 mmol: 10 ml.

3. The method for photocatalytic coupling of cumene to form cyclohexane according to claim 1, characterized in that, The dehydrogenation coupling reaction takes 12 to 24 hours.

4. The method for photocatalytic coupling of cumene to form cyclohexane according to claim 1, characterized in that, The preparation process of the CdS nanosheets is as follows: a certain amount of cadmium acetate and thiourea are added to a certain amount of ethylenediamine at a molar ratio of 1:3, and stirred for a period of time to make them evenly mixed. The resulting mixture is subjected to a solvothermal reaction under heating conditions. The mixture after the reaction is centrifuged to obtain a precipitate. The precipitate is washed and dried to obtain CdS nanosheets.

5. The method for photocatalytic coupling of cumene to form cyclohexane according to claim 1, characterized in that, The preparation process of the MoS2 nanosheet sol is as follows: ammonium tetrathiomolybdate is placed in a tube furnace and heated under an inert atmosphere. After heating, it is naturally cooled to room temperature to obtain MoS2 powder. The MoS2 powder is dispersed in ethanol and ultrasonically treated to obtain MoS2 nanosheet sol.

6. The method for photocatalytic coupling of cumene to form cyclohexane according to claim 5, characterized in that, The ultrasonic treatment consists of two parts: ① The mixture is ultrasonically treated for 48 hours, and then the suspension is centrifuged and 2 / 3 of the supernatant is collected in a glass bottle; ② The obtained liquid is ultrasonically treated again, and then the treated suspension is centrifuged and 2 / 3 of the supernatant is collected to obtain the MoS2 nanosheet sol.

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