A CO-promoting 2 Photocatalyst for the reduction and oxidative coupling of 1-phenylethanol

Abstract

The invention discloses a novel photocatalyst for promoting CO2 reduction and 1-phenylethanol oxidative coupling, wherein diethylenetriamine is modified on the surface of CdS nanosheets by a solvothermal method, thereby obtaining the photocatalyst CdS-DETA. The novel catalyst can utilize surface amino groups to strengthen the adsorption and activation of CO2 and inhibit the recombination of photogenerated carriers, thereby significantly improving the efficiency of the photocatalytic CO2 reduction and 1-phenylethanol oxidative coupling reaction, and the preparation method thereof is simple and easy, the photocatalytic reaction conditions are mild, the product selectivity is high, and the photocatalytic catalyst has broad application prospects in carbon-based fuels and green preparation of pinacol, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of photocatalytic CO2 technology, and specifically relates to a novel photocatalyst for promoting the oxidative coupling of CO2 reduction and 1-phenylethanol. Background Art

[0002] Excessive CO2 emissions have had a great negative impact on the human living environment, and people have been actively exploring solutions for a long time. Using solar photocatalytic technology to reduce CO2 to small molecules such as CO and CH4 can reduce the concentration of CO2 in the atmosphere and alleviate environmental problems such as climate change. At the same time, the generated carbon-based products can be used as fuel to make up for energy shortages, which is one of the effective ways to serve the national strategy of "carbon neutrality". Studies have shown that under light, semiconductor photocatalysts (such as ZnIn2S4, TiO2, CdSe, CdS, etc.) can be excited to generate photogenerated electrons and ultimately reduce CO2. However, traditional semiconductor photocatalysts have the disadvantages of low quantum efficiency, poor light absorption performance, and unstable structure, resulting in low photocatalytic efficiency. In order to obtain higher reaction efficiency, most traditional photocatalytic CO2 reduction systems use organic amines (such as triethylamine, triethanolamine, etc.) as electron sacrificial agents, which is obviously not in line with the concept of sustainable development and wastes photogenerated holes with oxidation ability.

[0003] In order to improve the efficiency of semiconductor photocatalytic reactions, researchers have developed a variety of strategies, the most common of which is precious metal doping. Precious metal doping can modulate the band structure, light absorption and other properties of semiconductors. During the photoreaction process, the doped metal can serve as a capture site for photogenerated electrons, inhibit the recombination of photogenerated carriers, and can also serve as an active center for catalytic reactions, thereby improving the efficiency of photocatalytic reactions. However, the rarity and high cost of precious metals will seriously hinder the practical application of such photocatalysts. Therefore, the development of new and efficient non-precious metal catalysts is the key to improving the photocatalytic efficiency. Modifying organic groups on the surface of semiconductors is another effective way to improve the efficiency of semiconductor photocatalytic reactions. For example, by grafting amino functional groups on the surface of semiconductors, the adsorption and activation of CO2 molecules can be enhanced, electron transfer can be promoted, carrier recombination can be inhibited, and the photocatalytic efficiency can be improved, but the method often requires high temperature and high pressure synthesis conditions. Therefore, finding a simple and convenient synthesis method has important practical application value.

[0004] Selective oxidation of alcohols to produce polyols is a crucial reaction in the production process of pharmaceutical, flavor, confectionery and beverage industries. However, such reactions usually need to be carried out under harsh conditions, such as high temperature and high pressure. In recent years, the selective oxidation of alcohols under mild conditions using photocatalytic technology is considered to be a "green" strategy for preparing polyols and has received widespread attention.

[0005] Based on the above research background, developing efficient photocatalysts and using photocatalytic technology to simultaneously achieve highly selective CO2 reduction and alcohol oxidation to generate high value-added carbon-based fuels and polyols obviously has important research significance and practical value. Summary of the invention

[0006] In view of the shortcomings of existing catalysts and photocatalytic CO2 conversion systems, the present invention provides a novel photocatalyst for promoting the reduction of CO2 and the oxidative coupling of 1-phenylethanol. The catalyst can effectively enhance the adsorption and activation of CO2 molecules and promote the separation and migration of photogenerated carriers, thereby improving the efficiency of the photocatalytic reaction. Moreover, the catalyst can simultaneously realize the reduction of CO2 and the oxidative coupling of 1-phenylethanol to generate high value-added products CO and pinacol.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A photocatalyst for promoting the oxidative coupling of CO2 reduction and 1-phenylethanol is prepared by modifying the surface of CdS nanosheets with diethylenetriamine (DETA) so that amino groups are evenly distributed on the surface of CdS nanosheets. Specifically, cadmium nitrate tetrahydrate and thiourea are dissolved in diethylenetriamine and stirred at 120°C for 30 min, and then the obtained precipitate is washed and dried to obtain the photocatalyst CdS-DETA.

[0009] Furthermore, 6.9 mmol of the used cadmium nitrate tetrahydrate and 34.6 mmol of thiourea were added to every 50 mL of diethylenetriamine.

[0010] Furthermore, the content of CdS in the photocatalyst is 70wt%.

[0011] The photocatalyst CdS-DETA can be used to promote the reaction of CO2 reduction and 1-phenylethanol oxidative coupling.

[0012] The remarkable effects of the present invention are:

[0013] (1) The present invention modifies the surface of cadmium sulfide with diethylenetriamine, thereby enhancing its adsorption and activation of CO2 molecules, promoting the transfer of photogenerated electrons, and inhibiting the recombination of photogenerated carriers, thereby effectively improving the efficiency of the photocatalytic reaction.

[0014] (2) The present invention constructs a novel photocatalytic redox system, which can simultaneously realize the reduction of CO2 and the oxidative coupling of 1-phenylethanol to generate high value-added products CO and pinacol.

[0015] (3) The preparation method of the present invention is simple and easy to implement. At the same time, the photocatalytic reaction conditions are mild and the product selectivity is high, which is conducive to promotion and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 XRD patterns of CdS-DETA prepared in Example 1 and CdS prepared in Example 2.

[0017] Figure 2 FT-IR graphs of CdS-DETA prepared in Example 1 and CdS prepared in Example 2.

[0018] Figure 3 This is a comparison chart of the activities of CdS-DETA prepared in Example 1 and CdS prepared in Example 2 for photocatalytic CO2 reduction and oxidative coupling of 1-phenylethanol.

[0019] Figure 4 This is the time-yield diagram of the photocatalytic CO2 reduction and 1-phenylethanol oxidative coupling of CdS-DETA prepared in Example 1. DETAILED DESCRIPTION

[0020] In order to make the contents of the present invention easier to understand, the technical solution of the present invention is further described below in conjunction with specific implementation methods, but the present invention is not limited thereto.

[0021] Example 1 Preparation of CdS-DETA

[0022] 6.9 mmol of cadmium nitrate tetrahydrate and 34.6 mmol of thiourea were added to 50 mL of diethylenetriamine (DETA), and stirred in a 120 ℃ oil bath for 30 min. After heating, the mixture was naturally cooled to room temperature, and the precipitate was washed with ethanol and dried in vacuum at 60 ℃ to obtain a CdS-DETA sample.

[0023] Example 2 Preparation of CdS without amine modification

[0024] 100 mg of CdS-DETA prepared in Example 1 was dispersed in 60 mL of deionized water, and transferred to a polytetrafluoroethylene reactor after ultrasonic treatment for 10 min and kept at 120 °C for 12 h. After the reactor was naturally cooled to room temperature, the product was washed with deionized water and dried in vacuo at 60 °C to obtain a CdS sample.

[0025] Figure 1 The XRD patterns of CdS-DETA prepared in Example 1 and CdS prepared in Example 2. As can be seen from the figure, the diffraction peaks of CdS-DETA and CdS correspond to the standard card (JCPDS: 41-1049), indicating that the two samples were successfully prepared.

[0026] Figure 2FT-IR spectra of CdS-DETA prepared in Example 1 and CdS prepared in Example 2. As can be seen from the figure, compared with CdS without amine modification, CdS-DETA shows abundant organic group signals, among which 3100-3300 cm -1 and 1532-1680 cm -1 The strong absorption peaks at 1330cm -1 The characteristic peak at 1400-1500 cm -1 and 2700-3000 cm -1 The characteristic peak at is attributed to the bending vibration of the CH bond. The above FT-IR characterization results illustrate the successful modification of diethylenetriamine on the CdS surface.

[0027] Example 3 Activity Evaluation of CdS-DETA Photocatalytic CO2 Reduction and Oxidative Coupling of 1-Phenylethanol

[0028] The operation process of the CO2 reduction and 1-phenylethanol oxidative coupling efficiency is as follows: 5 mg of photocatalyst and 175 μL of 1-phenylethanol are uniformly dispersed in a mixed solution of 9.5 mL of acetonitrile and 1.5 mL of H2O, and then high-purity CO2 gas is introduced into the reactor to completely exclude air, a 300 W xenon lamp is used as the light source, and the reaction temperature is controlled at 25 °C by a circulating condenser. The gas and liquid products produced by the system are qualitatively and quantitatively analyzed by an Agilent 7890B gas chromatograph equipped with a nickel converter and a Waters 1525 liquid chromatograph.

[0029] Figure 3 The activity comparison diagram of the CdS-DETA prepared in Example 1 and the CdS prepared in Example 2 for photocatalytic CO2 reduction and 1-phenylethanol oxidative coupling. Figure 3 It can be seen that compared with CdS without amine modification, CdS-DETA photocatalyst can effectively improve the efficiency of photocatalytic CO2 reduction. This is mainly because the amine modified on the surface of CdS can enhance the adsorption and activation of CO2, promote the transfer of photogenerated electrons, and inhibit the recombination of photogenerated carriers, thereby improving the efficiency of the photocatalytic reaction.

[0030] Figure 4 The time-yield diagram of the photocatalytic CO2 reduction and 1-phenylethanol oxidative coupling of CdS-DETA prepared in Example 1. Figure 4It can be seen that at first, the yield of the product increased almost linearly with the increase of time, and then the yield of the product slowed down. This is attributed to the reduction of the raw material 1-phenylethanol in the intermittent reaction system; and it can also be seen from the figure that the photocatalyst CdS-DETA showed good activity and selectivity in the catalytic CO2 reduction and 1-phenylethanol oxidative coupling reaction system, and the utilization rate of photogenerated electrons and holes was close to the stoichiometric ratio of 1:1.

[0031] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention should fall within the scope of the present invention.

Claims

1. Application of a CdS-DETA photocatalyst in the oxidative coupling reaction of CO2 reduction and 1-phenylethanol, characterized in that: The surface of the CdS nanosheets is modified by diethylenetriamine so that the amino groups are evenly distributed on the surface of the CdS nanosheets, thereby obtaining the CdS-DETA photocatalyst, which is specifically prepared by dissolving cadmium nitrate tetrahydrate and thiourea in diethylenetriamine, stirring at 120°C for 30 minutes, and then washing and drying the obtained precipitate; The photocatalyst CdS-DETA can be used to promote the reaction of CO2 reduction and 1-phenylethanol oxidative coupling, so as to simultaneously realize the reduction of CO2 and the oxidative coupling of 1-phenylethanol to generate CO and pinacol.

2. The use according to claim 1, characterized in that: The content of CdS in the photocatalyst is 70 wt %.

3. The use according to claim 1, characterized in that: Add 6.9 mmol of cadmium nitrate tetrahydrate and 34.6 mmol of thiourea to every 50 mL of diethylenetriamine.

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