Application of CdS-CdIn2S4 in the two-phase redox preparation of benzyl alcohol, benzaldehyde, and hydrogen from toluene and water.

Abstract

This invention discloses a novel application of CdS-Cdln2S4 in the two-phase oxidation-reduction of toluene and water to prepare benzyl alcohol, benzaldehyde and hydrogen. It can be used for green, efficient and selective oxidation of toluene to prepare benzyl alcohol and benzaldehyde, preventing excessive oxidation of toluene to benzoic acid or carbon dioxide, and can synergistically reduce water to prepare hydrogen. It has the advantages of high selectivity, low energy consumption and low pollution.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically involving CdS-CdIn2S4 as a photocatalyst for the photocatalytic two-phase redox reaction of toluene and water to prepare benzyl alcohol, benzaldehyde and hydrogen. Background Technology

[0002] Benzaldehyde is an important organic compound widely used in fine chemical industries such as fragrances, dyes, pharmaceuticals, pesticides, and auxiliaries, as well as in the synthetic materials industry. Currently, the main industrial processes for synthesizing benzaldehyde include three types: toluene chlorination hydrolysis, direct benzene carbonylation, and toluene gas-phase oxidation. These methods not only require high acid and pressure resistance from production equipment, but the residual chloride ions in the produced products limit benzaldehyde's applications (especially in fragrances and pharmaceuticals), and generate large amounts of wastewater, polluting the environment. While the toluene gas-phase oxidation method avoids the use of chlorine and has a short process flow and fast reaction speed, it suffers from low benzaldehyde selectivity (many byproducts from deep oxidation) and high energy consumption. In recent years, many researchers have focused on developing efficient and green synthesis processes for benzaldehyde, such as benzyl alcohol oxidation, styrene oxidation, and phase-transfer catalytic oxidation. However, these methods still suffer from high costs, high energy consumption, and low benzaldehyde yields. Therefore, developing inexpensive, efficient, and green methods for benzaldehyde preparation is of great significance.

[0003] Compared to traditional high-temperature and high-pressure processes, photocatalysis is a green and low-energy-consumption process with broad application prospects. Under low-temperature, low-pressure conditions and using green oxidants (air and oxygen), various organic reactions can be achieved through photocatalysis. Photocatalytic organic oxidation for synergistic hydrogen production has attracted much attention because it can simultaneously utilize electrons and holes to produce clean and renewable H2 energy and high-value-added chemicals. However, photocatalytic hydrogen evolution synergistic organic oxidation suffers from low reactivity and the need for solvents. Most organic compounds are immiscible with water, requiring solvents to ensure sufficient contact between the catalyst and the organic compounds and water for reaction. Therefore, there is an urgent need to find a two-phase photocatalyst suitable for solvent-free photocatalytic toluene oxidation for synergistic hydrogen production. Summary of the Invention

[0004] The purpose of this invention is to develop new applications of CdS-CdIn2S4 in the two-phase oxidation-reduction of toluene and water to prepare benzyl alcohol, benzaldehyde and hydrogen. It can be used for green, efficient and selective oxidation of toluene to prepare benzyl alcohol and benzaldehyde, preventing the over-oxidation of toluene to benzoic acid or carbon dioxide, and can synergistically reduce water to prepare hydrogen. It has the advantages of high selectivity, low energy consumption and low pollution.

[0005] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: The application of CdS-CdIn2S4 in the two-phase redox reaction of toluene and water to prepare benzyl alcohol, benzaldehyde and hydrogen: CdS-CdIn2S4 is used as a catalyst for the photocatalytic reaction of toluene and water to produce benzyl alcohol, benzaldehyde and hydrogen.

[0006] Preferably, the preparation process of CdS-CdIn2S4 is as follows: cadmium salt, indium salt, and sulfur salt solutions are dissolved in water and stirred evenly to form a solution. Then, the resulting solution is stirred vigorously under heating conditions to obtain CdS-CdIn2S4.

[0007] More preferably, the indium salt is indium chloride tetrahydrate, the cadmium salt is cadmium nitrate tetrahydrate, and the sulfur salt is thioacetamide, and the molar ratio of indium chloride tetrahydrate, cadmium nitrate tetrahydrate, and thioacetamide is 1.5~5:2:4.5~8; even more preferably 2~3:2:5~6.

[0008] More preferably, the temperature of the stirring reaction is 50~130℃, more preferably 90~110℃; and the time is 3~8h, more preferably 5~6h.

[0009] Preferably, the volume ratio of toluene to water is 1~3:1~3.

[0010] Preferably, the light source for photocatalysis is light with a wavelength λ ≥ 400 nanometers, such as a 300 W xenon lamp; the time is 1~48 h.

[0011] Preferably, the amount of catalyst used is not less than 0.5 g / L, and more preferably not less than 1 g / L.

[0012] The advantages of this invention are: CdS-CdIn2S4 is used for the green, efficient, and selective oxidation of toluene to produce benzyl alcohol and benzaldehyde. It can prevent toluene from being over-oxidized to benzoic acid or carbon dioxide and can also synergistically reduce water to produce hydrogen. It has the advantages of high selectivity, low energy consumption, and low pollution. Detailed Implementation

[0013] To better understand the essence of the present invention, the following embodiments are used to further illustrate the content of the present invention, but these should not be regarded as limitations on the present invention. The following description is only used to explain the present invention, and any modifications, substitutions or improvements made without departing from the spirit and principles of the present invention shall fall within the scope of protection claimed by the present invention.

[0014] Example 1

[0015] 2 mmol of indium chloride tetrahydrate, 2 mmol of cadmium nitrate tetrahydrate, and 5 mmol of thioacetamide were dissolved in 160 mL of water and stirred for 30 min. The solution was then heated to 90 °C and kept under vigorous stirring for 5 h. After cooling to room temperature, the solution was sonicated for 1 h and then filtered, washed, and dried to obtain CdS-CdIn2S4.

[0016] The catalytic activity of the prepared photocatalyst was investigated using photocatalytic selective toluene oxidation synergistic with water reduction to produce hydrogen as a model reaction under visible light and vacuum conditions. 20 mg of the prepared photocatalyst material was taken, and then 10 mL of water and 10 mL of toluene were added. The reaction system was evacuated and stirred vigorously for 30 min, followed by irradiation with a 300 W xenon lamp (wavelength greater than 400 nm) for 24 h. After irradiation, the mixture was transferred to a centrifuge tube, centrifuged, and the catalyst was separated. The products were qualitatively and quantitatively analyzed using NMR, HPLC, and GC. The yields of benzyl alcohol and benzaldehyde were 0.15% and 0.34%, respectively, with selectivities of 17.6% and 82.2%. The hydrogen yield was 3.99%.

[0017] Examples 2-5 The catalytic activity of cadmium, indium, and sulfur under different molar ratios was investigated. The operation procedure was similar to that in Example 1, except that the amounts of indium chloride tetrahydrate, cadmium nitrate tetrahydrate, and thioacetamide added to the composite material were changed. All other conditions remained the same, and the samples were numbered CCS-1, CCS-3, CCS-4, and CCS-5. The conditions and reaction results of the composite catalysts prepared in Examples 2-5 are shown in Table 1.

[0018] Table 1. Reaction results of CdS-CdIn2S4 catalyst with different molar ratios

[0019] As shown in Table 1, CdS-CdIn2S4 prepared under different molar ratios of indium chloride tetrahydrate, cadmium nitrate tetrahydrate, and thioacetamide yielded different product yields. Among them, the yields of benzyl alcohol, benzaldehyde, and hydrogen were highest when the molar ratio was 2:2:5.

[0020] Examples 6-9 Following the steps of Example 1 with the best results, with all other conditions unchanged, only the stirring temperature during catalyst preparation was changed to 50, 70, 110, and 130°C, and the samples were numbered T1, T2, T3, and T4. The catalyst conditions and reaction results prepared in Examples 6-9 are shown in Table 2.

[0021] Table 2. Reaction results of CdS-CdIn2S4 catalysts obtained at different stirring temperatures.

[0022] As shown in Table 2, the CdS-CdIn2S4 catalysts obtained at different stirring temperatures yielded different product yields, with the highest yields of benzyl alcohol, benzaldehyde, and hydrogen at 90℃.

[0023] Examples 10-14 Following the steps of Example 1 with the best results, with all other conditions unchanged except for the heating time during the preparation of the composite photocatalyst, the heating times were selected as 3h, 4h, 6h, 7h, and 8h, and the samples were numbered S1, S2, S3, S4, and S5. The reaction results of Examples 10-14 are shown in Table 3.

[0024] Table 3 Effect of different heating times on product yield

[0025] Table 3 shows that the yields of a series of products were obtained by changing the heating time of the catalysts. Compared with Example 1, it was found that the product yield remained basically unchanged after heating for 5 hours. Therefore, a heating time of 5 hours is preferable.

[0026] Examples 15-18 The catalyst with the best effect was selected, and only the ratio of water to toluene was changed while all other conditions remained the same. The samples were numbered M1, M2, M3, and M4. The reaction results of Examples 10-13 are shown in Table 4.

[0027] Table 4 Effect of the ratio of water to toluene on photocatalytic performance

[0028] Table 4 shows that, under the action of the optimal catalyst, a series of yields of benzyl alcohol, benzaldehyde and hydrogen were obtained according to different volume ratios of water to toluene. Compared with Example 1, it was found that a volume ratio of water to toluene of 1:1 was the most suitable.

[0029] Examples 19-23 The catalyst with the best effect was selected, and only the mass of different catalysts was changed while all other conditions remained unchanged. The catalyst masses were selected as 10 mg, 40 mg, 60 mg, 80 mg, and 100 mg, and the samples were numbered Z1, Z2, Z3, Z4, and Z5. The conditions and reaction results of the composite catalysts prepared in Examples 19-23 are shown in Table 1.

[0030] Table 5. Effect of different catalyst masses on product yield

[0031] Table 5 shows that, under the action of the optimal catalyst, varying the catalyst content yielded a series of ethyl acetate yields. Compared with Example 1, it was found that the yield increased with increasing catalyst content, but the rate of increase was not significant after 20 mg. Therefore, the most suitable catalyst content is 1 g / L (based on the total volume of toluene and water).

[0032] Comparative Example 1 20 mg of commercially available CdS was added to 10 mL of water and 10 mL of toluene. The reaction system was evacuated and stirred vigorously for 30 min, then irradiated with a 300 W xenon lamp (wavelength greater than 400 nm) for 48 h. After irradiation, the mixture was transferred to a centrifuge tube and centrifuged to separate the catalyst. The products were qualitatively and quantitatively analyzed using NMR, HPLC, and GC. The yields of benzyl alcohol and benzaldehyde were 0.02% and 0.09%, respectively, with selectivities of 19.2% and 80.2%, and the hydrogen yield was 1.20%.

[0033] Comparative Example 2 1 mmol indium chloride tetrahydrate, 2 mmol cadmium nitrate tetrahydrate, and 4 mmol thioacetamide were dissolved in 160 mL of water and stirred for 30 min. The solution was then heated to 90 °C and kept under vigorous stirring for 5 h. After cooling to room temperature, the solution was sonicated for 1 h and then filtered, washed, and dried to obtain CdIn2S4.

[0034] 20 mg of CdIn₂S₄ was added to 10 mL of water and 10 mL of toluene. The reaction system was evacuated and stirred vigorously for 30 min, then irradiated with a 300 W xenon lamp (wavelength greater than 400 nm) for 48 h. After irradiation, the mixture was transferred to a centrifuge tube and centrifuged to separate the catalyst. The products were qualitatively and quantitatively analyzed using NMR, HPLC, and GC. The yields of benzyl alcohol and benzaldehyde were 0.01% and 0.05%, respectively, with selectivities of 20.4% and 9.3%. The hydrogen yield was 1.13%.

Claims

1. The application of CdS-CdIn2S4 in the two-phase redox preparation of benzyl alcohol, benzaldehyde, and hydrogen from toluene and water, characterized in that, CdS-CdIn2S4 was used as a catalyst for the photocatalytic reaction of toluene and water to produce benzyl alcohol, benzaldehyde and hydrogen. The volume ratio of toluene to water is 1~3:1~3; The light source for the photocatalysis is light with a wavelength λ≥400 nm, and the time is 1~48 h; The amount of catalyst used is not less than 0.5 g / L.

2. The application according to claim 1, characterized in that, The preparation process of CdS-CdIn2S4 is as follows: cadmium salt, indium salt, and sulfur salt solutions are dissolved in water and stirred evenly to form a solution. Then, the resulting solution is stirred vigorously under heating conditions to obtain CdS-CdIn2S4.

3. The application according to claim 2, characterized in that, The indium salt is indium chloride tetrahydrate, the cadmium salt is cadmium nitrate tetrahydrate, and the sulfur salt is thioacetamide. The molar ratio of indium chloride tetrahydrate, cadmium nitrate tetrahydrate, and thioacetamide is 1.5~5:2:4.5~8.

4. The application according to claim 3, characterized in that, The molar ratio of indium chloride tetrahydrate, cadmium nitrate tetrahydrate, and thioacetamide is 2~3:2:5~6.

5. The application according to claim 2, characterized in that, The stirring reaction is carried out at a temperature of 50~130℃ for 3~8 hours.

6. The application according to claim 5, characterized in that, The stirring reaction is carried out at a temperature of 90-110°C for 5-6 hours.

7. The application according to claim 1, characterized in that, The amount of catalyst used is not less than 1 g / L.

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