Cs3Bi2X9 / TiO2 composite material, preparation method thereof and application of Cs3Bi2X9 / TiO2 composite material in catalysis of ammoxidation of methyl aromatic hydrocarbon

Abstract

The invention discloses a Cs3Bi2X9 / TiO2 composite material and a preparation method thereof. The Cs3Bi2X9 / TiO2 composite material is successfully applied to selective photocatalytic ammoxidation of methyl aromatic hydrocarbon. When the composite catalyst is used for selective photocatalytic ammoxidation of methyl aromatic hydrocarbon, high benzonitrile yield (greater than 1g. Gcat-1. Day-1) and high selectivity (greater than 85%) can be obtained under mild conditions (the lowest reaction temperature is 80 DEG C and the lowest reaction pressure is 1bar), and the composite catalyst is a satisfactory photocatalyst.

Description

Technical Field

[0001] The invention relates to a Cs3Bi2X9 / TiO2 composite material and a preparation method thereof and application of the composite material in catalyzing the ammoxidation of methyl aromatic hydrocarbons, belonging to the technical field of photocatalytic preparation of chemicals. Background Art

[0002] Ammoxidation of aromatic compounds is the main route to produce organic nitriles, which have been used as common building blocks for high-performance rubbers and electronic devices. They are important components for the production of pharmaceuticals, agrochemicals, and fine chemicals. In industry, the gas-phase ammoxidation of methyl aromatics is carried out on V-Cr oxide, a process with high reaction temperature (>350°C) or high pressure (>1.5MPa) with high energy loss. Using light energy as the driving force, the ammoxidation of toluene can be achieved under milder conditions, providing an alternative green route for chemical production.

[0003] Although halide perovskites have shown great potential in photocatalytic organic synthesis, the toxicity of lead has limited their further development. 3+ Replace Pb in B position 2+ A new lead-free perovskite with a stoichiometric ratio of A3B2X9 can be prepared. The bismuth-based perovskite Cs3Bi2X9 can effectively activate toluene; TiO2 has been widely studied due to its suitable bandgap, high stability, low cost and non-toxicity. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a Cs3Bi2X9 / TiO2 composite material. The prepared Cs3Bi2X9 / TiO2 composite material can be used for selective photocatalytic ammoxidation of methyl aromatic hydrocarbons.

[0005] The technical solution adopted by the present invention is: a Cs3Bi2X9 / TiO2 composite material, which is composed of Cs3Bi2X9 and TiO2, and the loading rate of Cs3Bi2X9 in the composite material is 5-20wt.%, and the preferred loading rate is 10-20%.

[0006] Preferably, TiO2 is anatase TiO2.

[0007] Also disclosed is a method for preparing the Cs3Bi2X9 / TiO2 composite material, the steps of which include:

[0008] (1) adding CsBr and BiBr3 into DMSO to obtain a DMSO solution containing CsBr and BiBr3, wherein the molar ratio of CsBr to BiBr3 in the DMSO solution is 3:2;

[0009] (2) Add TiO2 to DMSO solution, mix well and then dry to remove DMSO to obtain Cs3Bi2X9 / TiO2 composite material.

[0010] Preferably, in step (2), a physical mixing method is used, the mixing time is 20-40 min, and the mixture is dried in an oven at 100° C. for 24 h to remove DMSO.

[0011] The invention also discloses the application of the Cs3Bi2X9 / TiO2 composite material in catalyzing the ammoxidation of methyl aromatics.

[0012] The invention also discloses the application of the Cs3Bi2X9 / TiO2 composite material in catalyzing methyl aromatic hydrocarbons to prepare aromatic nitrile.

[0013] Preferably, Cs3Bi2X9 / TiO2 composite material is added to the methyl aromatic solution, and under the catalytic conditions of light source and Cs3Bi2X9 / TiO2 composite material, C(sp 3 )-H bond is activated to generate aromatic nitrile in an ammonia and oxygen atmosphere.

[0014] The reaction formula is as follows (1):

[0015]

[0016] Preferably, the reaction temperature is 80-130° C. and the reaction pressure is 1-4 bar.

[0017] Preferably, the light source used is monochromatic light in the wavelength band of λ<550nm.

[0018] Preferably, monochromatic light with a wavelength of 365-530 nm is used.

[0019] Preferably, the methyl aromatic hydrocarbon is toluene or p-chlorotoluene.

[0020] The present invention adopts a simple and easy-to-operate synthesis method to prepare a lead-free perovskite Cs3Bi2X9 and TiO2 composite material, which can have a high benzonitrile yield (>1g·g cat -1 ·day -1 ) and high selectivity (>85%), making it a satisfactory photocatalyst, which is excellent among the reported photocatalysts and thermal catalysts. The work of the present invention provides a strategy for exploring lead-free perovskites as photocatalysts for aromatic ammoxidation, and also provides a method for improving their performance.

[0021] The beneficial effects of the present invention are as follows:

[0022] (1) The present invention provides a method for preparing a Cs3Bi2X9 / TiO2 composite material, wherein TiO2 is the main component and Cs3Bi2X9 is distributed on the surface of TiO2; more importantly, the surfaces of TiO2 and Cs3Bi2X9 are not covered by organic ligands, which can provide more active sites. The entire preparation process is simple, the conditions are controllable, and the cost is low.

[0023] (2) The Cs3Bi2X9 / TiO2 composite material provided by the present invention has a coupling effect, which can realize the liquid-phase methyl aromatic ammoxidation under visible light, especially the toluene ammoxidation under relatively low temperature and low pressure; and the catalyst has high selectivity and conversion rate under the condition of sufficient gas, and has the potential for practical application.

[0024] (3) By mixing Cs3Bi2X9, a substance that can activate toluene, with TiO2, we can achieve photocatalytic toluene ammoxidation with high selectivity and high conversion rate at a relatively low pressure, which provides a new idea for further reducing the temperature of the toluene ammoxidation reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 , Transmission electron microscope (TEM) image of the catalyst sample prepared in Example 1.

[0026] Figure 2 , Scanning electron microscope (SEM) image of the catalyst sample prepared in Example 1.

[0027] Figure 3 , X-ray diffraction data (XRD) of the catalyst sample prepared in Example 1.

[0028] Figure 4 , the relationship between the product yield and selectivity in Example 2 and the change in Cs3Bi2Br9 loading.

[0029] Figure 5 , the relationship between the product yield in Example 2 and temperature.

[0030] Figure 6 , the relationship between the product yield in Example 2 and the wavelength of light.

[0031] Figure 7 , the relationship between the product yield and selectivity in Example 2 and the reaction pressure.

[0032] Figure 8 , GC-MS of the product in Example 2. DETAILED DESCRIPTION

[0033] The present invention is further illustrated by examples below, but is not intended to be limiting of the present invention. The specific materials used in the embodiments of the present invention and their sources are provided below. However, it should be understood that these are merely exemplary and are not intended to limit the present invention, and materials identical or similar to the types, models, qualities, properties or functions of the following reagents and instruments can be used to implement the present invention. The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples, unless otherwise specified, can all be obtained from commercial sources.

[0034] Example 1: Preparation of photocatalyst

[0035] The composite catalyst Cs3Bi2X9 / TiO2 was synthesized by wet impregnation method. 2mL of dimethyl sulfoxide (DMSO) solution contained 500mg of CsBr and BiBr3, and 300mg of TiO2 was mixed with the DMSO solution containing CsBr and BiBr3 precursors; 10wt.% Cs3Bi2X9 / TiO2 sample required 120μL of DMSO solution. After 20min of physical mixing, the mixture was dried in an oven at 100°C for 24h to obtain a halide Cs3Bi2X9 / TiO2 composite material with a loading ratio of 10wt.%. By changing the ratio of DMSO solution containing CsBr and BiBr3 to TiO2, Cs3Bi2X9 / TiO2 with different loading ratios can be obtained. Transmission electron microscope images of the prepared Cs3Bi2X9 / TiO2 catalyst are shown in Figure 1 , scanning electron microscope images are shown in Figure 2 , XRD data see Figure 3 The TiO2 crystal phase used in the preparation is anatase phase. The catalytic effect of using other crystal forms of TiO2 is far inferior to that of anatase phase TiO2. For example, the catalytic effect of rutile phase TiO2 loaded with Cs3Bi2X9 is lower than that of Cs3Bi2X9 alone (regardless of benzonitrile yield or benzonitrile selectivity).

[0036] There are no specific requirements for the particle size of TiO2 except for the crystal form. The particle size of TiO2 used in this embodiment is distributed in the range of 50nm to 800nm.

[0037] Alternatively, the DMSO solution of Cs3Bi2X9 can be used directly to replace the DMSO solution containing CsBr and BiBr3 precursors.

[0038] Example 2: Preparation of benzonitrile

[0039] Preparation of benzonitrile: Weigh 80 mg of Cs3Bi2X9 / TiO2 with different loading rates into a reactor, add 5 mL of toluene, then ultrasonically oscillate the reaction bottle for 5 minutes to mix it evenly, then load the mixed solution into a light-transmitting reactor, replace the reaction system with a 60% O2+40% NH3 state, turn on LED light sources of different wavelengths, and irradiate the reaction for 3 hours. After the reaction is completed, turn off the light source, centrifuge the reaction mixture, pour out the supernatant, and filter the catalyst solid with a filter membrane to obtain a post-reaction liquid. The liquid mainly contains the product benzonitrile and unreacted toluene, which can be separated by distillation to obtain benzonitrile with higher purity. The performance of the obtained product was tested by GC, GC-MS, etc. The relationship between the yield and selectivity of the target product and the change in Cs3Bi2Br9 loading is shown in Figure 4 The relationship between product yield and temperature is shown in Figure 5 The relationship between product yield and light wavelength is shown in Figure 6 The relationship between product yield and selectivity as a function of reaction pressure is shown in Figure 7 The GC-MS test results of the product are shown in Figure 8 The selectivity of the above reaction formula and its corresponding product is shown in the following formula (2):

[0040]

[0041] Example 3: Preparation of p-chlorobenzonitrile

[0042] Preparation of p-chlorobenzonitrile: Weigh 80 mg of 10% Cs3Bi2X9 / TiO2 in a reactor, add 5 mL of p-chlorotoluene, then ultrasonically oscillate the reaction bottle for 5 minutes to mix it evenly, then load the mixed solution into a light-transmitting reactor, replace the reaction system with a 60% O2+40% NH3 state, turn on a 450nm LED light source, and irradiate the reaction for 3 hours. After the reaction is completed, turn off the light source, centrifuge the reaction mixture, pour out the supernatant, and filter the catalyst solid with a filter membrane to obtain a liquid after the reaction. The liquid mainly contains the product p-chlorobenzonitrile and unreacted p-chlorotoluene, which can be separated by distillation to obtain p-chlorobenzonitrile with higher purity. The obtained product is tested for performance by GC, GC-MS, etc. In this embodiment, 78.3 μmol of p-chlorotoluene can be produced, and its selectivity is about 82%. The selectivity of the above reaction formula and its corresponding product is shown in the following formula (3):

[0043]

[0044] In summary, the Cs3Bi2X9 / TiO2 composite material provided by the present invention has a coupling effect, and can realize liquid-phase toluene ammoxidation under visible light; and the catalyst has high selectivity and conversion rate under the condition of sufficient gas, has the potential for practical application, and solves the drawbacks of high temperature and high pressure in current production. Due to milder reaction conditions, the new method of the present invention can prepare a series of nitrile organic compounds, which can be applied in chemical production, chemical reaction mechanism and other aspects.

Claims

1. A Cs3Bi2X9 / TiO2 composite material, characterized in that It is composited by Cs3Bi2X9 and TiO2, and the loading rate of Cs3Bi2X9 in the composite material is 5-20wt.%.

2. The Cs3Bi2X9 / TiO2 composite material according to claim 1, characterized in that TiO2 is anatase TiO2.

3. The method for preparing the Cs3Bi2X9 / TiO2 composite material according to claim 1 or 2, characterized in that The steps include: (1) adding CsBr and BiBr3 into DMSO to obtain a DMSO solution containing CsBr and BiBr3, wherein the molar ratio of CsBr to BiBr3 in the DMSO solution is 3:2; or directly using a DMSO solution of Cs3Bi2X9; (2) Add TiO2 to DMSO solution, mix well and then dry to remove DMSO to obtain Cs3Bi2X9 / TiO2 composite material.

4. Application of Cs3Bi2X9 / TiO2 composite materials in catalytic ammoxidation of methyl aromatics.

5. Application of Cs3Bi2X9 / TiO2 composite materials in catalyzing the preparation of aromatic nitriles from methyl aromatics.

6. The use according to claim 5, characterized in that: Cs3Bi2X9 / TiO2 composite material is added into methyl aromatic hydrocarbon solution, and aromatic nitrile is generated in ammonia oxygen atmosphere under the catalytic conditions of light source and Cs3Bi2X9 / TiO2 composite material.

7. The use according to claim 6, characterized in that: The reaction temperature is 80-130°C, the reaction pressure is 1-4 bar, and the oxygen content in the ammonia-oxygen atmosphere is 20-80%.

8. The use according to claim 6, characterized in that: The light source used is monochromatic light in the wavelength band of λ<550nm or complex light containing light in this wavelength band.

9. The use according to claim 8, characterized in that: Use monochromatic light with a wavelength of 365-530nm.

10. The use according to any one of claims 5 to 9, characterized in that The methyl aromatic hydrocarbon is toluene or p-chlorotoluene.

Images