Method for photocatalytic oxidative cracking of lignin

Abstract

The invention relates to a method for preparing an aromatic oxygen-containing compound by photocatalytic oxidative cracking of lignin. According to the method, an organic molecular photocatalyst is adopted as a catalyst, oxygen or air is adopted as an oxidizing agent, lignin model compounds or lignin extracted by an organic solvent is adopted as a raw material, and the obtained aromatic compound products comprise aromatic aldehyde, aromatic carboxylic acid, aromatic ester and phenolic compounds. The method comprises the following reaction processes: adding raw materials, a catalyst and an organic solvent into a photocatalytic reactor, filling oxygen or air with specific pressure, and reacting for a certain time at a specific temperature in a stirring state; the organic photocatalyst disclosed by the invention is a homogeneous catalyst, can be dissolved in an organic solvent and can be in full contact with reaction raw materials; meanwhile, the method is mild in reaction condition and simple in technological process; through the synergistic effect of the catalyst and the specific organic solvent, side reactions such as excessive oxidation of the intermediate and the product are inhibited, and the selectivity and yield of the target aromatic product are improved.

Description

Technical Field

[0001] The present invention relates to a method for preparing aromatic monomer compounds by catalytic oxidation of lignin through visible light, and specifically involves using a non-metallic organic molecular photocatalyst to oxidatively crack a plurality of lignin model compounds with a β-O-4 connection structure and lignin extracted with an organic solvent and other raw materials under light conditions to prepare aromatic aldehydes, aromatic carboxylic acids, aromatic formate and phenolic compounds. Background Art

[0002] Lignin is a natural aromatic polymer and one of the three major components of lignocellulosic biomass. Using lignin as a raw material to produce high value-added aromatic chemicals is an important way to achieve efficient conversion and utilization of lignin. Among them, catalytic oxidation and cracking of lignin can achieve the preparation of aromatic oxygenated compounds under relatively mild reaction conditions. For example, the current large-scale process routes for preparing vanillin from lignin at home and abroad mainly use nitrobenzene alkaline oxidation and Cu (II) alkaline oxidation systems (Cellulose Science and Technology, 2010, 18, 49–54). These systems have a high yield of vanillin, but the use of strong alkaline solutions and the generation of a large amount of wastewater cause secondary environmental pollution, and oxidants such as nitrobenzene are highly toxic.

[0003] In recent years, a system for catalyzing the oxidative cracking of lignin using oxygen as an oxidant has also been developed. For example, Carsten Bolm et al. reported that hydrotalcite-based catalysts containing Cu and V elements can catalyze the oxidative cracking of lignin model molecules and raw materials such as organic solvent-extracted lignin to prepare aromatic aldehydes (ChemSusChem 2015, 8, 2106–2013); in addition, perovskite-type catalysts containing Mn, Cu or Co can also catalyze the oxidative depolymerization of lignin in alkaline solutions using O2 as an oxygen source (Energy Fuels 2009, 23, 19–24). O2 activation and selective bond breaking of lignin are the key issues to be solved. Since the three phenylpropane monomers of lignin are mainly connected in a β-O-4 manner, in order to understand the mechanism of catalytic oxidative cracking of lignin, research is mainly carried out on the lignin β-O-4 model compound, in order to achieve the oxidative breaking of the C–C bond and C–O bond of the lignin β-O-4 structure.

[0004] In recent years, photocatalytic oxidation has also been considered as a new type of oxidation technology in the research of lignin conversion to prepare aromatic chemicals. Compared with thermochemical processes, photocatalytic reactions have milder conditions and shorter reaction times, and can use renewable solar energy to promote carbon emission reduction in the reaction process. Some literature has reported the use of visible light catalytic methods to achieve catalytic cracking of lignin model compounds to prepare aromatic compounds. In 2014, Stephenson's group used a two-step method, first using the oxidant [4-AcNHTEMPO]BF4 to oxidize benzyl alcohol, and then using the photocatalyst [Ir(ppy)2(dtbbpy)]PF6 to cleave the C–O bond, to achieve the conversion of lignin β-O-4 model molecules (J.Am.Chem.Soc.2014,136,1218–1221). In 2015, Han Sen Soo et al. used a one-step oxidation method with a V complex as a catalyst to achieve the C–C bond cleavage of the β-O-4 model molecule (Chem. Sci. 2015, 6, 7130–7142). In 2018, Liu et al. reported the non-metallic C3N4 photocatalytic cleavage of the C–C bond of the lignin β-O-4 model molecule to prepare aromatic aldehydes and other compounds, with a selectivity of more than 90% (ACS Catal. 2018, 8, 4761-4771). The methods reported so far still have problems such as the difficulty in synthesizing homogeneous metal complex catalysts, the high price of precious metal catalysts, the over-oxidation of phenolic products, and the insufficient contact between heterogeneous photocatalysts and lignin raw materials. Therefore, it is still necessary to develop efficient visible light catalytic lignin oxidative depolymerization catalysts.

[0005] Molecular catalysts such as organic photosensitizers are cheap and readily available, have strong absorption in the visible light wavelength range, and are easily adjustable in redox ability. They can easily activate O2 to produce highly reactive oxygen species under light excitation, and therefore have potential application advantages in catalyzing the oxidative depolymerization of lignin.

[0006] We have developed a method for the oxidative cracking of lignin model compounds and organic solvent-extracted lignin using non-metallic organic molecules as photocatalysts. This method has mild reaction conditions, simple operation, cheap and readily available photocatalysts, and low usage. By optimizing solvents and reaction conditions, highly selective preparation of aromatic oxygenated compounds can be achieved, while maintaining their stability and inhibiting over-oxidation, which has important application prospects. Summary of the invention

[0007] The significance of the present invention lies in the invention of a new method for preparing aromatic oxygen-containing compounds by photocatalytic oxidative cracking of lignin, which uses non-metallic organic photosensitizer molecules as catalysts and can be dissolved in organic solvents, thus overcoming the problem of poor contact between solid catalysts and lignin substrates; the organic molecular catalyst has low cost and small dosage, and through the synergistic effect with the solvent system, it realizes the efficient depolymerization of a variety of lignin β-O-4 model compounds and lignin extracts, and obtains aromatic products mainly composed of aromatic aldehydes, aromatic carboxylic acids and aromatic formate esters in high yield.

[0008] The technical solution adopted by the present invention is:

[0009] Add lignin raw material, photocatalyst and organic solvent into a photoreactor (such as quartz photoreactor), fill the photoreactor with oxygen and / or air, and stir the lignin for oxidation and cracking reaction under the irradiation of light source; the lignin raw material is one of lignin model compound or lignin extracted by organic solvent; the photocatalyst is one or more of acridine organic molecule, rhodamine photosensitive molecule, eosin photosensitive molecule and cyano aromatic hydrocarbon molecule; the organic solvent is n-hexane, tetrahydrofuran, 1,4-dioxane, carbon tetrachloride, chloroform, 1,2-dichloromethane, 1,2-dichloroethane , acetone, acetonitrile, ethyl acetate, methyl formate, isopropanol or more; the mass concentration of the lignin raw material added to the photoreactor in the organic solvent is 1-50g / L, preferably 2-30g / L, more preferably 2-25g / L; the molar ratio of the photocatalyst to the lignin raw material in the photoreactor is 1-50%; the light source is a single wavelength LED light source in the range of 300-650nm, or a xenon lamp light source with a continuous wavelength range of 260-780nm; the photocatalytic reaction temperature is 0-80℃; the reaction time is 30-360 minutes.

[0010] The reaction raw materials are one or more of the following: lignin model compounds, lignin extracted from birch, pine, poplar, bamboo or plant straw (corn straw) by organic solvent, wherein the lignin model compounds are 2-phenoxy-1-phenylethanol, 1-(4-methoxyphenyl)-2-phenoxyethanol, 1-(3,4-dimethoxyphenyl)-2-phenoxyethanol, 4-methoxy-α-[(2-methoxyphenoxy)methyl]benzyl alcohol, 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethanol, 2-phenoxy-1-phenyl-1,3-propanediol, 1-(4-methoxyphenyl)-2-phenoxy-1,3-propanediol, 1-(4-methoxyphenyl)-2-phenoxy-1,3-propanediol, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol, 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)ethanol, 1-(4-methoxyphenyl)-2-(2,6-dimethoxyphenoxy)ethanol, 1-(3,4-dimethoxyphenyl)-2-(2,6-dimethoxyphenoxy)ethanol, 1-(3,4-dimethoxyphenyl)-2-(2,6-dimethoxyphenoxy)-1,3-propanediol, one of the model molecules of lignin β-O-4 oligomer;

[0011] The oxidant is oxygen and / or air, and the pressure in the photoreactor is 0.1-0.6 MPa, preferably 0.2-0.6 MPa, more preferably 0.3-0.5 MPa. The molar ratio of the photocatalyst to the raw material is preferably 2-30%, more preferably 5-25%; the reaction temperature is preferably 10-60°C, more preferably 30-60°C; the reaction time is preferably 45-180 minutes, more preferably 60-180 minutes.

[0012] The preferred reaction solvent is one or more of the organic solvents n-hexane, tetrahydrofuran, 1,4-dioxane, chloroform, dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, methyl formate, methanol, and isopropanol; more preferably, the reaction solvent is a mixed solvent of two solvents (a mixture of solvent A and solvent B), wherein solvent A is one of chloroform, dichloromethane, 1,2-dichloroethane, acetonitrile, acetone, and 1,4-dioxane, and solvent B is one of n-hexane, tetrahydrofuran, 1,4-dioxane, chloroform, dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, methyl formate, methanol, and isopropanol, and the volume percentage of solvent A in the mixed solvent is 10% to 90%, preferably 20% to 80%, and more preferably 30% to 70%. The product after the reaction is one, two, or more than three of aromatic aldehydes, aromatic carboxylic acids, aromatic carboxylic acid esters, and phenolic compounds.

[0013] This method uses organic molecular photocatalysts, which absorb in both the ultraviolet and visible light regions. The catalyst is excited under light conditions to produce electronic transitions, and electron transfer occurs between the excited state photocatalyst and the substrate molecule, so that the substrate molecule loses electrons and is oxidized. At the same time, the excited state catalyst that has gained electrons reacts with O2 molecules to activate O2 to produce active oxygen species. After the substrate is activated and oxidized, a free radical intermediate is formed, which in turn triggers the breakage of the C-C bond to form aromatic aldehydes and carbon-based free radical intermediates. Further oxidation can produce final products such as aromatic carboxylic acids and aromatic formate esters.

[0014] Both light and organic molecular catalysts are necessary conditions for the realization of this process. The greater the O2 pressure, the stronger the oxidation effect on the substrate molecules and the faster the reaction rate. The redox potential of the catalyst has a great influence on the catalytic process, and the reaction shows a significant solvent effect. The polarity, viscosity and aggregation state of the solvent all have a great influence on the reaction process.

[0015] This method has mild conditions, simple operation, a wide range of substrates, and the organic molecular catalysts used are cheap and readily available, have high catalytic activity, and show high selectivity for the target product. It is a new green method to achieve photocatalytic oxidative cracking of lignin.

[0016] The organic photocatalyst involved in the present invention is a homogeneous catalyst, which can be dissolved in an organic solvent and can fully contact with the reaction raw materials; at the same time, the method has mild reaction conditions and a simple process; through the synergistic effect of the catalyst and the specific organic solvent, side reactions such as excessive oxidation of intermediates and products are suppressed, thereby improving the selectivity and yield of the target aromatic product.

[0017] Compared with the existing method of preparing aromatic compounds by oxidative cracking of lignin, the present invention has the following advantages:

[0018] 1. The catalyst is a non-metallic organic molecule, which is cheap and readily available, easily soluble in organic solvents, and has good contact performance with the reaction raw materials;

[0019] 2. This type of catalyst has good response absorption in the ultraviolet-visible light region, has suitable redox ability, is easy to undergo electron transfer process, and has high catalytic activity for substrate molecules and oxygen;

[0020] 3. The reaction conditions are mild, and rapid conversion can be achieved at room temperature and normal pressure;

[0021] 4. The mixed solvent system accelerates the reaction rate of the substrate, inhibits the excessive oxidation side reaction of phenolic products, and improves the product selectivity and yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the gas chromatography analysis spectrum of the system after the reaction in Example 6. DETAILED DESCRIPTION

[0023] In order to further explain the present invention in detail, several specific implementation cases are given below, but the present invention is not limited to these embodiments.

[0024] The photocatalyst manufacturer information used in the following examples is as follows:

[0025]

[0026] The synthesis method of the lignin model compound used in the following examples is as follows. The experimental steps are as follows: phenol (73 mmol), potassium carbonate (10.4 g, 75 mmol) and acetone (150 mL) are added to a 350 mL round-bottom flask, replaced with Ar gas, and stirred at room temperature for 30 minutes. 2-bromoacetophenone (70 mmol) is added to the solution, stirred at room temperature for 16 hours, the suspension after the reaction is filtered to remove the solid, and the filtrate is distilled under reduced pressure to remove the solvent. The crude product is recrystallized with ethanol to obtain 2-phenoxy-1-phenylacetophenone.

[0027] 2-Phenoxy-1-phenyl acetone (10 mmol) was added to a 100 mL pressure bottle, and 50 mL of THF / water solvent (v / v=4 / 1) was added, followed by NaBH4 (0.45 g, 12 mmol) and stirred at room temperature. After reacting for 2 hours, an excess of saturated NH4Cl aqueous solution (30 mL) was added, followed by extraction with ethyl acetate (20 mL×3), and the organic phases were combined and dried over anhydrous sodium sulfate. The organic solvent was removed by rotary evaporation, and the obtained solid was vacuum dried at 45 degrees Celsius for 8 hours to obtain 2-phenoxy-1-phenyl ethanol.

[0028] 2-Phenoxy-1-phenylethanone (4mmol) and ethanol / acetone solvent (v / v=1 / 1, 10mL) were added to a 50mL round-bottom flask to dissolve, and then anhydrous potassium carbonate (0.6g, 4.3mmol) and a magnet were added, and stirred for 20 minutes at room temperature under an Ar atmosphere. Then 0.6mL of formaldehyde aqueous solution (36.5-38%, 7.3mmol) was added to the mixed solution, and after stirring at room temperature for 3 hours, the mixture was filtered to remove potassium carbonate, and then the solvent was removed by rotary evaporation. The solid product obtained after concentration was separated by silica gel column chromatography to obtain 2-phenoxy-1-phenyl-1,3-propanediol.

[0029] The synthesis methods of other model compounds are the same as above, except that the corresponding phenol is replaced by 2-methoxyphenol or 2,6-dimethoxyphenol, and / or 2-bromoacetophenone is replaced by 4-methoxy-α-bromoacetophenone or 3,4-dimethoxy-α-bromoacetophenone.

[0030]

[0031] The corresponding references for the synthesis method are ChemSusChem, 2014, 7, 3164–3171, ChemCatChem, 2015, 7, 401–404, and ACS Catal., 2013, 3, 3111-3122.

[0032] The preparation method of organic solvent extraction lignin used in the following examples: First, take 40g of ground pine wood powder and add it to 200mL 1,4-dioxane solvent, then add 2mol / L HCl solution (16mL), and heat and stir the mixture at 120 degrees Celsius and N2 atmosphere for 2.5 hours. After the mixture is cooled, filter it with a Buchner funnel, evaporate the collected liquid to remove the solvent and concentrate it, and add 200mL deionized water to precipitate it. The solid crude lignin obtained by precipitation is vacuum dried at 60 degrees Celsius. Then use acetone: methanol (volume ratio of 9:1, 10mL) to dissolve the dried crude lignin, and then add 200mL ether solvent to precipitate it. Use a Buchner funnel to filter and collect fine lignin solids and vacuum dry them at 60 degrees Celsius to obtain organic soluble pine lignin (~3.0g) after extraction. Other organic extraction lignin methods are the same, only the pine wood is replaced by bamboo, corn stalks, poplar or birch.

[0033] Comparative Example 1

[0034] In a 6mL quartz light reaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst and substrate feed ratio is 5%), 1mL dimethyl sulfoxide solvent (mass concentration of reaction raw materials in solvent is about 21g / L). The quartz light reaction tube is sealed, filled with 0.3MPa oxygen, and stirred under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction ends, the gas chromatography-mass spectrometry detection product is used, and the gas chromatography is quantitatively used, and the aromatic product yield is shown in Table 1.

[0035] Example 1

[0036] In a 6mL quartz light reaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst and substrate feed ratio is 5%), 1mL acetonitrile solvent (mass concentration of reaction raw materials in solvent is about 21g / L). The quartz light reaction tube is sealed, filled with 0.3MPa oxygen, and stirred under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction finishes, the gas chromatography-mass spectrometry detection product is used, and the gas chromatography is quantitatively used, and the aromatic product yield is shown in Table 1.

[0037] Example 2

[0038] In a 6mL quartz photoreaction tube, add 0.2mmol 2-phenoxy-1-phenylethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst and substrate feed ratio is 5%), 1mL acetone solvent (mass concentration of reaction raw materials in solvent is about 43g / L). The quartz photoreaction tube is sealed, filled with 0.3MPa oxygen, and stirred under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction ends, the product is detected by gas chromatography-mass spectrometry, and the yield of aromatic products is shown in Table 1 with gas chromatography quantitative analysis.

[0039] Example 3

[0040] In a 6mL quartz light reaction tube, add 0.05mmol 2-phenoxy-1-phenylethanol, 0.0025mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst and substrate feed ratio is 5%), 1mL dichloromethane solvent (mass concentration of reaction raw materials in solvent is about 10g / L). The quartz light reaction tube is sealed, filled with 0.3MPa oxygen, and stirred under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction ends, the gas chromatography-mass spectrometry detection product is used, and the gas chromatography is quantitatively used, and the aromatic product yield is shown in Table 1.

[0041] Example 4

[0042] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent 1,2-dichloroethane. Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0043] Example 5

[0044] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent chloroform. The quartz photoreaction tube is sealed, filled with 0.3MPa oxygen, and stirred under light irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 1.

[0045] Example 6

[0046] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0047] Example 7

[0048] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.1MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0049] Example 8

[0050] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.5MPa air, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0051] Example 9

[0052] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.001mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 1%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0053] Example 10

[0054] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 10%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0055] Embodiment 11

[0056] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.02mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 20%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0057] Example 12

[0058] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.05mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 50%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0059] Example 13

[0060] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 0 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0061] Embodiment 14

[0062] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 40 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0063] Embodiment 15

[0064] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 60 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0065] Example 16

[0066] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 80 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0067] Embodiment 17

[0068] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 30 minutes. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0069] Embodiment 18

[0070] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 1.5 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0071] Embodiment 19

[0072] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 4 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0073] Embodiment 20

[0074] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 1.

[0075] Table 1. Reaction results of photocatalytic lignin model oxidative depolymerization

[0076]

[0077]

[0078] Note: The values ​​in the table represent the product yield, which is the molar percentage of the product relative to the input substrate raw material. The rest are oxidation byproducts without CC bond oxidation cleavage, phenolic polymers caused by over-oxidation, small molecule degradation products such as formic acid / maleic acid, and other byproducts that have not been detected.

[0079] Table 1 Analysis: Comparative Example 1 uses a single solvent, dimethyl sulfoxide, and the substrate conversion is very small after 3 hours of reaction, and the target product is not detected; Compared with Comparative Example 1, the use of organic solvents with medium polarity and low viscosity (Examples 1-6) has a better reaction effect; On the basis of using a suitable solvent, as the O2 pressure increases, the reaction rate is accelerated (Examples 6-8); Comparative Example 6 and Example 9-12, as the amount of catalyst increases, the product yield also increases, but when the amount of catalyst is too much, it affects the light absorption and catalytic performance, and it is preferred that the photocatalyst and the reaction raw materials The molar ratio of the feed is 2 to 25%; comparing Example 6 with Examples 13 to 16, the reaction temperature has little effect on the product yield, and the target product with a higher yield can be obtained at room temperature, but too high a temperature may promote further oxidative polymerization side reactions of products such as phenol, resulting in a slight decrease in the yield; comparing Example 6 with Examples 17 to 20, as the reaction time is prolonged, the product yield gradually increases, and the reaction is close to complete after 1.5 hours. After the substrate is completely converted, too long a time will cause the phenyl formate product to be further hydrolyzed to phenol, and the phenol may be excessively oxidized and polymerized, reducing the yield of the target product.

[0080] Embodiment 21

[0081] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing acetonitrile: chloroform = 1:9, acetonitrile volume percentage is 10%). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0082] Embodiment 22

[0083] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing acetonitrile: chloroform = 1:4, acetonitrile volume percentage is 20%). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0084] Embodiment 23

[0085] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 4:1, acetonitrile volume percentage is 80%). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0086] Embodiment 24

[0087] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 9:1, acetonitrile volume percentage is 90%). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0088] Embodiment 25

[0089] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing 1,4-dioxane: n-hexane = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0090] Embodiment 26

[0091] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing chloroform: normal hexane = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0092] Embodiment 27

[0093] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing acetonitrile: normal hexane = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0094] Embodiment 28

[0095] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing 1,4-dioxane: acetonitrile = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0096] Embodiment 29

[0097] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing chloroform: tetrahydrofuran = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0098] Embodiment 30

[0099] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing chloroform: 1,2-dichloroethane = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0100] Embodiment 31

[0101] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing chloroform: isopropanol = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0102] Embodiment 32

[0103] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing chloroform: methanol = 1: 1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0104] Embodiment 33

[0105] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: tetrahydrofuran = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantitatively determined by gas chromatography. The yield of aromatic products is shown in Table 2.

[0106] Embodiment 34

[0107] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: methyl formate = 1: 1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0108] Embodiment 35

[0109] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: dichloromethane = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0110] Embodiment 36

[0111] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing 1,2-dichloroethane:tetrahydrofuran = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0112] Embodiment 37

[0113] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing 1,2-dichloroethane: acetonitrile = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0114] Embodiment 38

[0115] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetone: isopropanol = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantitatively determined by gas chromatography. The yield of aromatic products is shown in Table 2.

[0116] Embodiment 39

[0117] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), 1mL solvent (containing acetone: acetonitrile = 1: 1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry, and the gas chromatography is quantitatively used. The yield of aromatic products is shown in Table 2.

[0118] Embodiment 40

[0119] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 10-methyl-9-mesityl acridine perchlorate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0120] Embodiment 41

[0121] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 10-methyl-9-mesityl acridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 365nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0122] Embodiment 42

[0123] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 9-mesityl-2,7-dimethyl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0124] Embodiment 43

[0125] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol 3,6-di-tert-butyl-9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0126] Embodiment 44

[0127] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol rhodamine B catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 575nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0128] Embodiment 45

[0129] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol eosin Y catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 510nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0130] Embodiment 46

[0131] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol Eosin B catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0132] Embodiment 47

[0133] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol catalyst 9,10-dicyanoanthracene (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0134] Embodiment 48

[0135] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol catalyst 4,5-di(9-carbazolyl)-phthalonitrile (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile:chloroform=1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0136] Embodiment 49

[0137] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol catalyst 2,4,5,6-tetrakis (9-carbazolyl)-isophthalonitrile (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0138] Embodiment 50

[0139] In a 6mL quartz photoreaction tube, add 25mg of lignin β-O-4 oligomer model molecule, 2.3mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 1mL of solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa of oxygen, and stir the reaction under the irradiation of the light source. The wavelength of the light source is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic product is shown in Table 2.

[0140] Comparative Example 2

[0141] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol tris(2,2'-bipyridine) dichlororuthenium catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0142] Comparative Example 3

[0143] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenylethanol, 0.005mmol (4,4'-di-tert-butyl-2,2'-bipyridine) bis[(2-pyridyl)phenyl]iridium (III) hexafluorophosphate catalyst (catalyst to substrate feed ratio is 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 6 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 2.

[0144] Table 2. Reaction results of photocatalytic lignin model oxidative depolymerization

[0145]

[0146]

[0147] Note: The values ​​in the table represent the product yield, which is the molar percentage of the product relative to the input substrate raw material. The rest are oxidation byproducts without CC bond oxidation cleavage, phenolic polymers caused by over-oxidation, small molecule degradation products such as formic acid / maleic acid, and other byproducts that have not been detected.

[0148] Table 2 Analysis: Comparing Examples 1 to 6 with Examples 21 to 39, the solvent has a greater influence on the product yield, and two mixed organic solvents have a better effect than a single organic solvent. It is more preferred that the reaction solvent is a mixed solvent of two solvents (a mixture of solvent A and solvent B), wherein solvent A is one of chloroform, dichloromethane, 1,2-dichloroethane, acetonitrile, acetone, and 1,4-dioxane, and solvent B is one of n-hexane, tetrahydrofuran, 1,4-dioxane, chloroform, dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, methyl formate, methanol, and isopropanol, and the volume percentage of solvent A in the mixed solvent is 10% to 90%. Comparing Examples 40 to 49 with Control Examples 2 and 3, the common metal organic photocatalysts [Ru(bpy)3]Cl2 and [Ir(dtbbpy)(ppy)2]PF6 have poor catalytic effects on the oxidation and bond breaking of lignin model molecules (Control Examples 2 and 3). The acridine, rhodamine, eosin and cyanoaromatic organic molecules used in this application have good catalytic effects under ultraviolet-visible light illumination.

[0149] Embodiment 51

[0150] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-methoxyphenyl)-2-phenoxyethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0151] Embodiment 52

[0152] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(3,4-dimethoxyphenyl)-2-phenoxyethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0153] Embodiment 53

[0154] In a 6mL quartz photoreaction tube, add 0.1mmol 4-methoxy-α-[(2-methoxyphenoxy)methyl]benzyl alcohol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0155] Embodiment 54

[0156] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)ethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0157] Embodiment 55

[0158] In a 6mL quartz photoreaction tube, add 0.1mmol 2-phenoxy-1-phenyl-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0159] Embodiment 56

[0160] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-methoxyphenyl)-2-phenoxy-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0161] Embodiment 57

[0162] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0163] Embodiment 58

[0164] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0165] Embodiment 59

[0166] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0167] Embodiment 60

[0168] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)ethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0169] Embodiment 61

[0170] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(4-methoxyphenyl)-2-(2,6-dimethoxyphenoxy)ethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0171] Embodiment 62

[0172] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(3,4-dimethoxyphenyl)-2-(2,6-dimethoxyphenoxy)ethanol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0173] Embodiment 63

[0174] In a 6mL quartz photoreaction tube, add 0.1mmol 1-(3,4-dimethoxyphenyl)-2-(2,6-dimethoxyphenoxy)-1,3-propanediol, 0.01mmol 9-mesityl-10-phenylacridine tetrafluoroborate catalyst (catalyst to substrate feed molar ratio of 5%), and 1mL solvent (containing acetonitrile: chloroform = 1:1, V / V). Seal the quartz photoreaction tube, fill it with 0.3MPa oxygen, stir and react under light source irradiation, the light source wavelength is 455nm, the temperature is constant at 30 degrees Celsius, and the reaction is carried out for 3 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of aromatic products is shown in Table 3.

[0175] Embodiment 64

[0176] In a 100mL quartz photoreactor, add 100mg of organic solvent to extract pine lignin, 10mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 30mL of solvent (containing acetonitrile: chloroform = 1:1, V / V) (the mass concentration of the reaction raw materials in the solvent is about 3.3g / L). The quartz photoreactor is sealed, filled with 0.3MPa of oxygen, and stirred under the irradiation of the light source. A xenon lamp light source (with a wavelength range of 260 to 780nm after adding a filter) is used, and the temperature is kept constant at 60 degrees Celsius for 5 hours. After the reaction is completed, the product is detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic monomer product is shown in Table 3.

[0177] Embodiment 65

[0178] In a 100mL quartz photoreactor, 100mg of organic solvent was added to extract bamboo wood lignin, 10mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 30mL of solvent (containing acetonitrile: chloroform = 1:1, V / V). The quartz photoreactor was sealed, filled with 0.3MPa of oxygen, and stirred under the irradiation of a light source. A xenon lamp light source (with a wavelength range of 260 to 780nm after adding a filter) was used, and the temperature was kept constant at 60 degrees Celsius for 5 hours. After the reaction was completed, the product was detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic monomer product is shown in Table 3.

[0179] Embodiment 66

[0180] In a 100mL quartz photoreactor, 100mg of organic solvent was added to extract corn straw lignin, 10mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 30mL of solvent (containing acetonitrile: chloroform = 1:1, V / V). The quartz photoreactor was sealed, filled with 0.3MPa of oxygen, and stirred under the irradiation of a light source. A xenon lamp light source (with a wavelength range of 260 to 780nm after adding a filter) was used, and the temperature was kept constant at 60 degrees Celsius for 5 hours. After the reaction was completed, the product was detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic monomer product is shown in Table 3.

[0181] Embodiment 67

[0182] In a 100mL quartz photoreactor, 100mg of organic solvent extracted poplar lignin, 10mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 30mL of solvent (containing acetonitrile: chloroform = 1:1, V / V) were added. The quartz photoreactor was sealed, filled with 0.3MPa of oxygen, and stirred under the irradiation of a light source. A xenon lamp light source (with a wavelength range of 260 to 780nm after adding a filter) was used, and the temperature was kept constant at 60 degrees Celsius for 5 hours. After the reaction was completed, the product was detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic monomer product is shown in Table 3.

[0183] Embodiment 68

[0184] In a 100mL quartz photoreactor, 100mg of organic solvent-extracted birch lignin, 10mg of 9-mesityl-10-phenylacridine tetrafluoroborate catalyst, and 30mL of solvent (containing acetonitrile: chloroform = 1:1, V / V) were added. The quartz photoreactor was sealed, filled with 0.3MPa of oxygen, and stirred under the irradiation of a light source. A xenon lamp light source (with a wavelength range of 260 to 780nm after adding a filter) was used, and the temperature was kept constant at 60 degrees Celsius for 5 hours. After the reaction was completed, the product was detected by gas chromatography-mass spectrometry and quantified by gas chromatography. The yield of the aromatic monomer product is shown in Table 3.

[0185] Table 3. Reaction results of photocatalytic oxidative depolymerization of lignin

[0186]

[0187]

[0188] Note: The product yields of Examples 51 to 63 in the table represent the molar percentage relative to the substrate raw material, and the rest are oxidation byproducts without CC bond oxidation cleavage, phenolic polymers caused by over-oxidation, small molecule degradation products such as formic acid / maleic acid, and other byproducts that have not been detected. In Examples 64 to 68, there are many types of products obtained after the reaction using organic solvent to extract lignin as the raw material, which is related to the molecular structure of the lignin itself; since the theoretical maximum yield of the monomer aromatic aldehyde product after the lignin reaction is only 20-30%, but the use of nitrobenzene strong oxidant and the addition of strong base in the reaction system promote the oxidation reaction effect, the present invention uses O2 oxidant and no external additives to achieve selective oxidation and cracking of lignin under room temperature and light conditions; the remaining substances after the reaction are unreacted lignin raw materials, oligomer residues with undetected structures, and small molecule degradation products such as formic acid and maleic acid obtained by over-oxidation.

Claims

1. A method for photocatalytic oxidative cracking of lignin, characterized in that: Adding lignin raw materials, photocatalysts and organic solvents into a photoreactor (such as a quartz photoreactor), filling the photoreactor with oxygen and / or air, and stirring the lignin for oxidative cracking reaction under the irradiation of a light source; The lignin raw material is one of a lignin model compound and lignin extracted from an organic solvent; The photocatalyst is one or more of acridine organic molecules, rhodamine photosensitizing molecules, eosin photosensitizing molecules, and cyanoaromatic molecules; The organic solvent is one or more of n-hexane, tetrahydrofuran, 1,4-dioxane, carbon tetrachloride, chloroform, 1,2-dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, ethyl acetate, methyl formate, and isopropanol; The mass concentration of the lignin raw material added to the photoreactor in the organic solvent is 1 to 50 g / L, preferably 2 to 30 g / L, more preferably 2 to 25 g / L; The molar ratio of the photocatalyst to the lignin raw material in the photoreactor is 1 to 50%; The light source is a single wavelength LED light source in the range of 300 to 650 nm, or a xenon light source with a continuous wavelength range of 260 to 780 nm; The photocatalytic reaction temperature is 0 to 80° C. and the reaction time is 30 to 360 minutes.

2. The method according to claim 1, characterized in that: The reaction raw materials are one or more of the following: lignin model compounds, lignin extracted from birch, pine, poplar, bamboo or plant straw (corn straw) by organic solvent, wherein the lignin model compound is one of the compounds in the following table; 3. The method according to claim 1 or 2, characterized in that: The reaction route of the lignin model compound is:

4. The method according to claim 1 or 3, characterized in that: The photocatalyst is one or more of the following organic molecules:

5. The method according to claim 1, characterized in that: The oxidant is oxygen and / or air, and the pressure in the photoreactor is 0.1-0.6 MPa, preferably 0.2-0.6 MPa, and more preferably 0.3-0.5 MPa.

6. The method according to claim 1, characterized in that: The reaction solvent is preferably one or more of the organic solvents n-hexane, tetrahydrofuran, 1,4-dioxane, chloroform, dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, methyl formate, methanol, and isopropanol; The molar ratio of the photocatalyst to the raw material is preferably 2 to 30%, more preferably 5 to 25%.

7. The method according to claim 1, characterized in that: The preferred reaction temperature is 10 to 60°C, more preferably 30 to 60°C; The reaction time is preferably 45 to 180 minutes, more preferably 60 to 180 minutes.

8. The method according to claim 1 and claim 6, characterized in that: More preferably, the reaction solvent is a mixed solvent of two solvents (a mixture of solvent A and solvent B), wherein solvent A is one of chloroform, dichloromethane, 1,2-dichloroethane, acetonitrile, acetone, and 1,4-dioxane, and solvent B is one of n-hexane, tetrahydrofuran, 1,4-dioxane, chloroform, dichloromethane, 1,2-dichloroethane, acetone, acetonitrile, methyl formate, methanol, and isopropanol; the volume percentage of solvent A in the mixed solvent is 10% to 90%, preferably 20% to 80%, and more preferably 30% to 70%; The products after the reaction are one, two or more than three of aromatic aldehydes, aromatic carboxylic acids, aromatic carboxylic acid esters and phenolic compounds.

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