Method for preparing renewable phenolic products through reaction-separation coupled catalytic degradation of biomass

Abstract

The invention discloses a method for preparing a renewable phenol product by reaction-separation coupled catalytic degradation of biomass, which comprises the following steps: putting a biomass raw material, a high-boiling-point solvent and a catalyst into a reaction kettle of a segmented temperature control packed column, starting stirring, sealing the reaction kettle and heating, then filling a low-boiling-point solvent into the reaction kettle, and carrying out reaction-separation coupled catalytic degradation on the low-boiling-point solvent to obtain the renewable phenol product. A low-boiling-point product (mainly a monophenol product) generated by catalytic degradation of biomass and low-boiling-point solvent steam enter a segmented temperature control packed column together, so that step-by-step separation of the monophenol product is realized. The low-boiling-point product and the solvent enter a collecting tank, the low-boiling-point solvent is subjected to distillation separation based on waste heat and an auxiliary heating system, cyclic utilization of the low-boiling-point solvent is achieved through a condensing device, and the monophenol product is left in the collecting tank. According to the method, a distillation / rectification separation process is combined with biomass catalytic degradation, the product selectivity is improved through selective separation of the segmented temperature control packed column, the mass fraction of the monophenol product can reach 80% or above, and the yield is not lower than 40%.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass deep processing, and specifically relates to a method for preparing renewable phenolic products by reaction-separation coupled catalytic degradation of biomass. Background Art

[0002] As a renewable aromatic resource that can be obtained on a large scale from nature, lignin shows great potential in the process of catalytic hydrocracking and can be used to produce sustainable aromatic compounds / fuels. The catalytic hydrocracking of lignin meets the needs of atomic economy and can generate a variety of value-added products from by-products of the agricultural and forestry industries. The structure of the lignin obtained after separation has changed, and some CO bonds have been replaced by more stable CC bonds. Using it for catalytic degradation often has problems such as low monomer products. Therefore, the lignin first strategy of preferentially treating and utilizing lignin has significant advantages in the conversion and utilization of lignin and the efficiency of the hierarchical conversion and utilization of all components of biomass.

[0003] The selective cleavage of CO bonds and CC bonds between phenolic monomer units in lignin is the key catalytic process of catalytic hydrogenolysis in the lignin priority strategy, and its feasibility has been confirmed by the reactions of multiple lignin phenolic model compounds. A common strategy for catalysts used in such reactions is to load active metals (such as ruthenium, nickel, palladium, platinum, etc.) on acidic carriers (such as zeolites, alumina, zirconyl sulfate, etc.). The Joint Bioenergy Research Institute of the United States used Ru / C as a catalyst and isopropanol as a hydrogen donor solvent to catalyze the degradation of lignin separated from low eutectic solvents, and the yield of mixed phenol monomers was less than 27% (DOI: 10.1039 / C6GC02473D); Beijing University of Chemical Technology used platinum loaded on a variety of alkaline carriers as a catalyst to catalyze the depolymerization of alkaline lignin, and the yield of single phenols was 10-30% (DOI: 10.1007 / s11244021014594); the patent "A catalyst for in-situ hydrogenolysis of aromatic ether bonds, its preparation method and application" (CN114029070A) uses a highly dispersed NiRu alloy catalyst for in-situ hydrogenolysis of lignin. Under optimal conditions, the methanol-soluble matter in the product is close to 60%, and the content of monophenols and diphenols in the total product is greater than 70%; the patent "A method for selective hydrogenolysis of lignin catalyzed by nickel-based materials supported by zirconium phosphate" (CN108558608A) uses nickel-based materials supported by zirconium phosphate to catalyze the selective hydrogenolysis of lignin, with a lignin conversion rate of more than 85.1% and a monophenol yield of more than 13.0%.

[0004] Although many studies have demonstrated the potential of lignin to prepare renewable aromatic chemicals, there are still major challenges in the actual industrial application of this technology. Low monomer product yield and poor product selectivity are common problems faced by this type of process. In order to achieve a competitive economic efficiency level, the conversion rate of lignin and product selectivity still need to be further improved. Summary of the invention

[0005] To solve the above problems, the present invention introduces the idea of ​​reaction-separation coupling in the traditional biomass catalytic conversion process, continuously removes the monophenol products in the reaction system through hot solvent distillation, promotes the catalytic degradation of lignin in biomass, thereby maximizing the monomer yield, and improves product selectivity based on regulating the temperature distribution of the separation section.

[0006] In order to achieve the above technical objectives, the present invention adopts the following technical solutions: A method for preparing renewable phenolic products by reaction-separation coupled catalytic degradation of biomass, specifically comprising the following steps: Step 1), placing the biomass raw material, the high boiling point solvent and the catalyst in a reactor of a reaction-separation coupling device, the mass ratio of the volume of the high boiling point solvent to the biomass raw material is 1-10 mL / g, and the mass ratio of the catalyst to the biomass raw material is (0.01-0.1):1; Step 2), start the reactor to stir, seal the reactor and heat it to 170-260°C, then fill the reactor with a low boiling point solvent, and adjust the pressure control valve at the top of the segmented temperature control packing column to stabilize the system pressure. The flow rate of the low boiling point solvent is 3-10 mL / min, and the system pressure is controlled at 1-4 MPa; Step 3), the low boiling point products (mainly monophenol products) produced by the catalytic degradation of biomass enter the segmented temperature-controlled packing column together with the low boiling point solvent vapor, and the monophenol products are separated step by step through the segmented temperature control setting. The temperature control range of the segmented temperature-controlled packing column is 130-200°C; Step 4), the low boiling point product and the solvent pass through the pressure control valve into the collection tank, the low boiling point solvent is distilled and separated based on the waste heat and the auxiliary heating system, and the low boiling point solvent is recycled through the condenser, and the monophenol product remains in the collection tank.

[0007] Furthermore, the reaction-separation coupling device includes a reactor, a collecting tank, a water cooler, a solvent tank and a preheating furnace. A segmented temperature-controlled packing column is connected in series on the top of the reactor. The top outlet of the segmented temperature-controlled packing column is connected to the inlet of the collecting tank through a pipeline and a pressure control valve arranged on the pipeline. The collecting tank is provided with a gas outlet and a liquid outlet. The gas outlet is connected to the inlet of the water cooler through a pipeline, the outlet of the water cooler is connected to the inlet of the solvent tank through a pipeline, the outlet of the solvent tank is connected to the inlet of the solvent pump through a pipeline, the outlet of the solvent pump is connected to the inlet of the preheating furnace through a pipeline, and the outlet of the preheating furnace is connected to the bottom of the reactor through a pipeline.

[0008] Furthermore, a bypass is provided on the connecting pipeline between the preheating furnace and the reactor, and the bypass is connected to a hydrogen / nitrogen bottle.

[0009] Furthermore, the segmented temperature-controlled packing column is a three-stage temperature-controlled packing column, and each segment of the packing column is provided with a thermometer.

[0010] Furthermore, in step 1), the high boiling point solvent is any one of ethylene glycol, glycerol, diethylene glycol, N,N-dimethylformamide, N-methyl-2-pyrrolidone, or a mixed solvent of two or more thereof in any proportion.

[0011] Furthermore, in step 2), the low boiling point solvent is any one of cyclopentane, cyclohexane, methanol, ethanol, propanol, isopropanol, acetone, and ether, or a mixed solvent of two or more in any proportion.

[0012] Furthermore, in step 1), the biomass raw material is any one of straw, wood chips, bamboo chips, peanut shells, rice husks and corn cobs, or a mixture of two or more of them in any proportion.

[0013] Furthermore, in step 1), the catalyst is at least one of Ru / HZSM-5 and Ru / tungsten oxide-zirconium oxide, the Ru content in Ru / HZSM-5 is 3-10% of the mass of HZSM-5, the Ru content in Ru / tungsten oxide-zirconium oxide is 3-10% of the mass of tungsten oxide-zirconium oxide, and the mass of W accounts for 7-14% of the mass of zirconium oxide.

[0014] Preferably, the preparation process of the catalyst Ru / HZSM-5 is as follows: HZSM-5 molecular sieve is placed in water, and an appropriate amount of RuCl 3Dissolve in the aforementioned water containing molecular sieves, add commercial concentrated ammonia water to adjust the pH to 8-10, stir at room temperature for 1-3 hours, let stand for 10-15 hours, filter, and place the resulting precipitate in a muffle furnace at 200-250 ° C for 1-3 hours, and reduce it with hydrogen at 180-220 ° C in a tubular furnace for 1-3 hours to obtain a Ru / HZSM-5 catalyst, wherein the Ru content is 3-10% of the carrier mass, and the mass ratio of the HZSM-5 molecular sieve to the volume of water is 1 g: (4-6) mL.

[0015] The preparation process of the catalyst Ru / tungsten oxide-zirconium oxide is as follows: put zirconium oxide in water, weigh an appropriate amount of ammonium metatungstate and dissolve it in the water containing zirconium oxide, add commercial concentrated ammonia water to adjust the pH to 9-11, stir at 50-70°C for 2-4 hours, let stand for 10-15 hours, filter, take the precipitate and put it in a muffle furnace, calcine at 500-600°C for 1-3 hours to obtain the carrier tungsten oxide-zirconium oxide, in which the mass of W accounts for 7-14% of the mass of zirconium oxide, which is determined by the amount of ammonium metatungstate weighed, and the mass ratio of zirconium oxide to water is 1 g: (4-6) mL. Put tungsten oxide-zirconium oxide in water, weigh an appropriate amount of RuCl 3 Dissolve in the aforementioned water containing tungsten oxide-zirconium oxide, add commercial concentrated ammonia water to adjust the pH to 8-10, stir at room temperature for 1-3 hours, and stand for 10-15 hours. Filter by suction, calcine the resulting precipitate in a muffle furnace at 200-250°C for 1-3 hours, and reduce it in a tubular furnace at 180-220°C with hydrogen for 1-3 hours to obtain a Ru / tungsten oxide-zirconium oxide catalyst, wherein the Ru content is 3-10% of the carrier mass, and the mass ratio of tungsten oxide-zirconium oxide to water is 1 g: (4-6) mL.

[0016] Furthermore, the monophenol is guaiacol, eugenol, syringol, phenol and its derivatives.

[0017] The process design features of the present invention are as follows: the continuous reaction-separation device is a reactor connected in series with segmented temperature-controlled packing columns; during the reaction process, the high-boiling-point solvent is retained in the reactor, and the low-boiling-point solvent can be recycled through waste heat distillation-cooling.

[0018] The present invention uses the reaction-separation coupling idea to strengthen the biomass catalytic degradation process, continuously removes the monophenol product through hot solvent distillation, promotes the conversion of lignin to monomer products, and realizes the selective separation of phenolic monomers with the help of segmented temperature-controlled packing columns to improve product selectivity. To achieve this goal, the present invention innovatively adopts a two-liquid phase solvent system, in which a high-boiling-point solvent is used as a solvent medium for the catalytic degradation reaction, and a low-boiling-point solvent is used as a hydrogen source and a carrier gas for separating specific degradation products. During the reaction process, the high-boiling-point solvent stays in the reactor part, while the low-boiling-point solvent vapor carries part of the degradation light product through the segmented temperature-controlled packing column and enters the collection tank to realize product collection and solvent recovery. Compared with the traditional reaction process, the reaction-separation coupling proposed by the present invention has a higher monophenol yield and product selectivity, significantly improves the utilization rate of the lignin component, and has a certain driving effect on improving the economic benefits of biomass catalytic degradation related processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a schematic diagram of the reaction-separation coupling device; In the figure: 1-reactor; 2-section temperature control packing column; 3-pressure control valve; 4-collection tank; 5-water cooler; 6-solvent tank; 7-solvent pump; 8-hydrogen / nitrogen cylinder; 9-preheating furnace; T a 、T b It is a cascade temperature control device for the reactor; Figure 2 The GCMS total ion chromatogram of the straw catalytic hydrogenolysis products; Figure 3 This is the GCMS total ion chromatogram of the products of catalytic hydrogenolysis of poplar sawdust. DETAILED DESCRIPTION

[0020] 1. Experimental Materials The catalyst used in the present invention is Ru / HZSM-5, Ru / tungsten oxide-zirconium oxide, and the preparation method of the catalyst is as follows: Catalyst Ru / HZSM-5: 10 g HZSM-5 molecular sieve was placed in 50 mL water, and an appropriate amount of RuCl 3 Dissolve in the aforementioned water containing molecular sieves, add commercial concentrated ammonia water dropwise to adjust the pH to 9, stir at room temperature for 2 hours, and let stand for 12 hours. Filter by suction, calcine the resulting precipitate in a muffle furnace at 220°C for 2 hours, and reduce it with hydrogen at 200°C in a tubular furnace for 2 hours to obtain a Ru / HZSM-5 catalyst, wherein the Ru content is 3-10% of the carrier mass, specifically weighing RuCl 3 The quality of the decision.

[0021] Catalyst Ru / tungsten oxide-zirconium oxide, take 10g of zirconium oxide and place it in 50mL of water, weigh an appropriate amount of ammonium metatungstate and dissolve it in the water containing zirconium oxide, add commercial concentrated ammonia water dropwise to adjust the pH to 10, stir at 60℃ for 3 hours, and let stand for 12 hours. Filter, take the white precipitate and place it in a muffle furnace, calcine at 550℃ for 2 hours to obtain the carrier tungsten oxide-zirconium oxide, in which the mass of W accounts for 7~14% of the mass of zirconium oxide, which is determined by the amount of ammonium metatungstate weighed. Take 10g of tungsten oxide-zirconium oxide and place it in 50mL of water, weigh an appropriate amount of RuCl 3 Dissolve in water, add commercial concentrated ammonia water dropwise to adjust the pH to 9, stir at room temperature for 2 hours, and let stand for 12 hours. Filter by suction, calcine the resulting precipitate in a muffle furnace at 220°C for 2 hours, and reduce it with hydrogen at 200°C in a tube furnace for 2 hours to obtain a Ru / tungsten oxide-zirconium oxide catalyst, wherein the Ru content is 3-10% of the carrier mass, specifically weighing RuCl 3 The quality of the decision.

[0022] The biomass raw materials used in the present invention are straw powder and poplar sawdust. The yield of monophenol product is calculated by dividing the mass of monophenol product by the mass of lignin in the biomass raw materials. The lignin content in the straw powder is 19.1%, and the lignin content in the poplar sawdust is 28%.

[0023] 2. Experimental Methods The monophenol content of the product was determined by gas chromatography, mass spectrometry and comprehensive two-dimensional gas chromatography. The internal standard n-dodecane was added during the determination process to achieve semi-quantitative analysis.

[0024] 3. Experimental Setup like Figure 1 As shown, the reaction-separation coupling device includes a reactor 1, a collecting tank 4, a water cooler 5, a solvent tank 6 and a preheating furnace 9. A segmented temperature-controlled packing column 2 is connected in series at the top of the reactor 1. The top outlet of the segmented temperature-controlled packing column 2 is connected to the inlet of the collecting tank 4 through a pipeline and a pressure control valve 3 arranged on the pipeline. The collecting tank 4 is provided with a gas outlet and a liquid outlet. The liquid outlet serves as the outlet of the monophenol product. The gas outlet is connected to the inlet of the water cooler 5 through a pipeline. The outlet of the water cooler 5 is connected to the inlet of the solvent tank 6 through a pipeline. The outlet of the solvent tank 6 is connected to the inlet of the solvent pump 7 through a pipeline. The outlet of the solvent pump 7 is connected to the inlet of the preheating furnace 9 through a pipeline. The outlet of the preheating furnace 9 is connected to the bottom of the reactor 1 through a pipeline. A bypass for leak detection is provided on the connecting pipeline between the preheating furnace 9 and the reactor 1, and the bypass is connected to a hydrogen / nitrogen cylinder 8. The segmented temperature-controlled packing column 2 is a three-stage temperature-controlled packing column, and each segment of the packing column is provided with a thermometer; temperature control meters are provided inside the reactor 1 and on the outer wall of the reactor 1, and the inner and outer temperature control meters adopt a cascade temperature control method to accurately control the reactor temperature.

[0025] Embodiment 1: 5 g of straw powder (100-200 mesh), 30 mL of glycerol, and 0.5 g of Ru / H-ZSM5 (Ru content is 3% of the mass of HZSM-5) are placed in a continuous reaction-separation device (reactor 1 connected in series with a segmented temperature-controlled packing column 2, 100 mL); the reactor 1 is started for stirring, the reactor 1 is sealed and heated to 220°C, and then a low boiling point solvent (isopropanol) is charged into the reactor 1 through a solvent pump 7, and the pressure control valve 3 at the top of the segmented temperature-controlled packing column 2 is adjusted to stabilize the system pressure, the low boiling point solvent flow rate is 5 mL / min, and the system pressure (the system consisting of the reactor and the segmented temperature-controlled packing column) is controlled at 1.5 MPa. The low-boiling-point products (mainly monophenol products) produced by the catalytic degradation of biomass enter the segmented temperature-controlled packing column 2 together with the low-boiling-point solvent vapor. Based on the segmented temperature control setting, the monophenol products are separated step by step. The three-stage temperature control of the packing column is T1=200°C, T2=175°C and T3=150°C from bottom to top. During the reaction, the low-boiling-point products (monophenol products) and the solvent pass through the pressure control valve 3 and enter the collection tank 4. The low-boiling-point solvent is distilled and separated based on the waste heat and auxiliary heating system. The low-boiling-point solvent vapor is discharged from the top of the collection tank 4 and enters the water cooler 5. The low-boiling-point solvent is recycled through the water cooler 5, and the product (monophenol product) is retained in the collection tank 4.

[0026] After 3 hours of reaction, the reactor 1 and the segmented temperature-controlled packed column 2 were closed for heating. When the temperature was lower than 100°C, the solvent pump 7 was adjusted to release the system pressure, and the temperature was allowed to drop to room temperature. The collecting tank 4 was opened and the product in the collecting tank was dissolved with ethyl acetate (3 times, 5 mL of ethyl acetate each time). The ethyl acetate solution was rotary evaporated to obtain 0.67 g of catalytic degradation product and monophenol product ( Figure 2 The content of compound 1-7 in the total product was calculated by external standard method using standard substance) with a proportion of 67.54% and a mass of monophenol product of 0.44 g, and a yield of 47.63% ( Figure 2 The low boiling point solvent overflowing from the top of the collecting tank 4 is recovered into the solvent tank 6 through the water cooler 5 and directly used for the next reaction.

[0027] As a comparison, 5 g straw powder was used as raw material, 30 mL glycerol, 30 mL isopropanol as solvent, and 0.5 g Ru / H-ZSM5 (Ru content was 3 wt.%) as catalyst was reacted in a reactor (220 ° C, 6 h), and 1.78 g of catalytic degradation product and monophenol product (attached Figure 2 The mass proportion of compounds 2, 3, and 5 in the total product is 6.36%, the mass of the monophenol product is 0.11 g, and the yield is 11.91%.

[0028] Embodiment 2: The 30 mL of glycerol in Example 1 was replaced with 30 mL of N-methyl-2-pyrrolidone, and other conditions remained unchanged, and 0.52 g of catalytic degradation product and monophenol product ( Figure 2 The mass proportion of compound 1-4) in the total product is 64.0%, the mass of the monophenol product is 0.33g, and the yield is 35.03%.

[0029] Embodiment 3: The low boiling point solvent (isopropanol) in Example 1 was replaced with methanol, and other conditions remained unchanged. 0.24 g of catalytic degradation product and monophenol product ( Figure 2 The mass proportion of compound 1-7) in the total product is 65.1%, the mass of the monophenol product is 0.16g, and the yield is 16.45%.

[0030] Embodiment 4: The catalyst in Example 1 was replaced with Ru / WO x / ZrO 2 (Ru content is 3% of the mass of tungsten oxide-zirconium oxide, and the mass of W accounts for 14% of the mass of zirconium oxide). Other conditions remain unchanged, and 0.71g of catalytic degradation product and monophenol product ( Figure 2 The mass proportion of compound 1-7) in the total product is 66.54%, the mass of monophenol product is 0.47g, and the yield of monophenol product is 49.73%.

[0031] For comparison, 5 g straw powder was used as raw material, 30 mL glycerol and 30 mL isopropanol were used as solvents, and 0.5 g Ru / WO x / ZrO 2 (Ru content is 3% of the mass of tungsten oxide-zirconium oxide, and the mass of W accounts for 14% of the mass of zirconium oxide) as catalyst in a reactor (220℃, 6h), 1.84g of catalytic degradation product and monophenol product ( Figure 2 The proportion of compounds 2, 3, and 5 in the total product was 5.47%, the mass of the monophenol product was 0.10 g, and the yield was 10.59%.

[0032] Embodiment 5: The reactants in Example 1 were replaced with poplar sawdust (100-200 mesh), and other conditions remained unchanged. 1.08 g of catalytic degradation product and monophenol product ( Figure 3 Compound 4-15) accounts for 68.85% of the total product, the mass of the monophenol product is 0.73g, and the yield is 49.57%.

[0033] As a comparison, 5 g of poplar sawdust was used as raw material, 30 mL of glycerol, 30 mL of isopropanol as solvent, and 0.5 g of Ru / H-ZSM5 as catalyst were reacted in a reactor (220 °C, 6 h), and 2.08 g of catalytic degradation product and monophenol product ( Figure 3 The proportion of compound 4-15 in the total product was 8.85%, the mass of monophenol product was 0.18 g, and the yield was 12.27%.

Claims

1. A method for preparing renewable phenolic products by reaction-separation coupled catalytic degradation of biomass, characterized in that: The specific steps include: Step 1), placing the biomass raw material, the high boiling point solvent and the catalyst in a reactor of a reaction-separation coupling device, the mass ratio of the volume of the high boiling point solvent to the biomass raw material is 1-10 mL / g, and the mass ratio of the catalyst to the biomass raw material is (0.01-0.1):1; Step 2), start the reactor to stir, seal the reactor and heat it to 170-260°C, then fill the reactor with a low boiling point solvent, and adjust the pressure control valve at the top of the segmented temperature control packing column to stabilize the system pressure. The flow rate of the low boiling point solvent is 3-10 mL / min, and the system pressure is controlled at 1-4 MPa; Step 3), the low boiling point products produced by the catalytic degradation of biomass and the low boiling point solvent vapor enter the segmented temperature-controlled packing column together, and the monophenol products are separated step by step through the segmented temperature control setting. The temperature control range of the segmented temperature-controlled packing column is 130-200°C; Step 4), the low boiling point product and the solvent pass through the pressure control valve into the collection tank, the low boiling point solvent is distilled and separated based on the waste heat and the auxiliary heating system, and the low boiling point solvent is recycled through the condenser, and the monophenol product remains in the collection tank.

2. The method according to claim 1, characterized in that: The reaction-separation coupling device comprises a reactor, a collecting tank, a water cooler, a solvent tank and a preheating furnace. A segmented temperature-controlled packing column is serially connected on the top of the reactor. The top outlet of the segmented temperature-controlled packing column is connected to the inlet of the collecting tank through a pipeline and a pressure control valve arranged on the pipeline. The collecting tank is provided with a gas outlet and a liquid outlet. The gas outlet is connected to the inlet of the water cooler through a pipeline. The outlet of the water cooler is connected to the inlet of the solvent tank through a pipeline. The outlet of the solvent tank is connected to the inlet of a solvent pump through a pipeline. The outlet of the solvent pump is connected to the inlet of the preheating furnace through a pipeline. The outlet of the preheating furnace is connected to the bottom of the reactor through a pipeline.

3. The method according to claim 1, characterized in that: In step 1), the high boiling point solvent is any one of ethylene glycol, glycerol, diethylene glycol, N,N-dimethylformamide, and N-methyl-2-pyrrolidone, or a mixed solvent of two or more of them in any proportion.

4. The method according to claim 1, characterized in that: In step 2), the low boiling point solvent is any one of cyclopentane, cyclohexane, methanol, ethanol, propanol, isopropanol, acetone, and ether, or a mixed solvent of two or more in any proportion.

5. The method according to claim 1, characterized in that: In step 1), the biomass raw material is any one of straw, wood chips, bamboo chips, peanut shells, rice husks and corn cobs, or a mixture of two or more of them in any proportion.

6. The method according to claim 1, characterized in that: In step 1), the catalyst is at least one of Ru / HZSM-5 and Ru / tungsten oxide-zirconium oxide, the Ru content in Ru / HZSM-5 is 3-10% of the mass of HZSM-5, the Ru content in Ru / tungsten oxide-zirconium oxide is 3-10% of the mass of tungsten oxide-zirconium oxide, and the mass of W accounts for 7-14% of the mass of zirconium oxide.

7. The method according to claim 2, characterized in that: A bypass is provided on the connecting pipeline between the preheating furnace and the reactor, and the bypass is connected to the hydrogen / nitrogen bottle.

8. The method according to claim 1 or 2, characterized in that: The segmented temperature-controlled packing column is a three-stage temperature-controlled packing column, and each segment of the packing column is provided with a thermometer.

9. The method according to any one of claims 1 to 7, characterized in that: The monophenols are guaiacol, eugenol, syringol, phenol and their derivatives.

Images