Method for oxidative depolymerization of beta-O-4 lignin model compound based on electrochemical continuous flow reactor

Abstract

The invention discloses a method for oxidative depolymerization of a beta-O-4 lignin model compound based on an electrochemical continuous flow reactor, the reactor comprises an anode plate, a cathode plate and a snakelike reaction channel located between the anode plate and the cathode plate, and the anode plate and the cathode plate are respectively connected with an anode and a cathode of a power supply; the method comprises the following steps: dissolving a beta-O-4 lignin model compound and tetraethylammonium perchlorate in a mixed solvent of acetonitrile and methanol to obtain a homogeneous solution, continuously introducing the homogeneous solution into a snakelike reaction channel of a reactor, and applying current to carry out an electrolytic reaction to prepare an aromatic compound; continuous depolymerization of the beta-O-4 lignin model compound can be achieved, products can be discharged in time, over-reaction can be relieved, enlargement is easy, meanwhile, due to the narrow gap and the large specific surface area of the reactor, the electrolyte concentration and the electrolytic tank pressure can be remarkably reduced, single-time conversion is achieved, the reaction rate is remarkably increased, the products are mainly benzaldehyde dimethyl acetal, and the cost is low. And the conversion rate and the yield are relatively high.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical catalytic biomass value-added, and in particular to a method for oxidative depolymerization of a β-O-4 lignin model compound based on an electrochemical continuous flow reactor. Background Art

[0002] Lignin is the largest source of renewable aromatic compounds, and recovering aromatic compounds from lignin is an important scientific goal. Electrochemical methods utilize renewable electrical energy to convert substrates into target compounds, eliminating the need for the specific oxidants and reductants used in traditional chemical methods. Furthermore, selective substrate conversion can be achieved by manipulating electrodes, electrolytes, electrode potential (current), and electrolysis methods. Electrochemical methods provide a gentle, green, and efficient pathway for the efficient depolymerization and conversion of lignin.

[0003] Lignin has a complex structure and produces numerous depolymerization products, making analysis difficult. To improve depolymerization efficiency and refine depolymerization strategies, research into the depolymerization mechanism of lignin is often necessary. Since β-O-4 bonds are the most abundant linking bonds in lignin, studying the selective cleavage of CO and CC bonds using β-O-4 model compounds is highly instructive for efficient lignin depolymerization. Furthermore, β-O-4 model compounds are simple in structure, easy to synthesize, and their products are easily isolated and identified, making them widely used in mechanistic studies of lignin depolymerization. Laboratory studies on the electrochemical depolymerization of lignin often use intermittent electrolysis, i.e., electrolysis experiments are conducted in beakers or H-type electrolytic cells. This method offers advantages such as simple setup and ease of operation, but also has disadvantages such as low mass transfer rates, slow reaction rates, high cell pressures, and difficulty in scaling up.

[0004] Benzaldehyde dimethyl acetal is stable under neutral or alkaline conditions and can be hydrolyzed to benzaldehyde under acidic conditions. Compared to benzaldehyde, it is less susceptible to oxidation and can be used to protect the aldehyde group. It is an important organic intermediate widely used in flavors, pharmaceuticals, and other fields. Compared with traditional acid-catalyzed synthesis methods, the electrochemical continuous flow process for producing aromatic acetals from lignin is expected to be more environmentally friendly, efficient, and economical. Summary of the Invention

[0005] The invention provides a method for oxidative depolymerization of a beta-O-4 lignin model compound based on an electrochemical continuous flow reactor.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for oxidative depolymerization of a β-O-4 lignin model compound based on an electrochemical continuous flow reactor, characterized in that the electrochemical continuous flow reactor includes an anode plate, a cathode plate, and a serpentine reaction channel located between the anode plate and the cathode plate, wherein the anode plate and the cathode plate are respectively connected to the positive and negative electrodes of a power supply;

[0008] A β-O-4 lignin model compound and tetraethylammonium perchlorate are dissolved in a mixed solvent to obtain a homogeneous solution, which is continuously introduced into a serpentine reaction channel of an electrochemical continuous flow reactor, and an electric current is applied to perform an electrolysis reaction to obtain an aromatic compound; the mixed solvent is acetonitrile and methanol.

[0009] The electrochemical continuous flow reactor used in the present invention consists of two pieces of perforated stainless steel (a base and a cover), a graphite electrode, a nickel sheet electrode, a piece of soft silicone, a fluororubber gasket, a polytetrafluoroethylene sheet with a serpentine channel, and an electrode placement chamber made of polytetrafluoroethylene.

[0010] The two pieces of stainless steel with holes and the electrode placement chamber have the same overall size. The four corners of the electrode placement chamber are treated to avoid airflow to facilitate milling and electrode placement. During assembly, use a three-combination hexagonal knurled screw (flat washer and spring washer) and a plum handle nut (through hole) to tighten together. Soft silicone is located between the graphite electrode and the stainless steel cover, acting as a buffer and insulator. The electrode is connected to the power wire through a conductive copper foil with a thickness of 0.05 mm. The copper foil is located on the back of the electrode and is not in contact with the electrolyte. The thickness of the polytetrafluoroethylene sheet with a serpentine channel and the shape of the channel are variable. The thickness depends on the flatness of the electrode surface. Under current conditions, the thickness can range from 0.1 mm to 1 mm.

[0011] The continuous flow electrochemical reaction device also includes a power supply that can provide a constant current, a peristaltic pump that provides power for the flow of electrolyte and its matching peristaltic pump tube, and a storage bottle for containing the electrolyte before and after the electrolysis reaction.

[0012] Preferably, the flow rate of the homogeneous solution is 100-800 μL / min, more preferably 100 μL / min-200 μL / min. The current density is 2.5-25 mA / cm 2 .

[0013] Preferably, the current is 20-160 mA, more preferably 30-50 mA.

[0014] Preferably, the thickness of the serpentine reaction channel is 0.1-1.0 mm, preferably 0.25-0.5 mm.

[0015] Preferably, the volume ratio of acetonitrile to methanol is 1:3-5:1.

[0016] Preferably, the volume ratio of acetonitrile to methanol is 1:3-3:1, preferably 1 / 1.

[0017] Preferably, the anode plate is a graphite electrode; the cathode plate is a nickel sheet electrode, a stainless steel electrode, a platinum electrode, a copper electrode or a silver electrode.

[0018] Preferably, the β-O-4 lignin model compound includes one or more of 2-phenoxy-1-phenylethanol, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-phenoxyacetophenone and 2-phenoxy-1-phenylethane.

[0019] Preferably, the molar volume ratio of tetraethylammonium perchlorate to the mixed solvent is 10 -4 -1.5×10 -3 mol: 20 mL; the molar ratio of the lignin dimer model compound to tetraethylammonium perchlorate is 2.5:(1-15).

[0020] Preferably, the aromatic compounds include benzaldehyde, methyl benzoate, benzaldehyde dimethyl acetal, 4,4-dimethoxy-2,5-cyclohexadien-1-one, and 4-methoxyphenol, wherein the yield of benzaldehyde dimethyl acetal can reach up to 52%.

[0021] The invention provides a method for electrochemically depolymerizing a β-O-4 lignin model compound 2-phenoxy-1-phenylethanol to generate benzaldehyde dimethyl acetal. Specifically, an electrochemical continuous flow reactor is used, reaction channels and electrodes with a certain shape and thickness are selected, 2-phenoxy-1-phenylethanol and tetraethylammonium perchlorate are dissolved in a mixed solvent of acetonitrile and methanol in a certain proportion to prepare a homogeneous solution, a power supply provides a current of a certain intensity, and a peristaltic pump is used to adjust the rotation speed so that the homogeneous solution continuously passes through the reactor at a certain flow rate to achieve a single conversion, thereby generating an aromatic compound, wherein the product is mainly benzaldehyde dimethyl acetal.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] (1) The present invention constructs an electrochemical reaction system that can efficiently depolymerize β-O-4 lignin model compounds. It adopts a two-electrode constant current method, does not require a reference electrode, and uses graphite and nickel sheets as electrodes. No oxidant is required in the reaction, the conditions are mild, the substrate conversion rate is high, and the product is mainly benzaldehyde dimethyl acetal with high yield and good selectivity.

[0024] (2) The present invention uses an electrochemical continuous flow reactor to achieve continuous depolymerization of lignin dimer model compounds at low electrolyte concentrations. The electrolytic cell pressure is stable, the reaction time is greatly shortened, the product can be discharged from the reactor in a timely manner, overreaction is reduced, and the reaction rate is significantly improved, which is easy to expand.

[0025] (3) The electrochemical continuous flow reactor of the present invention has the advantages of high specific surface area, strong mass transfer capacity, high current density, stable electrolytic cell pressure, and easy expansion, allowing precise control of reaction parameters. In addition, the narrow gap of the reactor can reduce the electrolyte concentration and achieve a single conversion, which can, to a certain extent, avoid the overoxidation problem that may be caused by long-term electrolysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention is further described below with reference to the accompanying drawings.

[0027] Figure 1 This is a schematic diagram of the continuous flow electrochemical reactor designed in the present invention after assembly with a power supply, peristaltic pump, and liquid storage bottle. The following diagram shows the components: 1 - stainless steel cover plate, 2 - soft silicone pad, 3 - graphite electrode, 4 - copper foil, 5 - reaction channel, 6 - nickel electrode, 7 - fluororubber gasket, 8 - electrode placement chamber, 9 - stainless steel base, 10 - power supply, 11 - post-reaction liquid storage bottle, 12 - pre-reaction liquid storage bottle, and 13 - peristaltic pump.

[0028] Figure 2 These are three different shapes of reaction channels designed by the present invention: (a) Type I reaction channel, (b) Type II reaction channel, and (c) Type III reaction channel.

[0029] Figure 3 It is a reaction pathway diagram for the electrochemical conversion of 2-phenoxy-1-phenylethanol according to the present invention.

[0030] Figure 4 GC-FID spectra of the electrolysis products of the present invention; (a) is a comparative example, and (b) is an example. DETAILED DESCRIPTION

[0031] Figure 1 This is a schematic diagram of the electrochemical continuous flow reactor designed in the present invention, assembled with a power supply, peristaltic pump, and liquid storage bottle. The reactor is constructed in a stacked format. The reactor body comprises an electrode chamber 8, constructed from polytetrafluoroethylene. The back of the reactor features a threaded hole for connection to an externally threaded straight-through connector, allowing electrolyte to flow in and out of the reactor. The electrode chamber 8, reaction channel 5, and fluororubber gasket 7 all exhibit excellent solvent and corrosion resistance. The copper foil 4, located on the back of the electrodes, is shielded from contact with the electrolyte, preventing contamination during the electrolysis process.

[0032] Assembly method of the electrochemical continuous flow reactor: During assembly, first stick the copper foil 4 to the back of the electrode. From bottom to top, use the hexagonal knurled three-combination screw (flat washer and spring washer) to pass through the electrode placement chamber 8 and the stainless steel base 9. Place the fluororubber gasket 7, nickel electrode 6, reaction channel 5, and graphite electrode 3 into the electrode placement chamber 8 in turn. Finally, place the soft silicone pad 2 and the stainless steel cover 1, and tighten them with a plum handle nut (through hole). The electrode area is 25 square centimeters, and the effective electrode area exposed to the solution is 7.63 square centimeters.

[0033] Wherein, the reaction channel is shaped as follows Figure 3 As shown, they are (a) type I reaction channel, (b) type II reaction channel, and (c) type III reaction channel. (a) Type I reaction channel: effective area is 7.63 cm 2 (b) Type II reaction channel: effective area is 6.75 cm 2 (c) Type III reaction channel: effective area is 9.26 cm 2 . Preferably it is a type I reaction channel.

[0034] After each electrolysis experiment, the graphite electrode and nickel electrode were polished with sandpaper, washed with deionized water and ethanol respectively, and then dried for use.

[0035] The method for using this electrochemical continuous flow reactor to depolymerize the β-O-4 lignin model compound 2-phenoxy-1-phenylethanol is as follows: a target amount of 2-phenoxy-1-phenylethanol, the electrolyte tetraethylammonium perchlorate, acetonitrile, and methanol are added to a pre-reaction liquid reservoir 12 and stirred evenly. First, assemble the electrochemical continuous flow reactor. Connect a peristaltic pump tube to the externally threaded straight-through connector of the electrode placement chamber 8, and the other end to the pre-reaction liquid reservoir 12. Start the peristaltic pump 13. The post-reaction liquid reservoir 11 is used to collect the electrolyzed solution. After the solution enters the electrochemical continuous flow reactor, turn on the power. Once the solution in the pre-reaction liquid reservoir 12 and the pump tubing is depleted, turn off the power. Use an appropriate amount of acetonitrile to wash any residual reactants and products in the device and pipelines, and then turn off the peristaltic pump.

[0036] The electrolyte in the liquid storage bottle 11 after the reaction was pretreated as follows: after the electrolysis experiment, 5 mL of acetonitrile was used to clean the pipeline and the entire reactor, and the 5 mL of acetonitrile was combined with the electrolyzed solution and transferred to a 250 mL separatory funnel. 40 mL of deionized water and an appropriate amount of saturated salt water were added, and 40 mL of dichloromethane was used for three extractions. The lower organic phase was combined and an appropriate amount of anhydrous sodium sulfate was added to remove water.

[0037] Detection and analysis were performed using a gas chromatography-mass spectrometer (GC-MS), with quantification performed using an internal standard method using dimethyl phthalate as the internal standard. 2-Phenoxy-1-phenylethanol conversion = (amount of substance before reaction - amount of substance after reaction) / amount of substance before reaction. Product yield = amount of product / amount of 2-Phenoxy-1-phenylethanol before reaction.

[0038] like Figure 3 and Figure 4 As shown, 2-phenoxy-1-phenylethanol can be electrochemically converted into benzaldehyde, methyl benzoate, benzaldehyde dimethyl acetal, 4,4-dimethoxy-2,5-cyclohexadien-1-one, and 4-methoxyphenol under the method of the present invention.

[0039] The following is further described based on the examples.

[0040] Example 1: Graphite electrode is used as anode, nickel electrode is used as cathode, I-type reaction channel is selected, thickness is 0.5mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 3:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0041] Example 2: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0042] Example 3: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -31 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:3 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0043] Example 4: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1.25×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0044] Example 5: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 2.5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0045] Example 6: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0046] Example 7: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1.5×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0047] Example 8: Graphite electrode as anode, stainless steel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0048] Example 9: Graphite electrode as anode, lead electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0049] Example 10: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -41 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 100 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0050] Example 11: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 150 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0051] Example 12: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 250 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0052] Example 13: Graphite electrode is used as anode, nickel electrode is used as cathode, I-type reaction channel is selected, thickness is 0.5mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 300 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0053] Example 14: Graphite electrode is used as anode, nickel electrode is used as cathode, I-type reaction channel is selected, thickness is 0.5mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 375 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0054] Example 15: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 450 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0055] Example 16: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 600 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0056] Example 17: Graphite electrode as anode, nickel electrode as cathode, type II reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -41 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 125 μL / min, with an applied current of 35.38 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0057] Example 18: Graphite electrode as anode, nickel electrode as cathode, type II reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 225 μL / min, with an applied current of 35.38 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0058] Example 19: Graphite electrode as anode, nickel electrode as cathode, type II reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 325 μL / min, with an applied current of 35.38 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0059] Example 20: Graphite electrode as anode, nickel electrode as cathode, type II reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 400 μL / min, with an applied current of 35.38 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0060] Example 21: Graphite electrode as anode, nickel electrode as cathode, type II reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 525 μL / min, with an applied current of 35.38 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0061] Example 22: Graphite electrode as anode, nickel electrode as cathode, type III reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 175 μL / min, with an applied current of 48.54 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0062] Example 23: Graphite electrode as anode, nickel electrode as cathode, type III reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 300 μL / min, with an applied current of 48.54 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0063] Example 24: Graphite electrode as anode, nickel electrode as cathode, type III reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -41 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 450 μL / min, with an applied current of 48.54 mA. The power supply and peristaltic pump were turned off after the solution was depleted. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0064] Example 25: Graphite electrode as anode, nickel electrode as cathode, type III reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 550 μL / min, with an applied current of 48.54 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0065] Example 26: Graphite electrode as anode, nickel electrode as cathode, type III reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 725 μL / min, with an applied current of 48.54 mA. The power supply and peristaltic pump were turned off after the solution was depleted. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0066] Example 27: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.25 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 100 μL / min, with an applied current of 20 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0067] Example 28: Graphite electrode is used as anode, nickel electrode is used as cathode, I-type reaction channel is selected, thickness is 0.25mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0068] Example 29: Graphite electrode is used as anode, nickel electrode is used as cathode, I-type reaction channel is selected, thickness is 0.25mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 225 μL / min, with an applied current of 45 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0069] Example 30: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.25 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 400 μL / min, with an applied current of 80 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0070] Example 31: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with thickness of 0.25 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4mol tetraethylammonium perchlorate in 20 mL of acetonitrile / methanol (1:1 by volume) to obtain a homogeneous solution. The homogeneous solution was passed through the continuous flow electrochemical reactor at a flow rate of 800 μL / min using a peristaltic pump, and an electric current of 160 mA was applied. After the solution was consumed, the power and the peristaltic pump were turned off. The electrolyte after the reaction was pretreated and analyzed by gas chromatography mass spectrometry (GC-MS).

[0071] Example 32: Graphite electrode as anode, nickel electrode as cathode, type I reaction channel was selected, and the thickness was 0.5 mm. 2.5 x 10 -4 mol 2-phenoxy-1-phenylethanol and 5 x 10 -4 mol tetraethylammonium perchlorate in 20 mL of acetonitrile / methanol (1:1 by volume) to obtain a homogeneous solution. The homogeneous solution was passed through the continuous flow electrochemical reactor at a flow rate of 800 μL / min using a peristaltic pump, and an electric current of 160 mA was applied. After the solution was consumed, the power and the peristaltic pump were turned off. The electrolyte after the reaction was pretreated and analyzed by gas chromatography mass spectrometry (GC-MS).

[0072] Example 33: Graphite electrode as anode, nickel electrode as cathode, type I reaction channel was selected, and the thickness was 0.5 mm. 2.5 x 10 -4 mol 2-phenoxy-1-phenylethanol and 5 x 10 -4 mol tetraethylammonium perchlorate in 20 mL of acetonitrile / methanol (1:1 by volume) to obtain a homogeneous solution. The homogeneous solution was passed through the continuous flow electrochemical reactor at a flow rate of 800 μL / min using a peristaltic pump, and an electric current of 160 mA was applied. After the solution was consumed, the power and the peristaltic pump were turned off. The electrolyte after the reaction was pretreated and analyzed by gas chromatography mass spectrometry (GC-MS).

[0073] Example 34: Graphite electrode as anode, nickel electrode as cathode, type I reaction channel was selected, and the thickness was 0.5 mm. 2.5 x 10 -4 mol 2-phenoxy-1-phenylethanol and 5 x 10 -4 mol tetraethylammonium perchlorate in 20 mL of acetonitrile / methanol (1:1 by volume) to obtain a homogeneous solution. The homogeneous solution was passed through the continuous flow electrochemical reactor at a flow rate of 800 μL / min using a peristaltic pump, and an electric current of 160 mA was applied. After the solution was consumed, the power and the peristaltic pump were turned off. The electrolyte after the reaction was pretreated and analyzed by gas chromatography mass spectrometry (GC-MS).

[0074] Example 35: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 800 μL / min, with an applied current of 160 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0075] Example 36: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 1.0 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 100 μL / min, with an applied current of 20 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0076] Example 37: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 1.0 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0077] Example 38: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 1.0 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -41 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 400 μL / min, with an applied current of 80 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0078] Example 39: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 1.0 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 800 μL / min, with an applied current of 160 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0079] Example 40: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 20 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0080] Example 41: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 30 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0081] Example 42: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 50 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0082] Example 43: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 5×10 -4 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of a 1:1 acetonitrile / methanol (volume ratio) mixture to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 60 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0083] Comparative Example 1: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of acetonitrile to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0084] Comparative Example 2: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of acetonitrile to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 200 μL / min, with an applied current of 50 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0085] Comparative Example 3: Graphite electrode as anode, nickel electrode as cathode, I-type reaction channel with a thickness of 0.5 mm. -4 mol 2-phenoxy-1-phenylethanol and 1×10 -3 1 mol of tetraethylammonium perchlorate was dissolved in 20 mL of acetonitrile to obtain a homogeneous solution. This solution was passed through a continuous flow electrochemical reactor using a peristaltic pump at a flow rate of 150 μL / min, with an applied current of 40 mA. Once the solution was depleted, the power supply and peristaltic pump were turned off. The post-reaction electrolyte was pretreated and analyzed by gas chromatography-mass spectrometry (GC-MS).

[0086] Table 1: Reaction evaluation results with different methanol contents

[0087]

[0088] Table 2: Results of reaction evaluation without adding methanol

[0089]

[0090] Table 3: Reaction evaluation results at different electrolyte concentrations

[0091]

[0092] Table 4: Reaction evaluation results of different cathodes

[0093]

[0094] Table 5: Reaction evaluation results of reaction channels with different shapes

[0095]

[0096]

[0097] Table 6: Reaction evaluation results of reaction channels with different thicknesses

[0098]

[0099] Table 7: Reaction evaluation results at different currents

[0100]

[0101]

[0102] Note: The values ​​in the table represent the molar yield relative to the substrate, and - means that the corresponding product could not be detected by GC-MS.

[0103] From the comparison of Comparative Examples 1-3 and Comparative Examples 1-3, it can be seen that methanol can participate in the reaction as a reactant to generate benzaldehyde dimethyl acetal under the electrochemical action, the benzaldehyde dimethyl acetal is not easy to be oxidized, and the yield is higher. In addition, after the addition of methanol, the electrolytic cell pressure is greatly reduced, and the graphite electrode is not easy to be corroded.

[0104] From the comparison of Comparative Example 2 and Examples 4-7, it can be seen that the electrolysis in the reactor of the application can greatly reduce the amount of electrolyte, especially the amount of expensive tetraalkylammonium salt, thereby reducing the cost and also reducing the difficulty of subsequent product separation and purification.

[0105] From the comparison of Comparative Example 6 and Examples 8-9, it can be seen that the application can use inexpensive nickel electrodes and stainless steel as cathodes, which have long service life and good electrolysis effect, and can avoid the use of toxic lead electrodes.

[0106] From the comparison of Comparative Example 6 and Examples 10-16, the reaction conversion rate and yield decrease with the increase of flow rate, and the flow rate is too small to easily generate methyl benzoate by over-oxidation. The flow rate within the preferred range of the application is beneficial to achieve high yield and high conversion rate.

[0107] From the comparison of Comparative Example 6 and Examples 10-26, by controlling the current density to be constant and adjusting the flow rate, the reaction time of 2-phenoxy-1-phenylethanol in three different shapes of reaction channels is basically the same. By comparing the conversion rate and yield of the three, it is found that the change of shape does not affect the reaction, and the increase of protrusions or grooves on the reaction channel reduces the firmness of the reaction channel. The preferred shape of the reaction channel of the application is beneficial to prolong the service life.

[0108] From the comparison of Comparative Example 6 and Examples 27-39, considering the reaction rate and product yield, the preferred thickness of the reaction channel of the application is beneficial to achieve high conversion rate and high yield in a shorter time.

[0109] From the comparison of Comparative Example 6 and Examples 40-43, it can be seen that the preferred current range of the application is beneficial to achieve high conversion rate and high yield.

[0110] In summary, the reactor can greatly reduce the amount of electrolyte, reduce the pressure of the electrolytic cell and make it more stable, speed up the reaction rate, and the shape of the reaction channel has little effect on the reaction result. Under the condition of constant total electric charge consumption, the reaction channel with smaller thickness can apply larger current at faster flow rate to achieve high conversion rate and high yield in a short time, while the reaction channel with larger thickness needs to apply smaller current and slower flow rate to achieve higher yield.

[0111] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for oxidative depolymerization of a β-O-4 lignin model compound based on an electrochemical continuous flow reactor, characterized in that: The electrochemical continuous flow reactor comprises an anode plate, a cathode plate and a serpentine reaction channel located between the anode plate and the cathode plate, wherein the anode plate and the cathode plate are connected to the positive and negative electrodes of a power supply respectively; A β-O-4 lignin model compound and tetraethylammonium perchlorate are dissolved in a mixed solvent to obtain a homogeneous solution, which is continuously introduced into a serpentine reaction channel of an electrochemical continuous flow reactor, and an electric current is applied to perform an electrolysis reaction to obtain an aromatic compound; the mixed solvent is acetonitrile and methanol.

2. The method according to claim 1, characterized in that The flow rate of the homogeneous solution is 100-800 μL / min, and the current density is 2.5-25 mA / cm 2 .

3. The method according to claim 2, characterized in that The current is 20-160 mA.

4. The method according to claim 3, characterized in that The thickness of the serpentine reaction channel is 0.1-1.0 mm, the current is 30-50 mA, and the flow rate of the homogeneous solution is 100 μL / min-200 μL / min.

5. The method according to claim 4, characterized in that The volume ratio of the acetonitrile to methanol is 1:3-5:

1.

6. The method according to claim 5, characterized in that The volume ratio of the acetonitrile to methanol is 1:3-3:

1.

7. The method according to any one of claims 1 to 6, characterized in that The anode plate is a graphite electrode; the cathode plate is a nickel sheet electrode, a stainless steel electrode, a platinum electrode, a copper electrode or a silver electrode.

8. The method according to claim 7, characterized in that The β-O-4 lignin model compound includes one or more of 2-phenoxy-1-phenylethanol, 2-(2-methoxyphenoxy)-1-phenylethanol, 2-phenoxyacetophenone and 2-phenoxy-1-phenylethane.

9. The method according to claim 8, characterized in that The molar volume ratio of tetraethylammonium perchlorate to the mixed solvent is 10 -4 -1.5×10 -3 mol: 20 mL; the molar ratio of the lignin dimer model compound to tetraethylammonium perchlorate is 2.5:(1-15).

10. The method according to claim 9, characterized in that The aromatic compounds include benzaldehyde, methyl benzoate, benzaldehyde dimethyl acetal, 4,4-dimethoxy-2,5-cyclohexadien-1-one, and 4-methoxyphenol.

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