Method for co-producing formic acid and hydrogen through off-field electro-catalysis oxidation of solid biomass

Abstract

The invention discloses a method for co-producing formic acid and hydrogen through off-field electro-catalysis solid biomass oxidation, and belongs to the technical field of electro-catalysis. According to the method, a water-soluble electron mediator is introduced, and a solid-solid reaction with slow mass-charge transfer between a traditional electro-catalysis electrode and solid biomass is decoupled into a rapid liquid-solid reaction, so that the problem that solid reactants cannot be treated by traditional electro-catalysis is effectively solved. Meanwhile, oxidation and reduction reactions are transferred into a reactor outside the electrolytic tank, so that complex reactions related to gas, liquid, solid and other phases can be carried out far away from the surface of an electrode, pollution of reactants or products to the electrode, a catalyst, a diaphragm and the like is fundamentally avoided, and therefore, failure or activity reduction of an electrocatalytic reaction system is prevented. The method significantly improves the stability and continuity of the system, and is suitable for large-scale biomass hydrogen production and selective preparation of chemicals.

Description

Technical Field

[0001] The present application relates to a method for off-site electrocatalytic solid biomass oxidation to co-produce formic acid and hydrogen, belonging to the technical field of electrocatalysis. Background Art

[0002] Biomass is the only renewable carbon resource that is widely distributed and inexpensive. Directly upgrading and converting biomass through green and sustainable strategies is of great significance for alleviating the energy crisis and achieving carbon neutrality. However, there are some problems with the current thermal catalytic oxidation process for direct utilization of biomass, including the use of precious metal catalysts, the consumption of large amounts of oxidants, and the need for harsh conditions such as high temperature and high pressure (Nature Catalysis, 2018, 1, 332-338; Green Chemistry, 2019, 21, 6089-6096). Although the conditions for electrocatalytic biomass conversion are relatively mild, due to the difficulty of mass-charge transfer between solid electrodes and solid biomass in the electrolytic cell, current research on electrocatalytic biomass conversion is mostly focused on model molecules. For example, patents CN 113832482 B, CN 116397245 A, CN 118516688 A and CN 113638006 A all studied the conversion of small molecules such as some water-soluble polyhydroxy compounds, but did not involve the direct conversion and upgrading of solid biomass. In addition, such systems usually place the reactants into the anode electrolyte and carry out oxidation reactions through the electrode or the catalyst surface it carries. In this process, organic matter will be strongly adsorbed on the electrode, causing poisoning of the active centers on the electrode surface and easy to be peroxidized. At the same time, the free radicals generated during the reaction may destroy the structure of the membrane. At the same time, under high current density working conditions, a large number of hydrogen bubbles will precipitate rapidly, which can easily cause the catalyst to fall off, and the adsorption of bubbles on the electrode surface will reduce the contact area between the electrode and the electrolyte, causing mass transfer difficulties. This phenomenon is called "bubble shielding effect" (Adv. Energy Mater. 2024, 14, 2303563). The above factors will cause the electrocatalytic reaction system to fail or decrease in activity, making it difficult to achieve stable and continuous operation.

[0003] Therefore, in order to realize the industrial, continuous and stable application of large-scale solid biomass oxidation coupled hydrogen production, it is urgent to innovate the existing electrocatalytic reaction mode to achieve direct electrocatalytic solid biomass conversion and avoid problems such as contamination and coverage of electrodes and membranes by reactants or products. Summary of the invention

[0004] In order to solve the problem that traditional electrocatalysis cannot handle solid reactants in the existing electrocatalytic technology and the problem of reactants or products polluting and covering electrodes, catalysts and membranes, this application proposes a new type of "off-site" electrocatalytic solid biomass oxidation co-production of formic acid and hydrogen. By introducing a water-soluble electron mediator, the solid-solid reaction with slow mass-charge transfer between the traditional electrocatalytic electrode and the solid biomass is decoupled into a fast liquid-solid reaction, thereby effectively solving the problem that traditional electrocatalysis cannot handle solid reactants. At the same time, the oxidation and reduction reactions are transferred to the reactor outside the electrolytic cell, which allows complex reactions involving gas, liquid, solid and other phases to be carried out away from the electrode surface, fundamentally avoiding the pollution of reactants or products on electrodes, catalysts and diaphragms, thereby preventing the electrocatalytic reaction system from failing or decreasing in activity.

[0005] This application adopts the following technical solutions:

[0006] The "off-site" electrocatalytic solid biomass oxidation method for co-production of formic acid and hydrogen adopted in this application is based on the following system:

[0007] (I) Electrochemical cell system: The electrochemical cell system includes an anode tank, a cathode tank, an electrolyte and a diaphragm, and the redox couples of the anode and cathode are converted into corresponding oxidized states and reduced states respectively by applying voltage.

[0008] (II) Oxidation system: The oxidized redox couple obtained at the anode is added to an oxidation reactor, and the solid biomass is oxidized into products under the action of a catalyst. The products are then separated from the redox couple by distillation or extraction, and the separated couple re-enters the electrochemical cell for anode oxidation regeneration.

[0009] (III) Reduction system: The reduced redox couple obtained at the cathode is added to the reduction reactor, and H + It is reduced to H2 and released, and the reacted electrode couple re-enters the cathode of the electrochemical cell for reduction and regeneration.

[0010] According to a first aspect of the present application, a method for the co-production of formic acid and hydrogen by off-site electrocatalytic oxidation of solid biomass is provided, comprising the following steps: in an off-site electrocatalytic system, solid biomass or biomass derivatives undergo oxidation reaction to generate formic acid, and H + Generate hydrogen through reduction reaction;

[0011] The off-site electrocatalytic system includes an electrochemical cell system, an oxidation system, and a reduction system;

[0012] The electrochemical cell system comprises an electrolytic cell, wherein the electrolytic cell comprises an anode electrode, a cathode electrode, an anode tank and a cathode tank separated by a diaphragm, and an electrolyte disposed in the anode tank and the cathode tank;

[0013] The electrolyte in the anode tank includes a redox couple M composed of M metal ions. x+ / M (x+1)+ ,

[0014] The electrolyte in the anode tank includes inorganic metal ions composed of N metal ions. y+ / N (y-1)+ , where x is 2 to 6, y is 2 to 6;

[0015] The oxidation system comprises an oxidation reactor, and the oxidation reactor is cyclically connected with the anode tank in the electrolytic cell through a first anode pipeline and a second anode pipeline;

[0016] The reduction system comprises a reduction reactor and a separator, wherein the reduction reactor is cyclically connected to the cathode tank in the electrolytic cell through a first cathode pipeline and a second cathode pipeline, and the separator is on the second cathode pipeline;

[0017] The step of generating formic acid by oxidation reaction of solid biomass or biomass derivatives comprises: (x+1)+ The electrolyte is introduced into the oxidation reactor through the first anode pipeline, mixed with the solid biomass or biomass derivative, and an oxidation reaction occurs to generate formic acid and metal ions M x+ , formic acid and metal ions M x+ After separation in the separator, formic acid is discharged from the oxidation system, containing metal ions M x+ The electrolyte is returned to the anode tank through the second anode pipeline;

[0018] The H + The steps of generating hydrogen by reduction reaction include: (y-1)+ The electrolyte is introduced into the reduction reactor through the first cathode pipeline, and reacts with the H + Reduction reaction occurs to generate hydrogen and metal ions N y+ , hydrogen is discharged from the reduction system, containing metal ions N y+ The electrolyte returns to the cathode tank through the second cathode pipeline.

[0019] Optionally, the electrolytic cell is selected from one of an H-type electrolytic cell and a liquid flow battery.

[0020] Optionally, the temperature of the electrochemical cell system is 5 to 80° C., and the pressure is 1 to 30 bar.

[0021] Optionally, the electrolyte is an acidic aqueous solution with a pH value less than 2.

[0022] Optionally, the acid in the acidic aqueous solution is at least one inorganic acid selected from H2SO4, HCl, H3PO4, and HClO4.

[0023] Optionally, the acid concentration in the acidic aqueous solution is 0.01 to 6 mol / L.

[0024] Optionally, the redox couple M in the electrolyte x+ / M (x+1)+ The concentration of inorganic metal ions and the effect of y+ / N (y -1)+ The concentration can be selected arbitrarily.

[0025] Optionally, the electrolyte further comprises a metal inorganic salt, for example, an alkali metal, an ammonium ion, etc. may be added to increase the conductivity of the electrolyte and optimize the catalytic activity.

[0026] Optionally, the anode electrode and the cathode electrode are independently selected from at least one of a carbon rod, a carbon felt, a titanium mesh, a copper mesh, and the like.

[0027] Optionally, the M metal is selected from one of V and Ce, and the N metal is selected from one of Eu, Cr and V.

[0028] Optionally, the redox couple M x+ / M (x+1)+ Selected from one of V(IV) / V(V), Ce(III) / Ce(IV).

[0029] Optionally, the inorganic metal ion N y+ / N (y-1)+ One selected from heteropoly acid, Eu(II) / Eu(III), Cr(II) / Cr(III), V(II) / V(III).

[0030] Optionally, the solid biomass is selected from at least one of straw, corn cobs, and wood powder.

[0031] Optionally, the biomass derivative is selected from at least one of sugars, alcohols, aldehydes and carboxylic acids.

[0032] Optionally, the biomass derivative is selected from at least one of cellulose, hemicellulose, xylan, sucrose, cellobiose, glucose, fructose, mannose, galactose, sorbitol, xylose, xylitol, erythrose, erythritol, glycerol, glyceraldehyde, glyceric acid, ethylene glycol, glycolaldehyde, glycolic acid, glyceraldehyde, oxalic acid, glyoxal, and acetaldehyde.

[0033] Optionally, the oxidation reactor is selected from one of a fixed bed, a tank reactor, a slurry bed, a tray reactor, and a fluidized bed reactor.

[0034] Optionally, the conditions for the oxidation reaction include: the pressure of the oxidizer is 1 to 200 bar, and the temperature is 5 to 200°C.

[0035] Optionally, the separator comprises an extraction separator and / or a distillation separator.

[0036] Optionally, the extraction process using the extraction separator includes: using ether extraction to separate formic acid and metal ions M x+ After separation, the formic acid in the ether is back-extracted with water to obtain an aqueous formic acid solution.

[0037] Optionally, the extraction process using the distillation separator includes: extracting the formic acid and metal ion M x+ The electrolyte is rotary evaporated to obtain an aqueous formic acid solution.

[0038] Optionally, the extraction process using the extraction separator includes: extracting 5 times with ether three times the volume of the reaction solution to separate formic acid and redox couple, with a formic acid extraction rate of up to 99%, and then back-extracting the formic acid in the ether with water to obtain a formic acid aqueous solution; for a small amount of ether remaining in the redox couple solution after extraction, the solution can be heated to 30-50°C and nitrogen can be passed through for a period of time to remove it.

[0039] Optionally, the extraction process using the distillation separator includes: using a rotary evaporator to perform distillation operation, setting the temperature of the rotary evaporator to 40 to 65°C, and setting the low-temperature cooling circulation system to -15 to -20°C. When both temperatures reach the set values, pouring the reaction solution containing formic acid into a round-bottom flask and starting rotary evaporation. After the rotary evaporation is completed, the formic acid aqueous solution can be obtained by collecting the bottle.

[0040] Optionally, the reduction reactor is selected from one of a fixed bed reactor, a tank reactor, a slurry bed reactor, and a fluidized bed reactor.

[0041] Optionally, the conditions for the reduction reaction include: the pressure of the reduction reactor is 1 to 200 bar, and the temperature is 5 to 200°C.

[0042] Optionally, the reduction reactor further comprises a catalyst, the H + The step of generating hydrogen by reduction reaction also includes: the reduction reactor contains a catalyst, under the action of the catalyst, the metal ions N (y-1)+ The H in the electrolyte in the reduction reactor + Reduction reaction occurs to generate hydrogen and metal ions N y+ .

[0043] Optionally, the catalyst is selected from metals and / or metal oxides, metals and / or metal oxides supported on a carrier, and non-metallic catalysts.

[0044] Optionally, the metal is selected from at least one of Au, Cu, Ru, Ir, Pt, Pd, Rh, Fe, and Co.

[0045] Optionally, the carrier is selected from at least one of carbon, metal oxide, carbide, silicide and phosphide.

[0046] Preferably, the non-metal catalyst is selected from at least one of carbides, phosphides and nitrides.

[0047] Optionally, in the reduction reactor, H + Derived from at least one of H2SO4, HCl, H3PO4, and HClO4.

[0048] The beneficial effects of this application include:

[0049] The method for the off-site electrocatalytic oxidation of solid biomass to produce formic acid and hydrogen provided by the present application, by introducing a water-soluble electron mediator, decouples the slow solid-solid reaction of mass-charge transfer between the traditional electrocatalytic electrode and the solid biomass into a fast liquid-solid reaction, thereby effectively solving the problem that the traditional electrocatalysis cannot handle solid reactants. At the same time, this method transfers the oxidation and reduction reactions to the reactor outside the electrolytic cell, and can move the complex reactions involving gas, liquid, solid and other phases out of the electrode surface, fundamentally avoiding the pollution of the reactants or products to the electrodes, catalysts and diaphragms, thereby preventing the electrocatalytic reaction system from failing or decreasing in activity. This "off-site" electrocatalytic method significantly improves the stability and continuity of the system, is suitable for large-scale biomass hydrogen production and selective preparation of chemicals, and is not only suitable for basic theoretical research, but also has important practical application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 is a schematic diagram of the reaction principle of the present application (taking glucose as an example);

[0051] Figure 2 is a graph of hydrogen production for different catalyst dosages of the present application;

[0052] Figure 3 It is a graph of hydrogen generation rate and V(II) conversion rate at different space velocities of the present application;

[0053] Figure 4 This is the hydrogen evolution stability diagram of the system in this application after running for 200 hours.

[0054] Figure 5 is a high performance liquid chromatogram of the ethylene glycol oxidation product of Example 4 of the present application;

[0055] Figure 6 is a high performance liquid chromatogram of the glycerol oxidation product of Example 5 of the present application;

[0056] Figure 7 This is a high performance liquid chromatogram of the wood powder oxidation product of Example 7 of the present application. DETAILED DESCRIPTION

[0057] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0058] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0059] Unless otherwise specified, conventional methods were used for testing and instrument settings were those recommended by the manufacturer.

[0060] As one of the embodiments, the method for the off-site electrocatalytic solid biomass oxidation co-production of formic acid and hydrogen provided in the present application is achieved by the following technical solution:

[0061] The whole process includes three parts: electrochemical cell system, oxidation system and reduction system. The specific steps are as follows: the electrochemical cell system consists of an anode tank, a cathode tank, an electrolyte and a diaphragm. The electrolytes of the cathode and anode are both acidic aqueous solutions with a pH value of less than 2. The solute on the anode side is a metal ion M x+ , which undergoes oxidation reaction on the anode surface, the valence state increases, and the oxidized M (x+1)+ The solute on the cathode side is metal ion N y+ , a reduction reaction occurs on the cathode surface, the valence state decreases, and the reduced N (y -1)+ .

[0062] In the oxidation system, the oxidized metal ion M (x+1)+ Introduced into the oxidation reactor, it undergoes oxidation reaction with solid biomass and biomass derivatives, and the metal ions M (x+1)+ Restored to M x+ , while the solid biomass or biomass derivative is oxidized to form formic acid. The metal ions are separated from the formic acid by distillation or extraction, and then the metal ions M x+ Return to the anode tank to complete the electrochemical / biomass and biomass derivative oxidation reaction cycle on the anode side.

[0063] In the reduction system, the reduced metal ions N (y-1)+ is introduced into the reduction reactor and reacts with H + Reduction reaction occurs, metal ion N (y-1)+ Oxidized to N y+ , H + is reduced to hydrogen H2 and released. After that, the metal ion N y+ Return to the cathode tank to complete the electrochemical / hydrogen evolution reaction on the cathode side.

[0064] Example 1 "Off-site" electrocatalytic solid biomass-derived glucose oxidation coupled hydrogen production

[0065] Step 1: Preparation of electrolyte

[0066] VOSO4 solid is dissolved in 1 mol / L H2SO4 aqueous solution to obtain V(IV) / H2SO4 solution, which is then reduced to V(III) / H2SO4 solution at the cathode of an electrochemical cell. The V(IV) / H2SO4 solution is used as the anode electrolyte and the V(III) / H2SO4 solution is used as the cathode electrolyte.

[0067] Step 2: System Construction

[0068] like Figure 1 As shown, the "off-site" electrocatalytic solid biomass oxidation system for co-production of formic acid and hydrogen in the present application consists of an electrochemical cell, an oxidation reactor, and a reduction reactor. In the electrochemical cell, a carbon felt electrode is used as the working electrode, and a proton exchange membrane (Nafion117 model, the membrane is pretreated in a boiling solution of 1 mol / L H2SO4 and 3% H2O2 for 30 minutes, and then washed with deionized water) is used to divide the electrochemical cell into an anode and a cathode, and the corresponding anolyte and cathode electrolyte are added. The system is connected to a power source through a wire for electrolysis operation. During the electrolysis process, the metal ion V (IV) at the anode is oxidized to V (V), and the reaction equation is: The V(III) at the cathode is reduced to V(II) with the reaction equation: 3+ +e - →V 2+ .

[0069] The V(V) generated by anodic oxidation is introduced into the autoclave oxidation reactor through a liquid pump and reacts with biomass-based glucose at normal pressure and set temperature (80°C) for a specified time (4h). During the reaction, the molar ratio of glucose to V(V) in the solution is 1:18, glucose is cleaved and oxidized to formic acid, and V(V) is reduced to V(IV). The reaction equation is: After the reaction is completed, formic acid and electrolyte are separated by distillation or extraction to obtain a formic acid aqueous solution, and the electrolyte containing V (IV) is returned to the electrochemical cell and reoxidized to V (V) under electrochemical action. The conversion rate and selectivity of the reaction solution are confirmed by liquid chromatography, and the results show that the anodic oxidation product is mainly formic acid, the conversion rate of glucose is 99%, the formic acid selectivity is 90%, and the CO selectivity is 8%.

[0070] The V(II) generated by cathode reduction is transported to the fixed bed reduction reactor by a liquid pump and reacts with H in the solution. + A reduction reaction occurs. Under the action of molybdenum carbide catalyst (labeled as Mo2C), V(II) is oxidized to V(III), and H +is reduced to hydrogen. The reaction equation is: V 2+ +H + →H2+V 3+ After the reaction is completed, the electrolyte containing V(III) returns to the cathode of the electrochemical cell and is regenerated into V(II) through electrochemical reduction. Figure 2 As shown in Figure 2, the actual production of hydrogen is consistent with the theoretical production at different catalyst dosages. Figure 3 As shown in the figure, the volume space velocity of the V(II) electrolyte flowing into the fixed bed reduction reactor is an important parameter affecting the reaction. When the catalyst dosage is determined, as the volume space velocity of the V(II) electrolyte increases, the hydrogen generation rate first increases and then remains unchanged, while the conversion rate of V(II) gradually decreases. The volume space velocity is selected to be 22 mL g -1 h -1 The hydrogen evolution stability test was carried out under the conditions of Figure 4 As shown, the results show that the system runs stably for 200 hours and has practical application value.

[0071] The overall reaction equation of the whole system is: C6H 12 O6+H2O→HCOOH+CO2+H2. This means that the “off-site” electrocatalytic solid biomass-based glucose oxidation to produce formic acid and hydrogen is achieved.

[0072] The present application effectively avoids organic matter contamination of electrodes, catalysts and diaphragms by transferring the biomass organic matter oxidation reaction on the anode side to the external reactor of the battery. At the same time, the cathode hydrogen production reaction is moved to the outside of the battery, which avoids hydrogen bubbles covering the cathode catalyst and eliminates the bubble shielding effect, thereby improving the working efficiency of the battery.

[0073] Example 2: Off-site electrocatalytic production of formic acid and hydrogen from xylose

[0074] The method is the same as that of Example 1, except that the glucose in step 2 is replaced by xylose, wherein the molar ratio of xylose to V(V) in the solution is n 木糖 :n V =1:15, the reaction results are that the conversion rate of xylose is 100%, the selectivity of formic acid is 93%, and the selectivity of CO2 is 5%.

[0075] Example 3: Off-site electrocatalytic production of formic acid and hydrogen from fructose

[0076] The method is the same as in Example 1, except that the glucose in step 2 is replaced by fructose, wherein the molar ratio of fructose to V(V) in the solution is n 果糖 :n V =1:18, the reaction results are that the conversion rate of fructose is 100%, the selectivity of formic acid is 73%, and the selectivity of CO2 is 26%.

[0077] Example 4: Off-site electrocatalytic production of formic acid and hydrogen from ethylene glycol

[0078] The method is the same as that of Example 1, except that the glucose in step 2 is replaced by ethylene glycol, wherein the molar ratio of ethylene glycol to V(V) in the solution is n 乙二醇 :n V =1:6, the reaction results are that the conversion rate of ethylene glycol is 29%, the selectivity of formic acid is 92%, and the selectivity of CO2 is 2%.

[0079] Example 5: Off-site electrocatalytic production of formic acid and hydrogen from glycerol

[0080] The method is the same as in Example 1, except that the glucose in step 2 is replaced by glycerol, wherein the molar ratio of glycerol to V(V) in the solution is n 甘油 :n V =1:9, the reaction results are that the conversion rate of glycerol is 45%, the selectivity of formic acid is 77%, and the selectivity of CO2 is 15%.

[0081] Example 6 “Off-site” electrocatalytic production of formic acid and hydrogen from cellulose

[0082] The method is the same as that of Example 1, except that the glucose in step 2 is replaced by cellulose hydrolyzate, wherein the step of cellulose hydrolysis is as follows: 0.5 g of each biomass sample is placed in a 250 ml beaker, followed by the addition of 7.5 ml of a 72 wt% sulfuric acid solution. The mixture is stirred at room temperature for 2 hours. Then 90 ml of water is added to reduce the sulfuric acid concentration to 3 wt%, and the solution is heated to 100°C and refluxed for 6 hours under magnetic stirring. The molar ratio of glucose in the cellulose hydrolyzate to V(V) in the solution is (n 水解葡萄糖 :n V =1:9), the reaction results are that the conversion rate of glucose is 100%, the selectivity of formic acid is 90%, and the selectivity of CO2 is 10%.

[0083] Example 7: "Off-site" electrocatalytic production of formic acid and hydrogen from wood powder

[0084] The method is the same as that in Example 1, except that the reactant glucose at the anode in step 2 is replaced with wood powder. The reaction result is that the substances (including sugars) produced by the in-situ hydrolysis of cellulose and hemicellulose in the wood powder are in-situ oxidized by the redox couple V(V) to formic acid and a small amount of acetic acid, leaving insoluble lignin in the solution. According to the experimental results, 0.54g can be obtained from 0.8g of wood powder, and the mass yield is 67.5%.

[0085] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for the co-production of formic acid and hydrogen by off-site electrocatalytic oxidation of solid biomass, characterized in that: The steps include: in an off-site electrocatalytic system, solid biomass or biomass derivatives undergo oxidation reaction to generate formic acid, and H + Generate hydrogen through reduction reaction; The off-site electrocatalytic system includes an electrochemical cell system, an oxidation system, and a reduction system; The electrochemical cell system comprises an electrolytic cell, wherein the electrolytic cell comprises an anode electrode, a cathode electrode, an anode tank and a cathode tank separated by a diaphragm, and an electrolyte disposed in the anode tank and the cathode tank; The electrolyte in the anode tank includes a redox couple M consisting of M metal ions. x+ / M (x+1)+ , The electrolyte in the anode tank includes inorganic metal ions composed of N metal ions. y+ / N (y-1)+ , where x is 2 to 6, y is 2 to 6; The oxidation system comprises an oxidation reactor, and the oxidation reactor is cyclically connected with the anode tank in the electrolytic cell through a first anode pipeline and a second anode pipeline; The reduction system comprises a reduction reactor and a separator, wherein the reduction reactor is cyclically connected to the cathode tank in the electrolytic cell through a first cathode pipeline and a second cathode pipeline, and the separator is on the second cathode pipeline; The step of generating formic acid by oxidation reaction of solid biomass or biomass derivatives comprises: (x+1)+ The electrolyte is introduced into the oxidation reactor through the first anode pipeline, mixed with the solid biomass or biomass derivative, and an oxidation reaction occurs to generate formic acid and metal ions M x+ , formic acid and metal ions M x+ After separation in the separator, formic acid is discharged from the oxidation system, containing metal ions M x+ The electrolyte is returned to the anode tank through the second anode pipeline; The H + The steps of generating hydrogen by reduction reaction include: (y-1)+ The electrolyte is introduced into the reduction reactor through the first cathode pipeline, and reacts with the H + Reduction reaction occurs to generate hydrogen and metal ions N y+ , hydrogen is discharged from the reduction system, containing metal ions N y+ The electrolyte returns to the cathode tank through the second cathode pipeline.

2. The method according to claim 1, characterized in that The electrolytic cell is selected from one of an H-type electrolytic cell and a flow battery; Preferably, the temperature of the electrochemical cell system is 5-80° C., and the pressure is 1-30 bar.

3. The method according to claim 1, characterized in that The electrolyte is an acidic aqueous solution with a pH value less than 2; Preferably, the acid in the acidic aqueous solution is at least one inorganic acid selected from H2SO4, HCl, H3PO4, and HClO4; Preferably, the acid concentration in the acidic aqueous solution is 0.01 to 6 mol / L.

4. The method according to claim 1, characterized in that: The electrolyte also includes a metal inorganic salt.

5. The method according to claim 1, characterized in that The M metal is selected from one of V and Ce, and the N metal is selected from one of Eu, Cr and V; Preferably, the redox couple M x+ / M (x+1)+ One selected from V(IV) / V(V), Ce(III) / Ce(IV); Preferably, the inorganic metal ion is N y+ / N (y-1)+ One selected from heteropoly acid, Eu(II) / Eu(III), Cr(II) / Cr(III), V(II) / V(III).

6. The method according to claim 1, characterized in that The solid biomass is selected from at least one of straw, corn cobs, and wood powder; Preferably, the biomass derivative is selected from at least one of sugars, alcohols, aldehydes, and carboxylic acids; Preferably, the biomass derivative is selected from at least one of cellulose, hemicellulose, xylan, sucrose, cellobiose, glucose, fructose, mannose, galactose, sorbitol, xylose, xylitol, erythrose, erythritol, glycerol, glyceraldehyde, glyceric acid, ethylene glycol, glycolaldehyde, glycolic acid, glyceraldehyde, oxalic acid, glyoxal, and acetaldehyde.

7. The method according to claim 1, characterized in that The oxidation reactor is selected from one of a fixed bed, a tank reactor, a slurry bed, a tray reactor, and a fluidized bed reactor; Preferably, the conditions for the oxidation reaction include: the pressure of the oxidizer is 1 to 200 bar, and the temperature is 5 to 200°C.

8. The method according to claim 1, characterized in that The separator comprises an extraction separator and / or a distillation separator; Preferably, the extraction process using the extraction separator comprises: using ether extraction to separate formic acid and metal ions M x+ Separating, and then back-extracting the formic acid in the ether with water to obtain a formic acid aqueous solution; Preferably, the extraction process using the distillation separator comprises: extracting the formic acid and metal ion M x+ The electrolyte is rotary evaporated to obtain an aqueous formic acid solution.

9. The method according to claim 1, characterized in that: The reduction reactor is selected from one of a fixed bed reactor, a tank reactor, a slurry bed reactor, and a fluidized bed reactor; Preferably, the conditions for the reduction reaction include: the pressure of the reduction reactor is 1-200 bar, and the temperature is 5-200°C.

10. The method according to claim 1, characterized in that The reduction reactor also contains a catalyst, the H + The step of generating hydrogen by reduction reaction also includes: the reduction reactor contains a catalyst, under the action of the catalyst, the metal ions N (y-1)+ The H in the electrolyte in the reduction reactor + Reduction reaction occurs to generate hydrogen and metal ions N y+ .

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