Method for the production of hydrogen by coupling of electrocatalytic polyol production of polyol acids

Abstract

The application discloses a method for preparing polyol acid and coupling hydrogen production by electrocatalysis polyol, which comprises the following steps: taking a conductive substrate loaded with an anode catalyst noble metal / hydroxide as an anode, taking a cathode catalyst as a cathode, assembling an electrolytic cell with an electrolyte, adding polyol into the electrolyte, and oxidizing the polyol into polyol acid at the anode and reducing water into hydrogen at the cathode under voltage conditions. The application constructs the noble metal / hydroxide as the anode catalyst, takes the hydrogen atom / oxygen atom in water as the source of [H] / [O] in the redox reaction, utilizes the hydrogen bond action between the hydroxyl group on the surface of the hydroxide and the hydroxyl group of the polyol to adsorb and enrich the polyol on the surface of the catalyst, improves the local concentration of the reactant, thereby improves the current density, and makes it meet the requirements of industrial production. Meanwhile, the water is reduced into hydrogen at the cathode, and the industrial application potential is further improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyol acid production, and particularly relates to a method for preparing polyol acid by coupling electrocatalytic polyol production and hydrogen production. BACKGROUND

[0002] With the call for sustainable development of society, the idea of turning waste into treasure is increasingly favored by researchers. For example: glycerol is the main byproduct in the production process of biodiesel, and one ton of glycerol is produced for every nine tons of biodiesel. The production of biodiesel has exceeded 46.8 billion liters in 2020 (Renewables 2021-global status report), which leads to an excess of glycerol output. On the other hand, ethylene glycol is a key monomer of polyethylene terephthalate (PET) plastic. The annual output of PET is about 700 million tons, but less than 20% of PET is recycled by traditional mechanical methods, and the rest is buried or discarded, which not only seriously pollutes the environment but also wastes a large amount of ethylene glycol (Nat. Commun., 2021, 12, 4679). How to upgrade the value of glycerol and ethylene glycol "waste" has become a research problem.

[0003] Lactic acid and glycolic acid are the oxidation products of glycerol and ethylene glycol, respectively, and are also the monomers of biodegradable plastics polylactic acid (PLA) and polyglycolic acid (PGA), respectively, and are widely used in cosmetics and medical fields. At present, the production of lactic acid and glycolic acid is mainly based on microbial fermentation method, but the fermentation method has a very long production time and involves complex separation steps, which limits the further development of lactic acid and glycolic acid. Thermal catalytic glycerol / ethylene glycol to lactic acid / glycolic acid has been widely studied (Appl. Catal. B, 2021, 284: 119803; Nat. Commun., 2014, 5(1): 1-9), but it requires a high-temperature and high-pressure environment, which is not conducive to industrial production. Electro-catalytic method is driven by renewable energy electricity and uses water as the source of [O] and [H] in the redox reaction, which is green and pollution-free, and has attracted much attention from researchers in recent years. However, due to the multi-hydroxyl structure of glycerol and ethylene glycol, the C-C bond is easy to break, so the product of electro-catalytic polyol is mainly formic acid with low added value.

[0004] Although there have been some literatures in recent years that use noble metal-based catalysts to successfully prepare lactic acid / glycolic acid by electro-catalytic glycerol / ethylene glycol (J. Catal., 2017, 356, 14-21; Chem Catal., 2021, 1, 941-955), but the current density is difficult to meet the needs of industrial production (>300 mA cm -2 ) and the selectivity of lactic acid / glycolic acid and the faradic efficiency still need to be improved. SUMMARY

[0005] The present application is proposed to overcome the shortcomings of the prior art of the preparation of polybasic acid by electrocatalysis of polyhydric alcohol, and aims to provide a method for the preparation of polybasic acid by electrocatalysis of polyhydric alcohol coupled with hydrogen production, for example, to fully utilize the excess glycerol and ethylene glycol, and to convert the glycerol and ethylene glycol into more valuable lactic acid and glycolic acid under a large current density.

[0006] The present application is realized by the following technical solutions:

[0007] The present application is realized by the following technical solutions:

[0008] (I) Assembling an electrolytic cell

[0009] An electrically conductive substrate loaded with an anode catalyst is used as an anode, a cathode catalyst is used as a cathode, and an electrolyte is assembled into an electrolytic cell;

[0010] The anode catalyst is a hydroxide-loaded noble metal;

[0011] (II) Electro-catalytic reaction

[0012] Polyhydric alcohol is added to the electrolyte, and under the voltage condition, the polyhydric alcohol is oxidized at the anode to generate polybasic acid, and water is reduced at the cathode to generate hydrogen.

[0013] In the above technical solution, the polyhydric alcohol is glycerol, ethylene glycol, glucose, sorbitol, arabinose, xylitol, etc.

[0014] In the above technical solution, when the polyhydric alcohol is glycerol, the polybasic acid is lactic acid; when the polyhydric alcohol is ethylene glycol, the polybasic acid is glycolic acid; when the polyhydric alcohol is glucose, the polybasic acid is gluconic acid, glucaric acid or glycolic acid; when the polyhydric alcohol is sorbitol, arabinose, xylitol, the polybasic acid is lactic acid or glycolic acid.

[0015] In the above technical solution, the noble metal is any one or several of platinum, gold, silver, ruthenium, iridium, palladium, copper or rhodium.

[0016] In the above technical solution, the hydroxide is a nickel-based, cobalt-based, copper-based hydroxide or hydrotalcite material.

[0017] In the above technical solution, the preparation method of the hydroxide is electrodeposition, hydrothermal method or etching method.

[0018] In the above technical solution, the preparation method of the anode is electrodeposition or liquid phase reduction.

[0019] In the technical scheme, the electrolyte is one or more of aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate and sodium carbonate, and the concentration of electrolyte in the electrolyte is 20-300 g / L.

[0020] In the technical scheme, the cathode catalyst is any one or mixture of several of transition metal oxide, transition metal phosphide, transition metal sulfide, transition metal nitride, transition metal boride, platinum-based catalyst, palladium-based catalyst, ruthenium-based catalyst, rhodium-based catalyst, nickel-based catalyst or copper-based catalyst; when the cathode catalyst is powder, the cathode is composed of the conductive substrate loaded with the cathode catalyst.

[0021] In the technical scheme, the conductive substrate is any one of carbon cloth, carbon paper, nickel foam, nickel sheet, nickel mesh, copper foam, copper sheet, copper mesh, titanium sheet, titanium mesh, stainless steel sheet, stainless steel mesh, ITO conductive glass or FTO conductive glass.

[0022] In the technical scheme, the concentration of polyol in the electrolyte is 1-50 g / L.

[0023] In the technical scheme, the voltage of the electrocatalytic reaction in step (II) is 0-2 V vs Ag / AgCl.

[0024] A catalyst for electrocatalytic preparation of polyol acid from polyol, the catalyst is a hydroxide supported noble metal, the hydroxide is nickel-based, cobalt-based, copper-based hydroxide or hydrotalcite material; the noble metal is any one or several of platinum, gold, silver, ruthenium, iridium, palladium, copper or rhodium; the catalyst is prepared by electrodeposition method, hydrothermal method, etching method and liquid phase reduction method; the catalyst is used as anode catalyst in electrocatalytic reaction.

[0025] Application of a hydroxide supported noble metal catalyst for electrocatalytic preparation of polyol acid from polyol.

[0026] The beneficial effects of the present application are:

[0027] The application provides a method for preparing polyol acid by coupling hydrogen production through electrocatalysis of polyol, constructs noble metal / hydroxide as an anode electrocatalyst, uses hydrogen atom / oxygen atom in water as [H] / [O] source in an oxidation-reduction reaction, uses hydrogen bond interaction between a hydroxyl group on the surface of the hydroxide and a hydroxyl group of the polyol to adsorb and enrich the polyol on the surface of the catalyst, improves local concentration of the reactant, thereby improving current density, and makes the current density meet the demand of industrial production, meanwhile, water is reduced to hydrogen gas at the cathode, and the industrial application potential is further improved; the method can realize efficient electrocatalysis of polyol (such as glycerol, ethylene glycol) to prepare polyol acid (such as lactic acid, glycolic acid) under room temperature and normal pressure, simultaneously produces hydrogen gas at the cathode, and provides a new idea and method for green and efficient preparation of polyol acid (such as lactic acid, glycolic acid). BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a reaction principle schematic diagram of the application (taking lactic acid as an example);

[0029] Figure 2 is a scanning electron microscope graph of the anode catalyst in example 1 of the application;

[0030] Figure 3 is an X-ray diffraction graph of the anode catalyst in example 1 of the application;

[0031] Figure 4 is a linear polarization curve graph of the anode catalyst in example 1 of the application for electrocatalysis of glycerol;

[0032] Figure 5 is a current density comparison graph of the anode catalyst in example 1 of the application with literature;

[0033] Figure 6 is a high performance liquid chromatogram of the glycerol oxidation product in example 1 of the application;

[0034] Figure 7 is a scanning electron microscope graph of the anode catalyst in example 2 of the application;

[0035] Figure 8 is a high performance liquid chromatogram of the ethylene glycol oxidation product in example 2 of the application;

[0036] Figure 9 is a scanning electron microscope graph of the anode catalyst in example 3 of the application;

[0037] Figure 10 is a high performance liquid chromatogram of the ethylene glycol oxidation product in example 3 of the application.

[0038] For those skilled in the art, other related drawings can be obtained according to the above drawings without creative labor. DETAILED DESCRIPTION

[0039] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application are further described below in combination with the drawings of the specification and through specific embodiments.

[0040] Example 1

[0041] Electrocatalytic glycerol to lactic acid coupled with hydrogen production:

[0042] (1) Preparation of anode and cathode

[0043] A. Preparation of anode (foam nickel supported Au / Ni(OH)2)

[0044] First, foam nickel supported Ni(OH)2was prepared by the following method: first, foam nickel was ultrasonically treated in ethanol for 5 minutes, then immersed in dilute hydrochloric acid for 1 hour, followed by ultrasonic treatment in deionized water for 5 minutes, and finally placed in a reaction kettle containing deionized water and reacted at 60°C for 5 days to obtain foam nickel supported Ni(OH)2.

[0045] Then, foam nickel supported Au / Ni(OH)2was prepared by the following method: a 10 mM chloroauric acid solution was prepared and 0.5 M boric acid was added, and a three-electrode system was formed with foam nickel supported Ni(OH)2as the working electrode, a platinum sheet as the counter electrode, and a saturated calomel electrode as the reference electrode; electrodeposition was carried out at -1 V vs Ag / AgCl for 600 s to obtain the anode, i.e., foam nickel supported Au / Ni(OH)2.

[0046] The scanning electron microscope image and X-ray diffraction pattern of the obtained anode catalyst Au / Ni(OH)2are shown in Figure 2 , 3 As can be seen from Figure 2 / 3, the Ni(OH)2is a nanosheet array structure, and gold particles are distributed on the nanosheet array with a particle size of 100 nm to 200 nm.

[0047] B. Preparation of cathode (platinum sheet)

[0048] A platinum sheet with a size of 15 mm*15 mm*2 mm was cut, and the cut platinum sheet was rinsed with deionized water and ready for use.

[0049] (2) Preparation of electrolyte

[0050] 5 g of glycerol was added to 100 mL of a 50 g / L NaOH aqueous solution to obtain the electrolyte.

[0051] (3) Electrocatalytic reaction

[0052] The anode (foam nickel supported Au / Ni(OH)2) and the cathode (platinum plate) obtained in step (1) were placed into the electrolyte obtained in step (2) to form an electrolytic cell, and then lactic acid was prepared by electrolysis at room temperature and pressure, under a bias of 1.0 V vs RHE for 1 h.

[0053] (4) Detection

[0054] After the reaction, 1 mL of the reaction solution was taken and neutralized with acid, and the impurities were filtered off. The product was detected by high performance liquid chromatography, and the results are shown in Table 1. The selectivity of lactic acid was 80%. At the same time, the total faradic efficiency was calculated to be 100% by the liquid phase results. Figure 6 Figure 4 The linear polarization curve of the anode catalyst of this embodiment for electrocatalysis of glycerol and the current density of the anode catalyst of this embodiment are shown in Figures 1 and 2, respectively. Figure 5 It can be seen from the comparison with the literature that the current density of Au / Ni(OH)2 at 0.95 V and 1.05 V vs RHE is as high as 384 mA cm-2 and 605 mA cm-2, respectively, which is much higher than the reported values in the prior art. -2 -2 The total faradic efficiency was 100% as calculated from the liquid phase results.

[0055] Example 2

[0056] Electrocatalytic preparation of glycolic acid coupled with hydrogen production from ethylene glycol:

[0057] (1) Preparation of anode and cathode

[0058] A. Preparation of anode (foam copper supported Pd / Co(OH)2)

[0059] First, foam copper supported Co(OH)2 was prepared by configuring a 0.2 M cobalt nitrate solution as an electrolyte, using foam copper as a working electrode, platinum as a counter electrode, and a saturated calomel electrode as a reference electrode to form a three-electrode system, and then electrodeposition was carried out at -1.2 V for 300 s to obtain foam copper supported Co(OH)2.

[0060] Then, foam copper supported Pd / Co(OH)2 was prepared by configuring a 2 mM potassium chloropalladite solution, placing the foam copper supported Pd / Co(OH)2 in the solution, and adding 0.5 g of sodium borohydride under stirring to prepare foam copper supported Pd / Co(OH)2.

[0061] The scanning electron microscope image of the obtained anode catalyst Pd / Co(OH)2 is shown in Figure 3. Figure 7

[0062] B. Preparation of cathode (carbon cloth supported cobalt phosphide) ​​​

[0063] A 0.2 M cobalt nitrate solution was prepared, and carbon cloth was used as the working electrode, platinum plate as the counter electrode, and saturated calomel electrode as the reference electrode to form a three-electrode system. Co(OH)2-loaded carbon cloth was obtained by electrodeposition at -1.2 V for 300 s; 1 g of sodium hypophosphite and Co(OH)2-loaded carbon cloth were simultaneously placed in a tube furnace, purged with Ar gas, and calcined at 300 °C for 2 h to obtain CoP-loaded carbon cloth.

[0064] (2) Preparation of electrolyte

[0065] 3.5 g of ethylene glycol was added to 100 mL of a 60 g / L KOH aqueous solution to obtain the electrolyte.

[0066] (3) Electrocatalytic reaction

[0067] The anode (Pd / Co(OH)2-loaded foam copper) and the cathode (CoP-loaded carbon cloth) obtained in step (1) were placed in the electrolyte obtained in step (2) to form an electrolytic cell, and then glycolic acid was prepared by electrolysis at room temperature and pressure under a bias of 1.1 V vs RHE for 1 h. The total Faraday efficiency was 100% according to the calculation of the Faraday efficiency from the liquid phase results.

[0068] (4) Detection

[0069] After the reaction, 1 mL of the reaction solution was taken and neutralized with acid, and the impurities were filtered off. The product was detected by high performance liquid chromatography, and the results are shown in Table 1. The selectivity of glycolic acid was 95%. Figure 8

[0070] Example 3: Preparation of lactic acid coupled with hydrogen production by electrocatalytic glycerol

[0071] (1) Preparation of anode and cathode

[0072] A. Preparation of anode (Pt / NiFe(OH) x -loaded titanium mesh)

[0073] First, NiFe(OH) x -loaded titanium mesh was prepared by the following method: 80 mL of a mixed solution of 0.25 mmol of nickel nitrate and 0.15 mmol of ferrous sulfate was prepared, and 1.25 mmol of ammonium fluoride and 9 mmol of uric acid were added. After stirring, the cleaned titanium mesh was placed in the solution. NiFe(OH) x was prepared by reacting at 120 °C for 6 h.Then, Au / NiFe(OH) x -loaded titanium mesh was prepared by the following method: a 10 mM chloroplatinic acid solution was prepared, and 0.15 M sodium chloride was added as the electrolyte. Au / NiFe(OH) xThe three-electrode system was configured with the anode as a working electrode, a platinum plate as a counter electrode, and a saturated calomel electrode as a reference electrode, and the anode, i.e., a Pt / NiFe(OH) x .

[0074] The scanning electron microscope image of the obtained anode catalyst Pt / NiFe(OH) x is shown in Figure 9 .

[0075] B. Preparation of a cathode (nickel mesh loaded nickel sulfide)

[0076] A three-electrode system was configured with a 0.2M nickel nitrate solution as an electrolyte, a nickel mesh as a working electrode, a platinum plate as a counter electrode, and a saturated calomel electrode as a reference electrode. The nickel mesh loaded Ni(OH)2 was obtained by electrodeposition at-1.2V for 300s; the nickel mesh loaded Ni(OH)2 and 0.1g thioacetamide were put into an autoclave and reacted at 120℃ for 6h to obtain a nickel mesh loaded nickel sulfide, i.e., the cathode.

[0077] (2) Preparation of an electrolyte

[0078] 10g ethylene glycol was added to 100mL of a 100g / L KOH aqueous solution to obtain an electrolyte.

[0079] (3) Electrocatalytic reaction

[0080] The anode (Pt / NiFe(OH) x ) and the cathode (nickel mesh loaded nickel sulfide) obtained in step (1) were put into the electrolyte obtained in step (2) to form an electrolytic cell, and then glycolic acid was prepared by electrolysis at room temperature and pressure and at a bias of 1.2V vs RHE for 1h.

[0081] (4) Detection

[0082] After the reaction was completed, 1mL of the reaction solution was taken and neutralized with acid, and the impurities were filtered off, and then the product was detected by high performance liquid chromatography, and the results are shown in Figure 10 . The selectivity of glycolic acid was 86%, and the total Faraday efficiency was 100% according to the calculation of the Faraday efficiency from the liquid phase results.

[0083] Design principle of the application:

[0084] As Figure 1As shown, the present application constructs noble metal / hydroxide as an anode electrocatalyst, uses hydrogen atom / oxygen atom in water as [H] / [O] source in redox reaction, uses hydrogen bond interaction between hydroxyl group on hydroxide surface and polyol hydroxyl group to adsorb and enrich polyol on catalyst surface, improves local concentration of reactants to improve current density, so as to meet the needs of industrial production, and water is reduced to hydrogen gas at the cathode.

[0085] The chemical reaction equation is:

[0086] (1) Taking glycerol as an example

[0087] The anode reaction is: C3H8O3+2OH - -2e - →C3H6O3+2H2O;

[0088] The cathode reaction is: 2H2O+2e - →H2+2OH - .

[0089] (2) Taking ethylene glycol as an example

[0090] The anode reaction is: C2H6O2+4OH - -4e - →C2H4O3+2H2O;

[0091] The cathode reaction is: 2H2O+2e - →H2+2OH - .

[0092] The present application responds to the call of a sustainable development society, and develops a production method for efficiently and greenly preparing polyol acid from polyol, which adsorbs and enriches polyol through hydrogen bond interaction between hydroxyl group on hydroxide surface and polyol hydroxyl group, so as to greatly improve the reaction rate, and provides a new idea and method for efficiently and greenly preparing polyol acid.

[0093] The applicant declares that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for the electrocatalytic polyol production of polyol acid coupled hydrogen generation, characterized by: The method comprises the following steps: (I) assembling an electrolytic cell Assembling an electrolytic cell with a conductive substrate loaded with an anode catalyst as an anode, a cathode catalyst as a cathode, and an electrolyte; The anode catalyst is a hydroxide-supported noble metal; the hydroxide is a nickel-based, cobalt-based, or copper-based hydrotalcite material; the concentration of the electrolyte in the electrolyte is 60 g / L to 300 g / L; The cathode catalyst is any one or a mixture of several of a transition metal oxide, a transition metal phosphide, a transition metal sulfide, a transition metal nitride, or a transition metal boride; (II) electrocatalytic reaction Adding a polyol to the electrolyte, and under a voltage condition, the polyol is oxidized to a polyol acid at the anode, and water is reduced to hydrogen at the cathode.

2. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: The polyol is glycerol, ethylene glycol, glucose, sorbitol, arabinose, or xylitol; the polyol acid is lactic acid, glycolic acid, gluconic acid, or saccharic acid.

3. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: The noble metal is any one or several of platinum, gold, silver, ruthenium, iridium, palladium, copper, or rhodium.

4. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: The electrolyte is one or several aqueous solutions of sodium hydroxide, potassium hydroxide, lithium hydroxide, potassium bicarbonate, potassium carbonate, sodium bicarbonate, or sodium carbonate.

5. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: When the cathode catalyst is a powder, the cathode is composed of a conductive substrate loaded with the cathode catalyst.

6. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: The concentration of the polyol in the electrolyte is 1 g / L to 50 g / L.

7. The method of claim 1, wherein the electrocatalytic polyol production polyol acid coupling hydrogen production is characterized by: The voltage of the step (II) electrocatalytic reaction is 0 V to 2 V vs Ag / AgCl.

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