A method for preparing glyceric acid by electrocatalytic oxidation of glycerol

Abstract

A method for preparing glyceric acid by electrocatalytic oxidation of glycerol is disclosed. Glycerol is used as a reactant and electrocatalytically oxidized in a potassium hydroxide solution at room temperature and normal pressure to prepare glyceric acid. The catalyst is a platinum catalyst supported on lanthanum oxyfluoride, and the platinum loading is no more than 20 wt%. The catalyst is prepared as follows: lanthanum nitrate and ammonium fluoride are fully dissolved in an aqueous solution at a molar ratio of 1:1, adjusted to a weakly alkaline state, stirred evenly, and then centrifuged, washed, and centrifuged to obtain a lanthanum oxyfluoride carrier; the resulting solid is dried, calcined, and ground to obtain the lanthanum oxyfluoride; platinum nitrate and lanthanum oxyfluoride are heated and stirred in water to evaporate to dryness, so that the platinum is impregnated on the lanthanum oxyfluoride carrier; the resulting solid is dried and calcined, and the platinum nitrate is converted to platinum after calcination. The catalyst for preparing glyceric acid by electrocatalytic oxidation of glycerol has high catalytic reaction activity and simple reaction conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing glyceric acid from glycerol, and in particular to a method for preparing glyceric acid from glycerol by electrocatalytic oxidation. Background Art

[0002] The catalytic conversion of glycerol into high-value-added chemicals or fuels can not only solve the problem of excess biodiesel by-products and avoid their pollution of the environment, but also meet the demand for glyceric acid and its downstream products and reduce costs, which is of great practical significance.

[0003] A comparison of the production economics of different products from the electrocatalytic oxidation of glycerol (such as formic acid, glycolic acid, glyceraldehyde, oxalic acid, and glyceric acid) revealed that glyceric acid is the most economically viable product. Glyceric acid promotes ethanol metabolism and has high pharmaceutical value. Glyceric acid-derived oligoesters exhibit antitrypsin activity, helping to promote alcohol decomposition in the human body.

[0004] Currently, there are two methods for catalytic oxidation of glycerol: biomass catalytic oxidation and oxidant oxidation. Biomass oxidation is the selective oxidation of the hydroxyl groups of glycerol by microbial fermentation. The biomass oxidation products usually contain a large number of microorganisms and impurities, which is not conducive to subsequent separation, has a long production cycle, and has high environmental requirements. Oxidant oxidation is the most commonly used method for glycerol oxidation, and the glyceric acid product of glycerol oxidation has also reached a high level. However, due to the large amount of precious metals, the price of the catalyst still accounts for 95% of the production cost of high-value-added products such as dihydroxyacetone, tartaric acid, and oxalic acid. In addition, precious metal catalysts are poisoned or deactivated after the reaction. Therefore, it is very meaningful to develop a stable carrier while reducing the amount of precious metals to achieve the catalytic effect. Summary of the Invention

[0005] The object of the present invention is to solve the above-mentioned problems in the prior art and to provide a method for preparing glyceric acid by electrocatalytic oxidation of glycerol, which can convert glycerol into glyceric acid in one step quickly under mild reaction conditions.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for producing glyceric acid by electrocatalytic oxidation of glycerol comprises electrocatalytic oxidation of glycerol as a reactant in a potassium hydroxide solution at room temperature and atmospheric pressure to produce glyceric acid. The catalyst is a lanthanum oxyfluoride-supported platinum catalyst, and the platinum loading is no more than 20 wt %. Preferably, the platinum loading is 15 wt %.

[0008] The present invention adopts a three-electrode system, 0.5 mol / L potassium hydroxide and 0.1 mol / L glycerol solution, normal pressure, room temperature, the solution stirring speed is 600 r / min, and the reaction time is 1 to 4 hours.

[0009] The catalyst preparation method is as follows: lanthanum nitrate and ammonium fluoride are fully dissolved in an aqueous solution according to a certain ratio, adjusted to a weak alkaline state, heated and stirred uniformly, and then centrifuged, washed, centrifuged, dried, and calcined to obtain a lanthanum oxyfluoride carrier; the obtained lanthanum oxyfluoride carrier is impregnated with platinum nitrate at room temperature, stirred, dried, and reduced at 200-450° C. for 1-3 hours in an air atmosphere to precipitate platinum metal by in-situ reduction.

[0010] The molar ratio of the lanthanum nitrate to the ammonium fluoride is 1:1.

[0011] The temperature of the heating and stirring is 70-120°C.

[0012] The calcination temperature is 800° C., the calcination time is 2 to 4 hours, and the heating rate is 2 to 5° C. / min.

[0013] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0014] Traditional glyceric acid production methods are limited and suffer from high energy consumption, multiple reaction steps, and long reaction times. The present invention utilizes electrocatalytic oxidation to produce glyceric acid, which avoids many of the drawbacks of stoichiometric and biomass oxidation processes. The process is simple and can be performed at room temperature. Furthermore, by controlling the catalyst composition and reaction variables such as electrode potential, electrolyte pH, glycerol concentration, reaction temperature, and reaction time, the product formation pathway can be well controlled, improving product selectivity.

[0015] The present invention uses metal nitrate as raw material and prepares a low-cost, large-scale catalyst for electrocatalytic oxidation of glycerol to glyceric acid through a deposition precipitation method and an impregnation method. The preparation process is simple and reduces the pollution of the solvent to the environment, and can be used in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a scanning electron microscope image of the 15% Pt / LaOF catalyst;

[0017] Figure 2 XRD patterns of LaOF, 5%wt Pt / LaOF, 10%wt Pt / LaOF, 15%wt Pt / LaOF, 20%wt Pt / LaOF, La2O3, and 15%Pt / La2O3 catalysts;

[0018] Figure 3 Linear sweep voltammograms of 5% wt Pt / LaOF, 10% wt Pt / LaOF, 15% wt Pt / LaOF, and 20% wt Pt / LaOF catalysts;

[0019] Figure 4XPS graphs of 15% wt Pt / LaOF and 15% wt Pt / La2O3. DETAILED DESCRIPTION

[0020] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer and more understandable, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0021] Example 1

[0022] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 5% of the mass of the lanthanum oxyfluoride.

[0023] The preparation method of the above catalyst specifically comprises the following steps:

[0024] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 5% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 5% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0025] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.5 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured a glycerol conversion of 6.5% and a glyceric acid selectivity of 14.4%.

[0026] Example 2

[0027] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 10% of the mass of the lanthanum oxyfluoride.

[0028] The preparation method of the above catalyst specifically comprises the following steps:

[0029] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 10% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 10% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0030] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.5 V, the pressure was 101 kPa at normal pressure, the temperature was 25° C., the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 12.6%, and the glyceric acid selectivity to be 12.2%.

[0031] Example 3

[0032] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 15% of the mass of the lanthanum oxyfluoride.

[0033] The preparation method of the above catalyst specifically comprises the following steps:

[0034] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 15% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 15% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid. Figure 1 This is an electron micrograph of the prepared catalyst.

[0035] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.5 V, the pressure was 101 kPa at normal pressure, the temperature was 25° C., the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion rate to be 26.3%, and the glyceric acid selectivity to be 25.7%.

[0036] Example 4

[0037] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 20% of the mass of the lanthanum oxyfluoride.

[0038] The preparation method of the above catalyst specifically comprises the following steps:

[0039] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 20% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 20% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0040] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.5 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion rate to be 25.3%, and the glyceric acid selectivity to be 5.7%.

[0041] Figure 2 The XRD patterns of the platinum-supported lanthanum oxyfluoride catalysts prepared in Examples 1 to 4 show that the 5% wt Pt / LaOF, 10% wt Pt / LaOF, 15% wt Pt / LaOF, and 20% wt Pt / LaOF prepared in the present invention are all pure phases, showing strong lanthanum oxyfluoride diffraction peaks, and no characteristic diffraction peaks of Pt are observed, indicating that Pt is highly dispersed on the surface of the lanthanum oxyfluoride catalyst.

[0042] Example 5

[0043] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 5% of the mass of the lanthanum oxyfluoride.

[0044] The preparation method of the above catalyst specifically comprises the following steps:

[0045] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 5% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 5% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0046] The catalyst prepared in this example was used in the electrocatalytic oxidation of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.55 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 20.4%, and the glyceric acid selectivity to be 10.6%.

[0047] Example 6

[0048] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 10% of the mass of the lanthanum oxyfluoride.

[0049] The preparation method of the above catalyst specifically comprises the following steps:

[0050] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 10% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 10% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0051] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.55 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 r / min, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 17.7%, and the glyceric acid selectivity to be 12.0%.

[0052] Example 7

[0053] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 15% of the mass of the lanthanum oxyfluoride.

[0054] The preparation method of the above catalyst specifically comprises the following steps:

[0055] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 15% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 15% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0056] The catalyst prepared in this example was used in the electrocatalytic oxidation of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.55 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 r / min, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion rate to be 21.4%, and the glyceric acid selectivity to be 7.8%.

[0057] Example 8

[0058] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 20% of the mass of the lanthanum oxyfluoride.

[0059] The preparation method of the above catalyst specifically comprises the following steps:

[0060] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 20% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 20% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0061] The catalyst prepared in this example was used in the electrocatalytic oxidation of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.55 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion rate to be 21.2%, and the glyceric acid selectivity to be 7.1%.

[0062] Example 9

[0063] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 5% of the mass of the lanthanum oxyfluoride.

[0064] The preparation method of the above catalyst specifically comprises the following steps:

[0065] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 5% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 5% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0066] The catalyst prepared in this example was used in the electrocatalytic oxidation of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.6 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography revealed a glycerol conversion of 6.8% and a glyceric acid selectivity of 13.9%.

[0067] Example 10

[0068] A catalyst for electrocatalytic oxidation of glycerol to produce glyceric acid. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 10% of the mass of the lanthanum oxyfluoride.

[0069] The preparation method of the above catalyst specifically comprises the following steps:

[0070] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 10% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 10% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0071] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.6 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 r / min, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 10.4%, and the glyceric acid selectivity to be 11.3%.

[0072] Example 11

[0073] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 15% of the mass of the lanthanum oxyfluoride.

[0074] The preparation method of the above catalyst specifically comprises the following steps:

[0075] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 15% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 15% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0076] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.6 V, the pressure was 101 kPa at normal pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 18.2%, and the glyceric acid selectivity to be 7.1%.

[0077] Example 12

[0078] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol. The molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, wherein the mass fraction of Pt is 20% of the mass of the lanthanum oxyfluoride.

[0079] The preparation method of the above catalyst specifically comprises the following steps:

[0080] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and rapidly stirred until the solid was completely dissolved. Sodium hydroxide solution was then added dropwise to the mixed solution to adjust the pH value of the solution to approximately 10. The solution was then stirred at 550 r / min, heated at 50° C. for 5 h, centrifuged at 10,000 r / min for 5 min, washed three times with deionized water, dried at 60° C. for 2 h, and calcined at 800° C. for 3 h to obtain LaOF. The LaOF was transferred to a beaker, impregnated with 20% wt Pt at 50° C., stirred and dried, and then calcined at 400° C. for 2 h to obtain 20% wt Pt / LaOF, thereby obtaining a catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0081] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.6 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion rate to be 20.8%, and the glyceric acid selectivity to be 6.4%.

[0082] Comparative Example 1

[0083] A catalyst for preparing glyceric acid through electrocatalytic oxidation of glycerol, wherein the molar ratio of fluorine to lanthanum in the lanthanum oxyfluoride catalyst is 1:1, and no Pt is loaded.

[0084] The preparation method of the above catalyst specifically comprises the following steps:

[0085] 1.7320 g of lanthanum nitrate hexahydrate and 0.1428 g of ammonium fluoride were dissolved in 50 mL of deionized water and stirred rapidly until the solid was completely dissolved. Sodium hydroxide solution was added dropwise to the mixed solution to adjust the pH value of the solution to about 10. At this time, the solution was stirred at 550 r / min, heated at 50°C for 5 hours, centrifuged at 10,000 r / min for 5 minutes, washed with deionized water three times, dried at 60°C for 2 hours, and calcined at 800°C for 3 hours to obtain LaOF solid catalyst for the electrocatalytic oxidation of glycerol to glyceric acid.

[0086] The catalyst prepared in this example was used in an electrocatalytic oxidation reaction of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution, a three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode. The voltage was set to 0.5 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography measured the glycerol conversion to be 6.0%, and the glyceric acid selectivity to be 11.7%.

[0087] Figure 3 The linear sweep voltammograms of 5% wt Pt / LaOF, 10% wt Pt / LaOF, 15% wt Pt / LaOF, and 20% wt Pt / LaOF catalysts show that there is an obvious oxidation peak around 0.55 V. An oxidation reaction occurs at the glycerol carboxyl group around 0.55 V, and glycerol is initially oxidized to glyceraldehyde at the platinum active site on the catalyst surface. Glyceraldehyde spontaneously turns into glyceric acid in an alkaline environment. When the generated glyceric acid does not leave the catalyst surface in time or is re-adsorbed, over-oxidation of the three-carbon product occurs, turning it into oxalic acid or formic acid. This is also the reason for the high selectivity of formic acid.

[0088] Comparative Example 2

[0089] A catalyst for preparing glyceric acid by electrocatalytic oxidation of glycerol is a lanthanum oxide catalyst, wherein the mass fraction of Pt is 15% of the mass of the lanthanum oxide.

[0090] The method for preparing the lanthanum oxide catalyst for catalyzing the electrocatalytic oxidation of glycerol to produce glyceric acid comprises the following steps:

[0091] A certain amount of lanthanum nitrate hexahydrate was calcined at 800℃ in a muffle furnace for 2h to obtain La2O3. 0.5g of La2O3 was taken, impregnated with 15wt% Pt at 50℃ and dried, and calcined at 300℃ for 2h to obtain a 15wt% Pt-loaded La2O3 catalyst.

[0092] The lanthanum oxide catalyst prepared in this example was used in the electrocatalytic oxidation of glycerol. The reaction conditions were 0.5 mol / L potassium hydroxide and 30 mL of a 0.1 mol / L glycerol aqueous solution. A three-electrode system consisting of a silver-silver chloride reference electrode, a carbon rod counter electrode, and a carbon fiber paper-supported catalyst working electrode was used. The voltage was set to 0.55 V, the pressure was 101 kPa at atmospheric pressure, the temperature was 25°C, the rotation speed was 600 rpm, and the reaction time was 4 hours. Liquid chromatography revealed a glycerol conversion of 1.8% and a glyceric acid selectivity of 0%.

[0093] Compared with Comparative Example 1, Example 3 has a glycerol conversion rate of 26.3% and a glyceric acid selectivity of 25.7%, which are 2 to 4 times higher than the glyceric acid conversion of the lanthanum oxyfluoride catalyst without platinum under the same conditions.

[0094] Comparing Example 6 with Comparative Example 2, the conversion rate of glycerol in Example 6 was 17.7%, while the conversion rate of glyceric acid of the catalyst without fluorine composition under the same conditions was 1.8%.

[0095] Figure 4The XPS graphs of 15% wt Pt / LaOF and 15% wt Pt / La2O3 show that the lower binding energy of 529.3-529.9 eV belongs to the lattice oxygen (O 2- latt); the intermediate binding energy is the surface adsorbed oxygen (O 2- / O - ) and oxygen vacancies (Vo) (Oads: 530.4-531.7 eV); the peak with higher binding energy is attributed to oxygen from chemically adsorbed water molecules (OOH: 532.3 eV). XPS results indicate that the addition of fluorine reduces oxygen vacancies and increases lattice oxygen, which is beneficial for the electrocatalytic oxidation of glycerol. Therefore, the present invention utilizes LaOF as a carrier to support Pt, which can enhance the catalytic activity of glycerol to produce glyceric acid.

Claims

1. A method for preparing glyceric acid by electrocatalytic oxidation of glycerol, characterized in that: At normal pressure and room temperature, glycerol is used as a reactant and electrocatalytically oxidized in a potassium hydroxide solution to produce glyceric acid. The catalyst is a platinum catalyst supported by lanthanum oxyfluoride, and the platinum loading is not higher than 20 wt%.

2. The method for preparing glyceric acid by electrocatalytic oxidation of glycerol according to claim 1, wherein: The platinum loading was 15 wt%.

3. The method for preparing glyceric acid by electrocatalytic oxidation of glycerol according to claim 1, wherein: The catalyst preparation method is as follows: lanthanum nitrate and ammonium fluoride are fully dissolved in an aqueous solution according to a certain ratio, adjusted to a weak alkaline state, heated and stirred uniformly, and then centrifuged, washed, centrifuged, dried, and calcined to obtain a lanthanum oxyfluoride carrier; the obtained lanthanum oxyfluoride carrier is impregnated with platinum salt at room temperature, stirred, dried, and reduced at 200-450° C. for 1-3 hours in an air atmosphere to precipitate platinum metal by in-situ reduction.

4. The method for preparing glyceric acid by electrocatalytic oxidation of glycerol according to claim 3, wherein: The molar ratio of the lanthanum nitrate to the ammonium fluoride is 1:

1.

5. The method for preparing glyceric acid by electrocatalytic oxidation of glycerol according to claim 3, wherein: The temperature of the heating and stirring is 70-120°C.

6. The method for preparing glyceric acid by electrocatalytic oxidation of glycerol according to claim 3, wherein: The calcination temperature is 800° C., the calcination time is 2 to 4 hours, and the heating rate is 2 to 5° C. / min.

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