Method for synthesizing glycine by electrocatalysis of oxalic acid coupling nitrate with molecular catalyst lead phthalocyanine

Abstract

The invention discloses a method for synthesizing glycine by coupling oxalic acid with nitrate under the electro-catalysis of a molecular catalyst lead phthalocyanine, and belongs to the technical field of materials and electro-catalysis. The method comprises the following steps: uniformly mixing lead phthalocyanine, a dispersing agent and a binding agent to prepare catalyst slurry; loading the catalyst slurry on carbon paper to obtain carbon paper containing a catalyst; an H-type electrolytic tank is assembled, in the H-type electrolytic tank, an electrolyte of an anode chamber is a sulfuric acid solution, an electrolyte of a cathode chamber is a sulfuric acid solution containing oxalic acid and potassium nitrate, and the cathode chamber and the anode chamber are separated through an ion exchange membrane; a calomel electrode is inserted into the cathode chamber as a reference electrode, carbon paper containing a catalyst is used as a working electrode, a platinum sheet is inserted into the anode chamber as a counter electrode, and glycine is obtained through electrolysis. The glycine is prepared by using the lead phthalocyanine as the catalyst, so that the reaction efficiency can be effectively improved, the reaction energy consumption is reduced, and the production process is simplified.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of materials and electrocatalysis, and more particularly to a method for synthesizing glycine by coupling oxalate and nitrate using a molecular catalyst phthalocyanine lead. BACKGROUND

[0002] Alpha-amino acids are the basic building blocks of important biomolecules in proteins and life systems, and are widely used in drug development, food technology, material science, etc. Traditional amino acid synthesis methods, such as Strecker amino acid synthesis, usually involve highly toxic cyanide and have poor solubility. Enzymatic hydrolysis, although having the advantages of short reaction time and simple operation, is often limited by temperature and pH. Hydrolysis requires high-temperature and high-pressure equipment and high operating costs. Glycine, as the simplest amino acid, is widely used in daily life. Compared with traditional amino acid synthesis methods, electrochemical synthesis of glycine has the advantages of simple process, mild reaction conditions, and high product quality. The most ideal method for electrochemical synthesis of glycine is one-step electrolysis, but the C-N coupling process involves the transfer of multiple electrons, and in this process, multiple by-products are produced, plus the competition of hydrogen evolution reaction, so it is very challenging to achieve high selectivity and high Faraday efficiency for electrochemical synthesis of glycine.

[0003] The most commonly used carbon source for electrochemical synthesis of amino acids is some biomass-derived acids, such as pyruvic acid, glyoxylic acid, and 2-ketopentanoic acid, but often requires higher expenditure, reducing the industrial application. Selecting carbon-based molecules upstream of ketonic acids provides a strong competitive advantage in reducing the cost of electrochemical synthesis and promoting industrial implementation. The co-reduction of oxalic acid and nitrate mainly involves two half-reaction processes, including the electro-reduction of oxalic acid and the electro-reduction of nitrate. Oxalic acid can be obtained directly by CO2 electro-reduction, and existing studies have shown that a Faraday efficiency of more than 80% for the electro-reduction of CO2 to synthesize oxalic acid can be achieved at high current density. Using nitrate in wastewater as a nitrogen source, the intermediate hydroxylamine in the electro-reduction process has a strong nucleophilic ability on the nitrogen atom, while the carbonyl carbon of the intermediate glyoxylic acid generated by one-step reduction of oxalic acid has a strong electrical property. Hydroxylamine can undergo nucleophilic addition with the carbonyl group on the glyoxylic acid to form the key glyoxylic acid oxime precursor, which is further reduced to generate glycine. In the reaction process, both oxalic acid and nitrate are easily over-reduced to generate glycolic acid and ammonium, respectively, reducing the selectivity and Faraday efficiency of the reaction.

[0004] Traditional heterogeneous catalysts face many scientific and technological problems in the field of electrocatalytic CN coupling. First, traditional catalysts usually have low selectivity and activity, and strong competitive reactions, resulting in low product yields and many by-products. Secondly, these catalysts are easily deactivated at high current densities and cannot operate stably for a long time. In addition, the structure of heterogeneous catalysts is complex, and the active sites are difficult to precisely control, resulting in poor controllability of the catalytic process. Finally, the preparation and recovery process of the catalyst is complicated and the cost is high, making it difficult to achieve large-scale application. These problems restrict the widespread application of traditional heterogeneous catalysts in the field of electrocatalytic CN coupling.

[0005] Therefore, developing an environmentally friendly and cost-effective method for CN coupling electrosynthesis of glycine relying on inexpensive reactants has urgent practical significance and application value. Summary of the Invention

[0006] To address the above problems, the present invention provides a method for synthesizing glycine by electrocatalyzing the coupling of oxalic acid with nitrate using a molecular catalyst, lead phthalocyanine. The present invention uses lead phthalocyanine as a catalyst to prepare glycine, which can effectively improve reaction efficiency, reduce reaction energy consumption, and simplify the production process.

[0007] The present invention aims to provide a method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by using a molecular catalyst lead phthalocyanine, comprising the following steps: Lead phthalocyanine, a dispersant and a binder are uniformly mixed to prepare a catalyst slurry.

[0008] The catalyst slurry is loaded on the carbon paper to obtain the catalyst-containing carbon paper.

[0009] An H-type electrolytic cell is assembled. In the H-type electrolytic cell, the electrolyte in the anode chamber is a sulfuric acid solution, the electrolyte in the cathode chamber is a sulfuric acid solution containing oxalic acid and potassium nitrate, and the cathode chamber and the anode chamber are separated by an ion exchange membrane.

[0010] A calomel electrode is inserted into the cathode chamber as a reference electrode and carbon paper containing a catalyst is used as a working electrode. A platinum sheet is inserted into the anode chamber as a counter electrode for electrolysis. During the electrolysis process, a CN coupling co-reduction reaction is carried out to obtain glycine.

[0011] In a preferred embodiment of the present invention, the amount of lead phthalocyanine added to the carbon paper containing the catalyst is 1.5 mg / cm 2 ~2mg / cm 2 .

[0012] In a preferred embodiment of the present invention, in the sulfuric acid solution containing oxalic acid and gallium nitrate, the molar ratio of oxalic acid to potassium nitrate is 1:1.

[0013] In a preferred embodiment of the present invention, the current density during the electrolysis process is 150-500 mA / cm 2 .

[0014] In a preferred embodiment of the present invention, the electrolysis time is 4h~5h.

[0015] In a preferred embodiment of the present invention, the dispersant is water and ethanol, and the binder is Nafion solution.

[0016] In a preferred embodiment of the present invention, the volume ratio of Nafion solution, ethanol and water is 3:1:1.

[0017] In a preferred embodiment of the present invention, the ion exchange membrane is a Nafion 117 ion exchange membrane.

[0018] In a preferred embodiment of the present invention, the concentration of the sulfuric acid solution is 1 mol / L to 1.5 mol / L. Compared with the prior art, the present invention has the following beneficial effects: In view of the problems in the prior art of CN coupling electrosynthesis of glycine, such as increased by-products, reduced selectivity, and decreased Faradaic efficiency due to a large number of transferred electrons, the present invention uses lead phthalocyanine as a catalyst, oxalic acid and potassium nitrate solution as reactants, and performs co-reduction electrosynthesis through a one-step synthesis method. Nucleophilic addition of glyoxylic acid obtained by reduction with oxalic acid and hydroxylamine obtained by reduction with nitrate is performed to obtain a key intermediate glyoxylic acid oxime, which is promoted to be further reduced to obtain glycine. Ultimately, the goals of high Faradaic efficiency, high selectivity, and long-term stability are achieved.

[0019] This method, using lead phthalocyanine as a catalyst, boasts a simple structure, low production cost, and large-scale application. Systematic experiments demonstrate the feasibility and stability of the electrosynthesis of glycine using the molecular catalyst lead phthalocyanine to couple oxalic acid with nitrate. This method utilizes an innovative catalytic system, improving reaction efficiency, reducing reaction energy consumption, mitigating safety risks, and simplifying the production process, providing a technical reference for more economical and efficient glycine production. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the mechanism for preparing glycine according to the present invention.

[0021] Figure 2 This is a schematic diagram of the device structure used when the catalyst of the present invention is used.

[0022] Figure 3 This is a comparison of polarization curves of the catalyst lead phthalocyanine used in the examples in different cathode electrolytes.

[0023] Figure 41 is a graph evaluating the Faraday efficiency performance at different operating current densities of Examples 1 to 3 and Comparative Examples 1 to 6.

[0024] Figure 5 1 is a comparison diagram of the polarization curves of Example 1 and Comparative Examples 7 to 10 in 8 mL of 1M H2SO4 dissolved in 0.25 M oxalic acid and 0.25 M potassium nitrate electrolyte.

[0025] Figure 6 For Example 1 and Comparative Examples 7 to 10 at 150 mA / cm 2 Faraday efficiency diagram of each product at working current density.

[0026] Figure 7 The lead phthalocyanine catalyst of the present invention is 150 mA / cm 2 Cycling stability performance diagram under working current density.

[0027] Figure 8 This is a specific implementation diagram of the lead phthalocyanine catalyst of the present invention in MEA. DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] The present invention is a method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by using a molecular catalyst lead phthalocyanine. The mechanism diagram is shown in FIG. Figure 1 As shown, the specific steps include: S1: The molecular catalyst lead phthalocyanine was mixed with Nafion solution, ethanol and water and ultrasonically dispersed for 30 minutes to obtain a catalyst slurry.

[0030] Wherein, the molecular catalyst includes but is not limited to lead phthalocyanine.

[0031] The dispersant includes but is not limited to at least one of isopropyl alcohol, ethanol, acetone and water.

[0032] The binder includes but is not limited to 0.5% Nafion solution.

[0033] S2: The obtained catalyst slurry is evenly loaded on carbon paper (commercial carbon paper) and dried naturally to obtain a working electrode.

[0034] The loading method includes but is not limited to spraying and dipping.

[0035] The carbon paper has an area of ​​1×1 cm 2 , the catalyst loading is 1.5-2.5 mg / cm².

[0036] S3: The obtained working electrode is placed in an H-type electrolytic cell to perform a co-reduction test.

[0037] During the test, a Shanghai Chenhua CHI 760E electrochemical workstation was used, and argon was introduced at a flow rate of 5 mL / min to prevent air interference. At the same time, mechanical stirring was performed at a speed of about 500 rpm in the cathode chamber to enhance mass transfer. Figure 2 As shown, the reaction site is an H-type dual electrolytic cell, with the cathode and anode compartments separated by a proton exchange membrane (Nafion-117). The cathode chamber is filled with 8 mL of a mixture of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H₂SO₄, while the anode chamber is filled with 8 mL of a 1 M H₂SO₄ solution. The catalyst loading is typically 1.5-2.5 mg / cm². The working electrode is placed on the cathode side, with a calomel electrode (saturated potassium chloride) inserted as the reference electrode (RE). A Pt sheet electrode serves as the counter electrode (CE) in the anode compartment.

[0038] The chronopotentiometry was used to measure the current density of 150, 350, and 500 mA / cm 2 The test was conducted at 2600C with no current density applied, ensuring that the charge transferred in each test was 2600C to obtain the CN coupling product, glycine. H2 during the reaction was detected using a gas chromatograph and a 400 MHz Bruker nuclear magnetic resonance spectrometer.

[0039] It should be noted that the electrolyte after the electrolysis is an electrolyte containing glycine. Glycine can be obtained by purifying the electrolyte containing glycine according to conventional methods. Specifically, the electrolyte containing glycine is desalted and then freeze-dried to obtain the final glycine product.

[0040] The following are specific examples.

[0041] Example 1 Weigh 2.0 mg of molecular catalyst lead phthalocyanine (Pb Pc) catalyst powder and prepare it into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, drop-coat it on a 1 cm 2 Carbon paper was used as the working electrode.

[0042] The anode chamber was added with 8 mL of 1 M H2SO4 solution, and the cathode chamber was added with 8 mL of 1 M H2SO4 solution dissolved with 0.25 M oxalic acid and 0.25 M potassium nitrate mixed solution with equal volume. The prepared working electrode was placed in the cathode chamber, and a saturated potassium chloride standard electrode with a calomel electrode was inserted as a reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as a counter electrode (CE). Under the condition of 150 mA / cm 2 , electrolysis was performed for 5 h, and finally an electrolyte containing glycine was obtained.

[0043] Example 2 2.0 mg of molecular catalyst phthalocyanine lead (Pb Pc) catalyst powder was weighed and prepared into 1 mL slurry (200 μL of deionized water, 200 μL of ethanol, and 600 μL of 0.5 wt% Nafion solution). After ultrasonic mixing, it was drop-coated on a 1 cm 2 carbon paper as a working electrode.

[0044] The anode chamber was added with 8 mL of 1 M H2SO4 solution, and the cathode chamber was added with 8 mL of 1 M H2SO4 solution dissolved with 0.25 M oxalic acid and 0.25 M potassium nitrate mixed solution with equal volume. The prepared working electrode was placed in the cathode chamber, and a saturated potassium chloride standard electrode with a calomel electrode was inserted as a reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as a counter electrode (CE). Under the condition of 350 mA / cm 2 , electrolysis was performed for 2.2 h, and finally an electrolyte containing glycine was obtained.

[0045] Example 3 2.0 mg of molecular catalyst phthalocyanine lead (Pb Pc) catalyst powder was weighed and prepared into 1 mL slurry (200 μL of deionized water, 200 μL of ethanol, and 600 μL of 0.5 wt% Nafion solution). After ultrasonic mixing, it was drop-coated on a 1 cm 2 carbon paper as a working electrode.

[0046] The anode chamber was added with 8 mL of 1 M H2SO4 solution, and the cathode chamber was added with 8 mL of 1 M H2SO4 solution dissolved with 0.25 M oxalic acid and 0.25 M potassium nitrate mixed solution with equal volume. The prepared working electrode was placed in the cathode chamber, and a saturated potassium chloride standard electrode with a calomel electrode was inserted as a reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as a counter electrode (CE). Under the condition of 500 mA / cm 2 , electrolysis was performed for 1.5 h, and finally an electrolyte containing glycine was obtained.

[0047] Examples 1-3 were prepared by a similar method at 150 mA / cm2 350 mA / cm 2 and 500 mA / cm 2 The measurements were performed under current density conditions, keeping the same amount of charge transferred in the reaction.

[0048] The electrolyte containing glycine was obtained and coupled with gas chromatography to detect H2 during the reaction process, and a 400 MHz Bruker nuclear magnetic resonance spectrometer was used to detect the product content and calculate the Faraday efficiency.

[0049] The phthalocyanine lead was tested for electrochemical activity of the catalyst under different cathode solution environments using linear sweep voltammetry. See Figure 3 It can be seen that under the condition of an electrolyte containing only H2SO4, the polarization curve shows very weak current density; under the condition of an electrolyte containing oxalic acid and nitrate coexisting, the current density has the lowest starting potential, and its current density growth is also the fastest with the increase of potential. It is preliminarily indicated that the phthalocyanine lead in Example 1 can achieve high current density at ultra-low potential, and it is preliminarily judged that the adsorption of oxalic acid and nitrate can promote the co-reduction.

[0050] Comparative Example 1 2.0 mg of commercial elemental Pb catalyst powder was weighed and prepared into 1 mL slurry (200 μL of deionized water, 200 μL of ethanol, and 600 μL of 0.5 wt% Nafion solution), and after ultrasonic mixing, it was drop-casted on a 1 cm 2 carbon paper as a working electrode.

[0051] The liquid added to the cathode chamber was an 8 mL 1M H2SO4 solution containing 0.25 M oxalic acid and 0.25 M potassium nitrate mixed in equal volumes, and the liquid added to the anode chamber was an 8 mL 1 M H2SO4 solution. Electrochemical co-reduction test was performed using constant flow, and the prepared working electrode was placed in the cathode chamber, a calomel electrode (saturated potassium chloride) standard electrode was inserted as a reference electrode (RE), and a Pt sheet electrode was inserted into the anode chamber as a counter electrode (CE). Under the condition of 150 mA / cm 2 , electrolysis was carried out for 5 h, and the electrolyte containing glycine was finally obtained.

[0052] Comparative Example 2 2.0 mg of commercial elemental Pb catalyst powder was weighed and prepared into 1 mL slurry (200 μL of deionized water, 200 μL of ethanol, and 600 μL of 0.5 wt% Nafion solution), and after ultrasonic mixing, it was drop-casted on a 1 cm 2 carbon paper as a working electrode.

[0053] The cathode chamber was filled with 8 mL of a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H2SO4, and the anode chamber was filled with 8 mL of 1 M H2SO4 solution. Electrochemical co-reduction tests were conducted using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode containing a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted in the anode chamber as the counter electrode (CE). The flow rate was 350 mA / cm 2 Under the conditions of , electrolysis was carried out for 2.2 h to finally obtain an electrolyte containing glycine.

[0054] Comparative Example 3 2.0 mg of commercial elemental Pb catalyst powder was weighed and prepared into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, the mixture was drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0055] The cathode chamber was filled with 8 mL of a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H2SO4, and the anode chamber was filled with 8 mL of a 1 M H2SO4 solution. Electrochemical co-reduction tests were conducted using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode containing a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted in the anode chamber as the counter electrode (CE). The flow rate was 500 mA / cm 2 Under the conditions of , electrolysis was carried out for 1.5h to finally obtain an electrolyte containing glycine.

[0056] Comparative Example 4 2.0 mg of commercial PbO2 catalyst powder was weighed and prepared into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, the mixture was drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0057] The cathode chamber was filled with 8 mL of a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H2SO4, and the anode chamber was filled with 8 mL of a 1 M H2SO4 solution. Electrochemical co-reduction tests were conducted using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode containing a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted in the anode chamber as the counter electrode (CE). The flow rate was 150 mA / cm 2 Under the conditions of , electrolysis was carried out for 5 h to finally obtain an electrolyte containing glycine.

[0058] Comparative Example 5 2.0 mg of commercial PbO2 catalyst powder was weighed and prepared into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, the mixture was drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0059] The cathode chamber was filled with 8 mL of a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H2SO4, and the anode chamber was filled with 8 mL of 1 M H2SO4 solution. Electrochemical co-reduction tests were conducted using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode containing a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted in the anode chamber as the counter electrode (CE). The flow rate was 350 mA / cm 2 Under the conditions of , electrolysis was carried out for 2.2 h to finally obtain an electrolyte containing glycine.

[0060] Comparative Example 6 2.0 mg of commercial PbO2 catalyst powder was weighed and prepared into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, the mixture was drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0061] The cathode chamber was filled with 8 mL of a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 1 M H2SO4, and the anode chamber was filled with 8 mL of a 1 M H2SO4 solution. Electrochemical co-reduction tests were conducted using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode containing a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted in the anode chamber as the counter electrode (CE). The flow rate was 500 mA / cm 2 Under the conditions of , electrolysis was carried out for 1.5h to finally obtain an electrolyte containing glycine.

[0062] Comparative Example 7 Weigh 2.0 mg of molecular catalyst cobalt phthalocyanine (CoPc) catalyst powder and prepare it into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, drop-coat it on a 1 cm 2 Carbon paper was used as the working electrode.

[0063] The liquid added to the cathode chamber was a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 8 mL of 1M H2SO4. The electrochemical activity of the catalyst was tested using linear sweep voltammetry. The liquid added to the anode chamber was 8 mL of 1M H2SO4 solution. The electrochemical co-reduction test was performed using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode with a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as the counter electrode (CE). At 150 mA / cm 2 Under the conditions of , the electrolyte was electrolyzed for 5 h to obtain the final electrolyte. The H2 in the reaction process was detected by gas chromatography, and the product content was detected by 400 MHz Bruker nuclear magnetic resonance spectrometer to calculate the Faradaic efficiency.

[0064] Comparative Example 8 2.0 mg of molecular catalyst iron phthalocyanine (FePc) catalyst powder was weighed and prepared into 1 mL slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). After ultrasonic mixing, the mixture was drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0065] The liquid added to the cathode chamber was a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 8 mL of 1M H2SO4. The electrochemical activity of the catalyst was tested using linear sweep voltammetry. The liquid added to the anode chamber was 8 mL of 1M H2SO4 solution. The electrochemical co-reduction test was performed using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode with a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as the counter electrode (CE). At 150 mA / cm 2 Under the conditions of , the electrolyte was electrolyzed for 5 h to obtain the final electrolyte. The H2 in the reaction process was detected by gas chromatography, and the product content was detected by 400 MHz Bruker nuclear magnetic resonance spectrometer to calculate the Faradaic efficiency.

[0066] Comparative Example 9 Weigh 2.0 mg of molecular catalyst copper phthalocyanine (Cu Pc) catalyst powder and prepare 1 mL of slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution). Ultrasonic mixing was performed and then drop-coated on a 1 cm 2 Carbon paper was used as the working electrode.

[0067] The liquid added to the cathode chamber was a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 8 mL of 1M H2SO4. The electrochemical activity of the catalyst was tested using linear sweep voltammetry. The liquid added to the anode chamber was 8 mL of 1M H2SO4 solution. The electrochemical co-reduction test was performed using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode with a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as the counter electrode (CE). At 150 mA / cm 2 Under the conditions of , the electrolyte was electrolyzed for 5 h to obtain the final electrolyte. The H2 in the reaction process was detected by gas chromatography, and the product content was detected by 400 MHz Bruker nuclear magnetic resonance spectrometer to calculate the Faradaic efficiency.

[0068] Comparative Example 10 Weigh 2.0 mg of molecular catalyst tin phthalocyanine (SnPc) catalyst powder and prepare 1 mL of slurry (200 μL deionized water, 200 μL ethanol and 600 μL 0.5 wt% Nafion solution) respectively. After ultrasonic mixing, drop-coat the mixture on a 1 cm 2 Carbon paper was used as the working electrode.

[0069] The liquid added to the cathode chamber was a mixed solution of 0.25 M oxalic acid and 0.25 M potassium nitrate dissolved in 8 mL of 1M H2SO4. The electrochemical activity of the catalyst was tested using linear sweep voltammetry. The liquid added to the anode chamber was 8 mL of 1M H2SO4 solution. The electrochemical co-reduction test was performed using a constant flow. The prepared working electrode was placed in the cathode chamber, and a standard electrode with a calomel electrode (saturated potassium chloride) was inserted as the reference electrode (RE). A Pt sheet electrode was inserted into the anode chamber as the counter electrode (CE). At 150 mA / cm 2 Under the conditions of , the electrolyte was electrolyzed for 5 h to obtain the final electrolyte. The H2 in the reaction process was detected by gas chromatography, and the product content was detected by 400 MHz Bruker nuclear magnetic resonance spectrometer to calculate the Faradaic efficiency.

[0070] See also Figure 4 Comparative Examples 1 to 6 were tested for electrochemical activity using chronopotentiometry in the presence of oxalic acid and nitrate. It can be seen that compared to the catalysts in Comparative Examples 1 to 6, the catalyst in Example 1 exhibited superior intrinsic activity in the reaction of co-reduction of CN coupling to synthesize glycine. 150 mA / cm 2 The Faradaic efficiency at the current density reached 65%, 350mA / cm 2 Faradaic efficiency exceeds 55%, 500mA / cm 2The Faraday efficiency is also maintained above 50%. Compared with Comparative Examples 1 to 6, the Faraday efficiency is more than twice as high as that of the same metal Pb-based catalyst.

[0071] See also Figure 5 and Figure 6 It can be seen that under the coexistence of oxalic acid and nitrate, the electric density of the embodiment at the same voltage is significantly higher than that of comparative examples 7 to 10, indicating that under the same conditions, the embodiment has higher activity. Figure 5 It is further shown that the embodiment can more efficiently promote the co-reduction electrosynthesis of glycine by oxalic acid and nitrate.

[0072] See also Figure 7 It can be seen that the lead phthalocyanine catalyst of Example 1 has a high 2 Under the current density conditions, the activity did not decrease, showing good stability.

[0073] refer to Figure 8 , at 25 cm 2 In the MEA electrolytic cell, the total current is 1000 mA / cm 2 The single-pass electrosynthesis of glycine can be achieved.

[0074] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0075] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for synthesizing glycine by electrocatalyzing the coupling of oxalic acid with nitrate using a molecular catalyst, lead phthalocyanine, characterized in that: The following steps are involved: The lead phthalocyanine, the dispersant and the binder are mixed uniformly to prepare a catalyst slurry; loading the catalyst slurry on carbon paper to obtain catalyst-containing carbon paper; Assembling an H-type electrolytic cell, wherein the electrolyte in the anode chamber is a sulfuric acid solution, the electrolyte in the cathode chamber is a sulfuric acid solution containing oxalic acid and potassium nitrate, and the cathode chamber and the anode chamber are separated by an ion exchange membrane; A calomel electrode is inserted into the cathode chamber as a reference electrode and carbon paper containing a catalyst is used as a working electrode. A platinum sheet is inserted into the anode chamber as a counter electrode for electrolysis. During the electrolysis process, a CN coupling co-reduction reaction is carried out to obtain glycine.

2. The method for synthesizing glycine by electrocatalyzing oxalic acid-nitrate coupling using a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: On the carbon paper containing catalyst, the amount of lead phthalocyanine added is 1.5 mg / cm 2 ~2mg / cm 2 .

3. The method for synthesizing glycine by electrocatalyzing oxalic acid-nitrate coupling using a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: In the sulfuric acid solution containing oxalic acid and potassium nitrate, the molar ratio of oxalic acid to potassium nitrate is 1:1~1.

2.

4. The method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by coupling a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: The current density during electrolysis is 150~500mA / cm 2 .

5. The method for synthesizing glycine by electrocatalyzing oxalic acid-nitrate coupling using a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: The electrolysis time is 4h~5h.

6. The method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by using a molecular catalyst lead phthalocyanine as claimed in claim 1, characterized in that: The dispersants are water and ethanol, and the binder is Nafion solution.

7. The method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by coupling with nitrate using a molecular catalyst lead phthalocyanine according to claim 6, characterized in that: The volume ratio of Nafion solution, ethanol and water is 3:1:

1.

8. The method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by coupling with a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: The ion exchange membrane is Nafion 117 ion exchange membrane.

9. The method for synthesizing glycine by electrocatalyzing oxalic acid and nitrate by coupling with a molecular catalyst lead phthalocyanine according to claim 1, characterized in that: The concentration of sulfuric acid solution is 1mol / L~1.5mol / L.

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