A method for the preparation of 1,2-propanediol by homogeneous silver electrocatalytic oxidation of propylene

Abstract

The application provides a method for preparing 1,2-propanediol by homogenous silver electrocatalytic oxidation of propylene, which comprises the following steps: using an anode catalyst as an anode and a cathode catalyst as a cathode, adding a silver salt into an electrolyte aqueous solution, assembling into an electrolytic cell, and introducing propylene gas into the electrolytic cell under a voltage condition; wherein the silver salt is a silver salt capable of providing silver ions in the electrolyte aqueous solution. The method uses a homogenous catalyst, does not need to prepare a supported catalyst, simplifies process steps, and has a large current density for preparing 1,2-propanediol, a high Faraday efficiency, a high energy utilization efficiency, and a high production rate. Meanwhile, the method has mild conditions, is green and environmentally friendly, has a low cost, and is suitable for industrialized production.

Description

Technical Field

[0001] This invention relates to the field of electrocatalytic organic synthesis technology, specifically to a method for preparing 1,2-propanediol by homogeneous silver electrocatalytic oxidation of propylene. Background Technology

[0002] The catalytic oxidation of olefins is a fundamental and crucial reaction in organic chemistry, and the resulting oxygen-containing derivatives are widely used in numerous industrial sectors. Among these, the downstream oxidation products of low-carbon olefins such as ethylene and propylene, serving as the cornerstone of modern chemical industry, are largely basic raw materials for organic chemical synthesis. For instance, propylene oxide is one of the most important raw materials in the plastics industry, used to produce bulk chemicals such as polyurethane and polyester fibers; 1,2-propanediol has various applications in pharmaceuticals, cosmetics, and food manufacturing. Therefore, the output and capacity of downstream olefin oxidation products have maintained a consistently high level in recent years and continue to show a steady growth trend. According to relevant statistics, in 2023, the global annual production of 1,2-propanediol reached 2.7 million tons, with a global market value exceeding US$4 billion, and its market price maintained an annual growth rate of 4.4% (ACS. Sustainable. Chem. Eng. 2023, 11, 2773.).

[0003] In the industrial chain of olefin oxidation, thermocatalytic conversion is currently the dominant mode. The process for producing propylene oxide from propylene mainly uses the traditional chlorohydrin process and co-oxidation process. 1,2-Propanediol is primarily obtained by the hydrolysis of propylene oxide, a hydrolysis reaction that requires high temperature or strong acidity, making the reaction conditions quite harsh. Furthermore, the chlorohydrin process involves propylene chlorohydrinization, lime milk saponification, and product refining, consuming large amounts of water and chlorine, causing severe equipment corrosion, and generating large quantities of wastewater and waste residue, leading to serious environmental and safety problems. The co-oxidation process requires the production of peroxides as olefin oxidants, facing challenges such as high temperature and pressure, complex processes, high costs, safety hazards, and high carbon emissions. Statistical calculations show that in industrial production, the production of 1 ton of 1,2-propanediol requires the emission of approximately 4.7 tons of CO2, of which about 3 tons come from the propylene-to-1,2-propanediol conversion process, and the remainder from the production of propylene feedstock.

[0004] In recent years, relevant literature has reported methods for the direct electrocatalytic oxidation of propylene to prepare propylene oxide and 1,2-propanediol using transition metal catalysts, for example:

[0005] CN112962113A discloses the application of silver phosphate single-crystal catalysts with different crystal planes in the electrocatalytic epoxidation of propylene and a method for producing propylene oxide (Nat. Commun. 2022, 13, 932). Although this catalyst exhibits high selectivity and activity, the current density and Faradaic efficiency are both low in the electrocatalytic oxidation of propylene to propylene oxide. Furthermore, this method requires catalyst preparation, and to further obtain 1,2-propanediol, propylene oxide must be hydrolyzed, making the process cumbersome and costly.

[0006] CN116356360A discloses a supported silver-based catalyst and its application in the preparation of 1,2-propanediol (J. Am. Chem. Soc. 2023, 145, 16, 9104). This catalyst is obtained by forming a complex with a silver salt and a pyrazole compound, and then supporting this complex on a support. It is used to catalyze the direct oxidation of propylene to 1,2-propanediol, exhibiting high selectivity and good stability. However, its electrocatalytic faradaic efficiency remains low, reaching a maximum of less than 20%, and the current density is also low. Increasing the current density leads to a decrease in faradaic efficiency, significantly reducing energy utilization efficiency. Furthermore, this method requires catalyst preparation, making the process cumbersome.

[0007] CN116254565A discloses a silver single-atom catalyst and its application in the preparation of 1,2-propanediol. Although this catalyst has a high Faradaic efficiency in the electrocatalytic oxidation of propylene to 1,2-propanediol, its preparation process is quite cumbersome. It requires the use of special reagents (such as zirconium chloride, 2,2'-bipyridine-5,5'-dicarboxylic acid, etc.) to first prepare a metal-organic framework, then mix it with a dispersant (such as tetrahydrofuran or other organic solvents), and finally mix it with a silver salt solution. This not only increases the process cost but is also environmentally unfriendly, making it unsuitable for industrial production.

[0008] In summary, existing methods for the electrocatalytic oxidation of propylene to 1,2-propanediol suffer from numerous problems, such as low current density and low Faradaic efficiency, leading to reduced energy utilization efficiency. Furthermore, all existing catalysts for the electrocatalytic oxidation of propylene to 1,2-propanediol are supported catalysts, which are heterogeneous catalysts, and no reports have been made regarding homogeneous catalysts. Summary of the Invention

[0009] The problem the invention aims to solve

[0010] To address the aforementioned problems, this invention aims to provide a homogeneous silver-catalyzed method for the oxidation of propylene to prepare 1,2-propanediol, thereby improving the reaction rate and energy efficiency of 1,2-propanediol. This method uses a homogeneous silver catalyst, eliminating the need for catalyst preparation. The reaction process is simple and mild, with low cost, is environmentally friendly, and suitable for industrial production.

[0011] Solution for solving the problem

[0012] According to the inventor's research, the above-mentioned technical problems can be solved by the following solution:

[0013] [1] A method for preparing 1,2-propanediol by homogeneous silver electrocatalytic oxidation of propylene includes the following steps: using an anode catalyst as the anode and a cathode catalyst as the cathode, adding silver salt to an electrolyte aqueous solution to assemble an electrolytic cell, and introducing propylene gas into the electrolytic cell under voltage conditions; wherein the silver salt is a silver salt that can provide silver ions in the electrolyte aqueous solution.

[0014] [2] According to the method described in [1] above, the concentration of silver ions in the electrolyte aqueous solution is 12.5 μmol / L or more, preferably 12.5 μmol / L to 2500 μmol / L, more preferably 100 μmol / L to 1125 μmol / L, and most preferably 100 μmol / L to 550 μmol / L.

[0015] [3] According to the method described in [1] or [2] above, wherein the silver salt is one or more of silver nitrate, silver sulfate, silver acetate, silver acetylacetone, silver trifluoroacetate, silver tungstate, silver lactate, silver phosphate, silver fluoride, silver chlorate and silver perchlorate, preferably one or more of silver nitrate, silver sulfate and silver acetate, more preferably silver nitrate.

[0016] [4] According to any one of [1]-[3] above, the electrolytic cell further has a reference electrode, which is Ag / AgCl or Hg / Hg2Cl2, preferably Ag / AgCl.

[0017] [5] The method according to any one of [1]-[4] above, wherein the voltage is 1V to 4V vs Ag / AgCl, preferably 1.4V to 2.0V vs Ag / AgCl, more preferably 1.6V to 2.0V vs Ag / AgCl.

[0018] [6] The method according to any one of [1]-[5] above, wherein the anode catalyst is one or more 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 and FTO conductive glass, preferably carbon cloth or carbon paper.

[0019] [7] The method according to any one of [1]-[6] above, wherein the cathode catalyst is one or more of platinum, gold, silver, ruthenium, iridium, palladium, copper and rhodium, preferably platinum.

[0020] [8] The method according to any one of [1]-[7] above, wherein the electrolyte aqueous solution is an aqueous solution of one or more of sodium sulfate, potassium sulfate, lithium sulfate, zinc sulfate, magnesium sulfate, sodium nitrate, potassium nitrate, lithium nitrate, zinc nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, sulfuric acid, nitric acid, perchloric acid, sodium perchlorate, potassium perchlorate and lithium perchlorate; preferably, the concentration of the electrolyte aqueous solution is 1 mg / mL to 1000 mg / mL, more preferably 3 mg / mL to 20 mg / mL.

[0021] [9] The method according to any one of [1]-[8] above, wherein the flow rate of the propylene gas is 1 s.ccm to 500 s.ccm, preferably 10 s.ccm to 30 s.ccm.

[0022] The effects of the invention

[0023] The technical effects of this invention are as follows:

[0024] (1) This invention is the first to use a homogeneous silver catalyst to electrocatalyze the preparation of 1,2-propanediol from propylene, breaking the conventional idea that a supported heterogeneous catalyst needs to be prepared, greatly simplifying the process steps and saving process costs. The preparation method of this invention is more suitable for the industrial production of 1,2-propanediol.

[0025] (2) Compared with carbon-supported silver nanoparticle heterogeneous catalysts, the present invention uses simple silver ion catalysis to oxidize propylene to prepare 1,2-propanediol with a larger current density, a higher Faraday efficiency (up to 28%), higher energy utilization efficiency, and higher reaction rate and reaction selectivity.

[0026] (3) The preparation method of the present invention is mild and can be carried out at room temperature and normal pressure. It does not require special reagents or special conditions, nor does it require the use of organic solvents, making it green and environmentally friendly.

[0027] (4) The preparation method of the present invention can reduce the emission of waste gases such as carbon dioxide and generate hydrogen gas by coupling at the cathode, which is both green and environmentally friendly and improves economic benefits. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the mechanism for the homogeneous Ag ion electrocatalytic oxidation of propylene to prepare 1,2-propanediol according to the present invention.

[0029] Figure 2The results are from a liquid chromatography test conducted in Example 1 of this invention, where 1.8 mg of silver nitrate was reacted at a constant voltage of 1.8 V for 2 hours.

[0030] Figure 3 This is the current-time curve of the electrocatalytic oxidation of propylene to 1,2-propanediol under standard reaction conditions in Example 1 of the present invention;

[0031] Figure 4 This is the effect of the amount of homogeneous AgNO3 on the reaction performance of the electrocatalytic oxidation of propylene to 1,2-propanediol in Example 2 of the present invention; wherein, the value of the bar graph represents the Faraday efficiency, and the value of the line graph represents the partial current density;

[0032] Figure 5 This is the effect of reaction oxidation potential on the reaction performance of electrocatalytic propylene oxidation to 1,2-propanediol in Example 3 of the present invention; wherein, the value of the bar graph represents the Faraday efficiency, and the value of the line graph represents the partial current density;

[0033] Figure 6 This is a linear scanning voltammetric spectrum of homogeneous Ag ions before and after the introduction of propylene in Example 4 of the present invention;

[0034] Figure 7 The results are from a liquid chromatography test conducted in Example 5 of this invention, where 3.6 mg of silver nitrate was reacted at a constant voltage of 1.8 V for 2 hours.

[0035] Figure 8 The results are from a liquid chromatography test conducted in Example 6 of this invention, where 7.2 mg of silver nitrate was reacted at a constant voltage of 1.8 V for 2 hours.

[0036] Figure 9 The results are from a liquid chromatography test conducted in Example 7 of this invention, where 3.2 mg of silver sulfate was reacted at a constant voltage of 1.8 V for 2 hours.

[0037] Figure 10 The results are from the liquid chromatography test of 1.7 mg silver acetate reacted at a constant voltage of 1.8 V for 2 hours in Example 8 of the present invention.

[0038] Figure 11 This is a transmission electron microscope image of the carbon-supported silver nanoparticle heterogeneous catalyst obtained in Comparative Example 1 of the present invention.

[0039] Figure 12 The results are obtained by liquid chromatography of the carbon-supported silver nanoparticle heterogeneous catalyst used in Comparative Example 1 of the present invention, reacted at a constant voltage of 1.8V for 2 hours. Detailed Implementation

[0040] Various exemplary embodiments, features, and aspects of the present invention will be described in detail below. The term "exemplary" as used herein means "serving as an example, embodiment, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as superior to or better than other embodiments.

[0041] Furthermore, to better illustrate the present invention, numerous specific details are set forth in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In other instances, methods, means, apparatus, and steps well known to those skilled in the art have not been described in detail in order to highlight the spirit of the present invention.

[0042] Unless otherwise stated, all units used in this specification are international standard units, and all numerical values ​​and ranges appearing in this invention should be understood to include systematic errors that are unavoidable in industrial production.

[0043] In this specification, the word "may" has two meanings: to perform a certain process and not to perform a certain process.

[0044] In this specification, references to "some specific / preferred embodiments," "other specific / preferred embodiments," "implementation," etc., refer to specific elements (e.g., features, structures, properties, and / or characteristics) related to that embodiment, which are included in at least one of the embodiments described herein and may or may not be present in other embodiments. Furthermore, it should be understood that these elements may be combined in any suitable manner in various embodiments.

[0045] In this specification, the range of values ​​referred to as "value A to value B" refers to the range including the endpoint values ​​A and B.

[0046] In this specification, the numerical range referred to as "value A and above" refers to the range including the endpoint value A.

[0047] In this instruction manual, when "room temperature" or "room temperature" is used, the temperature can be 15℃ to 30℃, or more specifically 15℃ to 25℃, such as 20℃.

[0048] In existing reports, the catalysts for the electrocatalytic preparation of 1,2-propanediol from propylene are all supported catalysts, which are heterogeneous catalysts. These require preparation, and the preparation steps are cumbersome, sometimes requiring special reagents, resulting in high costs and hindering industrial production. This invention breaks with this conventional approach, proposing for the first time a method for the electrocatalytic preparation of 1,2-propanediol from propylene using a homogeneous catalyst. It uses a simple silver salt as a silver ion precursor, adding the silver salt to the electrolyte solution as a homogeneous catalyst, achieving a highly selective and efficient electrocatalytic preparation process for the conversion of propylene substrate to 1,2-propanediol product.

[0049] The reaction mechanism of homogeneous silver electrocatalytic oxidation of propylene to 1,2-propanediol in this invention is described in [reference needed]. Figure 1 At the anode of the electrolytic cell, silver ions react with water to form a silver-oxygen species intermediate. When the silver-oxygen species intermediate comes into contact with propylene, it oxidizes propylene to 1,2-propanediol and releases silver ions, thus realizing the catalytic cycle of silver ions.

[0050] Homogeneous silver catalyst

[0051] In this invention, the type of homogeneous silver catalyst is not particularly limited. Even when the concentration of silver ions in the electrolyte aqueous solution is low, it can still electrocatalyze the oxidation of propylene to prepare 1,2-propanediol. Therefore, any silver salt that can provide silver ions in the electrolyte aqueous solution can be used as the homogeneous silver catalyst of this invention, such as one or more of silver nitrate, silver sulfate, silver acetate, silver acetylacetone, silver trifluoroacetate, silver tungstate, silver lactate, silver phosphate, silver fluoride, silver chlorate, and silver perchlorate.

[0052] In some embodiments, the silver salt may be one or more of silver nitrate, silver sulfate, and silver acetate.

[0053] In some preferred embodiments, the silver salt may be a water-soluble silver salt. In this invention, "water-soluble silver salt" refers to a silver salt that can dissolve in water.

[0054] In some preferred embodiments, the silver salt may be silver nitrate.

[0055] Homogeneous silver electrocatalytic oxidation of propylene to prepare 1,2-propanediol

[0056] Specifically, the method for preparing 1,2-propanediol by homogeneous silver electrocatalytic propylene oxidation provided by the present invention includes the following steps: using an anode catalyst as the anode and a cathode catalyst as the cathode, adding silver salt to an electrolyte aqueous solution to assemble an electrolytic cell, and introducing propylene gas into the electrolytic cell under voltage conditions; wherein, the silver salt is a silver salt that can provide silver ions in the electrolyte aqueous solution.

[0057] In some embodiments, the concentration of silver ions in the electrolyte aqueous solution can be 12.5 μmol / L or higher; in some preferred embodiments, the concentration of silver ions in the electrolyte aqueous solution can be 12.5 μmol / L to 2500 μmol / L, more preferably 100 μmol / L to 1125 μmol / L, and most preferably 100 μmol / L to 550 μmol / L, for example, 125 μmol / L, 150 μmol / L, 200 μmol / L, 250 μmol / L, 260 μmol / L, 300 μmol / L, 400 μmol / L, 500 μmol / L, 530 μmol / L, 750 μmol / L, 1000 μmol / L, 1500 μmol / L, 2000 μmol / L, etc.

[0058] In some embodiments, the partial current density of 1,2-propanediol in this invention can be 2 mA cm⁻¹. -2 The above (e.g., 4.5mA cm) -2 7mA cm -2 9mA cm -2 10mA cm -2 Faraday efficiency can be above 20% (e.g., 20%, 22%, 25%, 28%, 30%, 35%, etc.).

[0059] In some implementations, a reference electrode is also present in the electrolytic cell.

[0060] In some specific embodiments, the reference electrode of the present invention can be Ag / AgCl or Hg / Hg2Cl2, preferably Ag / AgCl.

[0061] In some embodiments, the voltage of the present invention can be 1V to 4V vs Ag / AgCl, preferably 1.4V to 2.0V vs Ag / AgCl, more preferably 1.6V to 2.0V vs Ag / AgCl, for example, 1.5V vs Ag / AgCl, 1.6V vs Ag / AgCl, 1.7V vs Ag / AgCl, 1.8V vs Ag / AgCl, 2.0V vs Ag / AgCl, etc.

[0062] In some embodiments, the anode catalyst may be one or more 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, and FTO conductive glass; as some preferred embodiments of the present invention, the anode catalyst may be carbon cloth or carbon paper.

[0063] In some embodiments, the cathode catalyst may be one or more of platinum, gold, silver, ruthenium, iridium, palladium, copper, and rhodium; as some preferred embodiments of the present invention, the cathode catalyst may be platinum.

[0064] In some embodiments, the electrolyte aqueous solution may be an aqueous solution of one or more of sodium sulfate, potassium sulfate, lithium sulfate, zinc sulfate, magnesium sulfate, sodium nitrate, potassium nitrate, lithium nitrate, zinc nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, sulfuric acid, nitric acid, perchloric acid, sodium perchlorate, potassium perchlorate, and lithium perchlorate; as some preferred embodiments of the present invention, the electrolyte aqueous solution may be an aqueous solution of one or more of sodium perchlorate, potassium perchlorate, and lithium perchlorate.

[0065] In some embodiments, the concentration of the electrolyte aqueous solution can be from 1 mg / mL to 1000 mg / mL, preferably from 3 mg / mL to 20 mg / mL, for example, it can be 2 mg / mL, 6 mg / mL, 10 mg / mL, 12 mg / mL, 14 mg / mL, 16 mg / mL, 20 mg / mL, 50 mg / mL, 100 mg / mL, 200 mg / mL, 500 mg / mL, 800 mg / mL, etc.

[0066] In some embodiments, the flow rate of the propylene gas can be from 1 s.ccm to 500 s.ccm, preferably from 10 s.ccm to 30 s.ccm, for example, it can be 15 s.ccm, 20 s.ccm, 25 s.ccm, 50 s.ccm, 100 s.ccm, 200 s.ccm, 300 s.ccm, 400 s.ccm, etc.

[0067] In this invention, a reaction can occur by introducing propylene gas into an electrolyte aqueous solution. Propylene gas is continuously introduced during the reaction process. Therefore, the gas introduction time in this invention is also the reaction time.

[0068] In some embodiments, the reaction time of the present invention can be 0.5h to 48h, preferably 0.5h to 24h, for example, 1h, 2h, 3h, 4h, 6h, 8h, 10h, 16h, 20h, 30h, 40h, etc.

[0069] In some embodiments, the reaction rate of the 1,2-propanediol of the present invention can be 100.0 μmol h⁻¹. -1 cm -2 The above, for example, can be 125 μmol h -1 cm -2 150 μmol h -1 cm-2 175 μmol h -1 cm -2 200 μmol h -1 cm -2 wait.

[0070] In some embodiments, the selectivity of the 1,2-propanediol of the present invention can be 80% or more, for example, 81%, 85%, 90%, 95%, etc.

[0071] In this invention, introducing propylene gas means blowing propylene gas into the electrolyte aqueous solution; in some embodiments, introducing propylene gas means blowing propylene gas into the electrolyte aqueous solution at the anode.

[0072] In this invention, the homogeneous silver electrocatalytic oxidation of propylene to prepare 1,2-propanediol is carried out under mild reaction conditions, and the reaction can be carried out at room temperature and normal pressure. If the solubility of certain silver salts in the electrolyte aqueous solution is low at room temperature, the temperature of the electrolyte aqueous solution can be appropriately increased to increase the solubility of the silver salts, thereby increasing the concentration of silver ions in the electrolyte aqueous solution.

[0073] In this invention, "PG" refers to 1,2-propanediol, and "propanediol" also refers to 1,2-propanediol.

[0074] Quantitative identification and detection of products

[0075] In this invention, the quantitative identification of the product 1,2-propanediol can be achieved by liquid chromatography. In some embodiments, the detection conditions for liquid chromatography can be as follows: the detector is a differential refractive index detector (RID), the mobile phase is a 5 mM sulfuric acid aqueous solution, and the flow rate is 0.6 mL / min. In some specific embodiments of this invention, the retention time of 1,2-propanediol in the liquid chromatogram is 16.4 min (which can fluctuate within a reasonable range, such as 16.4 ± 0.2 min or 16.4 ± 0.1 min).

[0076] Carbon-supported silver nanoparticle heterogeneous catalyst

[0077] In this invention, a carbon-supported silver nanoparticle heterogeneous catalyst is used as a comparative catalyst. The preparation steps are as follows: a solution of soluble silver salt, carbon support, and reducing agent is stirred and mixed evenly and then loaded into a hydrothermal reactor for reaction. After the reaction is completed, the mixture is centrifuged and vacuum dried to obtain a carbon-supported silver-based catalyst.

[0078] In some embodiments, the silver salt may include one or more of silver nitrate, silver sulfate, silver acetate, silver acetylacetone, silver trifluoroacetate, silver tungstate, and silver lactate.

[0079] In some embodiments, the carbon support may include one or more of carbon black, Ketjen black, and acetylene black.

[0080] In some embodiments, the reducing agent may be sodium borohydride.

[0081] In some embodiments, the reaction temperature can be 80°C to 300°C, for example 200°C.

[0082] In some embodiments, the reaction time can be 0.5h to 5h, for example 3h.

[0083] Example

[0084] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0085] The detection conditions for liquid chromatography in the examples are as follows: the detector is a differential refractive index detector (RID), the mobile phase is 5 mM sulfuric acid aqueous solution, and the flow rate is 0.6 mL / min.

[0086] Example 1

[0087] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. 1.8 mg silver nitrate (10.6 μmol) was added to the electrolyte as a silver salt (silver ion concentration 265 μmol / L) as a homogeneous catalyst. A three-electrode system was constructed, using carbon paper as the anode, a platinum sheet as the cathode, and an Ag / AgCl electrode as the reference electrode. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken, and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 2 In the study, the peak area of ​​1,2-propanediol was 97020.1, the yield was 335 μmol, the Faradaic efficiency was 28.8%, and the PG partial current density was 9.0 mA cm⁻¹. -2 The reaction rate is 167.5 μmol / h. -1 cm -2 It was determined that the reaction produces 1,2-propanediol, along with acetone and acetic acid as byproducts. In the above reaction, the reaction rate of acetone is 8.8 μmol / h. -1 cm -2 The reaction rate of acetic acid is 28.4 μmol / h.-1 cm -2 The selectivity for 1,2-propanediol was 81.8%.

[0088] In addition, the current-time curves for the electrocatalytic oxidation of propylene to 1,2-propanediol were measured, and the results are as follows: Figure 3 As shown, this indicates that the current continuously increases as the reaction proceeds.

[0089] Example 2

[0090] Under the same experimental conditions as in Example 1, only the amount of silver nitrate was varied to 0.1 μmol, 0.5 μmol, 1.0 μmol, 5 μmol, 10 μmol, and 100 μmol. The effect of the amount of silver nitrate on the reaction performance of the electrocatalytic oxidation of propylene to 1,2-propanediol was determined. The results are shown in [link to example]. Figure 4 .from Figure 4 It can be seen that when the amount of silver nitrate is above 0.5 μmol, that is, when the concentration of silver ions is above 12.5 μmol / L, it exhibits a higher current density and Faraday efficiency.

[0091] Example 3

[0092] Under the same experimental conditions as in Example 1, only the reaction voltage was changed to 1.4V, 1.5V, 1.6V, 1.8V, and 2.0V vs. Ag / AgCl. The effect of reaction potential on the electrocatalytic oxidation of propylene to 1,2-propanediol was determined, and the results are shown in [reference needed]. Figure 5 .from Figure 5 It can be seen that it exhibits high Faraday efficiency in the range of 1.4V-2.0V, and also exhibits high current density in the range of 1.6V-2.0V.

[0093] Example 4

[0094] Under the same experimental conditions as in Example 1, linear sweep voltammetry spectra of silver ions before and after the introduction of propylene were measured at different voltages. The results are as follows: Figure 6 As shown. From Figure 6 As can be seen, the current density increases after propylene is introduced, indicating that the silver ions in the electrolyte catalyze the oxidation reaction of propylene.

[0095] Example 5

[0096] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. 3.6 mg silver nitrate (21.2 μmol) was added to the electrolyte as a silver salt (silver ion concentration 530 μmol / L) as a homogeneous catalyst. A three-electrode system was constructed, using carbon paper as the anode, a platinum sheet as the cathode, and an Ag / AgCl electrode as the reference electrode. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken, and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 7 In the study, the peak area of ​​1,2-propanediol was 101516, the yield was 353.6 μmol, the Faradaic efficiency of 1,2-propanediol was 25.7%, and the PG partial current density was 9.5 mA cm⁻¹. -2 The reaction rate is 176.8 μmol / h. -1 cm -2 .

[0097] Example 6

[0098] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. 7.2 mg silver nitrate (42.4 μmol) was added to the electrolyte as a silver salt (silver ion concentration 1060 μmol / L) as a homogeneous catalyst. A three-electrode system was constructed, using carbon paper as the anode, a platinum sheet as the cathode, and an Ag / AgCl electrode as the reference electrode. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 8 In the study, the peak area of ​​1,2-propanediol was 108092, the yield was 379.6 μmol, the Faradaic efficiency of 1,2-propanediol was 21.3%, and the PG partial current density was 10.2 mA cm⁻¹. -2 The reaction rate is 189.8 μmol / h. -1 cm -2 .

[0099] Example 7

[0100] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. 3.2 mg silver sulfate (10.3 μmol) was added to the electrolyte as a silver salt (silver ion concentration 257.5 μmol / L) as a homogeneous catalyst. A three-electrode system was constructed, using carbon paper as the anode, a platinum sheet as the cathode, and an Ag / AgCl electrode as the reference electrode. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken, and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 9 In the study, the peak area of ​​1,2-propanediol was 58484.3 μmol, the yield was 204.8 μmol, the Faradaic efficiency was 24.6%, and the PG partial current density was 5.5 mA / cm². -2 The reaction rate is 102.4 μmol / h. -1 cm -2 .

[0101] Example 8

[0102] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. 1.7 mg silver acetate (10.2 μmol) was added to the electrolyte as a silver salt (silver ion concentration 255 μmol / L) as a homogeneous catalyst. A three-electrode system was constructed, using carbon paper as the anode, a platinum sheet as the cathode, and an Ag / AgCl electrode as the reference electrode. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 10 In the study, the peak area of ​​1,2-propanediol was 64550.8 μmol, the yield was 223.4 μmol, the Faraday efficiency was 32.0%, and the PG partial current density was 6.0 mA / cm². -2 The reaction rate is 111.7 μmol / h. -1 cm -2 .

[0103] Compare with Example 1

[0104] A 20 mL aqueous solution containing 0.12 g silver nitrate as a silver precursor, 0.3 mg activated carbon as a carbon support, and 0.2 mg sodium borohydride as a reducing agent was prepared and stirred at room temperature for 1 h. After thorough mixing, the solution was poured into a hydrothermal reactor and reacted at 200 °C for 3 h. After the reaction, the supernatant was removed by centrifugation, and the solution was washed repeatedly with ethanol and deionized water, centrifuged, and dried. The resulting catalyst was dried overnight in a vacuum drying oven. The obtained carbon-supported silver nanoparticle electrocatalyst was dispersed in ethanol and sprayed onto a carbon paper substrate. The transmission electron microscopy (TEM) image of the carbon-supported silver nanoparticle electrocatalyst is shown in [Figure number missing]. Figure 11 The results indicate that the carbon-supported silver nanoparticle electrocatalyst has been successfully prepared.

[0105] A 40 mL aqueous solution containing 0.56 g sodium perchlorate was prepared as the electrolyte. A platinum sheet was used as the anode, an Ag / AgCl electrode as the reference electrode, and a three-electrode system was constructed. Propylene gas was introduced into the electrolyte at a flow rate of 20 s·ccm, and the reaction was continuously stirred for 2 hours at a constant voltage of 1.8 V relative to the Ag / AgCl electrode. Samples were taken, and 1,2-propanediol was quantitatively identified using liquid chromatography. The results were obtained on [date missing]. Figure 12 In the assay, the peak area of ​​1,2-propanediol was 12501.1, the yield was 44.6 μmol, the Radie efficiency of the 1,2-propanediol method was 19.7%, and the PG partial current density was 1.2 mA cm⁻¹. -2 The reaction rate is 22.3 μmol / h. -1 cm -2 .

[0106] It should be noted that although the technical solution of the present invention has been described with specific examples, those skilled in the art will understand that the present invention should not be limited thereto.

[0107] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing 1,2-propanediol by homogeneous silver electrocatalytic oxidation of propylene, comprising the following steps: An electrolytic cell is assembled by adding silver salt to an aqueous electrolyte solution using an anode catalyst as the anode and a cathode catalyst as the cathode. Propylene gas is then introduced into the electrolytic cell under voltage conditions. The silver salt is a silver salt capable of providing silver ions in the aqueous electrolyte solution, and the concentration of silver ions in the aqueous electrolyte solution is above 12.5 μmol / L. The anode catalyst is one or more 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, and FTO conductive glass. The cathode catalyst is one or more of platinum, gold, silver, ruthenium, iridium, palladium, copper, and rhodium. The aqueous electrolyte solution is an aqueous solution of one or more of sodium nitrate, potassium nitrate, lithium nitrate, zinc nitrate, calcium nitrate, magnesium nitrate, aluminum nitrate, nitric acid, perchloric acid, sodium perchlorate, potassium perchlorate, and lithium perchlorate.

2. The method according to claim 1, characterized in that, The concentration of silver ions in the electrolyte aqueous solution is 12.5 μmol / L to 2500 μmol / L.

3. The method according to claim 2, characterized in that, The concentration of silver ions in the electrolyte aqueous solution is 100 μmol / L to 1125 μmol / L.

4. The method according to claim 3, characterized in that, The concentration of silver ions in the electrolyte aqueous solution is 100 μmol / L to 550 μmol / L.

5. The method according to claim 1, characterized in that, The silver salt is one or more of silver nitrate, silver sulfate, silver acetate, silver acetylacetone, silver trifluoroacetate, silver lactate, silver fluoride, silver chlorate, and silver perchlorate.

6. The method according to claim 5, characterized in that, The silver salt is one or more of silver nitrate, silver sulfate, and silver acetate.

7. The method according to claim 6, characterized in that, The silver salt is silver nitrate.

8. The method according to any one of claims 1-7, characterized in that, The electrolytic cell also has a reference electrode, which is Ag / AgCl or Hg / Hg2Cl2.

9. The method according to claim 8, characterized in that, The reference electrode is Ag / AgCl.

10. The method according to any one of claims 1-7, characterized in that, The voltage is 1 V to 4 V vs Ag / AgCl.

11. The method according to claim 10, characterized in that, The voltage is 1.4 V~2.0 V vs Ag / AgCl.

12. The method according to claim 11, characterized in that, The voltage is 1.6 V~2.0 V vs Ag / AgCl.

13. The method according to any one of claims 1-7, characterized in that, The anode catalyst is carbon cloth or carbon paper.

14. The method according to any one of claims 1-7, characterized in that, The cathode catalyst is platinum.

15. The method according to any one of claims 1-7, characterized in that, The concentration of the electrolyte aqueous solution is 1 mg / mL to 1000 mg / mL.

16. The method according to claim 15, characterized in that, The concentration of the electrolyte aqueous solution is 3 mg / mL to 20 mg / mL.

17. The method according to any one of claims 1-7, characterized in that, The flow rate of the propylene gas is 1 s.ccm ~ 500 sccm.

18. The method according to claim 17, characterized in that, The flow rate of the propylene gas is 10 sccm to 30 s.ccm.

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