Preparation method of Ru-WO3 nano-catalyst as well as product and application of Ru-WO3 nano-catalyst

Abstract

The invention discloses a preparation method of a Ru-WO3 nano-catalyst and a product and application of the Ru-WO3 nano-catalyst, the preparation method of the Ru-WO3 nano-catalyst comprises the following steps: adding ammonium metatungstate into deionized water, stirring to obtain a solution A, then adding citric acid into the solution A to obtain a solution B, mixing the solution B and a titanium felt, and carrying out hydrothermal reaction to obtain a WO3-x carrier; the preparation method comprises the following steps: dipping a WO3-x carrier in a RuCl3 aqueous solution to obtain a Ru-WO3-x precursor; the Ru-WO3-x precursor is subjected to calcination, and a Ru-WO3 nano catalyst is obtained; the mass ratio of the ammonium metatungstate to the citric acid is 2.4 to 10. The Ru-WO3 nano-catalyst prepared by the preparation method is high in activity and selectivity, and is beneficial to improving the synthesis efficiency of electrically driven ethylene glycol.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electrocatalysis, and particularly relates to a preparation method of a Ru-WO3 nano catalyst, a product thereof and application thereof. BACKGROUND

[0002] Ethylene glycol, as an important basic chemical, has a wide range of applications in polymer synthesis, antifreeze preparation, energy storage and other fields. According to reports, the global ethylene glycol production capacity has exceeded 230 million tons in 2023, and its annual growth rate will maintain at a level of 4-5%. In traditional industrial production, ethylene glycol is mainly prepared by a two-step method: first, ethylene (C2H4) is oxidized to ethylene oxide by a thermal catalytic oxidation process, and then an opening reaction of the epoxide compound is performed. However, this process not only needs to be carried out under severe reaction conditions (200-300℃, 1-3 MPa O2), but also will be accompanied by about 1.6 tons of carbon dioxide emission per ton of ethylene glycol produced. In comparison, the electrochemical driven ethylene conversion to ethylene glycol technology exhibits significant advantages, which can be operated under normal temperature and pressure conditions, and is expected to be powered by renewable energy, providing a new technical path for realizing green and sustainable ethylene glycol production.

[0003] So far, researchers have made certain achievements in the efficiency of electro-driven ethylene glycol synthesis by designing excellent catalysts and constructing reasonable reaction routes. However, due to the low solubility of ethylene and the problem of multiple oxidation byproducts, the current density of the catalytic system is low (<20 mA cm-2), and the faradic efficiency is low (<80%), which seriously limits the application of the system. -2

[0004] The patent document with the publication number CN115448817A discloses a method for preparing ethylene glycol by one-step oxidation of ethylene coupled with electrocatalysis and thermal catalysis, which comprises the following steps: coating a carbon-based electrocatalyst on both sides of an electrode substrate to obtain an electrode sheet as a cathode, assembling an H-type electrolytic cell; adding an electrolyte containing a titanium-silicon molecular sieve heterogeneous catalyst to the cathode side, and continuously introducing a mixture of oxygen and ethylene to the cathode side to saturate it; using a constant potential method, each potential is continuously electrolyzed. The application realizes the coupling of electrocatalysis and thermal catalysis reaction. In addition, the application uses wood-derived biomass carbon material as the electrode substrate, which has good conductivity, the ethylene glycol yield reaches 70.16 mmol / gcath, and the hydrogen peroxide utilization rate reaches 86%; the TS-1 thermal catalyst is formed, which increases its service life and cycle stability. The technical route of the application is to use a carbon-based catalyst to electro-reduce oxygen to prepare H2O2, and then couple with a thermal catalyst TS-1 to prepare ethylene glycol by one-step oxidation of ethylene. Although the application realizes the synthesis of ethylene glycol under mild conditions, the cathode electrocatalysis and suspended thermal catalysis need to be controlled at the same time, the reaction path is complex, and it is not conducive to scale-up. ​

[0005] The patent document with publication number CN119530854A discloses a preparation method of a CoNC catalyst for ethylene oxidation to ethylene glycol, belonging to the field of ethylene oxidation, which comprises the following steps: first, dissolve cobalt nitrate hexahydrate, zinc nitrate hexahydrate and dimethyl imidazole in methanol respectively, mix the two solutions uniformly, stir overnight, obtain a purple suspension, centrifuge, wash and dry the suspension to obtain a purple solid, grind after high-temperature calcination for 3 hours under an argon atmosphere, and obtain the CoNC catalyst. The synthesis method is relatively simple in industry, the synthesized material is resistant to high temperature and has good stability, and shows good performance in the test of electrocatalytic ethylene to ethylene glycol. The application uses the CoNC catalyst as an anode to generate ethylene glycol by one-step electro-oxidation of ethylene in an H-type electrolytic cell. However, although the process path is simple, the low current density and low yield of the system show that the catalytic efficiency needs to be further improved.

[0006] Therefore, in order to improve the efficiency of electro-driven ethylene glycol synthesis, it is urgent to develop a catalyst with high activity and selectivity. SUMMARY

[0007] In view of the deficiencies of the prior art, the first aspect of the present application provides a preparation method of Ru-WO3 nanocatalyst, which has high activity and selectivity and is beneficial to improve the efficiency of electro-driven ethylene glycol synthesis.

[0008] The preparation method of Ru-WO3 nanocatalyst provided by the present application comprises: (1) stirring ammonium metatungstate in deionized water to obtain solution A, then adding citric acid to the solution A to obtain solution B, mixing the solution B and titanium felt, and then performing hydrothermal reaction to obtain WO 3-x carrier; (2) immersing the WO 3-x carrier in RuCl3 aqueous solution to obtain Ru-WO 3-x precursor, and x is an oxygen vacancy; (3) calcining the Ru-WO 3-x precursor to obtain Ru-WO3 nanocatalyst; The mass ratio of the ammonium metatungstate to the citric acid is 2.4-10.

[0009] The content of the ammonium metatungstate and the citric acid solution is controlled in the embodiments of the present application, so that the prepared Ru-WO3 nanocatalyst has a nanoneedle assembled cluster structure, which is beneficial to improve the catalyst activity.

[0010] Preferably, the titanium felt has a size of 10mm*30mm*0.1mm-30mm*30mm*0.3mm, and needs to be cleaned before the hydrothermal reaction, the cleaning solution is 10-30wt% oxalic acid solution, the cleaning time is 10-60 minutes, and the cleaning temperature is 75-95℃; the titanium felt needs to be cleaned with deionized water and ethanol after the hydrothermal reaction and is placed in a vacuum oven at 40-80℃ for drying.

[0011] Preferably, the hydrothermal reaction has a temperature of 160-200℃ and a reaction time of 10h-14h.

[0012] Preferably, the RuCl3 aqueous solution has a concentration of 0.1-10mmol / L and an immersion time of 6h-12h.

[0013] Preferably, the Ru-WO3 nanometer catalyst has a size of 10-30nm. 3-x The precursor needs to be washed and dried with deionized water and ethanol before calcination.

[0014] Preferably, the calcination has a temperature of 400-500℃ and a holding time of 2h-4h.

[0015] In a second aspect, the application further provides a Ru-WO3 nanometer catalyst prepared by the preparation method of the Ru-WO3 nanometer catalyst.

[0016] The Ru-WO3 nanometer catalyst provided by the embodiments of the application has a nanometer needle assembled cluster structure, high catalytic activity and selectivity, and is beneficial to improving the efficiency of electrically driven ethylene glycol synthesis.

[0017] Compared with the prior art, the Ru-WO3 nanometer catalyst provided by the embodiments of the application has no obvious loss of W element in the electrolysis process, and the homogeneous system is beneficial to strengthening the catalytic effect, thereby improving the Faraday efficiency of ethylene glycol, and thus, compared with the WO3 or RuO2 catalysts disclosed in the prior art, the Ru-WO3 nanometer catalyst provided by the application has high catalytic performance.

[0018] Preferably, in the Ru-WO3 nanometer catalyst, the elements of Ru, W and O are uniformly distributed, and the mass ratios of Ru, W and O are 1.2-3.6%, 76.7-79.1% and 19.7-21.4% respectively, so as to ensure that the active sites on the catalyst can uniformly and fully participate in the reaction, and improve the efficiency and selectivity of the reaction.

[0019] In a third aspect, the embodiments of the application further provide an application of the Ru-WO3 nanometer catalyst in an electrically driven ethylene glycol synthesis reaction, which comprises: In the alkaline electrolyte system, the alkaline electrolyte is a mixture of potassium hydroxide and potassium bromide, the Ru-WO3 nano catalyst is used as the anode, and ethylene gas is continuously introduced to convert ethylene into ethylene glycol through electrocatalytic reaction.

[0020] The existing process of electrically driving ethylene glycol synthesis has low current density (less than 20 mA cm - ²) due to the low solubility of ethylene in the aqueous electrolyte, and is limited by the low selectivity caused by the easy over-oxidation of ethylene to generate by-products such as ethylene oxide, formic acid, bromoethanol, etc., resulting in low sub- faradic efficiency (less than 80%), and the traditional thermal catalysis requires harsh conditions of high temperature and high pressure. The Ru-WO3 nano catalyst is used for the electrically driving ethylene glycol synthesis reaction in the embodiment of the present application, and the reaction route is: first, Br - is in-situ oxidized to BrO - by the Ru-WO3 nano catalyst, and then BrO - is used to directly oxidize ethylene to synthesize ethylene glycol, which is an electrocatalysis-chemical catalysis coupling process, different from direct electrode reaction.

[0021] Because the Ru-WO3 nano catalyst provided in the embodiment of the present application has excellent catalytic ability for Br - to BrO - , BrO - can be generated in-situ, and BrO - has high selectivity for oxidizing ethylene to produce ethylene glycol at room temperature, so BrO - can act as an oxidizing agent to react with ethylene in the solution, without the need for ethylene to be adsorbed on the electrode surface, completely avoiding the mass transfer limitation at the electrode-electrolyte interface, effectively solving the problem of low solubility of ethylene in the aqueous electrolyte, and the high selectivity of BrO - for oxidation simultaneously reduces the side reaction of over-oxidation of ethylene, significantly inhibits the generation of by-products such as ethylene oxide, and thus comprehensively improves the faradic efficiency and current density of the electrically driven ethylene glycol synthesis.

[0022] The reason for controlling the electrolyte to be an alkaline electrolyte in the embodiment of the present application is that the alkaline environment is a necessary condition for the Ru-WO3 nano catalyst to effectively catalyze Br - to BrO - , and when the electrode liquid is neutral or acidic, the main product is only bromoethanol, and the faradic efficiency is significantly reduced, and the target product ethylene glycol cannot be efficiently generated.

[0023] Further preferably, the molar ratio of potassium bromide to potassium hydroxide is 10-60. By controlling the concentration of potassium bromide, the electrolyte can be more effectively ensured to be in a strong alkaline environment, which is beneficial to the electrically driving Ru-WO3 catalysis of ethylene to BrO- The reaction path of the intermediate indirect oxidation to ethylene glycol is crucial, and the effect of insufficient alkalinity of the electrolyte on the catalytic efficiency is minimized, the ethylene glycol Faraday efficiency is reduced, and the side reaction of inducing oxygen evolution is minimized to affect the efficient generation of the target product ethylene glycol.

[0024] Preferably, the concentration of potassium hydroxide is one of 0.01 mol / L, 0.05 mol / L and 0.1 mol / L, and the concentration of potassium bromide is one of 1 mol / L and 3 mol / L. The concentration of potassium hydroxide is 0.05-0.1 mol / L, and the concentration of potassium bromide is 1-3 mol / L.

[0025] Further preferably, the concentration of potassium hydroxide is 0.05 mol / L, and the concentration of potassium bromide is 3 mol / L, and the catalytic effect can reach a good level under this combination of concentrations, so that the ethylene glycol electro-synthesis Faraday efficiency reaches 88.7%, and the current density reaches 50 mA cm -2 .

[0026] Preferably, the flow rate of ethylene gas is 30-100 mL / min. The present application controls the flow rate of ethylene, which can minimize the impact of ethylene on the catalyst surface, cover the active sites, increase the mass transfer resistance between the electrode and the electrolyte, and thus affect the efficient reaction.

[0027] Preferably, the counter electrode of the electro-catalytic reaction is a C rod, the reference electrode is Hg / HgO, the applied current is 10 mA cm -2 -100 mA cm -2 , and the anode product is detected by nuclear magnetic resonance hydrogen spectrum. The present application can realize ethylene glycol Faraday efficiency higher than 60% by controlling the current density, which indicates that the Ru-WO3 nanocatalyst has stable and good effect on the electro-driven ethylene glycol synthesis reaction.

[0028] Compared with the prior art, the present application has the following beneficial effects: The present application can efficiently prepare the Ru-WO3 nanocatalyst with a spherical cluster structure by controlling the mass ratio of citric acid and ammonium metatungstate, and the spherical cluster structure is assembled by nanoneedles, and the prepared Ru-WO3 nanocatalyst has high catalytic performance.

[0029] The present application significantly improves the efficiency of the electro-driven ethylene glycol synthesis reaction by preparing the Ru-WO3 nanocatalyst with a spherical cluster structure assembled by nanoneedles. The Ru-WO3 nanocatalyst can efficiently catalyze Br - to BrO - , and BrO -The catalyst can selectively oxidize ethylene to generate ethylene glycol at room temperature, compared with direct electrocatalytic oxidation of ethylene, the catalyst can generate BrO-oxidant in situ to directly oxidize ethylene to ethylene glycol, effectively overcoming the problems of low ethylene solubility and excessive oxidation, and the synergistic effect of components avoids the problem of W loss in the electrolysis process, and further improves the catalytic effect. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 X-ray diffraction patterns of Ru-WO3 and WO3 catalysts prepared in Example 1 and Comparative Example 3 of the present application; Figure 2 Raman spectra of Ru-WO3 and WO3 catalysts prepared in Example 1 and Comparative Example 3 of the present application; Figure 3 Scanning electron microscope images of Ru-WO3 catalyst prepared in Example 1 of the present application; Figure 4 Scanning electron microscope images of Ru-WO3 catalyst prepared in Example 1, 2 and 3 of the present application; Figure 5 Faraday efficiency diagram of electrocatalytic oxidation of ethylene at a current density of 10-100 mA cm-2 in Application Example 1 provided by the present application; -2 Figure 6 Faraday efficiency diagram of ethylene oxidation catalyzed by Ru-WO3 electrode prepared in Example 1, 2 and 3 of the present application; Figure 7 Faraday efficiency diagram of ethylene oxidation catalyzed by Ru-WO3 electrode in Application Examples 1, 2, 3 and 4 provided by the present application, and the electrolyte composition is 1M KBr and 0.01M KOH, and the electrolyte composition is 3M KBr and 0.01M KOH; Figure 8 UV spectra of the electrolyte after electrolysis and after electrolysis and passing ethylene in Application Example 1 provided by the present application, using Ru-WO3 as the electrode; Figure 9 Product nuclear magnetic hydrogen spectrum in Application Example 1 provided by the present application, using Ru-WO3 as the electrode, after electrolysis and passing ethylene; Figure 10 Faraday efficiency diagram of ethylene oxidation catalyzed by Ru-WO3 electrode in Example 1 and Comparative Examples 1 and 2 of the present application; Figure 11 Time-voltage curve, faraday efficiency diagram and electrolyte diagram after catalytic reaction of Ru-WO3, WO3 and RuO2 electrodes prepared in Example 1 and Comparative Examples 3 and 4 of the present application, wherein, Figure 11 ​(a) is the time-voltage curve of Ru-WO3, WO3, and RuO2 electrodes prepared in Example 1 of the present invention and Comparative Examples 3 and 4, Figure 11 (b) is a Faradaic efficiency diagram of Ru-WO3, WO3, and RuO2 electrodes catalyzing ethylene oxidation prepared in Example 1 of the present invention and Comparative Examples 3 and 4. Figure 11 (c) is a diagram of the electrolyte after the catalytic reaction of Ru-WO3 and WO3 electrodes prepared in Example 1 of the present invention and Comparative Example 3. DETAILED DESCRIPTION

[0031] Example 1 The preparation method of the Ru-WO3 nanocatalyst provided in this embodiment is: The titanium felt was cut into a size of 10mm*30mm*0.2mm and placed in a 20wt% oxalic acid solution at 90℃ for 30min. 0.89g of ammonium metatungstate was weighed and dissolved in 35mL of deionized water and stirred evenly to obtain solution A. 0.18g of citric acid was weighed and dissolved in solution A to obtain solution B. The washed titanium felt and solution B were transferred to a hydrothermal autoclave and kept at 180℃ for reaction for 12h. After the reaction, they were washed with deionized water and ethanol and dried to obtain WO 3-x . Will WO 3-x The catalyst was placed in a 5 mmol / L RuCl3 solution and immersed at room temperature for 8 h. After washing with deionized water and ethanol and drying, it was calcined at 450°C in a muffle furnace for 2 h to obtain the catalyst Ru-WO3.

[0032] The Ru-WO3 prepared in Example 1 was subjected to X-ray diffraction analysis ( Figure 1 ), the characteristic diffraction peaks of WO3 were found, which can be indexed as standard PDF cards (85-2460). No Ru-related diffraction peaks were found in the spectrum because the Ru content was low and entered the WO3 bulk phase in the form of doping.

[0033] The Ru-WO3 prepared in Example 1 was subjected to Raman spectroscopy analysis ( Figure 2 ), obvious OWO bending vibration peaks (solid box) and stretching vibration peaks (dashed box) were found in the WO3 support.

[0034] Scanning electron microscopy analysis of the Ru-WO3 prepared in Example 1 revealed that the Ru-WO3 was in a spherical cluster structure assembled by nanoneedles ( Figure 3 ), elemental analysis shows the uniform distribution of Ru, W and O, among which the mass proportions of Ru, W and O are 3.6%, 76.7% and 19.7% respectively.

[0035] Example 2 The only difference from Example 1 is that in Example 2, 0.09 g of citric acid is added to obtain the catalyst Ru-WO3-2.

[0036] Scanning electron microscopy analysis of the Ru-WO3-2 prepared in Example 2 revealed that the Ru-WO3-2 exhibited a nanoneedle structure.

[0037] Example 3 The only difference from Example 1 is that in Example 3, 0.36 g of citric acid is added to obtain the catalyst Ru-WO3-3.

[0038] Scanning electron microscopy analysis of the Ru-WO3-3 prepared in Example 3 revealed that the Ru-WO3-3 exhibited a nanoneedle structure.

[0039] like Figure 4 As shown, Examples 1, 2, and 3 illustrate that when the mass ratio of ammonium metatungstate to citric acid is within the range of 2.4-10, the Ru-WO3 nanocatalyst can effectively form a spherical cluster structure assembled by nanoneedles, and the morphology can be stably formed.

[0040] Application Example 1 A three-electrode system was constructed using the Ru-WO3 prepared in Example 1 as an ethylene oxidation electrocatalyst for electrochemical testing. The anode electrode was Ru-WO3, the cathode electrode was a carbon rod, and the reference electrode was Hg / HgO. The anode electrode was placed at the anode. The anolyte consisted of 25 ml of a potassium hydroxide solution containing 3 mol / L potassium bromide (0.05 mol / L potassium hydroxide). The catholyte composition was the same as that of the anode. Ethylene was continuously introduced into the anode during the electrolysis process at a gas flow rate of 60 mL / min.

[0041] Test different current densities (10 mA cm -2 -100mA cm -2 ) under Ru-WO3 catalytic ethylene oxidation to ethylene glycol Faradaic efficiency, Figure 5 It shows that the catalyst Ru-WO3 has a -2 -100mA cm -2 The Faradaic efficiency of ethylene glycol production is higher than 60% within the current density range, and the main by-products are ethylene oxide, formic acid and bromoethanol. -2 When the reaction temperature is 0.5000 ℃, the Faradaic efficiency of producing ethylene glycol can reach 84.5%.

[0042] Test 50mA cm -2 Time-voltage curve of Ru-WO3 catalytic ethylene oxidation under current density, Figure 11 (a) shows that the catalyst Ru-WO3 maintains a stable voltage response during electrolysis, with a voltage of 1.78 V (vs. reversible hydrogen electrode).

[0043] Without ethylene, 50 mA cm -2 Current density, the UV-vis spectra of electrolyte with and without ethylene after Ru-WO3 electrolysis, as shown in Figure 8 Without ethylene, Ru-WO3 electrolysis produces BrO - oxidation species, whose UV-vis characteristic peak is at 328 nm. After electrolysis with ethylene, the characteristic peak disappears (as shown in Figure 8 the blue line), indicating that BrO - oxidation species chemically reacts with ethylene.

[0044] Test 50 mA cm -2 Current density, the nuclear magnetic resonance hydrogen spectrum of the product after Ru-WO3 electrolysis and then with ethylene, Figure 9 indicates that after electrolysis at 50 mA cm -2 Current density and then with ethylene, ethylene glycol product is produced, indicating that the reaction route is that Ru-WO3 catalyzes Br - oxidation to BrO - species, and then BrO - species oxidizes ethylene to ethylene glycol, and the nuclear magnetic resonance provided by the application is dimethyl sulfoxide.

[0045] Application Example 2 The difference between this application example 2 and application example 1 is only that the electrolyte composition of this application example 2 is 25 ml of potassium bromide containing 1 mol / L potassium hydroxide solution, and the concentration of potassium hydroxide is 0.05 mol / L.

[0046] Test 50 mA cm -2 Current density, the Faraday efficiency of ethylene glycol produced by Ru-WO3 catalytic ethylene oxidation, Figure 7 indicates that this electrolyte combination shows good ethylene glycol Faraday efficiency, which is 73.1%.

[0047] Application Example 3 The difference between this application example 3 and application example 1 is only that the electrolyte composition of this application example 3 is 25 ml of potassium bromide containing 1 mol / L potassium hydroxide solution, and the concentration of potassium hydroxide is 0.1 mol / L.

[0048] Test 50 mA cm -2 Current density, the Faraday efficiency of ethylene glycol produced by Ru-WO3 catalytic ethylene oxidation, Figure 7 indicates that this electrolyte combination shows good ethylene glycol Faraday efficiency, which is 75.0%.

[0049] Application Example 4 The difference between this application example 4 and application example 1 is only that the electrolyte composition of this application example 4 is 25 ml of potassium bromide containing 3 mol / L potassium hydroxide solution, and the concentration of potassium hydroxide is 0.1 mol / L.

[0050] Test 50mA cm -2 Faradaic efficiency of Ru-WO3 catalyzed ethylene oxidation to ethylene glycol at current density of 50mA cm-2, Figure 7 The electrolyte combination shows a good ethylene glycol faradaic efficiency of 74.9%.

[0051] In summary, the faradaic efficiency of Ru-WO3 catalyzed ethylene oxidation to ethylene glycol in different concentrations of potassium hydroxide (0.01mol / L, 0.05mol / L, 0.1mol / L) and potassium bromide (1mol / L, 3mol / L) electrolyte is tested, as shown in Table 1. Figure 7 As shown in Table 1, when the alkalinity is weak (0.01mol / L), the ethylene glycol faradaic efficiency is low (<20%), while when the alkalinity is strong (0.05mol / L, 0.1mol / L), the ethylene glycol faradaic efficiency is high (>70%), indicating that a strong alkaline environment is a necessary condition for electrically driven Ru-WO3 catalyzed ethylene oxidation to ethylene glycol. However, a stronger alkaline environment can lead to the occurrence of oxygen evolution side reactions, so there is an optimal ratio of potassium bromide and potassium hydroxide concentration, and the ratio range is 10-60. When the concentration of potassium hydroxide is 0.05mol / L and the concentration of potassium bromide is 3mol / L, the ethylene glycol faradaic efficiency can reach 84.5%.

[0052] Application Example 5 The difference between this application example 5 and application example 1 is that Ru-WO3-2 prepared in example 2 is used as an ethylene oxidation electrocatalyst.

[0053] Test 50mA cm -2 Faradaic efficiency of Ru-WO3-2 catalyzed ethylene oxidation to ethylene glycol at current density of 50mA cm-2, Figure 6 It is shown that Ru-WO3-2 as an ethylene oxidation electrocatalyst shows a good ethylene glycol faradaic efficiency of 75.7%.

[0054] Application Example 6 The difference between this application example 6 and application example 1 is that Ru-WO3-3 prepared in example 3 is used as an ethylene oxidation electrocatalyst.

[0055] Test 50mA cm -2 Faradaic efficiency of Ru-WO3-2 catalyzed ethylene oxidation to ethylene glycol at current density of 50mA cm-2, Figure 6 It is shown that Ru-WO3-3 as an ethylene oxidation electrocatalyst shows a good ethylene glycol faradaic efficiency of 88.7%.

[0056] In summary, application examples 1, 5, and 6 show that within the range of mass ratio of ammonium metatungstate to citric acid 2.4-10, there is a good effect of synthesizing ethylene glycol.

[0057] Comparative Example 1 The only difference from Application Example 1 is that the electrolyte composition of this Comparative Example 1 is 25 ml of potassium bromide solution, and the concentration of potassium bromide is 3 mol / L.

[0058] Figure 10 It shows that when the electrolyte is neutral, the only product is bromoethanol, and its Faradaic efficiency is 40%.

[0059] Comparative Example 2 The only difference from Application Example 1 is that the electrolyte composition of Comparative Example 2 is 25 ml of sulfuric acid solution containing 3 mol / L potassium bromide, and the sulfuric acid concentration is 0.05 mol / L.

[0060] Figure 10 It shows that when the electrolyte is acidic, the only product is bromoethanol, and its Faradaic efficiency is 37.4%.

[0061] Comparative Examples 1 and 2 show that alkaline environment is the best environment for Ru-WO3 to catalyze Br - BrO production - The necessary conditions for the efficient production of target product ethylene glycol.

[0062] Comparative Example 3 The WO prepared in Example 1 3-x The catalyst WO3 was obtained by calcining at 450°C in a muffle furnace for 2 h.

[0063] X-ray diffraction analysis of the catalyst WO3 was performed ( Figure 1 ), the characteristic diffraction peaks of WO3 were found, which can be indexed as standard PDF cards (71-2141), indicating the successful preparation of WO3 catalyst. Raman spectroscopy analysis of WO3 was also performed ( Figure 2 ), obvious OWO bending vibration peaks (solid box) and stretching vibration peaks (dashed box) were found in the WO3 support, confirming the successful preparation of WO3 catalyst.

[0064] The only difference from Application Example 1 is that this Comparative Example 3 uses WO3 catalyst as the ethylene oxidation electrocatalyst.

[0065] Test 50mA cm -2 Performance of WO3 catalytic ethylene oxidation at different current densities, Figure 11 (a) shows that WO3 exhibits a higher electrolysis potential than Ru-WO3 and RuO2, and its electrolysis potential is higher at 50 mA cm -2 The Faradaic efficiency of catalytic ethylene oxidation to ethylene glycol at the current density is the lowest, which is 27.1% ( Figure 11 (b)).

[0066] Comparative Example 4 5 mg RuO2and 1 mg carbon black were mixed in a solution containing 200 μl deionized water, 750 μl isopropanol, 50 μl nafion binder and ultrasonicated for 30 min to disperse. The dispersion was dropped on a cleaned titanium felt with an active area of 1 cm 2 and a loading of 2.5 mg / cm 2 . After drying, a RuO2electrode was obtained.

[0067] The difference between this example and Example 1 is that this example uses a RuO2electrode as the electrocatalyst for ethylene oxidation.

[0068] The performance of the RuO2electrode in catalyzing ethylene oxidation was tested at a current density of 50 mA cm -2 , and the results are shown in (a) and (b) of Table 1. Figure 11 (a) shows that the RuO2electrode exhibits a higher electrolysis potential than Ru-WO3and a lower electrolysis potential than WO3, and its Faraday efficiency in catalyzing ethylene oxidation to produce ethylene glycol at a current density of 50 mA cm -2 is lower, being 29.8% (b). Figure 11

[0069] The results of Comparative Examples 3 and 4 show that the synergistic effect between Ru and WO3components in the Ru-WO3nanocatalyst promotes the efficient electro-synthesis of ethylene glycol. As shown in (c), pure WO3exhibits a significant loss of W during the electrolysis process, and leads to the formation of insoluble tungstate, which seriously reduces its catalytic performance, while the Ru-WO3exhibits excellent stability, without significant loss of W. This fully proves the importance of introducing Ru elements for stabilizing the WO3carrier and improving its Faraday efficiency in electrocatalyzing ethylene oxidation to produce ethylene glycol. Figure 11 (a) shows that the RuO2electrode exhibits a higher electrolysis potential than Ru-WO3and a lower electrolysis potential than WO3, and its Faraday efficiency in catalyzing ethylene oxidation to produce ethylene glycol at a current density of 50 mA cm -2 is lower, being 29.8% (b). Figure 11

[0069] The results of Comparative Examples 3 and 4 show that the synergistic effect between Ru and WO3components in the Ru-WO3nanocatalyst promotes the efficient electro-synthesis of ethylene glycol. As shown in (c), pure WO3exhibits a significant loss of W during the electrolysis process, and leads to the formation of insoluble tungstate, which seriously reduces its catalytic performance, while the Ru-WO3exhibits excellent stability, without significant loss of W. This fully proves the importance of introducing Ru elements for stabilizing the WO3carrier and improving its Faraday efficiency in electrocatalyzing ethylene oxidation to produce ethylene glycol. Figure 11 (c).

Claims

1. A method for preparing Ru-WO3 nanocatalyst, characterized in that: include: Ammonium metatungstate was added to deionized water and stirred to obtain solution A. Citric acid was then added to the solution A to obtain solution B. The solution B was mixed with titanium felt and subjected to hydrothermal reaction to obtain WO 3-x carrier; Will WO 3-x The support was immersed in RuCl3 aqueous solution to obtain Ru-WO 3-x Precursor; Will Ru-WO 3-x The precursor is calcined to obtain Ru-WO3 nanocatalyst; The mass ratio of the ammonium metatungstate to the citric acid is 2.4-10.

2. The method for preparing Ru-WO3 nanocatalyst according to claim 1, characterized in that: The temperature of the hydrothermal reaction is 160-200° C., and the reaction time is 10 h-14 h.

3. The method for preparing Ru-WO3 nanocatalyst according to claim 1, characterized in that: The concentration of the RuCl3 aqueous solution is 0.1-10 mmol / L, and the immersion time is 6h-12h.

4. A Ru-WO3 nanocatalyst prepared according to the preparation method of Ru-WO3 nanocatalyst according to any one of claims 1 to 3.

5. The Ru-WO3 nanocatalyst according to claim 4, characterized in that The Ru-WO3 nanocatalyst is a spherical cluster structure assembled by nanoneedles.

6. The Ru-WO3 nanocatalyst according to claim 4, characterized in that In the Ru-WO3 nanocatalyst, Ru, W, and O elements are evenly distributed, with the mass proportions of Ru, W, and O being 1.2-3.6%, 76.7-79.1%, and 19.7-21.4%, respectively.

7. Use of the Ru-WO3 nanocatalyst according to any one of claims 4 to 6 in an electrically driven ethylene glycol synthesis reaction, characterized in that: include: In an alkaline electrolyte system, the alkaline electrolyte is a mixture of potassium hydroxide and potassium bromide, the Ru-WO3 nanocatalyst is used as the anode, ethylene gas is continuously introduced, and ethylene is converted into ethylene glycol through an electrocatalytic reaction.

8. The use of the Ru-WO3 nanocatalyst in an electrically driven ethylene glycol synthesis reaction according to claim 7, characterized in that: The molar ratio of potassium bromide to potassium hydroxide is 10-60.

9. The use of the Ru-WO3 nanocatalyst in an electrically driven ethylene glycol synthesis reaction according to claim 7, characterized in that: The flow rate of the ethylene gas is 30-100 mL / min.

10. The use of the Ru-WO3 nanocatalyst in an electrically driven ethylene glycol synthesis reaction according to claim 7, characterized in that: The counter electrode of the electrocatalytic reaction is a C rod, the reference electrode is Hg / HgO, and the applied current is 10 mA cm -2 Up to 100mA cm -2 .

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