Method for producing hydrogen by electrochemically degrading organic wastes in ethylene glycol production

Abstract

The invention relates to the technical field of hydrogen production by water electrolysis, and discloses a method for producing hydrogen by electrochemically degrading organic waste in ethylene glycol production, which comprises the following steps: S1, mixing the organic waste in ethylene glycol production with a redox mediator, acid and a noble metal catalyst, and heating to perform degradation reaction, the redox mediator receives electrons released by oxidation of the organic waste in the reaction process and converts the electrons into low-valence ions; and S2, the reaction liquid obtained in the step S1 enters an electrolysis device to serve as anode electrolyte to be used for circulating electrolytic hydrogen production, low-valence ions are subjected to coupling electrolysis at the anode to be regenerated and return to the step S1 to participate in degradation again, and hydrogen is produced from water on the cathode side. According to the method, the redox mediator can be recycled, organic waste can be effectively degraded, hydrogen can be efficiently produced, and compared with electrolyzed water, the power consumption for producing hydrogen with the same volume is reduced by 50% or above.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen production by electrolysis, and particularly to a method for producing hydrogen by electrochemically degrading organic waste in ethylene glycol production. Background Art

[0002] Ethylene Glycol (EG), as an important organic compound, is widely used in multiple fields such as chemical industry, automotive antifreeze, polyester fiber production, solvents, and cosmetics. However, with the widespread use of ethylene glycol, the problem of treating the waste liquid generated in its production process has become increasingly prominent.

[0003] The degradation industry of ethylene glycol organic waste liquid generally includes steam distillation, membrane separation technology, oxidative decomposition, chemical precipitation, microbial degradation, etc. Steam distillation utilizes the difference in boiling points between ethylene glycol and other substances to separate ethylene glycol from the waste liquid through a distillation device. This method is applicable to waste liquid with a high ethylene glycol concentration but requires a large amount of energy and equipment investment (such as CN116874353A, CN219907094U). Membrane separation technology adopts membrane separation technologies such as reverse osmosis and nanofiltration, and utilizes the selective permeability of the membrane to separate ethylene glycol from the waste liquid. This method has the advantages of high efficiency, energy conservation, and environmental protection, but the price of membrane separation equipment is relatively high, and the membrane is prone to pollution and blockage. Oxidative decomposition utilizes strong oxidants (such as ozone, hydrogen peroxide, etc.) to oxidize ethylene glycol into low-toxic or non-toxic substances. This method can effectively reduce the toxicity of the waste liquid, but attention needs to be paid to controlling the reaction conditions to avoid secondary pollution (such as CN114804537A). Chemical precipitation is to add chemical reagents to form precipitates of harmful substances such as heavy metal ions in the waste liquid and separate them. This method is applicable to treating ethylene glycol waste liquid containing heavy metal ions and may introduce new pollutants at the same time. The biological treatment method is to convert ethylene glycol into harmless substances such as carbon dioxide and water through the metabolic action of specific microorganisms, but the treatment efficiency for high-concentration ethylene glycol waste liquid is relatively low, and the environmental temperature requirement is relatively high. All of these methods for treating ethylene glycol organic waste liquid have their own defects, such as high energy consumption and large input costs, resulting in slow industry development. Therefore, there is an urgent need to develop and design a highly efficient, environmentally friendly, and low-energy-consuming method for degrading ethylene glycol waste liquid and apply it to the actual industry.

[0004] CN114182294 A discloses a dual-catalyst system and method for electrochemically degrading biomass refining organic waste to produce hydrogen. This method adds biomass refining organic waste to the catalyst system for degradation and then uses it for electrolytic hydrogen production. The main components are cellulose and some hydrolyzed product sugars. However, ethylene glycol organic waste mainly consists of polymers with many ether bonds, having characteristics such as high boiling point, high viscosity, and severe browning, and it is more difficult to treat and degrade ethylene glycol organic waste. Summary of the Invention

[0005] The present invention provides a method for electrochemically degrading organic waste in ethylene glycol production to produce hydrogen, which can effectively degrade organic waste and efficiently produce hydrogen.

[0006] The technical solution of the present invention is to provide a method for electrochemically degrading organic waste in ethylene glycol production to produce hydrogen, including the following steps: S1. Mix the organic waste in ethylene glycol production with a redox mediator, an acid, and a noble metal catalyst, and heat for a degradation reaction. The redox mediator receives the electrons released by the oxidation of the organic waste during the reaction and is converted into a low-valent ion. S2. The reaction solution obtained in S1 enters an electrolysis device as an anolyte for cyclic electrolysis to produce hydrogen. Among them, the low-valent ion is regenerated through coupled electrolysis at the anode and returns to S1 to participate in the degradation again, and hydrogen is produced by the catalytic reaction of water on the cathode side under the catalysis of a Pt / C catalyst.

[0007] Optionally, the organic waste in ethylene glycol production is a viscous substance, and it is diluted during the degradation reaction to control its concentration in the degradation system to be 0.01 - 2 mol / L.

[0008] Optionally, the redox mediator contains polyoxometalate, polyoxometalate salt, or variable-valent metal ion, or a combination thereof.

[0009] Optionally, the concentration of the redox mediator in the degradation system is 0.05 - 3 mol / L.

[0010] Optionally, the polyoxometalate includes, but is not limited to, H 6 P 2 Mo 18 O 62 (P 2 Mo 18 ), H 3 PMo 12 O 40 (PMo 12 ), H 4 SiMo 12 O 40 or H 6 PMo 9 V 3 O 40 ; the polyoxometalate salt is a polyoxometalate doped with variable-valent metal ions, such as P 2 Mo 17 Cu, P 2 Mo 17 Fe, P 2 Mo 17 Mn, P 2 Mo 17 V or P 2 Mo16 V 2 ; The mixed system of polyoxometallic acid and variable valence metal ions is P 2 Mo 18 +Cu 2+ , P 2 Mo 18 +V 5+ , P 2 Mo 18 +Cr 6+ , P 2 Mo 18 +Fe 3+ or P 2 Mo 18 +Mn 4+ .

[0011] Optionally, the noble metal catalyst includes but is not limited to Pt / C, Pt / SiO 2 、Pt / Al 2 O 3 , Ru / C, Pd / C or Rh / C.

[0012] Optionally, in the degradation reaction system, the concentration of the acid is 0.1-3 mol / L. Optionally, during the degradation reaction, the acid is phosphoric acid.

[0013] Optionally, during the degradation reaction in S1, the temperature is controlled at 80°C to 160°C, and the reaction time is 1 to 24 hours.

[0014] Optionally, during electrolysis, the voltage is 0.5~3V and the current is 20~200mA / cm 2 .

[0015] The present invention has the following beneficial effects: (1) The present invention uses polyoxometalates or variable-valence metal ions as redox mediators to greenly degrade organic waste in ethylene glycol production, and cooperates with low-concentration acids and inorganic metal catalysts to mildly degrade ethylene glycol waste into carbon dioxide and water. The polyoxometalates or variable-valence ions obtained by degradation can be used as anolyte and regenerated through a coupled electrolysis process. At the same time, the cathode side can produce hydrogen efficiently with low energy consumption under the catalytic action of Pt / C catalyst.

[0016] (2) The coupling and synergistic increase of polyoxometalates and precious metal catalysts in this system improves the degradation efficiency of ethylene glycol waste. At the same time, polyoxometalates and precious metal catalysts are relatively stable in this system, have good self-healing and durability, and are not prone to poisoning effects. Therefore, they can be reused many times, greatly increasing the efficiency of ethylene glycol organic waste degradation.

[0017] (3) During the electrolysis process to produce hydrogen, the coupling and synergy between metal oxygenates and inorganic metal catalysts increase, accelerating the reaction with ethylene glycol organic waste, resulting in a reduction in the working voltage required for electrolysis and enabling hydrogen production with low energy consumption. Compared with electrolyzing water, the electrical energy consumed to produce the same volume of hydrogen is more than 50% lower.

[0018] (4) Ethylene glycol organic waste is mainly composed of ether bond-containing organic compounds, with high viscosity and boiling point, and is difficult to separate. Using this electrolysis system method for degradation, the process flow is simple and the energy consumption is low. When degrading ethylene glycol organic waste, it can effectively achieve waste recycling and reduce resource consumption, while also producing renewable green hydrogen energy. Description of the Drawings

[0019] Figure 1 It is the electrolysis polarization curve after the reaction of ethylene glycol organic waste in Example 1.

[0020] Figure 2 It is the graph of the change of electrolysis voltage with time after the reaction of ethylene glycol organic waste in Example 1.

[0021] Figure 3 It is the graph of the volume of hydrogen electrolyzed varying with time in Example 1.

[0022] Figure 4 It is the hydrogen production curve by electrolysis after the reaction of ethylene glycol organic waste at different concentrations in Example 2.

[0023] Figure 5 It is the graph of the change of the number of electrolysis times with the organic carbon content in Example 3.

[0024] Figure 6 It is the cyclic hydrogen production curve by electrolysis in Example 4. Detailed Embodiments

[0025] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials used in the following embodiments are all commercially available products unless otherwise specified.

[0026] For the organic waste in ethylene glycol production used in the following examples and comparative examples, the total organic carbon analyzer (TOC) was used to test the organic carbon content, which was 823.3 mg / L.

[0027] The following will describe the implementation schemes of the present invention in detail with reference to the examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.

[0028] Example 1 Take 5 g of ethylene glycol organic waste in 0.3 mol / L H 6 P2 Mo 18 O 62 (P 2 Mo 18 ) solution, with a total solution volume of 50 mL, reacts at a temperature of 100 °C for 2 hours. After the reaction, the reaction solution is fed into an electrolytic cell through a continuous flow pump for electrolysis. The area of the electrolytic cell is 40 cm 2 , and the electrolysis current is 25 mA / cm 2 . After 10 hours of electrolysis, 200 mL of hydrogen gas is obtained. As shown in Figure 1 , the electrolysis polarization curve shows that the initial decomposition voltage is 0.5 V; Figure 2 The reaction solution is introduced into a laboratory continuous flow electrolytic cell. At an electrolysis current of 25 mA / cm 2 , the electrolysis reaction is completed after 10 hours, and 200 liters of hydrogen gas is collected simultaneously ( Figure 3 ).

[0029] Example 2 Add different concentrations of ethylene glycol organic waste and react with polyoxometalate in 0.3 mol / L H 6 P 2 Mo 18 O 62 , 1 mol / L phosphoric acid, and 3 g of Pt / SiO 2 in a high-temperature resistant reaction flask. Add 0.006 mol / L, 0.06 mol / L, and 0.6 mol / L of ethylene glycol organic waste respectively, with a total volume of 30 mL. Under the conditions of a temperature of 150 °C and a magnetic stirrer speed of 400 r / min, react continuously for 6 hours. As shown in Table 1 and Figure 4 , the experimental results show that when reacting with different concentrations of ethylene glycol organic waste, the consumption of ethylene glycol organic waste and the Faraday efficiency of electrolytic hydrogen production are different. Generally speaking, the best effect is achieved when adding 0.06 mol / L of ethylene glycol waste.

[0030] Table 1

[0031] Example 3. Determination of organic carbon content after electrolysis of the reaction between ethylene glycol organic waste and polyoxometalate Take 10 g of ethylene glycol organic waste in 0.3 mol / L H 6 P 2 Mo 18 O 62 solution, with a total solution volume of 100 ml, reflux at 100 °C for 2 h for cyclic electrolytic hydrogen production. After each cyclic electrolysis, use TOC to test the content of organic matter in the electrolyte. In an electrolytic cell with an area of 40 cm 2, the electrolysis current is between 20 and 100 mA / cm 2 After 7 cycles of electrolytic hydrogen production, the organic carbon content in the ethylene glycol organic waste is 16.97 mg / L, and the degradation rate is 57.45% compared with the original solution (as shown in Table 2 below, Figure 5 shown).

[0032] Table 2

[0033] Example 4. Recycling hydrogen production by the reaction of ethylene glycol organic waste with polyoxometalate Take 15 g of ethylene glycol organic waste and add it to 0.3 mol / L H 6 P 2 Mo 18 O 62 solution, with a total volume of 60 ml. Add 1 mol / L phosphoric acid and 2 g of Pt / C catalyst, and react at 100 °C for 24 hours. After the reaction, in an electrolytic cell with an area of 40 cm 2 , the electrolysis current is tested for hydrogen production performance between 20 and 100 mA / cm 2 After seven cycles of electrolytic hydrogen production, the organic carbon content in the ethylene glycol organic waste is 5.17 mg / L, a decrease of 90.77% compared with the original solution (as shown in Table 3 below, Figure 6 shown). Compared with Example 3, when an inorganic acid and an inorganic metal catalyst are added, the degradation rate of ethylene glycol organic waste increases after the cyclic reaction.

[0034] Table 3

[0035] Example 5. Influence of adding inorganic catalyst on the cyclic degradation of ethylene glycol organic waste Take 10 g of ethylene glycol organic waste in 0.3 mol / L H 6 P 2 Mo 18 O 62 solution, with a total volume of 100 ml. Add or not add an inorganic catalyst respectively, and react at 100 °C for 2 hours. As shown in Table 4 below, after adding the inorganic metal catalyst, the consumption of ethylene glycol organic waste is much higher than that without adding the catalyst, reaching 90.9%.

[0036] Table 4

[0037] Example 6. Influence of different catalysts on the degradation of ethylene glycol organic waste Repeat Example 5. After adding the inorganic catalyst, the consumption of ethylene glycol organic waste increases. Therefore, experiments with different catalysts were added. When different inorganic catalysts were added, it had a significant impact on the degradation, electrolytic regeneration, and hydrogen production of ethylene glycol organic waste. The specific experimental results are shown in Table 5.

[0038] Table 5

[0039] Example 7. Effect of adding phosphoric acid on the degradation of ethylene glycol organic waste Take 10 g of ethylene glycol organic waste in 0.3 mol / L H 6 P 2 Mo 18 O 62 solution, with a total volume of 100 ml. Add or not add 0.1 - 3 mol / L phosphoric acid solution. At a temperature of 100 °C, react for 2 hours. After the reaction, electrolyze hydrogen production in an electrolytic cell with an area of 40 cm 2 , and the current is between 20 - 100 mA / cm 2 . The results show that after adding 1 mol / L phosphoric acid solution, the consumption of ethylene glycol organic waste reaches 88.9%, which is much higher than the consumption when adding low-concentration inorganic acids. And the Faraday efficiency of hydrogen production is 97% (as shown in Table 6).

[0040] Table 6

[0041] Example 8. Effect of different redox mediators on the degradation of ethylene glycol organic waste React different polyoxometalates and variable valence state ion species with ethylene glycol organic waste. Other conditions are the same as in Example 4. After the regeneration of the polyoxoacid, polyoxometalate, and variable valence state ion catalyst, it is repeatedly used for the degradation of ethylene glycol waste liquid. After 3 times of degradation, different polyoxometalates and variable valence state ion species have a significant impact on the degradation, electrolytic regeneration, and hydrogen production of ethylene glycol organic waste. The results are shown in Table 7. It can be seen from the results that the catalytic system composed of P 2 Mo 18 and different variable valence state ions has good catalytic degradation and repeated use ability for ethylene glycol organic waste.

[0042] Table 7

[0043] The above embodiments describe the preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including any other combination of each technical feature. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for producing hydrogen by electrochemically degrading organic waste in ethylene glycol production, characterized in that: The following steps are involved: S1. Mixing organic waste from ethylene glycol production with a redox mediator, an acid and a precious metal catalyst, and heating them to perform a degradation reaction. During the reaction, the redox mediator receives electrons released by oxidation of the organic waste and converts them into low-valent ions. The reaction liquid obtained from S2 and S1 enters the electrolysis device as the anode electrolyte for cyclic electrolysis to produce hydrogen, wherein the low-valent ions are regenerated in the anode coupled electrolysis and return to S1 to participate in degradation again, and the water on the cathode side produces hydrogen during the electrolysis process.

2. The method according to claim 1, characterized in that: The organic waste in ethylene glycol production is viscous, and it is diluted during the degradation reaction to control its concentration in the degradation system to 0.01~2mol / L.

3. The method according to claim 1, characterized in that: The redox mediator contains polyoxometallic acid, polyoxometallic acid salt or variable valence metal ion, or a combination thereof.

4. The method according to claim 1, characterized in that: The concentration of the redox mediator in the degradation system is 0.05-3 mol / L.

5. The method according to claim 3, characterized in that: The polyoxometallic acids include but are not limited to H6P2Mo 18 O 62 (P2Mo 18 ), H3PMo 12 O 40 (PMo 12 ), H4SiMo 12 O 40 or H6PMo9V3O 40 ; The polyoxometalate is a polyoxometalate P2Mo doped with variable valence metal ions 17 Cu、P2Mo 17 Fe、P2Mo 17 Mn、P2Mo 17 V or P2Mo 16 V2; the mixed system of polyoxometallic acid and variable valence metal ions is P2Mo 18 +Cu 2+ 、P2Mo 18 +V 5+ 、P2Mo 18 +Cr 6+ 、P2Mo 18 +Fe 3+ or P2Mo 18 +Mn 4+ .

6. The method according to any one of claims 1 to 5, characterized in that: The noble metal catalyst includes but is not limited to Pt / C, Pt / SiO2, Pt / Al2O3, Ru / C, Pd / C or Rh / C.

7. The method according to any one of claims 1 to 5, characterized in that: In the degradation reaction system, the acid concentration is 0.1-3 mol / L.

8. The method according to claim 6, characterized in that: During the degradation reaction, the acid is phosphoric acid.

9. The method according to claim 1, characterized in that: During the degradation reaction in S1, the temperature is controlled at 80°C~160°C.

10. The method according to claim 1, characterized in that: During electrolysis, the current is 20~200mA / cm 2 .

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