Method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation

Abstract

The present invention discloses a method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation. The feature of the present invention is that under preferred conditions, the prepared ruthenium carbon porous electrode can realize the efficient conversion of phenol in water to p-benzoquinone under environmental conditions. The specific steps are as follows: a uniformly dispersed ruthenium carbon porous electrode is prepared by electrodeposition; an electrolyte containing phenol is injected into the anode pool of an H-type electrolytic cell, wherein the ruthenium carbon electrode is used as the anode, the platinum sheet is used as the cathode, and the silver / silver chloride electrode is used as the reference electrode; under preferred conditions, the phenol pollutant can be selectively oxidized to p-benzoquinone at the anode. The present invention can simultaneously realize the removal of phenol in water and the recovery of high value-added carbon resources, and can provide technical support for the treatment and resource utilization of organic wastewater.

Description

Technical Field

[0001] The invention belongs to the technical field of water treatment, and in particular relates to a method for selectively converting phenol in water into p-benzoquinone by using an electrocatalytic oxidation method. Background Art

[0002] Phenolic compounds are a very typical organic pollutant and are widely present in various industrial wastewaters, such as coal chemical industry, phenolic resin manufacturing and dyeing industry wastewater. Phenolic pollutants have the characteristics of large emission, difficult degradation and high toxicity. In recent years, researchers have developed a variety of oxidation processes, such as photocatalytic oxidation, electrocatalytic oxidation, persulfate-based advanced oxidation and other technologies to achieve effective degradation of phenolic pollutants in wastewater. Although these processes have shown some results, they still face the following limitations: (1) Most oxidation processes have low mineralization rates for phenolic pollutants, and the parent phenolic pollutants are usually converted into small molecular organic matter with unknown toxicity, which poses a potential threat to the ecological environment and human health; (2) The mineralization of phenolic pollutants requires a large amount of chemical agents and energy, which greatly increases the cost of wastewater treatment; (3) The above processes use the mineralization of pollutants as wastewater treatment, which does not meet the requirements of green and low-carbon water treatment development. Therefore, it is urgent to seek new strategies to achieve the effective unification of economic and environmental benefits in wastewater treatment.

[0003] Wastewater resource utilization is a feasible green path for the low-carbon development of industrial wastewater treatment. p-Benzoquinone, a frequently detected phenol degradation intermediate, is often detected by liquid chromatography-mass spectrometry due to its extremely low yield and is generally regarded as a degradation by-product. In fact, p-Benzoquinone is a key raw material for a variety of chemical products and can be used as an inhibitor, photographic developer, and cosmetic raw material. At the same time, it is also an excellent energy storage material and is expected to be used in the field of new generation energy. At present, the price of p-Benzoquinone on the market is very expensive, much higher than that of phenols. Therefore, the selective conversion of phenolic pollutants to p-Benzoquinone can not only avoid the shortcomings of high cost and high carbon emissions of traditional oxidation processes, but also achieve efficient recovery of high value-added organic resources.

[0004] Electrocatalytic oxidation is a highly controllable and mild organic matter conversion technology that has received extensive attention in the chemical and energy fields. In the field of chemical synthesis, it has been reported many times that the directional transformation of phenolic hydroxyl structures to carbonyl structures can be achieved through electrocatalytic oxidation technology. However, due to their harsh operating conditions, the reported electrocatalytic strategies are difficult to apply to wastewater resource utilization under environmental backgrounds. For example, dilute sulfuric acid is usually used as an electrolyte during the reaction process, and the reaction solvent is usually an organic solvent rather than an aqueous solvent. Therefore, in order to realize the resource utilization of phenol-containing wastewater, it is of great significance to develop a green electrocatalytic oxidation technology that can achieve the selective conversion of phenolic pollutants to p-benzoquinone under environmental backgrounds. Summary of the invention

[0005] In view of this, the purpose of the present invention is to propose a method for selectively converting phenol in water to p-benzoquinone using electrocatalytic oxidation, which is characterized in that: under environmental conditions, phenol is selectively oxidized to p-benzoquinone using electrocatalytic technology. This method can simultaneously achieve the removal of phenol pollutants in water and the recovery of organic carbon resources.

[0006] The specific technical solution for achieving the purpose of the present invention is:

[0007] A method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation, comprising the following steps:

[0008] Step 1: dissolving ruthenium trichloride in a dilute hydrochloric acid solution, stirring evenly with a magnetic force and setting aside; wherein the concentration of ruthenium trichloride is 1.0-3.0 mmol / L; the concentration of dilute hydrochloric acid is 1.0 mol / L;

[0009] Step 2: using the mixed solution obtained in step 1 as an electrolyte, using carbon cloth as a substrate, and preparing a ruthenium carbon porous electrode by an electrodeposition method;

[0010] Step 3: Dissolve phenol and sodium sulfate in ultrapure water, stir evenly with a magnetic force, and mark it as the anolyte; dissolve an equal amount of sodium sulfate in ultrapure water, stir evenly with a magnetic force, and mark it as the catholyte; wherein the phenol concentration is 0.5-4.0 mmol / L; the sodium sulfate concentration is 50-100 mmol / L; the initial pH of the anolyte and catholyte is 3.0-9.0, and the reagent for adjusting the pH value of the solution is 1.0 mol / L sulfuric acid or 1.0 mol / L sodium hydroxide solution;

[0011] Step 4: injecting the anolyte and catholyte prepared in step 3 into the anode chamber and cathode chamber of the H-type electrolytic cell respectively; using the ruthenium carbon porous electrode prepared in step 2 as the anode, and using a three-electrode system to perform an electrocatalytic oxidation reaction;

[0012] Step 5: Continuously introduce argon gas into the anode chamber, apply an electric potential, and start the electrocatalytic oxidation reaction of phenol. After a period of reaction, the selective conversion of phenol to p-benzoquinone can be achieved; wherein the applied potential is 0.8-1.0 V; and the reaction time is 150 min.

[0013] In step 2, the volume of the electrolyte is 50~100 mL; the electrodeposition method is to place the electrolyte in a three-electrode reaction cell and apply an electric potential, wherein the working electrode is a carbon cloth, the counter electrode is a titanium sheet, the reference electrode is a silver / silver chloride electrode, the electrodeposition potential is -0.6 V, and the deposition time is 10~20 min.

[0014] Beneficial effects of the present invention:

[0015] (1) The raw materials for the preparation of ruthenium carbon catalytic electrode are simple and easy to obtain, the preparation cycle is short, the preparation conditions are mild, and the preparation cost is low.

[0016] (2) This method applies electrocatalytic oxidation technology to the treatment of phenol-containing wastewater, which not only avoids the shortcomings of traditional oxidation processes such as high cost and high carbon emissions, but also achieves efficient recovery of high value-added organic resources.

[0017] (3) The electrocatalytic oxidation technology of the present invention has mild operating conditions and can be operated in complex water environments, with little background ion interference and a wide pH application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the oxidation of phenol in water to p-benzoquinone in Example 1;

[0019] Figure 2 The curve showing the change of the UV spectrum over time during the reaction of Example 1;

[0020] Figure 3 This is a graph showing the cyclic performance of the ruthenium carbon electrode in Example 1;

[0021] Figure 4 It is a performance comparison diagram of phenol removal and p-benzoquinone yield in Example 1 and Comparative Example 1;

[0022] Figure 5 This is a performance comparison chart of phenol removal and p-benzoquinone yield of Examples 1 to 4 under different initial pH conditions;

[0023] Figure 6 It is a performance comparison diagram of phenol removal and p-benzoquinone yield under different potential conditions between Example 1 and Examples 5-6;

[0024] Figure 7 This is a performance diagram of phenol removal and benzoquinone yield in actual wastewater in Example 7. DETAILED DESCRIPTION

[0025] In order to better understand the content of the present invention, the technical solution of the present invention is further described below through specific examples, comparative examples and drawings. However, these examples do not limit the protection scope of the present invention. Example 1

[0026] (1) Prepare 2 mmol / L ruthenium trichloride in 100 mL of 1.0 mol / L dilute hydrochloric acid solution, stir magnetically and set aside;

[0027] (2) The mixed solution obtained above was used as an electrolyte, and carbon cloth was used as a substrate to prepare a ruthenium carbon porous electrode by an electrodeposition method, wherein the working electrode was carbon cloth, the counter electrode was titanium sheet, the reference electrode was silver / silver chloride electrode, the electrodeposition potential was -0.6 V, and the deposition time was 10 min;

[0028] (3) Prepare 0.5 mmol / L phenol and 50 mmol / L sodium sulfate in 100 mL ultrapure water, stir them evenly with a magnetic stirrer, and mark them as the anolyte. Prepare 100 mmol / L sodium sulfate in 100 mL ultrapure water, stir them evenly with a magnetic stirrer, and mark them as the catholyte. Use 1.0 mol / L dilute sulfuric acid to adjust the initial pH of the two electrolytes to 3.0.

[0029] (4) Injecting the above-prepared anolyte and catholyte into the anode chamber and cathode chamber of the H-type electrolytic cell respectively. The ruthenium carbon porous electrode prepared in step (2) is used as the anode, and the three-electrode system is used for electrocatalytic oxidation;

[0030] (5) Argon gas was continuously introduced into the anode chamber and a potential of 0.9 V was applied to initiate the electrocatalytic oxidation reaction of phenol. After a reaction time of 150 min, the selective conversion of phenol to p-benzoquinone was achieved.

[0031] Example 1 Schematic diagram of oxidation of phenol in water to p-benzoquinone Figure 1 As shown, and the curve of the change of UV spectrum with time during the reaction process is as shown Figure 2 As shown, it can be seen that as the reaction proceeds, the intensity of the characteristic peak of phenol (270 nm) gradually decreases, while the intensity of the corresponding characteristic peak of p-benzoquinone (246 nm) gradually increases, which indirectly reflects that the catalytic system can effectively oxidize phenol to p-benzoquinone.

[0032] The cyclic performance of the ruthenium carbon porous electrode in Example 1 is as follows: Figure 3 As shown, the results show that after the ruthenium carbon porous electrode is recycled 8 times, its activity has no obvious change, indicating that the prepared ruthenium carbon porous electrode has high stability.

[0033] Comparative Example 1

[0034] The difference between this comparative example and Example 1 is that a carbon electrode without ruthenium loading is used instead of the ruthenium carbon porous electrode.

[0035] The performance comparison of phenol removal and benzoquinone yield in Example 1 and Comparative Example 1 is shown in the figure below: Figure 4As shown in the figure, the results show that when a single carbon electrode is used as the anode, the concentration changes of phenol and p-benzoquinone in the solution can be basically ignored. When a ruthenium carbon porous electrode is used, the phenol concentration gradually decreases with the reaction time, and 96.4% removal can be achieved within 150 minutes. Correspondingly, the concentration of p-benzoquinone in the solution gradually increases with the reaction time, and the yield of p-benzoquinone reaches 78.9% after 150 minutes. This data fully demonstrates that the ruthenium carbon porous electrode can achieve the selective conversion of phenol to p-benzoquinone under optimized conditions. Example 2

[0036] The difference between this embodiment and embodiment 1 is that the initial pH of the two electrolytes in step (3) is adjusted to 5.0. Example 3

[0037] The difference between this embodiment and embodiment 1 is that the initial pH of the two electrolytes in step (3) is adjusted to 7.0 using 1.0 mol / L sodium hydroxide solution. Example 4

[0038] The difference between this embodiment and embodiment 1 is that the initial pH of the two electrolytes in step (3) is adjusted to 9.0 using 1.0 mol / L sodium hydroxide solution.

[0039] The performance of the electrocatalytic oxidation system in Examples 1 to 4 on the degradation of phenol and the production of benzoquinone under different initial pH conditions is as follows: Figure 5 The results showed that the increase in pH (3.0-9.0) had little effect on the removal of phenol (96.4%-93.4%), but caused a slow decrease in the yield of p-benzoquinone (78.9%-64.3%). This was attributed to the fact that in a neutral or alkaline environment, the oxygen evolution side reaction was more favorable, and the small amount of p-benzoquinone produced would be further oxidized. Example 5

[0040] The difference between this embodiment and embodiment 1 is that the applied potential in step (5) is adjusted to 0.8 V. Example 6

[0041] The difference between this embodiment and embodiment 1 is that the applied potential in step (5) is adjusted to 1.0 V.

[0042] The performance of the electrocatalytic oxidation system in Examples 1 and 5-6 on the degradation of phenol and the production of benzoquinone under different potential conditions is as follows: Figure 6 As shown. The results show that 0.9 V is the optimal applied potential. At 0.8 V, the applied potential is too small and is not enough to completely oxidize phenol within the effective time. However, even if too high a voltage (such as 1.0 V) can completely remove phenol, it will further oxidize the generated p-benzoquinone, resulting in a decrease in the yield of p-benzoquinone. Example 7

[0043] (1) Prepare 2 mmol / L ruthenium trichloride in 100 mL of 1.0 mol / L dilute hydrochloric acid solution, stir magnetically and set aside;

[0044] (2) The mixed solution obtained above was used as an electrolyte, and carbon cloth was used as a substrate to prepare a ruthenium carbon porous electrode by an electrodeposition method, wherein the working electrode was carbon cloth, the counter electrode was titanium sheet, the reference electrode was silver / silver chloride electrode, the electrodeposition potential was -0.6 V, and the deposition time was 10 min;

[0045] (3) 100 mL of actual coking wastewater containing 2.0 mmol / L was marked as the anolyte, and 100 mmol / L of sodium sulfate was prepared in 100 mL of ultrapure water. After magnetic stirring, it was marked as the catholyte. The initial pH of the two electrolytes was adjusted to 3.0 using 1.0 mol / L dilute sulfuric acid.

[0046] (4) Injecting the above-prepared anolyte and catholyte into the anode chamber and cathode chamber of the H-type electrolytic cell respectively. The ruthenium carbon porous electrode prepared in step (2) is used as the anode, and the three-electrode system is used for electrocatalytic oxidation;

[0047] (5) Argon gas was continuously introduced into the anode chamber and a potential of 0.9 V was applied to start the electrocatalytic oxidation reaction of phenol. After a reaction time of 150 min, the selective conversion of phenol in the wastewater to p-benzoquinone was achieved.

[0048] Example 7 Phenol removal and benzoquinone yield performance in actual wastewater Figure 7 The results show that for actual coking wastewater containing phenol, the electrocatalytic oxidation system can achieve 93.1% removal of phenol within 7 h, and the yield of benzoquinone can reach 65.9%. This data fully demonstrates that the system of the present invention has certain practical application potential in the resource utilization of phenol-containing wastewater.

[0049] It can be seen from the above embodiments that the present invention provides a method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation. The method of the present invention can not only achieve the effect of purifying wastewater, but also simultaneously realize the recovery of high value-added organic resources.

[0050] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation, characterized in that: The following steps are involved: Step 1: dissolving ruthenium trichloride in a dilute hydrochloric acid solution, stirring evenly with a magnetic force and setting aside; wherein the concentration of ruthenium trichloride is 1.0-3.0 mmol / L; the concentration of dilute hydrochloric acid is 1.0 mol / L; Step 2: using the mixed solution obtained in step 1 as an electrolyte, using carbon cloth as a substrate, and preparing a ruthenium carbon porous electrode by an electrodeposition method; Step 3: Dissolve phenol and sodium sulfate in ultrapure water, stir them evenly with a magnetic force, and mark them as the anolyte; dissolve an equal amount of sodium sulfate in ultrapure water, stir them evenly with a magnetic force, and mark them as the catholyte; wherein the concentration of phenol is 0.5-4.0 mmol / L; the concentration of sodium sulfate is 50-100 mmol / L; the initial pH of the anolyte and catholyte is 3.0-9.0, and the reagent for adjusting the pH value of the solution is 1.0 mol / L sulfuric acid or 1.0 mol / L sodium hydroxide solution; Step 4: injecting the anolyte and catholyte prepared in step 3 into the anode chamber and cathode chamber of the H-type electrolytic cell respectively; using the ruthenium carbon porous electrode prepared in step 2 as the anode, and using a three-electrode system to perform an electrocatalytic oxidation reaction; Step 5: Continuously introduce argon gas into the anode chamber, apply an electric potential, and start the electrocatalytic oxidation reaction of phenol. After a period of reaction, the selective conversion of phenol to p-benzoquinone can be achieved; wherein the applied potential is 0.8-1.0 V; and the reaction time is 150 min.

2. A method for selectively converting phenol in water to p-benzoquinone by electrocatalytic oxidation as claimed in claim 1, characterized in that: Step 2, the volume of the electrolyte is 50~100 mL; the electrodeposition method is to place the electrolyte in a three-electrode reaction cell and apply an electric potential, wherein the working electrode is a carbon cloth, the counter electrode is a titanium sheet, the reference electrode is a silver / silver chloride electrode, the electrodeposition potential is -0.6 V, and the deposition time is 10~20 min.

Images