阅读说明：本技术 一种银或银镍合金催化的电化学脱氯处理二氯甲烷的方法 (Method for electrochemical dechlorination treatment of dichloromethane under catalysis of silver or silver-nickel alloy ) 是由 倪建国 刘奇 谢国建 徐颖华 于 2020-04-03 设计创作，主要内容包括：本发明公开一种银或银镍合金催化的电化学脱氯处理二氯甲烷的方法。以酸性溶液为反应介质,二氯甲烷加入到酸性溶液构成电解反应液,作为阴极液；以碱性水溶液为阳极液；以银或银镍合金为阴极,在阳极液中化学惰性导电材料或涂覆贵金属氧化物的钛金属为阳极置于电解槽中进行电化学反应。其中所述的阴极液在反应过程中,pH保持在1～5。所述的酸性溶液是由溶剂和支持电解质混合配制而成的,溶剂为水和其他质子性有机溶剂的混合溶剂。本发明采用银镍合金作为电极材料,催化活性高且容易加工；实现利用电化学法将二氯甲烷高选择性(＞90％)的转化成甲烷,有利于回收。(The invention discloses a method for electrochemical dechlorination treatment of dichloromethane under the catalysis of silver or silver-nickel alloy. Adding dichloromethane into an acidic solution serving as a reaction medium to form an electrolytic reaction solution serving as a catholyte; taking an alkaline aqueous solution as an anolyte; silver or silver-nickel alloy is taken as a cathode, a chemical inert conductive material or titanium metal coated with noble metal oxide is taken as an anode in anolyte, and the anode is placed in an electrolytic bath for electrochemical reaction. Wherein the pH of the catholyte is kept between 1 and 5 in the reaction process. The acidic solution is prepared by mixing a solvent and a supporting electrolyte, wherein the solvent is a mixed solvent of water and other protonic organic solvents. The invention adopts silver-nickel alloy as electrode material, has high catalytic activity and is easy to process; the method realizes the conversion of dichloromethane into methane with high selectivity (more than 90%) by an electrochemical method, and is favorable for recovery.)

1. AA method for processing dichloromethane by electrochemical dechlorination under the catalysis of silver is characterized by comprising the following steps: adding dichloromethane into an acidic solution serving as a reaction medium to form an electrolytic reaction solution serving as a catholyte; taking an alkaline aqueous solution as an anolyte; silver is taken as a cathode, a chemical inert conductive material or a titanium metal coated with noble metal oxide is taken as an anode in anolyte, and the anode is placed in an electrolytic bath for electrochemical reaction; wherein the pH of the catholyte is kept between 1 and 5 in the reaction process; the current density of the electrochemical reaction is 1-6A/dm²(ii) a The electrolysis temperature is-10 to 80 ℃;

the acid solution is prepared by mixing a solvent and a supporting electrolyte, wherein the content of the supporting electrolyte in an electrolytic reaction solution is 0.05-0.5 mol/L; the supporting electrolyte is a salt which can be dissolved in the acidic solution, the solvent is a mixed solvent of water and other protonic organic solvents, and the content of the protonic organic solvent in the electrolytic reaction liquid is 20-90 wt%.

2. A method for electrochemical dechlorination treatment of dichloromethane catalyzed by silver-nickel alloy is characterized by comprising the following steps: adding dichloromethane into an acidic solution serving as a reaction medium to form an electrolytic reaction solution serving as a catholyte; taking an alkaline aqueous solution as an anolyte; placing silver-nickel alloy as a cathode and a chemically inert conductive material or a titanium metal coated with a noble metal oxide as an anode in an anolyte into an electrolytic tank for electrochemical reaction; wherein the pH of the catholyte is kept between 1 and 5 in the reaction process; the current density of the electrochemical reaction is 1-6A/dm²(ii) a The electrolysis temperature is-10 to 80 ℃;

the acid solution is prepared by mixing a solvent and a supporting electrolyte, wherein the content of the supporting electrolyte in an electrolytic reaction solution is 0.05-0.5 mol/L; the supporting electrolyte is a salt which can be dissolved in the acidic solution, the solvent is a mixed solvent of water and other protonic organic solvents, and the content of the protonic organic solvent in the electrolytic reaction liquid is 20-90 wt%.

3. The method according to claim 2, wherein the silver-nickel alloy contains 0 to 40 wt% of nickel and does not contain 0 wt%.

4. The method according to claim 3, wherein the silver-nickel alloy contains 0 to 10 wt% of nickel and does not contain 0 wt%.

5. The method according to any one of claims 1 to 4, wherein the supporting electrolyte is a salt of a cation which is a lithium ion or an ammonium ion and an anion which is a chloride ion or a perchlorate ion.

6. The process according to any one of claims 1 to 4, wherein the protic organic solvent is a mixture of a C1-C4 organic alcohol and acetic acid.

7. The method according to any one of claims 1 to 4, wherein the content of methylene chloride in the electrolytic reaction solution is 0.01 to 1 mol/L.

8. The method according to any one of claims 1 to 4, wherein the aqueous alkaline solution is an aqueous solution of LiOH or NaOH.

9. The method according to any one of claims 1 to 4, wherein the electrolysis temperature is 10 to 35 ℃.

10. A method according to any one of claims 1 to 4, wherein the membrane of the cell is a perfluorosulphonic acid cation membrane.

Technical Field

The invention belongs to the technical field of electrochemical dechlorination, relates to a dechlorination method for chlorine-containing Volatile Organic Compounds (VOCs), and particularly relates to a method for dechlorinating dichloromethane by using silver or silver-nickel alloy as a catalyst.

Background

Chlorine-containing VOCs can pose serious threats to human health and the global ecological environment. Such as: at present, chlorine-containing VOCs (volatile organic compounds) such as chloroethenes, chloromethanes and the like which are widely used have a 'three-cause' effect; the refrigerant freon (chlorofluoroalkane) which is used in large quantity generates serious damage to the ozone layer in the atmosphere stratosphere; research on the Martyn Chipperfield topic group at the university of british showed: dichloromethane is also an ozone depletion substance, and the recovery process of the Antarctic ozone layer is slowed down for 5-30 years due to the continuous increase of global dichloromethane emission [ Nat Commun 8, 15962(2017) ]. The exploration of an effective treatment method for the chlorine-containing VOCs has become one of the urgent problems in the environmental protection field of all countries in the world. The toxicity of the chlorine-containing VOCs is mainly caused by the introduction of chlorine elements, and chlorine atoms have higher electronegativity, so that the difficulty of electrophilic reaction is increased along with the increase of chlorine substituents, and the degradability of the chlorine-containing VOCs is greatly reduced. If the chlorine atoms in the chlorine-containing VOCs are removed, the generated chlorine-free product can be recycled as a raw material or used as a green fuel. Therefore, the research on the efficient dechlorination method of the chlorine-containing VOCs has important application value.

Research by the group of professors of Armando Gennaro, italy, has found that electrochemical dechlorination processes can be used for the dechlorination of chlorine-containing VOCs: both tetrachloromethane and trichloromethane were completely dechlorinated on copper electrodes in DMF solvent [ applied catalysis B: environmental 126(2012)347-354], the major product being methane; both trichloroethylene and dichloroethylene can be thoroughly dechlorinated to ethylene and ethane [ Applied Catalysis B: environmental 126(2012) 355-362 ]. Research conducted by the group of professors of Sandra Rondinini, Italy has found that on silver electrodes in acetonitrile solvent, trichloromethane and dichloromethane can also be completely dechlorinated to methane [ Electrochimica acta 49(2004) 4035-4046 ]. The two methods have the defects that solvents DMF and acetonitrile have high toxicity and easily cause secondary pollution; the conductivity of the catholyte is poor, and the cell pressure is high; poor selectivity of the dechlorination reaction results in non-uniform products which are not beneficial to recovery, for example, the yield of methane produced by dechlorination of tetrachloromethane and trichloromethane on a copper electrode is less than 80% at most [ Applied Catalysis B: environmental 126(2012) 347-354; silver is expensive, the electrocatalytic activity needs to be further improved, and in addition, the material is too soft and is not easy to be processed into an electrode.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a method for electrochemical dechlorination treatment of dichloromethane under the catalysis of silver or silver-nickel alloy.

The technical scheme adopted by the invention is as follows:

adding dichloromethane into an acidic solution serving as a reaction medium to form an electrolytic reaction solution serving as a catholyte; taking an alkaline aqueous solution as an anolyte; silver or silver-nickel alloy is taken as a cathode, a chemical inert conductive material or titanium metal coated with noble metal oxide is taken as an anode in anolyte, and the anode is placed in an electrolytic bath for electrochemical reaction. Wherein the pH of the catholyte is kept between 1 and 5 in the reaction process.

The invention breaks through the original intention of adding nickel into silver in the prior art to improve the mechanical strength of the electrode, but the addition of nickel in a proper proportion is discovered unintentionally, and the catalytic dechlorination activity and the product selectivity of the electrode can be improved unexpectedly. The content of nickel in the silver-nickel alloy is 0-40 wt%, and 0% is not contained, preferably 0-10 wt%, and 0% is not contained, particularly preferably 5 wt%.

The acid solution is prepared by mixing a solvent and a supporting electrolyte, wherein the content of the supporting electrolyte in the electrolytic reaction solution is 0.05-0.5 mol/L. The supporting electrolyte is a salt which can be dissolved in the acidic solution, specifically a salt consisting of cations and anions, wherein the cations are lithium ions or ammonium ions, and the anions are chloride ions or perchlorate ions. The solvent is a mixed solvent of water and other protonic organic solvents, and the content of the protonic organic solvent in the electrolytic reaction liquid is 20-90 wt%; wherein the protonic organic solvent is a mixture of C1-C4 organic alcohol and acetic acid, and the C1-C4 organic alcohol is methanol, ethanol, n-propanol, isopropanol, n-butanol, etc., preferably ethanol.

The cathode may be in the form of a plate, rod, wire, mesh, net, foam, fleece or sheet, preferably a net.

The current density of the electrochemical reaction is 1-6A/dm²。

In the electrolytic reaction process, the corresponding current density is changed according to the concentration change of dichloromethane in an electrolytic reaction liquid, and the content of dichloromethane in the electrolytic reaction liquid is 0.01-1 mol/L, preferably 0.05-0.5 mol/L.

The alkaline aqueous solution is LiOH aqueous solution or NaOH aqueous solution.

The anode material may be any chemically inert conductive material in an alkaline aqueous solution, such as stainless steel, platinum, graphite, carbon, conductive plastics. The anode may also consist of a coating applied to another material, for example: a noble metal oxide such as ruthenium oxide is coated onto the titanium metal. 316L stainless steel is preferred as the anode.

The electrolysis temperature is-10 to 80 ℃, and 10 to 35 ℃ is preferred as the temperature of the electrolysis reaction in consideration of volatilization of the solvent, solubility of the reactant in the electrolysis reaction solution, and conductivity of the electrolysis reaction solution.

The cell pressure in the electrolysis process is 7-10V.

The electrolysis reaction according to the invention can be carried out batchwise or in a continuous or semi-continuous manner. The electrolysis cell may be a stirred cell containing electrodes or a flow cell of any conventional design. The electrolytic cell may be a single-chamber cell or a diaphragm cell, preferably a diaphragm cell. Separator materials which can be used are various anion or cation exchange membranes, porous Teflon, asbestos or glass, preferably perfluorosulphonic cation membranes, as the diaphragm of the electrolysis cell.

While oxygen evolution as an anodic reaction is preferred, many other anodic reactions can be used. Including the evolution of chlorine and bromine molecules, or the production of carbon dioxide by the oxidation of protective materials such as formate or oxalate or the formation of valuable by-products by the oxidation of organic reactants.

The invention has the following beneficial effects:

(1) the invention adopts silver-nickel alloy as electrode material, has high catalytic activity and is easy to process;

(2) the solvent adopted by the method is green and environment-friendly and is convenient to recover;

(3) the catholyte adopted by the method has good conductivity and low pressure of the electrolytic bath;

(4) the invention realizes the conversion of dichloromethane into methane with high selectivity (more than 90%) by an electrochemical method, and is beneficial to recovery.

Drawings

FIG. 1 is an H-type electrolytic cell used in the present invention.

Detailed Description

The present invention is further illustrated by the following examples, which are not intended to limit the scope of the invention.