CN109055966A

CN109055966A - A kind of chemical combined method for preparing chlorine dioxide of electrochemistry-

Info

Publication number: CN109055966A
Application number: CN201811070339.3A
Authority: CN
Inventors: 唐阳; 万平玉; 莫恒亮; 孙惠; 谢鳌; 刘佳; 王力南; 庄姝娴; 龚义
Original assignee: Beijing University of Chemical Technology
Current assignee: Beijing University of Chemical Technology
Priority date: 2018-09-13
Filing date: 2018-09-13
Publication date: 2018-12-21

Abstract

A kind of chemical combined method for preparing chlorine dioxide of electrochemistry-, using the mixed solution of sodium chlorate and sulfuric acid as electrolyte, oxygen forms hydrogen peroxide in gas diffusion O_2 cathodic reduction, and the sodium chlorate, sulfuric acid in hydrogen peroxide and electrolyte occur chemical reaction and generates chlorine dioxide.In electrolytic cell outlet chlorine dioxide it is purified, absorb obtain aqueous solution of chlorine dioxide.The cathode of electrolytic cell is oxygen-consuming cathodes, and anode is that anti-corrosion non-sacrificial type analyses oxygen anodes, it is not necessary to can avoid chlorine dioxide in the reduction of cathode using cationic membrane or diaphragm.The distinguishing feature of this method is that hydrogen peroxide is directly produced by electrochemistry, reduces costs and also avoids security risk；Furthermore tank voltage is only 0.8 ~ 2 V, greatly reduces energy consumption.

Description

A kind of chemical combined method for preparing chlorine dioxide of electrochemistry-

Technical field

The present invention provides a kind of electrochemistry-the chemical combined method for preparing chlorine dioxide, and cathode is sent out especially in electrolytic cell The method that green energy conservation prepares chlorine dioxide is realized in the two-electron reduction reaction of raw oxygen.The invention belongs to water process and disinfection neck Domain.

Background technique

The preparation method of chlorine dioxide is broadly divided into sodium chlorite method and sodium chlorate method according to the difference of raw material at present. NaClO₃Compared to NaClO₂With remarkable advantage at low cost, NaClO is widely used in the industrial production₃As primary raw material, ClO is obtained after redox reaction occurs with reducing agent under acid condition₂.Common reducing agent include sulfur dioxide, chloride ion, Methanol, sucrose, hydrogen peroxide etc..Patent CN201310089330.8 in sucrose, glucose, sugar manufacturing process syrup or Syrup in sugar manufacturing process is reducing agent and NaClO₃Reaction obtains ClO₂.Patent CN200910114638.7 uses first The combined reducing agent that pure and mild hydrogen peroxide, hydrochloric acid or sodium chloride are mixed into is reacted with NaClO3 generates ClO₂Gas.Using alcohols, When carbohydrate, there are strict requirements to reducing agent dosage, otherwise easily residual causes the deterioration of reaction solution, generation secondary pollution etc. to ask Topic.Patent CN201510873365.X uses H₂O₂It is reacted as reducing agent with sodium chlorate, has benefited from H₂O₂Product is oxygen gas and water Advantage, be conducive to the separation of by-product.Compared to other reducing agents, H₂O₂Method has advantage environmental-friendly, that process is simple, but Be H2O2 at high cost and self stability it is not high and should not largely store.

Patent CN201610396232.2 discloses one kind by NaClO₃Electrolysis and crystal produce unit, ClO₂Generation unit And HCl synthesis unit, HCl is as reduction NaClO₃Generate ClO₂Reducing agent.Since whole process is related to the Cl of risk₂、H₂ And HCl synthesis unit is at there are security risks for device systems.Patent CN201210007975.8 passes through electrochemical oxidation NaClO₂Produce ClO₂, due to NaClO₂Price is higher, and need to separate the anode chamber and the cathode chamber using expensive ionic membrane to avoid oxidation product Reduction, in addition, cathode be precipitated hydrogen there is also safety problems.

To sum up, how green clean and safe restores NaClO₃Prepare ClO₂It has important practical significance and industrial value.

Summary of the invention

For existing NaClO₃Prepare ClO₂The shortcomings that technology, proposes the present invention.The purpose of the present invention is to provide a kind of nothings Need reducing agent, without ionic membrane, the electrolytic preparation ClO of low energy consumption₂The chemical combined method of electrochemistry-, have cleaning green, at The feature that this is low, product purity is high, production safety is reliable.

Electrolytic preparation ClO of the invention₂The prior art of method is characterized in that cathode uses gas diffusion oxygen cathode, Generation oxygen two-electron reduction is H₂O₂Reaction, the H generated in situ₂O₂It is reacted again with chlorate anions and generates ClO₂.Of the invention Electrolytic preparation ClO₂It is as follows that electrochemistry-chemical reaction process occurs in method, on anodes in electrolytic cells and cathode:

Anode: 2H₂O-4e^- → 4H⁺+O₂

Cathode: 2O₂+ 4H⁺+ 4e^-→ 2H₂O₂

Electrochemistry overall reaction: 2H₂O +O₂+ 4H⁺→ 2H₂O₂

Chemical reaction: 4NaClO₃+2H₂O₂+2H₂SO₄→ 4ClO₂+2Na₂SO₄+4H₂O+2O₂

Electrochemistry-chemistry overall reaction: 4NaClO₃+2H₂SO₄→ 4ClO2+2Na₂SO₄+2H₂O+O₂

In the reaction process, due to H₂O₂It is reduction reaction to occur on oxygen cathode by oxygen to generate in situ, therefore avoid Additional H₂O₂The problem of existing stability deficiency and security risk.Simultaneously as electrochemistry generates H₂O₂It can be with electrolysis after generation NaClO in slot₃Redox chemical reaction occurs, the electrochemistry-chemical reaction process in an electrolytic cell directly into Row pumps out electrolytic cell progress, and wherein the former makes device be further simplified, reduce costs.Since oxygen is sent out on oxygen cathode Raw reduction reaction produces H₂O₂Operating potential be higher than chlorate anions reduction potential, therefore NaClO₃In cathodic reduction curent density phase It can be ignored than hydrogen reduction, there is no need to use the i.e. avoidable chlorate anions of ionic membrane or diaphragm to be reduced in cathode.Consider Cathode O₂Reduction ratio cathode for hydrogen evolution operating potential wants high 1 V, and potential difference is smaller between anode.Therefore, using electric when oxygen cathode The practical slot pressure of chemical preparation Potassiumiodate is only 0.8 ~ 2 V, greatly reduces energy consumption compared to existing cathode for hydrogen evolution electrolysis mode.

The chemical combined method of electrochemistry-of the present invention prepares ClO₂Method in, cathode be mainly occur oxygen two Electronic reduction reaction, cathode product are mainly H₂O₂.Cannot have in cathod catalyst and promote direct four electron reduction of oxygen or H₂O₂ Pt, Ag, Fe, MnO of decomposition₂、Co₃O₄, perovskite, spinel components exist.

The chemical combined preparation ClO of electrochemistry-of the present invention₂Method, using no diaphragm plate frame electrolytic cell.Wherein Anode is anti-corrosion non-sacrificial type anode, using ruthenium or iridium coating layer titanium-matrix electrode, graphite or stainless steel electrode.Cathode is that may be implemented Oxygen reduction is to H₂O₂Gas-diffusion electrode, include at least electrode section and plenum section, wherein electrode section include catalysis Layer, collector and hydrophobic layer.Catalytic Layer is one or more of conductive black, graphene, carbon nanotube and polytetrafluoro The composite layer that ethylene (PTFE) is formed；Diffusion layer is the porous hydrophobic layer of high PTFE content；Collector is titanium net, in stainless (steel) wire One kind；What is be passed through in gas chamber is air or oxygen.

The chemical combined method of electrochemistry-of the present invention prepares ClO₂Method, be described in detail below:

A: contain NaClO₃ 0.1-2 mol/L、H₂SO₄The aqueous solution of 0.2-8 mol/L is added in electrolyte reservoir, is preheating to Temperature (25-95 DEG C) identical with electrolysis temperature.

B: electrolyte is injected into the sheet frame for keeping constant temperature (25-95 DEG C) using metering pump by the import of electrolytic cell lower end To hydroful in the oxygen cathode electrolytic cell of room, divides and oxygen cathode is entered by the upper end import of oxygen cathode gas chamber for the air of 10 ~ 50 kPa In gas chamber.

C: leading to direct current on anode, cathode, and current density is 100-3000 A/m²Under be electrolysed, at this moment O2 is in yin Pole occurs reduction reaction and generates H₂O₂, oxygen evolution reaction occurs on anode.

D: the gas of generation is purified, absorb after form ClO₂Aqueous solution is spare.

Specific embodiment

Technical characteristic in order to better illustrate the present invention, is illustrated below by specific embodiment.

Embodiment 1

Use plate-and-frame electrolytic cell, anode ruthenium coating titanium-matrix electrode, cathode gas diffusion oxygen cathode, oxygen cathode Catalytic Layer group It is divided into the acetylene black of PTFE and oxidation processes.Prepare NaClO₃For 1 mol/L, H₂SO₄For 5 mol/L electrolyte, 2 L, electrolyte Temperature is controlled at 45 ~ 50 DEG C.Air is passed through cathode air chamber after filtering, applies 1000 A/m of current density², electrolysis time 5 H, 0.94 ~ 1.35 V of tank voltage.It is electrolysed the ClO generated₂It is taken out of by excessive air and remaining nitrogen, is passed through absorption after filtering In bottle, ClO is obtained₂Solution.Through chemical analysis, ClO in acquired solution₂Concentration is 612 mg/L, and it is 88 that current efficiency, which is calculated, %。

Embodiment 2

Use plate-and-frame electrolytic cell, anode ruthenium iridium coating layer titanium-matrix electrode, cathode gas diffusion oxygen cathode, oxygen cathode Catalytic Layer Group is divided into the acetylene black of PTFE and oxidation processes.Prepare NaClO₃For 0.8 mol/L, H₂SO₄For 3 mol/L electrolyte, 1 L, electricity The control of liquid temperature is solved at 55 ~ 65 DEG C.Air is passed through cathode air chamber after filtering, applies 500 A/m of current density², electrolysis time 6 h, 0.82 ~ 1.16 V of tank voltage.It is electrolysed the ClO generated₂It is taken out of by excessive air and remaining nitrogen, is passed through suction after filtering It receives in bottle, obtains ClO₂Solution.Through chemical analysis, ClO in acquired solution₂Concentration is 1086 mg/L, and current efficiency is calculated For 92 %.

Embodiment 3

Use plate-and-frame electrolytic cell, anode ruthenium iridium coating layer titanium-matrix electrode, cathode gas diffusion oxygen cathode, oxygen cathode Catalytic Layer Group is divided into the Cabot carbon black of PTFE and oxidation processes.Prepare NaClO₃For 1.1 mol/L, H₂SO₄For 2 mol/L electrolyte 1 L, electrolyte temperature are controlled at 55 ~ 70 DEG C.Air is passed through cathode air chamber after filtering, applies 1200 A/m of current density², electricity Solve 3 h of time, 1.17 ~ 1.55V of tank voltage.It is electrolysed the ClO generated₂It is taken out of by excessive air and remaining nitrogen, after filtering It is passed through in absorption bottle, obtains ClO₂Solution.Through chemical analysis, ClO2 concentration is 2343 mg/L in acquired solution, and electricity is calculated Stream efficiency is 82 %.

Claims

1. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-, it is characterised in that in electrochemical reactor (electrolytic cell) Cathode use gas diffusion oxygen cathode, realizations oxygen reduction be hydrogen peroxide, the electrolysis generation hydrogen peroxide again with chlorate anions Chemical reaction occurs and generates ClO₂, anode is happens is that oxygen evolution reaction.

2. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, Anodic using ruthenium or Iridium coating layer titanium-matrix electrode, graphite or stainless steel electrode, happens is that oxygen evolution reaction on the anode.

3. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, wherein cathode be can be real Existing oxygen reduction includes at least electrode section and plenum section to the gas-diffusion electrode of hydrogen peroxide；Wherein electrode portion subpackage Include Catalytic Layer, collector and hydrophobic layer；Wherein Catalytic Layer be one or both of conductive black, graphene, carbon nanotube with The composite layer that upper and polytetrafluoroethylene (PTFE) is formed；Diffusion layer be high PTFE content porous hydrophobic layer, collector be titanium net, One of stainless (steel) wire, what is be passed through in gas chamber is air or oxygen.

4. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, wherein electrochemical cathode master If the two-electron reduction reaction of oxygen occurs.

5. cannot have in cathod catalyst the Pt, Ag for promoting direct four electron reduction of oxygen or hydrogen peroxide being promoted to decompose, Fe, MnO₂、Co₃O₄, perovskite, spinel components exist.

6. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, wherein negative in electrolysis unit Without diaphragm between pole, anode.

7. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, wherein hydrogen peroxide again with The reaction of chlorate anions carries out again after directly carrying out or pumping out in a cell electrolytic cell.

8. a kind of chemical combined method for preparing chlorine dioxide of electrochemistry-as described in claim 1, wherein chloric acid in electrolyte Sodium 0.1-2 mol/L, sulfuric acid 0.2-8 mol/L, 25-95 DEG C of electrolysis temperature, current density 100-3000A/m²。