CN101392386A - Electrochemical method for the simultaneous production of sodium chlorate and alkaline hydrogen peroxide - Google Patents

Abstract

The invention relates to an electrochemical method for simultaneously producing sodium chlorate and alkaline hydrogen peroxide, which can improve the utilization efficiency of two poles of electric current and reduce production cost. The present invention uses a kind of electrolytic cell that is made up of anode, cation exchange membrane, anion exchange membrane and negative electrode, and electrode and film are combined in turn to form anode chamber, intermediate chamber and cathode chamber; Lead sodium chloride and chloric acid to the anode chamber of electrolyzer Sodium solution, the cathode chamber leads to sodium hydroxide solution and air, the middle chamber leads to sodium hydroxide solution, after the direct current is passed between the electrodes, the anode generates chlorine gas, the cathode oxygen is reduced to generate hydrogen peroxide, and the concentration of sodium hydroxide solution in the middle chamber increases; The anolyte from the anode chamber flows into an external heated reaction tank, where chlorine gas is converted to sodium chlorate, and the anolyte is recycled back to the anode chamber of the electrolytic cell, and part of the concentrated sodium hydroxide solution that flows out of the intermediate chamber can be used to adjust the pH of the anolyte , no need to use additional sodium hydroxide, which can reduce operating costs.

Description

Electrochemical method for the simultaneous production of sodium chlorate and alkaline hydrogen peroxide

technical field

The invention relates to an electrochemical method for simultaneously producing sodium chlorate and alkaline hydrogen peroxide, belonging to the field of chemical production.

Background technique

The technology of separately preparing sodium chlorate or alkaline hydrogen peroxide by electrochemical method is relatively mature. For example, the conventional chlorate production method described in "Electrolytic production of sodium chloride" by J. Coleman (AICh. E. Symposium 204 vol 77 1981. pp244-263). Sodium chlorate is produced by electrolyzing a sodium chloride solution in a single-chamber electrolyzer, producing chlorine gas at the anode and hydrogen gas and hydroxide ions at the cathode. Chlorine gas is hydrolyzed to generate hypochlorous acid, which further undergoes a homogeneous chemical reaction in an independent heated reaction tank to generate chlorate. The electrochemical method to produce sodium chlorate generally uses a saturated sodium chloride solution at 60-80°C with a current density of 1-3kA/m ² .

US Patents 3,969,201, 4,118,305 and 4,406,758 describe electrochemical processes for the preparation of alkaline hydrogen peroxide solutions by cathodic reduction of oxygen in alkaline solutions. The cathode used in these patents is a three-dimensional graphite cathode, and the electrolyte is NaOH aqueous solution. The concentration of NaOH solution is 1-3mol/L, the temperature is 20-30°C, the apparent cathode current density is 0.1-1kA/m ² , and the oxygen pressure can be greater than one atmospheric pressure to increase the space-time yield of hydrogen peroxide.

The anode and cathode of the same electrolytic cell can be electrolyzed simultaneously to produce useful products. When the anode chamber and the cathode chamber are separated by a porous membrane, electrolyzed water can obtain hydrogen and oxygen at the same time. When a cation exchange membrane or a porous membrane is used to separate the anode chamber and the cathode chamber, electrolysis of sodium chloride can obtain chlorine gas and sodium hydroxide. US Patent 3,884,777 describes the invention of the simultaneous electrolytic production of chlorine dioxide, hydrogen peroxide, sodium hydroxide and chlorine gas by a three-compartment electrolyzer, wherein the hydrogen peroxide is produced by the anodic oxidation of sulfuric acid.

Japanese Patent 61-284591 relates to an electrochemical method for simultaneously preparing alkaline hydrogen peroxide and chlorine gas or sodium chlorate. The electrolytic cell used is a chambered electrolytic cell, and the electrodes are graphite cathode and noble metal anode respectively, and the anode and cathode are separated by a porous diaphragm. Examples of the invention employ only cation exchange membranes, such as DuPont's Nafion 315. Due to the use of a cation exchange membrane, it is necessary to add an equivalent chemical equivalent of sodium hydroxide to the anolyte to adjust the pH of the anolyte to 6-7 during the electrolysis process, which increases the operating cost.

Contents of the invention

The purpose of the present invention is to provide a kind of electrochemical method of simultaneously producing sodium chlorate and alkaline hydrogen peroxide at the deficiency of prior art, can improve the utilization efficiency of the two poles of electric current, reduce production cost.

For realizing such object, technical scheme of the present invention is:

(1) An electrolytic cell composed of an anode, a cation exchange membrane, an anion exchange membrane and a cathode is used, wherein the anode and the cation exchange membrane form an anode chamber, the cation exchange membrane and anion exchange membrane form an intermediate chamber, and the anion exchange membrane and the cathode form Cathode chamber; (2) sodium chloride and sodium chlorate solutions are passed through the anode chamber, sodium hydroxide solution and air are passed through the cathode chamber, sodium hydroxide solution is passed through the middle chamber, after direct current is passed between the electrodes, the anode generates chlorine gas, and the cathode oxygen is reduced to form Hydrogen peroxide, the concentration of sodium hydroxide solution in the middle chamber increases; (3) the anolyte flowing out from the anode chamber flows through an external heating reaction tank, and the chlorine gas is hydrolyzed to generate hypochlorous acid, and a homogeneous chemical reaction occurs to generate sodium chlorate, The anolyte is recycled back to the anode compartment of the electrolyzer. Part of the concentrated sodium hydroxide solution flowing out of the intermediate chamber can be used to adjust the pH of the anolyte.

The method of the present invention is specifically:

(1) adopt a kind of electrolyzer, this electrolyzer comprises anode, cation exchange membrane, anion exchange membrane and negative electrode, wherein anode and cation exchange membrane form anode chamber, cation exchange membrane and anion exchange membrane form intermediate chamber, anion exchange membrane and The cathode forms a cathode chamber.

(2) Feed the electrolyte into the anode chamber, cathode chamber and intermediate chamber respectively, wherein the concentration of sodium chloride in the anolyte is 0.1-5M, the concentration of sodium chlorate is 0-5M, and the anolyte stays once in the anode chamber The time is 10-100s; the cathode chamber is fed with sodium hydroxide solution and air, the concentration of sodium hydroxide solution is 0.1-5M, the residence time is 0.5-10min, and the residence time of air is 0.2-2s; the middle chamber is fed with 0.1-5M Sodium hydroxide solution, the residence time is 0.5-7min. The operating temperature of the electrolytic cell is 0-100°C, and a direct current with a current density of 0.1-6kA/m ² is passed through. The anode generates chlorine gas, the cathode oxygen is reduced to generate hydrogen peroxide, and the concentration of sodium hydroxide solution in the middle chamber increases.

(3) The anolyte flows through an external heated reaction tank, the chlorine gas is hydrolyzed to generate hypochlorous acid, and then a homogeneous chemical reaction occurs to generate sodium chlorate, after which the anolyte is circulated back to the anode chamber of the electrolytic cell. The pH of the circulating anolyte is controlled between 6-7 by dropwise addition of an acid, such as hypochlorous acid, or a suitable base, such as sodium hydroxide. The sodium hydroxide used to adjust the pH can be the concentrated sodium hydroxide solution from the electrolytic cell intermediate chamber.

The anode material in the present invention is a shape-stable electrode (DSA), including titanium-coated lead dioxide PbO ₂ /Ti, titanium-coated ruthenium Ru/Ti electrodes, and the like.

Cathode material among the present invention can select metals such as stainless steel plate, nickel plate, also can select carbon felt, graphite particle and graphite fiber etc., negative electrode among the present invention is preferably the composite graphite particle through carbon black/polytetrafluoroethylene coating.

The cation exchange membrane of the present invention can be selected from polyethylene cation exchange membrane, polyvinyl chloride type cation exchange membrane, polytetrafluoroethylene conductive cation exchange membrane or polysulfone sulfonic acid cation exchange membrane.

The anion exchange membrane of the present invention can be selected from polyethylene anion exchange membrane, butylbenzene quaternary ammonium anion exchange membrane, polysulfone anion exchange membrane or pyridinium quaternary ammonium anion exchange membrane and the like.

The electrochemical method of the present invention can simultaneously electrolyze and produce two useful chemicals—sodium chlorate and hydrogen peroxide, thereby improving the overall utilization efficiency of electric current and reducing production cost. In addition, the present invention adopts the sequential arrangement of the anode, cation exchange membrane, anion exchange membrane and cathode, so the concentrated sodium hydroxide solution flowing out from the intermediate chamber can be used to adjust the pH of the anolyte without using additional sodium hydroxide, so that Further reduce operating costs.

Description of drawings

Fig. 1 is the electrochemical method schematic diagram of electrolytic production sodium chlorate and alkaline hydrogen peroxide simultaneously of the present invention.

Detailed ways

The electrochemical method of the present invention will be further described below in conjunction with specific examples.

Fig. 1 has provided the electrochemical method test device and technological process of the present invention. As shown in Figure 1, a kind of electrolytic cell that the present invention adopts comprises anode, cation exchange membrane, anion exchange membrane and negative electrode, wherein anode and cation exchange membrane form anode chamber, cation exchange membrane and anion exchange membrane form intermediate chamber, anion exchange The membrane and the cathode form a cathode compartment. The anode chamber is fed with sodium chloride and sodium chlorate solutions, the cathode chamber is fed with sodium hydroxide solution and air, and the middle chamber is fed with sodium hydroxide solution.

When the electrolyzer is working, the hydroxide ions produced by electrolysis in the cathode chamber enter the intermediate chamber through the anion exchange membrane, and form sodium hydroxide with the sodium ions from the anolyte. The pH of the anolyte is adjusted by using the concentrated sodium hydroxide solution flowing out of the intermediate chamber, without using additional sodium hydroxide, thereby reducing the operating cost. The sodium hydroxide solution flows out of the middle chamber, part of which is used to adjust the pH of the anolyte, and part of which is returned to the original sodium hydroxide solution storage tank.

When the two ends of the electrodes are connected with direct current, hydrogen peroxide is produced at the cathode, chlorine gas is produced at the anode, and the chlorine gas is hydrolyzed to generate hypochlorous acid, and a homogeneous chemical reaction occurs in the external heating reaction tank to generate sodium chlorate. When the sodium chlorate in the anolyte reaches a certain concentration, part of the anolyte can be discharged and the sodium chloride solution added. Water can also be added or removed from the circulating anolyte to maintain water balance. In the present invention, the porous cathode can be electrolyzed in a trickle bed manner, and the sodium hydroxide solution and air pass through the cathode chamber in the same direction from top to bottom. The electrolyte in the anode chamber and the middle chamber flows in from bottom to top. Part of the sodium hydroxide solution flowing out of the intermediate chamber is used to adjust the pH of the anolyte, and part of it is returned to the storage tank of the original NaOH solution.

The feasibility of the electrochemical method of the present invention has been verified by experiments. Continuous electrochemical reaction process as shown in Figure 1, sodium hydroxide solution and air (catholyte) and sodium chloride solution (anolyte) are respectively pumped in the electrolytic cell of the present invention. The catholyte passes through the electrolyzer in a single pass. The anolyte is circulated back to the electrolytic cell after passing through the external heating reaction tank, and the heating reaction tank has a heater to control the temperature of the anolyte. The pH of the circulating anolyte is automatically controlled between 6 and 7 by dropping hypochlorous acid or sodium hydroxide, and the sodium hydroxide used to adjust the pH comes from the concentrated sodium hydroxide solution flowing out of the middle chamber of the electrolytic cell.

Example 1

The electrochemical process test device shown in Figure 1 was used to prepare alkaline hydrogen peroxide and sodium chlorate. The specific test conditions are as follows: the cathode material is carbon black/polytetrafluoroethylene coated composite graphite particles, the nickel cathode plate (80*70mm), the anode is a titanium-coated lead dioxide DSA electrode (80*70mm), and the apparent area of the electrode is 30cm ² , the anion exchange membrane is a polyethylene heterogeneous membrane, and the cation exchange membrane is a polyethylene heterogeneous membrane. The anolyte is 3.8M NaCl, and the residence time in the anode chamber is 21s; the catholyte is 2M NaOH, and the residence time is 7min; The concentration is 1M, and the residence time is 100s. The temperature of the anolyte in the electrolytic cell is 30°C and that of the catholyte is 35°C. When the current density is 1.2kA/m ² , the average terminal voltage is 4.3V. The temperature of the heating reaction tank is 70° C., the pH of the anolyte in the heating reaction tank is controlled at 6.5, and the volume of the anolyte in the heating reaction tank is 1 L. After electrolysis for 3 hours, the _{concentration} of _H2O2 was 0.161M, _NaClO3 was 0.04M, and the current efficiencies were 86.3% and 59.6%, respectively.

Example 2

The electrochemical process test device shown in Figure 1 was used to prepare alkaline hydrogen peroxide and sodium chlorate. The specific test conditions are as follows: the cathode material is carbon black/polytetrafluoroethylene coated composite graphite particles, the stainless steel cathode plate (80*70mm), the anode is a titanium-coated lead dioxide DSA electrode (80*70mm), and the apparent area of the electrode is 30cm ² , the anion exchange membrane is a polysulfone heterogeneous membrane, and the cation exchange membrane is a perfluorosulfonic acid membrane. The anolyte is 2.8M NaCl and 2.42M NaClO ₃ , and the residence time in the anode chamber is 8s; the catholyte is 2M NaOH, and the residence time is 84s. ; The concentration of NaOH solution in the middle chamber is 2M, and the residence time is 10s. The temperature of the anolyte in the electrolytic cell is 30°C and that of the catholyte is 35°C. When the current density is 1.2kA/m ² , the average terminal voltage is 4.1V. The temperature of the heating reaction tank is 70° C., the pH of the anolyte in the heating reaction tank is controlled at 6.5, and the volume of the anolyte in the heating reaction tank is 1 L. After 3 hours of electrolysis, the _{concentration} of _H2O2 was 0.036M, _NaClO3 increased to 2.47M, and the current efficiencies were 96.5% and 74.4%, respectively.

Example 3

The electrochemical process test device shown in Figure 1 was used to prepare alkaline hydrogen peroxide and sodium chlorate. The specific test conditions are as follows: the cathode material is carbon felt, the stainless steel cathode plate (80*70mm), the anode is a titanium Ru/Ti electrode coated with ruthenium (80*70mm), the apparent area of the electrode is 30cm ² , and the anion exchange membrane is polysulfone Phase membrane, cation exchange membrane is perfluorosulfonic acid membrane. The anolyte is 3.8M NaCl and 0.25M NaClO ₃ , and the residence time in the anode chamber is 42s; the catholyte is 4M NaOH, and the residence time is 42s. 0.2s; the concentration of NaOH solution in the middle chamber is 2M, and the residence time is 5s. The temperature of the anolyte in the electrolytic cell is 50°C, and that of the catholyte is 50°C. When the current density is 3kA/m ² , the average terminal voltage is 6V. The temperature of the heating reaction tank is 70°C, the pH of the anolyte in the heating reaction tank is controlled at 6.5, and the volume of the anolyte in the heating reaction tank is 2L. After 6 hours of electrolysis, the _{concentration} of _H2O2 was 0.037M and _NaClO3 increased to 0.37M, and the current efficiencies were 79.3% and 71.5%, respectively.

Example 4

Experiments were carried out using the electrochemical process shown in Figure 1 to prepare alkaline hydrogen peroxide and sodium chlorate. The specific test conditions are as follows: the cathode material is carbon felt, the stainless steel cathode plate (80*70mm), the anode is a titanium-coated ruthenium Ru/Ti electrode (80*70mm), the electrode surface area is 30cm ² , and the anion exchange membrane is butylbenzene quarter Ammonium membrane, cation exchange membrane is polysulfone sulfonic acid membrane. The anolyte is a mixed solution of 2.8M NaCl and 2.89M NaClO ₃ , and the residence time in the anode chamber is 14s; the catholyte is 1M NaOH, and the residence time is 42s. The time is 0.4s; the concentration of NaOH solution in the middle chamber is 2M, and the residence time is 5s. The temperature of the anolyte in the electrolytic cell is 30°C and that of the catholyte is 35°C. When the current density is 2.4kA/m ² , the average terminal voltage is 5.7V. The temperature of the heating reaction tank is 70° C., the pH of the anolyte in the heating reaction tank is controlled at 6.5, and the volume of the anolyte in the heating reaction tank is 1 L. After 3 hours of electrolysis, the _{concentration} of _H2O2 was 0.295M and _NaClO3 increased to 3.00M, and the current efficiencies were 79.1% and 81.9%, respectively.

Claims (5)

1, an electrochemical method for producing sodium chlorate and alkaline hydrogen peroxide simultaneously, is characterized in that comprising the steps: (1) An electrolytic cell composed of an anode, a cation exchange membrane, an anion exchange membrane and a cathode is adopted, wherein the anode and the cation exchange membrane form an anode chamber, the cation exchange membrane and anion exchange membrane form an intermediate chamber, and the anion exchange membrane forms a cathode cathode chamber; (2) Feed the electrolyte to the anode chamber, cathode chamber and intermediate chamber respectively; wherein, the concentration of sodium chloride in the anolyte is 0.1-5M, the concentration of sodium chlorate is 0-5M, and the anolyte stops once in the anode chamber The time is 10-100s; the cathode chamber is fed with sodium hydroxide solution and air, the concentration of sodium hydroxide solution is 0.1-5M, the residence time is 0.5-10min, and the residence time of air is 0.2-2s; the middle chamber is fed with 0.1-5M Sodium hydroxide solution, the residence time is 0.5-7min; the operating temperature of the electrolytic cell is 0-100°C, the current density is 0.1-6kA/m ² direct current, the anode generates chlorine gas, and the cathode oxygen is reduced to generate hydrogen peroxide. The concentration of sodium hydroxide solution in the chamber increases; (3) The anolyte flows through an external heating reaction tank, the chlorine gas is hydrolyzed to generate hypochlorous acid, and a homogeneous chemical reaction occurs to generate sodium chlorate, and the anolyte is circulated back to the anode chamber of the electrolytic cell; the cycle is regulated by adding acid or alkali dropwise The pH of the anolyte is between 6-7. 2, according to the electrochemical method of producing sodium chlorate and alkaline hydrogen peroxide simultaneously of claim 1, it is characterized in that the acid that the pH that regulates and controls circulation anolyte adopts is hypochlorous acid, and the alkali that adopts is to come from the electrolytic cell intermediate chamber Outflow of concentrated sodium hydroxide solution. 3, according to the electrochemical method of producing sodium chlorate and alkaline hydrogen peroxide simultaneously according to claim 1, it is characterized in that the material of described anode is that titanium is coated with lead dioxide or titanium is coated with ruthenium, and the material of described cathode is selected stainless steel plate , nickel plate, carbon felt, graphite particles, graphite fibers, or composite graphite particles coated with carbon black or PTFE. 4, according to the electrochemical method of producing sodium chlorate and alkaline hydrogen peroxide simultaneously according to claim 1, it is characterized in that described cation-exchange membrane selects polyethylene cation-exchange membrane, polyvinyl chloride type cation-exchange membrane, polytetrafluoroethylene Conductive cation exchange membrane or polysulfone sulfonic acid cation exchange membrane. 5. According to the electrochemical method of producing sodium chlorate and alkaline hydrogen peroxide simultaneously according to claim 1, it is characterized in that said anion-exchange membrane is selected polyethylene anion-exchange membrane, butylbenzene quaternary ammonium anion-exchange membrane, polysulfone anion-exchange membrane membrane or pyridinium quaternary ammonium anion exchange membrane.

Images