Method for production of electrolytic manganese dioxide

 

(57) Abstract:

The invention relates to inorganic chemistry and can be used in particular for the preparation of the catalyst used for purification of gas mixtures of carbon monoxide in the systems of collective and individual protection of respiratory organs in the emissions of industrial enterprises, for purification of exhaust gases of internal combustion engines, as well as for other industrial and environmental purposes. Method for production of electrolytic manganese dioxide involves the electrolysis of a solution containing 250 - 280 g/l manganese sulfate and 150 - 200 g/l free sulphuric acid, when the current density at the anode 500 - 600 a/m2by switching the polarity of the electrodes at 0.5 - 1.5 h intervals equal to 5 to 9 p.m Method allows to obtain electrolytic manganese dioxide with catalytic activity, superior known in the oxidation of carbon monoxide. table 1.

The invention relates to the field of inorganic chemistry and can be used in particular for the preparation of the catalyst used for purification of gas mixtures of carbon monoxide in the systems of collective and individual protection of respiratory organs and the emissions of the industry is in General and environmental objectives.

The known method for production of electrolytic manganese dioxide comprising the electrolysis of a solution containing manganese sulfate in the amount of 1-2 mol/l of free sulfuric acid in the amount of 0.25 to 1.0 mol/L. Electrolysis is carried out at a current density of 100500/m2and a temperature of 95oC with periodic switching the polarity of the electrodes (U.S. Pat. PCT WO N 79/00258 from 02.11.77,, CL C 25 B 1/00, C 01 G 45/02, H 01 M 4/50).

The disadvantage of this method is the low catalytic activity of the obtained electrolytic manganese dioxide in the oxidation of carbon monoxide.

Closest to the proposed technical substance and the number of matching characteristics is a method for electrolytic manganese dioxide comprising the electrolysis of a solution containing manganese sulfate in the amount of 100 g/l free sulfuric acid in the amount of 20 g/L. Electrolysis is carried out at a current density of 1 a/m2and a temperature of 95oC with periodic switching the polarity of the electrodes after 10 or more hours (A. C. USSR N 168658 from 03.04.62,, CL C 25 B 1/00).

The disadvantage of this method is the low catalytic activity of the obtained electrolytic manganese dioxide in the oxidation accesskey activity electrolytic manganese dioxide in the oxidation of carbon monoxide, what is achieved by the proposed method, including the electrolysis of a solution containing manganese sulfate and free sulfuric acid, periodic reversal of the polarity of the electrodes.

The difference of the proposed method against known is that during the electrolysis switching the polarity of the electrodes produce 0.5-1.5 hours every 5-9 hours.

Of scientific and technical literature authors unknown process operation of conducting electrolysis of a solution containing manganese sulfate and free sulfuric acid in the periodic switching of electrodes in 0.5 to 1.5 hours every 5-9 hours during the electrolysis.

The method is as follows.

Prepare the electrolyte solution containing 250-280 g/l manganese sulfate and 150-200 g/l free sulfuric acid. The electrolyte is poured into the cell, lined with vinyl liner, install the electrodes, made of sheet lead of high purity, and a water cooling unit, representing a coil of lead pipe. The electrolysis is carried out at current density at the anode 500-600 a/m2producing during the electrolysis PE trout, washed from sulfate ions with hot water at a temperature of 60-80oC, dried to a moisture content of not more than 20%, pressed at a pressure of 100 to 150 ATM., crushed, sieved fraction of 0.5-1.0 mm and dried at a temperature of 150-180oC for 3-4 hours. The catalytic activity obtained by the proposed method of electrolytic manganese dioxide in the oxidation of carbon monoxide was 6.3 to 7.2; catalytic activity obtained according to the method of electrolytic manganese dioxide in the oxidation of carbon monoxide was 0.8 to 1.5.

Example 1.

In a lined vinyl plastic electrolyzer containing 250 g/l manganese sulfate and 170 g/l of free sulfuric acid, establish the electrodes, made of sheet lead of high purity, and a water cooling unit, representing a coil of lead pipe. The electrolysis is carried out at current density at the anode 500 a/m2producing during the electrolysis switching the polarity of the electrodes at 0.5 hours every 5 hours. The precipitate of manganese dioxide was filtered, washed from sulfate ions with hot water at a temperature of 60oC, dried to a moisture content of not more than 20%, pressed at a pressure of 100 ATM., crushed, Otsego electrolytic manganese dioxide in the oxidation of carbon monoxide was 7.0.

Example 2.

A process as in example 1, except for the time interval produced by switching the polarity of the electrodes constituting 9 hours. The catalytic activity of the obtained electrolytic manganese dioxide in the oxidation of carbon monoxide was 6.7.

Example 3.

A process as in example 1, except for the interval of time for which switch the polarity of the electrodes, which is about 1.5 hours. The catalytic activity of the obtained electrolytic manganese dioxide in the oxidation of carbon monoxide was 6.4.

Example 4.

A process as in example 3, except for the time interval produced by switching the polarity of the electrodes constituting 9 hours. The catalytic activity of the obtained electrolytic manganese dioxide in the oxidation of carbon monoxide was 7.1.

The study of the influence of the magnitude of the time intervals at which and through which produce switching the polarity of the electrodes on the catalytic activity of the obtained electrolytic manganese dioxide in the oxidation of carbon monoxide in the table.

As with the ski manganese dioxide obtained by electrolysis of a solution containing manganese sulfate and free sulfuric acid, by switching the polarity of the electrodes during electrolysis in 0.5 to 1.5 hours every 5-9 hours.

With increasing time interval produced by switching the polarity of the electrodes, more than 9 hours of catalytic activity is markedly reduced. Reducing the time interval produced by switching the polarity of the electrodes is less than 5 hours leads to an increase in the duration of the electrolysis process. Reducing the interval of time for which switch the polarity of the electrodes is less than 0.5 hours leads to a decrease of catalytic activity of manganese dioxide in the oxidation of carbon monoxide. The increase in the interval of time for which switch the polarity of the electrodes, more than 1.5 hours does not lead to any noticeable changes in catalytic activity.

The increase of catalytic activity of electrolytic manganese dioxide obtained by electrolysis of a solution containing manganese sulfate and free sulfuric acid, by switching the polarity of the electrodes in 0.5 to 1.5 hours every 5-9 hours during the performance of the manganese sulfate and free sulfuric acid, at the anode is formed of manganese dioxide, which is deposited on the surface of the anode, through some time off from the surface and collects in the bottom of the cell. Until detachment from the surface of the anode particles formed of manganese dioxide act as crystallization centers, their sizes increase during the electrolysis process. In the case of switching the polarity of the electrodes and the formation of manganese dioxide starts to go on a clean electrode surface, which played the first role of the cathode, the surface of the electrode, which played the first role of the anode is cleared due to a change in current direction and the particles of manganese dioxide deposited on the bottom of the pot, without a significant increase in size. And since the catalytic activity of the manganese dioxide in the oxidation of carbon monoxide in large measure to the dispersion of the particles (the smaller the particle size is larger specific surface area is more active sites available for the molecules of the substrate), then in this case would be the formation of a fine product with a developed specific surface, which leads, ultimately, to improve catalytic activity.

With increasing time interval to the NCA is markedly reduced due to the formation of particles of relatively large size, having, respectively, an underdeveloped specific surface. The decrease in the magnitude of the time interval produced by switching the polarity of the electrodes is less than 5 hours leads to an increase in the duration of the electrolysis process and this is probably due to the fact that the reaction of the electrolytic production of manganese dioxide is due to the formation of kinetically significant intermediate products for quite a long induction period, during which there is an accumulation, resulting in the speed of the reaction is negligible. The increase in the duration of the electrolysis process is not economically feasible, since it leads to increased energy consumption and increase in the cost of industrial production.

Reducing the interval of time for which switch the polarity of the electrodes is less than 0.5 hours leads to a decrease of catalytic activity of manganese dioxide in the oxidation of carbon monoxide, since, apparently, for such a short time the surface of the electrode, which played the first role of the anode, no time to be cleaned from particles of manganese dioxide, which continue to serve as centers of crystallization, and the lytic activity. The increase in the interval of time for which switch the polarity of the electrodes, more than 1.5 hours does not lead to any noticeable changes in the catalytic activity of manganese dioxide in the oxidation of carbon monoxide.

Thus, the proposed method allows to obtain highly dispersed active electrolytic manganese dioxide, far beyond the known oxidation of carbon monoxide.

Implementation of the proposed method will allow on the basis of the obtained electrolytic manganese dioxide to prepare a highly effective catalyst used for purification of gas mixtures of carbon monoxide in the systems of collective and individual protection of respiratory organs and the emissions of industrial enterprises, for purification of exhaust gases of internal combustion engines, as well as for other industrial and environmental objectives that will provide an opportunity to effectively solve a wide range of environmental and technological problems.

From the above it follows that each of the signs stated together to a greater or lesser extent affect the solution of the problem, namely the increase of catalytic activity of manganese dioxide in the oxidation of Oia.

Method for production of electrolytic manganese dioxide comprising the electrolysis of a solution containing manganese sulfate and free sulfuric acid, periodic reversal of the polarity of the electrodes, characterized in that during the electrolysis switching the polarity of the electrodes produce 0.5 - 1.5 h every 5 - 9 PM

 

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3,5 4,5 and deposition of manganese ore containing manganese dioxide

FIELD: metallurgy.

SUBSTANCE: manganese dioxide obtaining method involves dilution of manganese-containing raw material in nitric acid so that solution of manganese nitrates and nitrates of calcium, potassium, magnesium and sodium impurities contained in the ore is obtained. Then, thermal decomposition of nitrates in autoclave is performed. Thermal decomposition is performed at constant pressure drop in autoclave, starting from pressure of 0.6 MPa and reducing it to the end of the process to 0.15 MPa. At that, pulp is constantly mixed at thermal decomposition with the mixer rotating at speed of 1-15 rpm and with superimposition of vibration on it with frequency of 20-50 Hz. Method can be implemented at chemical plants provided with pressure autoclaves.

EFFECT: obtaining manganese dioxide of improved quality.

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