SU1468970A1 - Electrode for electrochemical production of chlorine and alkali - Google Patents

Description

one

The invention relates to electrochemical production, in particular to electrodes for electrochemical processes, in particular for the production of chlorine and alkali.

A electrode for electrochemical processes is known, containing an electrically conductive base made of tantalum titanium, on which an active coating is applied, consisting of a metal oxide of a platinum group and a mixture of metal oxides containing a oxide of titanium or tantalum and at least one more oxide of the alloying metal selected from Groups: tin, silver, chromium, lanthanum, aluminum, cobalt, antimony, molybdenum, nickel, iron, tungsten, vanadium, phosphorus, boron, beryllium, sodium, calcium, strontium, lead, copper and bismuth. The oxide of the alloying metal is taken in an amount of 0.1-50% by weight of titanium dioxide or tantalum pentoxide. The ratio of the platinum group metal content to the rest of the oxide coating metals is 20: 100-85: 100. For the case when the active mass of the known electrode contains TiOj ,, RuO, and SnO, the ratio of these components will correspond, mol%: TiO 40-90; SnOg 0.25-25; RuO 9.75-35. Known electrode of the following composition, mol.%: RuO 21,8; TiO 72.7; SnOj, 5.5, after 1500 hours of tests in a concentrated solution of NaCl at 2 A / cm and 60 ° C, had an anodic potential of 1.42 V. Under the conditions of the tests according to the method of variable polarity (five anodic and five cathodic polarizations at 1 A / cm (within two minutes each polarization) the specified electrode has a weight loss of 0.09 mg / cm after two test cycles and a weight loss

0

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with

v |

31А6

after one dive

0.01 mg / cm to amalgam.

The disadvantage of this electrode is the low resistance of the electrode and the high overvoltage of chlorine, equal to about 2 A / cm 140 mV.

The closest to the proposed technical essence and the achievable result is an electrode for electrochemical production of chlorine and alkali, containing a base of a valve metal coated with an active coating of a mixture of oxides of tin, ruthenium and titanium, and the molar ratio of TiO .: () is in the range of 1.5-2.5: 1, and the content of SnOz is 35-50 mol.%

in a mixture of BpOg + KI.

The known electrode has an active coating composition in the range, mol%: TiO 60-75; SnO 10-20; 15-30.

The known electrode with the active coating of the composition: () 2.2: 1 (in molar fractions) and at 40 mol.% ZnOg in the mixture RuO ,, + SnO, i.e. the active mass has a composition, mol.%: TiOj 67; SnO. 13.2; RuO 19.8 and, under chlorine electrolysis conditions, has a loss of ruthenium from the active mass of 0.01 g per ton of chlorine. The deposition of chlorine at the known electrode is reduced by 40 mV relative to the electrode that does not contain SnOj in the active coating.

The known electrode is characterized by insufficient durability and relatively high overpotential release of chlorine, which leads to an increase in energy consumption per process.

The purpose of the invention is to increase the durability of the electrode and reduce the energy consumption for the process by reducing the overvoltage of chlorine emissions.

The goal is achieved by an electrode for the electrochemical production of chlorine and alkali, containing a base of a valve metal with a deposited 1–1 m on it of an active coating of a mixture of tin oxides, ruthenium and titanium, the ingredients taken in the following ratio, mol%: Ruthenium dioxide 15 -thirty

Titanium dioxide 25-55

Tin dioxide30-60

The proposed electrode has a higher content of tin dioxide relative to the known electrode (1.55%).

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five

ABOUT

3.0 times over). An increase in the relative fraction of tin dioxide in the active coating unexpectedly leads to a dramatic improvement in the electrochemical characteristics of the electrode and to its stability during electrolysis.

Example. A coating solution — a mixed aqueous-alcoholic solution of SnClj, TiCl and RuOHCl — is applied to the titanium electrode base, which has previously undergone sandblasting, degreasing, and etching. The coating solution is prepared from stock solutions: a solution of ruthenium hydroxychloride (RuOHCl) in water at a concentration of 150 g / l; a solution of titanium tetrachloride (TiCl) in water with a concentration of 220 g / l (in terms of TiO,); a solution of tin dichloride (SnCl) in water with a concentration of 500 g / l.

All three of the original solution when stored in a sealed container have unlimited stability, the mixed solution has a stability of 10-20 days.

The active coating of the electrode is made multi-layered. Each layer is deposited according to the same technology: the mixed solution consumption per 1 layer is 30 ml / m, which corresponds to a ruthenium pad of 1.35 g / m, after applying each subsequent electrode layer, first cyuiaT at 150 ° C, then burn at 5 for 20 minutes , last

the layer is calcined at 450 ° C for 40 minutes.

A total of 9 electrodes were manufactured and tested.

The potential of the anode was measured under conditions of chlorine diaphragm electrolysis: the concentration of sodium chloride in the anolyte was 280 g / l, the current density was 1000, 3000, 10,000 A / m, 5 and the temperature 80 ° g :.

The resistance of the electrodes was estimated. J by the method of variable polarity and amalgamation, as well as by the radioactive method.

The measurement results are presented in Table. one.

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The composition of the anode gas for all electrodes was determined under the following electrolysis conditions: the concentration of sodium chloride in the anolyte was 280 g / l, the current density was 2000 A / m, the temperature was 80 C. The results obtained are presented in Table. 2

For comparison, table. 2 and shows the performance of the electrode, not containing in the composition of the active mass of tin dioxide - 33 mol.% RuO and 67 mol.% TiO (ORTA electrode).

As can be seen from. the results given in table. 1 and 2, the proposed electrode has a lower ruthenium consumption, measured by the radioactive method, by 20% AO relative to the known electrode, as well as by the accelerated test method of variable polarity and amalgamation.

The actual consumption of ruthenium per 1 ton of chlorine obtained according to the results of measurements by a radioactivity method and according to the results of experimental tests is 0.006-0.008 g, while the known electrode has a ruthenium consumption of 0.01 g per 1 ton of chlorine obtained.

The proposed electrode also provides a reduction in the oxygen content in chlorine relative to the known electrode by 15-20%.

TiOj -67 55 Potential of the anode at the current density; A / m

10001,311.31

3,001.34 1.33

100001.40 1.36

B (relative NVE) Electrode resistance by the method of variable polarity and amalgamation, mg / cm 0.20.07 Electrode resistance by the radioactivity method, g / c

1.30 1.33 ", 35

1.30 1.33, 35

1.31 1.33 1.36

1.30 1.32 1.35

1.32 1.35 1.40

1.31 1.35 1.39

1.32 1.34 1.38

0.06 0.070.07

0.05

0.5

0.140.16

Todu, Mr. / Sn .., ".

(at 2 A / cm) 3.8 10 2.2-U 2.1-10 2.0-10-10 1.9-1 (G 1.6-1 (G 3.0-1 (G 2.7.10 2, 6-10

1.30 1.32 1.35

1.32 1.35 1.40

1.31 1.35 1.39

1.32 1.34 1.38

0.05

0.5

0.140.16

table 2

Claims (1)

ELECTRODE FOR ELECTROCHEMICAL PRODUCTION OF CHLORINE AND ALKALI, containing a valve metal base with an active coating of a mixture of oxides of ruthenium, titanium and tin, characterized in that, in order to increase the resistance of the electrode and reduce energy costs for the process by reducing overvoltage chlorine evolution, the active coating of the electrode contains the indicated oxides in the following ratio, mol.%: Ruthenium Dioxide Titanium Dioxide Tin Dioxide 15-30 25-55 30-60