SU1254061A1 - Method of producing chlorine - Google Patents

Description

The invention relates to technological-1-ht electrochemical production, specifically to the production of chlorine, for example, to the processes of obtaining chlorine and caustic soda according to diaphragmatic y or membrane methods.

The aim of the invention is to increase the corrosion resistance of metallo oxide anodes, especially when the chloride content in the anolyte is reduced,

Example 1. Oxide ruthenium titanium anode (ORTA) with an active coating on 30 mol LOOg and 70 koi.% TiO, deposited on titanium by thermal decomposition of salts, is irradiated in a sludge jpeaKTOpe neutron flux / cm / s for 200 h. Such an electrode is placed into an electrochemical cell of a flow type, in which the cathode and anode spaces are additionally separated by an ion exchange membrane to eliminate any possibility of catholyte getting into the anode space of the cell and changing the pH of the solution as a result The test vessel is continuously fed with a constant Scotblo (80 ml / h) test solution. The resulting anolyte collects and its radioactivity is periodically measured. The solution’s radioactivity from the solution is also measured separately: filled with concentrated hydrochloric acid in which the absorption of ruthenium, carried out by the cell together with chlorine in the form of RuCif, was carried out. All values of the reduced ORTA corrosion rates reflect the total loss of ruthenium from the electrode and are expressed in.

The crown of the cell is periodically yutter. gas samples :: romatographically determine their content

oxygen. These values are expressed as: E volume percent, -Periodically controlled :: / ptyal electrode and pH of the solution (.m, table experience 5).

The harzk-black nature of the behavior of ORTA during anodic polarization in chloride solutions is the slowness of the establishment of a steady state (steady-state velocity

corrosion). A steady-state corrosion rate is not immediately established when replacing the initial NaCl solution with an appropriate solution containing an additive. Therefore every

the experiment is carried out as follows. Initially, the electrode is put into a stationary state by polarizing it in the KaCl solution under study at a current density of 0.2 A / cm and

A temperature of 87 for approximately 300 hours is measured by a steady-state corrosion rate and oxygen content in chlorine. Then, without interrupting the field, the electrolyte in the cell is replaced with an NaCl solution containing the corresponding amount of phosphate, in which the electrode also withstands i less than 100 hours. After that,

with a higher concentration of phosphate 1-s. T. — How to conduct experiments with a garayp uet measurement of a sta1, akvravnyh: a real sign of corrosion corrosion, the oxygen content of chlorine and the potential of the electrode. The results of such measurements are presented in the table. Wellchms aE reflects an increase in the potential of the electrode with an increase in the concentration of Na-jPO in the anolyte compared with that of Had without phosphate. In those cases when the Velcch Sha deE did not exceed 15 mV, it is not listed in the table.

As can be seen from tablets, at all concentrations of NaCl and the anolyte pH studied, the introduction of phosphate ions (PO) into the anolyte at a concentration of 0.06 - 2.0 leads to a decrease in the corrosion rate of ORTA. The inhibitory effect of phosphate is the stronger, the lower the concentration of NaCl in the anolyte. As a result, if with a decrease in the concentration of NaCl in the initial phosphate-free solution from 300 to 50 g / l, the corrosion rate of ORTA increases by about 4 times (see table, experiments i and 6 without phosphate), then a similar change in the concentration of NaCl in the presence of 0.17 g / l PC does not cause an increase in the ORTA corrosion rate (see table, experiments 1 and & without a PO concentration of 0.18 g / l). As a result, in the solution of NaCl 50 g / l + 0.18 g / l of PO, the corrosion rate of ORTA was almost the same as in the solution of NaCl 300 g / l, which does not contain phosphates (see table, experiment 6 with P04 0 concentration 18 g / l and experience 1 without phosphate). From the point of view of the rate of corrosion of the oxygen content in chlorine and the electrode potential, the optimal concentration of PO in brine is a concentration of 0.6 g / l. At a PO concentration in the solution below 0.06 g / l, the phosphates do not affect the processes occurring at the electrode. An increase in the concentration of phosphate ions above 2.0 g / l leads to an increase in the oxygen content in chlorine and the potential of the electrode. The rate of corrosion of ORTA also increases gradually (see table, experiment 1 and 2).

Example 2. Measurements analogous to example 1 are also carried out in NaCl solutions, into which at the same time sulfate and phosphate ions are introduced at a concentration of 1-W and 0.18-- 2.0 g / l, respectively. With the simultaneous introduction of phosphate and sulfate ions into chloride solutions, a decrease in the ORTA corrosion rate and the chlorine oxygen content is observed. For example, in a solution of NaCl 150 g / l with

by the simultaneous introduction of 10 g / l of S04 and only 0.18 g / l of POvj ions, the corrosion rate decreases by about 2 times (from 210 to 910 g / cm h), and the oxygen content in chlorine decreases from 1.4 to 1, 0%. Thus, if the presence of sulfate ions in chloride solutions at a concentration of 10 g / l leads to an increase in oxygen content in the chlorine and an anode growth rate (C) under certain conditions, then with the simultaneous introduction of phosphate and sulfate into chloride solutions. ion decreases corrosion rate and oxygen content in chlorine.,

The results show that the introduction of phosphate to sulfate ions in chloride solutions is particularly useful when electrolyzing chloride solutions with a low concentration of NaCl.

The introduction of phosphates into the anolyte during chlorine electrolysis using membrane and diaphragm methods may allow the production of NaCl from electrolyte entering electrolysis much more completely, which makes it possible in principle to significantly reduce the amount of treatment plants for brine preparation. This is particularly economically feasible in the case of membrane electrolysis, taking into account the high requirements for brine cleaning. Reducing the concentration of NaCl from 300 to 150 g / l leads to a decrease in the conductivity of the electrolyte by about 2 times. However, in the case of membrane electrolysis, this will not cause a significant increase in the voltage on the bath, due to the small distance between the membrane and the anode. At the same time, the resistance of the membrane itself does not increase and the water transfer from the anode to the cathode will increase, which will reduce the flow of water needed to make up the cathode space of the electrolyzer, and will further increase the completeness of the use of brine supplied to the electrolysis

Claims (2)

I. METHOD FOR PRODUCING CHLORINE and chlorine-oxygen compounds by electrolysis of an aqueous solution of alkali metal chloride using an oxide-metal anode, characterized in that, in order to increase the stability of the anode, phosphate ions are introduced into it in an amount of 0.06-2.0 g / l . 2. The method according to claim 1, about l and h, and with the fact that sulfate ions are additionally introduced into the solution in an amount of 1-10 g / l. 12540 Od>