High Current Density Chlorate Cell Using Platinized Anodes

Abstract

Sodium chlorate was produced in a monopolar cell having platinized titanium anodes and steel cathodes. A high current density was used in order to minimize cell costs. A 144‐amp cell was built and tested in a continuous experiment for 31 days. The energy requirements were 6300 kwhr d.c./ton NaClO3 . The replacement platinum which may not have been optimized was shown as 5.3 normalg/ton NaClO3 . The cell operated at 1 amp/in.2, and 110°C. The cell feed contained approximately 190g normalNaCl and 330g NaClO3 per liter. Cell effluent contained 11Og normalNaCl and 580g NaClO3 per liter. The average cell voltage was 3.7. The pH was 6.7. This process is the subject of U.S. Patent 3,043,757. A cell with variable electrode spacings and height was used to indicate that ⅛ in. spacing would be preferred with electrodes 3 ft high in the commercial cell design.

Chlorine Oxides and Chlorine Oxygen Acids

“…Chlorate cell design has changed much within the last 25 years by the introduction of coated titanium anodes [179] and by the systematic application of the results of chlorate formation theory. Hypochlorite autoxidation occurs at high temperature outside the interelectrode gap or even outside the electrochemical reactor to decrease the hypochlorite concentration before the electrolyte reenters the cell.…”

Anodic chlorate formation on platinized titanium

“…Platinized titanium anodes are of technological interest in chlorate electrolysis [1,2] because of their corrosion resistivity which allows for cells to be operated at higher temperatures than with graphite anodes. In chlorate electrolysis this is of particular importance since the rate of chemical chlorate formation by disproportionation of hypochlorite (Equation 1) increases faster with temperature than that of the anodic loss reaction (Equation 2) which is generally believed to be mass transfer controlled under technical electrolysis conditions [4][5][6][7][8][9].…”

“…60CI-+ 3H20--*2C10 ~ +4CI-+6H + + 3/2 02 + 6e (2) The maximum current efficiency in a chlorate cell when all chlorate is formed according to Equation (2) is 66"7~o, while it is 100~o when all chlorate is formed according to Equation (1). The rate of anodic chlorate formation (Equation 2) has been studied previously by the authors on graphite electrodes [8,9] under conditions where reaction (1) was negligible.…”