Can Telluric Acid Replace Chromate as a Homogeneous Catalyst in the Chlorate Process?

Finding an alternative to Cr(VI) as catalyst for the conversion of hypochlorite/hypochlorous acid to chlorate is of critical importance to render the industrial chlorate process safe and sustainable. Recently, telluric acid was identified as a potential replacement but its performance under industrial conditions and its interactions with other parts of the process are still unknown. These factors are elucidated by a combination of density functional theory (DFT) modeling and pilot plant studies. Our results indicate, that the addition of telluric acid indeed has a beneficial effect on the decomposition of HOCl to chlorate. The increased performance, shown as a decreased oxygen formation and an increase in anodic current efficiency. It is mostly related to a buffering effect and an increased selectivity for chlorate formation. Unfortunately, a low cathodic current efficiency was achieved due to reduction of telluric acid to solid Te/TeO2 particles in the electrolyte and at the cathode. Despite the benefits of buffering effects and increased selectivity for chlorate formation, telluric acid is unsuitable as replacement for Cr(VI) in the chlorate process due to lack of compatibility with all process conditions. Replacing Substances of Very High Concern without compromising other environmental targets is an intriguing challenge. In this study we explore the possibility to replace toxic Cr(VI) with Telluric acid as catalyst in the energy intense production of sodium chlorate.image