AkzoNobel Specialty Chemicals is one of the major producers of sodium chlorate. Sodium chlorate is a stable and safe precursor for chlorine dioxide, used in Elemental Chlorine Free (ECF) bleaching of pulp. Bleached pulp is used for the production of paper, cardboard, and many other kinds of cellulose-based materials.
Since its invention, we have taken a leading role in optimizing the chlorate manufacturing process through our own research and through collaborations with universities and other partners. Despite making significant improvements over the years, even state-of-the-art chlorate manufacturing processes still rely on a key invention dating back to 1897 which is based on an additive of concern. We want to take the sustainability of this process to the next level and are looking for new methods which are more energy efficient and free of materials of concern.
Sodium chlorate is produced using electrochemical reactions, generally relying on small amounts of hexavalent Chromium (Cr(VI)) to make the process efficient. Cr(VI) has several roles in the process, for example making the cathode selective to the desired reactions and hindering the reduction of hypochlorite and chlorate, a side reaction that undermines the process. However, Cr(VI) has several health and environment related concerns, so we are looking for a process to make sodium chlorate without using any Cr(VI). A combination of solutions may be needed to provide a performance-competitive alternative.
Our current processes rely on a concentrated, warm, and very corrosive electrolyte, so requirements on materials used for equipment are very high. Also, electrical energy accounts for a major part of the cost for an electrolysis process, which puts high demands on energy efficiency.
We would consider any solution to make sodium chlorate without the need for Cr(VI). Of course we prefer bolt-on solutions that can be implemented within our current process, but even novel process designs are not out of consideration. A major requirement is energy efficiency and process safety. We have two possible avenues to a solution in mind:
Our scope is very broad, but any solution cannot contain materials of concern (like carcinogenic, mutagenic, or reprotoxic chemicals), and it should not result in a process with poor safety performance, poor energy efficiency, or create any major waste streams.
If you think you can help us produce chlorate in a sustainable, energy efficient way, we welcome you to join our Challenge on our Imagine Chemistry Challenge platform - open from January 10 - for open and collaborative innovation.
A review of chromium(VI) use in chlorate electrolysis: Functions, challenges and suggested alternatives. Balázs Endrodi, Nina Simic, Mats Wildlock, Ann Cornell. Electrochimica Acta 234 (2017) 108–122.