‘At some point we’re going to have to decarbonise all the elements of chemical industry […]’
Researchers from Northwestern University, Illinois, US, working with international collaborators, have developed a process for producing acetic acid based on carbon monoxide derived from captured carbon. The process involves a novel catalyst developed at Northwestern University. The work has been published in the journal Nature.
The researchers point out that while acetic acid for human consumption is produced via fermentation, 90% of the acetic acid market is for feedstock in the production of paints, coatings and adhesives, among other things. This acetic acid is derived primarily from methanol. A life cycle assessment showed the research team that for every kilogram of acetic acid produced from methanol, 1.6 kg of carbon dioxide is released.
The novel route developed by the research team takes captured carbon dioxide which is passed through an electrolyser to form carbon monoxide. This is then passed through a second electrolyser, where a novel catalyst containing just 1% copper, much lower than in traditional catalysts, favours the production of acetic acid. Efficiency was also improved by taking the reactor pressure up to 10 atmospheres.
‘A major challenge that we face is selectivity,’ said Josh Wicks, one of the paper’s four co-lead authors. ‘Most of the catalysts used for the second step facilitate multiple simultaneous reactions, which leads to a mix of different two-carbon products that can be hard to separate and purify. What we tried to do here was set up conditions that favour one product above all others.’ The researchers also reported that the new catalyst to be ‘relatively stable.’
‘Carbon capture is feasible today from a technical point of view, but not yet from an economic point of view,’ said Professor Ted Sargent, Department of Chemistry Northwestern University. ‘By using electrochemistry to convert captured carbon into products with established markets, we provide new pathways to improving these economics, as well as a more sustainable source for the industrial chemicals that we still need.’
Wicks added: ‘At some point we’re going to have to decarbonise all the elements of the chemical industry, so the more different pathways we have to useful products, whether it's ethanol, propylene or acetic acid, the better.’