Scientists have developed a catalyst that can turn carbon dioxide into acetic acid, a valuable industrial chemical and food additive.
The Australian, U.S., and Japanese researchers published their findings in Nature Communications, claiming that their method points to a scalable way to transform carbon dioxide emissions into useful materials.
Global demand for acetic acid is around 6.5 million tons each year. It is used to make various products such as pharmaceuticals, textiles, and cosmetics.
Acetic acid is also a major component of vinegar and a popular food preservative.
In the food industry, acetic acid is mostly produced by fermenting, but it’s made from fossil fuels in other industries, which produces greenhouse gas emissions during processing. Also, the production process typically requires expensive precious metals like cobalt, iridium, and rhodium.
Now researchers have discovered a way to make acetic acid from carbon dioxide and hydrogen, using iron as a catalyst.
The iron catalyst remains solid throughout the entire reaction, meaning the process doesn’t require additional equipment or energy to purify the acetic acid once it’s made.
“From theory, we knew iron should be a good candidate for catalyzing this reaction, but the challenge is to keep it stable under acidic water conditions,” said Akshat Tanksale, associate professor at Monash University.
Making acetic acid creates acid dissolved in water, while iron tends to rust in water.
The researchers used a metal-organic framework (MOF) as their solution. This substance consists of metallic atoms (in this case, iron) linked with carbon-based bridges, creating a sponge-like structure with molecule-sized holes in it.
Then the researchers heat the MOF, making some of iron atoms merge and form particles with a few nanometres in size. These particles were then embedded within a porous layer of carbon.
The resulting catalyst produced acetic acid (CH3COOH) from CO2 and hydrogen (H2) very efficiently.
Tanksale said this experiment took his team more than a year to develop this catalyst, with a trial-and-error process.
The researchers are in the process of commercializing the catalyst, which is more cost-effective than the currently used ones.
Tanksale says that the main challenge is not the catalyst itself but the availability and cost of the feedstocks: CO2 and hydrogen.
"While these feedstocks are readily available, their cost is considerably higher when derived from green sources," Tanksale says.
“To reap the true benefits of our technology, i.e. to achieve negative carbon emissions, carbon dioxide must be captured from air, and hydrogen must be made from water using renewable energy,” he added.