Efficient conversion

US researchers have found a way to convert ethanol into hydrogen very efficiently using a newly developed catalyst.

A catalyst developed by researchers at Ohio State University can help convert ethanol into hydrogen with a 90 per cent yield.

Umit Ozkan, professor of chemical and biomolecular engineering at Ohio State University, said the catalyst is also inexpensive, because it does not contain precious metals, such as platinum or rhodium.

Ozkan said: ‘Rhodium is used most often for this kind of catalyst, and it costs around $9,000 (£4,800) an ounce. Our catalyst costs around $9 (£4.80) a kilogram.’

The ethanol into hydrogen conversion process starts with a liquid biofuel such as ethanol, which is heated and pumped into a reactor, where the catalyst spurs a series of chemical reactions that ultimately convert the liquid to a hydrogen-rich gas.

The catalyst is made from tiny granules of cerium oxide – a common ingredient in ceramics – and calcium, covered with even smaller particles of cobalt. It produces hydrogen with 90 per cent efficiency at 660F (around 350C) – a low temperature by industrial standards.

One of the biggest challenges the researchers faced was how to prevent ‘coking’ – the formation of carbon fragments on the surface of the catalyst. The combination of metals – cerium oxide and calcium – solved that problem, because it promoted the movement of oxygen ions inside the catalyst. When exposed to enough oxygen, the carbon, like the biofuel, is converted into a gas and gets oxidised into carbon dioxide.

At the end of the process, waste gases such as carbon monoxide, carbon dioxide and methane are removed, and the hydrogen is purified. To make the process more energy efficient, heat exchangers capture waste heat and put that energy back into the reactor. Methane recovered in the process can be used to supply part of the energy.

Though their work was based on converting ethanol into hydrogen, Ozkan’s team is now studying how to use the same catalyst with other liquid biofuels.