Alcohol economy

28 February 2013
Posted by Chris Smith.

A new catalyst that can unleash the clean potential of hydrogen, without the risk of an explosion, has been developed by scientists in Germany.

Hydrogen is regarded as a promising candidate clean energy source: it packs a high energy punch but the only combustion product is water. The downside is that transporting it would require a complete overhaul of our present fuel infrastructure, and gaseous hydrogen is also unsafe, a fact indelibly endorsed by the 1937 Hindenberg disaster.

Instead scientists are searching for molecules that can act as sources of hydrogen when they are appropriately broken down, but can be more easily and safely stored and transported.

Methanol - a carbon atom linked to three hydrogen atoms and an alcohol (OH) group and 12.6% hydrogen by weight, fits the bill very well and some scientists have consequently advocated a "methanol economy" as a solution to the world's present energy and environmental problem.

But the fly in the ointment, or even the alcohol, is that, with present technology, to release the hydrogen locked up in methanol requires extremely harsh chemical conditions including very high temperatures and costly platinum-based catalysts. This places methanol as a fuel source beyond the economic reach of most domestic and even industrial consumers.

But now, University of Rostock researcher Martin Nielsen and his colleagues have come up with a catalyst molecule based on the much cheaper metal ruthenium (priced at a tenth the cost of platinum).

In the presence of a strong alkali, like potassium hydroxide, the new ruthenium complex will turn a molecule of methanol and a molecule of water into 6 molecules of hydrogen and a molecule of CO2.

But before environmental cynics point a comdemnatory finger at the carbon dioxide molecule, the team point out that this rapidly reacts in the alkali to produce a solid carbonate - like limescale - so it isn't actually released into the environment.

The catalyst also appears to be stable over long periods of time - the researchers show that it remains active over several weeks - but it's not a fait accompli.

As Toronto chemist Doug Stephan points out in an accompanying commentary on the work which is published in Nature, the activity of the catalyst is probably good enough to power mobile electronic devices, but for transport applications - such as in cars - then the process needs to go up a gear.

"But that's just optimisation," he says. "And that's what the German team will be concentrating on next: making a catalyst that delivers the same chemistry but at a higher rate..."

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