Carbon dioxide turned into hydrocarbon fuel
16:00 02 August 02
Exclusive from New Scientist Print Edition
A way to turn carbon dioxide into hydrocarbons has caused a big stir at an industrial chemistry conference in New Brunwick, New Jersey. Nakamichi Yamasaki of the Tokushima Industrial Technology Center in Japan says he has a process that makes propane and butane at relatively low temperatures and pressures.
While his work still needs independent verification, if he can make even heavier hydrocarbons, it might be possible to make petrol. It has carbon chains that are between five and 12 atoms long - butane is four atoms long.
The work suggests the tantalising prospect that CO2, the main greenhouse gas, could be recycled instead of being pumped into the atmosphere.
Many people have tried before to make hydrocarbons by mixing carbon with hydrogen gas in a reaction chamber at very high temperatures, but yields have always been pitiful. Yamasaki has used hydrochloric acid as his source of hydrogen ions.
He bubbles the CO2 into a reaction vessel (see graphic) where it is heated to about 300 °C at 100 times atmospheric pressure. The heat and pressure are low enough, says Yamasaki, to make it feasible to scale up the reaction so it can run on a power station's waste heat.
Using iron powder as a catalyst, Yamasaki says he has made substantial amounts of methane, ethane, propane and butane, which he was able to vent off as gases when the mixture cooled. If he can improve the catalyst's performance he is hopeful of making heavier hydrocarbons such as petrol, too.
William Siegfried, who has lead similar experiments at the University of Minnesota in the twin cities of Minneapolis and St Paul, says his group was only able to make methane at far higher temperatures. But his process also used a nickel-based alloy as a catalyst, rather than iron.
Siegfried's group was investigating whether natural methane deposits might have formed chemically with the metal in rocks acting as a catalyst rather than forming from the decay of rotting biological material over aeons.
Unless Yamasaki's technology can make the more valuable heavier hydrocarbons such as petroleum, which are liquid at room temperature, it will not be much more use than present-day bioreactors, in which bacteria that like to feed on CO2 are induced to produce methane. "Organisms have a special talent for that kind of reaction," says Siegfried.