There's no way around this problem; if a reaction released energy both going forward and going backward, it could fuel a perpetual motion machine, which, of course, is an impossibility.
Still, it is possible to make hydrocarbon combustion reactions run backward -- either by brute force or by finesse.
The brute force way is to pump in energy. That's how the Nazi turned coal into oil during World War II. Saddled with an abundance of coal but short on oil, Germany solved the problem by transmuting coal to oil by chemical means.
But Nazi synthetic oil plants worked only at high temperatures and pressures and much more energy was used to drive the reactions than was ultimately stored in synthetic oil they produced.
The finesse is to devise a chemical compound, a catalyst, that takes the reactants up an alternative, lower energy pathway to the reaction products. In effect, instead of going straight up the energy hill, the reaction takes a more manageableideally the minimal-energy-- series of switchbacks to the top.
Like a ball in a glove
Last year Mirica's group was working with a palladium compound that they hoped could catalyze the splitting of water. "The catalyst we made for that reaction worked," says Mirica "but not as well as we hoped. But we noticed it was easily oxidized, even by the oxygen in air.
"This was our first hint that this might be an interesting system. So then we asked what else we could use it for.
"One of our ideas was to use it to turn methane into ethane." Methane, the main component of natural gas, is released in large amounts when an oil well is tapped. Currently the methane from the oil fields is wasted; it is flared off on site, releasing even more carbon dioxide into the atmosphere.
Turning methane to ethane, says Mirica, could be the first step in a process of building longer-chain hydrocarbons such as butane and octane, which would be liq
|Contact: Diana Lutz|
Washington University in St. Louis