Joined: 16 Mar 2004
|Posted: Mon Feb 04, 2008 11:32 am Post subject: Tiny tubes set chemical reactions racing
|The efficiency of a fuel-generating chemical reaction can be boosted dramatically by mixing chemicals and catalysts inside nanoscopic test tubes, Chinese researchers have shown.
A team from the Dalian Institute of Chemical Physics in China found that a mixture of carbon monoxide and hydrogen (known as syngas) makes ethanol more quickly, with the help of tiny particles of a metal catalyst, when poured into carbon nanotubes.
The catalytic reaction was found to be more than 10 times faster when performed inside nanotubes, despite the lack of space for fresh reactants to circulate. The team showed multi-wall carbon nanotubes - 4 and 8 nanometres wide on the inside and 400 nm in length - to boost the metal catalyst's efficiency.
The researchers think the finding could be important for two reasons: Firstly, it could prove useful for generating ethanol fuel using syngas extracted from natural gas, coal or even biomass. Secondly, they suspect that other catalysts should get a speed boost from being inside nanotubes.
Inside and out
Ethanol yield was measured when metal catalyst particles were attached to both the outside and the inside of the nanotubes. The process occurred more than 10 times more quickly when they were on the inside.
Reactions were also performed inside different types of tube - such as glass - the results of which suggest that it is not just the shape of the environment that makes the difference, but the material too.
The team believes the unique way electrons are arranged inside carbon nanotubes may be responsible for the effect. They are more sparse on the inside of a tube and this may make it easier for the catalyst to loosen the bond that holds carbon and oxygen molecules together.
Further research needed
Andrei Khlobystov, a chemist at Nottingham University in the UK, agrees that this sounds feasible. He notes that rolling a sheet of carbon into a nanotube creates strains that push more electrons to the outside of the tube.
In 2004, Khlobystov and colleagues set a world record by creating the world's smallest test tube - placing nanoscale carbon spheres inside a single-walled nanotube.
Khlobystov points out that the catalysts used inside and outside the tubes were slightly different. But he is impressed with the results and believes other metal catalysts may benefit from the same trick.
"I am delighted others are investigating because there could be [other] useful chemical effects inside nanotubes," he says.
Journal reference: Nature Materials (DOI: 10.1038/nmat1916)