Catalyst converts bio-diesel waste into valuable chemicals

Palladium-gold nanoparticles are not only excellent catalysts for cleaning polluted water, but can also convert biodiesel waste into valuable chemicals, researchers say.
A new study by Rice University chemical engineer Michael Wong examined whether palladium-gold nanocatalysts could convert glycerol, a waste byproduct of biodiesel production, into high-value chemicals.
The data from the study produced a "volcano plot," a graph with a sharp spike that depicts a "Goldilocks effect," a "just right" balance of palladium and gold that is about 10 times faster at converting glycerol than catalysts of either metal alone.
"We've now seen this volcano plot at least four times now, first with trichloroethylene (TCE), then with the dry cleaning contaminant 'perc,' and more recently with chloroform and nitrites," Wong said.

"The remarkable thing is that the reaction, in each case, is very different," said Wong.
Wong, Rice graduate student and lead author Zhun Zhao and colleagues from the Argonne National Laboratory and the University of Groningen in Holland used high-powered X-ray spectroscopy and other techniques to show that the "Goldilocks" coverage area for glycerol catalysis was about 60 per cent.

"Palladium by itself oxidises, which is not good because it slows down the catalysis," Zhao said.
"We found that the gold in our catalysts helps stabilise the palladium and prevents it from degrading. The catalysts in our tests had extremely high durability.

"Our best catalyst produced a glycerol product with higher purity and in less time than anything else we found in the literature," said Zhao.
The study appears in the Royal Society of Chemistry's journal Chemical Science.