New catalyst could improve biofuel production

October 16, 2014, Pullman, Wash. – Washington State
University researchers have developed a new catalyst that could lead to making
biofuels cheaply and more efficiently.

Led by Professor Yong Wang, the
researchers mixed inexpensive iron with a tiny amount of rare palladium to make
the catalyst. Their work was featured on the cover of the October issue of the
journal ACS Catalysis.

Removing oxygen for better fuel

Researchers, government leaders and industry leaders are
interested in renewable biofuels as a way to reduce national dependence on
fossil fuels and reduce emissions of harmful carbon dioxide to the atmosphere,
where it contributes to global warming.

One of the biggest challenges in biofuels production is
grabbing carbon for fuel while also removing oxygen. High oxygen content makes
biofuel less stable, gooier and less efficient than fossil fuels and not
suitable for airplane or diesel fuels. To improve production, researchers also
want to use as little hydrogen as possible in the reaction.

The WSU researchers developed a mixture of two metals, iron
along with a tiny amount of palladium, to serve as a catalyst to efficiently
and cheaply remove oxygen.

“The synergy between the palladium and the iron is
incredible,” said Wang, who holds a joint appointment with Pacific Northwest
National Laboratory and WSU. “When combined, the catalyst is far better than
the metals alone in terms of activity, stability and selectivity.”

Palladium makes iron work better

Iron catalysts have been an inexpensive way to remove oxygen
from plant-based materials. But the catalyst can stop working when it interacts
with water, which is a necessary part of biofuels production. The iron rusts.

Palladium can work in water, but it is not terrific at removing
oxygen; and the metal is very expensive.

The researchers found that adding extremely small amounts of
palladium to iron helped cover the iron surface of the catalyst with hydrogen,
which caused the reaction to speed up and work better. It also prevented water
from interrupting the reactions. And less hydrogen was needed to remove the
oxygen.

“With biofuels, you need to remove as much oxygen as
possible to gain energy density,” said Wang. “Of course, in the process, you
want to minimize the costs of oxygen removal. In this case, you minimize
hydrogen consumption, increase the overall activity and gain high yields of the
desired fuel products using much less expensive and more abundant catalyst
materials.”

WSU teams collaborate

The team used advanced techniques – including
high-resolution transmission electron microscopy, X-ray photoelectron
spectroscopy and extended X-ray absorption fine structure spectroscopy – to
understand how atoms on the catalyst’s surface interact with the plant material
lignin. Corresponding theoretical calculations were done by a WSU team led by
Jean-Sabin McEwen.

“By adding the palladium, we could potentially use metals
such as iron, which are cheaper and abundant while functioning at better rates
with higher yields than palladium or iron alone,” said Wang.

The researchers would like to extend their studies under
more realistic conditions that more closely mimic real biofuels production.