Tires are dirty business, and we're not just talking
about the mud they gather as they roll beneath your car.
Manufacturing rubber is a resource-intensive process that is
heavily reliant on petroleum, but now scientists are claiming a
chemical breakthrough that replaces the key molecule in
conventional tires with one sourced from grass and trees
instead, all without affecting the tire's color, shape or
performance.
The environmental impact of tire production has
prompted a years-long search for a more sustainable method.
These efforts have focused on the main component of rubber, a
molecule called isoprene. To make isoprene, molecules in
petroleum are thermally broken apart and the molecule is
isolated from hundreds of other chemicals and purified, at which
point it organizes itself into long polymer chains.
Conveniently, isoprene can also be derived from
natural sources. While researchers have explored the possibility
of using sugars derived from biomass to make tire rubber, doing
so on anything near the scale required is no easy feat. In 2010,
for example, Goodyear described a
method of engineering bacteria to ramp up the microbial
production of isoprene, while the
cloning of a key enzyme to produce man-made isoprene in 2012
offered yet another potential way forward.
Now researchers at the University of Minnesota are
claiming a new breakthrough in the area, by way of a chemical
process that combines the boosting of natural microbial
fermentation with catalytic refining, similar to the process
used to refine petroleum.
The chemical process combines the boosting of
natural microbial fermentation with catalytic refining(Credit:
University of Minnesota)
It begins with the microbial fermentation of plant
sugars, such as glucose, into something called itaconic acid.
This acid is then mixed with hydrogen, causing a chemical
reaction that results in something called methyl-THF.
And the third step, which is where the breakthrough
lies, involves using a recently discovered catalyst called
Phosphorous Self-Pillared Pentasil to dehydrate the methyl-THF
into isoprene. This method resulted in catalytic efficiency as
high as 90 percent, with most of the product being isoprene,
something the researchers say gives the prospect of renewable
isoprene a real boost and could even lead to other advanced
rubber-based products.
"The performance of the new P-containing zeolite
catalysts such as S-PPP was surprising," says Paul Dauenhauer, a
University of Minnesota associate professor of chemical
engineering and lead author of the new study. "This new class of
solid acid catalysts exhibits dramatically improved catalytic
efficiency and is the reason renewable isoprene is possible."
The research was published in the journal
ACS Catalysis.