Page 66 - Plastics News December2018

TECHNOLOGY

Scientists develop new process that could reduce cost of manufacturing
plastic

cientists have developed new filtering material that prefer to do the opposite if feasible. "You want to absorb
Scould reduce the environmental cost of manufacturing the ethane byproduct and let the ethylene pass through,"
plastic by separating purified ethylene out of ethane. he said. Under a microscope, the metal-organic framework
By extracting the key ingredient in the most common looks like a half-built skyscraper of girders and no walls,
form of plastic from a mixture of other chemicals, they according to the scientists. The girders surfaces contain
believe their process consumes far less energy than certain hydrocarbon molecules that will stick to firmly. A
other methods. The metal-organic framework developed mixture of two hydrocarbons poured through the right MOF
by the National Institute of Standards and Technology can pull one kind of molecule out of the mix and allowing
was published in the journal Science. The plastic and other hydrocarbon to emerge in pure form.The scientists
built their system at the University of
Texas at San Antonio and China's Taiyuan
University of Technology. In 2012, other
researchers at the NCNR found that a
particular framework called MOF-74
separated a variety of hydrocarbons,
including ethylene.

"A huge topic in chemistry is finding
ways to break the strong bond that
forms between carbon and hydrogen,"
said team leader UTSA professor Banglin
Chen. "Doing that allows you to create
a lot of valuable new materials. We
found previous research that showed
that compounds containing iron peroxide
could break that bond." To break the
bond in a hydrocarbon molecule, the
compound would first have to attract
the molecule. By modifying MOF-74's
petroleum industries manufacture around 170 million tons walls to contain a structure similar to the compound, the
of ethylene worldwide each year by pulling the material molecule it attracted from their mixture was ethane.By
out of a mixture with ethane in the oil refining process. using neutron diffraction, they found what part of the
For years, scientists have been searching for an alternative MOF's surface attracts ethane."Without the fundamental
method to the current high-energy process that cools down understanding of the mechanism, no one would believe
the crude to more than 212 degrees below zero Fahrenheit our results," Chen said. "We also think that we can try to
Industries would prefer to wring out ethylene, which is add other small groups to the surface, maybe do other
the molecule needed to create polyethylene used to make things. It's a whole new research direction and we're very
shopping bags and other everyday containers. Dr. Wei excited."The researchers said they need to further develop
Zhou, a scientist at the NCNR said, "It's very difficult to the process before it is adapted. "We proved this route is
do. Most MOFs that have been studied grab onto ethylene promising, but we're not claiming our materials perform
rather than ethane. A few of them have even demonstrated so well they can't be improved," Zhou said. "Our future
excellent separation performance, by selectively adsorbing goal is to dramatically increase their selectivity. It's worth
the ethylene." From an industrial perspective, they would pursuing further."

Plastics News December 2018 6668