A University of Minnesota
team of researchers has overcome a major hurdle in the quest to design a
specialized type of molecular sieve that could make the production of gasoline,
plastics, and various chemicals more cost effective and energy efficient. The
breakthrough research, led by chemical engineering and materials science
professor Michael Tsapatsis in the university’s College of Science
and Engineering, is published in Science.
After more than a decade
of research, the team devised a means for developing free-standing, ultra-thin
zeolite nanosheets that as thin films can speed up the filtration process and
require less energy. The team has a provisional patent and hopes to
commercialize the technology.
“In addition to research
on new renewable fuels, chemicals, and natural plastics, we also need to look
at the production processes of these and other products we use now and try to
find ways to save energy,” Tsapatsis says.
Separating mixed substances
can demand considerable amounts of energy—currently estimated to be
approximately 15% of the total energy consumption—part of which is wasted due
to process inefficiencies. In days of abundant and inexpensive fuel, this was
not a major consideration when designing industrial separation processes such
as distillation for purifying gasoline and polymer precursors. But as energy
prices rise and policies promote efficiency, the need for more energy-efficient
alternatives has grown.
One promising option for
more energy-efficient separations is high-resolution molecular separation with
membranes. They are based on preferential adsorption and/or sieving of
molecules with minute size and shape differences. Among the candidates for
selective separation membranes, zeolite materials (crystals with
molecular-sized pores) show particular promise.
While zeolites have been
used as adsorbents and catalysts for several decades, there have been
substantial challenges in processing zeolitic materials into extended sheets
that remain intact. To enable energy-savings technology, scientists needed to
develop cost-effective, reliable, and scalable deposition methods for thin film
zeolite formation.
The University of Minnesota
team used sound waves in a specialized centrifuge process to develop “carpets”
of flaky crystal-type nanosheets that are not only flat, but have just the
right amount of thickness. The resulting product can be used to separate
molecules as a sieve or as a membrane barrier in both research and industrial applications.
“We think this discovery
holds great promise in commercial applications,” says Kumar Varoon, a University of Minnesota chemical engineering and
materials science PhD candidate and one of the primary authors of the paper
published in Science. “This material has good coverage and is very thin. It
could significantly reduce production costs in refineries and save energy.”
