PSE Success Story:
Scientists Develop Green Method to Produce Propylene Oxide
Propylene oxide is commonly used in the manufacturing of plastics and propylene glycols for
paints, household detergents and automotive brake fluids.
The Challenge
The current production of propylene oxide
creates a significant amount of by-products
that are harmful to the environment, including
chlorinated or peroxycarboxylic waste, or use
expensive reagents, such as hydrogen peroxide.
Manufacturers have tried using large silver
particles to produce propylene oxide from
propylene, but this method suffers from
a low selectivity or low conversion to
propylene oxide—creating a large amount
of carbon dioxide.
The Solution
Argonne researchers discovered that
nanoscale clusters of silver, consisting of
both three-atom clusters as well as larger
nanostructures of 3.5 nanometers in size
made of three-atom clusters, are highly active
and selective catalysts for the production
of propylene oxide. They then modeled the
underlying mechanism behind why these
ultrasmall nanoparticles of silver were so
effective in creating propylene oxide. The
researchers discovered that the open shell
electronic structure of the silver catalysts was the
impetus behind the nanoclusters’ selectivity.
Calculated relaxed structure and spin densities
of a Ag33 cluster. The optimized “nanohill”
geometries are very disordered and suggest that
the 2x4nm agglomerated nanoparticles might
have core-shell structures. The high-spin states
show significant spin density on some surface
atoms, which are expected to be more active for
propylene epoxidation as on the silver trimers.
The Results
Argonne scientists identified a new means of
producing propylene oxide that is both more
environmentally friendly and less expensive than current production methods. The new class of
silver-based catalysts can produce the chemical with few by-products at low temperatures.
The findings resulted from a highly collaborative team that involved five Argonne divisions and
collaborators from the Fritz-Haber-Institut in Berlin and the University of Illinois at Chicago.
“Propylene oxide is a building block in the creation of several other industrially relevant
chemicals, but the current methods of creating it are not efficient,” said Larry Curtiss,
Argonne materials chemist. “The work opens a new chapter in the field of silver as a
catalyst for propene epoxidation.”
More
- Scientists Develop Green Method to Produce Propylene Oxide (742 kB pdf)
July 2010
|
