Benny D. Freeman, winner of the 2009 American
Chemical Society Award in Applied Polymer Science, is cited for his “pioneering
polymer science research that has defined the state of the art in polymer-based
gas, liquid, and vapor separation membranes.”
Benny is the Kenneth A. Kobe and Paul
D. and Betty Robertson Meek & American Petrofina Centennial Professor of
Chemical Engineering at the University of Texas at Austin. He
received a B.S. from North
Carolina State University in
1983 and a Ph.D. from the University of California, Berkeley in 1988, all in chemical engineering. He was a
NATO Postdoctoral Fellow during 1988-89 at the Ecole Supérieure de Physique et
Chimie Industrielles de la Ville de Paris (ESPCI) in the laboratories of
Professor Lucien Monnerie and Liliane Bokobza. He served on the chemical
engineering faculty of North
Carolina State University
during 1989-2002. He joined the faculty at the University of Texas at Austin in 2002.
Benny supervises the research of a
large group of graduate students in the area of membranes for separations.
Some highlights from his productive career are given below.
Over the past 40 years, gas
separation properties of thousands of polymers were measured. Empirically, a
tradeoff is observed between gas permeability and gas selectivity: more
permeable polymers are less selective and vice versa. This behavior was
widely recognized, but not well understood. Benny developed a model using
fundamental facts that predicts this tradeoff behavior [Macromolecules, 32,
375 (1999)]. This publication helped change the direction of research away from
Edisonian structure/property studies seeking higher permeability and higher
selectivity and towards issues such as membranes with improved chemical
stability and membranes based on materials other than polymers (e.g.,
polymer/inorganic hybrids and inorganic materials).
His group, in collaboration with Dr.
Ingo Pinnau at Membrane Technology and Research, Inc., pioneered dispersion of nonporous
inorganic nanoparticles in rigid polymers to produce nanocomposites that are,
counterintuitively, more permeable and more selective than the native polymer.
Their landmark work [Science, 296, 519 (2002)] expanded the
portfolio of strategies to rationally manipulate permeation properties.
Removal of organic vapors from
mixtures with air or nitrogen and removal of higher hydrocarbons from natural
gas requires membranes that selectively remove larger molecules from
mixtures with smaller molecules (so-called reverse-selective membranes).
Working with Ingo Pinnau and Prof. Toshio Masuda of Kyoto University
catalyzed the preparation of libraries of new reverse-selective materials.
These materials harness higher solubility of larger molecules to promote high
permeability of larger, more soluble components (e.g., n-butane) in
mixtures with light gases (e.g., CH4), a concept not previously
appreciated. A review article co-authored by Benny [Prog. Polym. Sci., 26,
721-798 (2001)] summarizes the literature in this area.
In contrast to the traditional
approach of using rigid, glassy polymers for gas separation materials, Benny’s
group has tuned the molecular structure of polar, rubbery polymers to
remove CO2 from gas mixtures. For CO2/H2
separations, these materials, based on poly(ethylene oxide) diacrylate, have
among the highest combinations of CO2 permeability and CO2/H2
selectivity ever reported, and their mixed gas selectivity improves as CO2
partial pressure increases [Science, 311, 639 (2006)], which is
opposite to conventional polymer membranes, where selectivity decreases, often
catastrophically, at high CO2 partial pressures. In natural gas
separations, these membranes exhibit good CO2/CH4
selectivity at high CO2 partial pressures and are an order of
magnitude more permeable than conventional polymers [Adv. Matls., 18,
39 (2006)]. Traditional rigid polymers rely on high diffusivity selectivity to
achieve high permeability selectivity whereas these rubbery polymers work based
on high solubility selectivity. Membranes based on these materials are being
deployed commercially for hydrogen purification.
While working on polymer materials
design principles that challenge conventional wisdom, such as those described
above, Benny and colleagues from Hanyang University in Seoul, Korea (Professors
Young Moo Lee and Ho Bum Park) and CSIRO in Melbourne, Australia (Dr. Anita
Hill) pushed the envelope on traditional, highly size selective materials by
using biomimetic principles to design gas separation membranes having very high
CO2 permeability (1610 Barrer) and high CO2/CH4
selectivity (40) under strongly plasticizing conditions [Science, 318,
254 (2007)] to achieve what has been called a “breakthrough in the development
of polymers for gas separation.”
In liquid separations, Benny has
challenged conventional notions regarding wastewater purification membrane
design. Such membranes are typically porous and the major factor limiting
their service life is pore blockage by contaminants, which leads to
irreversible loss in membrane flux (membrane fouling). Ingo Pinnau and Benny
used thin (< 1 micrometer), nonporous membranes of self-assembled
block copolymers to provide continuous hydrophilic channels for water
permeation through a mechanically stable, high strength matrix. These
membranes have very high water flux but block contaminant transport, reducing
membrane fouling by more than 90% for oily wastewater purification, which
effectively increases membrane throughput by more than 10x. These membranes are
being installed aboard a Navy ship to purify oily wastewater.
A recent collaboration with Professor
James McGrath at Virginia Tech has yielded new desalination membranes with
previously unattainable property profiles. This research has identified
sulfonated polysulfones having uniquely outstanding chlorine resistance and
excellent desalination properties. Current desalination membranes are degraded
by chlorine, a widely used disinfectant. Consequently, this discovery is
important because it eliminates a processing step, dechlorination, which
currently limits the productivity of desalination plants. Initial results have
garnered worldwide attention [Science, 313, 1088 (2006)].
Benny has organized major ACS and
AIChE symposia, chaired the PMSE Division of ACS, chaired the Gordon Research
Conference on Membranes, co-chaired the annual meeting of the North American
Membrane Society and the International Congress on Membranes, the largest
membrane meeting in the world. His students have taken high-profile positions
in the field, further extending his influence to the next generation of
scientists.
Benny also received the 2008 Award
for Excellence in Industrial Gases Technology from the American Institute for
Chemical Engineers for his work on gas separations using membranes and a 2008
IBM Faculty Award, which is an internationally competitive award given to
university faculty who have an outstanding reputation for contributions to
their field. In 2002, he received the PMSE Cooperative Research Award. He has
received numerous additional teaching and research awards. He is an Associate
Editor of Industrial & Engineering
Chemistry Research
(published by ACS) and is a member of the Editorial Board of the Journal of
Membrane Science.
Past Applied Polymer Science Award Winners
, Number of access since November 07, 2000
