Oral Presentations
Sessions 1 & 2
Polymer Accelerated Hydrolysis of Starch for the Production of
Biofuels
Kendra Maxwell, Sujit Banerjee [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Improving the efficiency of the hydrolysis of starch to glucose is key to reducing energy use during the
conversion of starch to ethanol. We have found that the addition of charged polymers during hydrolysis
increases the conversion rate of starch to glucose. The aim of this study is to determine the major factors
that affect the mechanism so that optimal production rates are achieved. Electrostatic interactions largely
drive the increase in hydrolysis rate, however the results are greatly dependent on starch, enzyme and
polymer properties. A combination of analytical methods is used to study the interaction of
polyelectrolyte with enzyme as well as a polyelectrolyte with starch substrate in order to relate these
interactions to the hydrolysis mechanism. Hydrolysis with charged polymers as a function of process
conditions are also investigated.
DESIGNING OF A NOVEL CATALYST FOR COMMERCIAL
ETHANOL PRODUCTION
Manoj Agrawal [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The fermentation process for lignocellulosic ethanol production can be improved by enhancing the
efficiency of biocatalysts such as Zymomonas. Naturally occurring Zymomonas can only ferment glucose
and not xylose to ethanol. Xylose is the second major sugar after glucose in lignocellulosic hydrolysates.
Hence, to enable commercial use of this exceptionally promising ethanologen, it must be engineered for
efficient xylose fermentation.
A superior xylose fermenting strain of Zymomonas was constructed by applying a carefully designed
adaptation procedure to a strain rationally engineered to use xylose. The adapted strain can do complete
conversion of up to 10% (w/v) xylose to ethanol. The previous maximum reported in literature was 6%
(w/v) xylose that resulted in 1% (w/v) unfermented xylose. Hence, the adapted strain has nearly two-fold
higher process yield. The strain is also capable of fermenting a total of 10% glucose and 10% xylose to a
total of 9% ethanol, which is the highest amount of ethanol reported for mixed sugar fermentation by
Zymomonas.
By comparing the more adapted strain to less adapted strain, the rate limiting step for xylose fermentation
was determined and need for an altered xylitol metabolism for improving xylose fermentation was
established. A rewarding discovery of an aldo-keto reductase in Zymomonas was made during this
comparison study. While conducting the characterization experiments for biocatalyst, process
improvement and equipment modifications were carried out for the bio-reactor. These design
improvements prevent product loss and reduce operating cost.
The presentation will highlight the process of designing, characterizing and understanding molecular-
level catalytic mechanism for a highly efficient biocatalyst developed for ethanol production.
Accelerated Development of Dense Metal Membranes for High
Temperature Hydrogen Purification Using First Principles
Modeling
Sunggu Kang and David S. Sholl [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Hydrogen is a promising fuel source that has been attractive as an alternative to fossil fuels. One
of the important needs for use of hydrogen fuels is the ability to purify hydrogen from mixed gas streams.
Dense metal membranes are a well known approach for separating hydrogen from gas mixtures at high
temperatures. We performed first-principles calculations that provide a useful complement to experiments
by characterizing hydrogen permeance through dense metal membranes. We have introduced a first-
principles based method for this problem that is far more efficient than earlier calculations by our group
and others. This new approach was motivated by the detailed cluster expansion models developed earlier
by Semidey-Flecha and Sholl, and require only a handful of DFT calculations for each alloy of interest.
We have analyzed a large number of Pd-based binary alloys to demonstrate the capability of our new
approach. Specifically, we predicted the hydrogen permeability of the Pd96M4 where M = Li, Na, Mg, Al,
Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Y, Zr, Nb, Mo, Tc, Ru, Rh, Ag, Cd, In, Sn, Sb, Te, Hf,
Ta, W, Re, Os, Ir, Pt, Au, Tl, Pb, Bi, Ce, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu. Among the Pd-based
alloys we examined, multiple alloys showed the higher permeability of the hydrogen than the one in pure
Pd. These alloys would be potentially promising for hydrogen purification application.
FACILITATING EFFICIENT INVERSE MODELING OF PM2.5:
DEVELOPMENT OF THE ADJOINT OF ISORROPIA
Shannon Capps1, Armistead Russell
2, and Athanasios Nenes
1,3
1School of Chemical & Biomolecular Engineering
2School of Civil & Environmental Engineering
3School of Earth & Atmospheric Sciences
Georgia Institute of Technology, Atlanta, GA
Data assimilation of measurements of inorganic aerosol facilitates the adjustment of air quality
model parameters such as emissions rates to produce more accurate representations of ambient
concentrations. An efficient, physically-based inverse model of inorganic equilibrium thermodynamics
would help maximize the utility of an increasingly large database of in situ measurements of dust, sea
salt, and aerosol of anthropogenic origin that contribute to particulate matter less than 2.5 μm in diameter
(PM2.5). Furthermore, advances in remote sensing of speciated inorganic aerosol emissions would support
refinement of emissions parameters in global models through data assimilation. The high temporal and
spatial variability of aerosol concentrations and emissions justifies the costly development of an adjoint to
accomplish inverse modeling of millions of parameters efficiently.
The adjoint of ISORROPIA, an inorganic thermodynamic equilibrium model implemented
widely in regional and global chemical transport models, is presented. Development of the discrete
adjoint required augmenting the model to provide a differentiable algorithm to an automatic
differentiation tool, TAPENADE. Results of the adjoint are evaluated against sensitivities derived by the
complex variable method. Implementation of the adjoint of ISORROPIA has begun in the adjoint of
CMAQ, the first regional adjoint to be developed to treat PM2.5. Within the adjoint of the global chemical
transport model GEOS-Chem, the adjoint of ISORROPIA will enhance the current capabilities with
potential to assimilate the sea salt-related species sodium and chloride, essential for accurate treatment of
nitrate. This novel capacity for an inorganic thermodynamic equilibrium adjoint provides the means to
significantly enhance regional to global model simulations of inorganic aerosol, particularly by efficient
refinement of millions of emissions parameters.
Single-Walled Aluminosilicate Nanotubes:
Emerging Materials for Separations and Renewable Energy
Technology
Dun-Yen Kang [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Synthetic single-walled metal oxide (aluminosilicate) nanotubes are excellent emerging materials for a
number of potential applications involving molecular transport and adsorption; due to their unique pore
structure, high surface reactivity, and controllable dimensions. In this talk, we describe recent progress in
our laboratories on the synthesis, functionalization, and molecular diffusion and adsorption properties of
these materials. We first discuss the structure, synthesis, and characterization of these materials.
Thereafter, functionalization of the nanotube interior is an attractive target, but was initially impeded by
its high surface silanol density and resulting hydrophilicity. Controlled dehydration and dehydroxylation
of the nanotubes is critical for the success of functionalization efforts. We employ a range of solid-state
characterization tools to elucidate dehydration and dehydroxylation phenomena in the nanotubes as a
function of heat treatment. With an appropriate heat-treatment process, we show that the SWNT inner
surface can then be functionalized with various organic groups of practical interest via solid-liquid
heterogeneous reactions. We also present examples of experimental measurements and computational
predictions of the adsorption and transport properties of these materials.
DESIGN, SYNTHESIS, AND CHARACTERIZATION OF
METAL ORGANIC FRAMEWORKS FOR CO2 CAPTURE
Jagadeswara R. Karra, You-Gui Huang and Krista S.Walton
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Coal fired power plants are considered to be a major source of carbon dioxide emissions. CO2
is also an impurity in natural gas wells, and its presence will lead to low heating value of natural
gas and cause corrosion in pipelines. Adsorption technologies are attractive for CO2 capture as
they have the potential to be less energy intensive compared to other process such as amine
absorbers.
Metal organic frameworks (MOFs), a new class of porous materials, have attracted attention in
the recent years owing to their adjustable and tunable pore sizes, lower densities, higher pore
volumes and surface areas, and their ease of incorporation of functional group within their pores.
There have been several studies of CO2 adsorption in MOFs and many MOFs have shown
exceptional CO2 storage capacities at 298 K. However, these MOFs have shown
lower CO2 adsorption capacities at lower pressures. These MOFs have larger pores and hence
Vander Waals interactions between CO2 and pore walls are weaker at lower pressures. Building
MOFs with smaller pores comparable to the dimensions of the CO2 molecule and/or constructing
MOFs enriched with open metal coordination sites can enhance the capacities and selectivities
for CO2. With these considerations in mind, we have focused on designing and synthesizing
MOFs with smaller pores and open metal coordination sites.
Several new MOFs were synthesized by employing 4,4′,4′′,4′′′-benzene-1,2,4,5-
tetrayltetrabenzoic acid (BTTB) as a ligand and different metal precursors (Zn(II), Co(II), Ni(II),
Mg(II)). The adsorption equilibrium studies of gases CO2, N2, CH4 adsorption equilibrium
studies were conducted on these MOFs at room temperature, and its trends in behavior of
adsorption isotherms and adsorption selectivities for CO2 in binary mixtures of CO2/N2 and
CO2/CH4 at both low and high pressures were interpreted in terms of its structural features such
as pore size, pore dimensionality, open metal sites, surface area and pore volumes.
Control of Germanium Nanowire Crystal Growth Direction Using
Bifunctional Hydride Precursor Chemistry
Ildar Musin, Michael A. Filler [email protected]
School of Chemical & Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Semiconductor nanowire engineering provides a promising route to achieve next generation energy
conversion, photonic, and electronic materials and devices. In order to enable the appropriate function for
a particular application, control of nanowire crystal structure (e.g. lattice, orientation, faceting) is critical.
Unfortunately, there is currently limited control over crystal growth direction and it is often difficult to
prevent tapering due to unwanted radial deposition. To this end, we demonstrate the use of a bifunctional
precursor, GeH3CH3, with the ability to modulate Ge nanowire growth direction for the first time by
altering the surface energies through methyl group surface termination of nuclei at the three-phase
interface. Ge nanowires are synthesized using the vapor-liquid-solid (VLS) technique at 375 ˚C with
GeH4 in a H2 carrier gas with and without GeH3CH3. Scanning electron microscopy (SEM) revealed a
change in growth direction with the addition of GeH3CH3. High resolution transmission electron
microscopy (HRTEM) confirms the nanowire changed from the <111> to <110> crystal growth direction
and is single crystalline along its entire length. Time of flight secondary ion mass spectrometry (ToF-
SIMS) was used to detect the presence of methyl groups on the surface and X-ray photoelectron
spectroscopy (XPS) indicates this surface layer reduces the rate of oxidation. Furthermore, based on the
SEM and TEM images, the addition of GeH3CH3 can successfully increase the selectivity of axial over
radial growth by limiting film deposition on the sidewalls. The control of nuclei surface chemistry
demonstrated by our work provides an important new handle for controlling nanowire growth.
Furthermore the ability to terminate sidewalls during growth is expected to enable more robust doping
profiles by only permitting precursor incorporation through the catalyst tip.
HIGH SELECTIVITY CARBON MOLECULAR SIEVE DENSE
FILM MEMBRANES FOR ETHYLENE/ETHANE SEPARATION
Meha Rungta*, Liren Xu, William J. Koros *[email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Development of CMS dense film membranes specially tailored for the ethylene/ethane
(C2H4/C2H6) separation is investigated. A commercially available polyimide material,
Matrimid®, was pyrolyzed under vacuum (≤10mtorr) and the resultant CMS films were
characterized using pure gas C2H4 and C2H6 permeation at 35°C and 50psia feed pressure. The
effects on C2H4/C2H6 separation caused by different final vacuum pyrolysis temperatures ranging
from 500-800°C were investigated. For all pyrolysis temperatures, separation was found to
surpass the estimated polymeric C2H4/C2H6 'upper bound' line determined based on literature.
C2H4 permeability decreased with a corresponding increase in C2H4/C2H6 selectivity with
increasing pyrolysis temperature until 650-675°C where an optimum C2H4 permeability of 14-15
Barrer and a C2H4/C2H6 selectivity of ~12 were observed, both significantly higher than the
precursor material. Further, mixed gas permeation experiments, using a 63.2mol% C2H4 and
36.8mol% C2H6 mixture, showed slightly lower C2H4 permeability with an increase in
C2H4/C2H6 selectivity, rather than a selectivity decrease which is often seen with polymers.
An increase in permeation temperature resulted in an increase in C2H4 permeability with no
significant change in C2H4/C2H6 selectivity. The activation energies of permeation and diffusion
for C2H4 and C2H6 were found to be similar. Further, the C2H4/C2H6 selectivity of CMS
membranes was found to come mainly from its diffusion selectivity, whereas the sorption
selectivity was similar to polymeric membranes. The CMS membranes showed very high
'entropic selectivity' indicating that C2H4 has a significant configurational advantage over C2H6
in transport through the 'slit-like' CMS structure. This seems to be the main reason why CMS
membranes can deliver attractive C2H4/C2H6 separation performance.
OBSERVATION OF ISLANDS OF GRAPHENE ON SILICON
CARBIDE AFTER THE SELECTIVE ETCHING OF SILICON
Sonam Sherpa
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Graphene is a single layer of sp2 bonded carbon atoms arranged in a hexagonal lattice. Thus, it is a 2D
building block for graphitic material of all other dimensions. Recently, graphene has been regarded as one
of the successors to silicon for post-CMOS electronics because of the ultra-high carrier mobility; the
mobility of electrons in graphene layers can be as high as ~200,000 cm2/Vs at room temperature
compared to ~1,400 cm2/Vs in silicon. However, the promise of high-speed graphene electronics is
hindered by the lack of a growth process that is suitable for the production of graphene wafers in an
industrial scale. At present, epitaxial graphene grown on silicon carbide (SiC) by sublimation of silicon
atoms promises to be the most viable method for the production of large area graphene films. As a part of
our ongoing effort to develop an alternate route toward epitaxial graphene, we report the observation of
islands of graphene on SiC after silicon is selectively etched from SiC by employing a sequence of
electron-bombardment and HF dip. Carbon-enrichment of the SiC surface is confirmed by X-ray
photoelectron spectroscopy (XPS) while Raman spectroscopy verifies the presence of the islands of
graphene.
Structural Stability of Metal-Organic Frameworks
under Humid Conditions
Paul M. Schoenecker [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The ability to synthesize metal-organic frameworks (MOFs) with prescribed structural features has led to
intense interest in the materials for selective adsorption processes. However, sensitivity to water vapor is
widely considered to be a major weakness of MOFs that could negate potential advantages of the hybrid
materials from an applications perspective. This work presents an experimental investigation of water
adsorption in MOFs at room temperature and up to 90% relative humidity. Structural degradation of the
materials after regeneration is analyzed via powder X-ray diffraction and nitrogen adsorption
measurements. MOFs with open metal sites are quite hydrophilic but do maintain their structure, despite
significant loss in surface area due to irreversible water adsorption. The results show that copper paddle-
wheel (HKUST-1), 5-coordinated magnesium (Mg MOF-74), and 7-coordinated zirconium (UiO-66(-
NH2)) materials maintain excellent structural stability, while 4-coordinated zinc MOFs (DMOF-1-NH2;
UMCM-1) undergo complete loss of crystallinity. This work proves that careful choice of coordination
environment will lead to robust MOFs with water adsorption behavior that is comparable to conventional
adsorbents such as zeolites and activated carbon.
Oral Presentations
Sessions 3 & 4
FUNCTIONALIZTION OF BTC AND ITS EFFECT ON
PROPERTIES OF COPPER-BASED METAL-ORGANIC
FRAMEWORKS
Yang Cai, Krista Walton [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Porous metal-organic frame (MOFs) have attracted considerable attention in recent years, due to potential
applications of these novel porous material in gas storage, heterogeneous catalysis, selective guest
adsorption, and sensor technology. Compared with conventional microporous materials, MOFs with pore
sizes and chemical functionalities can be designed by modifying the metal group or organic linkers. There
is an outstanding challenge in the synthesis of crystalline nanoporous materials to systematically design
pore size and functionality of metal organic framework. Here, porous structures in which pore size and
functionality could be varied systematically have been designed by changing the functional groups of
ligands. Highly porous metal coordination polymers [Cu3(MBTC)2(H2O)3]n (where MBTC is methyl-
1,3,5-benzenetricarboxylate) and [Cu3(EBTC)2(H2O)3]n (where EBTC is ethyl-1,3,5-
benzenetricarboxylate) have been solvothermally synthesized in mixed solvents of H2O and ethanol.
They both have two different [Cu2(O2CR)4] units (where R is an aromatic ring), which create the same
three-dimensional framework with open metal sites and high surface area. The pore size and adsorption
properties are altered by introduction of the organic groups –CH3 and –C2H5. Both of them exhibit much
lower adsorption of water than HKUST-1 due to the hydrophobic functional groups. CuMBTC showed
higher adsorption of CO2 and CH4 than HKUST-1 at relative low pressure. CuEBTC has higher CO2 and
CH4 adsorption ability than CuMBTC due to its flexibility, even though it has lower surface area.
Control of Microscopic Liquid Flow with Amphiphilic Fabrics
Tracie Owens1, Johannes Leisen
2, Victor Breedveld
1, Haskell Beckham
2
1School of Chemical and Biomolecular Engineering
2School of Materials Science and Engineering
Georgia Institute of Technology, Atlanta, GA
Abstract
Fabrics provide channels for fluid flow with the same micron-sized length scales as microfluidic devices,
but they have the distinct advantage that textile manufacturing processes are not limited to small scales.
By using fabrics to carry out chemical processes, the benefits of microfluidic devices (i.e. high surface-
area-to-volume ratios and strong substrate-fluid interactions for control over bulk motion of fluids) can be
extended to large-scale applications. Novel fabric samples were carefully designed with systematically
varied patterns of yarns with hydrophilic and hydrophobic surface chemistries, in order to investigate the
mechanisms of fluid flow. Results show that these amphiphilic fabrics can selectively transport water
along their hydrophilic channels and that flow paths can be controlled through fabric design. Additionally,
simultaneous wicking of organic and aqueous liquids into these fabrics has been shown to promote
parallel flow of immiscible phases. The ultimate goal of this work is to quantify parallel flow of aqueous
and organic liquids in these amphiphilic fabrics and then use these fabrics as microfluidic contactors for
reduction of solvent volumes in large-scale liquid-liquid extractions.
TRANSPORT BEHAVIOR OF BUTANE ISOMER MIXTURES
THROUGH NEAT 6FDA-DAM DENSE FILMS
Omoye Esekhile, William J. Koros [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Transport of butane isomer through neat 6FDA-DAM membranes under ideal conditions of
single gas has been recently studied. Under annealing conditions of 230°C for 24hrs, the dual
mode transport model is valid, no plasticization effect is observed, and selectivity up to 26 can be
achieved. As single gas systems are not realistic, current research is focused on the transport
behavior of butane isomer mixtures.
Mixture systems introduce factors such as competition and bulk flow effect that may affect the
separation performance of the membrane. It was observed that butane mixtures exhibit a new
transport behavior that has not been previously observed in other gas pairs. This transport
behavior is hypothesized to be related to the much slower exchange of isobutane compared to n-
butane in the Langmuir environment.
In this symposium, I will discuss my hypothesis regarding the observed transport behavior, and
provide a model that better describes the system when compared to the commonly used binary
system extension of dual mode model accounting for bulk flow, and suggest future work.
The Surface Hydrogen-Controlled Crystal Structure of Group IV
Nanowires
Nae Chul Shin, Michael. A. Filler [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Semiconductor nanowires offer exciting opportunities to fabricate high performance devices for energy
conversion, photonics, and quantum computation. The precise control of crystal structure and geometry is
required to achieve a desired behavior, especially in highly confined nanoscale systems. Unfortunately, a
fundamental understanding of the surface chemistry that controls surface energetics is currently lacking,
despite its critical importance for robust synthesis. Although hydrogen is prevalent during the hydride-
based vapor-liquid-solid growth of semiconductor nanowires, its role is largely unknown. To this end, we
systematically studied the effect of hydrogen during the growth of Si nanowires and confirmed its
influence on crystal growth direction, catalyst ripening, and sidewall faceting for the first time. In-situ
transmission infrared (IR) spectroscopy was used to identify the presence and bonding of hydrogen on Si
nanowires as a function of growth conditions. Si nanowires were grown via a two-step process: (1) brief
nucleation at high temperature (550oC) and low pressure (5x10
-5 Torr) followed by (2) elongation under
different conditions (400 – 500oC, 5x10
-5 – 5x10
-3 Torr). Vertically-oriented epitaxial Si nanowires with
uniform densities, diameters, and lengths were obtained with this method. In-situ IR data recorded in real-
time reveals the evolution of surface Si-H stretching modes near 2090 cm-1
and 2075 cm-1
as a function of
growth conditions. Our data indicates that surface-bound hydrogen is responsible for changes in crystal
orientation even when nanowire diameter remains constant. More specifically, the surface energy of the
nuclei-vapor interface near the triple-phase-boundary is stabilized by hydrogen, which leads to a {111}
sidewall facet and growth in the [112] direction. This work demonstrates the important role that hydrogen
plays in the growth of semiconductor nanowires at multiple length scales. The extensive use of hydride
chemistries for most group IV and III-V semiconductor nanowire syntheses suggests significant
implications for a myriad of systems.
STUDY OF A HIGH CONTRAST POLYNORBORNENE AS A
NEGATIVE TONE ELECTRON BEAM RESIST
Mehrsa Raeis-Zadeh, Paul Kohl
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The electron-beam induced cross-linking lithographic characteristics of an epoxy-based
polynorbornene (PNB) dielectric were studied. The formulations showed high electron-beam
sensitivity and spatial resolution. The interaction of an electron beam with a PNB mixture
including epoxy cross-linker, photoacid generator (PAG) and sensitizer were investigated. The
contrast, photodefinability, and electron-beam activation of the components in the PNB
formulations were studied. Random cross-linking of the irradiated PNB polymer, by itself, was
found to occur at relatively high electron-beam doses. The primary route to high sensitivity was
through e-beam induced epoxy ring opening. Very high sensitivity was achieved when the epoxy
cross-linking was catalyzed by e-beam activation of a PAG. The effect of the post-exposure
bake and develop process on polymer sensitivity, contrast, and resolution was investigated. The
exposure and film thickness were optimized for each formulation to achieve nanometer scale
patternability. Structures with a critical dimension of 100 nm to 500 nm were fabricated and the
resolution limitation of the formulations and edge roughness of the structures were investigated.
Contrast values as high as approximately 8 were obtained at doses as low as 0.38 µC/cm2 for
formulation with additional PAG and epoxy cross-linkers. These studies were intended to
explore the feasibility of the PNB as a highly sensitive electron-beam resist for high contrast
pattern generation in nano scale.
Removal of Fermentation Inhibitors by Sorbents during Cellulosic-
ethanol Production
Kuang Zhang [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Ethanol can be produced from lignocellulosic biomass through fermentation. However, some
byproducts from lignocellulosics, such as furfural and 5-hydroxymethylfurfural (HMF), are
highly toxic to the fermentation and can substantially impede the ethanol-producing efficiency.
Commercial and polymer-derived activated carbons were investigated to selectively remove the
fermentation inhibitors, primarily furfural compounds, from water solution during the bio-
ethanol production. The oxygen functional groups on the carbon surface were discovered to
impose influence on the selectivity of sorbents between inhibitors and sugars during the
separation. After selectively removing inhibitors from the broth, the cell growth and ethanol
production efficiency recover noticeably in the fermentation. A sorption/desorption cycle was
designed and the sorbents were regenerated in the fixed-bed column system using ethanol-
containing liquid from fermentation.
COMPUTATIONAL STUDIES OF DNA TRANSLOCATION
THROUGH NANOPORES USING TIME-VARYING ELECTRIC
FIELDS
Christopher M. Edmonds
School of Bioengineering
Georgia Institute of Technology, Atlanta, GA
Single-molecule analysis of DNA has many applications in medicine and biotechnology
including: identification of individual genetic composition, finding possible biomarkers of disease, and/or
understanding genetic vulnerability to disease. One new promising single-molecule method, aimed at
overcoming the cost and speed limitations of conventional techniques like electrophoresis, is based on the
use of nanopore devices, individual porous channels of diameters 1-5 nm and lengths 5-25 nm. Because
DNA is negatively charged, it can be driven through a nanopore with the aid of an applied electric field.
By measuring the time required for DNA to travel through a nanopore, also known as translocation time,
many characteristics of a DNA chain can be deduced such as the chain length. Nanopore devices are
currently operated using DC electric fields and, unfortunately, cannot discriminate between biopolymers
that differ only slightly in length. The aim of the present work is to develop insights, using a detailed
computer simulation model developed in house, into the translocation of DNA through nanopores under
the application of time-varying electric fields, and to investigate the possibility of improved resolution by
this method.
OPTIMIZING THE SEPARATION OF GASEOUS
ENANTIOMERS BY SIMULATED MOVING BED AND
PRESSURE SWING ADSORPTION
Jason Bentley
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The separation of gaseous enantiomers, stereoisomers that differ only in the spatial orientation of
covalent bonds, is a particularly interesting problem. About one-third of all synthetic drugs are
marketed as racemates, one-to-one mixtures of enantiomers, despite the fact that drug receptors
may differentiate between stereoisomers such that binding likely favors one orientation over
another. Numerous studies have indicated that enantiomers of biologically active molecules have
measurable differences in their toxicity and metabolism in the human body. In particular, the
mechanism of action for fluorinated volatile anesthetics needs to be investigated further in order
to design safer general anesthetics with pure enantiomers.
It has been shown previously that the enantiomers of volatile anesthetics, such as isoflurane and
enflurane, can be separated using gas chromatography (GC) with a chiral stationary phase. This
work intends to optimize the separation of such enantiomers using GC technology by comparing
the productivity and cost of rival processes designed for this purpose. First, we investigate the
simulated moving bed (SMB) process, which features counter-current-like behavior in the
separation, and compare this to the pressure swing adsorption (PSA) process, which manipulates
the elution profiles by controlling the column pressure.
Both SMB and PSA are modeled in gPROMS as systems of differential algebraic equations, and
model parameters for enflurane were obtained by experimental work performed elsewhere.
Operating conditions are optimized such that feed throughput and product recovery for each
process are maximized subject to equal constraints on pressures and flow rates. Both productivity
and desorbent consumption are compared at the optimal operating conditions.
Magnetically separable aluminum catalysts for ring-opening
polymerization of ε-caprolactone
Wei Long and Christopher W. Jones [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Biodegradable poly(esters) that have wide applications in industries can be produced by ring-opening
polymerization (ROP) of cyclic lactone monomers. Although many highly active homogeneous metal
complexes have been reported as catalysts for the ROP of lactones, their application can be hampered by
the difficulty and cost associated with recovering the metal residue. We have identified magnetic
nanoparticles (MNPs) as an ideal alternative support for recoverable polymerization catalysts due to their
nonporosity, high external surface area, potential for facile surface modification, and easy recoverability
under a magnetic field. Magnetic nanoparticle supported aluminum catalysts are prepared and utilized for
the ring-opening polymerization of ε-caprolactone, yielding poly(caprolactone) with negligible metal
residue. The magnetic nanoparticle support and aluminum-functionalized fresh catalyst are characterized
by different techniques to assess the structure, morphology and surface area of the solid support and the
supported catalyst. The fresh catalysts display good activity for the polymerization. The catalysts are
recovered and recycled, with the used catalysts still allowing a very high conversion (>90%) to be
achieved, although at a reduced reaction rate relative to the fresh catalyst. After this initial deactivation,
the catalytic activity appears to stabilize. The polymer product is composed of predominantly low
molecular weight species at the targeted molecular weight, with a small amount of high molecular weight
polymer resulting from an inefficient chain transfer process at some catalytic sites.
MATRIMID® DERIVED CARBON MOLECULAR SIEVE
HOLLOW FIBER MEMBRANES FOR ETHYLENE/ETHANE
SEPARATION
Liren Xu, Meha Rungta, William J. Koros
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Carbon molecular sieve (CMS) membranes have shown promising separation performance
compared to conventional polymeric membranes for many gas pairs. Translating the very
attractive separation properties from dense films to hollow fibers is important for applying CMS
materials in realistic gas separations.
In this work, the C2H4/C2H6 separation, which is relatively difficult and not extensively
investigated application of CMS membranes, is considered in both dense film and hollow fiber
configurations. A commercially available polyimide, Matrimid®, is employed as a model
precursor material for CMS membrane formation. Resultant CMS membranes showed
interesting separation performance for several gas pairs (including previously reported O2/N2,
CO2/CH4, etc.), especially high selectivity for C2H4/C2H6.
Our comparative study between dense film and hollow fiber revealed very similar selectivity for
both configurations; however, a significant difference exists in effective separation layer
thickness between precursor fibers and their resultant CMS fibers. SEM results showed that the
deviation was essentially due to the collapse of the porous substructure of the precursor fiber.
Surprisingly, we found that the defect-free property of the precursor fiber was not a simple
predictor of CMS fiber performance. Even some seriously defective precursor fibers (i.e., fibers
with Knudsen diffusion selectivity), can be turned into highly selective CMS fibers close to the
fibers starting from defect-free fibers. This phenomenon of substrate collapse may be a common
feature which must be addressed in all cases involving intense heat-treatment, including thermal
cross-linking and other thermal rearrangement processes. To overcome the permeance loss
problem caused by substructure collapse, several engineering approaches as well as seeking
novel materials were considered and evaluated. These issues will be considered in detail.
ENABLING THE SUSTAINABLE SYNTHESIS OF PIPERYLENE
SULFONE: A RECYCLABLE DMSO REPLACEMENT
Gregory Marus, Eduardo Vyhmeister, Pamela Pollet, Megan E. Donaldson,
Veronica Llopis Mestre, Sean Faltermeier, Renee Roesel, Michael Tribo, Leslie
Gelbaum, Charles L. Liotta, and Charles A. Eckert
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
We have enabled the sustainable and scalable synthesis of piperylene sulfone (PS), a new dipolar aprotic
solvent. PS is a recyclable solvent with properties similar to dimethyl sulfoxide (DMSO). Traditionally,
the separation of reaction products from solvent is difficult and expensive. However, PS can be
decomposed by undergoing a reversible retro-cheletropic reaction at 110ºC, permitting facile solvent
removal and recycle. The previous synthesis of PS was not optimal toward an industrial scale due to
expensive chemicals and significant waste generation. In order to develop and optimize the process, we
first determined the kinetic parameters of reaction by employing in-situ proton NMR and then studied the
effects of radical inhibitors in reducing the self-polymerization of trans-piperylene. Additionally, we have
recovered PS from the reaction mixture via a sustainable CO2 separation method, resulting in a substantial
waste reduction. Thus, we have developed a sustainable scale-up method for PS, a recyclable DMSO
replacement.
Poster Presentations
MOLECULAR-LEVEL UNDERSTANDING OF BIOCATALYSIS
IN CELLULOSIC ETHANOL PRODUCTION
Manoj Agrawal [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The fermentation process for lignocellulosic ethanol production can be improved by enhancing the
efficiency of biocatalysts such as Zymomonas. Naturally occurring Zymomonas can only ferment glucose
and not xylose to ethanol. Xylose is the second major sugar after glucose in lignocellulosic hydrolysates.
Hence, to enable commercial use of this exceptionally promising ethanologen, it must be engineered for
efficient xylose fermentation.
A superior xylose fermenting strain of Zymomonas was constructed by applying a carefully designed
adaptation procedure to a strain rationally engineered to use xylose. The adapted strain can do complete
conversion of up to 10% (w/v) xylose to ethanol. The previous maximum reported in literature was 6%
(w/v) xylose that resulted in 1% (w/v) unfermented xylose. Hence, the adapted strain has nearly two-fold
higher process yield. The strain is also capable of fermenting a total of 10% glucose and 10% xylose to a
total of 9% ethanol, which is the highest amount of ethanol reported for mixed sugar fermentation by
Zymomonas.
By comparing the more adapted strain to less adapted strain, the rate limiting step for xylose fermentation
was determined and need for an altered xylitol metabolism for improving xylose fermentation was
established. A rewarding discovery of an aldo-keto reductase in Zymomonas was made during this
comparison study. While conducting the characterization experiments for biocatalyst, process
improvement and equipment modifications were carried out for the bio-reactor. These design
improvements prevent product loss and reduce operating cost.
The poster will highlight the process of designing, characterizing and understanding molecular-level
catalytic mechanism for a highly efficient biocatalyst developed for ethanol production.
BRINGING POLYMERS CHAINS TO ORDER-INTERCHAIN
INTERACTIONS IN POLY(3-HEXYLTHIOPHENE) AND ITS
IMPACT ON MESOSCALE CRYSTALLANITY AND CHARGE
TRANSPORT
Avishek R. Aiyar [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Tuning interchain interactions in poly(3-hexylthiophene) based conducting polymers is an effective
method of enhancing charge transport. We demonstrate that by changing the solvent environment around
the individual polymer chains, its self-assembly into mesoscale lamellar structures in the solid state can be
significantly altered, ranging from a featureless smooth surface to a nanofibrillar morphology with ca. 25-
30 nm wide fibrils. This is in close correspondence with the approximate contour length of the polymer
chain (~ 42 nm) indicating that manipulating the solvent environment can potentially lead to different
chain folding scenarios. Interestingly, subtle variations in nanofibrillar dimensions lead to differences in
charge transport, with featureless films obtained from chloroform, surprisingly exhibiting the highest
mobility of 1.2 × 10-2
cm2V
-1s
-1. X-Ray diffraction results will also be presented that would clarify the
lamellar structure within individual fibrils and the role of chain folding in intra vs inter-fibrillar transport
will also be explored.
OPTIMIZING THE SEPARATION OF GASEOUS
ENANTIOMERS BY SIMULATED MOVING BED AND
PRESSURE SWING ADSORPTION
Jason Bentley
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The separation of gaseous enantiomers, stereoisomers that differ only in the spatial orientation of
covalent bonds, is a particularly interesting problem. About one-third of all synthetic drugs are
marketed as racemates, one-to-one mixtures of enantiomers, despite the fact that drug receptors
may differentiate between stereoisomers such that binding likely favors one orientation over
another. Numerous studies have indicated that enantiomers of biologically active molecules have
measurable differences in their toxicity and metabolism in the human body. In particular, the
mechanism of action for fluorinated volatile anesthetics needs to be investigated further in order
to design safer general anesthetics with pure enantiomers.
It has been shown previously that the enantiomers of volatile anesthetics, such as isoflurane and
enflurane, can be separated using gas chromatography (GC) with a chiral stationary phase. This
work intends to optimize the separation of such enantiomers using GC technology by comparing
the productivity and cost of rival processes designed for this purpose. First, we investigate the
simulated moving bed (SMB) process, which features counter-current-like behavior in the
separation, and compare this to the pressure swing adsorption (PSA) process, which manipulates
the elution profiles by controlling the column pressure.
Both SMB and PSA are modeled in gPROMS as systems of differential algebraic equations, and
model parameters for enflurane were obtained by experimental work performed elsewhere.
Operating conditions are optimized such that feed throughput and product recovery for each
process are maximized subject to equal constraints on pressures and flow rates. Both productivity
and desorbent consumption are compared at the optimal operating conditions.
AEROSOL HYGROSCOPICITY AND CCN ACTIVATION
KINETICS IN A BOREAL FOREST ENVIRONMENT DURING
THE 2007 EUCAARI CAMPAIGN
Kate M. Cerully [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Atmospheric aerosols indirectly affect climate by acting as cloud condensation nuclei (CCN), surfaces
upon which water condenses to form cloud droplets. While it is generally thought that aerosols produce
an overall cooling effect, the indirect effect remains a large source of uncertainty in quantification and
prediction of anthropogenic climate change. For this reason, the study of aerosol and CCN properties and
behavior is necessary to in order to better understand aerosol-cloud-climate interactions. Toward this,
measurements of size-resolved CCN concentrations, hygroscopic growth, size distributions, and chemical
composition were collected from March through May, 2007, in Hyytiälä, Finland, as part of the European
Integrated project on Aerosol Cloud Climate and Air Quality Interactions (EUCAARI) campaign. Diurnal
variation of CCN maximum activated fraction, critical supersaturation, and chemical dispersion show the
effects of particle size on CCN characteristics for this region. Aerosol hygroscopicity, parameterized in
terms of a hygroscopicity parameter, κ, was derived independently from Continuous Flow Streamwise
Thermal Gradient Chamber (CFSTGC) and Hygroscopicity Tandem Differential Mobility Analyzer
measurements. κ values for all measured sizes indicate a strong presence of organics in the aerosol
population. Diurnal trends of κ show a minimum at sunrise and a maximum in the late afternoon; this
trend covaries with inorganic volume fraction and the m/z 44 organic mass fraction, an indicator of
aerosol oxidation, given by a Quadrupole Aerosol Mass Spectrometer (AMS). An analysis of CCN
activation kinetics further investigates if organic aerosol components cause inhibitions in droplet growth
rates.
FACILE “GREEN SYNTHESIS” OF SILVER-PPY CORE-SHELL
NANOPARTICLES AND THEIR STRONG CATALYTIC
ACTIVITY
Mincheol Chang and Elsa Reichmanis [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Silver-polypyrrole (PPy) core-shell nanoparticles have been fabricated by a facile one-step green
synthesis using silver nitrate as an oxidant and soluble starch as an environmentally benign stabilizer and
a co-reducing agent. The morphology of the particles was significantly affected by the reaction
temperature, changing from snake like core-shell nanomaterials to spherical core-shell nanoparticles. The
colloidal stability of silver-PPy core-shell nanoparticles was demonstrated in various solvents including
acids, bases, ionic and organic solvents. Furthermore, the core-shell nanoparticles exhibited high catalytic
activity in the reduction of methylene blue dye with NaBH4. This simple and green approach could
broaden and extend a scope to design various metal-conducting polymer core-shell nanostructures and
may have great potential for diverse applications.
COMPUTATIONAL STUDIES OF DNA TRANSLOCATION
THROUGH NANOPORES USING TIME-VARYING ELECTRIC
FIELDS
Christopher M. Edmonds
School of Bioengineering
Georgia Institute of Technology, Atlanta, GA
Single-molecule analysis of DNA has many applications in medicine and biotechnology
including: identification of individual genetic composition, finding possible biomarkers of disease, and/or
understanding genetic vulnerability to disease. One new promising single-molecule method, aimed at
overcoming the cost and speed limitations of conventional techniques like electrophoresis, is based on the
use of nanopore devices, individual porous channels of diameters 1-5 nm and lengths 5-25 nm. Because
DNA is negatively charged, it can be driven through a nanopore with the aid of an applied electric field.
By measuring the time required for DNA to travel through a nanopore, also known as translocation time,
many characteristics of a DNA chain can be deduced such as the chain length. Nanopore devices are
currently operated using DC electric fields and, unfortunately, cannot discriminate between biopolymers
that differ only slightly in length. The aim of the present work is to develop insights, using a detailed
computer simulation model developed in house, into the translocation of DNA through nanopores under
the application of time-varying electric fields, and to investigate the possibility of improved resolution by
this method.
TRANSPORT BEHAVIOR OF BUTANE ISOMER MIXTURES
THROUGH NEAT 6FDA-DAM DENSE FILMS
Omoye Esekhile, William J. Koros [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Transport of butane isomer through neat 6FDA-DAM membranes under ideal conditions of
single gas has been recently studied. Under annealing conditions of 230°C for 24hrs, the dual
mode transport model is valid, no plasticization effect is observed, and selectivity up to 26 can be
achieved. As single gas systems are not realistic, current research is focused on the transport
behavior of butane isomer mixtures.
Mixture systems introduce factors such as competition and bulk flow effect that may affect the
separation performance of the membrane. It was observed that butane mixtures exhibit a new
transport behavior that has not been previously observed in other gas pairs. This transport
behavior is hypothesized to be related to the much slower exchange of isobutane compared to n-
butane in the Langmuir environment.
In this symposium, I will discuss my hypothesis regarding the observed transport behavior, and
provide a model that better describes the system when compared to the commonly used binary
system extension of dual mode model accounting for bulk flow, and suggest future work.
Aluminosilicate Nanotubes:
Emerging Materials for Separations
Dun-Yen Kang [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Synthetic single-walled metal oxide (aluminosilicate) nanotubes are excellent emerging materials for a
number of potential applications involving molecular transport and adsorption; due to their unique pore
structure, high surface reactivity, and controllable dimensions. In this talk, we describe recent progress in
our laboratories on the synthesis, functionalization, and molecular diffusion and adsorption properties of
these materials. We first discuss the structure, synthesis, and characterization of these materials.
Thereafter, functionalization of the nanotube interior is an attractive target, but was initially impeded by
its high surface silanol density and resulting hydrophilicity. Controlled dehydration and dehydroxylation
of the nanotubes is critical for the success of functionalization efforts. We employ a range of solid-state
characterization tools to elucidate dehydration and dehydroxylation phenomena in the nanotubes as a
function of heat treatment. With an appropriate heat-treatment process, we show that the SWNT inner
surface can then be functionalized with various organic groups of practical interest via solid-liquid
heterogeneous reactions. We also present examples of experimental measurements and computational
predictions of the adsorption and transport properties of these materials.
First-principles studies of proton conduction in KTaO3
Sunggu Kang and David S. Sholl [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
KTaO3 (KTO) is a useful prototypical perovskite for examining the mechanisms of proton
transport. Previously, Gomez et al. reported DFT calculations describing proton hopping in defect-free
KTO (Gomez et al., J. Chem. Phys., 126, 194701, (2007)). We have used DFT calculations to extend that
work in two directions, namely understanding isotope effects in low and high temperature proton
transport and the role of native point defects in KTO. At cryogenic temperatures, quantum tunneling plays
an appreciable role in the net hopping of protons in KTO. At the elevated temperature characteristic of
applications involving proton conducting perovskites, tunneling is negligible but zero point energy effects
still lead to non-negligible isotope effects for H+, D
+, and T
+. We used DFT to characterize the
populations of relevant point defects in KTO as a function of experimental conditions, and to examine the
migration of proton near and in combination with these defects. This information gives useful insight into
the overall transport rates of protons through KTO under a variety of external environments.
INVESTIGATION OF STRUCTURAL EFFECTS ON THE
ADSORPTION OF CO2, CO, AND N2 IN
METAL ORGANIC FRAMEWORKS
Jagadeswara R. Karra and Krista S.Walton
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
A better understanding of how key structural features affect adsorption properties of guest
molecules is necessary for the development of simple heuristics that can lead to the design of
new metal organic frameworks (MOFs) with high gas adsorption capacities and improved
selectivities for specific gas separations. This study is an effort to understand the interplay of
different factors (pore size, heat of adsorption, open metal sites, electrostatics and ligand
functionalization) contributing to adsorption in MOFs.
Two MOFs, Cu-BTC and Zn2[bdc]2[dabco] were synthesized and characterized using powder X-
ray diffraction experiments and nitrogen adsorption at 77K. Adsorption isotherms for CO2, CO
and N2 were measured gravimetrically at room temperature. Grand Canonical Monte Carlo
(GCMC) simulations were performed to calculate adsorption of these gases for the synthesized
MOFs and two other MOFs IRMOF-1 and IRMOF-3. Heats of adsorption for each component in
all four MOFs were also computed. Binary mixture (CO2/CO) and (CO2/N2) simulations were
performed for 5%, 50%, and 95% CO2 mixtures and adsorption selectivities were calculated.
Simulations show that all the MOFs are selective for CO2 over CO and N2. Cu-BTC displays
higher selectivities for CO2 over CO at lower pressures for all mixtures due to the increase in
electrostatic interactions of CO2 with the exposed copper sites. IRMOF-3 shows surprisingly
higher selectivities for CO2 over CO for 50% and 95% mixtures at higher pressures due to the
presence of amine functionalized groups. These results and their implications for enhancement of
adsorption separation systems will be discussed.
Interactions between magnesium hydroxide and surface functional groups during
assembly of nanostructuctures on zeolite surfaces
Pei Yoong Koh
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Significant recent advances have been made in the integration of nanoscale metal oxides
into functional devices because of their superior optical, magnetic, electrical, and catalytic
properties. The performance of these devices depends on the size, shape, and morphology of the
particles used in making the devices. Furthermore, since the controlled fabrication of these
devices will undoubtedly involve supporting materials, a detailed understanding of the growth
mechanisms, and interactions of the metal oxide nanostructures with supports, as well as
identification of the optimal processing parameters for controlling the size, shape, and
morphology of these metal oxides are of practical interest.
In this poster, I will present a simple and facile deposition – precipitation method that
was developed for the fabrication of Mg(OH)2 nanostructures on zeolite 4A surfaces. The
optimum conditions for the deposition process were investigated and it was determined that the
presence of weak base such as ammonium hydroxide is essential to the control of the
morphology of the Mg(OH)2 nanostructures. A detailed examination of the interactions between
Mg(OH)2 and functional groups on the zeolite surface was conducted. Solid-state 29
Si, 27
Al, and
1H NMR spectra were coupled with FTIR measurements, pH and adsorption studies, and
thermogravimetric analyses to determine the interactions of Mg(OH)2 with surface functional
groups and to characterize structural changes in the resulting zeolite after Mg(OH)2 deposition. It
was discovered that acid – base interactions between the weakly basic Mg(OH)2 and the acidic
bridging hydroxyl protons on zeolite surface represent the dominant mechanism for the growth
of Mg(OH)2 nanostructures on the zeolite surface.
CRYSTALLIZATION PARAMETERS ESTIMATION OF
PARACETAMOL IN ETHANOL BY
FOCUS BEAM REFLECTANCE MEASUREMENT
Huayu Li [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Focus Beam Reflectance Measurement (FBRM) in crystallization process has been studied
extensively. However, translating chord length distribution (CLD) of FBRM to crystal size
distribution (CSD) is a problem resulting from the inversion of ill-posed matrix and the
estimation of the total crystal number. We proposes an approach to avoid the aforementioned
issue by comparing the measured CLD and the calculated CLD. CLD is measured and recorded
in a cooling batch, and is also simulated for the same condition. The CSD evolution curve,
obtained from the simulation of population balance equation, is then converted to normalized
CLD. The difference between measured CLD and simulated CLD is minimized in order to
estimate the parameters in crystal nucleation and growth. Simulation with these parameter values
is consistent with observations of our experiment and thus verifies the feasibility of our
approach.
Hybrid Sulfonic Acid Catalysts based on Silica -Supported
Poly(Styrene Sulfonic Acid) Brush Materials and their Application
in Ester Hydrolysis
Wei Long and Christopher W. Jones [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Catalytic conversions involving water as reactant, product or solvent are of increased importance in
biomass conversion into fuels and chemicals. In this context water tolerant solid acids are highly valued.
Polymer-oxide hybrid materials based on non-porous silica-supported sulfonic acid-containing polymer
brush materials are proposed here as a new class of potentially water-tolerant solid acid catalysis. Atom
transfer radical polymerization (ATRP) using both an established and a new ATRP initiator that is
designed to improve the hydrolytic stability of the catalyst, is used to create poly(styrene) brushes on the
surface of fumed silica. These brushes are sulfonated to produce an acid catalyst akin to an acidic
Merrifield resin, but with enhanced accessibility of the active sites. The catalysts are evaluated in the
hydrolysis of ethyl lactate, with the polymer brush materials having the same activity as a homogeneous
catalyst, p-toluene sulfonic acid, and being substantially more active than an acidic polymer resin
(Amberlyst 15). The heterogeneous nature of the catalyst allows for easy catalyst recovery and recycle.
The stability of the polymer brush catalysts depends on the nature of the initiator used, with the new
alkyl-based initiator introduced here giving enhanced stability relative to the standard, ester-containing
initiator that is most commonly used. The activity of the recycled polymer brush catalysts decreased
slightly in each cycle due to both desulfonation and the gradual detachment of the polymer chains from
the oxide support. Oxide-supported polymer brush materials are suggested to be a promising new
architecture for hybrid catalyst materials.
ENABLING THE SUSTAINABLE SYNTHESIS OF PIPERYLENE
SULFONE: A RECYCLABLE DMSO REPLACEMENT
Gregory Marus, Eduardo Vyhmeister, Pamela Pollet, Megan E. Donaldson,
Veronica Llopis Mestre, Sean Faltermeier, Renee Roesel, Michael Tribo, Leslie
Gelbaum, Charles L. Liotta, and Charles A. Eckert
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
We have enabled the sustainable and scalable synthesis of piperylene sulfone (PS), a new dipolar aprotic
solvent. PS is a recyclable solvent with properties similar to dimethyl sulfoxide (DMSO). Traditionally,
the separation of reaction products from solvent is difficult and expensive. However, PS can be
decomposed by undergoing a reversible retro-cheletropic reaction at 110ºC, permitting facile solvent
removal and recycle. The previous synthesis of PS was not optimal toward an industrial scale due to
expensive chemicals and significant waste generation. In order to develop and optimize the process, we
first determined the kinetic parameters of reaction by employing in-situ proton NMR and then studied the
effects of radical inhibitors in reducing the self-polymerization of trans-piperylene. Additionally, we have
recovered PS from the reaction mixture via a sustainable CO2 separation method, resulting in a substantial
waste reduction. Thus, we have developed a sustainable scale-up method for PS, a recyclable DMSO
replacement.
CROSSLINKING OF POLYNORBORNEN: FT-IR ANALYSIS
AND IMPACT ON MECHANICAL AND ELECTRICAL
PROPERTIES
Mehrsa Raeis-Zadeh, Paul Kohl [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The crosslinking and properties of an epoxy-based polynorbornene (PNB) dielectric was investigated.
Crosslinking was achieved by acid-catalyzed cationic crosslinking of epoxide groups. Degradation of the
crosslinks occurred at high temperature resulting in loss of linkages. Both crosslinking and degradation
reactions affect the properties of the cured films. The curing reactions and polymer properties were
studied using Fourier transform infrared spectroscopy. Full crosslinking of the films was achieved at a
relatively low cure temperature of 160°C. This cure temperature was found to be low compared to other
comparable PNB systems. The reduced modulus, internal film stress, dielectric constant, and swelling
behavior of cross-linked films were studied as a function of curing conditions. The trends in the observed
properties were consistent with the crosslink formation and degradation reactions of the epoxide
crosslinking. Polymer film cured at 160°C for 1 h resulted in the highest modulus and lowest dielectric
constant, residual stress and moisture absorption. This relatively low cure temperature is potentially very
advantageous in device assembly and processing.
Ced3A, a Cellodextrinase from the Marine Bacterium
Saccharopagus degradans and its role in cellulolytic activity.
Charles Rutter [email protected]
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
The cellodextrinase Ced3A from S. degradans was expressed in E. coli purified, and
characterized. Ced3A is a 110 kDa protein with a glycosyl family 3 domain as well as a PAF
acetylesterase domain. The sequence shows a lipobox motif on the N terminus. The enzyme
was translocated to the inner membrane in the periplasmic space when expressed in E. coli. The
enzyme showed activity on cello-oligomers between 2 and 5 glucose units. The enzyme was
shown to release glucose from the ends of these cello-oligomers. Strains expressing the Ced3A
protein were able to metabolize cellodextrins as a sole carbon source while strains without it
could not.
Engineering cellulolytic Escherichia coli towards Biofuel production
Ramanan Sekar
School of Chemical and Biomolecular Engineering Georgia Institute of Technology, Atlanta, GA
The current energy crisis is exponentially growing and widening the chasm between demand and supply.
Biofuels such as ethanol not only provide greener alternatives to fossil fuels but have been shown to
reduce emissions from vehicles, improving air and water quality. Biofuel production from sources such
as cellulose is believed to be more sustainable due to its low cost, vast availability in nature and sources
such as agricultural and industrial plant waste can be put to good use. However, the main obstacle is the
absence of a low-cost technology for overcoming its recalcitrance. To overcome this, a concept called
Consolidated Bioprocessing (CBP) has been put forward which proposes to integrate the production of
saccharolytic enzymes, hydrolysis of the carbohydrate components to sugar molecules, and the
fermentation of hexose and pentose sugars to biofuels into a single process. This process promises to
lower the cost and improve the efficiency towards product formation. However, CBP demands adequate
cellulase production in order to hydrolyze cellulose into utilizable sugars to maintain cell growth and the
production of required enzymes and desired biofuels. In the recent past, biotechnological tools such as
metabolic engineering have enabled the production of a large array of biocatalysts that are capable of
converting substrates such as glucose into desirable compounds through recombinant cellulolytic
strategies. The present study involves development of cellulolytic E. coli strains towards cellodextrin
assimilation by employing an energy-saving strategy in cellulose metabolism through the phosphorolytic
cleavage of cellodextrin mixture produced as cellulosic degradation products. This method is shown to be
energetically more favorable compared to hydrolytic cleavage of oligomers. The genome sequence of
cellulolytic Saccharophagus Degradans shows the presence of cellobiose and cellodextrin
phosphorylases which carries out phosphorylatic cleavage of β-glucosidic bonds present in cellodextrins
yielding α-D-glucose-1-phosphate and cellodextrin with lower chain lengths. A complete characterization
has been done in this study of the two enzymes from S. Degradans for temperature, pH and kinetics with
various substrates. This approach of combining degradation of higher oligomers with increased
phosphorylatic cleavage provides availability of more ATP molecules to the cells which can be channeled
towards assimilation, transport of essential compounds across the cell membrane and overall growth of
biomass. This would also ensure that cells growing on cellulose have enough cellular energy to be
dispensed for the necessary cellulase synthesis.
Establishing Structure Property Relationships for Reversible Ionic
liquids for CO2 capture
Swetha Sivaswamy
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
We discuss novel amine solvents for carbon-dioxide capture from flue gas of coal powered power plants.
Silylamines - that our group has developed - react with CO2 to form ionic liquids and release CO2 and
revert back to molecular form on heating to 50-70°C - much less than the aqueous amine solutions. We
have gathered thermodynamic data of silylamines which will be used in process design and simulation for
scale-up. I will present correlations between structure and properties that we have obtained. This
knowledge will be useful to introduce modifications in the silylamines. I will discuss our approaches to
minimize the viscosity of the solvent systems as well.
MATRIMID® CARBON MOLECULAR SIEVE HOLLOW FIBER
MEMBRANES FOR ETHYLENE/ETHANE SEPARATION
Liren Xu, Meha Rungta, William J. Koros
School of Chemical and Biomolecular Engineering
Georgia Institute of Technology, Atlanta, GA
Carbon molecular sieve (CMS) membranes have shown promising separation performance
compared to conventional polymeric membranes for many gas pairs. Translating the very
attractive separation properties from dense films to hollow fibers is important for applying CMS
materials in realistic gas separations.
In this work, the C2H4/C2H6 separation, which is relatively difficult and not extensively
investigated application of CMS membranes, is considered in both dense film and hollow fiber
configurations. A commercially available polyimide, Matrimid®, is employed as a model
precursor material for CMS membrane formation. Resultant CMS membranes showed
interesting separation performance for several gas pairs (including previously reported O2/N2,
CO2/CH4, etc.), especially high selectivity for C2H4/C2H6.
Our comparative study between dense film and hollow fiber revealed very similar selectivity for
both configurations; however, a significant difference exists in effective separation layer
thickness between precursor fibers and their resultant CMS fibers. SEM results showed that the
deviation was essentially due to the collapse of the porous substructure of the precursor fiber.
Surprisingly, we found that the defect-free property of the precursor fiber was not a simple
predictor of CMS fiber performance. Even some seriously defective precursor fibers (i.e., fibers
with Knudsen diffusion selectivity), can be turned into highly selective CMS fibers close to the
fibers starting from defect-free fibers. This phenomenon of substrate collapse may be a common
feature which must be addressed in all cases involving intense heat-treatment, including thermal
cross-linking and other thermal rearrangement processes. To overcome the permeance loss
problem caused by substructure collapse, several engineering approaches as well as seeking
novel materials were considered and evaluated. These issues will be considered in detail.
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