Oral Presentationssymposium.chbe.gatech.edu/sites/default/files/2011Topics.pdfThe presentation will highlight the process of designing, characterizing and understanding molecular-

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]



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]



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

[email protected]

1School of Chemical & Biomolecular Engineering

2School of Civil & Environmental Engineering

3School of Earth & Atmospheric Sciences


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]



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

[email protected]



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


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]



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

[email protected]



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]



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]



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

[email protected]

1School of Chemical and Biomolecular Engineering

2School of Materials Science and Engineering


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]



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]



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

[email protected]



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]



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

[email protected]

School of Bioengineering


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.

mailto:[email protected]

OPTIMIZING THE SEPARATION OF GASEOUS

ENANTIOMERS BY SIMULATED MOVING BED AND

PRESSURE SWING ADSORPTION

Jason Bentley

[email protected]



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]



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

[email protected]



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

[email protected]



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]



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]



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

[email protected]



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]



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]



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

[email protected]

School of Bioengineering


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]



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]



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]



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

[email protected]



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

[email protected]



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]



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]



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

[email protected]



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]



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]



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

[email protected]

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

[email protected]



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

[email protected]



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.

Documents

Oral Presentationssymposium.chbe.gatech.edu/sites/default/files/2011Topics.pdfThe presentation will highlight the process of designing, characterizing and understanding molecular-