CHE (Chemical Engineering, Petroleum, Nuclear Engineering)  

UKC 2012, Los Angeles, August 8-11.

*Corresponding author, E-mail address: kklim@hoseo.edu

The Effects of DME on the Kinetics of Gas Hydrate Formation

Gye-Gyu Lim*

Department of Chemical Engineering, Hoseo University

Asan, Chung Nam, South Korea (kklim@hoseo.edu)

ABSTRACT

I. INTRODUCTION

Natural gas hydrates form large reserves both on

land and offshore all over the earth. In the past,

research mainly focused on the inhibition of gas

hydrates since gas hydrates are commonly

encountered blocking pipe lines when transporting

natural gas. Electrolytes, alcohols and glycol are

common additives inhibiting gas hydrate formation.

Thereby the phase equilibrium is shifted towards

higher pressures and lower temperatures. In this

work the objective is first to get the effects of DME

on the rate of gas hydrate formation and second to

better understand the behavior of chemical

additives. DME(CH3OCH3) has similar physical

properties to LPG and a higher range of cetane

number than diesel (C10~C20). DME is also an

oxygenated environmentally friendly fuel with

nearly zero smoke and low PM, no peroxides

formation, and less engine noise. It can be also

used in hydrogen source for fuel cell. DME has

been synthesized from syngas through CO2

reforming using methane.

II. THEORY

A. Growth kinetics

The driving force of gas hydrate formation can

be regarded as crystallization process so that it

can be described by the supersaturation of

gaseous component in the aqueous liquid phase.

Because of hydrate formation the supersaturation

decreases and the system approaches

equilibrium. In order to study the kinetics of gas

hydrate formation, the definition as given in the

classical crystallization theory is used.

Crystallization is separated into the nucleation

stage followed by crystal growth. The nucleation

stage is the first period in which very small nuclei

are formed in oversaturated solutions. The

second stage is the growth of those nuclei to

larger sizes, the crystals.

III. EXPERIMENTS

A. Experimental set-up

The set-up was designed to study the gas

hydrate formation at constant temperature for pure

gases and gas mixtures. It consists of a high

pressure autoclave, a mechanic stirrer and a gas

supply system.

B. Experimental Procedures

In practice, nucleation can hardly be detected. In

this work the sum of times for crystals to reach

detectable sizes including the time necessary to

dissolve the gas in the water was considered as

the time for nucleation. The kinetics of the crystal

growth are deduced from the change of the degree

of supersaturation as function of the time from the

beginning of the crystal growth up to the moment

when pressure reaches approximately a constant

value. The half-decay time describes the time for

which the pressure has decreased 50% from the

total pressure.

IV.RESULTS AND DISCUSSION

1. Comparison of experimental data obtained with

methane and methane containing DME shows that

the addition of DME has a strong influence on the

rate of hydrate formation.

2. For the case of LPG containing DME the result

shows that DME was acted as an inhibitor.

Therefore, DME can be used as a promoter for

methane hydrate and an inhibitor for LPG hydrate.

ACKNOWLEDGEMENT

This project was funded by KOGAS through the

2011 university co-work program. The author is

grateful to KOGAS for the permission to present

this paper in UKC2012.

Synthesis of Ultra-long Hollow Chalcogenide Nanofibers for Thermoelectric Applications

Miluo Zhang

Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA 92521, USA

mzhan006@ucr.edu

Hosik Park Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA 92521, USA

phosik88@gmail.com

Nosang V. Myung Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA 92521, USA

myung@engr.ucr.edu

SUMMARY

In this work, various binary and ternary

chalcogenides including Bi2Se3, PbSe, PbTe,

Sb2Se3, Sb2Te3, and AgPbSe hollow nanofibers

with controlled size, composition and crystal

structure have been successfully synthesized. The

structure-property relationship of the chalcogenide

nanofibers, such as electric, optical, and TE

properties were investigated and evaluated for

enhancement of TE applications.

I. INTRODUCTION

Nanoengineered thermoelectric (TE) materials have received a great attention because of the potential improvements in the thermoelectric figure of merit (ZT), due to the classical and quantum mechanical size effects on electrons and phonons that provide additional mechanisms to enhance TE properties. The achievement of thermoelectric ZT of ~2–3 in painstakingly grown two-dimensional (2-D) nanostructures has been experimentally proved while a ZT exceeding 5 was theoretically predicted in one-dimensional (1-D) nanostructures.

1 In the

design of TE materials, nanotubes offer an additional degree of freedom compared to other 1-D nanostructures because the wall-thickness can be controlled in addition to length and diameter. Changes in wall-thickness are expected to strongly alter the electrical and phonon transport properties and thereby enhance the overall TE properties.

2

While several techniques exist for creating 1-D nanostructures, electrospinning (ES) has emerged as most versatile, scalable, and cost-effective method to synthesize ultra-long nanofibers with controlled diameter and composition. Although various nanofibers including polymers, carbon, ceramics and metals have been synthesized using direct electrospinning or through post-spinning processes, limited works were reported on the compound semiconducting nanofibers because of incompatibility of precursors. Therefore, a novel

approach has been developed that combine ES, galvanic displacement reaction (GDR) and cation exchange reaction (CER) to demonstrate cost-effective high through put fabrication of ultra-long hollow chalcogenide nanofibers for TE. The procedure exploited electrospinning to fabricate ultra-long Ni and Co nanofibers as sacrificial materials with controlled dimensions, morphology, and crystal structures, providing a large material database to tune redox potentials, thereby imparting control over the composition and shape of the nanostructures evolved during GDR. A CER was applied for the fabrication of ternary chalcogenide materials with preserved morphology and controlled composition. By using this approach, binary and ternary thermoelectric ultra-long hollow nanofibers including Bi2Se3, PbSe, PbTe, Sb2Se3, Sb2Te3, and AgPbSe were synthesized and their size, crystallinity, and composition dependent thermoelectric properties were systematically investigated.

Figure 1: TEM images of synthesized BixSe1-x hollow nanofibers

REFERENCES

1. Majumdar, A., Thermoelectricity in semiconductor nanostructures. Science 2004, 303, (5659), 777-778. 2. Zhou, G.; Li, L.; Li, G. H., Enhancement of thermoelectric figure of merit in bismuth nanotubes. Applied Physics Letters 2010, 97, (2).

Protein Engineering Using Non-Natural Amino Acids

Shun Zheng and Inchan Kwon*

University of Virginia, Charlottesville, VA, ik4t@virginia.edu

SUMMARY

Proteins consist of only twenty natural amino acid building blocks. Such a limited number of building blocks restrict possible set of proteins that can be designed. Therefore, non-natural amino acids can provide recombinant proteins chemical, physical, and biological properties that are not available in nature.

I. INTRODUCTION

Aminoacyl-tRNA synthetases (aaRSs) catalyze the aminoacylation reaction to establish the rules of genetic code. Precise manipulation of synthetase activity can alter the aminoacylation specificity to stably attach non-canonical amino acids into the intended tRNA. Subsequently by codon-anticodon interaction between message RNA (mRNA) and tRNA the amino acid analogs can be determined to deliver into a growing polypeptide chain. Thus introduction of non-natural amino acids into proteins in vivo relies heavily on manipulation of amino acid specificity of aaRS.

II. RESULTS and DISCUSSIONS The mutant phenylalanyl-tRNA synthetase (PheRS) from S. cerevisiae with a point mutation (T415G) in

the -subunit of the enzyme has been generated and characterized. Rationale for such a mutation is to create extra room to allow binding of bulkier amino acid substrates. The promiscuous substrate specificity of this mutant was extensively explored by ATP-PPi exchange assays in vitro. A broad activation profile toward many non-natural amino acids was observed. A phenylalanine auxotrophic E. coli strain transformed with this mutant synthetase and cognate suppressor tRNA enable the assignment of an amber nonsense codon to the amino acid tryptophan (Trp) or non-natural amino acids 3-(2-naphthyl)alanine. Further devised strains with phenylalanine, tryptophan double auxotroph or phenylalanine, tryptophan and lysine triple auxotroph outfitted with this pair of mutant synthetase and tRNA makes possible the efficient incorporation of p-bromophenylalanine (pBrF), p-idiophenylalanine (pIF), p-azidophenylalanine (pN3F), 3-(6-chloroindolyl)alanine (6BrW) and 3-(6-bromoindolyl)alanine (6ClW). Therefore, this variant

synthease and its cognate tRNA could serve as an additional 21

st pair for site-specific incorporation of

novel amino acid In the previous study, high fidelity incorporation of p-bromophenylalanine (pBrF) was hampered due to mischarging of the ytRNA

PheCUA

with natural amino acids, tryptophan (Trp) and lysine (Lys). We explored whether the ytRNA

PheCUA

and yPheRS can be re-designed to achieve high fidelity amber codon suppression with pBrF. Two different strategies have been applied to reduce the misincorporation of Trp and Lys, while retaining a high yield for protein synthesis. First, Lys misincorporation was eliminated by modification of the sequence of ytRNA

PheCUA in order to reduce

mischarging with Lys by E. coli lysyl-tRNA synthetase (eLysRS). Disruption of a Waston-Crick base-pairing between 30

th and 40

th bases in the

ytRNAPhe

CUA led to three-fold reduction in misacylation of Lys by eLysRS while also eliminating Lys misincorporation. Second, the binding site of yPheRS was rationally re-designed to enhance specificity for pBrF. Since the T415G mutation in yPheRS creates a large cavity that can accommodate the bulkier amino acid, Trp. The size of the cavity can be decreased by T415A mutation in yPheRS thus possibly reducing recognition of Trp. The yPheRS (T415A) variant showed five-fold higher activity for pBrF over Trp based on an ATP-PPi exchange. By combining mutant ytRNA

PheCUA

and yPheRS (T415A), pBrF was incorporated into murine dihydrofolate reductase in response to an amber codon with greater than 98% fidelity.

Multi-scale Modeling of Three-Phase System of Polymer Electrolyte Membrane Fuel Cell

Giuseppe F. Brunello, Ji Il Choi and Seung Soon Jang*

Georgia Institute of Technology Materials Science and Engineering

771 Ferst Drive NW, Atlanta, GA 30332 seungsoon.jang@mse.gatech.edu

SUMMARY

Using multi-scale atomistic modeling approach, we

modeled the three-phase system consisting of car-

bon support, Pt catalystic nanoparticle and polymer-

ic ionomer in cathode of polymer electrolyte mem-

brane fuel cell.

I. INTRODUCTION

We have simulated the three-phase systems

using multi-scale first-principles modeling approach

consisting of quantum mechanical density function-

al theory (DFT) and molecular dynamics (MD) simu-

lations in order to investigate the nanophase-

segregation of polymeric ionomers and water mole-

cules, surrounding Pt nanoparticle on graphitic car-

bon support. For this, we developed a force field

based on DFT computations and ran large-scale

MD simulations. Another topic we would like to ad-

dress is the Pt dissolution that degrades the fuel

cell performance by decreasing the active catalyst

surface area. In order to elucidate the Pt dissolution

mechanisms under a certain surface potential con-

dition, we implemented the DFT computation of var-

ious charged Pt surface in the presence of water.

II. DETAILS IN SIMULATION

Modeling of Three-Phase System. To achieve accurate analyses from the three-phase system, first, we built probable structures consisting of all the components in the simulated three-phase sys-tem. To prepare the accurate force field describing the molecular interactions between components in the three-phase system, we performed DFT compu-tations. Using the force field parameters based on the DFT computations, we built the three-phase systems with atomistic details as shown in Figure 1, showing nanophase-segregation of the polymeric ionomers and water molecules around Pt nanopar-ticle. The water phase should be very essential to transport the proton. We analyzed the distribution and transport of water, proton and oxygen in the

presence of Pt nanoparticle under various tempera-ture-pressure conditions.

water

H3O+ (160)

Sulfonate (160)

O2 (~30 out of 180)

Ionomer

Pt

Graphite

Figure 1. Three-phase system consists of Pt nanoparticle,

polymeric ionomer, and carbon support with other molec-

ular species such as water, proton and oxygen.

DFT Study on Pt Dissolution. Since it is known

that Pt catalyst particles in cathode are dissolved

under certain cathodic potentials, we investigated

the electrochemical stability of Pt nanoparticle un-

der various cathodic potentials using DFT computa-

tions with the double reference method suggested

by Filhol and Neurock [1] and the nudged elastic

band method [2-3]. We searched the transition state

and calculated the energy barrier for Pt dissolution

under a certain potential condition. Since the ener-

gy barrier changes as a function of potential, we

calculated the effect of potential on the rate con-

stant.

REFERENCES

[1] J.S Filhol, M.Neurock, Angew. Chem. Int. Ed. 45 (2006) 402. [2] D. Sheppard, R. Terrell, and G. Henkelman, J. Chem. Phys. 128, 134106 (2008).

Development of circulating fluidized bed reactor for the steam hydrogasification of low ranked fuel

Minyoung Yun

Center for Environmental Research and Technology University of

California, Riverside, USA 1084 Columbia Avenue

Riverside, CA 92507 myun002@ucr.edu

Dal Hee Bae Korea Institute of Energy Research

152 Gajeong-ro, Yuseong-gu Daejeon 305-343, Korea

dalbae@kier.re.kr

Chan S Park Center for Environmental Research

and Technology University of California, Riverside, USA

1084 Columbia Avenue Riverside, CA 92507 cspark@cert.ucr.edu

Joseph Norbeck Center for Environmental Research

and Technology University of California, Riverside, USA

1084 Columbia Avenue Riverside, CA 92507

Joe.norbeck@ucr.edu

SUMMARY

Application of circulating fluidization bed

technology to the SHR(Steam Hydrogasification

Reaction) of low rank fuel was investigated.

I. INTRODUCTION

Fluidization bed reactor is a popular technology

with several advantages. It has relatively high

reactivity by which solid feedstock are transformed

into fluid-like state through suspension in a reaction

gas. This technology has numerous applications in

the energy conversion process. Meanwhile, Steam

Hydrogasification Reaction (SHR) has been

developed by the Bourns College of Engineering -

Centre for Environmental Research and

Technology (CE-CERT). The SHR process has the

potential to generate synthetic or Substitute Natural

Gas (SNG) that can be used for electric power

generation and as an alternative transportation fuel

(e.g. Natural Gas Buses) by utilizing the use of low

ranked fuel such as lignite, biomass and municipal

waste.

II. EXPERIMENTAL

A cold reactor model of circulating fluidization

reactor consists of two separated reactors, which

are gasification reactor and thermal combustion

reactor, was designed and developed with

transparent acrylic material. With this configuration,

CO2 generated in the combustion reactor can be

easily captured; necessary heat for gasification

reaction can be provided by circulating sand.

Fluidization characteristics of solid particles used as

heat transfer medium between two reactors were

investigated. Loop seal design was optimized to

minimize the crosstalk of two fluidizing gases

between thermal gasification reactor and

combustion chamber, which is critical component

for the stable operation of the process.

I I I. RESULTS

Stable operation of reactor was achieved with

1-3 m/sec and 0.2 -1 m/sec of gas flow velocity in

the gasification reactor and thermal combustion

reactor respectively.

REFERENCES

1. Prabir basu, “Combustion and gasification in

fluidized beds”, pp. 59-101, 2006.

Programmable PLGA Microcapsules

Myung Han Lee University of Pennsylvania 220 S. 33

rd St. Towne M52

Philadelphia, PA 19104 myunghan76@gmail.com

Fuquan Tu University of Pennsylvania 220 S. 33

rd St. Towne M52

Philadelphia, PA 19104 tufq06@gmail.com

Daeyeon Lee University of Pennsylvania 220 S. 33

rd St. Towne 311A

Philadelphia, PA 19104 daeyeon@seas.upenn.edu

SUMMARY

We present the generation of near-infrared

(NIR)-sensitive microcapsules and demonstrate that

the release properties of these microcapsules can

be tailored by controlling their morphology.

I. INTRODUCTION

Hollow microcapsules containing an

aqueous core covered by a thin shell are useful for

encapsulating, protecting and delivering active

ingredients. In this study, we present the generation

of near-infrared-responsive PLGA microcapsules

with release properties that can be programmed by

controlling the morphology of the microcapsules.

II. Results and Discussion

A biocompatible polymer, poly(DL-lactic-co-

glycolic)acid (PLGA), is used to form hollow

microcapsules from monodisperse water-in-oil-in-

water (W/O/W) double emulsions1. Both the

composition of PLGA and the oil phase of W/O/W

double emulsions significantly influence the

morphology of the subsequently formed

microcapsules. PLGA microcapsules with vastly

different morphologies, from spherical to

“snowman-like” capsules, are obtained due to

changes in the solvent quality of the oil phase

during solvent removal. The adhesiveness of the

PLGA-laden interface plays a critical role in the

formation of snowman-like microcapsules.

NIR-sensitive PLGA microcapsules are

designed to have responsive properties by

incorporating gold nanorods into the microcapsule

shell, which enables the triggered release of

encapsulated materials. The effect of capsule

morphology on the NIR responsiveness and release

properties of PLGA microcapsules is demonstrated.

REFERENCES

1. M. H. Lee, K. C. Hribar, T. Brugarolas, N. P.

Kamat, J. A. Burdick, D. Lee*, “Programming the

Release Properties of PLGA Microcapsules by

Controlling Capsule Morphology”, Advanced

Functional Materials, 2012, 22, 131-138.

Polarity and Frequency Dependencies of Ta2O5 for EWOD Performance

Lian-Xin Huang UCLA MAE

420 Westwood Plaza, 37-129 ENG. IV, Los Angeles, CA, 90095

lhuangcoco@ucla.edu

Bonhye Koo UCLA CBE

420 Westwood Plaza, 7820 Boelter Hall, Los Angeles, CA, 90095

isler@ucla.edu

Chang-Jin “CJ” Kim UCLA MAE

420 Westwood Plaza, 37-124 ENG. IV, Los Angeles, CA, 90095

cjkim@ucla.edu

SUMMARY

We report that anodic tantalum pentoxide

(Ta2O5) as a dielectric material for electrowetting-

on-dielectric (EWOD) shows strong polarity and

frequency dependencies of the applied voltage.

I. INTRODUCTION

Ta2O5 has recently been reported as a superior

dielectric material for EWOD devices due to its high

permittivity and CMOS-compatible fabrication [1].

However, our study finds that the reported

superiority holds only when the EWOD voltage is

applied as negative DC or low frequency AC.

II. EXPERIMENT

A. Sample Fabrication

For a Ta2O5 EWOD device, tantalum was

sputtered on a glass microscope slide and anodized

to form Ta2O5 (200nm) on top. For a SiO2 EWOD

device, a silicon wafer was oxidized to form SiO2

(560nm). Cytop® (50nm) was spin-coated on both.

B. Experimental Procedure

A mixture of glycerin and KCl standard solution

(1:1) was used as a testing droplet (10μL). 2000

cycles of +DC (positive to the droplet), –DC, and

AC square wave were applied for long-term EWOD

actuation for a given electrowetting number

(Ew=0.31): 11.6V for Ta2O5 and 30V for SiO2

device.

III. RESULT

Figure 1 describes the contact angle changes

from the off state (without voltage) to the on state

(with voltage). It shows that long-term performance

slightly depends on polarity for the SiO2 devices;

the electrowetting effect decreases faster with +DC

than with –DC. However, this polarity dependence

is more dramatic for the Ta2O5 devices, i.e., no valid

data for +DC case due to electrolysis.

Figure 2 summarizes the contact angle

reduction for the (a) Ta2O5 and (b) SiO2 devices with

different AC frequencies: 50Hz, 100Hz, 250Hz, and

1kHz. For the Ta2O5 devices, long-term EWOD

performance decreased as frequency increases.

However, 50Hz and 1kHz didn’t show any clear

difference on SiO2 devices.

0 500 1000 1500 20000

2

4

6

8

10

12

14

16

18

Cycles

Co

nta

ct

An

gle

ch

an

ge, (

o)

-DC SiO2

-DC Ta2O

5

+DC SiO2

Fig 1. Contact angle reduction for Ta2O5 and SiO2

EWOD devices with different polarities.

0 500 1000 1500 2000-2

0

2

4

6

8

10

12

14

16

18

Cycles

Co

nta

ct

An

gle

ch

an

ge

, (

o)

50Hz

100Hz

250Hz

1kHz

(a) Ta2O5

0 500 1000 1500 2000

-2

0

2

4

6

8

10

12

14

16

18

Cycles

Co

nta

ct

An

gle

ch

an

ge

, (

o)

50Hz

1kHz

(b) SiO2

Fig 2. Contact angle reduction for a) Ta2O5 and b)

SiO2 EWOD devices with AC signals.

REFERENCES

1. Y. Li, W. Parkes, L.I., Haworth, A. Ross, J.

Stevenson, and A.J. Walton, "Room-Temperature

Fabrication of Anodic Tantalum Pentoxide for

Low-Voltage Electrowetting on Dielectric

(EWOD)," J. MEMS, 17(2008), pp.1481-1488.

Electrochemical Performance of Nano-sized LiFePO4 as Cathode Material for Li-ion batteries

Laura Kim

California Institute of Technology Caltech MSC 557

Pasadena CA, 91126 lkkim@caltech.edu

Hillary Smith California Institute of Technology

Caltech MC 138-78 Pasadena CA, 91126

hls@caltech.edu

Brent Fultz California Institute of Technology

Caltech MC-138-78 Pasadena CA, 91126

btf@caltech.edu

Lithium batteries are one of the most promising

energy storage technologies currently available, as

unmatched by any other energy storage devices in

energy density and performance. LiFePO4 has

attracted significant interest as a cathode material

for rechargeable lithium-ion batteries because it is

inexpensive, nontoxic, and made from naturally

occurring minerals. Improvements to the intrinsic

low electronic conductivity of LiFePO4 are sought by

reducing the particle size and coating the material

with carbon. We seek to understand the effect of

these modifications on the electrochemical

performance of these cathode materials. First, bulk

and nano-sized LiFePO4 were prepared by ball

milling with carbon black for 2 hours and 36 hours,

respectively. Then, the bulk and the nano-sized

materials were characterized by x-ray diffraction

(XRD) to determine particle size. Next, coin cells

were assembled in a glove box, and their

rechargeability and functionality were tested with an

Arbin cell cycler. Although it was hypothesized that

the nano-sample would perform better due to its

increased surface area and smaller travelling

distance for lithium ions, no significant difference

was observed in the Coulomb and energy

efficiencies of the bulk and nano-sized samples.

The nano materials exhibited a shorter voltage

plateau during discharge and the capacity faded

significantly with increasing cycling rate. Scanning

Electron Microscopy (SEM) images together with

the XRD results suggest that the nano material,

with smaller crystallites and larger surface area, did

not improve the movement of Li-ions through the

material and improve performance as expected

because the smaller crystallites were agglomerated

into particles equal to the particles in the bulk

material.

Figure 1. SEM images of bulk (top) and nano-

sized (bottom) LiFePO4 show that the nano-sized

crystallites in the have agglomerated into particles

approximately equal in size to the bulk particles.

Bulk x20k

Nano-sized x20k

Engineering of Saccharomyces cerevisiae for Enhanced Polyketide Production

Jin Wook Choi

University of California, Irvine Dept. of Chemical Engineering and

Materials Science choijw@uci.edu

Nancy A. Da Silva University of California, Irvine

Dept. of Chemical Engineering and Materials Science ndasilva@uci.edu

SUMMARY

The yeast Saccharomyces cerevisiae is a

promising host for the synthesis of fungal

polyketides and fatty acids. Using 6-methylsalicylic

acid (6-MSA) as a model polyketide, we have

studied the effects of host strain attributes and

precursor availability on product synthesis. Native

metabolic pathways in S. cerevisiae were up-

regulated or down-regulated to enhance precursor

production; these efforts led to up to 6.3-fold

increases in the specific 6-MSA level. Two promoter

systems with induction in different phases of growth

were studied and resulted in 26-fold differences in

the specific 6-MSA produced. The effects of the

strain and pathway manipulations on carbon

utilization were also characterized.

I. INTRODUCTION

Polyketides are molecules polymerized from

short chain carboxylic acids such as acetate,

propionate, malonate, and butyrate.1 The traditional

application is the development of commercial drugs

such as erythromycin and tetracycline, doxorubicin

and lovastatin.2 Another application is potential

platform for biorenewable chemical precursor

production. Carboxylic acids have emerged as a

potential platform chemical that can be achieved

through fatty acid synthases. Molecules with ring

structures can also be achieved through polyketide

synthases.

Native polyketide producing organisms are

difficult to use due to poor growth and lack of tools

for genetic modification. Thus, well developed

microorganisms such as Escherichia coli and S.

cerevisiae have been employed to produce

polyketides. S. cerevisiae is a promising host for

the production of short chain fatty acids;

dihydromonacolin L (DML), which is a lovastatin

precursor; 6-MSA; and the pyrone triacetic acid

lactone (TAL).

II. RESULTS

A. PGK1 promoter-based 6-MSA synthesis system

The genes ACS1 and ACC1 were individually

or simultaneously overexpressed under the PGK1

promoter together with 6-MSAS. ACS1 and ACC1

individual overexpression led to 1.8-fold and 2.2-

fold increase in specific 6-MSA synthesis,

respectively, and their simultaneous overexpression

led to a 6.3-fold increase, relative to the wild type.

B. ADH2 promoter-based 6-MSA synthesis system

The genes ACS1 and ACC1 were individually

overexpressed under the ADH2 promoter along

with 6MSAS. ACC1 overexpression showed only a

slightly increased 6-MSA synthesis. However, the

ADH2 promoter-based strain produced 26-fold

more 6-MSA (per cell) than the PGK1 promoter-

based strains.

C. Polyketide synthesis in protease deficient strain

S. cerevisiae strain BJ5464 lacks two proteases,

PrA and PrB. 6-MSA synthesis in this strain led to

1.4-fold increase in specific 6-MSA level relative to

BY4741, which has the proteases intact. The

synthesis of TAL in a protease deficient strain led to

a 1.6-fold increase relative to BY4741.

REFERENCES

1. Carreras, C. W.; Pieper, R.; Khosla, C., The chemistry and biology of fatty acid, polyketide, and nonribosomal peptide biosynthesis. In Bioorganic Chemistry Deoxysugars, Polyketides and Related Classes: Synthesis, Biosynthesis, Enzymes, 1997; Vol. 188, pp 85-126. 2. Panagiotou, G.; Andersen, M. R.; Grotkjaer, T.; Regueira, T. B.; Nielsen, J.; Olsson, L., Studies of the Production of Fungal Polyketides in Aspergillus nidulans by Using Systems Biology Tools. Applied and Environmental Microbiology 2009, 75 (7), 2212-2220.

Ultrafast Nanoscale Gas Sensors Based on Schottky Barriers

Lauren L. Brooks Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA, 92521, USA

lbrooks@engr.ucr.edu

Miluo Zhang Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA, 92521, USA

mzhan006@ucr.edu

Nosang V. Myung* Department of Chemical and Environmental Engineering,

University of California-Riverside, Riverside, CA, 92521, USA

myung@engr.ucr.edu

SUMMARY

One-dimensional nanoscale gas sensors have

been fabricated in order to optimize the optimize

sensor performance for a specific target gas. This

has been achieved through the selection of the

electrode material. In addition, the contacts

between the transducer and electrodes have been

designed to induce Schottky behavior, which also

enhances the sensor performance.

INTRODUCTION

Gas sensors are finding wide applications in

fields as diverse as human workplace monitoring,

environmental protection, military weapons

detection, biosensing, and many others. Much work

is being done to fabricate sensors on a single chip

that are sensitive, selective, durable, and have

small response and recovery times.1 Many different

materials have been tried to fabricate better

sensors, including metals, metal oxides,

nanomaterials, DNA, and ceramics. Single walled

carbon nanotubes (CNTs) are finding wide

acceptance for use as transducers in gas sensors

because of their large surface area to volume ratio,

excellent electronic properties and stability in

ambient conditions. Various metal electrodes and

dopants on the CNTs have been proposed to

enhance the sensor’s response to different gases

and its response and recovery times. The sensing

mechanism can come from ion gating along the

nanotube or from the contact at the metal

electrode/CNT interface. Schottky barrier, formed at

the contact interface from the different energy levels

of the materials, can control the sensor response.

The mechanism of Schottky barrier is still not well

understood, nor is it easy to control their formation

on gas sensors during fabrication. Gas sensors

based dominated by Schottky barriers are desirable

because they exhibit larger responses to analyte

gases and faster response times after gas exposure.

For this work, we synthesized an array of

electrodes on a silicon chip. On each chip, the

electrodes were fabricated with a chosen metal,

such as Pt, Pd, Ni, Cr and Au. CNTs were aligned

across each electrode gap by dielectrophoresis

(DEP), a quick and simple method that can be done

at ambient conditions and easily scaled up for mass

production. The performance of the sensors was

tested in various target gases such as H2, NOX, NH3,

H2S and H2O. The performance of each type of

sensor at various gas concentrations was

compared, looking for Schottky behavior from the

response level and the response time of each

sensor.

Figure 1: Sensing Responses of Pt, Pd, Ni, Au & Cr

Electrodes to NOX, H2, H2S, NH3 & H2O at OSHA

Permissible Exposure Level (PEL) Concentrations

REFERENCES

1. T. Hübert, L. Boon-Brett, G. Black, U. Banach,

“Hydrogen sensors – A review,” Sensors and

Actuators B: Chemical, Vol. 157, No. 2, pp. 329-

352, October 2011.

Role of Solution Chemistry on the Interaction between Bubbles and Oxide Minerals

Hyunjung Kim

Department of Mineral Resources and Energy Engineering

Chonbuk National University Jeonju, South Korea kshjkim@jbnu.ac.kr

Woori Chae Department of Mineral Resources

and Energy Engineering Chonbuk National University

Jeonju, South Korea gikimi85@naver.com

Junhyun Choi Department of Mineral Resources

and Energy Engineering Chonbuk National University

Jeonju, South Korea anar3092@naver.com

SUMMARY

The influence of solution ionic strength and electrolyte valence on the flotation behavior of malachite, which is one of the copper-containing minerals, has been investigated in well-controlled Hallimond tube experiments. The microflotation tests were carefully conducted over a range of solution ionic strength (IS) (1–300 mM) at a constant speed, pH (pH=9.5), flotation time (10 min),

and collector (sodium oleate) dosage (210-6

moles/g). The size of malachite for this experiment ranged from 45 to 53 μm, and two different types of electrolytes (NaCl and CaCl2) were employed for this study. In order to complement the flotation results, several characterization experiments (e.g., electrophoretic mobility, hydrophobicity tests) were also carried out over the same IS range employed in the microflotation study. Overall, strong coupled effect of solution IS and ion valence was observed (Figure 1). Specifically, the flotability of malachite increased with increasing IS in the presence of monovalent cations (Na

+) while the flotability

increased up to 30 mM and decreased with increasing IS in the presence of divalent cations (Ca

2+) (Figure 1). Furthermore, the flotability of

malachite was greater with the presence of Na+

compared with Ca2+

under low IS conditions while opposite trend was observed under high IS conditions (Figure 1). The results for electrophoretic mobility measurements showed that malachite was negatively charged in NaCl solution over the entire IS investigated while positively charged in CaCl2 solution, indicating that specific adsorption of Ca

2+

ions onto the surface of malachite occurred in CaCl2 solution and electrostatic interaction between malachite and bubble is expected to be repulsive and attractive in NaCl and CaCl2 solution, respectively. The characterization and flotation results to date suggest that the enhanced flotability in the presence of Ca

2+ at low IS was attributed to

the enhanced electrostatic attractive force between malachite and bubble, which is consistent with the extended Derjaguin-Landau-Verwey-Overbeek

(XDLVO) prediction. At high IS, however, the flotation behavior of malachite in the presence of Ca

2+ did not follow the XDLVO prediction, indicating

that additional non-DLVO type interactions are likely involved in this phenomenon. Plausible mechanisms for the distinct difference in the flotation behavior of malachite with the presence of Na

+ and Ca

2+ will be further discussed in this

presentation.

1 10 100 1000

Ionic Strength (mM)

20

40

60

80

100F

lota

bil

ity (

%)

CaCl2

NaCl

Figure 1: Flotation efficiency of oxide copper

mineral (malachite) at different ionic strengths. The

concentration of sodium oleate was 210-6

moles/g

and the experiments were carried out at pH 9.5.

ACKNOWLEDGMENTS

This work was supported by the Basic Science

Research Programs through the National

Research Foundation of Korea (NRF) funded by

the Ministry of Education, Science and

Technology (NRF-2011-0014627).

Sorption Enhanced Steam Hydrogasification of Coal for Self-sustained Hydrogen Supply and In Situ Removal of CO2

Chan Seung Park

CE-CERT University of California, Riverside

cspark@cert.ucr.edu

Zhongzhe Liu Center for Environmental Research

and Technology University of California, Riverside

Joe Norbeck Center for Environmental Research

and Technology University of California, Riverside

SUMMARY

The in situ removal of CO2 and the

enhancement of the energetic gas yield including

hydrogen and methane by sorption enhanced

steam hydrogasification (SE-SHR) process were

investigated.

I. INTRODUCTION

Figure 1 shows the block flow diagram of the

process. Lignite was used in this study as the

feedstock for steam hydrogasification reaction

(SHR) with the addition of calcined dolomite as

sorbent. CO2 was almost reduced to zero with the

introduction of the sorbent into the reactor. The

production of hydrogen and methane was increased

simultaneously. The hydrogen yield was augmented

by 60% when the mass ratio of sorbent to coal was

increased to 3 as compared with the SHR without

sorbent. The hydrogen in the product gas was

sufficient to maintain a self-sustained supply back

to the SHR when the sorbent/coal mass ratio was

over 1. The sorption enhanced performance was

determined at different temperatures ranging from

650°C to 800°C. SE-SHR also showed better

performance than sorption enhanced

hydrogasification (SE-HG).

Figure 1: Block Flow Diagram of Sorption

Enhanced Steam Hydrogasification Process

II. Result and Discussion

The main conclusion of this study is that the

overall performance of the SE-SHR was

substantially improved compared to the

conventional operation of the SHR. Figure 2 shows

the increase of gas production by increase of

sorbent loading.

Figure 2, Comparison on Product gas yield

In summary, SE-SHR process shows;

1) The production of H2 and CH4 was

increased

2) CO2 emission was mitigated dramatically

3) H2 was enough for self-sustained supply with

certain amount of sorbent loaded

4) The overall performance of SE-SHR was

better than SHR and SE-HG.

MoO2-Based Direct Liquid Fuel Solid Oxide Fuel Cell (SOFC)

Byeong Wan Kwon Washington State University

Dana Hall 118 Pullman, WA 99164

bkwon@wsu.edu

Grant Norton Washington State University

Dana 239D Pullman, WA 99164

mg_norton@wsu.edu

Su Ha Washington State University

Dana Hall 118 Pullman, WA 99164

suha@wsu.edu

SUMMARY

The present paper describes the fabrication and

performance of a porous molybdenum dioxide

(MoO2)-based anode for direct liquid fuel solid oxide

fuel cells (SOFCs), which can directly convert liquid

fuels into electrical energy without external fuel

processors.

I. INTRODUCTION

A significant advantage of direct liquid fuel

SOFCs where the fuel is directly fed into the anode

is the simplicity afforded by not having to externally

reform the fuel. Ni-based anodes are commonly

used for SOFCs. However, the major

disadvantages of Ni-based anodes are severe coke

formation and low sulfur tolerance. Excessive coke

formation on the anode leads to rapid deactivation

of the cell by physically blocking the catalyst

surface from the reactants. Similar to the problem

with coking, sulfur compounds present in fossil-

based liquid fuels also can quickly deactivate the

cell by forming nickel sulfide on the surface [1]. MoO2-based anode has many unique material and

catalytic properties that could be used as a novel

anode material for direct liquid fuel SOFCs and

mitigate the coking and sulfur poisoning issues of

existing Ni-based anode. The aim of this research

was to investigate the initial performance and long-

term stability of MoO2-based SOFCs using various

liquid fuels operating under the direct liquid fuel

SOFC mode. The results were compared with

commercial Ni-based SOFCs. The spent cells were

characterized using various analytical techniques

including scanning electron microscopy (SEM) with

energy dispersive X-ray analysis (EDX) and X-ray

diffraction (XRD).

II. Results

The MoO2-based anode was fabricated onto

yttria-stabilized zirconia (YSZ) electrolyte via

combined electrostatic spray deposition (ESD) and

direct painting methods. The cell performance was

measured by directly feeding liquid fuels such as n-

dodecane (i.e., a model diesel/kerosene fuel) to the

MoO2-based anode at 750oC. The stabilized power

densities from our MoO2-based SOFC were 2000

mW/cm2 at 0.6V. To test the long-term stability of

MoO2-based SOFC against coking, n-dodecane

was continuously fed into the cell for 24 h at its

open cell potential of ~0.86V (See Figure 1). During

this long-term testing, voltage-current density plots

were periodically obtained and they showed no

significant changes over 24 hr.

MoO2-Based SOFC

Ni-Based SOFC

e-

O2-

Anode

Electrolyte

cathode

H2O + CO2Biofuel

O2

e-

e-

e-

O2-

Anode

Electrolyte

cathode

H2O + CO2Biofuel

O2

e-

e-

Liquid Fuel

Mixture

Ni-Based Anode MoO2-Based Anode

Conventional

Ni-Based SOFC

WSU’s

MoO2-Based SOFC

Coke

Layer

No Coking!!!

MoO2-Based

Anode

YSZ

Electrolyte100 m

Cross Sectional

Image of SOFCH2O, CO2, etc.

At 850 oC

Figure 1: Plot of open cell potential as a function of

operation time for the Ni-based and MoO2-based

SOFCs using n-dodecane, air and CO2 mixtures as

a fuel at 850oC [2].

REFERENCES

1. R.J. Gorte and J.M. Vohs, “Novel SOFC anodes

for the direct electrochemical oxidation of

hydrocarbons,” Journal of Catalysis, Vol. 216,

No. 1-2, pp. 477-486, 2003.

2. B.W. Kwon, C. Ellefson, M.G. Norton, S. Ha,

“Molybdenum Dioxide-Based Anode for Direct

Liquid Fuel SOFC Applications,” Applied

Catalysis B: Environmental, Submitted in May,

2012.

Preparation of an Abstract in Two-Column Format for UKC

Casey Galvin North Carolina State University

Department of Chem. Engineering Raleigh, NC

cjgalvin@ncsu.edu

Jan Genzer North Carolina State University

Department of Chem. Engineering Raleigh, NC

jgenzer@ncsu.edu

SUMMARY

The Genzer group conducts research focused

on modification of surface properties using small

molecules and polymers, in particular polymer

brushes. This poster highlights the use of

organosilane molecules to introduce various

functional groups onto a surface through a vapor

phase deposition process. Homogeneous coatings

or gradient coatings can be easily created. Further

modification of the grafted molecules enables

tuning surface properties for a variety of

applications.

I. INTRODUCTION

We have worked to develop a versatile, facile, low-

cost procedure to introduce functional groups onto

solid surfaces by depositing organosilane (OS)

molecules from the vapor phase. This approach

takes advantage of vapor phase diffusion of OS

molecules from a reservoir to create a

concentration gradient, which translates to a

functional gradient on the substrate surface. Figure

1 illustrates the process. This process requires no

special equipment, can be carried out under

ambient conditions and can proceed to completion

on the order of minutes.

We have successfully produced homogeneous and

gradient surfaces with vinyl, primary and tertiary

amine, halogen and methyl functional groups using

trichlorosilanes and alkoxysilanes. We demonstrate

the versatility of these functional groups by using

post-deposition modification reactions to

incorporate fluorinated, zwitterionic and azide

species. Zwitterionic compounds have received

attention recently for their anti-fouling properties,

and the azide species is open for further reactions

using popular “click” reactions. All of these

compounds are commercially available, and the

reactions proceed under mild conditions.

Figure 1