SOUTHWEST CATALYSIS SOCIETY - Semantic Scholar · 2:00 PM Paul Barger, UOP LLC, a Honeywell Company...
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SOUTHWEST CATALYSIS SOCIETY 2014 SPRING SYMPOSIUM Friday, April 25, 2014 *Engineering Building 1 Room L2D2 University of Houston, Houston, TX Meeting sponsors:
Transcript of SOUTHWEST CATALYSIS SOCIETY - Semantic Scholar · 2:00 PM Paul Barger, UOP LLC, a Honeywell Company...
SOUTHWEST CATALYSIS SOCIETY
2014 SPRING SYMPOSIUM
Friday, April 25, 2014
*Engineering Building 1 Room L2D2
University of Houston, Houston, TX
Meeting sponsors:
Chair Bert Chandler
Trinity University Department of Chemistry
San Antonio, TX 78212 [email protected]
Chair-Elect Daniel Shantz
SABIC Technology Center 1600 Industrial Blvd
Sugar Land, TX 77478 [email protected]
Past-Chair Andy Moreland
Valero Energy Corporation San Antonio, TX [email protected]
Secretary
Kerry Dooley Cain Chemical Engineering Dept. Louisiana State University
Baton Rouge, LA 70803 [email protected]
Treasurer Victor Johnston
Celanese 9502 Bayport Road
Pasadena, TX 77057 [email protected]
Directors Jeff Rimer
Department of Chemical & Biomolecular Engineering
University of Houston Houston, TX 77204-4004 [email protected]
John W. Novak, Jr.
Pacific Industrial Development Corp.
18310 Old Trace Drive
Baton Rouge, LA 70817 [email protected]
Teng Xu
ExxonMobil Chemical 4500 Bayway Drive Baytown, Texas 77520
NACS Representative Mike Reynolds Shell International Exploration and
Production 3333 Highway 6 South
Houston, TX 77082 [email protected]
The SWCS officers and I welcome you to the 2014 SWCS Spring Symposium, Friday, April 25, 2014, at the University of Houston in the Engineering Building 1, Room L2D2 (building #580 on the University of Houston map on the back page). We are delighted to present 6 invited speakers and 31 poster presentations for this year’s meeting. Meritorious posters presented by students and post-docs will be identified with Best Poster Awards, carrying cash prizes. The 2014 Spring Symposium registration fee is $50, which includes North American Catalysis Society and SWCS annual membership dues, along with coffee/snack breaks. To speed registration, provide your business card along with your registration fee. You can also pre-register on-line through our pay-pal account We will be able to accept credit cards (Visa, MasterCard, Discover, and American Express) for the registration fee or corporate donations. Credit card receipts will be sent via e-mail, so please be prepared to input your e-mail address into our system when you pay. But note, that checks are faster (especially if you have them ready to go). We will also continue to accept cash. If you have colleagues who cannot attend the Symposium, please forward this program to them and let know they can mail their membership dues ($50) to our Treasurer, Victor Johnston (mailing address shown at left). Checks should be made out to SWCS. The student registration fee is $10, which includes NACS and SWCS membership. PARKING: The best place to park is in garage marked on the map (last page), 4400 University. You will need a credit card to enter. We will have parking coupons available for drivers of cars to exit the garage for free. You will input the coupon upon exiting, then run your credit card, which will not be charged.
We hope you enjoy the symposium! Bert Chandler Trinity University Chair
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2014 PROGRAM
All talks & breaks will be held in Engineering Building 1, Room L2D2
7:30 AM Registration – Victor Johnston, Treasurer (& helpers)
8:25 AM Welcoming Remarks – Bert Chandler, Chair
8:30 AM Steven Crossley, School of Chemical, Biological and Materials Engineering,
University of Oklahoma “Catalytic conversion of biomass to fuels: Active sites
required for the conversion of light acids and phenolics”
9:15 AM Patrick Brant, Exxon Mobil Chemicals “Innovations in Olefin Polymerization
Catalysis: From Natural Gas to Metallocenes”
10:00 AM Coffee Break and poster session
11:00 AM Rob Rioux, Department of Chemical Engineering, Pennsylvania State University,
“Single Molecule Investigations of Heterogeneous Catalysts: Probing Solvent Effects,
Active Site Heterogeneity and [possibly] Adsorbate Dynamics”
11:45 AM Christopher Jones, (Emmett Award Winner), Department of Chemical and
Biomolecular Engineering, Georgia Institute of Technology, “Amine-Modified
Silicates as Supports and Catalysts”
12:30 PM Lunch Break – on your own (map with options on last page)
1:45 PM Southwest Catalysis Society Excellence in Applied Catalysis Award
Dr. Heiko Weiner, Celanese, for contributions to Celanese’s TCX® Ethanol
Technology Commercialization
2:00 PM Paul Barger, UOP LLC, a Honeywell Company (F. G. Ciapetta Lectureship), Des
Plaines, IL, “UOP Advanced MTO Technology – A New Route for the Production of
Light Olefins”
2:45 PM Charlie Campbell (Burwell Lectureship), Departments of Chemistry and Chemical
Engineering, University of Washington “Supported Metal Nanoparticles:
Correlating Structure with Catalytic Function via Metal Atom Energetics”
3:30 PM Poster Awards and SWCS Business Meeting
In Engineering building 1
3:45 PM Adjourn
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Catalytic Conversion of Biomass to Fuels: Active Sites Required for the Conversion of Light Acids and Phenolics
Steven P. Crossley
Assistant Professor of Chemical, Biological, and Materials Engineering
University of Oklahoma
The thermochemical conversion of biomass to liquids through pyrolysis and
torrefaction is a promising approach to ultimately produce fuels and chemicals. The
critical challenge lies in the subsequent catalytic upgrading. Ongoing efforts at the
University of Oklahoma aim to separate the biomass into fractions rich in families of compounds such as
light oxygenates, furanics, and phenolics. Two families of catalysts that have shown considerable promise
for the catalytic upgrading of these families of oxygenates are metals supported on reducible oxides and
zeolites. In this contribution we will demonstrate the conversion of corrosive acetic acid to the chemical
building block acetone over zeolites with high selectivity. The mechanism of conversion of light
carboxylic acids over zeolites is contrasted to the mechanism observed over reducible oxides. The role of
the proximity of active sites as well as co-fed water on the mechanism and product selectivity will be
discussed. These findings will then be extended to help explain products and deactivation rates zeolites in
the presence of real pyrolysis oil vapors.
In addition, the nature of the catalytically active site required for the conversion of phenolics over metals
supported on reducible oxides, for example Ru/TiO2 or Ni/CeZrOx, is not well understood. By
systematically varying catalyst properties, we demonstrate that the active sites responsible for the
conversion of methoxy groups of phenolic species are due to surface defects on the reducible oxide, rather
than the perimeter surrounding the metal. The importance of the metal on enhancing the activity of the
reducible oxide for this reaction is dependent on the reducibility of the oxide itself. The introduction of
additional compounds present in the pyrolysis vapors, such as furanics and light oxygenates, compete for
adsorption sites on both the metal and reducible oxides to varying extents resulting in significant shifts in
product selectivity.
Innovation in Olefin Polymerization Catalysis: From Natural Gas to Metallocenes
Patrick Brant
Chief Polymer Science Advisor
Exxon Mobil Chemicals
Polyolefins - polyethylene, polypropylene, and smaller volume products such as
plastomers and ethylene-propylene rubber – are one of the great success stories in the
world today. Along with cement, steel, wood, and glass, for example, these are one
of the key building blocks in a growing array of applications. This class of polymers is so successful
because, like cement, steel, and glass, they are remarkably versatile providing solutions that deliver lowest
cost, enhanced convenience, and a host of other benefits in an expanding array of markets. Their
versatility in turn arises from molecular structures can be increasingly manipulated in a nearly surgical
manner to deliver greater performance while spurring and benefiting from innovations that reduce
production and fabrication costs. In this talk, we will look in particular at the contributions of shale gas
and metallocene catalysis to the growth and future prospects of polyolefins. Examples of enhanced
product performance through the design of metallocene catalysts, harnessing their deployment in
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commercial reactors, and controlling polymer structure will be provided. Opportunities for continuing
advancement of polyolefin performance through catalyst design and discovery will be considered.
Single Molecule Investigations of Heterogeneous Catalysts: Probing Solvent Effects, Active Site Heterogeneity and [possibly] Adsorbate Dynamics
Robert M. Rioux
Friedrich G. Helfferich Assistant Professor of Chemical Engineering
Pennsylvania State University
Metal nanoparticles are key components in the advancement of future energy
technologies since they are catalytically active for several organic-inorganic
syntheses, electron-transfer, and energy conversion reactions. They directly promote chemical conversion
and/or facilitate chemical transport to active interfaces. A detailed understanding of the relation between
structure and properties of nanoparticles will lead to tailored catalytic properties. Although these
structure-function relationships are pursued by many researchers; they are typically limited to ensemble-
level approaches where the intrinsic catalytic behavior of individuals is masked due to the asynchronicity
of their behaviors during catalytic turnover. We employ a single molecule approach utilizing a two-state
(pro-fluorescent to fluorescent) reduction reaction to examine the catalytic behavior of individual Au
nanoparticles with single turnover resolution. Through kinetic modeling and isotopic labeling, we
demonstrate competitive binding between solvent and substrate accounts for differences in observed
catalytic rates at the ensemble level. Temperature-dependent measurements of the catalytic activity of
single nanoparticles reveals heterogeneous in reactivity and kinetic parameters which are due to static
dispersion even though the dispersion varies temporally; these variations are ascribed to the intrinsic
reactivity of populations of indistinguishable active sites. Approaches to selectively titrate distinct active
site populations on the surface of individual Au nanoparticles have enabled us to distinguish between their
intrinsic kinetic behavior and utilizing ideal models of nanoparticle structures confirm their identity and
concentration. The ability to probe reaction dynamics during single molecule catalysis studies utilizing an
experimental and theoretical approach to understand delayed rise times in fluorescent response will be
discussed.
Amine-Modified Silicates as Supports and Catalysts
Christopher W. Jones (Emmett Award Winner)
New Vision Professor of Chemical and Biomolecular Engineering
School of Chemical & Biomolecular Engineering
Georgia Institute of Technology
Amine modified porous silicates are highly versatile materials. We have explored
synthesis-structure-property relationships for these materials in the separation of organic species from gas
or liquid phases, as well as for CO2 capture. In this work, I will relate our recent endeavors in the design
and application of porous silicate supported amines in catalysis. Both well-defined molecular amines and
polymeric amines grafted to silicate surfaces will be described. Catalysts based on discrete molecular
amines that act as basic sites and polymeric amines that cap and modify the reactivity of metal
nanoparticles will be described in reactions of importance in synthetic organic chemistry.
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Southwest Catalysis Society Excellence in Applied Catalysis Award Heiko Weiner, Celanese Chemicals
UOP Advanced MTO Technology – A New Route for the Production of Light Olefins
Paul T. Barger (F. G. Ciapetta Lectureship) Section Head – Catalyst Manufacturing Support
UOP LLC, a Honeywell Company
The UOP Advanced Methanol-to-Olefins (MTO) Technology combines the
UOP/Hydro MTO process for the conversion of methanol to light olefins with the
Total Petrochemicals/UOP Olefin Cracking Process (OCP) to convert C4+ by-products
into additional ethylene and propylene. The overall process provides a cost-
advantaged route for the utilization of natural gas, coal or biomass to produce these high volume
petrochemicals. Fundamental understanding of catalyst structure-performance relationships and the MTO
reaction mechanism have guided the development of this technology. The integration of the MTO and
OCP processes provides close to 90% overall carbon selectivity to ethylene and propylene from methanol.
Recent progress in the commercialization of this technology will also be reviewed.
*Grace Davison is gratefully acknowledged for sponsoring the Ciapetta Lectureship
Supported Metal Nanoparticles: Correlating Structure with Catalytic Function via Metal Atom Energetics
Charles T. Campbell (Burwell Lectureship)
Rabinovitch Endowed Chair of Chemistry
Departments of Chemistry and Chemical Engineering
University of Washington
Many important catalysts for energy and environmental technologies
involve late transition metal nanoparticles dispersed across the surface of
some support material. The relationships between the energetic stability of late transition metal particles
on oxide supports and their structural, electronic, chemisorption and catalytic properties will be examined.
Oxide-supported metal catalysts have been studied using well-defined surfaces involving vapor-deposited
metals on single-crystal oxide surfaces, where the metal atoms nucleate and grow nanoparticles. The
energetic stability of the metal atoms in these nanoparticles has been measured as a detailed function of
particle size and support properties using metal atom adsorption calorimetry. The small-molecule
chemisorption properties and sintering kinetics of these metal particles have also been measured. Trends
in adsorption and metal / oxide adhesion energies will be reviewed. We find correlations amongst the
energy of the metal atoms in these nanoparticles (i.e., their chemical potential, which depends both on
their particle size their oxide support) and the strength with which they bond adsorbates, their catalytic
kinetics and their sintering rates.
*Johnson Matthey is gratefully acknowledged for sponsoring the Burwell Lectureship
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POSTER ABSTRACTS
1. Study of Cobalt Copper nanoparticle as catalysts for ethanol synthesis from syngas
Zi Wang, James Spivey
Cain Department of Chemical Engineering, Louisiana State University, 110 Chemical Engineering, South
Stadium Rd, Baton Rouge, LA 70803. Email: [email protected]
This study uses microemulsion method to synthesize Cobalt and Copper composite catalysts for syngas to
ethanol reaction. The effective site pairs for this mechanism are Cobalt and Copper metal with intimate contact.
The catalyst is characterized by H2 Temperature programmed reduction to study its reduction behavior. X-ray
photoelectron spectroscopy is tested to determine the oxide phases of cobalt and copper composite.
Transmission Electron Microscopy is used to observe the structure of the catalyst. The catalyst is reduced at
400 °C in H2/He flow for three hours before reaction. After reduction, the reactor is pressurized to 40 bar and
the temperature increases to 270 °C. Syngas with certain H2 to CO ratio (H2:CO=2:1) flows inside the reactor
and catalytically converts to ethanol and other side products. The conversion is kept below 1% and the product
is analyzed by a Shimadzu GC-2014 Gas chromatograph. The result reveals that the interactions between
copper and cobalt are enhanced. Therefore more effective sites for ethanol formation are synthesized, which
yields to higher ethanol selectivity than other bulk catalysts.
2. The Effects of Surface Hydroxyl and Oxygen Species on the Partial Oxidation of Allylic Alcohols on
Au(111)
Gregory M. Mullen,1 Liang Zhang,
2 Edward J. Evans Jr.,
2 Ting Yan,
2 Graeme Henkelman,
2 and C. Buddie
Mullins1,2,
*
McKetta Department of Chemical Engineering1 and Department of Chemistry,
2 Center for Nano and Molecular
Science and Technology, Texas Materials Institute, and Center for Electrochemistry, University of Texas at
Austin, Austin, Texas 78712-0231, United States. Email: [email protected]
In this study, we explored the partial oxidation of allylic alcohols on the Au(111) surface precovered with
atomic oxygen and hydroxyl species via temperature programmed desorption and density functional theory
methods. We found that these processes can occur via multiple pathways, dictated by the relative composition
of surface intermediate species. All pathways proceed through alkoxide intermediates. Dehydrogenation of the
alkoxide is the rate-limiting step of the partial oxidation process. This step can be promoted by both oxygen
atoms and hydroxyl species. Hydroxyl species promote this reaction with nearly 100% selectivity towards
partial the partial oxidation product, whereas, oxygen atoms can promote both partial oxidation and combustion
pathways.
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3. Methane Oxidation at Low Temperature over Metal/Metal Oxide Supports
Munish K. Sharma, Michael P. Harold, William S. Epling*
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Rd, Houston,
TX 77004. Email: [email protected]
Methane oxidation is of great scientific interest as a method to control the increasing methane gas emissions.
Methane gas is a potent greenhouse gas which is 20 times stronger than CO2. This study focuses on exploring
the effect of noble/transition metals such as palladium (Pd), platinum (Pt), rhenium (Re), iron (Fe) etc. on metal
oxide supports ϒ-Al2O3, CeO2, ZrO2. Catalysts were prepared using incipient wetness impregnation method
(IMP) and calcined at 500oC for 4 hrs. Temperature programmed oxidation (TPO) activity tests were conducted
inside a 4 mm ID quartz tubular reactor in the temperature range of 25oC – 500
oC. Catalyst screening
experiments with multiple heating-cooling cycles were performed and were compared for activity against 1
wt% Pd/ϒ-Al2O3 catalyst. A conversion of 89 % in dry feed was observed for bimetallic Pd-Pt supported on ϒ-
Al2O3 against 69% for pure Pd supported on ϒ-Al2O3 at 400oC. Pd/ZrO2 showed an increase in the activity with
successive cycling. The conversion increased from 23% (for cycle-1) to 58% (cycle-4) at 400oC. This could be
attributed to strong metal support interaction (SMSI) effect after first light-off. Effect of palladium loading and
intermediate sintering during impregnation on the activity will be discussed.
4. First-principles investigation of the active site and the reaction mechanism of acetaldehyde
hydrodeoxygenation over Ru/TiO2(110)
Byeongjin Baek, Lars C. Grabow
Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas, 77204 - 4004,
United State. Email: [email protected]
Using periodic density functional theory (DFT) we have explored the hydrodeoxygenation (HDO) pathways of
acetaldehyde, a surrogate molecule for some of the over 400 different oxygenates from biomass fast pyrolysis,
on metallic Ru(0001), pure oxide catalysts (RuO2(110), TiO2(110)), and modified oxide catalysts (1 ML
RuO2/TiO2(110), Ru-doped TiO2(110), Ru10/TiO2(110)). The binding energies of possible surface intermediates
and the activation energies of a large number of different elementary steps, including the preference for C-H,
C-O, and C-C bond scission reactions, were investigated. On the metallic Ru(0001) surface, C-C scission rather
than C-O scission and the deposition of carbon on the surface at the end of the catalytic cycle is the preferred
pathway. For RuO2(110), 1 ML RuO2/TiO2(110), and TiO2(110) we first derived constrained thermodynamic
phase diagrams under typical HDO conditions, which indicate that these surfaces are partially reduced and
exhibit bridging hydroxyl groups. Upon further hydrogen adsorption the surface hydroxyl groups can be
removed as water and surface oxygen vacancies are formed. These vacancies not only play an important role
for acetaldehyde adsorption, but also are beneficial for the preferential activation of C-O scission over C-C
scission in acetaldehyde, leading to the desired product ethylene. Ethanol is predicted as the primary,
competing by-product on these oxide surfaces. The highest selectivity for ethylene is predicted for TiO2(110),
however, the dissociation of gas-phase hydrogen and the formation of bridging hydroxyl groups, the precursor
to the formation of a required oxygen vacancy, is highly activated in comparison to the remaining oxide
surfaces. In best agreement with experimental observations is a mechanism involving facile hydrogen spill-over
from the Ru nanocluster in the Ru10/TiO2(110) system and acetaldehyde HDO on the TiO2(110) surface.
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5. Optimization of LNT-SCR Dual-Layer Catalysts for Diesel NOx Emission Control
Yang Zheng, Dan Luss*, Michael P. Harold
**
Department of Chemical & Biomolecular Engineering, University of Houston, Houston, TX 77204. Email:
Monolithic catalysts consisting of a layer of SCR catalyst deposited on top of a LNT catalyst were optimized to
provide high NOx conversion with minimal precious group metal (PGM) loading as a cost-effective and highly-
efficient deNOx technology for light duty diesel and lean burn gasoline engines. In this study we demonstrate
the combination of zoned and layered architecture as an effective catalyst design strategy to improve NOx
reduction efficiency and enable up to 40% reduction of expensive PGM level from that of LNT only catalyst
without degrading its deNOx performance under simulated diesel exhaust conditions. We investigated the NOx
reduction pathway in the SCR layer of the dual-layer catalyst using simulated rich exhaust of C3H6/CO/H2 as
reductants. The non-NH3 reduction pathway by N-containing organic intermediates via the synergy of LNT and
SCR catalysts can play a major role in the incremental NOx conversion over SCR layer at low temperatures (<=
225 oC). The roles of NH3 and C3H6 as reductants for NOx conversion over the SCR catalyst increase with
temperature (> 225 oC). The impact of SCR and LNT zoning as well as SCR layer thickness, were studied.
Zoning of either or both the SCR and LNT in the dual-layer catalysts improved the low-temperature NOx
conversion, and minimized the high-temperature (300-400 oC) conversion loss caused by the SCR layer
diffusion resistance and undesired NH3 oxidation. The performance decline due to the Cu-zeolite layer
diffusion resistance was confirmed by replacing it with an inert Na-zeolite layer with a high Si/Al ratio.
6. Rare Earth/Transition Metal Oxides for Syngas Cleanup
Rui Li1, Matthew D. Krcha
2, Michael J. Janik
2, Amitava Roy
3 and, Kerry Dooley
1
1Department of Chemical Engineering, Louisiana State University, 3810 West Lakeshore Drive, Baton Rouge,
LA 70803 2Department of Chemical Engineering, Pennsylvania State University, University Park, PA16802
3Center for Advanced Microstructures and Devices, Louisiana State University, Baton Rouge, LA, 70806.
Email: [email protected]
The removal of tars from syngas generated in biomass or coal/biomass gasifiers plays an important role in
syngas cleanup. Problems caused by tar buildup downstream, such as pipeline blockage and catalyst
deactivation, are eliminated by converting tars to fuel gases. Rare earth oxides (REOs, e.g., Ce/LaOx) mixed
with transition metals (e.g., Mn, Fe) were synthesized by templated sol-gel or evaporation induced self
assembly methods, or supported on thermally stable alumina. These catalysts were applied to tar removal in the
temperature range <1100 K using synthetic syngas mixtures with C10H8 as a tar model compound, both with
and without H2S. Some commercial Ni reforming catalyst formulations were examined comparatively. Select
fresh and used catalysts were characterized by BET, TPO, XRD, XANES. We found that the C10H8 is reformed
to at least methane, although further reforming to CO and H2 is not always achieved. While CO2, H2S and coke
formation all inhibited or deactivated the catalysts at certain temperatures and to different extents, it was
determined that Fe- or Mn-doped supported REOs are promising tar cleanup catalysts. They exhibited higher
sulfur tolerance, less coking, and less methanation than typical Ni-based high temperature reforming catalysts.
This behavior is in part attributed to enhanced generation of oxygen vacancies in the doped REOs.
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7. Framework Stabilization of Si-Rich LTA Zeolite in OSDA-Free Conditions
Marlon T. Conato, Matthew D. Oleksiak, Jeffrey D. Rimer
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, Houston,
TX 77204. Email: [email protected]
LTA and FAU, two zeolite framework types that have found several commercial applications, are typically
prepared with a low Si-to-Al ratio (SAR) by direct synthesis without the use of organic additives or special
treatments such as seeded-growth or dealumination. Our study investigates the formation of these two crystal
structures with relatively high SAR products by hydrothermal synthesis without the use of organic structure
directing agents (OSDA). A one-step OSDA-free synthesis of LTA (zeolite A) with an SAR greater than 2 is
reported for the first time as well as the stability of its formation for a range of synthesis parameters, such as
temperature, crystallization time, alkalinity, and water content. The rational design of Si-rich zeolites provides
materials with improved thermal stability and extends their applicability to a wider range of operating
conditions.
8. The Role of TiO2 Support Sites for the Conversion of Lignin-Derived Phenolics on Ru/TiO2
Taiwo Omotoso, Steven Crossley
School of Chemical, Biological and Materials Engineering,University of Oklahoma. Email:
Bio-oil derived from lignocellulosic biomass is a promising source for producing renewable chemicals and
fuels, however catalytic upgrading of this complex mixture presents various challenges, partly due to the
conversion of phenolic compounds obtained from lignin pyrolysis. Supported ruthenium catalysts have been
shown previously to be active for the conversion of guaiacol and it was demonstrated that the synergism
between Ru and reducible TiO2 produced a more stable catalyst with higher initial guaiacol conversion rates
and higher selectivity to completely deoxygenated aromatic hydrocarbons when compared with other supports.
Interestingly catechol, a di-oxygenated compound, was not observed as an intermediate in this reaction over
Ru/TiO2. In this contribution, the role and nature of defect sites on the conversion of catechol over Ru/TiO2 at
250 °C and atmospheric pressure is studied by varying reduction temperature and number of perimeter sites
respectively. Catalysts were well characterized by XRD, TEM and other techniques. Results show that after
reduction at 600 °C, catechol conversion rates over Ru/TiO2 decreased due to the encapsulation of Ru metal
particles which occurs after high temperature reduction and this leads to decreased hydrogen spillover to create
defect sites. Also, rates due to catechol conversion on the support do not vary significantly with the number of
perimeter sites. Therefore, defect sites created from the synergy between Ru and TiO2 likely play a role in
catechol conversion over Ru/TiO2 and the sites are believed to be farther away from the Ru metal and not
perimeter sites near the Ru metal particles.
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9. Bimetallic Pt:Pd Catalyst Kinetics for CO and C3H6 Oxidation in Diesel Oxidation Catalysts
Melanie J. Hazlett, William S. Epling
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road; Houston,
TX 77204. Email: [email protected]
Diesel oxidation catalysts (DOCs) function to oxidize CO, NO, and HCs, and typically contain Pt and Pd. It
has been shown that adding Pd to Pt based DOCs leads to less Pt sintering relative to monometallic Pt catalysts
[1]. Pt is a much better NO oxidation catalyst than Pd, and Pd is less sensitive to CO poisoning than Pt [2].
Non-uniformly distributed, or zone-coated, oxidation catalysts have been studied [3], where the premise for
DOCs is axially distributing Pt group metal (PGM) to minimize the amount of metal used to meet conversion
targets. A non-linear relationship between oxidation performance and Pt or Pd content has been observed, with
different minimum Pt:Pd ratios achieving low light-off temperatures for different compounds [4]. Pt, Pd, and
different ratios of Pt:Pd bimetallic catalysts, supported on Al2O3, were prepared via incipient wetness
impregnation. All catalysts are based on 1 wt% Pt catalyst loading, with a molar equivalent of Pd considered
(0.55 wt%). TPO experiments conducted with CO (1000-4000ppm), and C3H6 (500-2000 ppm) with excess O2
(6-10 vol%) from 100-300°C. Outlet concentrations measured with MKS MultiGas2030 FTIR gas analyzer.
Results were modeled as a PFR, with low conversion (2-20%) data used to calculate kinetic parameters
(activation energies and frequency factors). The CO and C3H6 kinetics for monometallic Pt and Pd have been
tested and modeled, and we are currently characterizing the kinetics for various bimetallic Pt:Pd catalysts with
varying Pt:Pd ratios. The goal of this research is designing a better DOC (reduction in precious metal content
or improved performance), by taking advantage of the effects of different Pt:Pd ratios. Kinetic parameters
calculated can be used in a monolith reactor model to determine optimal axial distribution of PGM.
10. Experimental and kinetic study of SO2 oxidation on a Pt/γ-Al2O3 catalyst
Tayebeh Hamzehlouyan, Chaitanya S. Sampara, William S. Epling
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Rd, Houston,
TX 77204. Email:[email protected]
In order to describe SO2 oxidation over a Pt/γ-Al2O3 oxidation catalyst, an SO2 oxidation experimental study
was performed and a kinetic model was developed. An apparent activation energy of 98.8 kJmol-1 was
measured when SO3 was present in the feed. Reaction orders of 0.88 and -0.24 were obtained for SO2 and O2,
respectively, and the SO3 reaction order was found to be -0.42 demonstrating its inhibition effect. A Langmuir-
Hinshelwood mechanism was proposed for the reaction and a microkinetic model was developed. A plug flow
reactor model was assumed for a single channel of the monolith and the set of algebraic differential equations
was solved at various temperatures to predict the SO2 conversion as a function of temperature. The relative
importance of each step in the reaction mechanism was studied at different temperatures to identify the rate
determining step (RDS). According to the model, at temperatures below 300°C, O2 adsorption/desorption and
the surface reaction between the adsorbed SO2 and oxygen control the overall rate, whereas at higher
temperatures the surface reaction is the RDS. The model predicts that at low temperatures, SO3 inhibits SO2
oxidation through occupation of the active sites required for oxygen adsorption, verifying the higher activation
energy observed in the presence of SO3 in the feed. The modeling results revealed that the relative importance
of the individual rates in the mechanism as well as the surface coverages were strongly temperature dependent.
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11. Catalysts for the Positional Isomerization of Long-Chain Olefins
James Bruno and Kerry Dooley
Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA 70802. Email:
Internal, long chain olefins (>C12) are used in the production of paper sizing agents and as deep-sea drilling
fluids. In this project, we studied the double-bond (positional) isomerization of C16-C18 olefins. Both solid
acid and organometallic chain-walking catalysts were evaluated. Solid acids, such as sulfonated poly(styrene-
co-divinylbenzene), perfluorinated ion exchange resins, and acidic zeolites were tested in packed bed reactors
to determine catalyst lifetime and selectivity to internal olefins. The most promising catalysts had a high
selectivity with slow deactivation. Iron pentacarbonyl, a chain-walking catalyst, was tested in a batch reactor to
determine the optimal catalyst concentration, temperature, and residence time. We are currently studying the
immobilization of Fe(CO)5 on resin supports.
12. Vibrational Stark effects of CO at Platinum Electrodes in Ionic Liquids: Sum Frequency Generation
Spectroscopy and Density Functional Theory Study
Quan A. Vo1, Lars C. Grabow
2, Steven Baldelli
1
1Department of Chemistry, University of Houston, Houston, TX 77204
2Department of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204
The vibrational Stark effects of CO at metal electrodes in room-temperature ionic liquids have been
investigated recently. In this report, Stark shifts of CO at Platinum electrodes in alkyl-methylimidazolium
tetrafluoroborate with variation of alkyl chain lengths were obtained from sum frequency generation
spectroscopy. Under the assumption that the Helmholtz model can be applied to the double layer structure of
the ionic liquid/metal electrode interface, vibrational Stark shifts were used to deduce the thickness of the ionic
liquid layer. Further, the molecular interactions of ionic liquids and adsorbed CO on Platinum electrodes at
different external potentials were explored by density functional theory (DFT) calculations. DFT results
obtained for ionic liquids are compared to those in vacuum and water.
13. Non-Classical Pathways of Zeolite Crystallization from Amorphous Precursors
Rui Li, Manjesh Kumar, Jeffrey Rimer
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, Houston,
TX 77204. Email: [email protected].
This study focuses on the formation of zeolite L (LTL framework type), which is a prototypical example of a
crystal that grows by a non-classical crystallization mechanism. The evolution of pre-nucleation amorphous
particles was evaluated on the basis of their temporal change(s) in morphology, particle size, and degree of
aggregation (e.g., fractal dimension). To this end, we used a combination of experimental techniques, such as
electron microscopy and light scattering, to characterize their amorphous-to-crystalline phase transformation.
These studies revealed that LTL crystals nucleate from worm-like particles (WLPs), i.e. amorphous, fractal-like
precursors. The putative mechanism of formation involves the initial aggregation of colloidal silica particles,
which subsequently fuse together into fractal WLP aggregates. Time-elapsed images of evolving WLPs reveal
that these structures provide nutrients to growing crystals, and likely serve as solid interfaces for heterogeneous
nucleation and subsequent growth of LTL crystals via solution-mediated processes. This mechanistic study of
zeolite crystallization was extended to analyses of the fundamental effects of zeolite growth modifiers (ZGMs),
which are site-specific molecules that bind to growing crystals and tailor both their size and morphology,
thereby altering the physicochemical properties of zeolite catalysts in order to improve their performance in a
variety of commercial applications.
13
14. CO Oxidation over Bifunctional Alloy and Metal/Oxide Catalysts
Hieu A. Doan and Lars C. Grabow
Department of Biomolecular and Chemical Engineering, University of Houston, 4800 Calhoun Road, Houston
TX 77204-4004. Email: [email protected]
The descriptor-based approach in heterogeneous catalysis simplifies the daunting task of studying catalysts’
performance for complex reaction networks by employing scaling relations based on reactivity descriptors
derived from density functional theory (DFT) simulations [1]. Within this approach, catalysts can be evaluated
qualitatively through a simple descriptor such as an adsorption energy or the d-band center that is associated
with an active site. Although the resulting volcano curve makes it possible to study activity trends and identify
promising materials, it imposes a maximum achievable activity approximated by only a few candidates. To
widen the candidate pool for various catalytic processes and possibly even overcome the theoretical limit of
monofunctional catalysts we extend the descriptor-based approach to materials that consist of two or more
distinct sites that catalyze different reaction steps independently; such materials are often referred to as
“bifunctional catalysts”. Using DFT and microkinetic modeling, we aim to understand the interplay of active
sites on bifunctional catalyst surfaces by probing the CO oxidation reaction on metal alloy and metal-support
systems. For the former, we observed that the theoretical maximum activity is not significantly altered when
bifunctional sites are considered, but equally active bifunctional catalysts may be tailored from less active and
cheaper components. Our results for the latter, employing the Au/TiO2 system in particular, show that weakly
adsorbed H2O at the metal-support interface serves as a co-catalyst and significantly improves catalytic activity.
Such observation, supported by experimentally obtained kinetic isotope effects, indicates that the existence of
multiple active sites plays a very important role in determining the overall activity of metal-support interfaces.
15. First-principles Study of the Methanol-to-DME Reaction Mechanism on H-ZSM-5
Arian Ghorbanpour, Lars C. Grabow, Jeffrey D. Rimer
Department of Biomolecular and Chemical Engineering, University of Houston, 4800 Calhoun Road, Houston
TX 77204-4004. Email: [email protected]
Conversion of methanol to hydrocarbons over acidic catalysts, in particular H-ZSM-5, is a feasible route for the
production of liquid fuels and has been a popular subject of catalytic studies. The first step of this process is
methanol dehydration to dimethyl ether (DME). A thorough understanding of the mechanism of methanol
dehydration is therefore of great interest to identify improved catalytic materials for this reaction. Here, we use
periodic density functional theory calculations to study the reaction mechanism of methanol dehydration over
H-ZSM-5, a zeolitic catalyst with known activity for this reaction. We modeled the formation of DME from
methanol through two main pathways to identify the dominant mechanism. The associative pathway is
characterized by the initial adsorption of a methanol dimer followed by water elimination, while in the
dissociative pathway water formation occurs from a single methanol molecule followed by the DME formation
step after a second methanol molecule adsorbs.
The active sites of H-ZSM-5 are Brønsted acid sites that can be found in 12 distinguishable locations, which
may be grouped as belonging to the sinusoidal channel, the straight channel, or the intersection of those. We
have recently demonstrated that the geometric and chemical properties of these 12 sites span a wide range of
values and these variations may favor different reaction pathways [1]. The effect of geometry-dependent
confinement effects on the reaction mechanism is investigated by calculation of reaction barriers at T10, T11,
and T12 sites representing sinusoidal, straight, and intersection positions, respectively. We also employ an
approach to tune the acidity of a specific location of an active site in the framework by using three different
heteroatoms, i.e. aluminum, gallium, and indium. The resulting activation barrier of the reaction for the three
different heteroatoms is used as the site acidity descriptor and its relationship with other site properties is
investigated.
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16. Microkinetic modeling of oxidative methane activation on transition metal surfaces
Abraham I. Aboiralor, Lars C. Grabow
Department of Biomolecular and Chemical Engineering, University of Houston, 4800 Calhoun Road, Houston
TX 77204-4004. Email: [email protected]
Recent discoveries of large shale and tight gas reservoirs in the U.S. and many other parts of the world have led
to an increased interest in methane (CH4) utilization. The strong C-H bond and the high symmetry of the CH4
molecule, however, make it difficult to activate methane at lower temperatures and convert it into useful fuels
or chemicals. Literature evidence suggests that certain active surface oxygen species can facilitate CH4
activation and lower the required reaction temperature, but their nature remains elusive. Using a descriptor-
based microkinetic modeling approach implemented in “CatMAP” [1] with energetic input parameters obtained
from published linear scaling relations, we developed a reaction mechanism that describes total and partial
catalytic oxidation of CH4, and steam reforming on stepped (211) transition metal surfaces. The binding
energies of atomic carbon and oxygen are used as descriptors for the estimation of the remaining intermediates’
binding energies and stabilities of transition states. Trends in reactivity, selectivity, surface coverage, and the
nature of the rate-determining step as a function of reaction temperature are reported. These microkinetic
modeling results form the basis for the computational design of metal alloy catalysts for unselective methane
combustion to CO2 and H2O, as needed in vehicle exhaust after treatment catalysis, and the production of
synthesis gas (CO/H2) through selective partial oxidation or steam reforming.
17. A First Principles Comparison between Hydrodeoxygenation of Furan and Hydrodesulfurization of
Thiophene
Sashank Kasiraju, Byeongjin Baek and Lars C. Grabow
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Road, Houston
TX 77204-4004. Email: [email protected]
The high oxygen content (35-40 %) of bio-oil produced from fast pyrolysis of biomass reduces its heating value
and stability, and limits its subsequent use as a transportation fuel. Catalytic hydrodeoxygenation (HDO) is a
promising emerging technology that can be used to lower the oxygen content, but suitable catalysts need to be
developed. In order to better understand the HDO chemistry we compare it to the well-studied
hydrodesulfurization process (HDS) used in the petroleum refining industry for the removal of sulfur.
We studied furan-HDO (analogous to thiophene-HDS) on the RuO2 (110) surface, which is the oxide analogue
of the most active RuS2 catalyst for HDS. A prominent density functional theory (DFT) study of thiophene-
HDS on MoS2 is used as a reference [1]. Similar to HDS, HDO requires the initial creation of an oxygen-
vacancy site on the surface under high hydrogen pressures where the feed oxygenate is adsorbed. The potential
energy diagram based on the thermodynamic stability of reaction intermediates suggests that the reaction
pathways for two different mechanisms for the HDS of thiophene and HDO of furan are similar. Activation
barriers for elementary surface reactions further indicate that furan-HDO on RuO2 is facile. Vacancy formation
energies have been used as a descriptor to predict HDS trends in metal-sulfides. We report a linear scaling
relation on different rutile metal oxides to predict HDO trends as a function of oxygen vacancy formation
energies, which strongly suggests that this descriptor is also suitable for HDO on metal-oxides. Unraveling the
similarities and differences between the two processes and identifying a reactivity descriptor for HDO on
oxides will ultimately let us design a novel HDO catalyst for the commercialization of bio-fuels and chemicals.
15
18. On the nature of acid sites on tetragonal zirconia
Juan-Manuel Arce-Ramos1, Lars Grabow
2, María-Guadalupe Cárdenas-Galindo
1
1CIEP Facultad de Ciencias Químicas, Universidad Autónoma de San Luis Potosí, Av. Dr. Manuel Nava No. 6,
San Luis Potosí, SLP, México. 2Department of Chemical and Biomolecular Engineering, University of Houston, Texas 77204-4004, United
States. Email: [email protected]
Computational modeling has become a powerful tool to understand atomic-level processes and properties of
materials, especially when combined with experiments. In this study, the adsorption of ammonia (NH3) on
zirconia (ZrO2) was investigated by adsorption microcalorimetry and density functional theory (DFT) methods
(PW91 exchange-correlation functional combined with the PAW method). The sample was synthesized by
grafting of zirconium (IV) n-butoxide on fumed silica to achieve 30wt % Zr on the surface. The calcined
sample exhibits high surface area (218 m2/g) and only XRD features of tetragonal zirconia. According to
ammonia adsorption microcalorimetry results, the sample exhibits an initial heat of adsorption of around 165
kJ/mol. Our theoretical calculations suggest that NH3 binds strongly (ΔEads ~ 120 kJ/mol) to a vacancy-free
ZrO2(101) surface at coverages up to 2.16 NH3/nm2 (3.59 µmol/m
2). Even for a stepped ZrO2(211) surface
model, where the coordination of Zr surface atoms is lower, the initial heat of adsorption is comparable to
terrace sites. However, DFT results show stronger adsorption energies (up to 190 kJ/mol) when NH3 is
adsorbed dissociatively on the ZrO2(101) surface with oxygen vacancies. Adsorption energies below ~100
kJ/mol that decrease with increasing coverage can be well explained due to lateral NH3-NH3 interactions.
Therefore, the experimental acidity results are consistent with a ZrO2 surface where the strongest Lewis acid
sites are associated with oxygen vacancies.
19. Visible Light Photocatalytic Overall Water Splitting using Cobalt Monoxide Nanocrystals
Longbiao Liao, Jiming Bao
Department of Electrical & Computer Engineering, University of Houston, TX, 77204. Email:
Using solar energy and semiconductor photocatalysts to split water to produce hydrogen is crucial for solving
our energy crisis and environmental problems in the future. Recently, we demonstrated visible light
photocatalytical water splitting using nanocrystalline cobalt monoxide synthesized by mechanical ball milling.
TEM, TEM SAED, XPS and XRD revealed that milled particles are CoO single crystal with rock-salt structure
at size of 5-8 nm. The efficiency of solar-to-hydrogen of water splitting reached over 5% under simulated solar
irradiation. The high solar-to-hydrogen efficiency is due to its broad photocatalytic response to visible light up
to 650 nm.
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20. Tuning the Physicochemical Properties of Zeolite Catalysts through Molecular Design
Manjesh Kumar, Rui Liu and Jeffrey D. Rimer
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Rd., Houston,
TX 77004. Email: [email protected].
There are growing opportunities for the use of zeolite catalysts in a wide range of applications. Despite their
extensive use in commercial processes, an understanding of their growth mechanism(s) remains elusive. The
rational design of zeolite catalysts calls for more versatile synthetic approaches capable of a priori tailoring
crystal properties, such as crystal size, morphology, diffusion pathlength, and surface architecture. Here we will
discuss the design of 1-D zeolites, notably LTL and MOR types, which commonly exhibit severe mass
transport limitations due to their 1-D pores and suboptimal crystal habit. This class of porous materials offers
an opportunity to explore the impact of crystal engineering on catalyst performance (i.e. activity and
selectivity). To this end, we will discuss our studies of zeolite crystallization in the presence of zeolite growth
modifiers (ZGMs), which are molecules that selectively bind to specific surfaces of zeolite crystals and mediate
anisotropic growth rates [1]. We systematically examined a library of modifiers ranging in their structure and
functional moieties to assess the physicochemical properties that regulate their efficacy and specificity as
zeolite crystal growth modifiers. As we will demonstrate, the judicious selection of ZGMs can markedly alter
zeolite crystal morphology from high aspect ratio (needle-like) crystals to thin discs with diffusion pathlengths
and external surface areas that span more than 3 orders of magnitude. These studies revealed that ZGM
hydrophobicity and the spatial sequencing of binding moieties are effective molecular descriptors of its efficacy
[2]. Moreover, polymers proved to be more effective modifiers than their corresponding monomers.
Collectively, these studies seek to establish a molecular screening method to provide general heuristics for
designing 1-D zeolite structures. We will present these fundamental studies and also discuss how techniques,
such as atomic force microscopy, can be used to probe the mechanisms of zeolite crystallization and the effects
of ZGMs. Moreover, we will present time elapsed studies of zeolite L crystallization with and without
modifiers whereby we tracked transformations from amorphous to crystalline phases in order to elucidate the
impact of modifiers on zeolite L crystallization.
21. Controlling Polymorphism in Organic-Free Syntheses of Zeolites
Matthew D. Oleksiak, Marlon Conato, and Jeffrey D. Rimer*
University of Houston, Department of Chemical and Biomolecular Engineering, 4800 Calhoun Rd, Houston,
TX 77004. Email: [email protected]
The unique acidity, thermal stability, and shape-selectivity of nanoporous zeolites are utilized in industrial
applications spanning catalysis to ion exchange. Difficulties in the formation zeolites in organic-free zeolite
synthesis are prevalent, and the most common concern is the formation of undesirable crystal phase(s), i.e.
impurities. Oftentimes, organic structure directing agents (OSDAs) are used to form phase-pure crystals,
though these additives are typically costly and must be removed by post-synthesis calcination. In order to both
understand and control organic-free polymorphism, we constructed kinetic phase diagrams based on varying
synthesis conditions using only inorganic ions (e.g., alkali metals) as the structure directing agents. These
kinetic phase diagrams revealed regions of pure and mixed phases of eight zeolite framework types synthesized
from colloidal silica and sodium aluminate. Our systematic study has elucidated for the first time the phase
behavior of GIS framework type, which exhibits two polymorphs: zeolites P1 and P2. By generating phase
diagrams over a range of synthesis parameters, we have determined the conditions required to produce pure P1
and P2, and explored the kinetic pathways of each polymorph.
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22. The role of temperature and water on the conversion of acetic acid on HZSM-5
Abhishek Gumidyala, Tawan Sookonoi, Steven Crossley.
University of Oklahoma, School of Chemical, Biological and Materials Engineering, Norman, OK, 73019,
United States. Email: [email protected]
Acetic acid is one of the most abundant and problematic species present in bio oil obtained from the fast
pyrolysis of biomass. Acetic acid’s ability to promote polymerization of species present in pyrolysis oil and
deactivate catalysts even at low temperatures is major concerns in upgrading the pyrolysis oil. Further, its
corrosive nature contributes to handling and storage problems thereby making it the most undesirable
compound in bio oil. The ketonization reaction offers a great advantage in this process since it not only
removes acid but also forms acetone which can be further converted to produce longer-chain hydrocarbons via
aldol condensation/hydrogenation. We have identified conditions that favour the conversion of acetic acid to
the chemical building block, acetone with near 100% selectivity over HZSM-5. Temperature programmed
experiments and FTIR results are used to identify the reaction mechanism responsible for the initial
ketonization and subsequent reactions. Further, a systematic variation of temperature reveals the increase in rate
of acetone production with increasing temperature until 330 OC. Temperatures above 330
OC result in a loss of
carbon to form heavier condensation products that do not desorb from the catalyst surface. Finally we discuss
the important role of water by presenting a study of change in rate of reaction with partial pressure of water,
with implications on catalyst lifetime, competitive adsorption, and inhibition due to the interaction with reactive
intermediates.
23. Spatiotemporal behaviors of Pt/Rh/CeO2/BaO Catalyst during Lean-Rich Cycling
Hoang Nguyen, Dan Luss, Michael.P.Harold
Department of Chemical and Biomolecular Engineering, University of Houston, 4800 Calhoun Rd, Houston,
TX 77204-4007. Email: [email protected]
In this work, we describe a powerful optical sensing technique, namely coherent Optical Frequency Domain
Reflectometry (c-OFDR), that enables transient temperature measurement with an optical fiber. This technique
can pin point the exact location and magnitude of any temperature variations along a fiber with unparalleled
spatial and temporal resolution compared to any other traditional temperature measurement techniques. This
technique was used with the spatially resolved mass spectrometry (SpaciMS) equipment to study the
performance of two lean NOx trap (LNT) catalysts, one of which contained Ceria, under a periodic process.
The experiments were conducted at an initial catalyst temperature of 300°C. Both catalysts were fed
periodically for a short time (5s) with a rich feed of 1.2 vol.% propylene and followed by a longer (30s) lean
feed of 10 vol. % O2. The temperature measurements revealed complex spatial temporal temperature features,
i.e., the maximum temperature rise after the rich-lean switch was much higher than that following the lean-rich
switch. Moreover, the hot zone in a non-Ceria based catalyst following the rich-lean switch was wider than that
in the Ceria based catalyst. These thermal behaviors are explained based on the measured axial concentration
profiles. Both the measured spatial temporal concentration and temperature profiles showed that Ceria
increased the breakthrough time of propylene. The accumulation of absorbed propylene in the upstream
monolith caused the high temperature rise in the rich-lean transition. Furthermore, without Ceria the hydrogen
concentration increases monotonically along the monolith. In the presence of Ceria, hydrogen forms a local
maximum due to its downstream reaction with CeO2.
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24. Modeling Methane Oxidation
Syed Ali Gardezi, William Epling and Mike Harold.
Department of Chemial and Biomolecular Engineering, University of Houston, 4800 Callhoun Drive, Houston,
Texas, 77004. Email: [email protected]
In this research, a monolithic system having washcoat of “active material” supported on γ-Al2O3 is being
considered for CH4 oxidation. A kinetic and reactor level model has been developed, focusing on both kinetics
and hydrodynamics. In kinetic modeling, the data from experimental work is being used for the calculation of
surface activation energies and pre-exponential factors which are further supplied as subroutine values for the
main model. Different active metal surfaces will be analyzed against Pd-PdO which is taken as the base case. In
the hydrodynamic part “a single channel” is taken as representative of the entire monolith. The composition of
exhaust gas (2000 ppm CH4, 6% O2 and rest nitrogen) keeps the system diffusion limited with respect to
methane for typical washcoat thicknesses ranging from 15-50 μm, thus requiring an investigation of the intra-
washcoat porosity. The current model is one dimensional based on convective transport in the axial direction
while inter-channel radial diffusion is neglected. The regime near the washcoat is separated from the bulk via a
mass transfer coefficient. The model is capable of simulating both steady state and dynamic startup processes.
It can also simulate TPO experiments for kinetic evaluations. Another area of interest is partial oxidation where
oxygen becomes diffusion and/or reaction limiting. Such systems are more complicated, under limited oxidant
the system is characterized by six independent stoichiometric equations ranging from oxidation to reforming
and water gas shift reactions.
25. Benzyl Alcohol Oxidation by Supported Au Nanoparticle Catalysts: Evaluating the Number of Actives
Sites by Thiol Poisoning and Titration
Basu D. Panthi, Johnny Saavedra, Christopher J. Pursell, Bert D. Chandler
Department of Chemistry, Trinity University, 1 Trinity Place, San Antonio, TX 78212. Email:
Gold nanoparticles deposited on different oxides can be used for a variety of reactions including important
organic reactions. The catalytic activity of gold catalysts depends on many factors (particle size, dispersion,
support, etc.), all of which can influence the number of active sites. To differentiate the number of active sites
on different catalysts, we explored intentional thiol poisoning during benzyl alcohol oxidation. The total
number of thiol binding sites was also evaluated with a UV-Visible spectrophotometric titration using
phenylethyl mercaptan (PEM) as the titrant. The amount of thiol required to inhibit the catalytic activity was
then compared with the amount of thiol required to form the thiol Self Assembled Monolayer (SAM) on gold to
estimate the fraction of active gold sites. To better understand the poisoning mechanism and evaluate number
of active sites, thiols with different alkyl chain length were used. Comparison between Au/TiO2, Au/SiO2 and
Au/Al2O3 catalysts will be presented. Support effect on benzyl alcohol oxidation catalysis by gold nanoparticles
will also be presented.
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26. Water adsorption on Au based catalysts: implications for O2 activation and catalysis.
Johnny Saavedra, Basu Panthi, Chris Pursell and Bert Chandler*
Department of Chemistry, Trinity University, San Antonio, TX 78212-7200. Email: [email protected]
Water has a tremendous impact in CO oxidation catalyzed by Gold. We used in-situ FTIR experiments to
support low conversion catalysis measurements to understand how surface water affects CO oxidation catalysis
over Au/TiO2 and Au/Al2O3 catalysts. It was possible to determine that loosely bound surface water establishes
quasi-equilibrium with the catalyst surfaces. This adsorbed water, and adsorbed carbonates produced during the
reaction are key factors in determining the CO oxidation activity. Two main conclusions can be derived from
this study: 1) catalytic rate is greatly influenced by the presence of water adsorbed on a particular support and
2) the equilibrium of the water adsorbed in the support depends on the nature and the moisture content in the
gaseous stream. Understanding O2 activation co-catalyzed by the presence of adsorbed water on Au based
catalysts opens a new perspective on improving Au based catalysts for a variety of oxidation reactions.
27. Supported Transition Metal Oxides for Deoxydehydration of Polyols to Olefins
Alana Denning*, Friederike C. Jentoft*, Kenneth M. Nicholas**
Department of Chemical, Biological and Materials Engineering*, Department of Chemistry and
Biochemistry**, University of Oklahoma, 100 East Boyd St, Norman, OK 73019 . Email: Alana.L.Denning-
Oxo-Rhenium- and -molybdenum-compounds have been found to be suitable homogeneous catalysts for
deoxydehydration (DODH) of polyols to olefins1, a reaction of great potential for conversion of biomass to
fuels and platform chemicals. DODH can also be achieved by heterogeneous catalysis, as was demonstrated by
the successful application of carbon-supported perrhenate2. Here, a second generation of solid catalysts is
presented that is developed with the goal to improve resistance to leaching and to eventually replace rhenium
with a less expensive transition metal. Three heterogeneous catalysts: MoOx/Al2O3, ReOx/Al2O3, and
VOx/CeO2, were synthesized with careful attention to the surface structure of the transition metal-oxo species,
and were tested for DODH activity with 1,2-decanediol as a model compound for polyols. The choice of
reaction temperature was guided by temperature-programmed reduction (TPR) experiments for each catalyst.
Each catalyst was tested with multiple reducing agents including carbon monoxide and secondary alcohols that
would be feasible for use in a large scale industrial process. The supported molybdenum and rhenium catalysts
were active for DODH, yielding moderate amounts of decene. A brief analysis of side reactions and
suggestions for optimization will also be discussed.
28. Selective Oxidation of Ammonia to N2 on Structured Multi-Functional Catalysts Containing Pt/Al2O3
and Metal-Exchanged Zeolite
Sachi Shrestha*, M. P. Harold*1, K. Kamasamudram**
1 and A. Yezerets**
*Dept. of Chemical and Biomolecular Engineering, University of Houston, Houston, TX 77204-4004, USA.
**Cummins Inc., 1900 McKinely Av., MC50197, Columbus, IN 47201, USA. Email: [email protected];
An experimental and simulation study of selective NH3 oxidation on structured Ammonia Slip Catalyst (ASC)
is presented. The ASC’s contained ammonia oxidation (Pt/Al2O3) and NOx reduction (Fe-ZSM-5) functions
and had dual-layer and mixed washcoat structures. Bench-flow experiments showed that the light-off
temperature was independent of the structure, while the NH3 conversion and product distribution were sensitive
to the structure. The dual layer catalyst performed better in terms of N2 yield in the practically important 350-
500 oC temperature range. Simulations using a 1 + 1D model showed good agreement with the data and were
used to identify structures with improved performance.
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29. Methane Slip Emission Treatment Studies over Pt/Pd/Al2O3 Washcoated Monolith with Spatial
Concentration Measurements
Gregory S. Bugosh, Vencon G. Easterling, Michael P. Harold
Texas Center for Clean Engines, Emissions and Fuels (TxCEF), Dept. of Chemical and Biomolecular
Engineering, University of Houston, Houston, TX 77023. Email: [email protected]
Natural gas is increasingly utilized to fuel vehicles due to the price advantage over gasoline and diesel fuel.
Unfortunately, a small but significant amount of methane (CH4) survives the combustion chamber and “slips”
into the exhaust. While a small contributor to atmospheric smog, CH4 is a greenhouse gas with global warming
potential ~20 times that of CO2, and regulations are expected to become more stringent. CH4 emissions are also
particularly difficult to treat, compared to other unburned hydrocarbons. The catalytic abatement of CH4 slip
emissions by Pt/Pd/Al2O3 washcoated monolith was studied over a wide range of fuel lean and rich conditions.
A peak in CH4 conversion was observed at low O2 feed concentrations. CH4 conversion can be minimal (<10%)
at low O2 feeds until oxygen is lowered below a critical concentration, at which point the reaction achieves
light-off. When O2 feed is increased following light-off, the increased conversion is sustained (~90% at 538°C
or 1000°F). The CH4 conversion thus displays hysteresis depending on direction of O2 increase or decrease.
Additional increases in O2 concentration quenches the high conversion. Spatially resolved mass spectrometry
(SpaciMS) was also performed to further increase the understanding of the reaction progression through the
length of the monolith.
30. Pd-on-Au catalysis in glycerol oxidation and formic acid decomposition
Zhun Zhao1, Pongsak Limpornpipat
1, Huifeng Qian
1, and Michael S. Wong
1,2,3
1Department of Chemical and Biomolecular Engineering, Rice University, 6100 S. Main Street, Houston, TX
77005, USA 2Department of Chemistry, Rice University
3Department of Civil and Environmental Engineering, Rice University. Email: [email protected]
Bimetallic PdAu catalysts are shown to be more active than monometallic ones, but the reasons for the
enhancement are not well understood. In this study, Pd-on-Au NPs with variable Pd surface coverages (sc%)
ranging from 10 to 300 sc% were synthesized and immobilized onto carbon (Pd-on-Au/C). Tested for
glycerol oxidation at 60 °C, pH 13.5, and 1 atm under flowing oxygen, Pd-on-Au/C (1.0 wt% Au loading,
~4-nm Au particles) showed a volcano-shape activity dependence on Pd surface coverage, with maximum
turnover frequency (TOF) values (~6000 h-1
) at 80 sc%. The Pd-on-Au/C material generally had significantly
higher catalytic activities than monometallic Au/C (1.0 wt% Au loading, ~4-nm Au particles) and Pd/C (1.0
wt% Pd loading, ~4-nm Pd particles), both of which had TOF values of ~400 h-1
. For formic acid (FA)
decomposition, our recent kinetic results have showed that 300 sc% Pd-on-Au/C was highly active for FA
decomposition at room temperature. The catalyst had a calculated H2 generation rate of 137 mL/gPd/min and
an initial TOF of 123 h-1 based on 10 min’s data, much more active than its monometallic Au/C (not active)
and Pd/C (TOF = 38 h-1). The reaction rate was in the range of homogenous catalysts with no evidence of
CO formation. Through adjusting Pd surface coverage and Au core size, the catalytic activity and selectivity
could be further modulated.
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31. Carboxyl Multi-Walled Carbon Nanotubes Stabilized Palladium Nanocatalysts with Improved Methanol
Oxidation Reaction
Yiran Wang,1,2
Qingliang He,1,2
Jiang Guo,1,2
Huige Wei,1 Suying Wei
1, 2,* and Zhanhu Guo
1,*
1Integrated Composites Laboratory (ICL), Dan F. Smith Department of Chemical Engineering
Lamar University, Beaumont, TX 77710 USA, Email: [email protected] 2Department of Chemistry and Biochemistry, Lamar University, Beaumont, TX 77710 USA. Email:
Carboxylic groups functionalized multi-walled carbon nanotubes (MWNTs-COOH) decorated with palladium
(Pd) nanoparticles (NPs, the product was denoted as Pd/MWNTs-COOH) were prepared by one-pot thermal
decomposing palladium acetylacetonate (Pd(acac)2) in a refluxing xylene solution in the presence of MWNTs-
COOH without adding any reductant. A decreased ratio of D band to G band in Raman spectra suggested the
occupation of carboxylic groups by Pd NPs in the nanocatalysts. Transmission electron microscope (TEM)
revealed that the introduction of either MWNTs-COOH or MWNTs greatly facilitated the dispersion of Pd
NPs, and more uniform dispersion of Pd NPs was observed in the MWNTs-COOH rather than in MWNTs due
to the anchoring function of carboxylic groups. The Pd/MWNTs-COOH nanocatalysts were observed to have a
peak current density of 174.38 mA/mgPd for methanol oxidation reaction, higher than Pd/MWNTs (72.26
mA/mgPd) and pure Pd NPs (11.81 mA/mgPd). X-ray photoelectron spectroscopy (XPS) disclosed the
composition of Pd/MWNTs-COOH and the interaction between the Pd NPs and the carboxylic groups. For
methanol oxidation in KOH solution with varying methanol and KOH concentrations, the Pd/MWNTs-COOH
nanocatalysts exhibited the best catalytic performance in a condition with a balanced adsorption between
hydroxyl and methanol. Increased current peaks, enhanced reaction kinetics and improved tolerance stability
towards poisoning species with increasing the temperature from 2 to 40 °C were demonstrated by cyclic
voltammetry, Tafel and chronoamperometry tests.
32. Computational Studies of a Bimetallic Homogenous Hydroformylation Catalyst
Ranelka Fernando and George Stanley*
Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803-1804. Email:
In situ FT-IR and NMR spectroscopic data point to different [Rh2Hx(-CO)y(CO)z(rac-P4)]n+
hydroformylation catalysts in acetone and 30% water/acetone solvents. Gaussian DFT calculations have been
extremely useful in providing support for the structures and mechanisms of these bimetallic catalysts. In
acetone the primary catalyst species that reacts with alkene is the dicationic complex [Rh2H2(-CO)2(CO)2(rac-
P4)]2+. This fits our initial proposals and all the catalyst intermediates in the proposed catalytic cycle have
been calculated along with many of the transition state energies. When water is added deprotonation of the
dicationic hydride complex occurs to generate a monocationic mono-hydride catalyst species: [Rh2H(-
CO)(CO)3(rac-P4)]+. The DFT calculations clearly indicate that the active catalyst species usually only have a
single bridging hydride or carbonyl, unlike the double-bridged dicationic catalysts. The proposed bimetallic
monocationic mechanism has been fully computed and will be presented.
A Brief History of the Southwest Catalysis Society
As recounted by Joe W. Hightower, Professor Emeritus, Rice University (April 2009) B.S. ’59 - Harding University; M.S. ’61 and Ph.D. ’63 - The Johns Hopkins University
I came to Rice University from the Mellon Institute in Pittsburgh during the summer of 1967 and
immediately set out to meet catalyst people in the area. We announced an organizational meeting to be
held at Rice, Fall 1967. There were 63 people as charter members of what was to become the Southwest
Catalysis Club. Jim Richardson (Esso Research and Engineering, now University of Houston) drafted the
Bylaws and was elected Vice President, Jack Lunsford (Texas A&M University) was Secretary, Paul
Conn (Shell Oil) was the Treasurer, and I served as the first elected President. The officers held the first
all-day Spring Symposium in May 1968 in the Grand Hall at Rice, and the SWCS was off and running
(42 years and counting!). [As a note, I did my PhD thesis research with Professor Paul Emmett at Johns
Hopkins, which involved isotopic tracer studies of secondary reactions that occur during catalytic
cracking of petroleum products.]
At the time we started, there were about half a dozen “Catalysis Clubs” scattered around the
country: Chicago, Pittsburgh, New York, Philadelphia, California, and perhaps one more. I knew people
in all these “Clubs” though groups like the Gordon Research Conferences on Catalysis, and they all
encouraged us to start a club in the SW. Why 5 states? Texas was obvious. Arkansas was included
because of Sam Siegel (Chemist at UArk); Louisiana, because of several researchers at Esso in Baton
Rouge; Oklahoma, because of several Phillips researchers in Bartlesville; and New Mexico, because of
people at University of New Mexico and at Sandia National Labs in Albuquerque. In spite of the long
distances, people from all these places attended some of the early meetings held twice a year, which
sometimes had attendance near 200. Most of the early meetings were held at Rice or in the Auditorium at
the Shell-Westhollow labs. In later years, the meeting was held in nearby places like Austin, College
Station, and New Orleans.
What was going on that made the late 60s an optimal time to establish the SWCS? I think the
biggest factor was Shell downsizing its labs in Emeryville, CA and moving most its catalysis people to a
new research facility at Westhollow. At the same time, Esso was increasing its applied catalysis work
both in Baytown 30 miles east of the city and in Baton Rouge. For several years, Phillips Petroleum had
been accumulating an amazing number of patents in catalysis at their laboratories in Bartlesville. Bob
Eischens came from New York and was applying his pioneering infrared studies at Texaco in Port Arthur.
Celanese had several catalysis people doing research near Corpus Christi. Many of you may recall that
Texas City was devastated by the largest US chemical plant explosion of an ammonium nitrate ship in the
mid-40s. After the explosion, Monsanto rebuilt its facilities there, where workers were doing research on
improving catalytic processes for styrene and acrylonitrile manufacture. Petrotex Chemical in Pasadena,
another suburb on Houston's ship channel, was optimizing its butadiene and C4 olefins production through
catalytic processes.
In addition, catalysis groups were springing up at several universities, including surface science by
the late John Mike White at the University of Texas, Jack Lunsford's and Wayne Goodman's highly
productive groups at Texas A&M, Richard Gonzales at Tulane, Jim Richardson at U of H, Kerry Dooley
at LSU, Tom Leland and me at Rice, and groups at other universities in the 5-state area. What was
lacking? There was no formal mechanism for these diverse groups to exchange information or get advice
in the southwest. The time was ripe for an organization where catalysis could be openly discussed.
Although much catalysis research is proprietary, enough was sufficiently open to create a stimulating
environment for sharing mutual interests, many focusing on new ultra-high vacuum analytical equipment
that was being rapidly developed.
The first thing we did was to organize an NSF-supported workshop at Rice which (not surprisingly)
concluded that more funding was needed for research on catalysts for fuels, environmental protection (cat
converters), chemicals, etc. At that time, demand was also great for new employees with catalysis
training, but the supply was quite limited. This provided an occasion for the development of short courses
to train industrial employees in heterogeneous catalysis. Several courses were started around the country.
One of the most successful was started at Rice and has continued for more than 30 years through the
University of Houston. It can be said, then, that SWCS was instrumental in starting these
heterogeneous catalysis short courses.
The "Club" was soon invited to join the other half dozen Clubs as a part of the growing North
American Catalysis Society. Being the new kid on the block, our Club was asked to host its first biennial
North American Meeting (NAM-2) in February 1971, which was held at the Astrodome Hotel in Houston.
Jim Richardson and I were Associate and General Chair of the meeting, while Paul Venuto (Mobil
Research/Development and a colleague of the late Heinz Heinemann) was in charge of the Program. At
that meeting the late Dr. R. J. Kokes (one of my professors at Johns Hopkins) and Dr. H. S. Bloch
(Universal Oil Products) were recipients, respectively, of the first Paul H. Emmett and Eugene J. Houdry
Awards in fundamental and applied catalysis.
In 1985, the Southwest Catalysis Society was again called on to host a five-day 9th North American
Meeting (NAM-9) at Houston's Adam's Mark Hotel. This time, Jack Lunsford and Lynn Slaugh were
General and Vice Chair; I was Technical Program Chair. Most recently, the SWCS members organized
the spectacular North American Meeting at Houston's downtown Hilton Americas Hotel in 2007, attended
by over 1000 delegates from all over the world, “Celebrating Catalysis Texas Style.” Kudos again to
SWCS officers Kerry Dooley, Brendan Murray, Scott Mitchell, Michael Reynolds, Yun-Feng Chang,
Michael Wong, and many, many others! All told, the SWCS has hosted 3 national events now: 1971
(NAM-2), 1985 (NAM-9) and 2007 (NAM-20).
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