Unraveling Catalytic Mechanisms and Kinetics: Lessons from Electrical Networks

Meeting Program – November 2016

Ravindra Datta
Professor Ravindra Datta
Professor in the Department of Chemical Engineering,
Fuel Cell Center,
Worchester Polytechnic Institute


Abstract – Catalytic reaction networks, in general, comprise of multiple steps and pathways. While one can now readily predict kinetics of these molecular steps from first principles, there is not yet available a comprehensive framework for: 1) visualizing and analyzing these reaction networks in their full complexity; and 2) unequivocally identifying the germane steps and pathways.

Thus, we have developed an approach called the “Reaction Route (RR) Graph” approach, which allows: 1) direct enumeration of all the pathways as walks on the RR Graph; 2) thermodynamic consistence of step kinetics; 3) elucidation of dominant pathways that contribute materially to the overall flux; 4) identification of bottleneck steps in each of these pathways; and 5) development of explicit rate laws based on the electrical analogy.

The electrical network analogy is based on two aspects of RR Graphs, namely: 1) quasi-steady state (QSS) mass balance of intermediate species, the equivalent of the Kirchhoff’s Current Law (KCL) of electrical circuits; and 2) Hess’s law, or thermodynamic consistence, the equivalent of the Kirchhoff’s Potential Law (KPL), which makes RR Graphs precisely equivalent to electrical networks. Further, we define the step resistance in terms of step kinetics to make the analogy complete. The approach is described with the help of the water-gas shift example.

Biography – Ravi Datta is Professor of Chemical Engineering and Director of WPI Fuel Cell Center. He obtained his Ph.D. degree from the University of California, Santa Barbara, in 1981. From then until 1998, he was a Professor of Chemical Engineering at the University of Iowa, when he moved to WPI, and served as Chemical Engineering Department Head until 2005. Ravi’s research is focused on catalytic and electrocatalytic reaction engineering of Clean Energy, including, fuel cells, hydrogen, renewable fuels, novel catalysts, and catalytic reaction networks. He is a coauthor of 150 papers and 8 patents, and has been a mentor to 25 doctoral students.

Development of heterogeneous catalysts for the production of biomass-derived chemicals by selective C-O hydrogenolysis and deoxydehydration

Meeting Program – October 2016

Keiichi Tomishige
Keiichi Tomishige
Professor in the School of Engineering,
Tohoku University


Keiichi Tomishige

Abstract – Chemical composition of the feedstock from biomass and biomass-based building blocks has much higher oxygen contents than that from crude oil. It has been known that the target products such as monomers for the polymer synthesis have comparatively lower oxygen content, and the methodology for the decrease of the oxygen content is more and more important. One of effective methods is the utilization of the hydrogenolysis of C-O bonds in the substrates. For example, C3-C6 sugar alcohols (glycerol, erythritol, xylitol, and sorbitol) are also regarded as promising building blocks in the biomass refinery. If the selective hydrogenolysis of the target C-O bond among various kinds of the C-O bonds is possible, valuable chemicals such as diols, mono-ols, alkanes can be produced from biomass in high yield. ReOx-modified Ir metal catalyst (Ir-ReOx) is reported to be effective to the selective hydrogenolysis of polyols and cyclic ethers in water solvent. Ir-ReOx/SiO2 catalyzes the hydrogenolysis of glycerol to 1,3-propanediol. The hydrogenolysis of erythritol over the catalyst produces 1,4- and 1,3-butanediols. The selective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol also proceeds using Ir-ReOx/SiO2. In addition, the combination of Ir-ReOx/SiO2 with H-ZSM-5 gives n-alkanes and hexanols from cellulose, sugars, and sugar alcohols in high yield with the total C-O hydrogenolysis and without C-C bond dissociation and skeletal isomerization. Another interesting catalyst is ReOx-Pd/CeO2. The catalyst showed excellent performance for simultaneous hydrodeoxygenation of vicinal OH groups in various substrates. High yield (>99%), turnover frequency, and turnover number were obtained in the reaction of 1,4-anhydroerythritol to tetrahydrofuran. This catalyst is also applicable to the conversion of sugar alcohols mono-alcohols and diols are obtained in high yields from substrates with even and odd numbers of OH groups, respectively. In addition, ReOx-Au/CeO2 catalyzed the conversion of glycerol and erythritol to allyl alcohol and 1,3-butadiene in high yield (91% and 81%), respectively.

Biography – Keiichi Tomishige received his B.S., M.S. and Ph.D. from Graduate School of Science, Department of Chemistry, The University of Tokyo with Prof. Y. Iwasawa. During his Ph.D. course in 1994, he moved to Graduate School of Engineering, The University of Tokyo as a research associate and worked with Prof. K. Fujimoto. In 1998, he became a lecturer, and then he moved to Institute of Materials Science, University of Tsukuba as a lecturer in 2001. Since 2004 he has been an associate professor, Graduate School of Pure and Applied Sciences, University of Tsukuba. Since 2010, he is a professor, School of Engineering, Tohoku University.
His research interests are the development of heterogeneous catalysts for

  1. production of biomass-derived chemicals
  2. direct synthesis of organic carbonates from CO2 and alcohols
  3. steam reforming of biomass tar
  4. syngas production by natural gas reforming

He is Associate Editor of Fuel Processing Technology (2014/2-), Editorial board of Applied Catalysis A:General (2009/4-), Editorial advisory board of ACS Catalysis (2013/11-), International Advisory Board of ChemSusChem (2015/1-) and Advisory Board of Green Chemistry(2016/8-).

In Silico Prediction of Materials for Energy Applications

Meeting Program – September 2016

Dion Vlachos
Dion Vlachos
Elizabeth Inez Kelley Professor of Chemical
& Biomolecular Engineering and Professor of Physics,
University of Delaware

Abstract – In this talk, the need for new materials in various energy domains will be discussed. Multiscale simulation will then briefly be introduced as an enabling technology to address diverse engineering topics. A specific application of multiscale simulation is the prediction of macroscopic behavior from first principles. A more impactful avenue of research is how one could use multiscale modeling in reverse engineering for predicting new materials for production of energy and chemicals and energy storage. We will demonstrate how descriptor-based modeling can enable such a search of novel materials with emergent behavior and assess this framework with experiments. An outstanding question is how reliable and robust are model predictions in comparing to data and our quest for searching new materials. We will demonstrate this methodology for the specific example of ammonia decomposition for hydrogen production for fuel cells and briefly touch upon renewable chemicals and fuels from lignocellulosic biomass.
Biography – Dionisios (Dion) G. Vlachos is the Elizabeth Inez Kelley Professor of Chemical & Biomolecular Engineering and Professor of Physics at the University of Delaware and the Director of the Catalysis Center for Energy Innovation (CCEI), an Energy Frontier Research Center (EFRC) funded by the Department of Energy (DOE). He obtained a five-year diploma in Chemical Engineering from the National Technical University of Athens, Greece in 1987, his M.S. and Ph.D. from the University of Minnesota in 1990 and 1992 respectively, and spent a postdoctoral year at the Army High Performance Computing Research Center in Minnesota. After that, Dr. Vlachos joined the University of Massachusetts as an assistant professor, was promoted to an associate professor in 1998 and joined the University of Delaware in 2000. He was a visiting fellow at Princeton University in the spring of 2000, a visiting faculty member at Thomas Jefferson University and Hospital in the spring of 2007 and the George Pierce Distinguished Professor of Chemical Engineering and Materials Science at the University of Minnesota in the fall of 2007.

Professor Vlachos is the recipient of the R. H. Wilhelm Award in Chemical Reaction Engineering from AIChE and is an AAAS Fellow. He also received a NSF Career Award and an Office of Naval Research Young Investigator Award. He is a member of AIChE, ACS, the Combustion Institute, MRS, the North American Catalysis Society (NACS) and the Society for Industrial and Applied Mathematics (SIAM).

Dr. Vlachos’ main research thrust is multiscale modeling and simulation along with their application to catalysis, crystal growth, portable microchemical devices for power generation, production of renewable fuels and chemicals, catalyst informatics, detailed and reduced kinetic model development and process intensification. He is the corresponding author of more than 340 refereed publications with nearly 10,000 citations and has given over 200 plenary lectures, keynote lectures and other invited talks. Professor Vlachos has served as an executive editor of the Chemical Engineering Science journal and also served or currently serves on the editorial advisory board of ACS Catalysis, Reaction Chemistry & Engineering, Industrial and Engineering Chemistry Research, Applied Catalysis A: General, Proceedings of the Combustion Institute, the Open Energy and Fuels Journal, the Journal of Nano Energy and Power Research and the Journal of Chemical Engineering & Process Technology.

Insight into Supported Metal Catalyst Stability by Quantifying Thermodynamic Interactions at the Solid-liquid Interface

Meeting Program – April 2016

Robert Rioux
Robert Rioux
Friedrich G. Helfferich Associate Professor of Chemical Engineering
Pennsylvania State University

Abstract – Industrial applications of supported late transition metal catalysts demand economic and scalable synthesis of these catalysts and current synthetic methods lack precision in terms of size, shape and compositional control. Moreover, supported metal catalysts suffer from poor stability, manifested in the form of sintering (i.e., particle growth) during reaction. The proper selection of the oxide support is of great importance to ensure high dispersion, activity and selectivity of the nanoparticles. The ability of these supports to enhance the dispersion of the active metal on their surface and control their morphology and sintering kinetics is fundamentally related to the nature and strength of the metal–metal oxide interaction at the time of adsorption. In this work, we have utilized isothermal titration calorimetry (ITC), a technique capable of quantifying the thermodynamic description (ΔG, ΔH, ΔS, n (stoichiometry)) of transition metal association with a support material in a single experiment. After providing a brief introduction to ITC and methods of catalyst synthesis, we will discuss our results to quantify the electrostatic interactions between solvated transition metal ions and charged amphoteric metal oxide surface. Within this interaction-type, we have studied both refractory and reducible metal oxides. With a reducible metal oxide, ceria, we demonstrate a potentially new mechanism of adsorption, which may describe the successful stabilization of noble metals enabling maintenance of small sized nanoparticles compared to other oxide supports. In addition to ITC, bulk uptake studies have aided in quantifying the amount of metal precursor adsorbed on the support surface and equilibrium isotherms describe the uptake behavior and may provide insight for predicting long term stability of the nanoparticles. In the second half of the talk, we discuss the adsorption of transition metal oxide and hydroxide nanoparticles in the galleries of of Nb-based perovskites. ITC was used to quantitatively rank the strength of adsorption between the metal nanoparticle and their propensity to sinter, as assessed by in-situ, high-temperature transmission electron microscopy. In both examples, we will emphasize this initial interaction at the solid-liquid interface is important and conveys a history effect to the catalyst that is evident during post-processing (drying, calcination and reduction). The estimated thermodynamic parameters are expected to quantify the type of bonding at the interface, shed light on the binding mechanism and the growth and sintering kinetics of supported catalysts.
Biography – Robert (Rob) M Rioux is the Friedrich G. Helfferich Associate Professor of Chemical Engineering at the Pennsylvania State University. Prior to joining the Pennsylvania State University in 2008, he was a National Institutes of Health Postdoctoral Fellow at Harvard University in the Department of Chemistry and Chemical Biology working with Professor George Whitesides. He received his Ph.D. in physical chemistry from the University of California, Berkeley in 2006 working for Professor Gabor Somorjai. He holds a B.S. and M.S. degree in chemical engineering from Worcester Polytechnic Institute and the Pennsylvania State University, respectively. Since joining the Penn. State faculty, he has received a number of awards, including a DARPA Young Faculty Award, an Air Force Office of Scientific Research Young Investigator Program Award, a NSF CAREER Award and a 3M Non-Tenured Faculty Award. Research in his laboratory is currently sponsored by NSF, DOE-BES, DARPA, AFOSR, AFRL, ACS-PRF and industry. His group’s current research focus is on the development of spatially- and temporally-resolved spectroscopic techniques for imaging catalytic chemistry, single molecule methods to understand single molecule/particle catalytic kinetics and dynamics, elucidating reaction mechanisms in nanoscale systems, including catalyst synthesis, development of solution calorimetric techniques to understand catalytic processes at the solid-liquid interface and the development of base-metal catalysts for chemoselective chemical transformations, including biomass to chemicals conversion.

Identification of Active Sites for Methyl Lactate Dehydration on Faujasites

Meeting Program – March 2016

Bingjun Xu
Bingjun Xu
Chemical and Biomolecular Engineering
University of Delaware

Abstract – The dwindling reserve of crude oil and surge in natural gas production is rapidly changing the mix of the carbon source pool for the production of fuels and chemical feedstocks, and in turn creating shortages of several key commodity chemicals, e.g., propylene and butadiene. The shortage of certain commodity chemicals, such as propylene, drives up their prices, which in turn raises the cost of the downstream chemicals, such as acrylic acid. In this regard, lignocellulosic biomass derived feedstocks, e.g., lactic acid and its esters, can potentially bridge the gap. Currently, the commercial fermentation process using biomass-derived sugars can achieve a lactic acid (or its esters) yield of up to 90%. The absence of efficient and selective catalyst for lactic acid dehydration is the main missing link in the production of renewable acrylic acid. The primary roadblock for the rational design of catalysts for lactic acid dehydration is the lack of the mechanistic understanding of the nature of active sites and mechanistic steps leading to the selective removal of the α-hydroxyl group by dehydration. Through kinetic and in-situ spectroscopic investigations, we identify the dehydration reaction proceeds through dissociative adsorption, acid-mediated dehydration, and associative desorption steps. These mechanistic insights will guide the design of selective catalysts for this reaction.
Biography – Bingjun Xu is currently an Assistant Professor in the Department of Chemical and Biomolecular Engineering at University of Delaware. Dr. Xu received his Ph.D. in Physical Chemistry, advised by Prof. Friend, from Harvard University in 2011. His thesis established a mechanistic framework for oxidative coupling reactions on Au surface through surface science studies. Dr. Xu worked with Prof. Davis at Caltech on the development of a low temperature, manganese oxide based thermochemical cycle for water splitting. Upon finishing his postdoc, he joined University of Delaware in the fall of 2013. The current research interest of the Xu lab spans heterogeneous catalysis, electrocatalysis and in-situ spectroscopy.

Activation and Self-Initiation in the Phillips Ethylene Polymerization Catalyst

Meeting Program – February 2016

Susannah Scott
Susannah Scott
Duncan and Suzanne Mellichamp Chair in Sustainable Catalysis
Chemical Engineering and Chemistry & Biochemistry
University of California, Santa Barbara

Abstract – The mechanism of spontaneous activation of the Phillips (Cr/SiO2) ethylene polymerization catalyst in the absence of an alkylating co-catalyst is one of the longest-standing problems in heterogeneous catalysis. Experimental and computational evidence has long pointed to organochromium(III) active sites, and the preparation of grafted (SiO)2CrCH(SiMe3)2 sites by the reaction of Cr[CH(SiMe3)2]3 with partially dehydroxylated silica supports this conclusion. However, a plausible mechanism for their formation from the interaction of chromate and ethylene alone remains to be found. A key issue is the incommensurate nature of the required redox reactions, since Cr(VI) must be reduced by an odd number of electrons (three), while only closed-shell organic oxidation products are detected. For the CO-reduced catalyst, Cr K-edge XANES, EPR and UV-vis spectroscopies are consistent with initial step-wise reduction of Cr(VI) in two-electron steps, first to Cr(IV), and ultimately to Cr(II). According to Cr K-edge EXAFS and UV-vis spectroscopy, the Cr(II) sites have a coordination number higher than two, most likely through interaction with neighboring siloxane oxygens. After removal of adsorbed CO, the Cr(II) sites react with ethylene in an overall one-electron redox reaction to generate organochromium(III) sites and organic radicals.
Biography – Scott received her B.Sc. in Chemistry from the University of Alberta (Canada) in 1987, and her Ph.D. in Inorganic Chemistry from Iowa State University in 1991, where she worked with J. Espenson and A. Bakac on the activation of O2 and organic oxidation mechanisms. She was a NATO Postdoctoral Fellow with Jean-Marie Basset at the Institut de recherches sur la catalyse (CNRS) in Lyon, France, before joining the faculty of the University of Ottawa (Canada) in 1994 as an Assistant Professor of Chemistry. She held an NSERC Women’s Faculty Award, a Cottrell Scholar Award, a Union Carbide Innovation Award and was named a Canada Research Chair in 2001. She moved to the University of California, Santa Barbara in 2003, where she is currently holds the Duncan and Suzanne Mellichamp Chair in Sustainable Catalysis, with joint faculty appointments in both Chemical Engineering and Chemistry & Biochemistry. She directs the NSF-sponsored Partnership for International Research and Education in Electron Chemistry and Catalysis at Interfaces, a collaborative research program involving UCSB and several prominent catalysis research groups in China. Her research interests include surface organometallic chemistry, olefin polymerization, nanomaterials, biomass conversion, environmental catalysis and the development of new kinetic and spectroscopic methods to probe reaction mechanisms at surfaces. In 2013, Scott became an Associate Editor for the journal ACS Catalysis.

CO2 Conversion via Catalysis and Electrocatalysis

Meeting Program – January 2016

Jingguang Chen
Jingguang Chen
Thayer Lindsley Professor of Chemical Engineering
Columbia University

Abstract – Ocean acidification and climate change are expected to be two of the most difficult scientific challenges of the 21st century. Converting CO2 into valuable chemicals and fuels is one of the most practical routes for reducing CO2 emissions while fossil fuels continue to dominate the energy sector. The catalytic reduction of CO2 by H2 can lead to the formation of three types of products: CO through the reverse water-gas shift (RWGS) reaction, methanol via selective hydrogenation, and hydrocarbons through combination of CO2 reduction with Fischer-Tropsch (FT) reactions. In the current talk we will discuss some of our recent results in CO2 conversion via both heterogenerous catalysis and electrocatalysis. Our research approaches involve the combination of DFT calculations and surface science studies over single crystal surfaces, evaluations over supported catalysts, and in-situ characterization under reaction conditions. We will also discuss challenges and opportunities in this important research field.
Biography – Jingguang Chen is the Thayer Lindsley Professor of chemical engineering at Columbia University. He received his PhD degree from the University of Pittsburgh and then carried out his Humboldt postdoctoral research in Germany. After spending several years as a staff scientist at Exxon Corporate Research he started his academic career at the University of Delaware in 1998, and then took the roles as the director of the Center for Catalytic Science and Technology and the Claire LeClaire Professor of chemical engineering. He moved to Columbia University in 2012. He is the co-author of 20 US patents and over 300 journal articles with over 12,000 citations. He received many awards, including the awards from the catalysis clubs of Philadelphia (2004), New York (2008), Chicago (2011) and Michigan (2015). He recently won the 2015 George Olah award from the American Chemical Society.