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

Meeting Program — April 2016

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
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
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
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.

Engineering Molecular Transformations over Supported Metal Catalysts for the Sustainable Conversion of Biomass-Derived Intermediates to Chemicals and Fuels

Meeting Program — October 2015

Matt Neurock
Shell Professor of Chemical Engineering and Materials Science
University of Minnesota

Abstract — Future strategies for energy production will undoubtedly require processes and materials that can efficiently convert sustainable resources such as biomass into fuels and chemicals. While nature’s enzymes elegantly integrate highly active centers together with adaptive nanoscale environments to control the catalytic transformation of molecules to specific products, they are difficult to incorporate into large scale industrial processes and limited in terms of their stability. The design of more robust heterogeneous catalytic materials that can mimic enzyme behavior, however, has been hindered by our limited understanding of how such molecular transformations proceed over inorganic materials. The tremendous advances in ab initio theoretical methods, molecular simulations and high performance computing that have occurred over the past two decades provide unprecedented ability to track these transformations and how they proceed at specific sites and within particular environments. This information together with the unique abilities to follow such transformations spectroscopically is enabling the design of unique atomic surface ensembles and nanoscale reaction environment that can efficiently catalyze specific molecular transformations. This talk discusses recent advances in computational catalysis and their application to engineering molecular transformations for the conversion of biomass into chemicals and fuels. We will discuss the active sites, mechanisms and nanoscale reaction environments involved in specific bond making and breaking reactions important in the conversion of biomass-derived intermediates into chemicals and fuels and the design of 3D environments necessary to carry out such transformations.

Biography — Matt Neurock is the Shell Professor of Chemical Engineering and Materials Science at the University of Minnesota. He received his B.S. degree in Chemical Engineering from Michigan State University and his Ph.D. from the University of Delaware in 1992. He worked as a Postdoctoral Fellow at the Eindhoven University of Technology in the Netherlands from 1992–1993 and subsequently as Visiting Scientist in the Corporate Catalysis Center at DuPont from 1993–1994. He joined the faculty in Chemical Engineering at the University of Virginia in 1995 where he held joint appointments in Chemical Engineering and Chemistry. In 2014 he moved to the University of Minnesota and is currently on the faculty in Chemical Engineering and Materials Science. He has made seminal advances to development and application of computational methods toward understanding catalytic and electrocatalytic reaction mechanisms, and the sites and environments that carry out reactions under working conditions. He has received various awards for his research in computational catalysis and molecular reaction engineering including the Robert Burwell Lectureship from the North American Catalysis Society, R.H. Wilhelm Award in Chemical Reaction Engineering from the American Institute of Chemical Engineers, Paul H. Emmett Award in Fundamental Catalysis from the North American Catalysis Society, Distinguished Visiting Professor of University of Montpellier, Eastman Chemical Lecturer at the University of California Berkeley, Richard S. H. Mah Lecturer at Northwestern University, Johansen-Crosby Lecturer at Michigan State University, NSF Career Development Award, DuPont Young Investigator Award, Ford Young Faculty Award. He has co-authored over 240 papers, two patents and two books. He is an editor for the Journal of Catalysis and serves on numerous other editorial and advisory boards.

Catalysis for renewable fuels and chemicals: Challenges today and a look into where we are going

Meeting Program — November 2015

John Holladay
Biomass Sector Manager, and Associate Director of the Institute for Integrated Catalysis
Pacific Northwest National Laboratory

Abstract — Renewable carbon sources, such as biomass and sugars, offer alternative starting materials for producing fuels and chemicals. However, catalysis of highly oxygenated materials, often operating in the condensed phase, present substantial challenges with catalyst deactivation due to poisoning and reactor bed/support stability. In essence, the catalysts developed within the petrochemical industry are often not suitable and new solutions are needed if we are to match the efficiency that has been born from nearly 90 years of science and technology aimed at hydrocarbon processing.

In covering challenges today we will survey two families of catalytic technologies that produce fuels—with an emphasis on distillates and mid-distillates and chemical products. These technologies will cover (i) upgrading of oxygenates (from alcohols to complex bio-oils) and (ii) catalysis of fermentation derived molecules that have been minimally processed. The primary focus will be on problems and specific solutions that allowed long term, stable and efficient operation under continuous reaction conditions suitable for industry.

In part 2 of the lecture we will take a forward look toward where we would like to move the state of catalyst technology to allow processing of a broader range of carbon from waste resources at the (small) size of the point source while keeping capital and operating cost low. Such feedstocks include gaseous streams, such as CO-rich off gas; wet streams from food processing and waste water sludges; as well as dry streams from agriculture and forest residues or municipal solid waste.

Biography — John Holladay joined the Pacific Northwest National Laboratory (PNNL) in 2001 after working for five years at Union Carbide in South Charleston, WV. John currently serves as the Biomass Sector Manager at PNNL, where he is responsible for shaping PNNL’s strategy and vision for renewable fuels and chemicals. The program focuses on multiple areas including: developing cost-effective catalysts for renewable carbon conversion, learning from the efficiency that fungi offers for naturally processing biomass, and understanding alternative means for producing biomass in waste streams that are wet/dry or gaseous. He facilitates PNNL’s collaboration with others in academia, industry and government to advance the nation’s biofuels research. He served as Chief Scientific Officer for the National Advanced Biofuels Consortium, Chief Operations Officer for the National Alliance for Biofuels and Bioproducts and is currently an Associate Director of the Institute for Integrated Catalysis at PNNL.

Catalysis – An Indispensable Tool

Meeting Program — September 2015

Sourav Sengupta
Molecular Sciences, CR&D
E. I. DuPont de Nemours & Co
Wilmington, DE
sourav.sengupta@dupont.com

Abstract — In the past three decades, there has been a concerted effort in the chemical, agrochemical, pharmaceutical, nutraceutical, and petroleum industries to design cost-advantaged, inherently safer, sustainable, and environmentally-friendly processes. Catalysis plays a crucial role in improving process efficiencies and process intensification leading to increased atom utilization, reduced by-product formation, cheaper process, and lower capital investment. Also, there is an increasing interest in using renewably-sourced feedstocks for the production of fuels, chemicals, and advanced materials due to fluctuations in petroleum prices, limited availability of petroleum resources, and increasing consumer consciousness about sustainable processes.

Although catalysis is a major tour-de-force in driving this efficacious and green chemistry revolution, the role of reaction engineering, reactor design, process development, and optimum operating conditions cannot be underestimated. Some of the fundamental concepts of catalysis will be discussed and linked to chemical processes of industrial relevance. Specifically, the role of science and engineering in industrial catalysis will be illustrated with particular emphasis on catalyst evaluation, process optimization, catalyst deactivation, and reactor design associated with industrial processes. Case studies will include hydrogenation reactions using supported base metal and precious metal catalysts and solid acid catalyzed reactions, including the hydrogenation of hexafluoroacetone and catmint oil, and dehydration of xylose.

Biography — Dr. Sourav K. Sengupta is a Research Fellow in the Molecular Sciences Division (Central Research & Development Department) of E. I. DuPont de Nemours & Co. He received his PhD degree in Chemical Engineering from the University of Delaware in 1991. Immediately after completing his PhD, Dr. Sengupta joined the DuPont Company and was placed on loan to Conoco where he developed novel pathways for the oxidative desulfurization of gasoline and qualified new hydrodesulfurization and FCC catalysts. Shortly afterwards, he was transferred to the Corporate Catalysis Center (CR&D). At CR&D, he worked on solid acid, solid base, and hydrogenation catalysis programs and made important contributions to a number of Strategic Business Unit (SBUs).

Dr. Sengupta spent several years at DuPont’s Nylon business unit, where he worked on a number of commercial processes and research programs, including low-pressure and high-pressure ADN hydrogenation, hydrogen cyanide synthesis by Andrussow and induction-heating processes, and nitrous oxide destruction catalyst technology.

When DuPont sold their Nylon, polyester, and Lycra businesses to Koch Industries, Dr. Sengupta joined Invista, a wholly-owned subsidiary of Koch Industries, where his work involved investigating the technical and economic feasibility of caprolactam commercialization.

After a short stint at Invista, Dr. Sengupta came back to DuPont, and joined their Chemical Solutions Enterprise (DCSE) as a manufacturing technical chemist at Chambers Works in New Jersey. His responsibility covered 42 different specialty chemicals. There he worked with a team of experts to design, develop, and commercialize a novel hydrogenation process for the production of hexafluoroisopropanol (HFIP) and hexafluoroacetone (HFA) recovery process. He was also involved in the commercialization of a number of Capstone products. In 2009, he started up a Process Development Center for DCSE at the Experimental Station. In 2011, he moved back to CR&D and has been working on a number of R&D programs on using renewable feedstock to manufacture chemicals and materials and new catalyst development.

Dr. Sengupta’s expertise is in the area of catalysis, reaction engineering and reactor analysis, and process development. He has over 65 US patents, publications, and presentations to his credit.

Catalysis Club of Philadelphia

Promoting the science of catalysis since 1949.