Pervasiveness of Surface Metal Oxide Phases In Mixed Oxide Catalysts

Meeting Program – October 2012

 
Israel E. Wachs
Operando Molecular Spectroscopy & Catalysis Laboratory
Department of Chemical Engineering
Lehigh University
Bethlehem, PA 18015 USA

 
Abstract – Mixed oxide catalytic materials possess two or more metal oxide components as found in bulk mixed metal oxides (stoichiometric oxides as well as solid solutions), polyoxo metalates (POMs), molecular sieves, zeolites, clays, hydrotalcites and supported metal oxides. Although it is now well established that two-dimensional surface metal oxide phases are present for supported metal oxides on traditional supports (e.g., Al2O3, TiO2, ZrO2, SiO2, etc.), it is not currently appreciated that such surface metal oxide species or phases are also present for other types of mixed oxides. For example, recent surface analyses have demonstrated that stoichiometric bulk mixed metal oxides also possess surface metal oxide phases that control their catalytic activity. For example, the catalytic active sites for methanol oxidation to formaldehyde over the bulk Fe2(MoO4)3 mixed oxide catalyst are surface MoOx species and not the bulk Fe2(MoO4)3 phase as previously thought in the catalysis literature. The nanometer sized clusters in POMs also possess surface species when a second metal oxide component is introduced (e.g., H3+xPW12-xMxO40). Deposition of metal oxides into molecular sieves, zeolites, clays and hydrotalcites also results in the metal oxide additive usually being present as surface metal oxide species that are the catalytic active sites for many redox and acid reactions. The formation of these surface metal oxide phases is driven by their low surface free energy and low Tammann temperature for many metal oxides of interest in catalysis (e.g., VOx, MoOx, CrOx, ReOx, WOx, etc.).
 
Biography – Israel E. Wachs received his undergraduate education at The City College of The City University of New York where he graduated with a B.E. (ChE) in June, 1973. He received several recognitions upon graduation (AIChE Award for Outstanding Senior, Heller Memorial Award for Outstanding Scholastic Achievement, and White ChE Alumni Award). He continued his graduate ChE education at Stanford University under the mentorship of Professor Robert J. Madix in the area of surface science, and graduated with a PhD (ChE) in 1978. His research findings are considered the first application of surface science to catalysis, and his thesis publications are extensively cited in the surface science and catalysis literature.
 
INDUSTRIAL YEARS (1977-1986) – Israel joined Exxon Research & Engineering Company in their Corporate Research Labs towards the end of 1977. At Exxon, he was involved with many different catalytic technologies over the years (selective oxidation, acid catalysis, synthesis of synthetic fuels, hydrodesulfurization (HDS) and hydrocarbon conversion). He obtained 100 USA and international patents during his industrial career. One of his inventions on the selective oxidation of o-xylene to phthalic anhydride became the leading international industrial catalyst for this technology and is still used around the world. At Exxon, he received the Research Incentive Award for one of his inventions on the synthesis of synthetic fuels and was also selected to be an Exxon Fellow for the spring semester of 1986 at California Institute of Technology (CalTech). He departed for academia at the end of 1986.
 
ACADEMIC YEARS (1987-present) – He joined the Chemical Engineering Department of Lehigh University in January 1987. At Lehigh, he taught many different courses over the years: Heterogeneous Catalysis, Reactor Engineering, Fluid Mechanics, Professional Development, Unit Operations, Environmental Catalysis, and Air Pollution Control. He set up a world-class catalysis research laboratory focusing on mixed metal oxide catalytic materials and their characterization under reaction conditions (in situ and operando spectroscopy). These studies have established the foundation for the molecular/electronic structure – activity/selectivity relationships and the molecular engineering of mixed metal oxide catalysts. The research performed by Wachs and his students is well known around the world. This is reflected in the many national and international honors he has received over the years as well as ~17,000 citations to his publications with an H-index of 70 (one of the highest among heterogeneous catalysis researchers).

The current focus of Wachs’ catalysis laboratory is to develop catalyst characterization techniques under reaction conditions, referred to as operando spectroscopy in the recent literature. The term operando spectroscopy implies that the catalyst characterization information is being conducted simultaneously with online product analysis. Along these lines, Professor Wachs has developed instrumentation that can simultaneously obtain Raman, IR and UV-vis spectroscopic information and product analysis with an online mass spectrometer/GC system. This cutting-edge instrument is allowing Professor Wachs’ catalysis research group to rapidly develop molecular/electronic structure – catalytic activity/selectivity relationships for many different catalytic materials and reactions (selective hydrocarbon oxidation, hydrocarbon conversion with solid acid catalysts, gas-to-liquids, photocatalytic splitting of water, enzyme catalysis, CO2 capture, WGS, nanocatalysis, rational catalyst design, etc.).

Water Gas Shift over Industrial Cu Catalysts: A Mechanistic and Microkinetic Investigation

Meetimg Program – September 2012

 
Rostam J. Madon
BASF Corporation
25 Middlesex/Essex Turnpike
Iselin, NJ, USA 08830
rostam.madon@basf.com

 
Abstract – Low temperature water gas shift (LTS) is a commercially important reaction that takes place over a Cu-ZnO-Al2O3 catalyst. A large number of fundamental studies have been carried out for this reaction including investigations of the reaction mechanism as typified by Refs. [1-4]. In short, discussions have centered around (a) the redox mechanism in which adsorbed H2O is dissociated to O* and OH* and the O* is removed via CO* to form CO2 – where * is an active site, and (b) formate as a reactive intermediate. Recently, Gokhale et al. [5] using a DFT investigation of the LTS reaction on Cu(111) proposed a new mechanism that involves a reactive surface carboxyl. Our study is aimed at resolving which elementary steps best describe the catalytic cycle for the LTS reaction. To achieve this, we used the microkinetic modeling methodology pioneered by Dumesic [6], and analyzed our reactivity data using all elementary steps, including those that described the redox mechanism, the formate mechanism, and the carboxyl mechanism. Thus, we ensured that there was no bias towards any particular reactions to fit our data. We found the closed catalytic cycle for LTS on Cu consists of eight elementary steps that include the formation of COOH*, and its reaction with OH* to form CO2* and H2O*. The cycle does not include the reaction of CO2* and H* to form surface formate. However, this is an important side reaction, which ensures significant coverage of bidentate formate species on the Cu surface. Bidentate formate is a spectator species whose coverage increases with increasing pressure and decreases with increasing temperature. In summary, our investigation demonstrates that the redox and formate mechanisms are not relevant, and that the LTS catalytic cycle involves the formation and reaction of surface carboxyl. Several related aspects of the LTS reaction on Cu will also be discussed.
 

References

  1. Ovesen, C. V., et al. J. Catal. 158, (1996), 170.
  2. Koryabkina, N. A. et al. J. Catal. 217, (2003), 233.
  3. Rhodes, C., Hutchings G.J., and Ward A.M. Catal. Today 23, (1995), 43.
  4. Herwijnen, T.V., and de Jong, W. A. J. Catal. 63, (1980), 83 and 94.
  5. Gokhale, A. A., Dumesic, J. A., and Mavrikakis, M. J. Am. Chem. Soc. 130, (2008), 1402.
  6. Dumesic, J. A., et al. “The Microkinetics of Heterogeneous Catalysis”, American Chemical Society, Washington, D. C., 1993.

 
Speaker Bio – Ross completed his undergraduate studies in chemical engineering at the University Department of Chemical Technology, Mumbai, India. He did his graduate work at Stanford University, obtaining his Ph.D. under the guidance of Professor Michel Boudart. After completing his post-doctoral work with Professor W. Keith Hall at the University of Wisconsin – Milwaukee, Ross joined Exxon Research and Engineering Company. After 12 years with Exxon’s Corporate Research Laboratories, Ross joined Engelhard Corporation. Ross recently completed 25 years at Engelhard/BASF Corporation where he is currently a Senior Research Associate.

Ross has made pioneering contributions to the chemistry and engineering of catalytic processes. Early in his career with his advisor Michel Boudart, he developed an experimental method to address artifacts in kinetic data; a test accepted today as being definitive for kinetic control in catalysis. At Exxon, Ross’ studies in Fischer-Tropsch synthesis demonstrated the crucial role intraparticle diffusion played in enhancing hydrocarbon chain length and in changing selectivity. At Engelhard, he developed important concepts in fluid catalytic cracking to help design commercial catalysts. He elucidated the mechanism by which vanadium causes structural degradation of Y zeolite in FCC catalysts, and used this understanding to minimize its deleterious effect. His studies provided a definite assessment of the role of ZSM-5 additives in FCC to form light olefins and high octane gasoline. And, he defined the critical role rare earth cations play in Y-based FCC catalysts, demonstrating how the presence of rare earth influences hydride transfer reactions and product selectivity in FCC. Most recently, at BASF, Ross, together with colleagues in academia, elucidated the mechanism of the water gas shift reaction on copper, evincing parameters that could significantly improve catalytic activity. Importantly, though, Ross has used his conceptual and mechanistic approach to catalyst research to design commercial catalysts. He is the coinventor and developer of the Reduxion – Maxol® family of FCC catalysts and of the IsoPlus® and Ultrium® families; all of which have been used commercially worldwide. He coinvented the Flex-Tec® resid cracking catalyst which has been widely and successfully deployed in demanding resid cat-cracking processes. And most recently he has developed several copper based catalysts for the petrochemical industry.

Ross chaired the 1996 Gordon Research Conference on Catalysis, and in 2009 was awarded the AIChE Catalysis and Reaction Engineering Division Practice Award.

Commercialisation of a Novel Methyl Methacrylate Process – Catalyst Design and Development

2012 Spring Symposium

 
David W. Johnson
Lucite International UK Ltd

Abstract – A brief outline of Lucite International’s new “Alpha” methyl methacrylate technology is described including process scale up and the first exploitation in Singapore in late 2008. The technology was developed from 0.5g/h lab scale to 500g/h pilot and thence directly to 12te/h commercial scale. The plant was commissioned from first introduction of chemicals to 100% rate within 3 weeks and currently operates at over 16te/h with exceptional reliability.

Two catalytic steps are key to the technology. In the first, carbon monoxide, ethylene and methanol are reacted in solution with a novel palladium phosphine catalyst which gives methyl propionate in 99.9+% selectivity in a continuous process at ppm level palladium concentrations at 100C and 10bar total pressure. The catalyst activity and life is very sensitive to operating conditions. After extensive process development, activities of 15,000 moles/mole Pd/h and life of >1x107moles methyl propionate/mole Pd are routinely achieved on the commercial plant.

The second stage catalyst, composed of caesium/zirconia/silica reacts methyl propionate with formaldehyde at 330C and 1-2barg to form methyl methacrylate (MMA) and water. The selectivity is about 93% to MMA based on methyl propionate and over 80% on formaldehyde fed. The presentation describes some of the steps in development of the catalyst including comparisons with catalysts for similar process disclosed by competitors. A discussion of the mechanism of formation of MMA and byproducts is made in terms of surface reactions between reactants and products. A 2-site model is proposed involving both strongly basic and hydroxylic, weakly acidic sites. Reactions catalysed in byproduct formation include decarboxylations, combined condensation-decarboxylations, hydride transfers and acid catalysis. Lucite has found that competitive catalysts have the wrong balance of acidity and basicity and result generally in high levels of hydride transfer and acid catalysis products.

Speaker’s Biography: The author has a BA (Natural Sciences, Chemistry) from Oxford University a PhD in radiation chemistry and carried out postdoctoral research in LEED/XPS/UPS before joining ICI Ltd in 1977. Within ICI he worked initially on nitrate promoted silver ethylene oxide catalysts followed by 4 years in ICI’s New Science Group studying the structure of novel zeolites synthesised by ICI co-workers. Since 1990 he has worked in the area of MMA process design and led the exploratory research team which defined the Alpha process and currently leads Lucite’s (formerly ICI Acrylics) chemistry team. His current interests are process improvement for the Alpha technology and introduction of biotechnology into MMA manufacture.

Challenges in Catalysis Applied to Pharmaceutical Development

2012 Spring Symposium

 
Alan M. Allgeier
DuPont (formerly Amgen Inc.)

Abstract – In the development of pharmaceuticals, catalysis plays a critical role and its practitioners must nimbly assimilate knowledge of organic chemistry, surface reactions, reaction engineering and product isolation. In this presentation we explore three themes in catalysis for the pharmaceutical industry: 1) Enabling New Reactivity, 2) Quality… Above All Else and 3) Speed to Decisions… Speed to Market.

New Reactivity: Asymmetric hydroformylation of norbornene and utilization of ketolactols as aldehyde surrogates in reductive amination are described as novel chemistries demonstrated on clinical manufacturing scale. In the latter case, density functional theory provides insight into the mechanism of the reaction.
Quality: The use of precious metal catalysts engenders challenges of removing potentially toxic metals to meet quality specifications. The emerging technique of HPLC with ICP/MS detection is a valuable tool for understanding the diversity of residual metal complexes and identifying process options to clear metal impurities. In one such development effort a unique dearomatization reaction was characterized and its mechanism elucidated.

Speed: In conducting hydrogenation catalysis for pharmaceuticals catalyst deactivation is inevitably observed at some stage of development. In one case deactivation was particularly dependent upon gas to liquid mass transfer rates in batch reactors. A method for measuring the volumetric mass transfer coefficient (kLa) is described. Using this information reduces risk associated with scale up from laboratory to manufacturing equipment.

Speaker’s Biography – Alan Allgeier grew up in the beautiful countryside of northwest Pennsylvania. He earned his Ph.D. in Inorganic Chemistry in 1997 from Northwestern University under the direction of Prof. Chad Mirkin. He completed post-doctoral studies in heterogeneous catalysis at DuPont under Dr. Theodore Koch and continued at DuPont working on hydrogenation processes for nylon monomers and specialty chemicals, as well as, homogeneously catalyzed olefin hydrocyanation for specialty chemical applications. In 2004 Dr. Allgeier moved to Amgen to establish a competency in heterogeneous catalysis and pressure chemistry in support of drug discovery and development. In 2011 he returned to DuPont to lead a laboratory in the Surface and Particle Science Competency. Through his career Dr. Allgeier has been a leader in professional organizations including Arrangements Chair, Program Chair, Treasurer and Chair of the Philadelphia Catalysis Club, Board member of the 19th North American Catalysis Society Meeting, and Chair of the Organic Reactions Catalysis Society and its 23rd Conference. He is a contributing author / inventor of sixteen journal articles and fourteen patents or patent applications and served as Guest Editor for Topics in Catalysis. His technical interests include catalytic reactions for hydrogenation, carbonylation, and coupling, as well as, catalyst deactivation and reactor design.

Density Functional Theory Studies of Electrocatalysis

2012 Spring Symposium

 
Michael J. Janik
Department of Chemical Engineering
Pennsylvania State University


Abstract – Density functional theory (DFT) methods are widely used to evaluate surface catalytic reaction mechanisms and to predict the relative performance of various catalyst formulations or structures. The use of model systems, such as the single-crystal surface, to examine catalytic properties is well-established, with the gaps between model systems and realistic supported catalysts relatively understood. Translation of DFT approaches to the electrocatalytic environment requires additional methodological choices due to additional complexities offered by the electrified catalyst-electrolyte interface. This talk will provide an overview of these challenges and the various DFT approaches used to model electrocatalytic systems. The use of DFT to determine electrocatalytic reaction mechanisms and guide the design of catalytic materials will be discussed using examples from our group’s research; borohydride oxidation, oxygen reduction, and carbon dioxide reduction.

Speaker’s Biography – Dr. Janik is an assistant professor of Chemical Engineering at PSU, beginning his appointment August, 2006. His research interests are in the use of computational methods to understand and design materials for alternative energy conversion systems. Current activities address a wide-range of energy technologies including fuel cells and batteries, hydrogen generation, desulfurization, and CO2 capture. Research methods emphasize atomistic simulation using quantum chemical methods and kinetic modeling. Janik is affiliated with the PSU Electrochemical Engine Center, Battery and Energy Storage Technology Center and the PSU Institutes of Energy and the Environment. Janik is the director of a National Science Foundation supported Research Experience for Undergraduates cite in “Chemical Energy Storage and Conversion.” The Janik research group currently includes 8 graduate students and 11 undergraduate students. Dr. Janik received his B. S. in Chemical Engineering from Yale University. Following three years as a Process Engineer for Procter and Gamble, Janik completed his doctoral studies at the University of Virginia. Janik completed his doctoral thesis in 2006 examining acid catalysis by polyoxometalates followed by post-doctoral work studying methanol electrooxidation. He is the author of approximately 50 peer reviewed papers.

Desktop Molecular Modeling Help in Clarifying Odd Experimental Observations on Zeolites and Silica Gels

2012 Spring Symposium

 
Istvan Halasz
PQ Corporation

Abstract – Zeolites and amorphous silica gels are widely used in adsorption and catalysis. PQ commercializes silica based materials by tailoring them to specific customer needs worldwide. These modifications usually require series of material tests which mostly carried out at the company’s R&D Center where I have been assigned to investigate the porosity, acidity, sorption capacity, activity and other targeted properties of experimental and commercial products. Sometimes these experiments lead to unexpected, surprising, contradictory results which usually generate various speculative explanations. In this presentation I’ll illustrate through a few examples how molecular modeling can help in resolving conflicts between ideas and empirical findings. I intend to show that the commonly available computer power and modeling programs have developed so much during the past few years that even an experimentalist with limited resources and theoretical background can mimic various empirical data which is the basis to understanding material properties at the molecular level. It will be also shown how computer chemistry can lead to improved quantification of otherwise routinely measured molecular spectroscopic data. The presented examples will include model calculations based on force field related Monte Carlo algorithm, time dependent density functional theory, and a combination of quantum mechanical/molecular mechanical methods. Simulated experimental sorption isotherms and FTUV spectra of two hydrophobic zeolites will be presented to explain their unusual sorption properties and redox catalytic activities. Moreover, we compare the model and experimental FTIR and laser Raman spectra of some amorphous silicates and present the first experimental proof that silica gels obtained from aqueous alkaline silicate solutions or tetra-ethyl-orthosilicate at acidic or basic conditions can have distinct molecular structures which affect their final physical properties.

Speaker’s Biography – Istvan obtained a physics and chemistry teacher diploma from the Lajos Kossuth University, Hungary. Later he was awarded magna cum laude doctorate degree from the same university and a higher degree from the Hungarian Academy of Sciences, HAS. Following three years of teaching physical chemistry, he joined the Hungarian Hydrocarbon Institute, where he developed new, economic processes for pharmaceutical, fine chemical and petrochemical plants and studied the fundamentals of acid-base catalysis over metal oxides. As a young scientist he won several competitive awards and a research scholarship for the University of Technology in Vienna, Austria. After 12 years of industrial research, he moved to the Chemical Research Institute of HAS where his major research topics included shape selective catalysis on zeolites and synthesis of high temperature ceramic superconductors. Istvan also worked as postdoctoral researcher at Wayne State University and University of Iowa, focusing mainly on the catalytic abatement of automobile exhausts and industrial stack gases. He joined PQ nearly 14 years ago. He has been member of several scientific organizations and currently serves as president of NECZA (North East Corridor Zeolite Association). Istvan has authored and co-authored more than 180 publications.

Consequences of Acid Strength and Solvation in Catalysis Mediated by Ion-pair Transition States

2012 Spring Symposium

 
Enrique Iglesia
Department of Chemical Engineering
University of California at Berkeley and Chemical Sciences Division
E.O. Lawrence Berkeley National Laboratory


Abstract – The rate and selectivity of reactions catalyzed by acids depend on the stability of ion-pairs at transition states that mediate kinetically-relevant steps. Rates and selectivities for alkanol dehydration and homologation, alkene and cycloalkene isomerization, and alkoxide scission and hydrogen transfer on polyoxometalate and zeolitic acids show that sensitivity to acid strength reflects differences in the amount and diffuseness of the charge in the relevant precursors and the transition states. The effects of solvation by confinement on rates and selectivities depend, in turn, on their respective differences in size. The known structures of these acids allow rigorous comparisons between experiment and theory, which confirm the mechanistic interpretations of rate data and the relevance of deprotonation energies as theoretical proxies of acid strength. These studies and insights suggest a rigorous reactivity-based ranking of acid strength that can be used to assess the strength of solid acids with uncertain or non-uniform structures.

Speaker’s Biography – Enrique Iglesia is the Theodore Vermeulen Chair in Chemical Engineering at the University of California at Berkeley and a Faculty Senior Scientist in the Lawrence Berkeley National Laboratory. He received his B.S. from Princeton University and his Ph.D. degree from Stanford University with Professor Michel Boudart and joined the Berkeley faculty in 1993 after 12 years in research and leadership positions at the Corporate Research Labs of Exxon. He has served as Editor-in-Chief of Journal of Catalysis and is the President of the North American Catalysis Society and the Director of the Berkeley Catalysis Center. He has co-authored more than 300 articles in the leading journals in chemistry and chemical engineering and is a co-inventor in 38 U.S. patents. He is a member of the National Academy of Engineering and a Fellow of the American Chemical Society. His research has been recognized with the Somorjai and Olah Awards of the American Chemical Society, the Award for Excellence in Natural Gas Conversion, the Alpha Chi Sigma and Wilhelm awards of the American Institute of Chemical Engineers, the Emmett and Burwell Awards of the Catalysis Society, the Tanabe Prize in Acid-Base Catalysis, the Canadian Chemical Society Cross Canada Lectureship, and the Francois Gault Award of the European Federation of Catalysis Societies. His research interests include the synthesis and structural and mechanistic characterization of novel inorganic solids useful as catalysts in chemical reactions of critical importance in energy conversion, sustainable synthesis of energy carriers and petrochemicals, and pollution prevention and environmental control.