Explor­ing the Cat­alytic Prop­er­ties of Cu/SSZ-13 using NO Oxi­da­tion and Stan­dard Selec­tive Reduc­tion of NO with NH3

2014 Spring Symposium

Fabio H. Ribeiro*1, W. Nicholas Delgass1, William F. Schneider2, Jeffrey T. Miller3, Aleksey Yezerets4, Trunojoyo Anggara2, Christopher Paolucci2, Shane A. Bates1, Anuj Verma1, and Atish Parekh1
1School of Chemical Engineering, Purdue University, West Lafayette, Indiana 47907 (USA)
2Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana
46556 (USA)
3Argonne National Laboratory, Darien, IL 60439 (USA)
4Cummins Inc., Columbus, IN 47202 (USA)

Abstract – The Cu/SSZ-13 catalyst (CHA framework) is preferred for SCR applications because it shows both SCR performance and hydrothermal stability. In this work, the site requirements of the Standard SCR and NO oxidation reactions have been studied on Cu/SSZ-13. Based on an integrated experimental and modeling approach, the active site for the Standard SCR on Cu/SSZ-13 has been assigned to an isolated Cu ion located near the 6 member rings of SSZ-13, while NO oxidation required local Cu – O – Cu bonds in the 8 member cage of SSZ-13. The formation of local Cu – O – Cu bonds was a result of saturation of the number of favorable Al pairs near the 6 member ring to stabilize isolated Cu ions. The variation of the NO oxidation and the SCR rates of reaction with Cu/Al ratios was thus a catalytic consequence of different Cu ion configurations within SSZ-13. The working state of catalyst under SCR, moreover, was examined by Operando X – Ray Absorption Spectroscopy (XAS). Under reaction conditions, the Standard SCR involved a redox mechanism with both Cu(I) and Cu (II) species present. Further experiments using operando XAS to probe the redox cycle of Cu were carried out by removing the oxidizing half-reaction, which produced mostly the Cu(I) state, and then the reducing half reaction, which produced mostly the Cu(II) state. Thus, any mechanism of Standard SCR has to incorporate a redox cycle. In summary, the standard SCR on Cu-SSZ13 required isolated Cu ions to undergo a redox cycle near the 6 member ring of SSZ13.
Fabio_H_RibeiroBiography – Fabio H. Ribeiro is currently the R. Norris and Eleanor Shreve Professor of Chemical Engineering at the School of Chemical Engineering, Purdue University. He received his Ph.D. degree from Stanford University in 1989, held a post-doctoral fellowship at the University of California – Berkeley, and was on the Worcester Polytechnic Institute faculty before joining Purdue University in August 2003. His research interests consist of the kinetics of heterogeneous catalytic reactions and catalyst characterization by in situ techniques. He was Chair for AIChE’s Catalysis and Reaction Engineering Division (2010) and is editor for Journal of Catalysis.

Nanoporous Mate­ri­als for Solar Fuel Pro­duc­tion

2014 Spring Symposium

Feng Jiao
Department of Chemical and Biomolecular Engineering
University of Delaware
Newark, DE 19716

Abstract – Solar fuel production is an important technological challenge, considering that the energy of sunlight that strikes the earth’s surface in an hour is sufficient to meet our energy demands for a year. Irrespective of the approach that is pursued, oxygen evolution from water is the critical reaction, because water is the only cheap, clean and abundant source that is capable of completing the redox cycle for producing either hydrogen (from H2O) or carbonaceous fuels (from CO2) on a terawatt scale. Here, we will show our recent studies in mesoporous spinel systems, which suggest the metal sitting at the octahedral site has huge impact on the water oxidation activity of spinel catalysts. Another topic will be discussed in the presentation is the development of selective and robust CO2 reduction electrocatalyst. We will present a nanoporous Ag electrocatalyst, which is able to electrochemically reduce CO2 to CO with a ~92% selectivity at a rate (i.e. current) of over 3000 times higher than its polycrystalline counterpart under a moderate overpotential of less than 0.50 V. Such an exceptionally high activity is a result of a large electrochemical surface area (ca. 150 times larger) and intrinsically high activities (ca. 20 times higher) compared to polycrystalline Ag.
Feng_JiaoBiography – Feng Jiao obtained his BS in chemistry at Fudan University (2001) and his PhD degree in Chemistry at University of St Andrews (Scotland, 2008), before moving to Lawrence Berkeley National Laboratory as a postdoc scholar. He spent two years in Berkeley developing solar fuel technology and joined in the Chemical and Biomolecular Engineering Department at the University of Delaware as an assistant professor in 2010. He has already published more than 35 journal papers in leading scientific journals, such as Nature Communications, J. Am. Chem. Soc., and Angew. Chem. Int. Ed. His research activities include synthesis of nanoporous materials and their potential applications in energy storage and conversion.

Sur­face Reac­tions of Biomass-Derived Poly­ols on Metal Oxides and Sup­ported Metal Cat­a­lysts

2014 Spring Symposium

Carsten Sievers
Georgia Institute of Technology
School of Chemical & Biomolecular Engineering
Atlanta, GA 30332

Abstract – Aqueous phase processes are expected to play a key role in the production of renewable chemicals and fuels from biomass. Facile separation makes heterogeneous catalysts an attractive option for achieving high efficiency in these processes. Unfortunately, little is known about the surface chemistry of biomass-derived oxygenates in an aqueous environment. However, this knowledge will be needed to improve the activity, selectivity, and stability of catalysts for aqueous phase processes to the level we are used to in vapor phase reactions. This presentation will focus on surface interactions of biomass-derived oxygenates with metal oxides (Al2O3, TiO2, ZrO2, CeO2, MgO, Nb2O5) and supported metal catalysts (Pt/Al2O3).

The surface chemistry of aqueous solutions of polyols on polar metal oxides is strongly affected by the competition between water and the polyols for adsorption sites. Directed interactions with specific surface sites dominate. Even in the presence of water, polyols with sufficient spatial separation between their alcohol groups (e.g. glycerol) can chemisorb on Lewis acid sites forming stable multidentate surface species. The frequencies of C-O stretching vibrations of participating groups scale linearly with the electronegativity of the metal atom providing an indication for reactivity trends in acid catalyzed reactions, such as dehydration. The surface species described here can also stabilize metal oxides like γ-Al2O3 against hydrolysis in hot liquid water that would otherwise deteriorate the material. Direct dehydration of adsorbed glycerol on the Lewis acid sites of Nb2O5 yields hydroxyacetone as the main products, whereas acrolein is formed when Brønsted acid sites are involved in the conversion.

In-situ spectroscopic studies provide additional insight into the kinetics of the conversion of oxygenates in water. Specifically, ATR-IR spectroscopy is used to demonstrate that Pt/Al2O3 readily activates biomass-derived oxygenates, such as glycerol, to form surface bound CO on the Pt particles. The number of available surface sites is increased when Pt/γ-Al2O3 is cleaned by hydrogen and oxygen saturated water. After this pretreatment, some of the Pt sites that bind bridging CO show activity for the water-gas-shift reaction even at room temperature.
Model Release-YESBiography – Carsten Sievers obtained his Diplom and Dr. rer nat. degrees in Technical Chemistry at the Technical University of Munich, Germany. Under the guidance of Prof. Johannes A. Lercher he worked on heterogeneous catalysts for various processes in petroleum refining including hydrogenation of aromatics in Diesel fuel, alkylation, alkane activation, and catalytic cracking. Additional research projects included novel catalytic system, such as supported ionic liquids. In 2007, he moved to the Georgia Institute of Technology to work with Profs. Christopher W. Jones and Pradeep K. Agrawal as a postdoctoral fellow. His primary focus was the development of catalytic processes for biomass depolymerization and synthesis of biofuels. He joined the faculty at the Georgia Institute of Technology in 2009. His research group is developing catalytic processes for the sustainable production of fuels and chemicals. Specific foci are on the stability and reactivity of solid catalysts in aqueous phase, surface chemistry of oxygenates in water, applied spectroscopy, physicochemical characterization of solid materials, synthesis of well-defined catalysts, methane conversion, pyrolysis, and gasification. He is President of the Southeastern Catalysis Society and Program Chair of the ACS Division of Catalysis Science & Technology.

Zn Mod­i­fi­ca­tion of Pt(111) for the Hydrodeoxy­gena­tion of Aldoses

2014 Spring Symposium

Jesse R. McManus, Eddie Martono, & John M. Vohs
University of Pennsylvania
Abstract – The high oxygen content and multiple functional groups in biomass-derived platform molecules like glucose pose an interesting reaction engineering challenge for the conversion of biomass to value-added fuels and chemicals. The key to understanding the reaction pathways necessary for these conversions lies in elucidating reaction active sites on catalytically relevant surfaces and identifying the role of each functionality exhibited by the feed molecule in the reaction mechanism. In this study, temperature programmed desorption (TPD) and high resolution electron energy loss (HREEL) spectroscopy are utilized to probe the reaction pathway of the biomass-relevant glucose molecule, as well as model aldoses glyceraldehyde and glycolaldehyde, and simple aldehyde acetaldehyde on a Pt catalyst surface. The effects of modification of the Pt(111) surface with oxyphilic Zn adatoms are explored with regard to hydrodeoxygenation chemistry, and reaction mechanisms are proposed. With all molecules studied, it was found that Zn addition to Pt(111) resulted in an increase in the barrier for C-H and C-C scission, as well as notable activity for deoxygenation at the aldehyde oxygen as a function of polyalcohol content. These results help elucidate the role of multiple alcohol functionalities in biomass-derived oxygenates and highlight the potential of using alloy effects to modify catalytic chemistry.
Jess_R_McManusBiography – Dr. Jesse R. McManus recently completed his PhD research in Chemical Engineering at the University of Pennsylvania under the tutelage of Prof. John M. Vohs, successfully defending his thesis “Reaction Characterization of Biomass-Derived Oxygenates on Noble Metal Catalysts”. In 2009, he received his BSE in Chemical Engineering at Tulane University, graduating Summa Cum Laude with an Honors distinction. During his studies, Dr. McManus has received several awards for his academic accomplishments, including the Tulane-Richards Scholarship for Academic Excellence, The R.C. Reed Scholar Award for academic achievement and promise for the future, and the Doctoral Franklin Scholar Award for students with high promise to succeed in creative research at the cutting edge of their discipline. In the spring, Dr. McManus plans to depart from academic research and pursue a career in the energy sector with a major energy company.

Alkene Metathe­sis for Propy­lene Pro­duc­tion over W-based Cat­a­lysts: Insights from Multi-Functional Cat­a­lysts and Met­al­la­cy­clobu­tanes

2014 Spring Symposium

Christopher P. Nicholas

Abstract – Tungsten oxide supported on silica is an efficient catalyst for olefin metathesis used in industrial processes since the 1960s. Several elements point to isolated metal centers as the active sites, and from the Chauvin mechanism, it is reasonable to expect that carbene species are involved, possibly bearing an oxide ligand in the metal’s ligand sphere. Owing to the strategic importance of olefins as building blocks for the world chemical industry, development of efficient processes is of utmost relevance. More specifically, tailored heterogeneous catalysts with known structure–activity relationships may improve lifetimes and have higher numbers of active sites.

With our collaborators, we have been studying tungsten hydride supported on alumina prepared by the surface organometallic chemistry method as an active precursor for metathesis processes at low temperature and pressure. Taoufik, et.al. showed that ethylene can be converted to propylene at very high selectivities of 99% via a tri-functional mechanism involving dimerization, isomerization and cross-metathesis of ethylene and the produced 2-butene. Recently, via a contact time study we revealed that the dimerization of ethylene to 1-butene is the primary and also the rate limiting step in this reaction and results in deactivation of the catalyst due to a side reaction like olefin polymerization producing carbonaceous deposits on the catalyst.

With that knowledge, we have also investigated performance of the catalyst in the presence of ethylene and butenes. At low temperature (120 °C) in the cross-metathesis of ethylene and 2-butene, the catalyst deactivates notably with time on stream. However, at 150 °C, the catalyst was stable with time and thereby gave a high productivity in propylene. The ratio of ethylene to trans-2-butene was also studied, and the W-H/Al2O3 catalyst is stable and highly selective to propylene even at sub-stoichiometric ethylene ratios.

Surprisingly, we have also been able to obtain propylene in high yields from butene only feeds. 1-butene and 2-butene are both able to be converted into propylene at higher selectivity than expected due to isomerization and metathesis occurring simultaneously. Then, by studying isobutene / 2-butene cross-metathesis, we observed that the catalytic cycle involving the less sterically hindered tungstacyclobutane intermediate governs the conversion rate of the cross-metathesis reaction for propylene production from butenes and/or ethylene.


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Christopher_P_NicholasBiography – Chris joined UOP in 2006 after earning a Ph.D. from Northwestern University and working in the Hard Materials Center of Excellence at Sigma-Aldrich. He has worked in the Catalysis and Exploratory Research departments and is currently focused on New Materials Research. Chris is an inventor or co-inventor on 30+ US and foreign patents and coauthor of 13 peer reviewed journal articles and a book chapter. He has been involved with the Chicago Catalysis Club since graduate student days and is currently serving as the Program Chair for the Chicago Catalysis Club. Chris’ research interests encompass the gamut of inorganic and catalytic technologies ranging from materials synthesis to characterization to catalyst and process development. He has particularly enjoyed understanding the relationship between homogeneous and heterogeneous catalysts.