5
Analysis of the Catalysis Science Program Portfolio

This chapter evaluates the research portfolio of the U.S. Department of Energy (DOE) Office of Basic Energy Sciences (BES) Catalysis Science Program in detail.

METRICS FOR EVALUATING THE CATALYSIS SCIENCE PROGRAM PORTFOLIO

In the assessments below, grants are evaluated in terms of the characteristics of the portfolio, their impacts on fundamental science, and their contributions to meeting near-term and long-term national energy goals. The second and third metrics are explained below.

Fundamental Advances in Science

Defining fundamental science is challenging. “I know it when I see it” is an adage to which many scientists would agree. However, the committee has been asked to judge whether the Catalysis Science Program has “advanced fundamental science in catalysis,” so we must have some generally shared definition of fundamental science in catalysis. For the purposes of this study, we will define fundamental science in catalysis as a general understanding of or insight into a catalysis system or material that is fundamental enough to be applied to more than one catalyst. Examples might be the development of quantitative models of a class of reactions (such as hydrocarbon oxidation) using a class of catalysts (such as noble metals), the synthesis of a new class of materials (such as zeolites), and the understanding of reaction or surface mechanisms of a class of catalysts (such as transition metal oxides).



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5 Analysis of the Catalysis Science Program Portfolio This chapter evaluates the research portfolio of the U.S. Department of Energy (DOE) Office of Basic Energy Sciences (BES) Catalysis Science Pro- gram in detail. METRICS FOR EVALUATING THE CATALYSIS SCIENCE PROGRAM PORTFOLIO In the assessments below, grants are evaluated in terms of the charac- teristics of the portfolio, their impacts on fundamental science, and their contri- butions to meeting near-term and long-term national energy goals. The second and third metrics are explained below. Fundamental Advances in Science Defining fundamental science is challenging. “I know it when I see it” is an adage to which many scientists would agree. However, the committee has been asked to judge whether the Catalysis Science Program has “advanced fun- damental science in catalysis,” so we must have some generally shared defini- tion of fundamental science in catalysis. For the purposes of this study, we will define fundamental science in catalysis as a general understanding of or insight into a catalysis system or material that is fundamental enough to be applied to more than one catalyst. Examples might be the development of quantitative models of a class of reactions (such as hydrocarbon oxidation) using a class of catalysts (such as noble metals), the synthesis of a new class of materials (such as zeolites), and the understanding of reaction or surface mechanisms of a class of catalysts (such as transition metal oxides). 55

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56 CATALYSIS FOR ENERGY Contributions to the Nation’s Energy Goals The effectiveness of the Catalysis Science Program can also be judged by measuring its contribution or likely contribution to meeting near-term and long-term national energy goals. Near-term and long-term national energy goals have been neither clearly stated nor static during the past 20 years. However, for the purposes of this study, we will consider energy goals to be any goals related to reducing the amount of energy we need (efficiency) or reducing our need to import oil immediately or over the long term. As described in Chapter 3, the Catalysis Science Program portfolio is distributed between the two main categories of catalysis: heterogeneous and homogenous, each of which will be assessed separately below. The committee has made this distinction for convenience, based on the traditional division in catalysis. However, researchers are increasingly crossing the traditional barriers between heterogeneous and heterogeneous catalysis, blurring the distinction between the two (see the discussion of Contractor Meetings in Chapter 4), which the committee definitely views as a positive development. The names of princi- pal investigators are provided in the assessments where appropriate, along with references to contractor meeting abstract books or published journal articles. Lists of all of the principal investigators who received funding during the fiscal years (FYs) 1999 to 2007 and FY 2008 are provided in Appendix F. HETEROGENEOUS CATALYSIS Heterogeneous catalysts are the catalysts most commonly used in in- dustrial processes. Heterogeneous catalysis involves the use of a catalyst (which is typically a solid) that is in a different phase from the reactants (which are typically gases). Heterogeneous catalysts range in composition from solid metals to encapsulated metal nanoparticles in solution. Virtually every drop of oil is in contact with multiple heterogeneous catalysts during the refining process. Most commodity chemicals are produced by heterogeneously catalyzed processes. Heterogeneous catalysis is also used extensively in environmental processes. Every car now has a heterogeneous catalytic converter in its exhaust system to remove toxic fumes. Heterogeneous catalysis is used to clean flue gases from power plants and to remove toxic gases or odors from industrial production. The use of heterogeneous catalysts to re- move sulfur compounds from oil products and to clean flue gases from power plants are the primary reasons for the considerable decrease in the amount of acid rain in recent years.

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57 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO Why Is Heterogeneous Catalysis Important for Energy? Heterogeneous catalysis is a key to developing energy-efficient, envi- ronmentally friendly processes for the conversion of fossil-energy feedstocks (coal, petroleum, natural gas, and tar sands) to usable products, including gaso- line and diesel oil. Because heterogeneous catalysis is heavily used in the chemical industry, its efficiency is extremely important. To understand its im- portance, consider the catalytic production of ammonia, which is used to make fertilizers and is instrumental in the world’s food production; this process alone accounts for more than 1 percent of the world’s energy consumption.1 Heterogeneous catalysis is also essential for new, sustainable energy processes. It is used to convert biomass to usable energy products. It also is a key to new photochemical and electrochemical processes for possible future sustainable production of fuels based on sunlight and for new efficient processes for using such fuels in fuel cells. In many cases, it is the lack of efficient cata- lysts that prevents new technologies for using chemical energy from being eco- nomically feasible today. Assessment of Heterogeneous Catalysis Portfolio The committee assessed the grants within the heterogeneous catalysis portfolio according to the subareas described below, which are based on how the grant information was provided by the Catalysis Science Program staff. Traditional heterogeneous: Individual investigator grants involving heterogeneous catalysis but not associated with any new programs or initiatives. Surface science: Grants focused on the understanding of heterogeneous catalytic surfaces and the advanced application of surface science or the development of new approaches within surface science. Nanoscience: Grants funded under the National Nanotechnology Initia- tive (NNI; http://www.nano.gov) or grants focused on emergent proper- ties at the nanometer scale. The NNI was established in FY 2001 to co- ordinate federal nanotechnology research and development. Catalysis Science: Grants funded under the Catalysis Science Initiative (CSI), first awarded in 2003 and to multi-investigator, multidisciplinary 1 Worrell, E., D. Phylipsen, D. Einstein, et al. 2000. Energy Use and Energy Intensity of the U.S. Chemical Industry. Lawrence Berkeley National Laboratory (LBNL-44314). Online. Available at http://industrial-energy.lbl.gov/node/86. Accessed February 2, 2009.

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58 CATALYSIS FOR ENERGY teams. The stated goal of the CSI is to “develop combined experimental and theoretical approaches to enable molecular-level understanding of catalytic reaction mechanisms, ultimately enabling the prediction of catalytic reactivity at multiple time and length scales.” Theory: Grants focused on theory, modeling, or simulation. Grants in other categories may also include theory but not as the focus of the re- search. Other initiatives: Grants funded by various DOE cross-cutting pro- grams. During FY 1999 to FY 2001, coal chemistry and noncatalytic reactions were included in this category. More recently, grants have in- cluded those under the Hydrogen Fuel Initiative (HFI; established in 2005) and in related fields, such as electrochemistry. The distribution of grants into the six subareas of the heterogeneous ca- talysis portfolio for the time period studied is provided in Table 5-1. Overall, during the past eight years (FY 1999 to FY 2007), there ap- pears to be appropriate retention in research topics with a slight shift in focus to such growing fields as nanoscience and theory. Considering the central role that catalysis plays in traditional and alternative fuel production and the level of funding that is available for the Catalysis Science Program, BES has done an impressive job during the past eight years of providing the nation with funda- mental research in heterogeneous catalysis. TABLE 5-1 Distribution of Grants in the Heterogeneous Catalysis Portfolio by Subarea Traditional Hetero- Surface Nano- Other, geneous Science science CSI Theory HFI 1999–2001 28 22 13 --- 3 16 13(24a) 2002–2004 26 19 20 6 4 13(23a) 2005–2007 22 21 14 17 16 (14 HFI) a Number of participating institutions.

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59 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO Traditional Heterogeneous Within this subarea, a variety of projects are addressing the fundamen- tal questions in heterogeneous catalysis related to the nature of active sites and structure–activity relationships. The projects can be characterized according to the class of materials being studied, such as metals supported on one or two metal oxides, metal oxides with various promoters, and specific zeolitic materi- als; and the type of reaction being studied, such as methanol synthesis, olefin oxidation, and so on. These projects are tackling problems of immediate interest to industry because they typically are looking at advanced systems of present catalysts, such as automotive catalysts; or at new catalysts for important (large) processes, such as methanol synthesis. Traditional heterogeneous projects have often evolved over several grant cycles, and the evolution has tended toward more sophisticated characterization techniques (including density functional theory calculations) and a considerably deeper understanding of specific reac- tions using a particular catalyst. In many cases, this deeper insight has opened the possibility of suggesting new, more active catalysts. Analysis of the Traditional Heterogeneous Subarea. This subarea has provided a long-term stable funding basis for a number of U.S. researchers that are the dominant figures in the field. Some were principal investigators in the traditional heterogeneous catalysis subarea throughout the period studied. This group in- cludes A. Bell, J. Dumesic, B. Gates, R. Gorte, G. Haller, H. Kung, S. Suib, and I. Wachs (see Appendix Table F-1). A clear strength of the program is that it has provided a stable funding environment for leading researchers in the field. The disadvantage is that the program has at times been perceived as fostering a rela- tively closed community by providing too few opportunities to new researchers. That perception was aggravated by earlier funding practices in the Catalysis Science Program and by the economic situation in the 1980s. Only 17 new awards were granted to heterogeneous catalysis research- ers during the nine years following 1987. The lack of funding for new research- ers through the program coincided with a drop in hiring beginning in 1986 in the petroleum industry, a major employer of catalysis scientists at that time. The lack of opportunity in heterogeneous catalysis research seems to have had a last- ing effect on the community, particularly considering the lag time involved in training new Ph.D. researchers. More recently, significant efforts to improve the balance between new and established researchers have been successful. How- ever, because of the opportunity gap that existed during the mid 1980s to late 1990s, a “generation gap” in heterogeneous catalysis researchers still remains. Impacts on Fundamental Science and Contributions to Energy Goals. Examples of funded research in this subject can be found in the 2007 Catalysis Science

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60 CATALYSIS FOR ENERGY Program contractor meeting summary.2 They include the work of B. Gates on providing models for understanding heterogeneous catalysis mechanisms, the work of E. Iglesia on the design of single-site catalysts for oxidation reactions, studies by R. Gorte on cerium-based catalysts for automotive catalyst applica- tions, and the work of A. Bell on methanol catalysis and metal oxides (Cu/ZrO2). There is an important class of projects that are exploring new synthesis methods, unique reactor systems, unique characterization techniques, or a new set of reactions. Examples include the work of L. Schmidt, who has done pio- neering work on short-residence-time reactors; the work of R. J. Davis, who has studied basic and acidic properties of catalysts by using various probes and spec- troscopic methods and by using theory to enhance the work;3 and the work of J. A. Dumesic on liquid-phase reforming of biomass for energy purposes (Box 5- 1). The latter work illustrates how the Catalysis Science Program can support research leading to completely new catalytic chemistry and a series of new cata- lysts. Surface Science Over the past four decades, the field of surface science—including re- action, spectroscopic, and imaging studies of single crystals and other model surfaces—has brought the description of reaction mechanisms, intermediates, and active sites in heterogeneous catalysis from schematic depictions to observ- able structures. It has contributed substantially to the science of heterogeneous catalysis and in recent years has provided much of the critical experimental da- tabase with which to benchmark electronic structure calculations. The award of the 2007 Nobel prize in chemistry to Gerhard Ertl of Germany recognized the impact of surface science on the understanding, design, and control of catalytic processes. 2 Basic Energy Sciences. 2007. Frontiers in Interfacial and Nano Catalysis. U. S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/BES/chm/Publications/Contractors%20Meetings/2007_Catalysis.pdf. Ac- cessed January 13, 2009. 3 Siporin, S. E., B. C. McClaine, and R. J. Davis., 2003. Adsorption of N2 and CO2 on zeolite X exchanged with potassium, barium or lanthanum. Langmuir 19:4707-4713; and Li, J., J. Tai, and R. J. Davis. 2006. Hydrocarbon Oxidation and Aldol Condensation Over Basic Zeolite Catalysts. Ca- talysis Today 116:226-233.

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61 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO Box 5-1 Traditional Heterogeneous Catalysis Contribution to Energy Goals The conversion of biomass for energy purposes has opened up a field of research that may have a substantial impact on the advancement of science and on progress toward meeting the nation’s energy goals. In 2002, J. A. Dumesic and colleagues discovered that aqueous solutions of oxygenated hydrocarbons with a C:O stoichiometry of 1:1 could be converted with high yields over platinum-based catalysts at temperatures near 520 K to gas mix- tures of hydrogen and carbon dioxide containing low concentrations of carbon 1 monoxide (such as 50 ppm). That discovery was inspired by initial work in the Dumesic group dealing with the selectivity for cleavage of C-O versus C-C bonds in oxygenated hydrocarbon intermediates on platinum surfaces. The Dumesic group continued its work in aqueous-phase reforming to target the 2 conversion of sugars and polyols to alkanes. Specifically, it targeted the selec- tive cleavage of C-O bonds versus C-C bonds. The conversion of a sugar or polyol to an alkane having the same number of carbon atoms as the original reactant was a major advance in the conversion of biomass resources to liquid transportation fuels. Ensuing investigations explored various routes for achiev- ing C-C coupling reactions between biomass-derived intermediates before the final removal of all remaining hydroxyl groups to form longer-chain liquid al- kanes by dehydration combined with hydrogenation. In more recent work, Du- mesic’s group has designed new catalysts (inspired by results of density- function theory calculations in the literature) to carry out the conversion of glyc- erol to synthesis gas at temperatures near 540 K. In particular, high reaction rates have been achieved at low temperatures and at pressures near 20 atm 3 with new Pt–Ru and Pt–Re bimetallic alloys. 1 Cortright, R. D., R. R. Davda, J. A. Dumesic. 2002. Hydrogen from Ca- talysis Reforming of Biomass-Derived Hydrocarbons in Liquid Water. Nature 418:964-967. 2 Huber, G. W., R. D. Cortright, J. A. Dumesic, 2004. Renewable Alkanes by Aqueous Phase Reforming of Biomass-Derived Oxygenates. Angew. Chem. Int. Ed. 43:1549-1551. 3 Soares, R. R., D. A. Simonetti, J. A. Dumesic. 2006. Glycerol as a Source for Fuels and Chemical by Low-Temperature Catalytic Processing. Angew. Chem. Int. Ed. 45:3982-3985. Recently, Dumesic and his potential impact on the biorefinery concept were noted in a Science profile,4 and his work was featured in Green Chemistry (Fig- ure 5-1). The University of Wisconsin has obtained several patents based on the group’s research. 4 Cho, A. 2007. Profile: James Dumesic: Catalyzing the Emergence of a Practical Biorefinery. Science 315:795.

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62 CATALYSIS FOR ENERGY FIGURE 5-1 Integrated process to produce liquid fuels directly from glycerol. Liquid fuels can be produced in single reactor by coupling low-temperature conversion of glycerol to synthesis gas with formation of liquid alkanes by Fischer–Tropsch synthesis. SOURCE: Simonetti, D. A., J. Rass-Hansen, E. L. Kunkes, R.R. Soares, and J.A. Dumesic. 2007. Coupling of glycerol processing with Fischer–Tropsch syn- thesis for production of liquid fuels. Green Chemistry 9:1073-1083. Analysis of the Surface Science Subarea. Since its inception, the Catalysis Sci- ence Program has supported U.S. leaders in this field, such as G. Somorjai, R. Madix, and W. H. Weinberg (see Appendix Table F-1). It has also supported the growth of the field through a second generation of principal investigators (such as M. Barteau, C. Campbell, C. Friend, and W. Goodman), many of whom were graduate and postdoctoral students of the science’s pioneers. Collectively, the principal investigators of the surface science portion of the portfolio have gar- nered an impressive number of international prizes, National Academies mem- berships, and awards from the American Chemical Society, the American Insti- tute of Chemical Engineers, and various catalysis societies. However, the mix of principal investigators in the surface science subarea appears to be fairly static and aging; for example, there has been a decrease in the number of those who received their Ph.D.’s 11–20 years before receiving program funding (Table 5- 2). As a result, the “generation gap” in the field of catalysis and in the Catalysis Science Program portfolio noted elsewhere in this report is more of a demo- graphic “cliff” in the surface science subarea. However, the reality is encourag- ing: although there has been some erosion of U.S. competitiveness in surface

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63 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO TABLE 5-2 Distribution of Surface Science Principal Investigators in the Catalysis Science Program Portfolio by Years Since Receipt of Ph.D. Frequency Distribution Years since Ph.D. 1999 2001 2003 2005 2007 ≤ 10 2 0 1 1 1 11–20 10 9 5 5 5 21–30 3 5 8 8 6 31–40 4 4 3 2 1 ≥ 41 0 2 2 4 3 Total 19 20 19 20 16 science relative to Europe and Asia, there has also been a healthy evolution of the field that is well represented in the Catalysis Science Program portfolio, even if not in the static classification of surface science programs within the portfolio. The percentage of projects classified as primarily surface science in the program portfolio has remained fairly constant over the past decade, but a proper assessment of the field must account for other programs in BES that con- tain substantial support for surface science. For example, the Condensed Phase and Interfacial Molecular Science Program, the Materials Chemistry Program, and the Solar Photochemistry Program have important surface science compo- nents. Collectively, these three programs support nearly the same number of projects that could be classified as surface science aimed at catalysis as are sup- ported by the Catalysis Science Program. Furthermore, the number of subfields encompassed by the program has increased, in part due to the strong pull of new and important applications of surface science research. A substantial percentage of the nanoscience projects in the program’s portfolio can be credited to princi- pal investigators in surface science and their students. An aspect of these two developments is an apparent generation gap in the United States that may in- clude much of the broader field of catalysis science. For example, the work of C. Campbell (see Appendix Table F-1), the current editor of the journal Surface Science, is now considered to be part of the nanoscience portfolio. The same is true of theory: a substantial portion of the growth in the theory portfolio, especially in projects that incorporate both ex- periments and theory, has spun out of surface science groups—both past princi- pal investigators and their students. Thus, looking at a broader portfolio of pro- jects that might be labeled “model systems” and seen as encompassing surface science and nanoscience, including dynamics and theory, we can see an evolu- tion of the research programs and a refreshing of the principal investigator pool with younger researchers. There are programs that integrate surface science,

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64 CATALYSIS FOR ENERGY theory, nanoscience, and catalysis in the CSI portfolio. For example, all of the current CSI projects have a substantial computation and theory component, and approximately one-half have a surface science component. Impact on Fundamental Science. As noted above, research and re- searchers funded by the surface science portion of the portfolio have contributed to the growth of nanoscience and theory. Historically much of heterogeneous catalysis and the research supporting it have been at the nanoscale. However, the increased and broader focus on nanoscience at the national level has changed the “center of gravity” in surface science. During the most recent three-year time period, approximately one-half of the projects focused primarily on surface reac- tion mechanisms, and the other half focused more on surface structure. That leaves perhaps fewer than 10 groups in the country addressing surface reac- tion mechanisms as part of the surface science portfolio, and all of the principal investigators are established full professors. One consequence is that U.S. con- tributions to Surface Science typically make up 10–20 percent of the content per issue, and fewer still are related to studies of reaction mechanisms relevant to catalysis. Contributions to Meeting Energy Goals. During the past decade, the principal investigators in the surface science subarea have made numerous contributions to the mechanistic and structural understanding of catalytic reactions that con- tinue to advance catalysis of reactions and processes with energy implications. The work has provided the crucial foundation for the grand challenge, “Under- standing Mechanisms and Dynamics of Catalyzed Transformations,” that was articulated in the recent workshop report, Basic Research Needs in Catalysis for Energy. Examples of areas of impact include the topics listed below with the names of the Catalysis Science Program principal investigators provided in pa- rentheses5. • Hydrogenation and dehydrogenation (P. Stair, B. Koel, J. Vohs, and F. Zaera) • Hydrocarbon reforming (G. Somorjai) • Oxygenate reforming (J. Chen) • Selective oxidation (M. Barteau, C. Friend, and W. Tysoe) • Heteroatom removal (C. Friend, F. Ribeiro, G. Somorjai, and J. Vohs) • Surface photochemistry and catalysis (U. Diebold, P. Stair, J. Yates) 5 Basic Energy Sciences. 2004. Frontiers in Catalysis. U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/BES/chm/Publications/Contractors%20Meetings/CatalysisContrMtg2004/Ab stractBook/StartHere.htm. Accessed January 13, 2008.

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65 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO • Structure and dynamics of catalyst surfaces (E. Altman, C. Camp- bell, C. Friend, T. Madey, R. Madix, J. Vohs, J. Weaver, J. M. White) • Bimetallic and alloy systems (J. Chen, W. Goodman, B. Koel, J. Vohs) Nanoscience The National Nanotechnology Initiative (NNI) began funding catalysis research in 2001. At that time, BES identified two types of catalysis-related nanoscience: one type funded by the NNI and another type funded by BES gen- eral funds but identified as focusing on nanoscience, both of which will be ad- dressed in this section. Analysis of the Nanoscience Subarea. The NNI brought additional funding to the Catalysis Science Program: 10 awards were given—3 to national laboratories and 7 to universities. The principal investigators chosen to receive the additional NNI funding in FY 2001 included well-established catalysis researchers (G. Somorjai, J. M. White, and C. Nickolls), but 3 awards were given to newly ap- pointed professors (see Appendix Table F-1). Of the 10 projects funded in FY 2001, 7 were still being funded in FY 2007, in keeping with the BES trend of providing long-term funding. In FY 2002, 14 awards were given: 9 were con- tinuations to the principal investigators funded by the NNI in FY 2001 (1 of the national laboratory proposals was not refunded), and 5 were new. Of the 5 new projects in FY 2002, 4 were to established researchers, but only 2 of them re- mained funded in FY 2007. Overall, the influx of NNI funding into the Catalysis Science Program led to funding of four new professors in nanoscience, or ap- proximately one-fourth of the new funding. The Catalysis Science Program funds nanoscience work that is directly related to catalysis and to work that is more fundamental. Although the funda- mental work, such as the metal-organic framework synthesis, may be high risk, it is necessary and valuable if the next breakthrough materials—such as the next “zeolites”—for catalysis are to be discovered. Impacts on Fundamental Science. Most of the NNI projects focus on synthesis of novel single-site heterogeneous catalysis, nanoparticles as catalysts, or new materials that might lead to a new family of catalysts. New materials are ex- plored through novel synthesis schemes that are used to make porous solids for use as catalysts or by reacting catalytic species with potential catalyst supports. A good example of such work is that of A. Maverick and colleagues (Figure 5- 2), who are constructing porous inorganic–organic hybrid molecules that serve as a framework for solids that contain coordinately unsaturated metal centers. Although the materials are not constructed specifically to be catalysts, they illus-

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78 CATALYSIS FOR ENERGY PMe3 Me2Si Sc H N Me3C Figure 1 FIGURE 5-6 New class of mono-cyclopentadienyl silylamido complexes of scandium, developed by J. Bercaw and colleagues. SOURCE: Shapiro, P. J., E. Bunel, W. P. Schaefer, et al. 1990. Scandium Com- plex [{(.eta.5-C5Me4)Me2Si(.eta.1-NCMe3)}(PMe3)ScH]2: a Unique Example of a Single-component .alpha.-Olefin Polymerization Catalyst. Organometallics 9:867-869. The power of breakthroughs in homogeneous catalysis can be seen in the new EPDM polymerization processes, which are so much more efficient, use so much less energy, and require so much less capital than prior technology that much of the world production of this important elastomer uses the new proc- esses.19 This important technologic achievement would have been hindered without the support of DOE funding. It can be argued that new advances in science follow on the heels of new physical techniques. One way that the portfolio will contribute to meeting long-term national energy goals is through the discovery of cutting-edge analytic techniques for the study of catalytic mechanisms. C. Landis20 has used funding from BES to develop new analytic techniques for monitoring homogeneous ca- talysis as substrates are turned into products and elucidating the mechanisms of organometallic reactions. To quote from Landis’ abstract, “two general prob- lems in catalysis that are particularly relevant . . . are (1) how much of the cata- lyst is active and (2) what are the rate laws for very fast processes?” The project shows how the portfolio will contribute to the advancement of fundamental sci- Knight, G. W.; Stevens, J. C.; Chum, P.-W. S. (Dow Chem. Co.) U.S. Patent 5,272,236, 1993 (Dow Chem. Co.). 19 Chum, P. S., W. J. Kruper, M. J. Guest. 2000. Materials Properties Derived from INSITE Metallocene Catalysts. Adv. Mater. 12:1759-1767. 20 Basice Energy Sciences. 2006. Frontiers in Organometallic, Inorganic, and Bioinspired Chemistry & Catalysis. U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2006_Catalysis.pdf. Ac- cessed January 12, 2009.

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79 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO ence in energy-related catalysis. We mention it also to illustrate the cross- fertilization that is possible among the researchers who are funded by the pro- gram and who meet each other in the contractor meetings. Landis and colleagues are developing two methods, stopped-flow nu- clear magnetic resonance and quenched-flow mass spectrometry, that may revo- lutionize the ability of future scientists to study homogeneous catalysts as they are converting reactants to products. Critical features of the methods include the potential to distinguish active from inactive catalysts on millisecond time scales and the potential for automated, high-throughput operation.“In principle, each method is capable of determining complete kinetic profiles very efficiently: in principle, it may be feasible to collect all the data needed to determine the rate laws of initiation, propagation, and termination for an industrially relevant cata- lyst in 15 min.” Contributions to Meeting Energy Goals. Research in single-site catalysis has contributed to our national goal of using less energy to produce the materials we need for our lives. And while the Catalysis Science Program has been support- ing the discovery of important new classes of catalysts, it also has been support- ing (see abstracts in the 2006 contractor meeting book21) detailed mechanistic investigations of centrally important initiation, propagation, and termination processes (J. Bercaw, R. Jordan, T. Marks, and R. Schrock); the nature of cata- lyst–cocatalyst interactions (T. Marks); the nature of surface-supported species (T. Marks); and techniques for determining the rate laws for very fast polymeri- zation processes (C. Landis). With a view to gaining ever more control over polymer properties, tandem catalysts have been studied and developed (G. Ba- zan), and more recently studies of single-site polymerization catalysis have been extended to other industrially important polymers, such as polylactide and poly- carbonates (G. Coates and M. Chisholm), including the development of a car- bonylation route to lactone monomers (G. Coates). Fundamental science that will continue to help us to reach our long- term energy goals has been developed. Ancillary benefits include avoiding the use of plasticizers, which are of increasing concern for potential environmental and long-term health effects. The program has undoubtedly made and will con- tinue to make major contributions to the development of single-site polymeriza- tion catalysis. 21 Basic Energy Sciences. 2006. Frontiers in Organometallic, Inorganic, and Bioinspired Chemistry & Catalysis. U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2006_Catalysis.pdf. Ac- cessed January 12, 2009.

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80 CATALYSIS FOR ENERGY C-H Activation The Catalysis Science Program has a long history of funding projects in C-H bond activation and may rightly claim that it has made major contributions to successes in fundamental research.22 The largest number of individual pro- jects funded by the program are in C-H and C-X bond activation (see Table 3-2). The original “Holy Grail” in C-H activation, as expressed in the 1980s when this research began to flourish, was the conversion of methane gas into methanol, which was desirable as a liquid fuel for ease of transportation. The productive functionalization of unactivated C-H bonds was first reported in Russia by A. E. Shilov in the 1960s as a noncatalytic process that was stoichiometric in expensive platinum reagents. At that time, observations of the elementary step of metal insertion into an aliphatic C-H bond, presumably the most difficult step, were few. In the ensuing decades, there were numerous demonstrations of C-H addition processes using redox active metals—primarily Ir(I), Ru(II), and Pt(II)—and mechanistic studies in selectivity of these metals toward hydrocarbon substrates. Analysis of the C-H Activation Subarea. Despite much effort to date, for the portfolio to be effective in meeting national energy goals with respect to C-H activation, there must be further functionalization of the derived metal alkyl or metal aryl via known organometallic pathways in a catalytic manner. Neverthe- less, it must be emphasized that 20 years ago chemists could not design catalysts to do what they now do routinely, that is, “crack” the unactivated C-H bond of simple hydrocarbons or even understand many of the principles that control se- lectivity of the process. Consistent with progress in the first stage of tapping into the reactivity of the “nonfunctional” C-H group is the large investment that has been made by the Catalysis Science Program portfolio, in which 34 of 140 pro- jects (24 percent) are identified by the program directors in the 2007 projects as involving C-H activation (see Table 3-2). The need for catalytic modification of the C-H group for fuel or for chemical-feedstock development will continue to be of interest and to challenge scientists and engineers. Until now, the program has focused its support on stud- ies of the critical first step in C-H activation; however, there is a need to focus future research on the completion of important catalytic cycles to have an influ- ence on energy problems of the future. The field continues to have great prom- ise, but new approaches and new insights are needed to advance beyond single- metal activation of the C-H bond. The background for such studies should in- clude related biological processes. As stated by Tobin Marks during his presen- tation to the committee (see Appendix C), we should “learn from Nature, then 22 For a review of the history of C-H bond activation discoveries see: Goldman, A.S., and K. I. Goldberg. Organometallic C–H Bond Activation: An Introduction. In Activation and Functionaliza- tion of C-H Bonds ; Goldberg, K. I.; Goldman, A. S., Eds.; ACS Symposium Series 885; American Chemical Society: Washington, DC, 2004, pp 1-43.

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81 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO go beyond.” Although many projects are described as “bioinspired,” few pro- jects in the portfolio carefully analyze the mechanistic implications of enzyme active sites and the requirements met by the surrounding protein matrix (see the section on Biorelated Projects below). In contrast, there are examples of bioin- spired approaches in the portfolio, including the subject of C-H activation. One of them is described below. Contributions to Fundamental Science. A collaborative effort researching nano- vessels between R. G. Bergman and K. Raymond, of the University of Califor- nia, Berkeley, is funded by the Catalysis Science Program. Bergman’s involve- ment began 25 years ago, when initial studies of a photochemically produced Cp*Ir(PMe3) moiety led to reliable oxidative addition of C-H bonds from ali- phatic and aromatic compounds. The extensive mechanistic work that he and his colleagues have carried out over the years has allowed the current project of Bergman and Raymond to develop (Figure 5-7). FIGURE 5-7 Top, “nanovessel” is composed of Raymond’s supramolecular structure based on coordination of gallium by rigid binucleating dicatecholate ligand, which forms edges of tetrahedron. Bottom, cavity of water-soluble clus- ter is suitable for encapsulating Bergman’s iridium complex, which further ac- cepts substrate for reaction shown. SOURCE: Raymond, K. N., and R. G. Bergman. Selective Organic and Or- ganometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems. In Frontiers in Molecular Catalysis Science, U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2008_Ca talysis.pdf. Accessed January 13, 2009.

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82 CATALYSIS FOR ENERGY Nanovessels are valuable because they provide high catalyst stability and selective substrate access. These nanoscale molecular “reactors” are com- posed of ligands that make the exterior hydrophilic, and leave the interior hy- drophobic. This research can have major implications for the design of future semi-immobilized and site-isolated catalysts in other realms of homogeneous catalysis. Mechanistic studies are the foundation of hypotheses whose testing re- quires new synthetic approaches. The extensive program of established Catalysis Science Program investigator W. Jones of the University of Rochester, demon- strates the necessity of these efforts, and the buildup of information regarding the interplay of catalyst structure and function has led to new results regarding selective processes in C-X functionalized hydrocarbons. Other grantees have developed the processes further for functionalization of the hydrocarbon. As shown in the most recent contractor meeting abstracts, approximately 12 of the reports by grantees addressed functionalization. Figure 5-8 shows some of the functionalization reactions. Catalysis Science Program researcher M. Gagné has approached selec- tive activation of C-X (X = O, Br, Cl) bonds in carbohydrates for conversion to new value-added products based on an abundant feedstock that is a renewable resource. His program also develops catalysts from a suitably ligated base metal (Ni) rather than from expensive noble metals. FIGURE 5-8 Activation of several chloroalkanes, in which it was observed that there is 100 percent preference for C-H activation of terminal methyl group over C-Cl bond. SOURCE: Jones, W. 2008. Transition Metal Activation and Functionalization of Carbon-Hydrogen Bonds. In Frontiers in Molecular Catalysis Science. U.S. Department of Energy and Oak Ridge Associated Universities. Online. Avail- able at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2008_Ca talysis.pdf. Accessed January 13, 2009.

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83 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO Principal investigator A. Goldman is showing leadership in several as- pects of C-H activation, including dehydrogenation catalysis in tandem with alkylation (Figure 5-9). Such coupling of catalytic processes represents an im- portant evolution from emphasis on C-H activation to hydrocarbon functionali- zation. FIGURE 5-9 Tandem-catalyst system in which dehydrogenated products are subject to secondary reactions, such as addition of arenes (to yield alkylarenes) or cyclizations (to yield aromatics from linear alkanes). SOURCE: Goldman, A. 2008. Transition Metal Activation and Functionaliza- tion of Carbon-Hydrogen Bonds. In Frontiers in Molecular Catalysis Science. U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2008_Ca talysis.pdf. Accessed January 13, 2009. FIGURE 5-10 Proposed cycle of Ru(II)-catalyzed hydroarylation of olefins. SOURCE: Gunnoe, T. B. 2008. Transition Metal Catalyzed Hydroarylation of Multiple Bonds: Exploration of Second Generation Ruthenium Catalysts and Extension to Copper Systems. In Frontiers in Molecular Catalysis Science, U.S. Department of Energy and Oak Ridge Associated Universities. Online. Avail- able at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2008_Ca talysis.pdf. Accessed January 13, 2009.

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84 CATALYSIS FOR ENERGY Another young investigator, B. Gunnoe, is addressing alkane function- alization by addition of C-H bonds across C-C multiple bonds (Figure 5-10). Both the C-H activation and the C-C coupling reactions appear to occur at a single ruthenium as a catalytic center. Other catalysts, in particular planar complexes, have been shown to be promising for directing C-Cl versus C-H activation by yet another young inves- tigator, O. Ozerov. Contributions to Meeting Energy Goals. Ultimately, the goal of C-H activation catalysis is to find catalysts that would incorporate C-H activation into hydro- carbon-conversion technology, which would lead to functionalized compounds needed for feedstocks in the chemical industry or the ability to convert methane into useful liquid transportation fuels. Although the mechanistic studies of C-H activation processes that have established selectivity certainly encourage the development of possible applications, simple functionalization of hydrocarbons after C-H activation has not been realized. New ideas are needed; designs based on alkyl-group transfer to a second metal or on bifunctional ligands are possi- bilities. The potential for C-H activation (and all other subfields of homogene- ous catalysis) to affect future energy issues could be increased by integrating computational chemists more deeply into major synthetic and mechanistic stud- ies. A fundamental issue in catalyst design and mechanistic understanding must be addressed by computational chemistry. There appears to be a deficiency of computational projects that address homogeneous catalysis in the Catalysis Sci- ence Program portfolio. Homogeneous Catalysis in Organic Synthesis Homogeneous catalysis is widely used in the synthesis of fine chemi- cal, agricultural, and pharmaceutical intermediates and was identified by the survey of industry representatives (see Appendix D) as one of the most impor- tant fields of catalysis. It is a broad field, encompassing metal-based reagents for asymmetric and other transformations and metal-free organocatalyst systems. The discovery, development, and applications of metal-based catalytic reagents in organic synthesis have been recognized twice during the past decade: in 2001 by the award of a Nobel prize for chiral hydrogenation and oxidation catalysts and then in 2005 by the award of a Nobel prize for the olefin metathesis reac- tion. Analysis of Homogeneous Catalysis in Organic Synthesis. Analysis of the port- folio shows only a few, but nevertheless important, grants in this area. For example, the high inherent selectivity of homogeneous catalysts al- lows the production of molecules of desired handedness or enantioselectivity

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85 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO (asymmetric catalysis), which is critical for synthesis of fine chemicals, pharma- ceuticals, agricultural chemicals, and electronic material. An analysis of the portfolio reveals a small number of projects that in- volve the study and development of homogeneous palladium catalytic processes. Two projects in the portfolio deal with subjects of great interest. In the first, J. Hartwig uses palladium catalysis for hydroamination of olefins and addresses a key type of structural change. Wedding the strength of homogeneous catalysis to design a specific complex to affect a particular transformation with the strength of heterogeneous catalysts to facilitate separation of the metal complex from the reactants and products instills the need to “heterogenize” homogeneous cata- lysts. The other project, that of C. Jones, is a noteworthy effort to deal with that challenge. Contributions to Fundamental Science. Asymmetric catalysis is of less impor- tance for fuel production, but it is critical for production of fine chemicals, pharmaceuticals, agricultural chemicals, and electronics (for example, for liquid- crystalline displays). Conventional methods for separating enantiomers are slow and energy intensive. Asymmetric catalysts allow the production of selected enantiomers in high yields with increasingly efficient resource usage, energy efficiency, and waste reduction. Given the historical and continuing importance of this field to the chemical industry and the fact that many of the organometallic and homogene- ous catalysis programs funded by the Catalysis Science Program involve new ligand development, there seems to be a lack of programs directed specifically at asymmetric catalysis. Nevertheless, the number of these grants in the program portfolio is at an appropriate level considering that asymmetric catalysis re- search is for the most part well funded by other agencies. Contributions to Meeting Energy Goals. The Catalysis Science Program funds very few grants dealing with the use of transition-metal catalysis with respect to synthetic organic chemistry, which has potential industrial and energy-related ramifications. For example, the catalytic properties of palladium could make it possible to functionalize simple hydrocarbon-based feedstocks to more complex molecules or to defunctionalize biobased feedstocks to target molecules for im- portant applications. Homogeneous Catalysis in Biorelated Projects Enzymes are naturally occurring catalysts that are responsible for trans- forming biological molecules and materials into the myriad forms found in na- ture. Moreover, biological catalysts in energy-yielding and energy-requiring processes are linked to bioenergetics in ways that hold promise for meeting the energy needs of human economies.

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86 CATALYSIS FOR ENERGY An example is the cathodic reduction of oxygen to water—the key re- action of fuel cells. Engineered catalysts for fuel cells use noble metals, such as platinum. From a thermodynamic perspective, these are not efficient (and they are not naturally abundant). This has limited the use of fuel cells as power sources for transportation. Living cells have a version of the fuel cell, mitochon- dria, in which the cathodic reaction is the same as in engineered fuel cells: the reduction of oxygen to water to provide energy. Nature’s catalysts for hydrogen oxidation (and for proton reduction to hydrogen) are typically nickel and iron or iron alone. Nature’s catalysts smoothly oxidize methanol, ethanol, carbohy- drates, and fats to carbon dioxide, collecting all of the electrons for use in the mitochondrial fuel cell to reduce oxygen and yield energy. In addition to operating at ambient temperature, nature’s catalysts gen- erally direct complex chemical reactions along coordinates that yield essentially a single product, making the isolation and purification of products efficient. The protein component is a large fraction of an enzyme’s structure and is necessary for biological functions. However, the chemical processes are carried out by a much smaller number of atoms in the enzyme than the protein, and are made up of abundant elements that actually control the movements of electrons, atoms, and ions to rearrange the reactants to make products. Research in bioinspired catalysis is focused on isolating and understanding those catalytically active components of the enzymes. Analysis of Homogeneous Catalysis in Biorelated Projects. This portion of the Catalysis Science Program portfolio is difficult to assess because it is only a small component of the overall investment in catalysis. Depending on how one categorizes the funded projects, biorelated projects increased from 2 proposals during FY 1987 to FY 1997 to 10 during FY 2005 to FY 2007. The latest con- tractor meeting (May 2008) listed 14 projects that were described as bioinspired or biorelated. Despite the importance of the biorelated projects, the program does not appear to provide a useful way to bring experts in biological catalysis into con- tact with the mainstream contributors to the catalysis portfolio. One of the more “biological” of the funded investigators is D. Kern. Her work in the dynamic motion of proteins is related to catalytic turnover and signal transduction (phos- phorylation). A sampling of investigators whose primary aim is to understand metalloenzyme catalytic mechanisms is a needed component for advances in biorelated catalysis, and the lack of this opportunity for cross-fertilization is a serious concern. In contrast, many of the principal investigators who are active in bioinorganic catalysis are funded outside DOE. These principal investigators, however, may bring their insights to their DOE-funded research.

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87 ANAYLYSIS OF CATALYSIS SCIENCE PROGRAM PORTFOLIO FIGURE 5-11 Proposed mechanism of bioinspired cis-dihydroxylation of naph- thalene. SOURCE: Que, L. 2008. Bio-inspired Iron Catalysts for Hydrocarbon Oxida- tions: April 2008 report. In Frontiers in Molecular Catalysis Science, U.S. Department of Energy and Oak Ridge Associated Universities. Online. Available at http://www.sc.doe.gov/bes/chm/Publications/Contractors%20Meetings/2008_Ca talysis.pdf. Accessed January 13, 2009. Contributions to Fundamental Science. The Catalysis Science Program has funded key researchers in biorelated catalysis with some success. We applaud the consistent emphasis on oxidation catalysis. For example, in a project titled “Bioinspired Iron Catalysts for Hydrocarbon Oxidations,” L. Que and col- leagues have improved the understanding of oxygen addition reactions to or- ganic substrates (Figure 5-11). Inspired by nonheme iron oxygenases, Que and his group recently found biomimetic cis-dihydroxylation of naphthalene by us- ing a six-coordinate, octahedral iron complex designed to have cis-oriented la- bile ligands. The proposed mechanism of reaction shown below is important for all cis-dihydroxylation reactions, and the specific application is important for bioremediation. Because the selective oxidation of organic molecules is necessary for the efficient use of hydrocarbon feedstocks, it is important that this type of work be expanded. A second notable project in oxidation catalysis in the biorelated portfolio is that of the young investigator S. Stahl (see Appendix Table F-2), whose work on organometallic copper oxidase reactions is aimed at gaining fundamental understanding of copper-catalyzed aerobic oxidation reactions that proceed via organometallic intermediates. This new subject is being addressed by an up-and-coming young investigator who is moving away from expensive palladium reagents and toward the use of copper as a low-cost metal catalyst. Another young investigator funded by the program is P. Chirik of Cor- nell University, whose work is in synthetic approaches to nitrogen fixation. The need for ammonia for fertilizer and for use in feedstocks in the production of

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88 CATALYSIS FOR ENERGY nitrogen-containing organic molecules is as profound as are the energy require- ments for abiological fixation. Chirik’s metallocene complexes, which bind dinitrogen, promise new approaches to activation of this typically inert mole- cule. It is notable that the detailed mechanistic approaches of L. Que and S. Stahl may be expected to also contribute to the understanding of the reversal of the oxygenation process. Oxygen removal from carbohydrates is important for the development of biofuels. The work of J. Dumesic of the University of Wis- consin includes two main approaches to reforming of oxygenated compounds (Box 5.1): biomass gasification, followed by water-gas shift and Fischer– Tropsch reaction, and hydrogenation of biomass to produce a liquid fuel. The Catalysis Science Program staff has stated that a new emphasis on biomimetic chemistry will be announced in the near future. This will be highly appropriate given the convergence of molecular biology, biochemistry, bio- physical techniques, protein crystallography and synthetic analogues of metal- loenzyme active sites. Synthetic biology presents an opportunity for understand- ing the function of such evolutionarily perfected selective catalysts. SUMMARY On the basis of the information evaluated, the BES has done well with its investment in the Catalysis Science Program. Its investment has led to a greater understanding of the fundamental catalytic processes that underlie en- ergy applications, and it has contributed to meeting long-term national energy goals by focusing research on catalytic processes that reduce energy use or ex- plore alternative energy sources. In some areas the impact of the research has been dramatic, while in other areas important advances are yet to be made. The committee’s key findings and recommendations for the Catalysis Science Pro- gram are summarized in Chapter 6.