Opportunities for Catalysis Science in the 21st Century 

Report of WorkshopGaithersburg, Maryland

May 14 – 16, 2002

Why this subject?

"The economic contribution of catalysis is as remarkable as the phenomenon itself. Approximately one third of material gross national product in the US involves a catalytic process somewhere in the production chain (see Morbidelli, M, Gavriilidis, & Varma,A., Catalyst Design, N.Y., Cambridge Univ Press, 2001) Confining analysis to the chemical industry, the proportion of processes using catalysts is 80% and increasing. Total sales of catalysts in the US were more than $1 bn in 1996, with the catalyst market increasing at 5% per year."

Chemistry & Industry, Jan 21, 2002, page 22.

Why now?

The Academy’s Committee on Science Engineering and Public Policy in a recent report concluded that catalysis is a sub field in which the US is among the world leaders, but is broadly expected to lose its current international position because of refocusing investments in the industrial sector without of transfer of this expertise to the educational sector.

Advances in nanoscience understanding offer new approaches to establishing a firm scientific basis for advancing our understanding and ability to predict catalytic phenomena.

Basic science opportunity

Competitive position on international scene

Who participated?

National labs Industry

Academic

ForeignUSA

Ten Breakout Sessions

1. Catalysis design driven by fundamental research2. Linking basic research to applications through collaborations3. Biocatalysis4. Homogeneous catalysis5. National facilities—photons, neutrons and end stations6. Spatially resolved and atom specific microscopy and spectrosocopy7. Tuning reactivity by tailoring nanostructures8. Theory, modeling and simulation9. Dynamics and kinetics10. Synthesis of nanostructured materials for catalytic applications

Common themes emerging 1. Complexity and interdisciplinary

character of 21st century catalysis issues

An appreciation for the complexity associated with catalytic phenomena spanning, often with common features, biocatalysis, homogeneous and heterogeneous catalysis. Fundamental interdisciplinary research addressing such complexity requires the long-term organized cooperation, collaboration and funding of experts from many fields of science and engineering, and calls for using our specialized national facilities to their fullest potential.

Common themes emergring2. Advances enable tailoring, tuning and

designing nanostructured catalyst materials.

As a result of continuing advances in three arenas—experiment, computation, theory—especially those enabling tailoring, tuning and designing materials at the nanostructure level, there is a truly unique opportunity for experts from all three arenas to coherently move the field of catalysis forward by addressing core complex issues.

Recommendation – NCRI’s

National Catalysis Research Institutes (NCRIs)

• Establish two to three

• Competitively selected,

• Centered in the National Laboratories or universities as appropriate

• By charter, collaboratively networked to other national laboratories, universities, and industry.

NCRI’s

Recommendation: Basic research themes

Each NCRI would have a well-defined, long-term basic research theme, selected for its scientific importance and potential societal impact, and consist of a closely integrated group of appropriately expert collaborators to address the interdisciplinary research theme.

NCRI’s

Recommendation: Students, industry and virtual access.

To encourage and strengthen university—particularly student—involvement and increase participation of industrial users from throughout the country, each institute should include a prominent virtual component.

NCRI’s

Recommendation: NCRI support

NCRIs would receive sufficient support for amplifying, integrating, and accelerating the research of individual scientists at the institutes themselves and at institutions participating in the virtual collaboratory.

NCRI’s

NCRI’s and single investigator programs

Funding for an NCRI should not diminish the already very tight funding for productive single investigator programs; rather, an NCRI should involve newly available resources that serve to amplify these efforts.

Recommendation: Linkage to national facilities

Wherever possible and appropriate, institutes should include or be closely aligned with special research facilities including state-of-the-art microscopes, light sources, neutron sources, terascale computers, and/or nanoscience institutes in order to capitalize on their unique capabilities.

NCRI’s

Why this NCRI mode?National Catalysis Research Institute(s)

Addressing complex problem involves a focused, coherent, multidisciplinary, long-term attack that preserves flexibility for individual investigators and gains the best features of collaboration on a common problem.

Subdivisions and common concepts

Homogeneous Biological

Heterogeneous

Common Concepts

The electrons do it!

Structure and dynamics -- both important.

Sites are central but so are more subtle features.

Efficiency, effectiveness, robustness always important.

Experiment, simulation/computation, theory

Experiments Theory

Simulation/ Computation

Linkages

Size and time scale that can be handled:

Calculations: larger and longer with high accuracy.

Experiment: smaller and shorter.

Calculations and experiment: Potential to meet at nanoscale lengths and sub-picosecond times.

Catalyst Efficiency, Effectiveness, Robustness

Turnover Number Selectivity

Lifetime

Typically, faster is better – often there is a selectivity penalty.

Integrated over time, “minor” side reactions become a “major” problem.

OPPORTUNITY: Tune heterogeneous catalysts using nanoscience methods to realize the selectivity of biocatalysts and the single site

characteristics of homogeneous catalysts without overly compromising the turnover number and the catalyst lifetime.

Nanoscience and catalysis In much of heterogeneous catalysis, nanoscale particles are key.

Nanoscale particles are unique – neither bulk nor atomic properties.

Common goals of catalysis and nanoscience include:

understanding and predicting the properties of materials at the nanoscale and how they facilitate chemical reactivity.

building/manufacturing nanoscale components from the bottom up.

integrating nanoscale components into macroscopic scale objects and catalysts for real-world uses.

Key points from each of the ten sessions

Linking basic research to applications through collaborations

A number of foreign governments have either begun or continued to pursue catalysis as a matter of policy linked to their economic development.

Addressing many grand challenges for catalysis in the age of nanoscience requires new funding for coherently managed focused experimental and theoretical basic research goals.

Breakthoughs, rather than incremental improvements, are needed in many of these complex systems areas — breakthroughs that NCRI(s) can facilitate in a basic research environment that brings together and maintains long-term support for capable, productive and collaborative individuals.

Catalysis design driven by fundamental research toward use-inspired targets

Central goals for new catalysts—high turnover number at low temperatures, nearly 100% selectivity, and stability with respect to sintering and fouling.

Relevant intermediate term targets include: selective oxidation, alkane activation, byproduct and waste minimization, stereoselective synthesis, functional olefin polymerization, alkylation, living polymerization, and alternative feedstocks and renewables.

Relevant longer term targets include: photocatalytic water splitting, low cost oxidants, NOx decomposition, methane conversion to useful products, clean transportation fuels, low cost fuel cells and replacement of Pt-group metals.

Theory, including computation and simulation

The ultimate goal of theory is to develop ways to reliably predict new reactions and catalysts and, thus, guide rational design of novel materials and processes.

Powerful theoretical tools exist that are emerging as key ingredients of modern catalysis research.

Theoretical work should put structure and dynamics on an equal footing; in catalysis, both are critical. Theory, experiment and computation should be coherently linked

Organizationally, the contributions of theory to 21st century advances in catalysis can be fostered in several ways, such as programmatically combining experimental and theoretical efforts.

Homogeneous catalysts

Potentially highly selective, in part because the catalysts are well-defined molecules, i.e., single sites, with highly tunable structural and dynamical characteristics.

Emerging ability to tailor and control solid structure at the nanoscale combined with ability to control molecular structure brings the exciting possibility of building novel catalytic materials that combine the best features of homogeneous and heterogeneous catalysts — “nanocatalysts.”

Biocatalysis Biocatalytic conversion of renewable feedstocks derived

from cellulose, hemicellulose, starch and plant oils into desirable products, including transportation fuels, is an important economic target needing long term interdisciplinary basic research..

Goals do not differ from those involved in homogeneous and heterogeneous catalysis of petroleum feedstocks; efficiency and selectivity are central.

One particularly interesting new nanoscale capability applicable to biocatalysis is measurement, for single molecules, of optical spectra and mechanical properties.

Development, deployment, and application of high-throughput analytical techniques in an NCRI would be an enormous help

Synthesis of Nanostructured Materials

for Catalytic Applications Advances in synthetic methodology, coupled with advances

in temporally and spatially resolved characterization, provide a unique opportunity to construct nanostructured solid catalysts designed for high turnover numbers, superb selectivity, and minimal waste.

Sufficient complexity must be incorporated in the nanostructured material to block undesirable paths and keep open a low-energy catalyzed path to the target product.

The potential exists to bring heterogenous and biological catalysis into this research by immobilizing enzymes and homogeneous catalysts on these tailored structures.

Tuning Reactivity by Tailoring

Nanostructures Goal: tunable catalyst design from first principles.

Interdisciplinarity: Combining nano and molecular science, synthetic chemists working with catalysis and materials scientists can develop new nanocatalysts based on numerous strategies.

A concerted effort should be made to identify defect structures in nanocatalysts and, on a single site basis, synthesize and characterize them structurally, electronically, and catalytically.

Dynamics and kinetics

Dynamics—theory and experiment—provides the molecular level basis for determining kinetic parameters—reaction rate constants and diffusion coefficients—for each step in a reaction mechanism that describes an operating catalytic process.

The dynamics of catalyzed reactions must, of necessity, involve the atomic motion and energy flow in the catalyst as well as the reactant.

Biological, homogeneous, and heterogeneous catalysis share common dynamical issues, there is a splendid opportunity to develop common ground in the area of dynamics.

Spatially resolved and atom specific microscopy and spectroscopy

• Understanding the non-uniformity of reactions in-situ is one key to unraveling the complexities.

•Transmission electron microscopy continues to advance as electron beam sources and detectors improve, theory approaches expand and in-situ environmental accessories are developed.

• Experimental characterization of nanostructured catalysts often goes hand-in-hand with theory.

National photon and neutron facilities: Beamlines outfitted for and dedicated to

catalysis research

• Concurrent, in-situ measurements of spatial, chemical, and temporal properties can be made available on one beamline.

• Amplified use would result if dedicated beam lines and end stations were built to accommodate the unique requirements of catalysis research -- ancillary instrumentation required.

• On-site expertise in catalysis.

Human resources

Academic catalysis researchers (and students being trained) are declining in numbers.

Scientific Opportunities/challenges

Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) 8404.

Interpolation in the periodic table

Jacobsen, Dahl, Clausen, Bahn, Logadottir, Nørskov, JACS 123 (2001) 8404.

Measured ammonia synthesis rates 400 C, 50 bar, H2:N2=3:1

Catalysis by Design: Molecular engineering and heterogenization of metallocene catalysts

for propylene polymerization

 

Fundamental understanding of the action of catalyst activators such as methylalumoxane (MAO) enables a variety of heterogenization options for practical metallocene catalysts  G. G. Hlatky, Chem. Rev. 2000, 100, 1205. H. Ahn, C.P. Nicholas, and T. J. Marks, Organometallics 2002, 21, 1788. S. Obrey and A.R. Barron, Macromol. 2002,35, 1499. 

FLAPW calculated chargedensity difference obtainedby substracting the superposition of the charge densities of a Au monolayerand TiO2(110) from that ofAu/TiO2(110)

Yang, Wu, Goodman, PRB (2000)

Theory: FLAPW Calculations of Au/TiO2(110)

Predicts an initial statecore level shift for Au on TiO2 to a lower binding energy of ~1.2 eV, consistent with the experimental value of 1.0 eV

Au

Ti

Molecular Beams – Bruce Kay

Neutron diffraction

Probing local valence electron density with X-rays

Probing local valence electron density with X-rays

TEM

Pt

Al

O

[001]

[110]

Simulated image for a 0.5Å probe expected after correction of microscope aberrations

Z-contrast image at 1.3Å resolution showing Pt trimers and dimers on a -alumina support

Looking deep in side -- Raman

How long does it take to melt a gold nanorod?

a

50 nm

b

50 nm

0 50 100 150 200 250

-6

-4

-2

0 obs

= 690 nm

= 34 ± 6 ps

A /

mO

D

time / ps

Status

• Well developed basic understanding – theory-experiment

• Beginning to be able to use it directly in catalyst design

• Some activity-descriptor correlations

• Host of new in situ methods for catalyst characterization

• New very powerful screening methods

• We have a starting point which is radically different from the situation 5 or 10 years ago!