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“Strategy for Fabricating Nanoscale Catalytic Circuits”

“Strategy for Fabricating Nanoscale Catalytic Circuits” Heterogeneous Kinetics and Particle Chemistry Laboratory Washington University St. Louis, Missouri. Graduate Students Undergraduate Students John Parai Joe Swisher Eugene Redekop Adam Grimm Xiaolin Zheng Yoonsung Han

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“Strategy for Fabricating Nanoscale Catalytic Circuits”

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  1. “Strategy for Fabricating Nanoscale Catalytic Circuits” Heterogeneous Kinetics and Particle Chemistry Laboratory Washington University St. Louis, Missouri Graduate StudentsUndergraduate Students John Parai Joe Swisher Eugene Redekop Adam Grimm Xiaolin Zheng Yoonsung Han Rebecca Fushimi* Zachary Wegmann Mike Rude* Amy Vukovich Ana Brjetchkova *Graduated Jeffrey Packer Faculty Gregory Yablonsky John T. Gleaves

  2. “Strategy for Fabricating Nanoscale Catalytic Circuits” Heterogeneous Kinetics and Particle Chemistry Laboratory Washington University St. Louis, Missouri Why catalysis? Why now? What’s ahead?

  3. Growing 2 systems/year Ghent Eindhoven Delft Belfast Lund Chicago Berlin Cardiffe Lyon Bochum Beijing New Jersey Saint Louis Leipzig Madrid Tokyo Barcelona Tokyo City Houston Lausanne Bangkok HKPCL - Washington University TAP Reactor System “Research World” (Temporal Analysis of Products) TAP - International Research Applications Alternative energy sources: hydrogen production, synthesis gas, biomass conversion Environmental research: autoexhaust catalysis, NOx reduction, chemically benign processing Nanoscale research: catalytic nanofactories, atomic tailoring of particle surfaces Advanced industrial processes: high selectivity conversion of alkanes to useful chemicals

  4. Atom Molecule Enzyme Simple,complex solid Catalyst Molecules Electrons Photons Regeneration Start Molecule A C A Catalytic Cycle D Reaction A B Molecule B Photons, Electrons Catalysis Primer A Few Benefits of Catalysis Life Ammonia fertilizer Clean water Nontoxic auto-exhaust Nylon Sulphuric acid 93 octane gasoline L-dopa Hefty trash bags Anti-freeze Fuel cells Plastic drain pipe Aspartame Roundup and on and on …… Catalysts give precise spatial and temporal control of chemical reactions, can operate billions of cycles, produce materials, fuels, agricultural and pharmaceutical products, and store and release energy.

  5. C1 chemistry CH4 + CO2 2CO + 2H2 CO+ H2 Specific alkanes, alkenes CO+ H2 CH3CH2OH, or higher alcohol CO+ H2O CO2 + H2 2CH4 + O2 2CH3OH Photocatalytic Reactions H20 + hn Hydrogen CO2 + H2O + hn Chemicals Some Current Challenges for Catalysis Alkane conversion Ethane CH3CHO (acetaldehyde) Ethane Aromatics Propane CH2 CHCHO (acrolein) Propane CH2 CHC N (acrylonitrile) PropaneCH2 CHCH3 (propene) PropaneCH2 CHCOOH (acrylic acid)

  6. Depletion of Oil - Current Estimates Proven reserves - 1,200,000,000,000 barrels Current rate of consumption - 80,000,000 barrels/day (DOE, 2005)

  7. Worlds Largest Oil Field Ghawar Supergiant field- discovered 1948

  8. Depletion of Oil - Forecasting the Future Discoveries greater than consumption Consumption greater than discoveries Exploratory drilling

  9. Depletion of Oil - Forecasting Future Demand Fuel Imports ($ billions) % Increase Economy 2000 2004 2000 - 2004 China 21 48 128 India 19 34 79 Japan 77 99 29 US 140 216 54 European Union 219 347 58 Projected consumption - 2010 - 91,000,000 barrels/day 2015 - 100,500,000 barrels/day 2020 - 110,300,000 barrels/day 2025 - 120,900,000 barrels/day (DOE - Energy Information Adminstration 2004)

  10. We are here Global Context in which New Technology is Developed Population growth rates are predicted to continue to drop. World population predicted to reach 9 billion by 2043. By 2050 the world population will reach 9 to 10 billion, and current reserves of both oil and natural gas will be exhausted. Where will the new people live? Where do they obtain the raw materials for life? food, water, fuel, ….

  11. US WorldLow Income GDP (US$) (billions) 11,711.8 41,365.8 1,216.0 GNI per capita (US$/yr) 41,440.0 6,338.0 507.0 Life expectancy (years) 77.4 67.3 58.8 Population, total (millions) 293.7 6363.2 2311.7 Population growth (annual %) 0.8 1.2 1.8 Surface area (sq. km) (thousands) 9,629.1 133,940.9 29,264.5 Where will the new people live? In 2043 World Population - 9,000,000,000 US Population - 400,000,000 (US Census Bureau - 2006) (World Bank Statistics - 2004)

  12. Syngas Process Solar Catalytic Reactor CH4 + H2O 3H2 + CO CO + H2 K.I. Zamaraev, Topics in Catalysis, 1996, 3,1. Alternatives to Petroleum Coal, natural gas, oil shale, biomass The transition from petroleum will involve a change to a feedstock composed of C1 or C2 molecules and hydrogen.

  13. Industrial reactors that give precise reaction control. Highly selective catalysts to perform multi-step reactions. Changing Focus of Catalysis and Reaction Engineering Petroleum based chemistry - large hydrocarbon molecules are cracked into smaller molecules. C1-C2 based chemistry - large molecules are assembled from small ones. 1. Multiple sites to perform different reaction steps. 2. Molecular and nanoscale features. 3. Complex and fragile. 4. Photocatalytic materials

  14. Metal cluster Substrate surface Ag nanocluster array on alumina 20 nm Heiz, Sherwood, Cox, Kaldor, Yates, J. Phys. Chem. 99, 1995, 8730 - B. C. Gates, Chem. Rev.95, 1995, 511 - 522 C. Henry, Surface Science Reports 31, 1998, 231 - 325 Iijima and Ichihashi, Phys. Rev. Lett. 56, 1986, 616 - 619 G. Rupprechter, A. Eppler, A. Avoyan, G. Somorjai, Studies in Surface Science and Catalysis, 130 (2000) 215 - 220 Thin film Substrate surface C. Campbell, Surface Science Reports, 27, 1997, 1 - 111 Constructing Catalytic Circuits “Active Sites on a Chip”

  15. Precise kinetic characterization RH RH ROH ROH Oxygen, Metal atoms Metal Oxide Particle Precise Submonolayer Change in Surface Composition Physical characterization Atomic Tailoring of Catalysts Particles

  16. Vacuum - O2 T> 400 °C Oxygen uptake behavior Single phase (VO)2P2O7 and (800 torr O2) O2 desorption spectrum from 18O2-treated (VO)2P2O7 T= 460°C, V(4.13) 16O2 T= 450°C, V(4.10) Oxygen uptake (x1017 O atoms) Relative ion signal T= 430°C, V(4.07) 16O18O 12.7x1018 O atoms adsorbed 18O2 time (s) m/e Oxidation of a (VO)2P2O7 at Atmospheric Pressure Trx > 400, Pox ≈ 1atm, trx ≈ 1000 s (VO)2P2O7 (VO)2P2O7 + O2 Single XRD phase Vanadium oxidation state = 4.02 Bulk Vanadium oxidation state = 4.1 VOPO4 phases may be present

  17. Ox Time 0-min. 4-min. 128-min. 32-min. 64-min. MA production versus VPO oxidation time Sel. Selectivity and Conversion Con. R-Equil. 4-min.. 32-min. 64-min. 128-min. Oxygen treatment time Affect of Oxygen Surface Concentration on Catalyst Performance Increased oxygen concentration New phase (VO)2P2O7 O2 Flow T = 480° C P = 1 atm. C4H2O3 (maleic anhydride) C4H10 C4H10 Pulse T = 380° C P = vacuum

  18. Nanoparticles Nanoscale Fabrication on Particles Atomically tailored surface composition Metal atom deposition Metal Oxide Particle Well-defined bulk lattice

  19. Chemical Vapor Deposition B.C. Gates, Chem. Rev. 95, 1995, 511 - 522. Atomic Beam Deposition Knudsen Cell Reaction Products MMO MMO + M Atomic Beam Catalyst particles Metal-enriched nanolayer Single Crystal Organometallic Compound e.g., Ir6(CO)15 Metal Atom Deposition on Metal Oxide Particles

  20. Vibrate bed Creating Nanoscale Concentration Gradients of Transition Metal Species on Bulk Metal Oxide Catalysts Transition metal source Atomic beam Laser beam Catalyst particle Sample holder (Vacuum - 10-8 torr)

  21. Atom Deposition Chamber Cu pulses .1s

  22. 2. Small pulse size - High S/N 80 .0025 5.0 5.0 time(s) TAP Pulse Response Experiment Pulse valve Reactant mixture Microreactor Catalyst Key Characteristics Pulse intensity: 10-10 moles/pulse Input pulse width: 5 x10-4 s Outlet pressure: 10-8 torr Observable: Exit flow (FA) Mass spectrometer Vacuum (10-8 torr)

  23. Experimental and Predicted Responses Argon and Butane Pulsed over VPO Experimental and Predicted Responses Argon Pulsed over Quartz Particles Transport + Irreversible Adsorption Normalized Flow Relative Flow effective diffusivity porosity Argon Butane Response after Reaction 0.5 time(s) 0.5 time(s) Experimental and Predicted Responses Butane Pulsed over Oxygen-treated VPO Arrhenius Plot Butane over Oxygen-treated VPO 1.0 Ea = 12 kcal/mol Relative Intensity ln k 280 320 0.0 360 Temp. 0.1 400 440 time (s) 1000/T

  24. Quantities calculated from 0th, 1st, and 2nd moments 10000 • Conversion (number of surface oxygen atoms and hydrocarbon) • Selectivity • Product Yield • Residence time • Apparent rate constants • Apparent intermediate gas constants • Apparent time delay 6000 5000 4000 Pulse Number 3000 2000 1000 time(s) Zeroth Moment Shekhtman, S. Interrogative Kinetics A New Methodology or Catalyst Characterization. Doctoral Thesis, Washington University, 2003. Quantitative Determination of Catalyst Surface Composition and Kinetic Characteristics

  25. Atomic Beam Deposition Laser spot Silica particles Pd/PdO deposits 10-6 torr O2 Pd atoms Sample holder TAP Experiments O2 uptake CO CO2 Atomic Beam Deposition of Pd on Silica Particles

  26. - CO2 production - Total O2 uptake at room temperature Maximum indicates structure sensitivity Kinetic Evidence of Reactive Self-assembly Amorphous Pd/PdO deposit SiO2 + CO2 CO Pd nanoclusters

  27. Example reaction: C3H8 + 2 O2 C3H4O2 + 2H2O n 2 H2C CCH2 O2- Nanoscale Catalytic Circuit “Catalytic Nanofactory” m O2 4 C3H8 n 4 O2 C3H6 C3H4O2 Insulating phase Nanoparticle H+ b+ O2 activation site Mb Surface phase Ma Sub-surface phase (controlled oxygen transfer) Bulk phase (facile electron transfer) ne-

  28. Thanks for your attention.

  29. Vacuum Transformation of Oxygen-treated (VO)2P2O7 Wavelength time (s)

  30. 100 80 80 .0025 5.0 60 Fexit (t) 5.0 time(s) 40 Insignificant change Fexit (t) t(x5) 20 Fexit (t) t 2(x10) 0.0 1.0 2.0 3.0 4.0 5.0 time (s) time 0.0 Experimental Features of TAP Pulse Response Experiment Small Pulse Size - High S/N Primary and Time-weighted Transient Response Curves (0th moment) (1st moment) (2nd moment)

  31. Activity- Structure Relationship for Complex Catalysts

  32. Catalyst Preparation Methods from “Methods for Preparation of Catalytic Materials”, C. Contescu, and A. Contescu, Chem. Rev. 1995, 95,47

  33. Key Results: Metal Atom Deposition Experiments • Demonstrated a new approach for adding metals atoms to the surface of a bulk metal oxide. • Shown that small changes in the metal atom surface concentration can influence reaction kinetics. • Changes can be detected using transient response experiments. Oxygen Titration Experiments • Catalyst selectivity changes as a function of the catalyst oxidation state. • Total amount of catalyst oxygen used: 7.7  1018 atoms 5.5 atoms O/molecule Furan 9.5 atoms O/molecule Butane 8 atoms O/molecule Butene 7.8 atoms O/molecule Butadiene • Total amount of catalyst oxygen used: 7.7  1018 atoms • Oxygen consumption = oxygen adsorbed during oxidation treatment. • Apparent Kinetic Constants Reactants • was greatest for butadiene. Products • indicated different reaction paths. • was linearly independent of oxidation degree suggesting a more complex supply mechanism.

  34. isobutanol Catalyst precursor (1) V2O5 + o-H3PO4 (100%) (reflux 16h) Air/butane (1.5% C4) Dry (1) (2) 1 bar, 673 K, t > 1000h. Air calcine Single XRD phase: (VO)2P2O7 Vanadium Ox. State: 4.01 - 4.02 Bulk Catalyst Preparation for Butane Oxidation

  35. n 2 n 4 C3H8 + 2 O2 C3H4O2 + 2H2O Catalytic Selective Oxidation-Reduction Cycle R. K. Grasselli, Surface properties and catalysis by nonmetals, 1983, 273 -288 Propane O2- O2 Propane activation site Oxygen activation site H+ Ma Mb a+ b+ Phase B Surface phase n e- Acrylic acid Selective oxidation of propane to acrylic acid

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