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Catalyst Characterization

Catalyst Characterization

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Catalyst Characterization

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  1. Catalyst Characterization

  2. Reactive gas adsorption • What can be measured using this technique? • Who would be interested in such results? • A brief overview of measurement fundamentals. • Catalysts • Instrument specific features of benefit to analyzing catalysts

  3. Reactive Gas Adsorption • What can be measured using these techniques? • Amount of reactive sites on a surface • Active metal area • Dispersion • Nanocluster/crystallite size • Heats of adsorption • Ease of reduction (TPR) • Ease of oxidation (TPO) • Bond strength (TPD) • Activation Energy

  4. Reactive Gas Adsorption • Who would be interested in such results? • Catalyst researchers • Chemists • Chemical engineers • Catalyst manufacturers • Catalyst users • Catalyst regenerators

  5. Reactive Gas Adsorption • Who would be interested in such results? • Petrochemical companies • Catalysts are used to produce higher octane gasoline • Catalysts are used to produce new products • New catalysts are needed to utilize biofuels • Automotive companies • Catalysts are used to reduce undesirable exhaust gases • Fuel cell companies • A fuel cell electrode is a catalyst for combining two chemicals

  6. Petrochemicals/Fine Chemicals

  7. Environex • Exxon Mobil • Honeywell • Huntsman • Hyperion • Lyondell • Sabic • Shell • Sud-Chemie • Tricat • UOP • W.R. Grace • BASF • Evonik • Ineos • Grace Davison • Haldor Topsoe • Johnson Matthey • Interkat • Bosch • Chevron • Criterion • Delphi • Engelhard

  8. Catalysts

  9. Catalysts • Catalytic Converters : Automobile Exhaust • Catalyst (platinum, palladium and rhodium) on ceramic or metal support

  10. Fuel Cells

  11. Active Sites on a Catalyst • Metal on support. • Island-like crystallites • Not all metal atoms exposed. • Adsorption technique perfectly suited. (cf Chemical analysis of entire metal content )

  12. Catalysts • Cracking process catalyzed by a zeolite : micropore structure responsible for activity/selectivity.

  13. Overview of Chemisorption

  14. How? BET surface area, pore size distribution, true density, tapped density.

  15. Active Site Quantification Because the formation of a chemical bond takes place between an adsorbate molecule and a localized, or specific, site on the surface of the adsorbent, the number of active sites on catalysts can be determined simply by measuring the quantity of chemisorbed gas

  16. Chemisorption “Static” isotherms (manometric system) Autosorb-iQ-C (auto) “Pulse” titrations (flowing systems) ChemBET (manual) ChemBET Pulsar (auto) Autosorb-iQ-C-TCD (auto)

  17. Preparation Techniques • Sample is heated under inert flow to remove adsorbed moisture. While the reduction step creates moisture, we don’t want the reducing gas to compete for diffusion to surface. • Reduce with H2: can be pure hydrogen or diluted with nitrogen or argon. Higher concentrations give higher space velocities for the same volumetric flow rate. • Purge hot!

  18. Setup Filler rod goes here Quartz wool sample capillary

  19. Static (manometric) Setup adsorptives manifold Turbo-molecular (drag) pump vent Flow “U” cell diaphragm pump furnace

  20. Vacuum Chemi – AutosorbiQ-C

  21. Extrapolation Method Vm Volume Adsorbed Pressure (mm Hg) First (only?)isotherm

  22. The Second Isotherm combined Volume Adsorbed Weak only Pressure (mm Hg)

  23. The Difference Isotherm combined Weak only Volume Adsorbed Strong Pressure (mm Hg)

  24. Principles of Calculation Monolayer Volume, Vm= volume of gas chemisorbed in a monomolecular layer

  25. Metal Dispersion

  26. Flow Chemisoroption

  27. Flow Types of Analysis A flow system permits multi-functional catalyst characterization : active sites support

  28. Temperature Programmed…

  29. Catalysts • Support : Zeolites • Framework formed, Si + O (tetrahedral arrangement) • Network of cages, cavities, channels • Responsible for catalytic activity.

  30. Catalysts • Characterization of Catalysts : NH3 TPD for Acid Site Determination

  31. Flow Chemi – AutosorbiQ-C with TCD OR Pulsar

  32. Flow Chemi, Setup (Pulsar)

  33. M M M M CO CO CO CO H2 H H H H H He N2

  34. Titration LOAD INJECT signal injections

  35. Surface Reaction by MS(linear Mass Spec. scale) TCD signal

  36. Surface Reaction by MS(linear Mass Spec. scale) TCD signal

  37. Flow Chemisorption Overview

  38. What to Measure?

  39. Which Instrument Offers What?