1、Introduction to CharacterizationCatalyst Characterization:and Testing of CatalystsPhysical Techniques for Solid MaterialsJ. R. Anderson and K. C. PrattEdited by Boris Imelik and Jacques C. VedrineAcademic press, 19851989Plenum Press, New York, 1994Book 1Book 2ReferencesPrerequisite J.W. Niemantsverd
2、riet, Spectroscopy in Catalysis, 2nd edition,Wiley-VCH, 2000. Preview Israel E. Wachs (ed.), Characterization of Catalytic Materials,Butterworth-Heinemann, 1992.Turn off cell phones James T. Richardson, Principles of Catalyst Development. Plenumpress, 1989.No talking J. M. Thomas and R. M. Lambert,
3、Characterisation of Catalysts,Keep the classroom cleanJohn Wiley and Sons Ltd, 1980. (198719901988 A.T. Bell and A. Pines (ed.), NMR Techniques in Catalysis, Marcel Dekker, Inc. 1994.About the lecturerCOURSE LEVELimportant to methods and instruments as used in catalysis research. This is a graduate
4、level course on concepts and techniques The lectures and the learning expected of you will be significantlybeyond the level and detail of that taught in the other courses and Name: Lixiong Zhangwill assume that you are already familiar with the content of such asurvey course. Office location: Chem.
5、Eng. Buld. Room 315 There will be some overlap with other curriculum; however, somenew aspects will not be fully covered in the lecture, but will require Telephone number: 67186your learning them by reading on your own. Email: This is NOT a theory of spectroscopy course. However it doesassume that
6、the student has an introductory exposure to such atheoretical background at the senior undergraduate level. Suchbackground should enable you to better appreciate what is beingmeasured with the various techniques and to understand some ofthe language used in explaining the analytical applications.REQ
7、UIREMENTSTEXTBOOK There will be a periodic assigned readings to illustrate the lecturesand enhance discussion.“ Introduction to Characterization and Testing of Catalysts”, J. R. Active participation in class is expected for those taking the courseAnderson and K. C. Pratt, Academic press, 1985.for cr
8、edit who wish to get a good grade.“Catalyst Characterization: Physical Techniques for SolidThus BOTH will be graded for completion, but not for correctness.Materials”, Boris Imelik and Jacques C. Vedrine, Plenum Press,New York, 1994.EXAMSThe course was designed around the books, so most of themateri
9、al in the course will be mainly related to the topics in thebooks (especially 1st one).There will be a Final exam (2 hours) which will reflect the entireThe first one is available from the library. It would be possible toshare a text, but it will be very hard to get through the entirecourse. It is w
10、orth 90% of the points determining the grade.course without some sort of regular access to the text.Participation will be worth 10% of the points.FTP:/10.0.4.99/ Please rely on the lecturesSyllabus (I)Syllabus (II)1Introduction2 h11Infra-red (IR) Spectroscopy2 h2Measurement of surface area 12 hChapt
11、er 112Thermal analysis2 h3Measurement of surface area 22 hChapter 113X-ray photoelectron spectroscopy2 h4Particle Size and Density2 hChapter 2&414Nuclear Magnetic Resonance2 h5Measurement of pore size2 hChapter 315Other techniques2 h6Chemical Characterization2 hChapter 516Flexible2 h7Test of catalys
12、t activity2 hChapter 617Self-study2 h8Temperature programmed techniques2 h18Self-study2 h9X-ray diffraction2 h19Self-study2 h10Electron Microscopy2 h20Final exam2 hCatalysis research (triangle)Over 80% of industrial processes involveCatalytic reactioncatalysts, and half the elements in theperiodic t
13、able are involved one way oranother in catalytic systems.BerzeliusPreparationCharacterizationof catalystsof catalystsR.A. van Santen, Theoretical Heterogeneous Catalysis, World Scientific, London, 1991CatalysisReactionReactor Eng.CatalystsCharacterizationShapeStructureWhat is characterization?To exp
14、lore the properties of catalystsand catalytic mechanisms.researchExtrudeMacroscopicDrying(trianglePreparationMesoscopicSpectrumTemp.-programmedActivationIn-situ techniqueprism)MicroscopicMolecular structureSynthesisSurface chemistryTheoretic chemistrySchematic representation of a catalytic reaction
15、Bulk properties Morphology and Composition Phase structure Particle properties Density Particle size and shape Mechanical properties Surface area Pore size distribution Diffusivity Surface properties Elemental and molecular composition Chemical status of the components Dispersion Acidity Activity Ac
16、tivity MechanismPotentialEnergyadsorptionreactiondesorptionadsorptionreactiondesorptionReaction coordinateCO + O2 = CO2Why do we need characterization ? (II)To investigate mechanisms Knowledge of catalyst composition and structure is crucial to an understanding of the factors that affect catalyst ac
17、tivity and selectivity. The catalytic properties of a surface are determined by its composition and structure on the atomic scale. It is essential to know the exact structure of a catalyst surface, including defects, steps, as well as the exact locations of the promoter atoms. Such information makes
18、 it possible to determine which portions of a catalyst are active and how changes in catalyst synthesis and pretreatment affect the propertiesof the catalytically active sites.Why do we need characterization ? (I) Check effectiveness Provide specifications for products Investigate mechanisms so that
19、 we can rationally design catalysts Examine why catalysts deactivatedWhy do we need characterization ? (III)To examine deactivation Catalyst characterization is also vital to understanding the changes that occur in the structure and composition of a catalyst following both use under reaction conditi
20、on and regeneration to reactivate the catalyst.Aim of catalyst characterizationHow to conduct catalyst characterization? The main interest is to optimize or produce an active, selective, stable and mechanically robust catalyst. In order to accomplish this, tools are needed which identify those struc
21、tural properties that discriminate efficient from less efficient catalyst.The ultimate goal In industrial research: to deal with the materials science of catalysts on a more or less mesoscopic scale. In fundamental research: to look at the surface of a catalyst atom by atom (on the atomic scale), an
22、d under reaction conditions.citenghameatsnoiphotoscatalystelectronsldefiesonicnt. mu.ralewavesCharacterizationtechniques can be derived from physical techniquesPhysical techniques Electrons: Electron microscopy Neutrals: Neutron scattering, neutron diffraction Ions: Ion scattering spectroscopy Magne
23、tic: Nuclear magnetic resonance Heat: Temperature-programmed techniques, thermogravimetry Photos: X-ray photoelectron spectroscopy EM. field: Atomic Force Microscopy Sonic wave: Photoacoustic spectroscopyWhat do we want to know? (II)6. What are the causes of catalyst aging? Does it involve a modific
24、ation of the atomic arrangements, or site blockage by poisons, or a change in the mechanical properties?7. When a foreign element is added to a material, how is it incorporated? Is there formation of a solid solution or a mixture of phases? Is phase segregation possible, e.g., at the surface? Are th
25、e electronic properties of the material affected?8. When a catalyst is supported on a solid, is there only a dispersion effect which increases the surface-to-volume ratio and thus the number of active sites? Is there a change in the properties of the support (e.g., electron transfer and acidity) and
26、/or in the active phase?9. What is the role of the transfer of electrons (active phase-support, or for alloys metal-metal), and of the geometric arrangement and size of particles of solid catalysts?What do we want to know? (I)1. What are the nature and the real number of active sites?2. What are the
27、 structure and lifetime of the intermediate complexes?3. How does the presence of the reagents modify the electronic structure and geometric array of the active sites? What modifications do the reagents undergo upon interaction with the catalyst in the course of adsorption? Can the steps leading to
28、the formation of the reaction products be followed?4. What are the chemical composition and the real atomic arrangement at the catalyst reagent surface? Are they identical at the surface and in the bulk of a solid catalyst and are they modified by the addition of reagents or during the catalytic rea
29、ction? What is the importance of the role played by the method of preparation of the catalyst?5. What is the influence of the coordination state, of the active transition metal ions, of the symmetry of their proximate environment, of the valency state, and of the degree of covalence of the metal-lig
30、and bonds?What should we use in our research? Depending on Your research purpose what information you would like to know. Availability of the instrument. Research funding.We have to remember Quick and easy experiments in catalyst characterization hardly exist. The correct interpretation of spectra r
31、equires experience based on practice and a sound theoretical background in spectroscopy, in physical chemistry and often in solid state physics as well. Intensive cooperation between spectroscopists and experts in catalysis is the best way to ensure meaningful and correctly interpreted results. The
32、most useful information almost always comes from a combination of several characterization techniques.Catalysis JournalsAdvance in Catalysis (Book Series) Microporous and MesoporousCatalysis (Book Series)MaterialsJournal of Molecular Catalysis A&B Catalysis Reviews ScienceApplied Catalysis A & Band
33、TechnologyStudies in Surface Science andJournal of Physical ChemistryJournal of CatalysisCatalysis (Book Series)Reaction Kinetics and CatalysisTopics in CatalysisLettersCatalysis LettersCATTECHCatalysis TodayCatalysis Surveys from Asia (Japan)ZeolitesCatalysis CommunicationsKinetics and CatalysisMic
34、roporous MaterialsGreen ChemistryAdsorption versus AbsorptionMeasurement of surface area (I)H H H H H H H H HPhysical adsorptionChemisorptionH2 adsorption onBET surface areapalladiumAdsorptionAbsorptionSurface processbulk processH H HH HH HH HHHH HH HHHHH HHHHHHH HH2 absorption opalladium hydrideNom
35、enclatureTypes of Adsorption ModesSubstrate or adsorbent: surface onto which adsorption can occur.Example: catalyst surface, activated carbon, aluminaAdsorbate: molecules or atoms that adsorb onto the substrate.Example: nitrogen, hydrogen, carbon monoxide, waterAdsorption: the process by which a mol
36、ecule or atom adsorb ontoPhysical adsorption ora surface of substrate.physisorptionCoverage: a measure of the extent of adsorption of a specie onto aBonding between molecules andsurfacesurface is by weak van der WaalsExposure: a measure of the amount of gas the surface had beenforces.exposed to ( 1
37、Langmuir = 10-6 torr s)coverage Tfraction of surface sites occupiedChemical bond is formed betweenH H H H H H H H HadsorbateHHHmolecules and surface.HHadsorbentChemical adsorption orchemisorptionSurface area measurementAdsorption Energetics Specific surface area: m2 g-1Potential energy (E) for adsor
38、ption is only dependent on distance Total surface area physical adsorption by BET methodbetween molecule and surface Metal and oxide surface area chemisorptionadsorbate Surface area of metal or oxide supported on the support Surface area of bulk metal or oxided Surface area of single metal or oxide
39、in mixed metals or oxidesP.E. is assumed to be independent of:surface angular orientation of molecule changes in internal bond angles and lengths position of the molecule along the surfaceAdsorption EnergeticsAdsorption Energetics- PhysisorptionPhysisorption versus chemisorptionApplications:repulsiv
40、e force surface area measurement0.3 nm pore size and volume determinationE(d) pore size distributionE(ads)E(ads)E(ads)PhysisorptionChemisorptionsmall minimalarge minimaVan der Waal forcesweak Van der Waalformation of surfacenitrogenChemisorptionattraction forcechemical bondsdsurfaceattractive forcesNote: there is no activationbarrier for physisorptiono fast processmetal surfaceAdsorption Energetics - chemisorptionChemical Adsorption ProcessesPhysisorption + molecular chemisorptionre = equilibrium bond distanceApplications: active surface areaCOmeasurementsE(d) surface site energetic
