Advanced Techniques For Characterization Of Heterogeneous .
Graduate School of Materials Research (GSMR)Graduate School in Chemical Engineering (GSCE)Department of Chemical Engineering (ÅA)Advanced techniques for characterizationof heterogeneous catalysts(4 credits/sp/op/Bologna)Main lecturer:Prof. Andrey SimakovCentro de Nanociencias y NanotecnologiaUniversidad Nacional Autonoma de MexicoLecturers:Prof. Tapio Salmi, Åbo AkademiProf. Dmitry Murzin, Åbo AkademiProgramMonday, 26.059.15Opening remarksThe scope of the course.In situ and operando spectroscopic techniques for characterizationof heterogeneous catalysts.Non-steady-state kinetic methods for heterogeneouscatalysts characterization.Concept of transient analysis. Main definitions.Advanced techniques for characterization of heterogeneous catalysts
ProgramTuesday, 27.059.15Transient analysis of catalytic reactions including in situ andoperando spectroscopic measurements.Advanced techniques for characterization of heterogeneous catalystsProgramWednesday, 28.059.15Transient analysis of catalytic reactions using isotopes.Applications of Temporal analysis of products (TAP) in analysis ofcatalytic reaction mechanisms.Thursday, 29.059.15Transient analysis of three-phase catalytic reactions.Numerical aspects.Advanced techniques for characterization of heterogeneous catalysts
The scope of the courseNonin situ/operando experiments provideNon-steadysteady-state and /insitu and /okinetic and spectroscopic information that is critical for comparison of non-steady-state performance ofdifferent catalysts, development of a dynamic kinetic model ofcatalytic transformations, design of efficient catalytic reactors particularthose that work under non-steady-state conditions.The goal of this course is to improve your skill in the application of theseadvanced methods for analysis of heterogeneous catalytic reactions anddesign new effective heterogeneous catalysts.Advanced techniques for characterization of heterogeneous catalysts. Part 1In situ and operando spectroscopic techniquesfor characterization of heterogeneous catalystsAdvanced techniques for characterization of heterogeneous catalysts. Part 1
In situ and operando spectroscopic techniques for characterization of heterogeneous catalystsCatalysis, like other branches of chemistry, developed in its own way:the phenomenologicalperceptionunderstanding of the processeson molecular levelIn the beginning were steady-state kinetic experiments the generallyapplied experimental method, but nowadays the frontiers are the differentkinds of surface spectroscopy with atomic scale resolution.Advanced techniques for characterization of heterogeneous catalysts. Part 1In situ and operando spectroscopic techniques for characterization of heterogeneous catalystsFundamental structure–activity/selectivity relationships are critical for thedevelopment of knowledge-based design of new and novel catalyticmaterials for different applications.True fundamental understanding of the structure–activity/selectivityrelationship requires molecular level characterization of catalyticmaterials under realistic catalytic operation conditions.Advanced techniques for characterization of heterogeneous catalysts. Part 1
EtymologyFirst partIN SITUThe term in situ spectroscopy is well established and widely usedin the catalysis literature.Etymologically, the term in situ has no temporal discrimination.Advanced techniques for characterization of heterogeneous catalysts. Part 1In situit is possible to describe several different types of in situ studies:(a) “In situ” describes the collection of spectra of a catalytic sample in thesame environment were it has been treated or pretreated and thetemperature may no longer be that of the pretreatment.Advanced techniques for characterization of heterogeneous catalysts. Part 1
In situit is possible to describe several different types of in situ studies:b) Variable-programmed “in situ” spectra describes the spectramonitor the transformations occurring versus a variable.Variable-programmed in situ studies may follow the materials undermany conditions relevant to catalysis (pressure, temperature, reactantconcentration, etc.).Advanced techniques for characterization of heterogeneous catalysts. Part 1In situit is possible to describe several different types of in situ studies:c) “Reaction in situ” refers to in situ spectroscopic measurement underreaction conditions relevant to catalytic operation. Many in situ reactor celldesigns may not be appropriate for true catalytic reaction kinetic studiesbecause of complications from gas phase reaction due to large voidvolumes or heat and mass transfer gradients.However, many IN SITU reactor cell designs may not be appropriatefor TRUE catalytic reaction kinetic studies due to large void volumes orheat and mass transfer gradientsAdvanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of IN SITU cellsAfter nearly 60 years of intensive application, infrared spectroscopy (IR)remains the most widely used, and usually most effective, spectroscopicmethod for characterization of surface chemistry of heterogeneouscatalysts.catalystsThe IR cell in which the catalyst sample is pre-treated and subsequentlystudied is extremely important in surface studies.Advanced techniques for characterization of heterogeneous catalysts. Part 1Examples of IN SITU cellsThe one of the first in situ cells for IR studies published in scientific literaturewas:R.P. Eischens, S.A. Francis and W.A. Pliskin, J. Phys. Chem., 60 (1956) 194.In order to reveal the relative strength of bonding for the chemisorbed COcontributing to each band or the effect of interaction on the band positions thespectra of chemisorbed CO were studied as a function of surface coverageover silicasilica-supported Pt, Pd and Ni.NiThe authors wrote: "In order to carry out this work efficiently it was necessary todesign apparatus in which the IR spectra could be obtained while the sampleswere subjected to a wide range of temperatures and pressures. Successfuldevelopment of this in situ apparatus not only makes it possible to study the effectof surface coverage but also opens the way to IR studies of chemisorbedmolecules while reactions are in progress".Advanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of IN SITU cellsThe perfect, allall-purpose cell has yet to be devised,devised and cell design isnormally chosen to suit the purposes of a particular study.In catalytic research very often "home-made" IR cell reactors are usedfor the particular in situ studies.Advanced techniques for characterization of heterogeneous catalysts. Part 1Examples of IN SITU cellsPeri and Hannan [J.B. Peri, R.B. Hannan, J. Phys. Chem., 64 (1962)1526] designed an quartz IR cell for the determination of the surfacehydroxyl groups on γ-aluminaAdvanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of IN SITU cellsRyason [P.R. Ryason, Rev. Sci. Instrum., 44 (1973) 772. ] has described a stainlesssteel quartz cell for IR transmission spectroscopy of catalyst waferscross section of infrared cellConflat flangecell insertConflat flangeConflat flangeConflat flangerotable magnetConflat flangestainless steel-Pyrex sealsilica thermocoupletube bundlerotable heat shieldConflatflangefused silica tubeholes for thermocouple wiresConflat flangethermocouple junctionholderremovable silicawafer holderViton gasketthermocouple shieldsalkali halide windowplatinum wirefurnaceAdvanced techniques for characterization of heterogeneous catalysts. Part 1Examples of IN SITU cellsProkopowicz et al. [R.A. Prokopowicz, P.L. Silveston, F.L.Baudais, D.E. Irish, R.R. Hudgins, Appl. Spectrosc., 42 (1988)385 ] have presented a design of a transmission IRcell for the high-temperature study of transientadsorption and reaction in a flow systemAdvanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of IN SITU cellsDesign of the high temperature IR cell for transient experimentsSet-up was designed for study of Heat ofAdsorption of Carbon Monoxide on aPt/Rh/CeO2/Al2O3 Three-Way Catalystat High Temperatures, JC,179,1998,5031 – CaF2 windows,2 – catridge heaters,3 – Viton O-rings,4 – vacuum line,5 – gas inlet,6 – gas outlet,7-8 – cooling water inlet-outlet,9 – sample holder,10 – disk of catalystbody of the cellsample holderAdvanced techniques for characterization of heterogeneous catalysts. Part 1Examples of IN SITU cellsHome made FTIR cell for fast transientsIn order to observe fast surface transients, it is required that the reactorhas a low dead volume, and a reactor was constructed with this as a majordesign criterion.A cylindrical, CaF2 rod (A) slidesthrough internal O-rings located onboth halves. A sample pellet is heldbetween the CaF2 rods when the twohalves are bolted together. Gasflows into and out of the cellthrough small holes (B) and iscontained within the volume sealedby the O-ring (C). Chilling fluid iscirculated through ports in the bodyof both halves (D).The reactor volume surrounding the waferis theoretically 0.05 cm3 !!!Advanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of IN SITU cellsCommercial InIn-Situ HighHigh-Low Pressure Infrared Reactorfrom ININ-SITUSITU-Research InstrumentsIn-Situ-Research InstrumentSize o.d. 4",height 3.75“Operating Pressures 10-5 torr - 15 atmMaterialStainless Steel Windows CaF2 or any otherstandard IR transparent materialCatalyst SampleSize 2 cm o.d., typically 80 mg of solidTemperature Control/MeasurementOne mini-thermocouple for reactor body tempcontrol and one for sample surface measurementFlow Pattern:Gases are flown parallel on both sides of thewafer Gaskets Viton O-ringsHarrick High Temperature CellAdvanced techniques for characterization of heterogeneous catalysts. Part 1Examples of IN SITU cellsCommercial Reaction Chamberfrom Harrick Scientific for DRIFT analysisThe Low Temperature Reaction Chamber, CHC-CHA,is designed for operation from -150 C to 600 C undervacuum.In addition to the heater incorporated in the sample stage,the CHC also features a cooling conduit connected to adewar.Main parts of ChamberAdvanced techniques for characterization of heterogeneous catalysts. Part 1Optical accessories
it is possible to describe several different types of in situ studies:c) “Operando” methodology describes “in situ” spectra under true catalyticoperation as determined by simultaneous online activity/selectivitymeasurements.Advanced techniques for characterization of heterogeneous catalysts. Part 1OperandoOperando spectroscopic methodology has just recently beenintroduced into the catalysis literature in 2002. This technique combinessimultaneous in situ spectroscopy and kinetic measurements on thesame sample and time.Operando is borrowed from Latin, which means “working” or “operating”since the spectra are of an “operating” catalyst, whereas, “in situ” means“on site”.Advanced techniques for characterization of heterogeneous catalysts. Part 1
OperandoSome historical remaks The first Operando Congress was celebrated in Lunteren,Netherlands, 2–6 March 2003. The Second Operando Congress was celebrated in Toledo,Spain, 23–27 April 2006. The Next Operando Congress will be celebrated in 2009.Advanced techniques for characterization of heterogeneous catalysts. Part 1OperandoLater we’ll consider an overview of the different multiple technique operando set-upscurrently available for obtaining combined spectroscopic and catalyticinformation on heterogeneous catalytic systems. Also some difficulties, which can be encountered during the developmentof these set-ups, will be mentioned. In a third part, it will be shown that there are, besides obtainingcomplementary information on the same catalyst system under identicalreaction conditions, additional advantages for combining spectroscopictechniques.Advanced techniques for characterization of heterogeneous catalysts. Part 1
Examples of Operando set-upsOperando ESR cell developed in the group of Brückner (Berlin, Germany)It has been used to study for instance thebehavior of vanadium phosphate catalysts during theoxidation of n-butane, the dehydrogenation of alkanes oversupported chromium oxide catalysts and the selective catalytic reduction of NOxover supported manganese oxide catalysts.operandoESRset-up probesparamagnetictransitionmetalions orIt isThesimilarwith thatdevelopedin my groupin the BoreskovInstituteof Catalysisorganicradicalspresentin theworkingdehydrogenationcatalytic solid. of butanes20 years agowhich wasappliedfor studyof oxidativeover V-Mg-O catalysts.Advanced techniques for characterization of heterogeneous catalysts. Part 1Examples of Operando set-upsEach characterization technique allowsobtaining additional information aboutthe catalytic system positioned in thereactor tube.The adding additional spectroscopictechniques is most valuable if theyprovide complementary information!!!So, identical pieces would not display the wholepicture of the catalytic problem and would notenable us to discriminate between activespecies (cyclists) and spectator species.Advanced techniques for characterization of heterogeneous catalysts. Part 1
Combining operando techniques in one spectroscopicspectroscopic-reaction cell:cellNew opportunities for elucidating the active site and related reactionmechanism in catalysisIt would be more advantageous to look on catalytic systems from differentperspectives by making use of multiple characterization techniquesAdvanced techniques for characterization of heterogeneous catalysts. Part 1Examples of Operando set-upsAn example of two techniques combined in one set-upTheoperandoUV–visset-upallows to measured–d transitionsand oxideSchemeandpicture of anoperandoUV–vis/Ramanset-up for themeasuringsupported nmetaloxidesandthecatalysts operating in gas-phase reactions at elevated temperatures and ambient pressures.formation of organicviaUniversity.their n–π*π–π* transitions underSet-up ismoleculesbuilt in UtrechtTheorNetherlands.working conditionsAdvanced techniques for characterization of heterogeneous catalysts. Part 1
An example of three techniques combined in one set-upExamples of Operando set-upsAn operando UV–UV–vis/Raman/EDvis/Raman/ED--XAFS setset-upfor measuring supportedmetal oxide catalystsoperating in gas-phasereactions at elevatedtemperatures andambient pressures.Detailed outline of the capillaryreaction-spectroscopy cell forsimultaneously measuringRaman/UV–vis (reflectance mode)and energy dispersive XAFS(transition mode), together withillustrative picturesUtrecht University, The NetherlandsAdvanced techniques for characterization of heterogeneous catalysts. Part 1An example of three techniques combined in one set-upExamples of Operando set-upsThe setup for parallel operando EPR/UV–EPR/UV–vis/Ramanvis/Raman measurementsBuilt in the Institut für Angewandte Chemie Berlin, GermanyAdvanced techniques for characterization of heterogeneous catalysts. Part 1
OperandoOperandoOverview of operando set-ups making use of multiple spectroscopiccharacterization techniquesExisting combinations of techniques for studying heterogeneous catalysts at work:S. J. Tinnemans, J. G.Mesu, K.Kervinen, T.Visser, T. A. Nijhuis, A.M.Beale, D.E. Keller, Ad M.J. van der Eerden and B.M.“Combining operando techniques in one spectroscopic-reaction cell: Newopportunities for elucidating the active site and related reaction mechanism incatalysis” Catalysis Today V.113, I.1-2,2006, Pages 3-15WeckhuysenAdvanced techniques for characterization of heterogeneous catalysts. Part 1OperandoOverview of operando set-ups making use of multiple spectroscopiccharacterization techniquesExisting combinations of techniques for studying heterogeneous catalysts at work:S. J. Tinnemans, J. G.Mesu, K.Kervinen, T.Visser, T. A. Nijhuis, A.M.Beale, D.E. Keller, Ad M.J. van der Eerden and B.M.“Combining operando techniques in one spectroscopic-reaction cell: Newopportunities for elucidating the active site and related reaction mechanism incatalysis” Catalysis Today V.113, I.1-2,2006, Pages 3-15WeckhuysenAdvanced techniques for characterization of heterogeneous catalysts. Part 1
OperandoOverview of operando set-ups making use of multiple spectroscopiccharacterization techniquesExisting combinations of techniques for studying heterogeneous catalysts at work:S. J. Tinnemans, J. G.Mesu, K.Kervinen, T.Visser, T. A. Nijhuis, A.M.Beale, D.E. Keller, Ad M.J. van der Eerden and B.M.“Combining operando techniques in one spectroscopic-reaction cell: Newopportunities for elucidating the active site and related reaction mechanism incatalysis” Catalysis Today V.113, I.1-2,2006, Pages 3-15WeckhuysenAdvanced techniques for characterization of heterogeneous catalysts. Part 1OperandoSome remarksThe first operando techniques combined in one set-up and reported in theopen literature were X-ray diffraction (XRD) and X-ray absorptionspectroscopy (EXAFS). XRD provides long-range ordering information ofthe catalytic solid under investigation, whereas EXAFS is sensitive to theshort-range ordering of the materials under study.Most combinations involve the use of vibrational (IR as well as Raman)and electronic (UV–vis) spectroscopies.In the case of magnetic resonance techniques (NMR and EPR) moretechnical hurdles have to be taken to make the combined operando set-upworking.Advanced techniques for characterization of heterogeneous catalysts. Part 1
OperandoConcluding remarksThe coupling approach in which two or more spectroscopic techniques are combined inone spectroscopic-reaction cell seems to be very powerful for elucidating the chemistry ofcatalyst materials, the mechanism of a catalytic reaction and the identification of activesites in heterogeneous catalysts.This approach looks at first sight simple, but a lot of experimental hurdles have to betaken before a successful set-up can be applied to a particular catalytic problem. As anexample the high intensity radiation, such as synchrotron sources for measuring XAFSdata, may affect the catalytic process under investigation. By using a second technique,it is possible to evaluate the effect of such intense light sources on the investigatedsystem.Advanced techniques for characterization of heterogeneous catalysts. Part 1OperandoConcluding remarksEvaluation of the still limited amount of literature reveals that there are – roughlyspeaking – two types of research groups working in the field of operandospectroscopy1. On one hand, there are people focusing on the inorganic part of thecatalyst material. More in particularly, these researchers make use oftechniques, such as operando UV–vis and EPR spectroscopies, to test theoxidation state of a particular supported transition metal ion.2. On the other hand, there are scientists putting more emphasis on theorganic part of a catalytic reaction. These research groups use e.g.operando NMR and IR spectroscopies.Advanced techniques for characterization of heterogeneous catalysts. Part 1
OperandoConcluding remarksFinally, other fields of catalysis are still hardly explored. An example of anunder developed area of research is the study of heterogeneous catalystsoperating in the liquid phase. Only a limited number of studies report on theuse of operando spectroscopy on catalytic solids in the liquid phase.Perhaps, that the coupling of IR-ATR, in combination with other operandotechniques, opens new avenues to gather detailed insight in these importantcatalytic processes.detectorIR beamCatalyst as the finesolid particles in thin cellFlow inMIRROWFlow outAdvanced techniques for characterization of heterogeneous catalysts. Part 1NonNon-steadysteady-state kinetic methods for heterogeneouscatalysts characterizationAdvanced techniques for characterization of heterogeneous catalysts. Part 1
Non-steady-state kinetic methods for heterogeneous catalysts characterizati
IN SITU The term in situ spectroscopy is well established and widely used in the catalysis literature. First part Etymology Etymologically, the term in situ has no temporal discrimination. Advanced techniques for characterization of heterogeneous catalysts.
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