Characterization of Solid Catalysts in the Functioning State by Nuclear Magnetic

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1、Adv.Catal.50(2006)149–225CharacterizationofSolidCatalystsintheFunctioningStatebyNuclearMagneticResonanceSpectroscopyM.HUNGERInstituteofChemicalTechnology,UniversityofStuttgart,D-70550Stuttgart,GermanyandW.WANGStateKeyLaboratoryofAppliedOrganicChemistry,LanzhouUniversity,7300

2、00Gansu,P.R.ChinaThischapterisareviewoftechniquesandapplicationsofsolid-statenuclearmagneticres-onance(NMR)spectroscopyforinvestigationsofsolidcatalysts,withastrongemphasisoninvestigationsofcatalystsinthefunctioningstate.Thetechniquesallowinvestigationsofboththechemicalreact

3、ionsaswellaschangesinthecatalyststakingplaceinsidetheNMRspectrometer.Theexperimentaltechniquesaresuitableformagic-anglespinning(MAS)NMRspectroscopyunderbatchreactionconditions,forexample,withasampleofcatalystpowderinasealedglassampouleoragas-tightMASNMRrotor,orunderflowcondit

4、ions,forexample,withthecatalystparticlesinanMASNMRrotorreactor.Theformertechniquehastheadvantageoflowcostandcommerciallyaccessibleequipment,andthelattertechniqueallowsmeasurementsundercondi-tionsclosetothoseofindustrialprocesses.Representativeapplicationsdescribedinthisrevie

5、wincludeinvestigationsofthefateofisotopiclabelsallowingtheindirectcharacterizationofthenatureoftransitionstatesandreactionpathwaysbyisotopescramblingandthedeterminationofactivationenergiesofthereactionsinthepathways.Otherexamplesincludeinvestigationsoforganicdeposits,surface

6、complexes,andreactionintermediatesformedintheporesofzeolitecatalystsundercontinuous-andstopped-flowreactionconditions.Furtherapplicationsincludeinvestigationsofchangesinthelocalstructureofframeworkatomsandsurfacesitesinmicro-porouscatalystsresultingfromadsorptionanddesorption

7、ofprobemoleculesandreactants.Abbreviations:CAVERN,cryogenicadsorptionvesselenablingrotornestling;CF,continuous-flow;CRAMPS,combinedrotationandmultiple-pulsespectroscopy;Cs,NaY,zeoliteNa-Y(FAU)exchangedwithcesiumcations;CP,crosspolarization;CT,centraltransition;DABCO,1,4-diaza

8、bicyclo-(2,2,2)-octane;DCAA,dichloroaceticacid;DCAC,dichloroacetylchloride;