Download - Chemical Reaction kinetics in practice
-
FEATURE
6OLUMENO
#HEMICALREACTIONKINETICSINPRACTICE
4HECHEMICALREACTIONSTAKINGPLACEINTHECHEMICALREACTORFORMTHEHEARTOFANYCHEMICALPROCESS2EACTIONKINETICSARETHETRANSLATIONOFOURUNDERSTANDINGOFTHECHEMICALPROCESSESINTOAMATHEMATICALRATEEXPRESSIONTHATCANBEUSEDINREACTORDESIGNANDRATING"ECAUSEOFTHEIMPORTANCEOFCORRECTANDSAFEDESIGNOF CHEMICALREACTORS CHEMICALREACTIONKINETICS ISAKEYASPECT OF RESEARCHANDDEVELOPMENTINCHEMICALINDUSTRIESINRESEARCHINSTITUTESANDACADEMICCENTERSASWELLASININDUSTRIALLABORATORIES4HEREISANDTHEREWILLALWAYSBEASTRONGNEED FORKNOWLEDGEANDA SKILL BASE CONCERNING THEDETERMINATIONOF REACTIONKINETICSANDTHEIRAPPLICATIONINTHEFORMOFAKINETICMODEL4HISPAPER ISA RESULT OF COOPERATIONWITHIN%UROKINA CONSORTIUMOF OVER%UROPEANCOMPANIESANDUNIVERSITIES!NINDUSTRIALQUESTIONNAIRE INHIGHLIGHTEDTHATINDUSTRYISNOTONLYALITTLECONSERVATIVEINTHEMETHODSITUSESTODETERMINEKINETICSBUTALSOTHATTHEREWASAWIDEAWARENESSOFTHESCOPEFORIMPROVEMENT%UROKINWAS THUS FOUNDED IN TO TRYAND ESTABLISH THEBESTPRACTICESANDTOFACILITATEDEVELOPMENTWORKINKINETICSANDASSOCIATEDAREAS4HEPAPERBRIEmYEXPLAINS SOMEUNDERLYINGTHEORYOFHETEROGENEOUSLY CATALYZEDCHEMICALREACTIONSANDTHEIRKINETICS)TDEALSSPECIlCALLYWITHTHEACQUISITIONOFKINETICDATAANDGIVES RECOMMENDATIONS FOR THE SELECTION OF THE EXPERIMENTALREACTORANDCONDITIONS!PRIMARYAIMOFTHISPAPERISDISCUSSKINETICEXPERIMENTATIONANDMODELING THROUGHA SERIES OF CASE STUDIES ATTEMPTING TO ILLUSTRATEGOODPRACTICEMETHODSINKINETICMODELINGPITFALLSANDRECOMMENDATIONS4HEPAPERCLOSESWITHSOMERECOMMENDATIONSANDAPERSPECTIVEONTHEFUTURENEEDSOFINDUSTRIALREACTIONKINETICS
2OB*"ERGER%(UGH3TITT'UY"-ARIN&REEK+APTEIJN*ACOB!-OULIJN
CORRESPONDINGAUTHOR3YNETIX0/"OX"ILLINGHAM#LEVELAND43,"53!4EL&AXEMAILHUGH?STITT ICICOM
-
%UROKIN
CHEMICALREACTIO
NKINETICSINP
RACTICE
7HATAREKINETICSh+INETICSv IS SIMPLY A TECHNICAL TERM USED TO DESCRIBETHERATEOFACHEMICALPROCESS SUCHASACATALYTICREACTIONAS A FUNCTION OF THE CONDITIONS 4HE MODELS AND THEIRMATHEMATICALMANIFESTATIONSVARYENORMOUSLYINTHELEVELOFCOMPLEXITYANDTHEDEGREETOWHICHTHEYREmECTTHEACTUALCHEMICALANDPHYSICALPROCESSESOCCURRING!TTHEIRSIMPLESTTHEYCANBEOFTHEFORMRATEtF4CONCENTRATIONN WHERENISTERMEDTHEORDEROFREACTION7ITHHETEROGENEOUSCATALYTICREACTIONSTHERE ISMORETHANONE RATE PROCESS OCCURRING IN SERIES 4HE REACTION PROCESSCANBEBROKENDOWNINTOANUMBEROFIDENTIlABLESTEPSALLWITHTHEIROWNRELEVANTRATEEQUATIONSOMEOFWHICHMAYBECOMBINEDINTOANOVERALLREACTIONRATEEQUATION4HESTEPSTYPICALLYCITEDARE -ASSTRANSFEROFREACTANTSTOTHECATALYSTSURFACE !DSORPTIONOFREACTANTSONTOCATALYSTACTIVESITES #ATALYTICREACTION $ESORPTIONOFREACTIONPRODUCTS -ASSTRANSFEROFPRODUCTSAWAYFROMSURFACE3TEPS AND ARE IDENTIlABLE mUID PHASE PHENOMENAAS DISTINCT FROM THE SURFACE PROCESSES THAT CHARACTERIZEADSORPTIONANDREACTIONANDSPECIlCALLYACATALYTICREACTION4HEYCANANDINDEEDSHOULDHAVETHEIROWNRATEEQUATIONSBUTDONOTALWAYSDOSOINPRACTICE4HE SURFACE PROCESS ITSELF ALSO TYPICALLY COMPRISES A
NUMBER OF DISCRETE STEPS !T ITS SIMPLEST THIS MAY BEENVISAGED AS THE SORPTIONnREACTIONnDESORPTION SEQUENCECITED ABOVE4HE NEXT LEVEL OFMODEL COMPLEXITY THEREFOREINCLUDESTHESESTEPSEITHERASSIMPLESTEPSORASCOMPETITIVEADSORPTION OF TWO REACTANTS OR A REACTANT AND ANOTHERCOMPONENTSUCHASASOLVENTORDILUENT4HISCANBEDONE
IMPLICITLYWITHINAMATHEMATICALEXPRESSIONFORTHEREACTIONRATE !T THEIR MOST COMPLEX THE REACTION RATE EXPRESSIONCANBEBASEDONTHEMECHANISTICORELEMENTAL STEPSOF THEREACTION4HISCANHAVEINCREASEDMATHEMATICALCOMPLEXITYBUTISGENERALLYABETTERPHYSICALREPRESENTATIONOFTHEPROCESS'IVENTHEABOVEANUMBEROFQUESTIONSARISE7HYARE
KINETICMODELSREQUIRED7HYISTHERESUCHDIVERSITYINTHEFORM AND EXACTITUDE OF KINETIC AND RATEMODELS(OW ARETHEEXPERIMENTALDATAMEASURED!NDHOWARE THEMODELSDERIVEDANDlTTED4HISPAPERWILLATTEMPTTOANSWERTHESEQUESTIONSINTHECONTEXTOFANINDUSTRIALVIEWPOINT!KEYISSUEISTHATASKINETICMODELSINCREASEINCOMPLEX
ITYTHEEXPERIMENTALEFFORTTHERANGEANDSCOPEOFEXPERIMENTATION REQUIRED TO BUILD lT AND VALIDATE THE MODELALSOINCREASE4HEPERCEPTIONININDUSTRYAPPEARSTOBETHATTHEEFFORT REQUIRED INCREASESBEYONDTHEPROPORTIONALGAININ BENElT 4HEREFORE FROM THE POINT OF VIEW OF INDUSTRYTHENEEDFORCOMPLEXMODELSBASEDONTHEPHYSICOCHEMICALEVENTS MUST EITHER BE JUSTIlED OR THE EFFORT REQUIRED TODERIVETHEMSIGNIlCANTLYREDUCED4HIS PAPER WILL THEREFORE EXPLAIN AND ILLUSTRATE THE
NEED FOR AND THE METHODS USED TO OBTAIN RELIABLEKINETIC DATA FOCUSING ON HETEROGENEOUS CATALYSIS )T WILLDEAL WITH THE ACQUISITION OF KINETIC DATA GIVE SOMETHEORETICAL BACKGROUND ON KINETICS AND KINETIC MODELINGAND WILL PROVIDE RECOMMENDATIONS FOR THE SELECTION OFTHE EXPERIMENTAL REACTOR AND CONDITIONS !MAJOR PART OFTHE PAPERWILL CONSIDER KINETICMODELING THROUGH THE USEOF A SERIES OF CASE STUDIES ATTEMPTING TO ILLUSTRATE GOODPRACTICE METHODS IN KINETIC MODELING AND PITFALLS ANDRECOMMENDATIONS)NVIEWOFTHELIMITEDSPACEMASSTRANSFERANDHYDRODYNAMIC ASPECTSWILL NOTBE COVERED IN THE CASE
%UROKININDUSTRYACADEMIACOLLABORATIONTOWARDSBETTERKINETICSINTERMEZZO
%UROKIN ISACONSORTIUMOF%UROPEANBASEDCOMPANIES TOGETHERWITHANUMBEROFACADEMICCENTERSFOCUSEDONDEVELOPINGPRACTICEINKINETICMODELING7EBSITEWWWEUROKINORG)TWASESTABLISHEDINAFTERTHENEEDWASREALIZEDVIAAQUESTIONNAIREEXTENSIVELYCITED IN THIS PAPER AND TWO WORKSHOPS IN TO BETTERDElNE NEEDS AND COLLECTIVE DRIVERS )T CURRENTLY CONSISTS OF COMPANIES !KZO .OBEL $OW "ENELUX $3- 2ESEARCH )&04ECHNIP"ENELUX3HELL2ESEARCHAND4ECHNOLOGY#ENTRE3TATOIL,INDE%NI4ECNOLOGIE3YNETIXAND%##HEM4ECHNOLOGIESANDFOUR ACADEMIC CENTERS $ELFT 5NIVERSITY OF 4ECHNOLOGY 'HENT5NIVERSITY .45 4RONDHEIM AND5# ,OUVAIN 4HEMEMBERSHIPBASE IS EVIDENTLY VERY BROAD FROM SEVEN DIFFERENT COUNTRIESAND COMPANY ACTIVITIES IN OIL AND GAS PETROCHEMICALS BULKAND lNE CHEMICALS MANUFACTURE ENGINEERING CONTRACTING TO THEOIL PETROCHEMICALS AND lNE CHEMICALS MARKETS AND A CATALYSTCOMPANY
%UROKINS STATED AIM IS TO PRODUCE A PRECOMPETITIVE TOOLKIT FORMEASURINGKINETICDATAANDMODELDEVELOPMENTFORHETEROGENEOUSCATALYTICSYSTEMS4HEACTIVITIESARECURRENTLYFOCUSEDONI %XPERIMENTAL METHODS TO DETERMINE REACTION KINETICS EGINVESTIGATIONOFTHECAPABILITIESOFDIFFERENTTYPESOFLABORATORYREACTORSTOMEASURETHEKINETICSOFSPECIlCREACTIONCLASSES
II $EVELOPMENTOFMODELSFORASETOFSELECTEDLABORATORYREACTORSYSTEMSTOBEUSEDFORPROCESSINGEXPERIMENTALDATAANDORTHE DETERMINATION OF SUITABLE EXPERIMENTAL CONDITIONS EGTOASSESS IF THEPROPOSEDEXPERIMENTALCONDITIONSARE IN THEKINETICALLYORTHEMASSTRANSFERCONTROLLEDREGIME
III-ETHODS FOR THE DETERMINATION OF KINETIC MODELS FROMEXPERIMENTALDATAINCLUDINGMODELDISCRIMINATIONPARAMETERESTIMATIONANDDESIGNOFEXPERIMENTS
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
STUDIES4HEPAPERWILLCLOSEWITHAFORWARDLOOKINGSECTIONCONSIDERINGTHEFUTURENEEDSOFINDUSTRIALREACTIONKINETICS
7HYDOWENEEDKINETICMODELS4HISPAPERISARESULTOFCOOPERATIONWITHIN%UROKIN)NTERMEZZOACONSORTIUMOFOVER%UROPEANCOMPANIESAND UNIVERSITIES ESTABLISHED IN SPECIlCALLY TO FACILITATEACTIVECOLLABORATIONINTHElELDOFCATALYTICREACTIONKINETICS4HIS INITIATIVE BY SO MANY LEADING COMPANIES GIVES ANINDICATION OF THE IMPORTANCE THAT THE CHEMICAL INDUSTRYATTACHESTOKINETICS"UTWHYAREKINETICSIMPORTANT+NOWLEDGE OF THE RATE OF A CATALYTIC REACTION AND ITS
SELECTIVITYASAFUNCTIONOFTHEPROCESSCONDITIONSANDREACTANTCONCENTRATIONSISESSENTIALFORTHEAPPLICATIONOFTHECATALYSTIN A COMMERCIAL REACTOR-ORE SPECIlCALLY THE KINETICS OFTHEREACTIONAREREQUIREDINTHEFORMOFAMATHEMATICALRATEEXPRESSIONTHATCANBEUSEDTORELIABLY TRANSLATE LABORATORYANDPILOTSCALEDATAINTOTHEDESIGNOFACOMMERCIALSCALEUNIT4HAT RATEORKINETICEXPRESSION TELLSHOWTHE REACTION RATEVARIESWITHPROCESSCONDITIONSSUCHASTEMPERATUREPRESSUREANDCOMPOSITIONANDPREFERABLYALSOWITHAMEASUREOFTHEVOLUMETRICCONCENTRATIONOFCATALYTICSITES4HEIMPORTANCEOF A REACTIONS KINETICS IS THAT THE RATE AND SELECTIVITY OF AREACTION DETERMINE THE SIZE OF THE CATALYTIC REACTOR FOR AGIVENOVERALLPRODUCTION RATE7ITHOUT A RELIABLEMEANS TOPREDICTTHEREACTIONRATETHEREACTORDESIGNCOULDBEHIGHLYSPECULATIVE4HEREARESEVERALEFFECTSTHATCANARISEFROMTHISUNCERTAINTY&IRSTLYWITHOUTRELIABLEESTIMATESOFTHECAPITALCOSTSNEEDEDTOBUILDAPRODUCTIONPLANTANDTHEPROBABLEOPERATINGCOSTSITISNOTPOSSIBLETOCARRYOUTAMEANINGFULEVALUATION OF THE ECONOMIC MERITS OF BUILDING THE PLANTAND WITHOUT A PERSUASIVE ECONOMIC IMPERATIVE THE PLANTIS UNLIKELY TO BE SANCTIONED 3ECONDLY AND PERHAPS MOREIMPORTANTLYWITHOUTRELIABLEKINETICSITISNOTFULLYPOSSIBLETOEVALUATETHESIDEREACTIONSANDTHEDYNAMICEFFECTSTHATMAYOCCURINTHEREACTORWHICHISACRITICALSTEPINASSESSINGTHEOPERATIONALSAFETYANDENVIRONMENTALIMPACTOFACHEMICALSPRODUCTIONUNIT
7HATDOESINDUSTRYUSEKINETICSFOR4HE IMPORTANCE OF KNOWLEDGE AND OF HAVING A SKILL BASECONCERNINGTHEDETERMINATIONOFREACTIONKINETICSANDTHEIRAPPLICATION IN THE FORM OF A KINETIC MODEL IS CLEAR 4HISBEGS THE QUESTION OF HOW GOOD INDUSTRY IS AT MEASURINGAND APPLYING CHEMICAL RATE MODELS AND WHAT PRECISELY ITDOES WITH THEM 4HIS WAS PUT TO THE TEST IN WHENTHEh#HEMICAL%NGINEERINGINTHE!PPLICATIONSOF#ATALYSISv7ORKING 0ARTY OF THE %UROPEAN &EDERATION OF #HEMICAL%NGINEERINGAPPROVEDASURVEYOFINDUSTRIALPRACTICEINTHEMEASUREMENTANDEVALUATIONOFKINETICS4HERESULTSOFTHISSURVEYWEREPUBLISHEDININSUMMARYFORM;=4WENTYFOUR CHEMICAL ANDOIL COMPANIES ENGINEERING CONTRACTORSANDCATALYSTMANUFACTURERSRESPONDEDTOTHEQUESTIONNAIREANDTHATLEVELOFRETURNINDICATESHOWSERIOUSLYINDUSTRYTAKESTHIS ISSUE 4HE RESULTS MAKE INTERESTING READING NOT ONLYFROM THE VIEWPOINTOFHOW INDUSTRY TREATS ITS KINETICSBUTALSOTHEDIVERSITYACCORDINGTOTHEINDUSTRYSECTOROFHOWTHEY USE THEM !DDITIONALLY A SURVEY OF THE GAPS ANDNEEDS FOR CATALYSIS IN %UROPEAN INDUSTRY;= STRESSED THEIMPORTANCE OF FURTHER DEVELOPMENTS IN KINETICS RESEARCH#ONSIDER lRSTLY HOW COMPANIES USE THEIR KINETICS THE
PERCEIVED REASON FOR THEDETERMINATIONOF KINETIC AND RATEMODELS 4HE OVERALL RESULTS FROM THE SURVEY ARE SHOWN IN&IGUREANDINDICATEAFAIRLYEVENTHREEWAYSPLITBETWEENCATALYST DEVELOPMENT PROCESS DEVELOPMENT AND PROCESSOPTIMIZATION3IGNIlCANTLYTHEREISONLYSMALLMINORITYUSEOFKINETICDATAFORMECHANISTICRESEARCHBYCONTRASTAMAJORFORCEINACADEMIA7HENTHESAMEDATAAREPRESENTEDBYTHEINDUSTRYSECTOR
IN &IGURE SOME CLEAR TRENDS EMERGE 4HE CHEMICAL ANDOILCOMPANIESMAINLYUSEKINETICS FORPROCESSDEVELOPMENTANDPROCESSOPTIMIZATIONANDTOASMALLEREXTENTFORCATALYSTDEVELOPMENT !S MIGHT BE EXPECTED CATALYST PRODUCERSFOCUSONCATALYSTDEVELOPMENTWHILEENGINEERINGCOMPANIESCONCENTRATE ON PROCESS DEVELOPMENT 3OME MECHANISTICRESEARCHISDONEBYTHECATALYSTPRODUCERSANDTHECHEMICALCOMPANIESBUTTHISDOESNOTEXCEEDOFTHEUTILIZATIONOFKINETICDATA
PROCESSDEVELOPMENT
PROCESSOPTIMIZATION
OTHER
CATALYSTDEVELOPMENT
MECHANISTICRESEARCH
&IGURE5TILIZATIONOFKINETICDATAININDUSTRY
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
4HE LATERPARTSOF THE SURVEY FOCUSEDONHOW INDUSTRYMEASURESITSDATAANDTHETYPESOFMODELSITUSESTOREPRESENTTHEKINETICS"EFORECONSIDERINGTHESEASPECTSITISTIMELYTOCONSIDERTHEBACKGROUNDTOKINETICTHEORYTHEMEASUREMENTOFKINETICDATAANDREACTIONKINETICMODELING
PROCESSOPTIMIZATION
PROCESSOPTIMIZATION
OTHER
OTHER
CATALYSTDEVELOPMENT
CATALYSTDEVELOPMENT
MECHANISTICRESEARCH
MECHANISTICRESEARCH
ACHEMICALCOMPANIES
BOILCOMPANIES
CCATALYSTCOMPANIES
PROCESSDEVELOPMENT
PROCESSDEVELOPMENT
PROCESSOPTIMIZATION
OTHER
CATALYSTDEVELOPMENT
MECHANISTICRESEARCH
PROCESSDEVELOPMENT
DENGINEERINGCOMPANIES
PROCESSOPTIMIZATIONOTHER
CATALYSTDEVELOPMENT
MECHANISTICRESEARCH
PROCESSDEVELOPMENT
&IGURE5TILIZATIONOFKINETICDATAFORDIFFERENTCHEMICALINDUSTRYSECTORS
4YPESOFKINETICMODELS2ESEARCHERSINCATALYSISKINETICSANDREACTORENGINEERINGAREGENERALLYWELLINFORMEDABOUTTHEGENERALTHEORYCONCERNINGREACTIONKINETICS!TTHESIMPLERLEVELWECANDISTINGUISHTWOCOMMONBASICAPPROACHESTOREACTIONMODELINGSUMMARIZEDIN4ABLE
0OWERLAWKINETICS&ORTHEIRREVERSIBLEGASPHASEREACTION!"m#THERATEOFREACTIONMAYBEREPRESENTEDBYANEXPRESSIONOFTHEFORMRKP!NP"M
WHEREP!ANDP"ARETHEPARTIALPRESSURESOFREACTANTS!AND"RESPECTIVELYANDKISTHERATECONSTANT4HEEXPONENTSNANDMARETERMEDTHEhORDERSOFREACTIONv)TMAYSEEMNATURALTOASSUMEARATEEXPRESSIONRK;!=;"=WHERE THE ORDERS OF REACTION MATCH THE STOICHIOMETRICCOEFlCIENTS AND THUS A SECOND ORDER REACTION FOR THISEXAMPLElRSTORDERINEACHREACTANT4HISISNOTNECESSARILYTHECASE!REACTIONMECHANISMCANINCORPORATEANUMBEROFSUBREACTIONSANDTHEPOWERLAWAPPROACHDISGUISESTHIS4HEREALRATEEXPRESSIONWILLREmECTTHEKINETICSOFTHEPOTENTIALLYSLOWESTORRATEDETERMININGSTEP4HEREACTIONORDERSHOULDTHEREFOREALWAYSBEDETERMINEDEXPERIMENTALLY4HEPOWERLAWEXPRESSIONISCOMMONLYUSEDBECAUSEOF
ITSSIMPLICITYANDITSPROPERTYTHATITFREQUENTLYlTSTHEDATARATHER EASILY 4HE ANCIENT WONDER OF RECONCILING DATA BYPLOTTING THEM ON LOGLOG GRAPH PAPER HAS NOT FADED EVENIN THIS HIGH TECHNOLOGY AGE )N CATALYSIS THIS EXPRESSIONISNOTHOWEVERBASEDONASOUNDPHYSICOCHEMICALTHEORYANDTHEREFORETHERELIABILITYOFTHERESULTSANDPREDICTIONSISLIMITEDTOTHERANGEOFCONDITIONSUNDERWHICHTHEKINETICEXPERIMENTSWEREPERFORMED
%FFECTOFEQUILIBRIUM! GIVEN REACTION SUCH AS! "m # CAN OFTEN OCCUR INBOTHDIRECTIONSVIZ!"#7HICHDIRECTIONPREVAILSAT A GIVEN CONDITION DEPENDS ON THE THERMODYNAMICS%QUILIBRIUM CORRESPONDS TO THE MINIMIZATION OF 'IBBSFREEENERGY)FNOBARRIEREGACTIVATIONENERGYEXISTSTHENASYSTEMWILLALWAYSMOVETOWARDSEQUILIBRIUM4WO REACTIONS CAN BE DElNED EACH WITH ITS OWN RATE
EQUATION!SSUMINGFORTHESAKEOFSIMPLICITYAlRSTORDERDEPENDENCYFOREACHCOMPONENT
0OWERLAWEXPRESSION
RKEXPP!P" ,ANGMUIR(INSHELWOOD(OUGEN7ATSONTYPEEXPRESSION
R
4YPESOFCOMMONLYUSEDRATEEXPRESSIONSFORTHEREACTION!G"Gm#G
4ABLE
N M
%!24
KR+!ADSP!+"ADSP"+!ADSP!+"ADSP"+#ADSP#
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
! KINETIC MODEL WAS DERIVED FOR AN EFmUENT TREATMENT PROCESSTHE CATALYTIC DECOMPOSITION OF THE POLLUTANT 4HIS WAS BASEDON EXPERIMENTAL DATA WHERE THE REACTION WAS OBSERVED TO BEIRREVERSIBLE AND lRSTORDER IN THE REACTANT 4HE DATA WERE ONLYMEASUREDOVER A NARROW TEMPERATURE RANGE THAT BELIEVED TO BETHEPROBABLEOPERATINGDOMAINFORTHEINDUSTRIALSCALEREACTOR4HEEXPRESSIONFORTHElRSTORDERRATECONSTANTTHATWASUSEDTOlTTHEEXTENSIVEDATASETWAS
(EREITCANBESEENTHATTHE!RRHENIUSTERM;!%A4=HASBEENSUPPLEMENTEDBYASECONDTEMPERATURETERMINTENDEDTOIMPROVETHESTATISTICALlTFORATOTALOFFOURlTTINGPARAMETERSFORESSENTIALLYONEVARIABLE4HISWORKEDWELLUNTILAPLANTOPERATINGONEOFTHESE
4HROUGH OVERPARAMETERIZATION THE ABILITY OF THE MODEL TO EXTRAPOLATE BEYOND THEINTERMEZZO
REACTORSWANTED TO INCREASE THROUGHPUT AND PROPOSED INCREASINGTHEOPERATINGTEMPERATURETOACHIEVETHIS4HERESULTOBTAINEDWITHTHE ABOVE MODEL IS SHOWN IN &IGURE )T WAS SURPRISING THAT ATHIGHERTEMPERATURESTHECONVERSIONWASESSENTIALLYINDEPENDENTOFTEMPERATUREANDEVENTUALLYEXPERIMENTALDATASHOWEDTHATTHISWASNOTTRUE4HEPROBLEMLAYINTHEADDITIONALTEMPERATURETERMINTHEKINETICEXPRESSION)N THE lRST INSTANCE THIS ADDITIONAL TEMPERATURE TERM WAS SIMPLYREMOVED AND A SIMPLE !RRHENIUSTYPE RELATIONSHIP WAS lTTEDTHROUGH THE DATA 4HISMODIlED EXPRESSION WAS FAR MORE ABLE TOPREDICT PERFORMANCE OUTSIDE THE EXPERIMENTAL TEMPERATURE RANGE!COMPARISONOF THEPREDICTEDDESIGNCATALYSTVOLUMES TOACHIEVEAGIVENCONVERSION ISSHOWN IN&IGURE4HEREVISEDMODELMOREACCURATELY PREDICTS THE EXPECTED TREND WHICHWAS ALSO OBSERVEDEXPERIMENTALLY
LNK!%A#4
4#
#
FORWARDREACTION !"m# RATE RFKF;!=;"=BACKREACTION #m!" RATE RBKB;#=4HESEARENOTINDEPENDENTEXCEPTAThVERYLOWvCONVERSIONSWHEREEQUILIBRIUMISNOTAPPROACHED!TOTHERCONDITIONSTHENETFORWARDREACTIONRATEFOR!"#ISGIVENBYRRFRBKF;!=;"=KB;#=4HUS EQUILIBRIUM OCCURS WHEN THE FORWARD AND REVERSEREACTION RATESAREEQUAL RF RB ANDHENCENONET REACTIONOCCURS&ORTHEREACTION!"#THEEQUILIBRIUMCONSTANTISGIVENBY+EQ[;#=;!=;"=] EQ)TMAYTHUSBESHOWNTHAT+EQKBKF4HENETFORWARDREACTIONRATEISTHEREFOREGIVENBYRKF[;!=;"=n;#=+EQ]
%FFECTOFTEMPERATURE4HEVALUEOFTHEEQUILIBRIUMCONSTANTISASTRONGFUNCTIONOFTEMPERATURE&ORENDOTHERMICREACTIONS+EQANDEQUILIBRIUMCONVERSIONINCREASEWITHTEMPERATUREWHILEFOREXOTHERMICREACTIONS THE CONVERSE IS TRUE4HIS STRONGDEPENDENCEONTEMPERATUREISALSOPREVALENTINREACTIONRATECONSTANTSANDSO THE NEXT LEVEL OF DETAIL TO BE INTRODUCED MAY BE THETEMPERATUREDEPENDENCEOFTHERATEOFREACTION4HISISMOSTCOMMONLYDONEUSINGAN!RRHENIUSTYPEEXPRESSIONK!EXP%A24(ERE%AISKNOWNASTHEh!CTIVATION%NERGYv2EACTION
RATE CONSTANTS AND EQUILIBRIUM CONSTANTS COMMONLY SHOWAGREEMENTWITHTHISRELATIONSHIP4HISRELATIONSHIPISSHOWNIN&IGUREWITHCURVESPLOTTEDFORDIFFERENTACTIVATIONENERGIESALLBASEDAROUNDASIMILARRATECONSTANTAT+)TCANBESEENTHATTHEVALUEOF%AHASAVERYSTRONGINmUENCEONTHERATEDEPENDENCYONTEMPERATURE4HISISIMPORTANTINTHEDESIGNOFCHEMICALREACTORS
4HE ACTIVATION ENERGY IS A COMMONLY CITED PARAMETERANDITSVALUEOFCOURSETELLSTHEREACTIONENGINEERHOWDEPENDENTTHEREACTIONRATEISONTEMPERATURE6ALUESOFnK*MOL ARE TYPICAL FORMANY CATALYZED REACTIONS#OMBUSTIONANDMANYOTHERNONEQUILIBRIUMLIMITEDREACTIONSMAYHAVEMUCHHIGHERVALUESK*MOLFOREXAMPLE!RULEOFTHUMBOFTENQUOTEDISTHATTHERATEOFAREACTIONWILLDOUBLEFOREVERY+RISEINTHEREACTIONTEMPERATURE4HISCORRESPONDSTOANACTIVATIONENERGYINTHERANGE nK*MOLATTYPICALREACTIONTEMPERATURES4HUSTHEREACTIONENGINEER
EXPERIMANTALDOMAINISSEVERELYCOMPROMISEDCATALYTICDECOMPOSITIONREACTION
4EMPERATURE#
RELATIVEREACTIONRATECONSTANT ACTIVATIONENERGYK*MOL
INCREASING%!
&IGURE2EACTIONRATESTRONGLYDEPENDSONTEMPERATURE
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
,ANGMUIRn(INSHELWOODn(OUGENn7ATSONKINETICS)NORDERTOOBTAINAMOREMEANINGFULKINETICEXPRESSIONITISNECESSARYTOSTARTINTRODUCINGPHYSICALANDCHEMICALPROCESSESOCCURRING AT THE CATALYST SURFACE INTO THE MATHEMATICALREPRESENTATION/NEOFTHESIMPLESTMETHODSANDMOSTPOPULARAPPROACHESTOTHISISVIATHE,ANGMUIRn(INSHELWOODMODELAND THE ASSOCIATED ,ANGMUIRn(INSHELWOODn(OUGENn7ATSON,((7TYPEKINETICEXPRESSION ! ,ANGMUIRn(INSHELWOODn(OUGENn7ATSON TYPE EXPRESSIONISDERIVEDUSINGTHEASSUMPTIONSTHATTHEADSORPTIONOF ALL COMPONENTS CAN BE DESCRIBED BY THE ,ANGMUIRn(INSHELWOODMODEL AND THAT ONE SURFACE REACTION IS RATEDETERMINING4HE SHAPEOF THE RATEEXPRESSIONDEPENDSONTHE CHOICE OF THE RATEDETERMINING STEP ! STUDY OF THETHEORETICAL BACKGROUND CAN HELP THE RESEARCHER TO lNDTHE MOST PROBABLE RATEDETERMINING STEP AND TO OBTAINPROPER ESTIMATES OF THE KINETIC PARAMETERS WHICH CAN BEUSED AS INITIAL ESTIMATES FOR THE PARAMETER lTTING 4HESEINITIAL ESTIMATES SHOULD ALSO BE USED TO CHECK AFTERWARDSIF THE PARAMETERS FOUND BY THE lTTING ROUTINE ARE INPHYSICOCHEMICALLYACCEPTABLERANGES4HISMODEL THUSMAKES ASSUMPTIONS ABOUT ADSORPTION
ANDDESORPTIONONTHECATALYST SURFACE!T ITS SIMPLEST THE,ANGMUIRn(INSHELWOOD MODEL ASSUMES THAT ALL REACTANTSADSORBONTOCATALYST SURFACESAND THAT REACTIONOCCURSASASURFACEPROCESS4HISYIELDSAKINETICEXPRESSIONOFTHEFORM
RATEt
4HROUGH OVERPARAMETERIZATION THE ABILITY OF THE MODEL TO EXTRAPOLATE BEYOND THE
CAN IMMEDIATELY START JUDGING THE SUSCEPTIBILITY OF A REACTION TO RUNAWAY SELECTIVITY LOSS OR EFFECTIVE EXTINCTION IFTHETEMPERATUREGOESOUTSIDETHEIDEALOPERATINGWINDOW!SIDEREACTIONWITHFOREXAMPLEANACTIVATIONENERGYOFK*MOLTELLSTHEDESIGNCHEMICALENGINEERTHATIFTHETEMPERATUREISALLOWEDTORISETHESELECTIVITYWILLFALLRAPIDLY&URTHERMOREUNLESSTHATSIDEREACTIONISCONSTRAINEDTHENTHISREPRESENTSARUNAWAYPOTENTIALANDTHATMUSTBECONSIDEREDINTHEREACTORANDCONTROLSYSTEMDESIGN'IVEN THEPHYSICAL INTERPRETATIONS THATCANBEATTACHED
TO THE ACTIVATION ENERGY IT CAN EASILY BE SEEN WHY THISAPPROACH IS POPULAR )T IS STILL HOWEVER CONSTRAINED BYTHE mAWS OF THE EMPIRICAL POWER LAW APPROACH "ECAUSEOF THE LACK OF PHYSICOCHEMICAL RELEVANCE THE ACCURACY OFTHE KINETIC EXPRESSION AND THE APPLICATIONOF THEMODEL ISRESTRICTEDTOTHEEXPERIMENTALCONDITIONSUNDERWHICHITWASDETERMINED&OREXAMPLEITMAYBETEMPTINGTOIMPROVEATEMPERATURE
lT BY INCREASING THE NUMBER OF TEMPERATURE TERMS IN THEEXPRESSION 4HIS IS NOT ADVISABLE SEE )NTERMEZZO "YSTATISTICALLYIMPROVINGTHElTWITHATERMTHATHASNOPHYSICALMEANING THEAPPLICATIONOF THEMODEL IS TIGHTLY RESTRICTEDTOTHEEXPERIMENTALRANGEWHICHINTHISCASEPREVENTEDUSEOFTHEORIGINALMODELTOEVALUATEAREACTOROPERATINGATANINCREASED TEMPERATURE4HIS EMPHASIZES THE IMPORTANCEOFNOTINCLUDINGTOOMANYPARAMETERSINAMODELPARTICULARLYWITH THOSE PARAMETERS THAT DO NOT HAVE ANY PHYSICALSIGNIlCANCE )T IS ALWAYS WORTH REMEMBERING THAT WITHENOUGHlTTINGPARAMETERSAMODELCANBEFORCEDTOlTANYDATASETBUTJUSTBECAUSETHEREISAGOODSTATISTICALlTDOESNECESSARILYNOTMEANTHATITISAGOODMODEL
&IGURE0REDICTEDEXITCONCENTRATIONUSING2ATEEXPRESSION &IGURE0REDICTEDCATALYSTVOLUMETOACHIEVEAGIVENCONVERSION
TEMPERATURE
LOGEXITCONCENTRATION
TEMPERATURE
DESIGNCATALYSTVOLUME
NEWMODEL
OLDMODEL
EXPERIMANTALDOMAINISSEVERELYCOMPROMISEDCATALYTICDECOMPOSITIONREACTION
3PECIlCALLYBYUSINGATEMPERATURETERMINADDITIONTOTHE!RRHENIUSRELATIONSHIP THElTWITHIN THEEXPERIMENTAL DOMAINWAS IMPROVED(OWEVER THE MODEL WAS ENTIRELY USELESS WHEN ASKED TO PREDICTPERFORMANCEOUTSIDE THEDATA TEMPERATURE RANGE4HEMODELWASIMPROVEDINTHElRSTINSTANCESIMPLYBYSTRIPPINGOUTTHEREDUNDANTSTATISTICALTERM
%VENTUALLY A NEW MODEL WAS DERIVED BASED ON FURTHEREXPERIMENTATION USING A ,ANGMUIR(INSHELWOOD APPROACH TOACCOUNT FOR THE INHIBITING EFFECT OF THE COMPETITIVE ADSORPTIONOF A SECOND NONREACTING COMPONENT PRESENT IN THE STREAMAND PROVIDEDWITH ONLY THE!RRHENIUSTYPE TERM TO DESCRIBE THETEMPERATUREDEPENDENCE
KINETICFACTORDRIVINGFORCEADSORPTIONTERMN
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
4HENUMERATORISABASICREACTIONRATEEQUATIONWHILETHEDENOMINATORACCOUNTS FOR THEEFFECTSOF THE SORPTIVE STEPS&OR EXAMPLE FOR A REACTION! "m # NOT EQUILIBRIUMLIMITEDTHERATEOFFORMATIONOF#ISGIVENBYTHE,((7TYPEEXPRESSIONR
WHEREKRISTHERATECONSTANTFORTHESURFACEREACTIONAND+!ADS+"ADSAND+#ADSARETHEADSORPTIONCOEFlCIENTSFORTHERESPECTIVESPECIES3TRICTLY THE ,ANGMUIRn(INSHELWOODMODEL ASSUMES A
HOMOGENEOUSCATALYSTSURFACE.ONHOMOGENEITYANDPOTENTIAL ADSORPTION ONTO DIFFERENT ACTIVE SITES ARE EFFECTIVELYACCOUNTEDFORBYDIFFERENCESINTHEVALUESOF+!ADSAND+"ADSORINTHEFORMOFTHEADSORPTIONTERM4HISISINFACTONEOFTHESTRENGTHSOFTHE,((7MATHEMATICALEXPRESSION)NTHEDATAlTTINGATITSSIMPLESTTHEPLOTISEFFECTIVELYOFYVERSUS
WHERE THE SIMPLE POWER LAW PLOT IS IMPROVED BY THEDENOMINATORTHATALLOWSADEGREEOFINDEPENDENTCURVATURE4HE ,((7TYPE EXPRESSIONS HAVE BEEN FOUND TO lT AWIDERANGEOFREACTIONS7HILETHE,ANGMUIRn(INSHELWOODKINETICMODELISAGOODONEITSREALSTRENGTHLIESINITSABILITY
TODESCRIBEMIXTURESBASEDONSINGLECOMPONENTPARAMETERSANDTHEROBUSTNESSOFTHEDERIVEDMATHEMATICALEXPRESSION4HESECOMMENTSMAYAPPEARTOSUGGESTTHATTHEMODEL
WORKS PRIMARILY BECAUSE OF ITSMATHEMATICAL FORM4HIS ISNOTTRUE4HEUNDERLYINGCONCEPTOFCOMPETITIVEADSORPTIONEQUILIBRIA ON A lNITE NUMBER OF ACTIVE SITES IMPINGING ONTHEREACTIONKINETICSISVERYIMPORTANT-ANYSYSTEMSEXISTWHERETHEKINETICSAREINFACTSTRONGLYAFFECTEDBYADSORPTIONPHENOMENA4HEMOSTOBVIOUSEFFECTISWHEREAREACTANTISSTRONGLYADSORBEDTOTHEEXTENTTHATITISALWAYSAVAILABLEINEXCESSONTHECATALYSTSURFACE4HEREACTIONRATETHUSBECOMESINDEPENDENTOFITSGASPHASECONCENTRATIONORZEROORDER!NEXAMPLEOFTHISISSHOWNIN)NTERMEZZOWHERESTRONGLYADSORBING SYSTEMS SHOWING ZERO HIGH CONCENTRATION LOWCONVERSIONORlRSTORDERLOWCONCENTRATIONHIGHCONVERSIONDEPENDENCIES ARE DISCUSSED !N IMPORTANT POINT IS HOWTHISKINETICBEHAVIORINmUENCESTHESELECTIONOFTHEREACTORTYPETHATWOULDBE IDEAL FORCARRYINGOUTTHEREACTIONATACOMMERCIALSCALE
+R+!!DSP!+"!DSP"+!ADSP!+"!DSP"+#!DSP#
BXQAXP
:EROORDERKINETICSFORASTRONGLYADSORBINGREACTANTTRANSFORMTOlRSTORDERINTERMEZZO
"ENZALDEHYDE WAS SELECTIVELY HYDROGENATED TO BENZYL ALCOHOLIN THE LIQUID PHASE USING MOLECULAR HYDROGEN OVER A CATALYSTCONSISTING OF WT.I ON A CORDIERITEMONOLITH COATEDWITH WT!L/
&IGURESHOWSATYPICALRESULTFORTHECONCENTRATIONASAFUNCTIONOFTHERESIDENCETIMEINABATCHRECYCLEREACTOR;I= )NTHElRSTPARTTHE SELECTIVITY TOWARDS BENZYL ALCOHOL IS VERY HIGH 7HEN MOSTBENZALDEHYDEHASBEENCONVERTED THERATEOFHYDROGENOLYSISOFBENZYL ALCOHOL TO TOLUENE AND WATER BECOMES SUBSTANTIAL 4HE
LINEAR DECREASE IN A LARGE PART OF THE EXPERIMENT SHOWS THAT THEAPPARENTREACTIONORDERFORBENZALDEHYDEISZERO
+INETICMODELING! SIMPLE ,ANGMUIRn(INSHELWOODMODEL IS ABLE TO DESCRIBE THESETYPICALEXPERIMENTALRESULTS5NDERTHEASSUMPTIONSTHATv BENZALDEHYDEANDHYDROGENADSORBONDIFFERENTSITESv THESURFACEREACTIONISRATEDETERMININGv NEARLYALLACTIVESITESAREOCCUPIED4HEFOLLOWINGSIMPLIlEDEXPRESSIONISOBTAINEDFORTHEREACTIONRATEOFBENZALDEHYDERANDTHEFORMATIONRATEOFTOLUENER RAK RAKWHERE K AND K INCORPORATE THE CATALYST CONCENTRATION AND THEHYDROGEN PRESSURE DEPENDENCY TERM + REPRESENTS THE RATIO OFTHEADSORPTIONCONSTANTSOFBENZYLALCOHOLANDBENZALDEHYDEANDA ACCOUNTS FOR CATALYST DEACTIVATION 4HE ADSORPTION OF TOLUENE ISNEGLIGIBLE4HE lTTED PARAMETER VALUES SHOWN IN 4ABLE INDICATE THAT THEADSORPTIONOFBENZALDEHYDEISSTRONGERTHANTHATOFBENZYLALCOHOL4HISEXPLAINSTHEAPPARENTREACTIONORDEROFZEROFORBENZALDEHYDEATHIGHCONCENTRATIONS!THIGHCONVERSIONS THE TERM+#BALC IN THEDENOMINATOR BECOMES LARGER THAN THE TERM #BALD AND CAUSES THE
BENZALDEHYDE BENZYLALCOHOL TOLUENE
KINETICSATHIGHCONVERSIONDUETOADSORPTIONOFTHEPRODUCT"ENZALDEHYDEHYDROGENATION
4ABLE+INETICPARAMETERSESTIMATED
+INETICPARAMETERSESTIMATED
K;MOLMMONOLITHS= K;MOLMMONOLITHS= +;=
#BALD#BALD+#BALC
#BALC#BALD+#BALC
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
4HEROLEOFMASSTRANSFER
)NTRINSICAPPARENTANDEXTRINSICKINETICS!S NOTED IN THE INTRODUCTORY SECTION AN IMPORTANT PARTOFTHECATALYTICREACTIONPROCESS IS THEMASSTRANSFEROFTHEREACTANT TO THE CATALYST SITES 4HIS INVOLVES NOT ONLY THETRANSFERWITHINTHEBULKmUIDPHASEBUTALSOTHETRANSPORTWITHINTHEPOROUSSTRUCTUREOFTHECATALYSTPELLETORPARTICLE4HEACTUALTRANSPORTINTHEmUIDPHASECANBESLOWANDTHUSTHEOBSERVEDREACTIONRATEISINFACTAFFECTEDBYANDMAYINDEEDBEDOMINATEDBYTHEMASSTRANSFERPROCESS4YPICALEXAMPLESHEREARECATALYTICREACTIONSOCCURRINGINTHELIQUIDPHASEANDCATALYZEDOXIDATIONPROCESSES)TMAY NOT BE SIMPLE EXPERIMENTALLY TO DECOUPLE THE
TRANSPORT AND KINETIC PROCESSES !FTER ALL DIFFUSION ANDKINETIC RATEFORAlRSTORDERREACTIONHAVETHEEXACT SAMEDEPENDENCYONCONCENTRATIONlRSTORDER$IFFUSIONANDMASS TRANSFERHOWEVERHAVEAMARKEDLY LOWERDEPENDENCYONTEMPERATUREANDTHEREFOREMASSTRANSFERINHIBITEDRATESARE CHARACTERIZED BY AN ARTIlCIALLY DEPRESSED VALUE OF THEACTIVATIONENERGYANDTHAT THE!RRHENIUSPLOTMAYYIELDACURVERATHERTHANASTRAIGHTLINE4HEMASS TRANSFER IN A REACTOR OCCURS ON SEVERAL DIFFERENTLENGTHSCALES
4URBULENTMASSTRANSFERFROMTHEBULKmUIDTONEARTHECATALYSTSURFACEnMM
,AMINARMASSTRANSFERINTHEmUIDBOUNDARYLAYERORMASSTRANSFERlLMABOUTTHECATALYSTPARTICLEnMM
$IFFUSION WITHIN THE POROUS STRUCTURE OF THE CATALYSTnMM
!SPECTS AND ABOVE ARE CONVENIENTLY LUMPEDUSING THEWELLKNOWN7HITMANlLMTHEORYASSEENIN&IGUREWHICHASSUMESTOTALMIXINGZEROCONCENTRATIONGRADIENTSINTHEBULK mUID AND A LAMINAR lLM WHOSE RESISTANCE TO MASSTRANSFERISCHARACTERIZEDBYAMASSTRANSFERCOEFlCIENTWHICHISACTUALLYACONDUCTANCE4HISRATEOFMASSTRANSFERISLARGELYDEPENDENT ON THE mUID PROPERTIES DENSITY VISCOSITY THEmUIDVELOCITYRELATIVETOTHESOLIDANDTHESIZEOFTHECHANNELIN WHICH THE mUID IS mOWING 4HERE ARE MANY EMPIRICALCORRELATIONSINTHELITERATUREFORMASSTRANSFERCOEFlCIENTS;=AND MANY ARE DERIVED IN GEOMETRIES RELEVANT TO CATALYTICREACTORS!FURTHERCOMPLICATIONCANARISEINLIQUIDPHASEREACTIONS
INVOLVING A GASEOUS REACTANT SUCH AS HYDROGENATION ANDOXIDATIONUSINGMOLECULARHYDROGENANDOXYGENRESPECTIVELY#OMMERCIALLY THESE REACTIONS ARE TYPICALLY CARRIED OUT INSPARGED STIRRED TANKSOR TRICKLEBEDS )N THIS CASE THERE ISTHEADDEDSTEPOFTHEGASEOUSREACTANTTRANSFERRINGINTOTHE
:EROORDERKINETICSFORASTRONGLYADSORBINGREACTANTTRANSFORMTOlRSTORDER
&IGURE#ONCENTRATIONSASAFUNCTIONOFTIMEDURINGBENZALDEHYDEHYDROGENATIONATWTBENZALDEHYDEAT+AND-0A;I=
TIMES
CONCENTRATIONMOLM
BENZALDEHYDEBENZYLALCOHOL
TOLUENE
APPARENT REACTIONORDER FORBENZALDEHYDE TO INCREASE TOONE4HISWASCONlRMEDBYEXPERIMENTSWITH LOWER INTIALCONCENTRATION )T ISCLEAR THAT FOR ESTIMATION OF THE PARAMETERS THE MAIN PART OF THEMEASUREMENTSHOULDBECARRIEDOUTATLOWCONCENTRATION7HATARETHECONSEQUENCESOFTHETRANSFORMATIONOFTHINTOSTORDERKINETICS&ORZEROORDERKINETICSTHEREACTORTYPEISNOTCRITICALANDACONTINUOUSLYSTIRREDTANKREACTOR#342ISSUITABLEFORALARGEPART
KINETICSATHIGHCONVERSIONDUETOADSORPTIONOFTHEPRODUCT"ENZALDEHYDEHYDROGENATION
OFTHECONVERSION)NVIEWOFTHETRANSFORMATIONINTOSTORDERANDTHEUNDESIREDCONSECUTIVE REACTIONOFBENZYLALCOHOL TO TOLUENEHOWEVERA#342ISNOTASUITABLEREACTORANDAPLUGmOWREACTORISTOBEPREFERREDINTHElNALCONVERSIONSTAGEASAhlNISHINGREACTORv
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
7HENSIMPLIFYINGAMODELBY
LIQUID PHASE EN ROUTE TO THE CATALYST SURFACE 4HIS OPENSUPANADDITIONALAREAOFMASSTRANSPORTINCHEMICALREACTORSTHATDEPENDSCRITICALLYONTHEINTERDISPERSIONOFTHEPHASESAND THE REACTOR HYDRODYNAMICS 4HIS IS BEYOND THE SCOPEOF THE PRESENT PAPER BUT HAS BEEN REVIEWED EXTENSIVELYELSEWHERE 3EE ;= FOR SOME RECOMMENDED REFERENCES4HE MASS TRANSPORT WITHIN THE CATALYST PELLET MAY
BE HARDER TO CHARACTERIZE 4HE EFFECT IS EASILY OBSERVEDEXPERIMENTALLYBYVARYING THESIZEOF THECATALYSTPARTICLE4RADITIONALLY THISHASBEENTREATEDMATHEMATICALLYUSINGAhPELLET EFFECTIVENESSv BASED ON THE 4HIELE MODULUS;= !TYPICAL PLOT OF PELLET EFFECTIVENESS AS A FUNCTION OF PELLETSIZEFORAlRSTORDERREACTIONISSHOWNIN&IGURE"ECAUSETECHNIQUESANDMODELS FORCHARACTERIZINGPOROUSNETWORKSANDMASS TRANSFER STILL DO NOT LEAD TO RELIABLE PREDICTIONSTHERE IS A TENDENCY TO MEASURE KINETICS USING THE SAME
FLUIDFLOWVELOCITYPROFILE
CONCENTRATIONPROFILES
7HITMANACTUAL
7HITMANFILMTHICKNESS
CONCENTRATIONINSOLIDPHASE
SOLIDSURFACEORINTERFACE
)NGASLIQUIDSYSTEMSAFILMEXISTSONBOTHSIDESOFTHEINTERFACE
&IGURE7HITMANlLMTHEORYFORINTERFACIALMASSTRANSFER
$IFFUSIVITY%MSEC2EACTIONRATECONSTANTSEC
PELLETDIAMETERMM
EFFECTIVENESS
&IGURE0ELLETEFFECTIVENESSISAFUNCTIONOFPELLETDIAMETER
LUMPINGBECAREFULNOTTOGOTOOFARNDORDEREFFECTSIN($3INTERMEZZO
)N HYDRODESULPHURIZATION ($3 OF VACUUM GAS OIL IT IS WELLDOCUMENTEDTHATREALFEEDSTOCKSEGGASOILFOLLOWANAPPARENTSECONDORDER BEHAVIOR IN THE AMOUNT OF SULPHUR CONTAININGCOMPONENTSSEE&IGURESAND(OWCANTHISBERATIONALIZED)T ISQUITESTRANGE TOlNDASECONDORDERBEHAVIORWHILE THERE ISNOT ANY SUGGESTION OF A BIMOLECULAR REACTION STEP BETWEEN TWOSULPHURCONTAINING MOLECULES -OREOVER THE SULPHUR PRODUCT IS(3ONLY4HE EXPLANATION LIES IN THE COMPLEX COMPOSITION OF THE REALFEEDSTOCK COVERING THIOETHERS THIOPHENE BENZOTHIOPHENE DIBENZOTHIOPHENEANDSUBSTITUTEDDIBENZOTHIOPHENESSEE&IGURESAND4HEYALLHAVEDIFFERENTREACTIVITIESOVERACATALYSTIN($3RESULTINGINTHECOMPOSITECONTRIBUTIONOFALLTHESEMOLECULESINTHEOVERALLKINETICBEHAVIOUR
BEDLENGTH
C
CONCENTRATION
CONVERSION
,(36H
33WT
GASOIL#O-OALUMINATRICKLEFLOW,M
&IGURE %XPERIMENTAL RESULTS FOR HYDRODESULFURIZATION IN A lXED BEDREACTOR;IIIII=
&IGURE&ITTINGRESULTSFORREACTIONORDER
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
7HENSIMPLIFYINGAMODELBY LUMPINGBECAREFULNOTTOGOTOOFARNDORDEREFFECTSIN($3
3IMULATEDDISTILLATIONBP
SPACETIMEKGSMOL
CONCENTRATIONMOLM ###
#
##
NDORDERREACTIONDATA
4ABLE
+INETICSOFTHESECONDORDERREACTIONUSEDANDTHElTTINGRESULTSFORTHETHREElRSTORDERREACTIONS
SECONDORDERREACTION
KMMOLS CMOLM
THREElRSTORDERREACTIONS
KS CMOLM
KS CMOLM
KS CMOLM
3
3
32 2
3
23 3
2232 THIOETHERS
THIOPHENE
BENZOTHIOPHENE
DIBENZOTHIOPHENE
SUBSTITUTEDDIBENZOTHIOPHENE
&IGURE#OMPOSITIONOFOILFRACTIONSINVACUUMGASOIL
)TWASDEMONSTRATEDBYTHESUMMATIONOFTHREElRSTORDERREACTIONSIN A PLUGmOW REACTOR THAT THE COMPOSITE CONVERSION PROlLE AS AFUNCTIONOFSPACE TIMECANBEDESCRIBEDBYSECONDORDERKINETICSOVERABROADRANGEOFSPACETIMES;IV=4HISISILLUSTRATEDIN&IGUREAND4ABLE0ROBLEMSWILLARISEIF THIS ISNOTRECOGNIZEDANDAREACTORFORDEEP($3 IS DIMENSIONED ON THE BASIS OF THE SECONDORDER KINETICS4HIS WILL EVENTUALLY LEAD TO REQUIRED REACTOR VOLUMES THAT ARE TOOLARGEWHILEAPROPERlRSTORDERDESCRIPTION FOR THEMOST REFRACTORYCOMPONENTSWOULDYIELDTHEPROPERANSWER)N THIS CASE THREE LUMPS ARE SUFlCIENT TO DESCIBE THE KINETICS OFTHE MIXTURE OF REACTANTS ACCURATELY !N IMPORTANT QUESTION TO BEANSWEREDINCOMPARABLETYPESOFPROBLEMSISWHICHANDHOWMANYLUMPEDCOMPONENTSSHOULDBEUSED
&IGURE3ULPHURCOMPOUNDSPRESENTINVACUUMGASOIL
&IGURE 3UCCESSFUL lTOFASIMULATEDSECONDORDERPROlLEBYMEANSOFTHE SUM OF THREE lRSTORDER REACTIONS DIFFERING BY ABOUT A FACTOR OF SEVEN INREACTIVITY
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
CATALYST PELLET SIZE AS WILL BE USED IN THE OPERATING PLANT)NMANYCASESTHISLEADSTOAKINETICMODELTHATINHERENTLYINCLUDESINTRAPARTICLEMASSTRANSPORTRATEEFFECTS#LEARLYITISESSENTIALTODISTINGUISHBETWEENMODELSTHAT
INCLUDEONLYCHEMICALEFFECTSANDTHOSETHATINCLUDEVARYINGDEGREES OFMASS TRANSFER2EGARDINGMASS TRANSFERWE CANDElNETHREELEVELSOFAMODELA )NTRINSICWHEREALLTHEEFFECTSOFMASSTRANSPORTHAVEBEENSTRIPPEDOUTANDTHEMODELREPRESENTSONLYTHESURFACEPROCESSES
B !PPARENTWHEREANYTRANSPORTLIMITATIONSINTERNALTOTHECATALYSTSTRUCTUREAREINCLUDEDINTHEMODEL-EASURINGKINETICSONAFULLSIZEDPELLET ISANEXAMPLEOFTHIS7HILEMAYBENOTSTRICTLYCORRECTFROMASCIENTIlCPOINTOFVIEWITISNONETHELESSPRAGMATIC
C %XTRINSICWHERENOATTEMPTHASBEENMADETODECOUPLE THE GROSS MASS TRANSFER FROM THE REAL OR INTRINSICKINETICS4HEMODELMAYTHEREFOREINCLUDEEFFECTSRELATEDTOGROSSMIXINGTIMESANDDIFFUSIONTHROUGHTHELAMINARlLMADJACENTTOTHECATALYSTSURFACE/NE lNAL POINT HERE IS THAT IN DEVELOPING AN INTRINSIC
MODELITBEHOVESTHEEXPERIMENTERTOVERIFYTHEABSENCEOFTRANSPORTEFFECT4HEREISMUCHGUIDANCEINTHELITERATUREONHOWTODOTHIS;=)TISCLEARHOWEVERTHATTHISISNOTALWAYSDONE
-ODELINGMORECOMPLEXSYSTEMS-ANY REAL SYSTEMS ARE COMPLEX INVOLVING MULTIPLECOMPONENTS OF FEASIBLE REACTIONS 7HILE IT IS POSSIBLE TOTREAT SUCH SYSTEMS EXHAUSTIVELY IT IS RARELY PRACTICAL TO DOSO 4ECHNIQUES HAVE THEREFORE BEEN DEVELOPED TO SIMPLIFYSYSTEMSONARATIONALBASISSOTHATTHEREACTIONKINETICSCANBECHARACTERIZEDWITHOUTEXCESSIVEEXPERIMENTATIONANDBYUSINGAMATHEMATICALMODELOFAPPROPRIATECOMPLEXITY4WOTECHNIQUESCOMMONLYUSEDARELUMPEDMODELSANDREACTIONNETWORKS
,UMPEDMODELS!STHENAMESUGGESTSTHEESSENCEOFTHISISSIMPLIlCATIONBYCOLLECTINGRELATEDVARIABLES4HISHASBEENREFERREDTOALSOASvLUMPEDPARAMETERMODELv4HISHOWEVERISAMISNOMERASITISTHECHEMICALSPECIESRATHERTHANTHEPARAMETERSTHATAREGROUPED4HISISTYPICALLYAPPLIEDTOGROUPSOFCHEMICALSOFSIMILARPROPERTIES4HISISAPOWERFULMETHODBUTSHOULDBEDONEHOWEVERWITHEXTREMECAREANDWITHDUEATTENTIONTOWHETHERTHESIMPLIlCATIONSAREINFACTVALID!SANEXAMPLE)NTERMEZZOSHOWSTHEEXPLANATIONOFTHEOFTENOBSERVEDAPPARENTSECONDORDERBEHAVIORBUTWHICHWASFOUNDUNABLETODESCRIBEDEEP($3ACCURATELY4HECAUSE ISOVERSIMPLIlCATION 2EDUCING THE MODEL TO ONE hLUMPv IS EXCESSIVEWHEREASATHREEhLUMPvMODELCANDESCRIBETHEDEEP($3
7HENUSINGREACTIONNETWORKSDONTIGNORETHEPOSSIBILITYTHATINTERMEDIATESREACTINTERMEZZO
!SPARTOF THEHYDRODENITROGENATION ($.NETWORKOFQUINOLINETHECONVERSIONOFOFORTHOPROPYLANILINE/0!INTOPROPYLBENZENE0"PROPYLCYCLOHEXENE0#(%ANDPROPYLCYCLOHEXANE0#(HASBEENSTUDIED&IGURESHOWSTHEKINETICSCHEME4HE REACTIONS STARTING FROM/0!SHOWlRSTORDERDEPENDENCIES4HEREACTIONALSOPROCEEDSVIATHEPROPYLCYCLOHEXYLAMINE0#(!INTERMEDIATEWHICHISOBSERVEDONLYINTRACES)NCLUDED IN THISSCHEME IS THEDIRECT CONVERSIONOF/0! TO0#(TO OBTAIN A GOOD DESCRIPTION OF THE PRODUCT CONCENTRATIONS AS A
FURTHERWITHOUTDESORPTIONANDSUBSEQUENTREADSORPTION(YDRODENITROGENATIONOFQUINOLINE
FUNCTIONOFTHESPACETIMEINTHEREACTOR&IGURE4HISISEXPLAINEDBY THE FACT THAT DURING THE REACTION THERE WILL BE A COMPETITIONBETWEENDESORPTIONANDCONSECUTIVEREACTIONOFTHESURFACESPECIES4HATPARTOFTHEADSORBED/0!WILLREACTINCONSECUTIVESTEPSTOWARDSTHElNALPRODUCTACCOUNTSFORTHIS@DIRECTREACTIONSTEP)NTERMEDIATESPECIESDONTNECESSARILYHAVETODESORBlRSTBEFOREREACTINGFURTHERINACONSECUTIVESTEP4HISISANIMPORTANTASPECTOFTENOVERLOOKEDIN CONSECUTIVE REACTION SCHEMES AS IN SELECTIVE HYDROGENATIONSAND OXIDATIONS AND DEPENDS ON THE RELATIVE MAGNITUDE OF THE
&IGURE2EACTIONSCHEMEOFTHE($.OFORTHOPROPYLANILINE/0! &IGURE+INETICSOFTHE($.OFORTHOPROPYLANILINE/0!OVER.I-OAT#ONESITEMODEL;V=
/0!0"
0#(0#(%
K
K
K
K
.(
SPACETIMES
PARTIALPRESSUREK0A
0#(
/0!
0#(% 0"
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
7HENUSINGREACTIONNETWORKSDONTIGNORETHEPOSSIBILITYTHATINTERMEDIATESREACT FURTHERWITHOUTDESORPTIONANDSUBSEQUENTREADSORPTION(YDRODENITROGENATIONOFQUINOLINE
&IGURE0ROPOSEDMECHANISMFORTHE($.OFORTHOPROPYLANILINE/0!OVER.I-OONESITEMODEL;V=
CORRESPONDING RATE CONSTANTS INVOLVED /F COURSE IF ADSORPTIONDESORPTIONEQUILIBRIUMISASSUMEDTHISPHENOMENONWILLNOTOCCUR4HIS TYPE OF MODEL DEVIATES THEREFORE FROM THE CLASSICAL ,((7MODELWITHONERATEDETERMININGSTEP4HE 0#( FORMATION CAN BE DESCRIBED BY lRSTORDER IRREVERSIBLEREACTIONS FROM /0! AND FROM 0#(% !LTHOUGH /0! WILL STRONGLYADSORBAT THECATALYSTANDHENCEAZEROORDER ISANTICIPATED THEEQUALLY STRONG AMMONIA PRODUCT ADSORPTION RESULTS IN A CONSTANTDENOMINATOR OF THE RATE EXPRESSION INDEPENDANT OF CONVERSION
YIELDINGAlRSTORDERDEPENDENCY3IMILAROBSERVATIONSHAVEBEENMADE FOR THE MORE COMPLEX REACTION SCHEME IN THE SELECTIVEHYDROGENATIONOFCINNAMALDEHYDE;VI=
RESULTS ACCURATELY 4HIS EXAMPLE ILLUSTRATES ALSO THAT ONESHOULD AVOID DERIVING THE KINETIC MECHANISM FROM VISUALINSPECTIONOFTHEEXPERIMENTALDATAONLY4HEUSEOFALIMITEDRANGEOFEXPERIMENTALCONDITIONSMAYRESULTINANOVERALL PICTUREDESCRIBEDBY SIMPLE KINETIC EQUATIONS THATMAYDRAMATICALLYFAILWHENEXTRAPOLATED
2EACTIONNETWORKS!REACTIONNETWORKISESSENTIALLYAMAPPINGEXERCISEOFTHEFEASIBLE REACTIONS IN A SYSTEMWHEREMULTIPLE REACTIONS AREPOSSIBLE BOTH IN SERIES AND IN PARALLEL ! TYPICAL EXAMPLEIS SHOWN IN )NTERMEZZO 4HIS CASE STUDY HIGHLIGHTS APOTENTIALPROBLEMWITHTHISAPPROACHBASICASSUMPTIONSOFREACTIONPATHS)TISALLTOOEASYTOASSUMETHATALLREACTIONSOCCURASDISCRETEADSORPTIONnREACTIONnDESORPTIONCYCLESANDNEGLECT THE FACT THAT AN INTERMEDIATE DOES NOT NECESSARILYHAVETODESORBBEFOREITREACTSFURTHER4HISISINFACTQUITECOMMON
4HEORETICALLYBASEDKINETICMODELS)T IS POSSIBLE TO BUILD KINETIC MODELS FROM THEORETICALANDMECHANISTICCONSIDERATIONSOFTHEREACTION!COMMONAPPROACH IS THE SOCALLED ELEMENTARY STEP APPROACH WHERETHEREACTIONMECHANISMISDESCRIBEDBYASETOFSINGLEEVENTSEACH OF WHICH CAN BE ASCRIBED A RATE EQUATION OR A TERM
IN A SINGLE RATE EQUATION 4HIS CLEARLY HAS THE POTENTIALTO LEAD TO VERY COMPLEX MODELS WITH LARGE NUMBERS OFlTTING PARAMETERS )F THIS TECHNIQUE IS USED PROPERLY THEMECHANISTICUNDERSTANDINGCANINFACTLEADTOSIMPLEMODELSANDEQUATIONSTHROUGHTHERATIONALELIMINATIONOFSOMEOFTHESTEPSINORDERTOFOCUSONTHERATELIMITINGSTEPSANDKEYCOMPETITIVEPROCESSESINTHECASEOFPARALLELREACTIONS4HE DESCRIPTION OF THE REACTION KINETICS OF COMPLEX
REACTION NETWORKS REQUIRES A MODELING APPROACH MORESOPHISTICATEDTHANSIMPLYADJUSTINGTHEKINETICPARAMETERSFOREACHREACTIONINDEPENDENTLY!WELLESTABLISHEDAPPROACHFORDEVELOPINGANDUSINGAFUNDAMENTALMODELFORHYDROCRACKINGOF PARAFlNS IS SHOWN IN )NTERMEZZO 4HIS ALSO PROVESTHAT KINETIC MODELING BASED ON FUNDAMENTALS DOES NOTNECESSARILY REQUIRE lTTING OF A LARGE NUMBER OF KINETICPARAMETERSBUTTHATONTHECONTRARYPROPERFUNDAMENTALMODELS MAY REDUCE THE TOTAL NUMBER OF lT PARAMETERSSIGNIlCANTLY WITHOUT LOSING THE RELIABILITY OF THE MODELIF EXTRAPOLATED !NOTHER METHOD FOR THE MATHEMATICALTREATMENTOFTHEKINETICSINREACTIONNETWORKSCANBEFOUNDIN4EMKIN;=
7HATTYPESOFKINETICMODELSDOESINDUSTRYUSE)NTHEIRREPORTONTHEINDUSTRIALQUESTIONNAIRE"OSETAL;=CLASSIFYMODELSACCORDINGTOTHECOMPLEXITYANDTHEEXTENT
/0!
/0! 0#"
0#(! 0#(!
0#(% 0#(%
0#(
(#SNOTADSORBEDWEAKLYCOMPAREDTO.S
ONLYTRACESFOUNDSLOW
THEDIRECTROUTETO0#(
COMPETITIVEPARALLELSTEPSDIRECTGLOBALROUTES
KA
KB
KDKE
KC
FASTREACTIONSTEPS
KCKD
R/0!nKAKBK/0!P/0!
KAK/0!P/0!K.(P.(
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
-ODELTYPES
3IMPLElRSTORDERORPOWERLAW
,((7,ANGMUIRn(INSHELWOODn(OUGENn7ATSON NLUMPEDMODELSFORCOMPLEXSYSTEMS $ETAILEDMECHANISTICMODEL!BINITIOMOLECULARDYNAMICS
-ODELLEVEL !)NTRINSICKINETICMODELSEXCLUDINGALLTRANSPORTEFFECTS "!PPARENTKINETICMODELSTHATINCLUDEINTERNALTRANSPORTEFFECTS #%XTRINSICMODELSINCLUDINGALLTRANSPORTEFFECTSPLUSKINETICS
#LASSIlCATIONOFKINETICMODELS"OSETAL ;=
4ABLE
OFDECOUPLINGOFMASSTRANSFER)TWILLBEREPRODUCEDHEREASITHIGHLIGHTSTHEDIFFERENTAPPROACHES#ONCERNINGTHETYPEOFKINETICEXPRESSIONSUSEDWITHIN
THE COMPANIES MOST OF THE RESPONDENTS STATED THAT INPRINCIPLE ONE SHOULD STRIVE FOR INTRINSIC KINETICS BUTNEVERTHELESSTHEMAJORITYFORVARIOUSREASONSFREQUENTLYDONOT SEPARATE ALL TRANSPORT PHENOMENA FROM THE CHEMICALREACTIONKINETICS4HAT ISWHILETHEADVANTAGESOF INTRINSICKINETICSAREACKNOWLEDGEDTHESEADVANTAGESDONOTALWAYSOUTWEIGHTHEDIFlCULTIES INOBTAININGTHEM3PECIlCALLY IFANY OF HYDRODYNAMICS MASS TRANSFER AND KINETICS CAN BELUMPEDANDSCALEDBYSIMILARITYTHENTHIS ISOSTENSIBLYTHESIMPLESTANDMOST FAVOREDROUTEALBEITONETHATMAYBEFRAUGHTWITHDIFlCULTIES+INETIC MODELS ARE MOSTLY SIMPLE lRST OR N TH ORDER OR
,ANGMUIRn(INSHELWOOD TYPE EXPRESSIONS MORE COMPLEXKINETICMODELSARESCARCELYUSED3IMPLICITYANDMINIMIZATION
+INETICMODELINGBASEDONFUNDAMENTALSDOESNOTNECESSARILYREQUIREALARGEINTERMEZZO
4O THE CONTRARY PROPER FUNDAMENTAL MODELS MAY SIGNIlCANTLYREDUCE THE TOTAL NUMBER OF lT PARAMETERS WITHOUT LOSING THERELIABILITY OF THEMODEL IF EXTRAPOLATED 4HIS IS SHOWN HERE WITHREFERENCETOAFUNDAMENTALMODELFORHYDROCRACKING
3COPE(YDROCRACKING OF HEAVY HYDROCARBONS REPRESENTS A CASE TYPICALFOR RElNING OIL 4HE PRODUCTION CAPACITY OF RElNERY UNITS CAN BEAS HIGH AS ONE MILLION TON PER YEAR IE AMONG THE LARGEST INTHEINDUSTRY(ENCEEVENVERYMARGINALIMPROVEMENTSINPRODUCTYIELDS HAVE SIGNIlCANT EFFECTS ON THE PROCESS ECONOMICS 4HISPROVIDESASTRONGINCENTIVETOUSEDETAILEDKINETICMODELS!KEYFEATUREOFRElNINGPROCESSESISTHECOMPLEXCOMPOSITIONOFTHEFEEDANDPRODUCTSTREAMS4HOUSANDSRATHERTHANHUNDREDSOFMOLECULESARE INVOLVED!TlRSTSIGHT THE LUMPINGOF INDIVIDUALMOLECULES WITH SIMILAR PHYSICAL AND CHEMICAL PROPERTIES SEEMSVERYATTRACTIVE3UCHANAPPROACHISFACEDWITHSEVERALDRAWBACKSHOWEVER THE LACK OF A CLEAR PHYSICAL MEANING OF THE KINETICPARAMETERSINTHELUMPEDMODELBEINGTHEMAINONE4HISREQUIRESA REGRESSION OF EXPERIMENTAL DATA TO OBTAIN ESTIMATES OF THEVALUES OF THE LATTER !CTUALLY THESE VALUES CAN EVEN DEPEND ONTHE FEEDSTOCKCOMPOSITION-OREOVER THENUMBEROFPARAMETERSINCREASESDRASTICALLYWHENMORE LUMPSHAVETOBECONSIDERED INORDER TOENABLE THEMODEL TOCALCULATE RELEVANTPROPERTIESOF THEPRODUCTSTREAMSSUCHASTHEOCTANENUMBER&INALLYITISHARDTOACCOUNTFORTHEEFFECTOFCATALYSTPROPERTIESONTHEKINETICS.ONE OF THE ABOVE DISADVANTAGES ARE SHOWN BY THE SOCALLEDFUNDAMENTAL MODELS BASED ON THE KINETICS OF THE ELEMENTARYREACTIONS OCCURRING BETWEEN THE INDIVIDUAL MOLECULES PROVIDEDSOMEREASONABLEASSUMPTIONSBASEDONTHEUNDERLYINGCHEMISTRYAREMADE
NUMBEROFKINETICPARAMETERS&UNDAMENTALMODELFORHYDROCRACKING
2EACTIONCHEMISTRY(YDROCRACKING CATALYSTS ARE BIFUNCTIONAL IE THEY CONTAIN AHYDROGENATION FUNCTION ON AN ACIDIC CARRIER 4HE METALCATALYZEDREACTIONSANDTHEELEMENTARYACIDCATALYZEDREACTIONSCONSIDEREDINTHEHYDROCRACKINGOFALKANESAREDEPICTEDIN&IGURE0HYSISORPTIONOFALKANESANDALKENESINTOTHEZEOLITEPORESPRECEDESTHESEREACTIONSTEPS !LKANES OR CYCLOALKANES DEHYDROGENATE ON THEMETAL SITESWITHFORMATIONOFUNSATURATEDCYCLOALKENESWHICHINTURNMIGRATETOTHE"RNSTEDACIDSITESOFTHECARRIERWHERETHEYAREPROTONATEDYIELDING CARBENIUM IONS 4HE LATTER UNDERGO REACTIONS SUCH ASHYDRIDE AND ALKYL SHIFTS SCRAMBLING THE POSITION OF THE CHARGE OROFTHEALKYLSUBSTITUENTSPROTONATEDCYCLOPROPANE0#0BRANCHINGALTERINGTHENUMBEROFSUBSTITUENTSANDCRACKINGCLEAVINGTHE##BONDINBPOSITIONOFTHEPOSITIVECHARGE
2ATEEQUATIONS!CCOUNTINGFORALLTHEPOSSIBLEREACTIONINTERMEDIATESLEADSTOHUGEREACTIONNETWORKS3TARTINGFROMFOREXAMPLENNONADECANEALKANESALKENESANDCARBENIUMIONSINVOLVEDINDEHYDROGENATIONSDEPROTONATIONSHYDRIDESHIFTS ALKYL SHIFTS 0#0 BRANCHINGS AND BSCISSIONSHAVE TO BE CONSIDERED IN THE lRST INSTANCE )T IS VERY REASONABLEHOWEVERTOASSUMETHATTHETHERMODYNAMICANDKINETICPROPERTIESOFTHEINDIVIDUALHYDROCARBONSPECIESARECOMPLETELYDETERMINEDBYTHENATUREOFTHECARBONATOMSDIRECTLYINVOLVEDWITHTHEELEMENTARYREACTIONS )N THE SOCALLED SINGLE EVENT APPROACH DEVELOPED BY&ROMENT AND COWORKERS;VII= THE POSSIBLE EFFECTS OF THE SKELETALSTRUCTURE OF THE REACTING SPECIES ON THE RATE COEFlCIENTS ARENEGLECTED EXCEPT FOR THE GLOBAL SYMMETRY (ENCE THE LATTER ONLYDEPENDSONTHETYPEOFTHEINVOLVEDCARBENIUMIONSANDTHENUMBEROF SINGLE EVENTS WHICH EQUALS THE RATIO OF THE GLOBAL SYMMETRYNUMBEROFREACTANTANDACTIVATEDCOMPLEX
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
+INETICMODELINGBASEDONFUNDAMENTALSDOESNOTNECESSARILYREQUIREALARGE
&IGURE2EACTIONSCHEMEOFTHE($.OFORTHOPROPYLANILINE/0!
NUMBEROFKINETICPARAMETERS&UNDAMENTALMODELFORHYDROCRACKING
OF NUMBER OF EXPERIMENTS IS PARAMOUNT )NTERESTINGLYENGINEERINGCOMPANIESAREMOSTLIKELYTOUSEINTRINSICKINETICSWHILECATALYSTCOMPANIESFAVORTHEMLEAST3IGNIlCANTLYTHEREISNOEVIDENCEFORSIGNIlCANTUSEOFMECHANISTICORABINITIOMODELS
!CQUISITIONOFKINETICDATA4HEAMOUNTOFEFFORTTHATSHOULDBEPUTINTOTHETHEORETICALASPECTOFAKINETICINVESTIGATIONDEPENDSONTHECOMPLEXITYOFTHEREACTIONSCHEMETHENONLINEARITYOFTHEDEPENDENCIESOF THE VARIABLES AND THE RELIABILITY OF THE REQUIRED KINETICMODEL4HISISOFCOURSETHETECHNICALDRIVER!LSOTOCONSIDERISTHEULTIMATEESTIMATEDPRODUCTVALUEANDTHEPROBABLECOSTOFNONCONFORMANCEOFTHEKINETICSlNANCIALSAFETYHEALTHANDENVIRONMENT!SNOTEDABOVEONLYOCCASIONALLYDOESINDUSTRYDEVELOPCOMPLEXKINETICMODELS
3ELECTIONOFEXPERIMENTALREACTOR!NYKINETIC INVESTIGATIONSHOULDSTARTWITHA SEARCHOF THEEXISTINGKNOWLEDGECONCERNINGTHEREACTIONSYSTEM!RMEDWITH THE INFORMATION AVAILABLE FROM THE LITERATURE AND THESTARTOFACONCEPTUALMODELOFTHEKINETICSITISPOSSIBLETOSTARTCONSIDERINGTHEEXPERIMENTALAPPROACHTHEEQUIPMENTTOUSEANDTHEEXPERIMENTALCONDITIONSANDPROGRAM4HEINITIALSTEPISUSUALLYTOCONSIDERTHETYPEOFREACTOR
TOBEUSED)NMANYSTUDIESITMAYBEEXPEDIENTTOUSEMORETHANONETYPE4ABLESGIVEOVERVIEWSOFSOMEPOSSIBLELABORATORY REACTORS FOR KINETIC DATE MEASUREMENT FOR GASnSOLIDANDGASnLIQUIDnSOLIDSYSTEMSRESPECTIVELY!LSOGIVENARESOMEOFTHEIMPORTANTCHARACTERISTICSOFTHOSEREACTORS
'ASnSOLIDREACTIONS.O SINGLE REACTOR IS RIGHT FOR ALL SYSTEMS AND THEREFORE APLURALITYOFTYPESEXISTSASDEMONSTRATEDBY4ABLEWHICH
7HENONLYSECONDARYANDTERTIARYCARBENIUMIONSARECONSIDEREDTHE ABOVE ASSUMPTIONS REDUCE THE NUMBER OF DIFFERENT TYPES OFELEMENTARY REACTIONS TO 4HIS INCLUDES ALKYL SHIFTS INTRARINGALKYLSHIFTS0#0BRANCHINGSRINGCONTRACTIONSACYCLICBSCISSIONSENDOCYCLICBSCISSIONSANDEXOCYCLICBSCISSIONS!SSUMING QUASIEQUILIBRIUM OF THE DEHYDROGENATIONS AND THATTHECONCENTRATIONOFCARBENIUMIONSCANBENEGLECTEDCOMPAREDTOTHETOTALCONCENTRATIONOFACIDSITESLEADSTOTHECORRESPONDINGRATEEQUATIONSIN&IGURE
-ODELPARAMETERS"OTHTHERMODYNAMICANDKINETICPARAMETERSAREPRESENTINTHERATEEQUATIONSL 4HE DEHYDROGENATION EQUILIBRIUM COEFlCIENT +DEH CAN BECALCULATEDFROMTABULATEDTHERMODYNAMICDATA
L 4HE PHYSISORPTION EQUILIBRIUM COEFlCIENT +, AS WELL AS THESORPTION CAPACITY #SAT DEPEND ON THE CATALYST AND HAVE TOBEDETERMINEDEXPERIMENTALLYPREFERABLY INDEPENDENTLY FROMTHE EXPERIMENTS AIMED AT THE DETERMINATION OF THE KINETICPARAMETERS;VIII=
L 4HE RATE COEFlCIENTS K ONLY APPEAR COMBINED WITH THEEQUILIBRIUMCOEFlCIENTS FORPROTONATION+PROT(ENCE IT IS NOTTHEIR INDIVIDUAL VALUE BUT ONLY THAT OF THE PRODUCT K+PROT THECOMPOSITERATECOEFlCIENTWHICHAFFECTSTHEREACTIONRATES/FCOURSE THE LATTER SHOULD SHOW AN !RRHENIUS DEPENDENCY ONTEMPERATURE
L 4HECOMPOSITEPREEXPONENTIAL!RRHENIUSFACTOR!COMPCANBECALCULATED WITHOUT THE REGRESSION OF KINETIC DATA BASED ONTRANSITIONSTATETHEORYANDONTHEPREEXPONENTIALFACTOROFTHEPHYSISORPTIONEQUILIBRIUMCOEFlCIENT;IXX=
SEENEXT
GASPHASEPHYSISORPTION
DEHYDROGENATION
DEPROTONATIONALKYLSHIFT0#0BRANCHING
SCISSION
ZEOLITE
METALSITES
ACIDSITES
&IGURE(YDROCRACKINGREACTIONMECHANISM
&IGURE(YDROCRACKING2ATE%QUATIONS(#HYDROCARBON
CALCULATEDVIATHERMODYNAMICDATA
DETERMINEDBY.(40$
PARAMETERSTOBEESTIMATED
#CAT#TK+PROT+DEH+,P(#P(R+,P(#
DETERMINEDBYPHYSISORPTIONEXPERIMENTS
ACT24
KCOMPK+PROT!COMPEXP
%COMP
ACT%COMP%ACT$(PROT
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
'n3REACTOR )NVESTIGATION +INETICS )SOTHERMICITY $EACTIVATING 4YPICAL &AST #OSTS OFFAST ATHIGH CATALYSTS PARTICLE EXPERIMENTATION LOWHIGH REACTIONS CONVERSIONS SIZE;MM=
DIFFERENTIALlXEDBED n
INTEGRALlXEDBED n ENTRAINEDmOWREACTOR RECYCLEGRADIENTLESSlXEDBED n THERMALGRAVIMETRICANALYSIS DIFFERENTIALmUIDIZEDBED n PULSElXEDBED n TEMPORALANALYSISOFPRODUCTS n TEMPPROGRAMMEDREACTOR n
4ABLE
/VERVIEWOFCHARACTERISTICSOFSEVERALTYPESOFGASnSOLIDREACTORSWHICHCANBEUSEDTOSELECTTHEREACTORTOCARRYOUTTHEKINETICEXPERIMENTS
(ENCE COMPOSITE ACTIVATION ENERGIES %COMP HAVE TO BEESTIMATEDIEOBTAINEDBYREGRESSIONOFKINETICDATA-ARTENSETAL;IXX= OBTAINED SUCH A SET OF PARAMETERS BY REGRESSION OF DATAOBTAINEDON0T539ZEOLITESANDFEEDINGPURECOMPONENTSSUCHAS NALKANES IN THE RANGE # TO # AND CYCLOALKANES SUCH ASMETHYLCYCLOHEXANEETHYLCYCLOHEXANEANDNBUTYLCYCLOHEXANETOA CONTINUOUS STIRRED TANK REACTOR #342 AT PRESSURES FROM TO-0AMOLARHYDROGEN TOHYDROCARBON RATIOS FROM TOAND TEMPERATURES FROM TO + !T THESE CONDITIONS THEHYDROCARBONSAREINAGASEOUSSTATE)NTOTALMORETHANDATAWERE REGRESSED @&IGURE A SHOWS A TYPICAL CONVERSION VERSUSSPACETIMERELATIONAND&IGUREBSHOWSTHEEFFECTOFCONVERSIONONTHEPRODUCTDISTRIBUTIONFORNDODECANEATONESETOFCONDITIONS)NVIEWOFTHEAMOUNTOFEXPERIMENTALDATATHENUMBEROFADJUSTABLEPARAMETERS IS RATHER LIMITED4HISAMONGOTHER THINGS ISDUE TOTHEASSUMEDINDEPENDENCEOFTHELATTERONTHEHYDROCARBONCHAINLENGTH 4HE LATTER IS TOTALLY ACCOUNTED FOR VIA THE PHYSISORPTIONPARAMETERS#SATAND+,4HE ADEQUATE MATHEMATICAL DESCRIPTION OF CONVERSIONS ANDSELECTIVITIESONAGIVENCATALYSTASDISCUSSED TILLNOW ISCERTAINLYANIMPORTANTGOALOFKINETICMODELING4HECAPABILITYOFTAKINGINTOACCOUNT THE KINETICALLY RELEVANT PROPERTIES OF THE CATALYST IS ANEVENMOREIMPORTANTFEATUREOFTHEHYDROCRACKINGMODELPRESENTEDHERE)NDEEDTHERATEEQUATIONSCONTAINTWOPARAMETERSRELATEDTOTHECATALYSTTHETOTALCONCENTRATIONOFACIDSITES#TANDTHESTANDARDPROTONATIONENTHALPY$(OPROT4HELATTERISAMEASUREOFTHEAVERAGESTRENGTHOFTHEACID;XIXII=!DJUSTINGONLYTHESETWOPARAMETERSANDTHEHYDROCRACKINGON539ZEOLITESWITHADIFFERENTAVERAGEACIDSTRENGTHSCANBEMODELEDADEQUATELY
&IGUREA#ONVERSIONVSSPACETIME+BARINLET(TONDODECANEMOLARRATIO
&IGUREB)SOMERIZATIONANDCRACKINGCONVERSIONVSTOTALCONVERSIONFORALLEXPERIMENTALCONDITIONSSYMBOLSEXPERIMENTALCURVESMODELPREDICTIONS
&IGURE-ASSmUXESOFMAJORPRODUCTFRACTIONSASAFUNCTIONOFAXIALREACTORCOORDINATEATTYPICALINDUSTRIALCONDITIONSFEEDSTOCKHYDROGENATEDVACUUMGASOIL;XIII=
7&KGSMOL
4OTALCONVERSION
TOTALCONVERSION
ISOMERIZATION
CRACKINGCONVERSION
ISOMERIZATION
CRACKING
AXIALPOSITIONM
MASSFLUXKGS M
,0'
NAPHTHA
MIDDLEDISTILLATERESIDUE
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
)NDUSTRIALLY HYDROCRACKING IS PERFORMED IN AN ADIABATIC lXED BEDREACTOR CONSISTING OF THREE PHASES THE lXED CATALYTIC BED AND AmOWOFGASANDOF LIQUID)NTHETRICKLEmOWREGIMETHELIQUIDmOWSDOWNDISPERSEDINTHEFORMOFDROPLETSANDRIVULETSCONCURRENTLYWITHTHE CONTINUOUS GAS PHASE #LEARLY THIS IS QUITE A DIFFERENCE WITHTHEHYDRODYNAMICS IN THE#342SETUPUSEDFOR THEDETERMINATIONOF THE REACTION KINETICS 0ROVIDED THAT THE LATTER CORRESPONDS TOINTRINSIC KINETICS IE REmECT ONLY CHEMICAL AND HENCE SCALEINDEPENDENTPHENOMENATHEIRAPPLICATIONTOINDUSTRIALHYDROCRACKINGIS STRAIGHTFORWARD )T SUFlCES TO SUBSTITUTE THE RATE EQUATIONS INTHE REACTOR MODEL EQUATIONS ACCOUNTING FOR THE TRICKLE mOW IN ANAPPROPRIATE WAY 4HE LATTER CONSISTS OF THE CONSERVATION LAWS FORMASSENERGYANDMOMENTUM&IGURESHOWSTHEEVOLUTIONOFTHEDIFFERENTPRODUCTFRACTIONSASTHEVACUUMGASOILSTREAMSTHROUGHTHECATALYSTBEDATTYPICALINDUSTRIAL
'n,n3REACTOR )NVESTIGATIONOF )NVESTIGATIONOF $EACTIVATING 4YPICALRESIDENCE 4YPICALCATA &AST #OSTS FASTREACTIONS SEQUENTIALREACTIONS CATALYSTS TIMELIQUID LYSTSIZE;MM= EXPERIMENTATION LOWHIGH
TRICKLEBED S n
UPmOWPACKEDBED MIN n SPINNINGBASKET nMIN INTERNALRECIRCULATIONREACTOR nMIN SLURRYREACTORSEMIBATCH nHR n SLURRYREACTORCONTINUOUS nMIN n BUBBLECOLUMN MIN GASLIFTREACTOR MIN WETTEDWALL S NOTAPPLIC PULSETRICKLEBED S n PULSESLURRYREACTOR MIN n 4ABLE
/VERVIEWOFCHARACTERISTICSOFSEVERALTYPESOFGASnLIQUIDnSOLIDREACTORSWHICHCANBEUSEDTOSELECTTHEREACTORTOCARRYOUTTHEKINETICEXPERIMENTS
CONDITIONS 4HE CARBON NUMBER OF THE FEED RANGES FROM TO 4HE RESIDUE CONSISTS OF THE HYDROCARBON FRACTIONWITH ORMORE CARBON ATOMS .OTE THAT THE LUMPING INTO ,0' NAPHTHAMIDDLEDISTILLATESANDRESIDUEISONLYPERFORMEDFORREPRESENTATIONPURPOSES 4HE KNOWLEDGE OF THE KINETICS OF THE TYPES OFELEMENTARY REACTIONS ALLOWS US TO DESCRIBE THE VACUUM GASOILCONVERSIONANDTHERESULTINGPRODUCTDISTRIBUTIONUPTOTHELEVELOFTHEINDIVIDUALMOLECULES/FCOURSESUCHADEGREEOFPRECISIONISNEITHERREALLYREQUIREDNORATTAINABLE4HEMAJORBOTTLENECKCONSISTSOF THE LACKOFMOLECULAR INFORMATIONPROVIDEDBYTODAYSSTATEOFTHEARTANALYTICALTECHNIQUES"UTAGAINASTHEFUNDAMENTALKINETICMODEL CONTAINS INFORMATION UP TO THEMOLECULAR LEVEL RELUMPINGCANOCCURTOANEXTENTDEEMEDAPPROPRIATE&IGUREILLUSTRATESTHISBYSHOWINGTHEEVOLUTIONOFTHELIQUIDCONCENTRATIONOFCOMPONENTSCONSTITUTINGA FRACTIONOF THE RESIDUE THEMONOCYCLICNAPHTHENICLUMPSWITHCARBONNUMBERBETWEENAND
&IGURE"REAKDOWNOFTHEMONOCYCLICNAPHTHENEFRACTIONOFTHERESIDUEASAFUNCTIONOFTHEAXIALREACTORCOORDINATE;XIII=
AXIALPOSITIONM
LIQUIDCONCENTRATIONMOLM
MO. MO.
MO.MO.MO. MO. MO.
MO.MO.
MO.
!PPLICATIONTOTHEHYDROCRACKINGOFAHYDROGENATEDVACUUMGASOIL
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
&IGURE3IXTUBEMICROREACTORINSTALLATIONREPRODUCEDCOURTESYOF3YNETIX
4HERMOGRAVIMETRICANALYSIS4'!ISNOWAWELLESTABLISHEDTECHNIQUE BUT CONSIDER ALSO THAT THE TAPERED ELEMENTOSCILLATING MICROBALANCE 4%/- WHICH HAS MUCH BETTERGASnSOLID MASS TRANSFER CHARACTERISTICS THAN THE 4'!DUE TO THE FORCED mOW THROUGH A SMALL PACKED BED;=4HE 4%/- HAS BEEN SUCCESSFULLY USED TO MEASURE COKEDEPOSITION KINETICS;= AND CHANGING OXIDATION STATES OFOXIDE CATALYSTS;= )F AN IMPORTANT PART OF THE KINETICINFORMATION CAN BE DERIVED FROM CALORIMETRY DIFFERENTIALSCANNING CALORIMETRY $3# COULD BE OF INTEREST )N lNECHEMICALS CALORIMETER REACTORS ARE BECOMING INCREASINGLYPOPULARPARTLYBECAUSETHEYPROVIDETHEKEYINFORMATIONFORSAFETYINADDITIONTOTHERATEDATA
&IGURE $IAGRAM OF A "ERTYTYPE INTERNAL RECYCLE REACTOR 2EPRODUCEDCOURTESYOF!UTOCLAVE%NGINEERS
IS A SUMMARIZED VERSION %ASILY THE MOST COMMON FORMOF REACTOR FORMEASURINGKINETICSOVER A STATIONARY CATALYSTIS THE lXED BED MICROREACTOR 4HESE CAN BE OPERATED INDIFFERENTIALFORMVIZLOWCONVERSIONORININTEGRALMODEATHIGHERCONVERSIONS4HElXEDBEDMICROREACTORSAREESSENTIALLYSMALLTUBULARREACTORSSAYnMMINCHIN DIAMETER OPERATED WITH DIFFERENT CATALYST VOLUMES ANDSPACEVELOCITIESTOOBTAINEITHERTHEVERYLOWORRELATIVELYHIGHCONVERSIONSREQUIRED-ICROREACTORSARENOWWELLESTABLISHEDANDTHEBESTAREFULLYAUTOMATEDWITHMORETHANONEREACTORTUBEOPERATINGINPARALLELSEE&IGURE4HE THIRD CLASSIC CONlGURATION IS THE WELLMIXED OR
GRADIENTLESSREACTORTYPIlEDBYTHE"ERTYAND#ARBERRYTYPEREACTORS "ECAUSE THE REACTOR IS WELLMIXED THE REACTOR ISEFFECTIVELYATTHEEXITCONCENTRATION)NTHECASEOFA"ERTYREACTOR SEE &IGURE A TURBINETYPE IMPELLER DRIVES THEGASTHROUGHTHECATALYST!NALTERNATEDESIGNTHE#ARBERRYREACTORHASTHECATALYSTINACROSSROTATINGBASKETTHATITSELFACTSASTHEIMPELLER4HESETHREECONlGURATIONSOROPERATINGAPPROACHESARE
COMPAREDIN&IGUREINTERMSOFTHERELATIONSHIPBETWEENTHE RATE AND THE CONVERSION 4HE FUNDAMENTAL DIFFERENCEBETWEENTHEDIFFERENTIALREACTORANDTHEGRADIENTLESSREACTORLIES IN THE FACT THAT IN THE DIFFERENTIAL REACTOR WITH LOWCONVERSIONS THE REACTOR IS PREDOMINANTLY AT THE FEEDCOMPOSITIONWHEREASFORTHERECYCLEREACTORASSUMINGPERFECTMIXINGTHECONCENTRATIONINTHEREACTORAPPROXIMATESTOTHEEXIT CONCENTRATION 4HEREFORE THE REACTORS FUNDAMENTALLYMEASURE THE KINETICS UNDER DIFFERENT PROCESS CONDITIONSREGARDINGCOMPOSITIONANDCONVERSION4HElXEDBEDMICROREACTORSANDTHEGRADIENTLESSVERSION
ARE THE WORKHORSES OF GAS PHASE HETEROGENEOUS CATALYTICKINETICS 4HERE IS HOWEVER AN INCREASING NUMBER OFALTERNATIVES SOME OF WHICH ARE PARTICULARLY SUITED TOSPECIlC PROBLEMS )F A CATALYST MASS CHANGE DUE TO THEREACTION YIELDS IMPORTANT KINETIC INFORMATION ONE COULDSELECT A REACTOR CAPABLE OF ONLINE MASS MEASUREMENT
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
$###
#CONCENTRATION
,DISTANCETHROUGHREACTOR
#
DIFFERENTIAL RECYCLEGRADIENTLESS
#
#CONCENTRATION
,DISTANCETHROUGHREACTOR
INTEGRAL
#
#CONCENTRATION
,DISTANCETHROUGHREACTOR
Rt$#7&
$#SMALL
RtD#D7
$# R&D7
Rt$#7&
$#LARGE
&ORCASESWHERETHECHOICEISNOTSOCLEAR4ABLECANBEUSEDASAGUIDELINEFORTHECHOICEOFTHEREACTOR&ROMTHETABLEITFOLLOWSTHATIMPORTANTQUESTIONSTOBEANSWEREDAREI !RETHEREACTIONSRELATIVELYFASTII )S KINETIC DATA NEEDED AT HIGH CONVERSIONS CAN BE OBTAINEDRELATIVELYEASYINARECYCLEREACTORIII !RETHEREACTIONSSTRONGLYEXOORENDOTHERMICANDIV $OESTHECATALYSTDEACTIVATESIGNIlCANTLY
&IGURE#OMPARISONOFCOMMONLABORATORYmOWMICROREACTORSUSEDFORKINETICMEASUREMENTS
&IGURE$IAGRAMOFA2OBINSONn-AHONEYREACTOR2EPRODUCEDCOURTESYOF!UTOCLAVE%NGINEERS
/THER ASPECTSMAY ALSO INmUENCE THE CHOICE SUCH AS THEAPPROACH TO IDEAL PLUG mOW OR MIXING THE RISK OF mOWMALDISTRIBUTION THE EASE OF MEASUREMENT OF THE CATALYSTTEMPERATURE AND THE EASE OF WITHDRAWING SAMPLES 4HEAVAILABLE CATALYST SIZE THE ALLOWABLE REACTOR COSTS AND THEEXPERIMENTALEFlCIENCYAMOUNTOFKINETICDATAPERUNITOFTIMEOFEXPERIMENTATIONWILLDETERMINETHElNALCHOICE2EACTORSOPERATEDATSTEADYSTATEAREEXPERIMENTALLYTHE
MOSTCONVENIENTBUTTHEDYNAMICALLYOPERATEDSYSTEMSARENOWRECEIVINGINCREASINGATTENTION4HESEINCLUDETHEPULSEDlXEDBEDTEMPORALANALYSISOFPRODUCTS4!0ANDTEMPERATUREPROGRAMMEDREACTORSMENTIONEDIN4ABLE(OWEVERWHILETHEYDOALLOWFASTACQUISITIONOFKINETICDATAITISNOTALWAYSCLEARHOWTOTRANSLATETHOSEDATAINTOAMATHEMATICALMODEL4HEYOFTENALSOREQUIREAMORESKILLEDOREXPERIENCEDOPERATORORA SIGNIlCANTLY LONGER LEARNINGPERIOD)NGENERALTHESEREACTORSAREMAINLYOFINTERESTFOREXTENSIVEKINETICINVESTIGATIONSINCLUDINGELUCIDATIONOFMECHANISTICASPECTS4HElNALCHOICEOFTHEREACTORISUSUALLYDETERMINEDBYTHEFOLLOWINGASPECTSv !BSOLUTEREACTIONRATEv #ATALYSTSHAPEANDSIZEv 4HE REACTORS ALREADY AVAILABLE IN THE LABORATORY OR THE RELATIVECOSTSOFTHEALTERNATIVENEWINSTALLATIONSv ,IKELIHOODOFSIGNIlCANTTRANSPORTLIMITATIONSMASSAND HEATTRANSFERv .ONIDEALITIES SUCH AS mOW DISTRIBUTION AND HYDRODYNAMICS
)F POSSIBLE ANY COMPLICATIONS ARISING FROM NONKINETICPARAMETERSIMPINGINGONTHEOBSERVATIONOFINTRINSICKINETICSSHOULDBECIRCUMVENTEDBYCHOOSINGPROPERTESTCONDITIONS
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
'ASnLIQUIDnSOLIDREACTIONS4HE CHOICE OF THE REACTOR FOR INVESTIGATION OF THE KINETICSOF GASnLIQUIDnSOLID SYSTEMS IS USUALLY DETERMINED BY THECHARACTERISTICS SHOWN IN 4ABLE &OR THOROUGH KINETICINVESTIGATIONSINWHICHTHEINmUENCEOFTHEREACTIONPRODUCTSAND SEQUENTIAL REACTIONS SHOULD ALSO BE INVESTIGATED ONLYTHESLURRYREACTORANDTHEINTERNALRECIRCULATIONREACTORARETRULY RECOMMENDED 4HE SLURRY REACTOR MOST COMMONLY ALMOST INEVITABLY TAKES THE FORMAT OF A STIRREDAUTOCLAVE)FNOTPROPERLYASSESSEDTHESESYSTEMSCANEASILYBE PRONE TO MASS TRANSPORT LIMITATIONS PARTICULARLY ATTHE GASnLIQUID INTERFACE ! COMMONLY USED TYPE OF GASnLIQUIDnSOLIDGRADIENTLESSINTERNALRECIRCULATIONREACTORISTHE2OBINSONn-AHONEY REACTOR SEE&IGUREWHERE THEGASnLIQUID DISPERSION IS FORCED THOUGH A CATALYST BASKET 4WOALTERNATIVETYPESOFINTERNALRECIRCULATIONREACTORSHAVEBEENPROVEN SUCCESSFUL FOR KINETIC INVESTIGATIONS THE TURBINEREACTORINWHICHTHEGASnLIQUIDMIXTUREISTRANSPORTEDBACKTOTHETOPBYTURBINEBLADESLOCATEDINTHEOUTERANNULAROFTHEREACTOR;=ANDTHESCREWIMPELLERSTIRREDREACTOR3)32HAVING THE SCREW IN THE CENTRAL SHAFT;="OTH REACTORS ARESHOWNIN&IGURE
3ELECTIONOFEXPERIMENTALCONDITIONS)T IS EVIDENT THAT THE REACTOR AND ANALYTICAL EQUIPMENTGENERALLYLIMITTHERANGEOFTHEEXPERIMENTALCONDITIONSTHATCAN BE COVERED (OWEVER SEVERAL ADDITIONAL ASPECTS MAYFURTHER LIMIT THE RANGES OF CONDITIONS AT WHICH USEFULKINETIC DATA CAN BE OBTAINED )F INTRINSIC KINETICS ARE TOBE ASSURED IT IS ESSENTIAL TO CHECK ON RATE LIMITATION DUETO MASS AND HEAT TRANSPORT LIMITATIONS /NE SHOULD ALSOCHECK FOR OTHER PHENOMENA CAUSING NONIDEALITY SUCH ASAXIAL DISPERSION IN A TUBULAR REACTOR CATALYST BYPASS ANDINADEQUATEMACROMIXING4HEREARESEVERALhTRICKSvUSEDTOGENERATE CONDITIONS WHERE TRANSPORT IS NOT LIMITING 4HEMOST COMMONOF THESE IS THE USE OF INERT PARTICLESMIXEDINWITHTHECATALYSTTOARTIlCIALLYINCREASETHEACTIVEREACTORBULKVOLUME4HISDILUTESANYHEATEFFECTSANDBYDILUTIONWITH lNE PARTICLES AXIAL DISPERSION AND BYPASSING CAN BELIMITEDEVENFORACOMBINATIONOFARELATIVELYSHORTBEDANDINDUSTRIALCATALYSTPARTICLESIZE)FTHEPROBLEMISINTRAPELLETTHENTHEONLYOPTIONISTOOPERATEWITHASMALLERPARTICLESIZE4ABLES AND GIVE AN INDICATION OF SUITABLE CATALYST
SIZE AND SHAPE SUCH AS POWDER SMALL CRUSHED PARTICLESANDCOMPLETECATALYSTBODIES)F INTRINSICKINETICSARETOBE
&IGURE!LTERNATEREACTORSFORMULTIPHASEKINETICSMEASUREMENTSATURBINEREACTORBSCREWIMPELLERSTIRREDREACTOR
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
MEASURED THE PRECISE CATALYST SIZE TO BE USED SHOULD BEESTIMATEDVIACALCULATIONSCONCERNING TRANSPORT LIMITATIONSAND OTHER PHENOMENA POSSIBLY CAUSING NONIDEALITIES !SNOTEDABOVEIFLARGECATALYSTPELLETSARETOBEUSEDINPRACTICE IT MAY BE EXPEDIENT TO USE FULLSIZED PELLETS OFTENDILUTEDWITHINERTPARTICLESANDMEASURETHEAPPARENTKINETICSWITHTHEKNOWLEDGETHATTHEDATAWILLINCLUDEINTRAPELLETTRANSPORTEFFECTS4HEEXPERIMENTALREQUIREMENTFORINTRINSICKINETICSISA
MAJORAREAOFSTUDYINITSOWNRIGHTANDANYTHINGMORETHANASTATEMENTOFAWARENESSISBEYONDTHESCOPEOFTHISPAPER4HEREISACONSIDERABLEWEALTHOFLITERATUREAVAILABLEINTHISlELDSEEFOREXAMPLE+APTEIJN-OULIJN;=OR&ROMENT"ISCHOFF;=/NCE THE RANGE OF SUITABLE CONDITIONS IS SET A CHOICE
HAS TO BE MADE FOR THE NUMBER OF EXPERIMENTS AND THESETS OF CONDITIONS AT WHICH THESE SHOULD BE CARRIED OUT&ROMAMECHANISTICPOINTOFVIEW ITOFTEN ISASSUMEDTHATMOST RELIABLE RESULTS WILL BE OBTAINED WHEN VARYING THEINDEPENDENTVARIABLESJUSTONEBYONE(OWEVERASTATISTICALAPPROACHWILLFREQUENTLYINCREASEEXPERIMENTALEFlCIENCYBYVARYINGMORETHANONEINDEPENDENTVARIABLESIMULTANEOUSLY/FCOURSETHISHASTHEDISADVANTAGETHATEVALUATIONOFTHEDATABYVISUALINSPECTIONRATHERTHANBYSTATISTICALANALYSISBECOMES HARDER %XPERIMENTAL DESIGN IS ALSO A LARGE lELDANDBEYONDTHESCOPEOFTHECURRENTPAPER!TITSSIMPLESTTHIS IS EPITOMIZED BY FACTORIAL DESIGN ALTHOUGH MORESOPHISTICATEDTECHNIQUESAREAVAILABLEWHICHARENONLINEARINTHEIRAPPROACH;=
-EASUREMENTOFKINETICSININDUSTRY)TISTIMENOWTORETURNTOTHEINDUSTRIALSURVEY4HERESULTSAREFAIRLYEMPHATIC!LLCOMPANIESDOEMPLOYINHOUSETESTUNITS FOR MEASURING KINETIC DATA ALTHOUGH MANY ALSO DOKINETICWORKINCOLLABORATIONWITHACADEMICINSTITUTIONSANDRESEARCH ORGANIZATIONSWITH OF REPLIES CITING THE USEOF EXTERNAL DATA!LL RESPONDENTS CITE THEUSEOF lXEDBEDMICROREACTORSWHICHCOMESASNOSURPRISE4HEUSEOFPILOTPLANTFORMODELlTTINGISCOMMONPLACEBUTONLYUSEFULLSCALEPLANTOPERATINGDATAFORTHISPURPOSE!SREGARDSLABORATORYREACTORTYPESHOWEVERUTILIZATION
IS LESS WIDESPREAD /NLY CITE THE USE OF RECYCLEDOR GRADIENTLESS REACTORS WHILE AS FEW AS HAVEUSED TEMPERATURE PROGRAMMED TECHNIQUES AND ONLY ONERESPONDINGCOMPANYPOSSESSEDA4!0REACTOR4HESEDATA ARE A FEWYEARSOLDNOWBUT IN TRUTH LITTLE
HASREALLYCHANGED)NDUSTRYSTILLRELIESHEAVILYONlXEDBEDMICROREACTORSFORGASPHASEREACTIONSALMOSTTOTHEPOINTOFEXCLUSIVITY'IVEN THE IMPROVEMENT IN THE TECHNIQUESNOWONGOINGINACADEMIATHEREISCLEARLYHEADROOMWHICHSHALLBEADDRESSEDLATER)T IS ALSO APPARENT FROM THE SURVEY THAT INDUSTRY DOES
NOT BELIEVE IT IS AS CAREFUL AS IT SHOULD BE IN SELECTINGEXPERIMENTAL CONDITIONS 4HE ABSENCE OF MASS TRANSFERLIMITATIONISNORMALLYCHECKEDATLEASTEXPERIMENTALLY0LUG
mOWANDISOTHERMICITYAREFREQUENTLYASSUMEDWITHOUTANYSUCH VERIlCATION THE USE OF RIGOROUS MODELS TO DESCRIBETHEMICROREACTORISRARE4HEGOALSHOULDBESIMPLEREACTORSTHAT REQUIREONLY SIMPLEMODELS )NMORE COMPLEXMIXINGSITUATIONSSUCHASMULTIPHASEANDmUIDIZEDSYSTEMSTHEUSEOFCOLDmOWMODELSFORTHEHYDRODYNAMICSANDMASSTRANSFERISRARE#OLLECTIVELYTHEREFOREINDUSTRYBELIEVESITISMAYBENOT
ASDILIGENT AS IT SHOULDBE INENSURING THE INTRINSICNATUREOF ITS KINETICS 4HIS IS ALMOST CERTAINLY MITIGATED BY ANENORMOUSACCUMULATEDEXPERIENCEINTRANSLATINGLABORATORYDATA INTOKINETICMODELSANDUSINGTHESETOACCURATELYANDSAFELYPREDICTTHEPERFORMANCEOFACOMMERCIALREACTOR
+INETICMODELING7HENASERIESOFEXPERIMENTSHASBEENCARRIEDOUTITISTHENNECESSARY TO DEVELOP ONE OR MORE KINETIC MODELS AND TOTRYTOADJUSTTHEKINETICPARAMETERSBYlTTINGTHEMATHEMATICAL EXPRESSIONS TO THE EXPERIMENTAL DATA 4HE AMOUNT OFWORKREQUIREDFORTHISISOFTENSIGNIlCANTLYUNDERESTIMATEDBECAUSEOFUNEXPECTEDCOMPLICATIONS#OMMONhCOMPLICATIONSvON THECHEMICAL SIDEARE LOWLEVEL IMPURITIES IN THEFEEDUNEXPECTEDSIDEREACTIONSANDUNCERTAINTIESCONCERNING THE PHYSICAL PROPERTIES OF THE MIXTURE OR OF SOME OFTHECOMPOUNDSPRESENT%XAMPLESONTHEEXPERIMENTALSIDEARERESIDUESOFCHEMICALSINTHEREACTORFROMPREVIOUSWORKREACTOR WALLS TAKING PART IN THE REACTION DIFlCULTIES WITHCHEMICALANALYSISANDINACCURACIESOFTHEANALYTICALEQUIPMENT0ROBLEMSALSOOCCURWITHTHEMODELINGITSELFSUCHASTHEUSEOFAKINETICMODEL THAT ISEITHER TOOSIMPLEOR TOOCOMPLEXTHEUSEOFONLYONEORINSUFlCIENTDIFFERENTMODELSANDALACKOFPHYSICOCHEMICALBACKGROUNDOFTHOSEMODELS/FCOURSEKINETICRESEARCHHASBEENCARRIEDOUTFORMANY
YEARSANDACCORDINGLYTHEREISMUCHEXPERIENCEAVAILABLEINTHE LITERATURE AND IN MANY LABORATORIES REGARDING SUITABLEAPPROACHES FOR DIFFERENT PROBLEMS RECOMMENDATIONS TOIMPROVETHEACCURACYOFMODELSWAYSTOENHANCETHEENTIREINVESTIGATIONANDLASTBUTNOTLEASTAFEWPITFALLSTOAVOID!NUMBEROFCASESTUDIESHAVEALREADYBEENINTRODUCED4HESEANDAFEWMOREWILLNOWBEUSEDTOTELLAFEWSALUTARYTALESANDTOTRYANDDEMONSTRATEGOODPRACTICEANDLEADTOSOMESIMPLE RECOMMENDATIONS ON KEY POINTS TO CONSIDER WHENDOINGKINETICMODELING7ORK ON THE REACTION KINETICS CAN USEFULLY BEGIN EVEN
IN THE EARLIEST STAGES OF A CATALYST OR REACTOR DEVELOPMENTPROGRAM SEE )NTERMEZZO 2ATHER SIMPLE MODELS THATDESCRIBE THE IMPORTANT REACTIONS REASONABLYWELL CAN BE ARELATIVELYCHEAPBUTVERYUSEFULINPUTINPRIMARYECONOMICEVALUATIONS CONCERNING THE FULLSCALE PRODUCTION AND THEAMOUNTOFINVESTIGATIONANDDEVELOPMENTWORKREQUIRED!LTHOUGH KINETIC MODELING USUALLY NEEDS THE REACTION
MECHANISMPURELYASANINPUTTOHELPBUILDAMATHEMATICALDESCRIPTIONOFTHEEVENTSOCCURRINGITCANALSOLEADTONEWINSIGHTSINTHEREACTIONMECHANISMANDREACTIONSEQUENCES!N EXAMPLE CONCERNING THE DISCOVERY OF A NEW INSIGHT
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
//
/
/
/(/
/
/
/(/
/
/
//
/
/
//
/
/
2
2
2
2
2
22
3TARTYOURKINETICSSTUDIESEARLYINTHEDEVELOPMENTPROGRAMFORMAXIMUMADVANTAGEINTERMEZZO
3INCE MARKET PRICES FOR BUTADIENE ARE LOW USE OF BUTADIENEAS FEEDSTOCK FOR THE PRODUCTION OF HIGHGRADE CHEMICALS IS VERYINTERESTING4HETELOMERIZATIONREACTIONOFBUTADIENEWITHOPHTHALICACID YIELDS A MIXTURE OF LINEAR AND BRANCHED ESTER ISOMERS ASSHOWN IN &IGURE !FTER HYDROGENATION OF DOUBLE BONDS IN THEALKENEGROUPSTHEPRODUCTHASPOTENTIALUSEASPLASTICIZER4HEREACTIONSAREHOMOGENEOUSLYCATALYZEDBYAPALLADIUMnLIGANDCOMPLEX INAPOLARORGANICSOLVENT4HEFORMATIONOF THEPRODUCTPROCEEDS THROUGHMONOESTER SPECIES 4HIS HAS BEEN CONlRMEDBY A COMBINATION OF EXPERIMENTATION AND KINETIC MODELING !SIMPLIlEDREACTIONSCHEMEISSHOWNIN&IGURE
4HETELOMERIZATIONOFBUTADIENEWITHOPHTHALICACID
/NE OF THE OBJECTIVES OF THIS RESEARCH PROJECT WAS TO SPEEDUP THE COURSE OF DEVELOPMENT OF THE NEW PRODUCT AS MUCH ASPOSSIBLE4HEREFOREKINETICMODELINGWASSTARTEDCONCURRENTLYWITHTHEEXPERIMENTALOPTIMIZATIONOFTHEREACTIONSYSTEM4HERESULTSOFTHREEEXPERIMENTSINWHICHTHEBUTADIENEOPHTHALICACIDRATIOWASVARIEDANDOTHERPARAMETERSKEPTCONSTANTWEREUTILIZEDTOEVALUATE PROPOSED KINETICMODELS#RITERIA FOR THE SELECTION OF THEMOSTAPPROPRIATE MODEL WERE BEST lT FOR THE CONVERSION OF OPHTHALICACIDANDSELECTIVITIESOF THEPRODUCTSUSINGAMINIMUMNUMBEROFPARAMETERSMINIMIZETHEPRODUCTOFTHEWEIGHTEDSUMOFSQUARESOFRESIDUALSANDTHENUMBEROFPARAMETERS
&IGURE5PGRADINGOFBUTADIENE
&IGURE3IMPLIlEDREACTIONSCHEME
(#//(
#//(
#//#(
#//#(
#//#(
#//#(
!CKNOWLEDGMENT4HEAUTHORSAREGRATEFULTO*OHAN(OORN$3-2ESEARCH0/"OX-$'ELEEN4HE.ETHERLANDSFORSUPPLYINGTHISCASESTUDY
CONCERNINGTHEADSORPTIONMODEINASELECTIVEHYDROGENATIONPROCESSISSHOWNIN)NTERMEZZO4HE IMPORTANCE OF USING PROPER STATISTICAL TOOLS IN
THE KINETIC INVESTIGATION SHOULD NEVER BE UNDERESTIMATEDEITHERFORREASONSOFTIMEEFFECTIVENESSORCONlDENCEINTHERESULTING MODEL 7HILE AT THE BASIC LEVEL THIS CAN SIMPLYBE THE EXPERIMENTAL DESIGN FOLLOWED BY USE OF A SUITABLEOPTIMIZATIONPACKAGEFORPARAMETERESTIMATIONITMAYALSOINCLUDEMATHEMATICALTRANSFORMATIONOFTHEMODELEQUATION
INORDER TOGIVEMORE RELIABLElTTING )NTERMEZZO SHOWSHOW ,((7 KINETIC EXPRESSIONS MAY BE REPARAMETERIZEDBY MATHEMATICALLY REMOVING ALL KINETIC PARAMETERS FROMTHE NUMERATOR 4HIS REPARAMETRIZATION SUPPRESSES THEINTERDEPENDENCYBETWEENTHEPARAMETERSANDTHUSENHANCESTHElTTINGPROCESS
+INETICMODELINGGOODPRACTICE)NORDER TO IMPROVE THE EFlCIENCY AND ACCURACYOF KINETICMODELING A SERIES OF RECOMMENDATIONS CAN BE GIVEN OFWHICHSOMEWEREILLUSTRATEDORMENTIONEDPREVIOUSLY
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
3TARTYOURKINETICSSTUDIESEARLYINTHEDEVELOPMENTPROGRAMFORMAXIMUMADVANTAGE 4HETELOMERIZATIONOFBUTADIENEWITHOPHTHALICACID
&IGURE%XPERIMENTSYMBOLSANDMODELLINESFORTHREESELECTEDCOMPONENTS
4HEPROCEDURERESULTEDINAMODELTHATCONSISTSOFVERYSIMPLERATEEXPRESSIONS7HENTHEREACTANTSAREDENOTEDBY"BUTADIENE0!OPHTHALICACID-LINEARLINEARMONOESTERINTERMEDIATEAND-BRANCHEDBRANCHED MONOESTER INTERMEDIATE THE RATE EQUATIONS ARE GIVENBYRK;"=;0!=RK;"=;0!=RK;"=;-LINEAR=RK;"=;-LINEAR=RK;"=;-BRANCHED=RK;"=;-BRANCHED=RK;"=
!N EXAMPLE OF THE COMPARISON BETWEEN EXPERIMENT AND MODELCALCULATIONSAFTEROPTIMIZATIONOFTHEKINETICPARAMETERS ISGIVENIN&IGURE )N THIS lGURE OPHTHALIC ACID ONE OF THE INTERMEDIATESAND THE LINEARPRODUCTARESHOWN INDIMENSIONLESSCONCENTRATIONSASAFUNCTIONOFTIMEALLCONCENTRATIONSHAVEBEENNORMALIZEDTOTHEINITIALOPHTHALICACIDCONCENTRATION
4HEEFFECTOFCATALYSTCONCENTRATIONISINCLUDEDINTHERATECONSTANTSFORA CERTAIN RANGEOF CONCENTRATIONS4HE ROLEOF THECATALYST INDETERMININGSELECTIVITIESANDINHIBITIONEFFECTSBYBYPRODUCTSSUCHASOCTATRIENEWASNOTCONSIDEREDINTHEMODEL3TATISTICALANALYSISOF THEMODELSHOWED THAT THEACCURACYOF THEPARAMETERSWOULDHAVETOBE IMPROVED INORDER TO INCREASETHERELIABILITYOFAPLANTSCALEREACTORDESIGN4HESIMPLEMODELOBTAINEDFROMEXPERIMENTSTHATWERECONDUCTEDFOR PURPOSES OTHER THAN KINETIC MODELING IS SUITABLE FOR TWOREASONSv )NTEGRATION IN A REACTOR MODEL FOR mOW SHEET CALCULATIONS INORDERTOMAKEPRIMARYECONOMICEVALUATIONSv 3TARTING POINT FOR THE DEVELOPMENT OF A MORE SOPHISTICATEDKINETICMODELNEEDEDFORAlNALREACTORDESIGN
4HECONTINUATIONOFTHEDEVELOPMENTOFTHEKINETICMODELINCLUDEDEXPERIMENTSATVARYINGTEMPERATURESANDSPECIlCALLYIDENTIlCATIONOFPRODUCTINHIBITIONADDINGOCTATRIENEORONEOFTHEESTERPRODUCTSTOTHESTARTINGMIXTURE
!CKNOWLEDGMENT4HEAUTHORSAREGRATEFULTO*OHAN(OORN$3-2ESEARCH0/"OX-$'ELEEN4HE.ETHERLANDSFORSUPPLYINGTHISCASESTUDY
v 3TRIVEFORINTRINSICKINETICSRATHERTHANAPPARENTKINETICSWHERE THE TRANSPORT EFFECTS AND INTRINSIC KINETICS ARELUMPED 4HIS STRONGLY IMPROVES THE UNDERSTANDING OFTHEPHYSICOCHEMICALBACKGROUNDOFTHESYSTEMANDMAYGIVEINSIGHTINTOUNUSUALORUNEXPECTEDEFFECTSANDALSOIMPROVESTHERELIABILITYANDACCURACYOFTHEMODELWHENEXTRAPOLATEDv 4HEEXPERIMENTALREACTORNEEDNOTNECESSARILYBEASMALLSCALE COPY OF THE INDUSTRIAL REACTOR 4HE USE OF TRICKLEBEDSANDmUIDBEDSSHOULDPREFERABLYBEAVOIDED
v $ETERMINEINADVANCEWHATKINETICINFORMATIONISREALLYNEEDEDTAKINGINTOACCOUNTTHERESOURCESAVAILABLEv !LWAYS SEARCH FOR INFORMATIONONCOMPARABLECHEMICALSYSTEMS "ESIDES LITERATURE ONE SHOULD NOT FORGET TOCHECKIFTHEREIS INFORMATIONAVAILABLEINTHELABORATORYFROMEARLIERRESEARCHv 5SEMORETHEORETICALLYBASEDMODELSIFRELIABILITYOFTHEKINETICSISREQUIREDFOREXTRAPOLATIONv !VOID ESTIMATING A LARGE NUMBER OF DIFFERENT KINETICPARAMETERS FROM A SMALL EXPERIMENTAL DATA SET !N
TIMEINMINUTES
CONCENTRATIONDIMENSIONLESS
/(/
/
/
/
/
//#//(
#//(
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
+INETICMODELINGMAYCONTRIBUTETONEWINSIGHTSINREACTIONMECHANISMSANDREACTIONINTERMEZZO
4HEREACTIONNETWORKSHOWNIN&IGURECANDESCRIBETHESELECTIVEHYDROGENATIONOFCINNAMALDEHYDETOCINNAMYLALCOHOL4HEDEVELOPMENTOFTHECONCENTRATIONSOFTHEVARIOUSCOMPONENTSIN A BATCH REACTORMAY BEWELL DESCRIBED BY AMODEL WITH lRSTORDERREACTIONSTEPSLIKEIN)NTERMEZZOFOR($.INCLUDING@DIRECTREACTIONSFROMREACTANTTOINTERMEDIATEANDENDPRODUCTS4HISISEXAMPLIlEDBY&IGUREWHERETHELINESDRAWNARETHEKINETICMODELPREDICTIONSFORLOWCONCENTRATIONSOFCINNAMALDEHYDEINTOLUENE;XIV=(OWEVERATHIGHERCONCENTRATIONS^MOLLTHESELECTIVITYFORTHEDESIREDPRODUCTCINNAMYLALCOHOLINCREASESCONSIDERABLYWHILEATTHESAMETIMETHEABSOLUTECONVERSIONRATEOFCINNAMALDEHYDEISABOUTTHESAME4HISSELECTIVITYCHANGECANINNOWAYBEPREDICTEDBYTHELOWCONCENTRATIONDERIVEDKINETICMODEL;XV=
SEQUENCES3ELECTIVEHYDROGENATIONOFCINNAMALDEHYDETOCINNAMYLALCOHOL
APPROPRIATEUSEOFSTATISTICALTOOLSFACILITATESTHEREJECTIONOFKINETICMODELSCONTAININGTOOMANYPARAMETERSv $ElNESEVERALDIFFERENTKINETICMODELSTHATMAYDESCRIBETHESYSTEMANDMODELSELECTIONCRITERIATOALLOWMAKINGACHOICEBETWEENTHESEMODELSv $ESIGN ADDITIONAL EXPERIMENTS WITH TWO GOALS I TOFACILITATE THE SELECTION OF THE @BEST MODEL AND II TOIMPROVETHEACCURACYOFTHEKINETICPARAMETERSv !PPLY PROPORTIONAL WEIGHTING IN ORDER TO ACHIEVE ANEQUALLYGOODDESCRIPTIONOFSMALLEXPERIMENTALRESPONSEVALUESASFORLARGEEXPERIMENTALRESPONSEVALUESv !RRHENIUS AND ,((7 EXPRESSIONS CAN BENElCIALLYBE REPARAMETERIZED;= 4HIS STRONGLY REDUCES THEINTERDEPENDENCYBETWEENACTIVATIONENERGYANDTHEPREEXPONENTIALFACTORWHICHENHANCESTHElTTINGPROCEDURE3EE)NTERMEZZOFORMOREDETAILS
&INALLY THE RESEARCHER IN KINETICS HAS TO CHOOSE A SUITABLESOFTWARE PACKAGE TO PERFORM THE PARAMETER ESTIMATION"ECAUSESEVERALDIFFERENTPACKAGESARECOMMERCIALLYAVAILABLEWITH STRONGLY VARYING CAPACITIES USER INTERFACES ANDVERSATILITYITISDIFlCULTTOCHOOSETHEMOSTSUITABLEPACKAGE! FUTURE PAPER;= WILL FOCUS ON ASPECTS TO BE CONSIDEREDBEFOREMAKINGACHOICEOFlTTINGSOFTWARE
#ONCLUSIONS+INETICSSTUDIESININDUSTRYAREPRAGMATIC%XPERIMENTSAREEXPENSIVE AND THERE MUST BE A lNANCIAL JUSTIlCATION FORKINETICSTUDIES4HEREALSONEEDSTOBEATECHNICALJUSTIlCATIONFORTHEMODELANDTHEOVERRIDINGREQUIREMENTISTOMAINTAINSIMPLICITY4HEMAJORITYUSAGEOFKINETICMODELSISINPROCESSNOTCATALYSISRESEARCH7HILE INDUSTRYWOULD LIKETOOBTAININTRINSICKINETICSMODELSBASEDONMECHANISTICCONSIDERATIONS
)N VIEW OF THE SAME CONVERSION RATE IT IS SPECULATED THATTHE ADSORPTION MODE AT HIGH CONCENTRATIONS DIFFERS FROM LOWERCONCENTRATIONS COMPARABLE TO THE ADSORPTION OF SURFACTANTS INTHE FORM OF MICELLES )N THIS SENSE THE CINNAMALDEHYDE ADSORBSPERPENDICULARTOTHE0TSURFACEWITHTHEAROMATICRINGSINAPARALLELARRANGEMENT hSELFASSEMBLINGWHICH ISSCHEMATICALLYDEPICTEDIN &IGURE .OW THE CARBONYLIC FUNCTIONALITY WILL BE MOST PRONETO HYDROGENATION ,ITERATURE ON THIS TYPE OF ORDERED ADSORPTION ISSCARCE BUT SOME EXAMPLES WITH AROMATIC MOLECULES HAVE BEENREPORTED;XVI=4HISSTRESSESTHEIMPORTANCETHATINSOMECASESEVENTHEADSORPTIONMODESHOULDBEINCORPORATEDINAKINETICMODELOTHERWISEREACTIONSELECTIVITIESWILLNOTBEPREDICTED
CINNAMALDEHYDE#!, CINNAMYLALCOHOL#/, BMETHYLSTYRENE
HYDROCINNAMALDEHYDE(#!, PHENYLPROPANE00PHENYLPROPANOL(#/,
CYCLOHEXYLPROPANOL#(0
&IGURE#INNAMALDEHYDEHYDROGENATIONREACTIONNETWORK
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
+INETICMODELINGMAYCONTRIBUTETONEWINSIGHTSINREACTIONMECHANISMSANDREACTION
&IGURE3PECULATEDADSORPTIONMODEOFCINNAMALDEHYDEMOLECULESONTHECATALYST
SEQUENCES3ELECTIVEHYDROGENATIONOFCINNAMALDEHYDETOCINNAMYLALCOHOL
ITISRARELYEXPEDIENTSOTODODUETOREASONSOFCOSTANDMANHOURSASWELLASELAPSEDTIMEANDECONOMICANDTECHNICALJUSTIlCATION"EFORESETTINGOUTONAMODELINGEXERCISEITISESSENTIAL
TO THINK CAREFULLY ABOUT THE REQUIREMENTS 7HAT WILL THEMODELBEUSED FOR!NDBYWHOM)SA FULLKINETICMODELWHAT IS ACTUALLY NEEDED7ILL THERE BE A NEED FOR EXTRAPOLATION REGARDING OPERATING DOMAIN AS WELL AS SCALE )NASSEMBLINGTHEMATHEMATICALEXPRESSIONEVERYEFFORTSHOULDBEMADE TOOBTAINPHYSICOCHEMICAL BASIS"EWAREOF OVERPARAMETERIZATION AND MAKE MAXIMUM USE OF APPROPRIATESTATISTICAL TOOLS )N DOING ALL THIS IT IS WORTH BEARING INMINDTHATPROCESSMODELSDONOTNEEDDETAILEDKINETICSBUTRATHERARELIABLERATEMODEL%VENWITHTHISTHEINmUENCEOF
EXTERNALFACTORSCHANGESWITHSCALEPARTICULARLYTHEEFFECTSOFMACROMIXINGANDTRANSPORT
&UTUREACTIVITIES)N CONSIDERING WHAT THE FUTURE HOLDS FOR KINETICS ORMOREPRECISELYWHATARETHEMAINAGENDAITEMSFORKINETICSRESEARCH IT IS WORTH RETURNING AGAIN TO THE INDUSTRIALSURVEY4HISALSOINQUIREDASTOOPINIONSONTHEASPECTSOFKINETICS THAT MOST URGENTLY REQUIRE IMPROVEMENTS 4HREEAREASWERECOMMONLYCITEDI )MPROVEMENTS IN THE ACQUISITION OF KINETIC DATA SINCETHISISCONSIDEREDTOOCOSTLYANDTIMECONSUMING
II 4HEREISCONSIDERABLEDIFlCULTYINTHEDETERMINATIONANDSUBSEQUENTAPPLICATIONOFKINETICSFORTHECASEOFUNSTABLEORVARIABLECATALYSTPERFORMANCEEGDEACTIVATION
0T
#
/
#
#
#
/
#
#
#
/
#
#
#
/
#
#
#
/
#
#
#
/
#
#
2ESIDENCETIMEMIN
#MOLL
#!,
#/,(#!,
(#/,
#(0
00
&IGURE%XPERIMENTALRESULTSCINNAMALDEHYDEHYDROGENATION
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
3TATISTICALTECHNIQUESHELPTOPERFORMEXPERIMENTALDESIGNANDTOlNDOPTIMALKINETICINTERMEZZO MODELS!CASESTUDYOFTHESELECTIVEREDUCTIONOF./BY.(
&IGURE$IFFERENTIALREACTORMODEL
./
./OUT.(
.( OUT
: :,
$ESIGN OF EXPERIMENTS IS A COLLECTION OF STATISTICAL TECHNIQUESEMPLOYED FOR SYSTEMATIC EXPERIMENTATION AND OPTIMAL MODELANALYSIS4HISAPPLICATIONILLUSTRATESTHEUSEOFEXPERIMENTALDESIGNFORMODELBUILDINGANDANALYSISFORTHESELECTIVECATALYTICREDUCTIONOF./BY.(
%XPERIMENTALSETUP4HEEXPERIMENTSFORTHEDETERMINATIONOFTHEINTRINSICKINETICSHAVEBEEN PERFORMED IN A TUBULAR PACKED BED REACTOR WHICH CAN BEMODELED USING THE PLUG mOW REACTORMODEL AS SHOWN IN &IGURE4HESEPARATEADSORPTIONANDSURFACEREACTIONSTEPSHAVEBEENLUMPEDINTOONEOVERALLREACTIONDESCRIBINGTHE./CONVERSION./.(/m.(/%ACHEXPERIMENTCOVERSASPECIlCCOMBINATIONOFMOLARFRACTIONS./.((/AND/ATTHEREACTORINLETTHEREACTORTEMPERATUREAND THE SPACE VELOCITY ! SMALL CATALYST PARTICLE SIZE HAS BEENSELECTED TO AVOIDMASS TRANSFER LIMITATIONS DUE TO PORE DIFFUSIONEFFECTS!TTHEREACTOROUTLETTHEMOLARFRACTIONS./AND.(HAVEBEENMEASURED
2ATEEXPRESSIONS!CCORDING TO THEDIFFERENTASSUMPTIONSSEVERAL RATEEXPRESSIONSFOR THESURFACE REACTIONHAVEBEENPROPOSED )N&IGURE SOMEREACTIONRATEEXPRESSIONSAREDISPLAYED4HECONSTANTSABCANDDAPPLYTOTHEPOWER LAWMODEL4HERATECONSTANT ISGIVENBYK4HEPARAMETERS+./+.(AND+(/ARETHEADSORPTIONCONSTANTS4HE RATEEXPRESSIONSDEPENDON THE LOCALPARTIALPRESSURES0./0.(0/AND0(/!TGIVENINLETCONCENTRATIONSTHE./AND.(OUTLETVALUESARECOMPUTEDUSINGTHEREACTORCONTINUITYEQUATIONSFOR.(AND./4HEPARAMETERSAREADJUSTEDSUCHTHATTHESUMOF
0OWERLAW
%LEY2IDEAL
RK
+.(P.(+./P./P/ +.(P.(+(/P(/
&IGURE3AMPLEOFSELECTEDMODELS
,ANGMUIRn(INSHELWOOD
RK +.(P.(+./P./P/
+./P./+.(+.(P.(+(/P(/
ARKP./P.(P(/P/B C D
D
D
"!
0ARALLELEXPERIMENTATIONRIGWITHREACTORSFORGASPHASEREACTIONSOVERAFIXEDBED
%NDEAVORUNITWITHREACTORSFORGASLIQUIDSLURRYREACTIONSEGHYDROGENATION
EIGHTINDIVIDUALINJECTORSWITHINDEPENDANTCONTROLOFTEMPERATUREPRESSUREREAGENTADDITIONANDGASDELIVERY
ALLFUNCTIONSCONTROLLEDVIASIMPLEKEYPAD
&IGURE(IGHnTHROUGHPUTEXPERIMENTATIONEQUIPMENTREPRODUCEDCOURTESYOFAARGONAUTTECHNOLOGIESBZETONALTAMIRA
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
3TATISTICALTECHNIQUESHELPTOPERFORMEXPERIMENTALDESIGNANDTOlNDOPTIMALKINETIC MODELS!CASESTUDYOFTHESELECTIVEREDUCTIONOF./BY.(
SQUAREDRESIDUALS332THEDIFFERENCESBETWEENTHEMEASUREDANDTHECOMPUTED./AND.(OUTLETVALUESISMINIMIZED
%XPERIMENTALDATA&IGUREDISPLAYSTHELEVELSOFTHEINLETCONCENTRATIONS4HEVALUESHAVEBEENARRANGEDUSINGA CENTRAL COMPOSITE DESIGN CONSISTINGOF CORNERS OF THE CUBE LOWHIGH VALUES STAR POINTS ORANGEOUTSIDE THE CUBE AND ONE OR MORE REPLICATES IN THE CENTER !COMPOSITEDESIGNHASBEENCHOSENASITISSUITABLEFORDETERMINATIONOF THE NONLINEAR EFFECTS ARISING FROM THE RATE EXPRESSIONS AND THESOLUTIONOFTHEDIFFERENTIALMASSBALANCES
&IGURE#ENTRALCOMPOSTEDESIGN
0ARAMETERESTIMATION&OR ALL SELECTEDMODELS THE LEASTSQUARES ESTIMATES OF THE RATECONSTANTANDTHEADSORPTIONCOEFlCIENTSHAVEBEENlTTED(OWEVERIN MANY CASES EXTREMELY LARGE STANDARD ERRORS AND MUTUALCORRELATIONS OF THE ESTIMATED PARAMETERS WERE EXPERIENCED )NTHE,ANGMUIRn(INSHELWOODMODELTHECORRELATIONSBETWEENKAND+./ANDBETWEEN+.(AND+(/WEREANDRESPECTIVELY4HIS INDICATES ILLCONDITIONEDBEHAVIOROF THEESTIMATIONPROBLEMINCLUDING VERY SENSITIVE AND LESS RELIABLE PARAMETER RESULTS5SINGTHEhPARAMETERINDENOMINATORvPRINCIPLESTHESEINACCURATERESULTS HAVE BEEN CONSIDERABLY IMPROVED !FTER DIVISION OF THENUMERATOR AND THE DENOMINATOR OF THE ,ANGMUIRn(INSHELWOODRATEBYTHECOMMONPARAMETERPRODUCTK+.(+./ANDREARRANGINGTHE PARAMETERS IN THE DENOMINATOR NEARLY ALL HIGH CORRELATIONSAND HIGH STANDARD ERRORS DISAPPEARED 4HIS REPARAMETERIZATIONPRODUCESA@CLOSETOLINEARMODELBYCLEARINGOFFCONSTANTSINTHENUMERATOROFTHERATEEXPRESSION
-ODELSELECTION)NORDERTOSELECTTHEBESTMODELAFURTHERMODELDISCRIMINATIONWASCARRIEDOUT&IGUREDISPLAYSTHEREACTIONRATESOFFOURRIVALMODELSSEVERAL FORMS OF ,ANGMUIRn(INSHELWOOD INCLUDING AMODEL WITHSURFACEDISSOCIATION CALCULATEDWITHAHIGH(/ FRACTIONOFAT THE REACTOR INLET (ARDLY ANY STATISTICALLY SIGNIlCANT DIFFERENCEIS EXPERIENCED &IGURE DISPLAYS THE RATES COMPUTED WITH THESAME PARAMETERS AT A MUCH LOWER (/ CONTENT OF 4HEDIFFERENCES BETWEEN THE RATE VALUES ARE EVIDENT PARTICULARLY ATHIGH ./ CONCENTRATIONS !DDING EXPERIMENTS CARRIED OUT AT LOW(/CONCENTRATIONINCREASEDTHEDISCRIMINATIVEPOWERBETWEENTHERELEVANTMODELS IN THESAMEWAYOTHEREXPERIMENTALCONDITIONS
III 4HERE IS CONSIDERABLE OPPORTUNITY TO IMPROVE THE USERFRIENDLINESSOFSOFTWAREFORMODELINGOFREACTORSFORTHEREGRESSIONOFKINETICDATATORATEEXPRESSIONSANDFORITSAPPLICATIONTOEXPERIMENTALDESIGN
4HEMAJORITY OF THE RESPONDENTS STATED THAT THE PROBLEMSINDICATED SHOULD BE SOLVED BY COOPERATION AND THIS OFCOURSEWASTHEIMPETUSTHATLEDTOTHEFORMATIONOF%UROKIN)NTERMEZZO4HEABOVE LISTESSENTIALLY RELATES TOSIMPLYIMPROVING THE WAY WE USE THE CURRENT TOOLS AND THEIRINCREMENTALDEVELOPMENT4HEALTERNATEQUESTIONISWHATARETHEPOTENTIALMAJORSTEPCHANGESTHATAREGOINGTOIMPINGEONKINETICSRESEARCHINTHEFUTURE4AKINGTHEMEDIUMANDLONGTERM PERSPECTIVES AS ONE HERE ARE SOME THOUGHTS ASTOWHAT THE FUTUREMIGHTBRINGORWHATWE INVOLVED INKINETICSRESEARCHOUGHTTOBECONSIDERINGv 3OFTWARE TOOLS SIMULATION REGRESSION EXPERIMENTALDESIGN WILL BE IMPROVED 4HIS WILL RELATE NOT ONLYTO IMPROVED USERFRIENDLINESS AND CALCULATION ROUTINESLEADING TO REDUCED COMPUTATIONAL TIMES BUT ALSO TO
DEVELOPMENTS IN STATISTICAL SEARCH AND OPTIMIZATIONTECHNIQUESv -OLECULARMODELINGCANBEEXPECTEDTOCONTRIBUTEMORETO USEFUL MECHANISTIC INFORMATION AND TO ESTIMATIONOF INITIAL PARAMETER VALUES 4HIS RELATES TO THE RAPIDDEVELOPMENTS IN THE THEORETICAL CHEMISTRY AND COMPUTATIONALTOOLSASWELLASTOTHEDEVELOPMENTINASSOCIATEDCOMPUTER HARDWARE 4HE LEADING COMPANIES ARE NOWTARGETINGINCREASEDCOMPUTATIONALPOWERONTHEDESKTOPTOFACILITATETHISv (IGH THROUGHPUT EXPERIMENTATION HAS LARGELY BEENASSOCIATED WITH COMBINATORIAL CHEMISTRY DISCOVERYAND SCREENING 4HE POTENTIAL IMPACT OF THE GROSSPARALLELIZATION OF EXPERIMENTAL EQUIPMENT ON KINETICMEASUREMENTSSHOULDNOTHOWEVERBEUNDERESTIMATED;=0ARALLELMICROREACTORUNITSAREINUSEININDUSTRYANDARENOWBECOMINGCOMMERCIALLYAVAILABLE&IGURESHOWSTWOEXAMPLESOFhOFFTHESHELFvPARALLELSCREENINGUNITS+INETIC DATAMAY BEMORE RAPIDLYMEASURED BUT THIS
./.(
(/
/
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
THEN PUTS THE EMPHASIS ON THE STATISTICAL TOOLS TO SETTHEEXPERIMENTALDESIGNANDPROCESSTHEACQUIREDDATA4HE THEORY IS THAT COMBINATORIAL OR SIMILARDISCOVERYWILL INCREASE THENUMBEROFNEWPRODUCTS AND SO THISINCREASE IN THE EFlCIENCY OF KINETICS RESEARCH WILL BEREQUIREDSIMPLYTOKEEPPACEv .ONSTATIONARYMETHODSSUCHASTEMPERATUREPROGRAMMEDREACTIONANDTEMPORALANALYSISOFPRODUCTSARECURRENTLYQUITE WIDELY USED TO OBTAIN MECHANISTIC INFORMATIONBUT AS YET THEOUTPUT ISUSED IN APRIMARILYQUALITATIVEFASHION AND RELATIVELY LITTLE QUANTITATIVE INFORMATION ISOBTAINED5NSTEADYSTATETECHNIQUESHAVETHEBENElTTHATDATAISACQUIREDMUCHMORERAPIDLY4HECHALLENGEISTO
UNDERSTANDHOWDATAMEASUREDINATRANSIENTCONDITIONCANBEAPPLIEDQUANTITATIVELY
4HOSE IN THE %UROKIN CONSORTIUM AND THEIR ACADEMICPARTNERSWILLBEACTIVELYADDRESSINGTHESEISSUESOVERTHENEXTFEWYEARS4HECHALLENGESSHOULDNOTBEUNDERESTIMATED)TWILL REQUIRE MAJOR EFFORT AND INNOVATION TO ACHIEVE THESEGOALS
&URTHERREADING4HERE EXIST MANY TEXTBOOKS CONCERNING THE THEORETICALBACKGROUNDOFREACTIONKINETICS4HE FOLLOWING BOOKS ARE SUITABLE FOR A GENERAL AND
BASIC INTRODUCTIONOF CHEMICAL KINETICSHOMOGENEOUS ANDHETEROGENEOUS CATALYSIS AND THE THERMODYNAMICS RELATEDWITHTHESE"OUDART;="OUDARTAND$JEGA-ARIADASSOU;=
&IGURE2ATEVALUESATA(/CONTENTOF
MODELMODELMODELMODEL
P./
2EACTIONRATE
DISPLAYING LARGE DIVERGENCE BETWEEN THE MODELS HAVE BEENADDED TOALLOW FOROPTIMALDISCRIMINATIONA FORMOFSEQUENTIALEXPERIMENTAL DESIGN !S A LAST STEP IN THE ANALYSIS OPTIMALPARAMETERS OF THE BEST MODEL HAVE BEEN RElTTED USING ALL THEDATA
MODELMODELMODELMODEL
P./
2EACTIONRATE
&IGURE2ATEVALUESATA(/CONTENTOF
#ONCLUSION5SINGSTATISTICALTECHNIQUESOPTIMALMODELANALYSISANDDESIGNFORTHESELECTIVECATALYTICREDUCTIONOF./BY.(HASBEENPERFORMED3PECIAL ATTENTION HAS BEEN PAID TO THE STATISTICAL DESIGN OF THEEXPERIMENTS EFlCIENT REPARAMETERIZATION OF THE MODELS AND THEDESIGNFOROPTIMALMODELDISCRIMINATION
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
7HEREK REACTIONRATECOEFFICIENTKO PREEXPONENTIALFACTOR
4 THEREPARAMETERIZEDREACTIONTEMPERATUREIN+CALCULATEDFROMTHEREACTIONTEMPERATURE4IN+ACCORDINGTO
4REF ANARBITRARILYCHOSENREFERENCETEMPERATUREWITHINTHEEXPERIMENTALTEMPERATUREWINDOW
KREF KOEXP
%A2q4REF
444
REF
KKOEXP
%A2q4
/RIGINAL!RRHENIUSEXPRESSION
KKREFEXP
%A2q4
2EPARAMETERIZED!RRHENIUSEXPRESSION
4HIS REPARAMETERIZATIONSTRONGLY REDUCES THE INTERDEPENDENCYBETWEENACTIVATIONENERGYANDTHEPREEXPONENTIALFACTORWHICHENHANCESTHElTTINGPROCEDURE%STIMATINGTHELOGOFKREFINSTEADOFKREFITSELFMAYFURTHERFACILITATETHEPARAMETERESTIMATIONPROCEDUREBECAUSETHISSTRONGLYREDUCESTHEDIFFERENCEINUNCERTAINTYRANGESOFBOTHPARAMETERS
!CKNOWLEDGEMENT4HEAUTHORSAREGRATEFULTO3JOERDVANDER7ALFORMERLY3HELL2ESEARCHAND4ECHNOLOGY#ENTRE!MSTERDAM4HE.ETHERLANDSFORSUPPLYINGTHISCASESTUDY
RK+!P!+"P"+!P!+"P"
/RIGINAL,((7EXPRESSION
RP!P"
K+!+"K+"K+!2EPARAMETERIZED,((7EXPRESSION
P!P"
&ROMENTAND"ISCHOFF;=AND+APTEIJNAND-OULIJN;=4HESEBOOKS COVER THE RANGE FROM THE FUNDAMENTALSOF CHEMICALKINETICSUPTOMODELINGOFREACTORS!NEXTENSIVEANDUSEFULPAPERCONCERNINGTHEMODELINGOFCATALYTICKINETICSISGIVENBY&ROMENTAND(OSTEN;=3OURCESOFMORE THOROUGH FUNDAMENTALBACKGROUNDOF
KINETICSOFHETEROGENEOUSLYCATALYZEDREACTIONSALSODElNEDAS MICROKINETICS ARE $UMESIC ET AL ;= :HDANOV;= 6AN3ANTEN;= AND 'OLDEN AND-ANION;= ! FREQUENTLY USEDMETHOD FORMICROKINETICMODELING IS THE"ONDORDER CONSERVATIONn-ORSEPOTENTIAL APPROACH "/#n-0 APPROACHSEE 3HUSTOROVICH; = AND "ELL;= "ENZIGER;= DESCRIBESSEVERALMETHODSFORESTIMATINGREACTIONENERGETICSONMETALSURFACES+ANGAND7EINBERG;=GIVEANOVERVIEWOFMETHODSFORMODELINGOFSURFACERATEPROCESSES%STIMATIONSOFHEATSOF CHEMISORPTION OF GASES ON METAL SURFACES CAN BE DONEUSINGTHEGENERALRULESDElNEDBY4ANAKAAND4AMARU;=
'UIDELINESFOR2EPARAMETERIZATIONv 2EPARAMETERIZE!RRHENIUSEXPRESSIONSACCORDINGTO v 2EPARAMETERIZE ,((7TYPE EXPRESSIONS BY REMOVING THE
KINETICPARAMETERSFROMTHENUMERATORACCORDINGTOFOREXAMPLE
)NSTEAD OF K +A AND +" THE COMBINATIONS K+!+" K+"AND K+! ARE ESTIMATED WHICH ALSO ENHANCES THE lTTINGPROCEDURE
-
%UROKIN
#HEMICALREACTIO
NKINETICSINP
RACTICE
0ROFDR IR'UY"-ARINIS FULL PROFESSOR OF #HEMICAL%NGINEERING AT THE 5NIVERSITY OF'ENT "ELGIUM (E RECEIVED HISDEGREEFROMTHE5NIVERSITYOF'ENTIN WHERE HE ALSO OBTAINEDHIS 0H$ IN !FTER A POSTDOCTORALSTAYINAT#ATALYTICA!SSOCIATESAND3TANFORD5NIVERSITYHEOBTAINEDTENUREATTHE5NIVERSITY
OF'ENTIN(ETOOKAPOSITIONOFFULLPROFESSORINATTHE%INDHOVEN5NIVERSITYOF4ECHNOLOGY4HE.ETHERLANDSWHERE HE TAUGHT ABOUT CHEMICAL REACTORS )N HERETURNED TO 'ENT AS DIRECTOR OF THE ,ABORATORIUM VOOR0ETRO