2004年化学反应工程期末考试参考答案A.Chooseoneofthefouranswers(5pointsforeachone,25pointsintotal)1.Activationenergymightbetakenasanindicationof(C)Athedifficultyofareaction.Bthecomplicacyofareaction.Cthetemperaturesensitivityofareaction.Dtheenergyofthereactantabsorbedorexhausted.2.Basedonwhatmodelandboundaryconditions,thedimensionlessmeanresidencetime(C)ATankinseriesmodelBThedispersionmodelwithclosedboundaryconditionsCThedispersionmodelwithopenboundaryconditionsDNone3.Withinthreecoefficientsconcerningaboutdiffusion,①dispersioncoefficient,②moleculardiffusioncoefficientand③Knudsendiffusivity,ifwesortthemfromlargetosmall,thesuitableorderis(D)A③>②>①B③>①>②C②>①>③D①>②>③4.ForthereactionA→R,secondorderkinetics,proceedsinabatchreactor,thefinalconcentrationofAis0.01mol/l.IftheinitialconcentrationCA0is1mol/l,ittakes283[sec].IftheinitialconcentrationCA0is5mol/l,ittakes285[sec].Howlongweneediftheinitialis5mol/landfinalis1mol/l?(A)A2[sec]B10[sec]C>10[sec]DBetween2and10[sec]5.Agas-phasereaction2A+B→C,startingwith50%A,25%Band25%inert,theexpansionfactorεAis(C)A-1B1C-0.5D0.5B.Aliquid-phasereactionA+B→productsisconductedinanisothermalbatchreactor.Thereactionisfirstorderwithrespecttoeachreactant,第1页withkA=0.025Lmol-1s-1,CA0=0.5molL-1,andCB0=1.0molL-1.Determinethetimerequiredfor75%conversionofA.(20points)C.Foramixedflowreactorofvolume6m3operatingwithasteady-state(liquid)feedrateof0.4m3min-1,whatfractionoftheexitstream(i)isofagelessthan10min?(ii)hasbeeninthetanklongerthan30min?(20points)D.AreactionA→Ristotakeplaceonaporouscatalystpellet(dp=6mm,De=10-6m3/m.cat.s).Howmuchistherateslowedbyporediffusionalresistanceiftheconcentrationofreactantbathingtheparticleis100mol/m3andthediffusion-freekineticsaregivenby(20points)第2页Chooseoneofthefollowingtwoproblemstosolveasyoulike,don’tchooseboth.E.Todeducetheresidencetimedistributionforamixedflowreactor.(15points)F.Thereactiontakesplaceinamixedflowreactor.DeterminetheoptimalspacetimeandthemaximalconcentrationofmainproductR.(15points)第3页第4页
