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The_112

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The_112The,the

    The

ChineseJ.Chem.Eng.,11(5)608610(2003)

    ;RESEARCHNoTES

    ;ThePreparationof2Chloro5chloromethylpyridineinan

    ;AirliftLoopReactor

    ;WENJianping(闻建平),WANGChanglin(~长林)andQIAO

    ;SchoolofChemicalEngineeringandTechnology,TianjinUniversity,Tianjin300072

    ;AbstractAnewprocessforthedirectchlorinationof2-chloro-5methylpyridinetoyield2-chloro-5chloro-

    ;methylpyridineinanairliftloopreactorfALR)hasbeenstudied.Fivemainreactionconditionsincluding

    T_R,

    ;na/ns,cp,QganddD/dRwereoptimized.Theaveragemolaryieldandpurityof2-chloro-5

    chloromethylpyridine

    ;obtainedwere79%and98.5%respectivelyundertheoptimumoperatingconditions.Finally,theefficien

    cyforthe

    ;preparationof2-chlorc-5

    chloromethylpyridinewithALRandstirredtankreactor(STR)respectivelywascompared.

    ;Keywords2-chloro-5chloromethylpyridine,2-chloro-5

    methylpyridine,directchlorination,airliftloopreactor ;1INTRoDUCTIoN

    ;Fruitfliesareseriousproblemsforagriculturein

    ;dustryandcauseextensivedamagetocrops.Ava- ;rietyofmethodshavepreviouslybeenutilizedin ;effortstocontrolfruitflies.Imidaclopridandae

    ;etamipridhavebeenprovedtobetwoofthesafe

    ;andhighemcientpesticidecompounds[1,.2-Chloro

    ;5-chloromethylpyridineistheimportantintermedi

    ;ateforproducingthem.Thereareseveralmeth

    ;odstoprepare2-chloro5chloromethylpyridine.in

    ;cluding2-chloro5methylpyridinemethod[,.niacin

    ;method[5]and3methylpyridinemethod[6J.Among

    ;them,thesynthesisof2-chloro5methylpyridinewith

    ;chlorinegaswithcatalysttodirectlyprepare2-chloro

    ;5-chloromethylpyridineintheSTRwasoneofthe ;mostsimple,effectiveandeconomicalmethods.None ;isknown,however,abouttheprocessforthedi

    ;rectchlorinationof2-chloro5methylpyridinetoyield

    ;2-chloro..5..chloromethylpyridinewithmultiphaseflow ;reactorssuitableforalargenumberofthegasliquid

    ;twophaseandthegasliquidsolidthreephasehetero

;geneouschemicalreactionsystems.TheALR,char

    ;acterizedbyawelldefinedflowpatternwitheffec

    ;tivedispersingeffect.relativelylowpowerconsump

    ;tionandhighmasstransfercoemcient.isbeingwidely ;usedformultiphasechemicalreactions[一圳.Theaim

    ;ofthepresentstudywasbothtodevelopALRandto ;obtaintheoptimumoperatingconditionsforthedi

    ;rectchlorinationof2-chloro5methylpyridinetoyield

    ;2-chloro.5chloromethylpyridine.

    ;2EXPERIMENTAL

    ;2.1Methodofsynthesis

    ;Itisknownthesidechainof2-chloro5

    ;methylpyridinecanreactusingazobisisobutyronitrile ;ascatalyst,withchlorinegas,tohaveonehydro- ;genatombeingsubstitutedbychlorineatom,and ;theproductof2-chloro-5.-chloromethylpyridineisob?- ;tained.Thesyntheticrouteisoutlinedbelow ;C

    ;2.2Experimentalsetup

    ;Theexperimentalsetupusedtoprepare2-chloro5

    ;chloromethylpyridineisschematicallyshowninFig.i. ;Five0.7mlongglassdrafttubesof0.05,0.06,0.07, ;0.08and0.09minsidediameterwerefixedconcentri

    ;callyinsidethe1.0mlongglassreactortubeof0.1m ;insidediameter,respectively.ThedD/dRratiosob

    ;tained:0.5,0.6,0.7,0.8and0.9respectivelyandthe ;workvolumeoftheALRwas7.85L.Aconcentricjet ;nozzlewithdiameterof0.003mwasdesignedandwas ;locatedatthebottompartofthedrafttube.Chlorine ;andnitrogengassuppliedwithgasstoragetanks ;Figure1Experimentalsetup

    ;1N2cylinder;2Cl2cylinder;3~topvalve;4--flowmeter ;51dryingbottle;6一只asbufferbottle;7ALR;

    ;8--temperaturemeasurementsystem;9-~condensertube; ;1Odryingtube;11--thermostaticbath;

    ;12gasburbottle;13--absorptionbottle

    ;Received200211-15,accepted200305-29.

    ;SupportedbvtheNturalscienceFoundationofTianjin(No.013605711)andtheNationalNaturalScienc

    eFoundationof

    ;China(No.20176040).

    ;Towhomcorrespondenceshouldbeaddressed.Email:jpwen@tju.edu.cn ;,

    ;

    ;,L

;ganm

    ;c

    ;c

    ;

    ;ThePreparationof2-Chloro?-5?-chloromethylpyridineinanAirliftLoopReactor

    ;enteredintothedrafttubetocirculatethesolution ;insidethereactor.Thegasflowratewascontrolled ;bycalibratedrotameter.Theexcesschlorinegasand ;theproducedhydrogenchloridebythereactionwere ;absorbedbysodiumhydroxidesolution.Tempera- ;turecontrollingsystemmaintainedaconstantreaction ;temperature.Condenserconnectedattheoutletofthe ;ALRkeptcondensationandcircumfluenceofthereac

    ;tionmixturestream.Inordertoprotectthereaction ;systemfromabsorbingwater,dryingtubecontaining ;anhydrouscalciumchlorideanddryingbottlecontain

    ;ingconcentratedsulfuricacidwereconnectedtothe ;inletandoutletofthisreactor.respectively. ;2.3SyntheticProcess

    ;Thepreparationof2-chloro5chloromethylpyridine

    ;wasperformedasfollows:intotheALR.2chloro5

    ;methylpyridine.azobisisobutvronitrileand6Lcarbon ;tetrachloridewereaddedandmixedthoroughlyby ;continuouslyfeedingnitrogengas,andthenthere

    ;actionmixturewereheateduptoboilingpointby ;thermostaticbath.Afterstopfeedingnitrogengas, ;thedriedchlorinegaswasintroducedintothesolu

    ;tioninthereactorwithgaschromatographdetecting ;thecontentof2-chloro..5..chloromethylpyridineand ;2-chloro5dichloromethylpyridineasthebyproduct. ;Chlorinegaswasterminatedwhenthecontentofthe ;byproducthadbeenfoundtoreach0.5%1%.Later

    ;thenitrogengaswasintroducedintothereactoragain ;toblowawaytheexcesschlorinegasandhydrogen ;chlorideproducedinthereaction.

    ;Thereactionmixturewasintroducedintoa10L ;distillationstillwithpHadjustedto6with40%(by ;mass1potassiumcarbonatesolutionandthenthe ;aqueousphasewa~removedafterphasesepara

    ;tion.Theorganiclayerobtainedwasdistilledun

    ;derhighvacuum.Carbontetrachloride.2chloro5.

    ;methylpyridine,2-chloro5chloromethylpyridinewere ;separatedgradually.Theunreacted2chloro5

    ;methylpyridinecanbeusedinthenextsyntheticpro

;cess.

    ;Thepurityandstructureof2chloro5

    ;chloromethylpyridineweredetectedbygaschromato

    ;graphandanalyzedbyHNMR,respectively.The

    ;purityofthefinalproductishigherthan98.5%and ;theanalyzedresultofHNMR(CDC13,200MHz,

    ;ppm)is8.37(s,1H),7.247.67(m,2H)and4.54

    ;fs,2H).

    ;3RESULTSANDDISCUSSION

    ;Reactiontemperatureisakeyfactorforchemical ;reactionandtheincreasingoftemperaturewillspeed ;upthereactionrateremarkably.Ascanbeseenfrom ;Fig.2,ahighestmolaryieldofproductwasobtained ;at7580oCwhichisveryclosetotheboilingpointof ;thereactionmixture.Ontheotherhand,theeffectof ;boilingonthemasstransfermavbeanotherfactoron ;theincreasingofthemolaryield.

    ;,?

    ;609

    ;Figure2Effectofreactiontemperatureonthemolar ;yieldof2-chloro-5-chloromethylpyridine ;(na/ns=O.08,cp=0.5g?ml,

    ;Qg=40L?h,dD/dR=0.70)

    ;l556O.C:26o-65.C:

    ;3657O.C:47O75.C:5758O.C

    ;Theinfluenceofn/nonthemolaryieldof2

    ;chloro5chloromethylpyridineisshowninFig.3.It ;isclearthatwhenn/nvariesfrom0.02to0.06,the ;yieldof2-chloro5chloromethylpyridinehasincreased ;withanincreaseinna/ns.Whenna/nsishigherthan ;0.06.theyieldof2-chloro5chloromethylpyridineis ;insensitivetothen/nsratio,andwithwasteofthe ;azobisisobutvronitrileascatalyst.Thereforetheopti

    ;mumna/nscanbeselectedas0.06.

    ;a/nsx100,mol?mol

    ;Figure3Effectofa/8onthemolaryieldof

    ;2-chloro-5chloromethylpyridine

    ;(1R=758o.c,cp=o.5g?ml,

    ;Qg=40L?h,dD/dR=o.70)

    ;Thetypicaleffectoftheconcentrationof2

    ;chloro-5methvlDvridineonthemolaryieldof2. ;chloro.5.chloromethylpyridineisillustratedinFig.4. ;Itisfoundthattheconversionrateof2-chloro-5

    ;methylpyridinedecreasedslightlywiththeincrease

;incandtheoptimumconcentrationof2-chloro-5

    ;methvlDvridinecanbeselectedas0.5g.ml1.

    ;AscanbeseenfromFig.5,themolaryieldof2

    ;chloro-5.chloromethylpyridineincreasedwithanin

    ;creaseinthechlorinegasflowrate.Theoptimum ;chlorinegasflowratecanbeconsideredselectedas ;35L.h_..

    ;Figure6showstheeffectofdD/dRonthemolar ;yieldof2-chloro-5chloromethylpyridine.Themaxi. ;mummolaryieldof2-chloro-5chloromethylpyridine

    ;wasobtainedat0.70ofdD/dR.Itmaybeattributed ;ChineseJ.Ch.E.11(5)608(2003)

    ;

    ;610ChineseJ.Ch.E.(Vo1.11,No.5)

    ;tothelargestoverallgas--liquidvolumetricmasstrans-- ;fercoefficientamongtherangeofthedD/dRstudied. ;Cp,g?ml

    ;Figure4Effectofconcentrationof

    ;2-chloro-5-methylpyridineonthemolaryieldof ;2-chloro-5-chloromethylpyridine

    ;(TR=758o.C,n/n.=o.08,

    ;Qg=40L?h_.,dD/dR=o.70)

    ;Figure5Effectofchlorinegasflowrateonthemolar ;yieldof2-chloro-5-chloromethylpyridine ;(=758O.C,na/n.=O.08,

    ;cp=0.5g-ml_.,dD/dR=o.70)

    ;dD/dR,m?m

    ;Figure6EffectofdD/dRonthemolaryieldof ;2-chloro-5-chloromethylpyridine

    ;(Ta=758O.C,na/n:O.08,

    ;Qg=40L?h,cp=0.5g-ml_1)

    ;Thestabilityofexperimentalresultwascarriedout ;atTR=7580cC,/=0.06,Qg=35L?h_.,

    ;cD=0.5g?ml_.,dD/dR=0.70.Ascanbeseenfrom ;Fig.7,undertheaboveoptimumoperatingcondi

    ;tionstheaveragemolaryieldandpurityof2..chloro..5.. ;chloromethylpyridinearehigherthan79%and98.5% ;respectivelyfortentimesofexperiments. ;AscanbecalculatedfromTable1.themolaryield ;of2-chloro5chloromethylpyridinehasincreasedby ;4.49%.thereactiontimehasdecreasedby21.7%and ;thequantityofchlorinegashasdecreasedby29.9%in ;theALRwithdD/dR=0.70relativelytothatinsTR ;October,2003

;undertheoperatingconditionssuchasTR=75

    ;80~C,na/=0.08,Qg=38.5L.h,cp=0.5g-ml.

    ;Itmaybeduetothehighergasliquidmasstransfer ;andthelongergasresidencetimeintheALR. ;

    ;experimentfortheithtime

    ;Figure7Stabilityofthemolaryieldandpurity ;undertheoptimumoperatingconditions ;(Ta=75——80.C,n/n8=o.06,Qg=35L-h,

    ;Cp=o.5g?ml,dD/dR=o.70)

    ;?Pm;?ym

    ;Table1ComparisonofeconomicalefficiencyofALR

    ;tothatofSTR

    ;NoMENCLATURE

    ;Cp

    ;dD

    ;dR

    ;na

    ;concentrationof2-chloro-5methylpyridine,g?m1

    ;insidediameterofdrafttube,Ill ;insidediameterofreactor,m

    ;molenumber0faz0bisis0butvr0nitrile,mo1 ;molenumberof2-chloro-5methylpyridine,mol ;purityof2-chloro-5-chloromethylpyridine,% ;chlorinegasflowrate,L.h

    ;reactiontemperature,.C

    ;molaryieldof2-chloro-5-chloromethylpyridine,%

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