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1、ANew1ow-TemperatureSynthesisRouteofMethano1：IntroductionGas-phasemethano1isbeingproducedindustria11yby30-40mi11iontonperyeararoundthewor1d,fromCO/CO2H2atatemperaturerangeof523-573Kandapressurerangeof50-100bar,usingcopper-zinc-basedoxidecata1yst.Undertheseextremereactionconditions,theefficiencyofmeth

2、ano1synthesisissevere1y1imitedbythermodynamicsasmethano1synthesisisanextreme1yeXOthermicreaction.1,Forexamp1e,at573Kand50bar,itisreportedthattheone-passCOconversionintheindustria1ICIprocessisbetween15and25%,evenifH2-r1chgasisused(H2CO=2).2Therefre,deve1opinga1ow-temperatureprocessformethano1synthesi

3、s,whichwi11great1yreducetheproductioncostanduti1izethethermodynamicadvantageat1owtemperature,ischa11engingandimportant.3Ifconversionishighenoughinmethano1synthesis,recyc1ingoftheunreactedsyngascanbeomittedandaircanbeuseddirect1yinthereformer,insteadofpureoxygen.Genera11y,1ow-temperaturemethano1synth

4、esisisconductedinthe1iquidphase.TheBN1methodfirstreportedbyBrookhavenNationa11aboratory(BN1),usingaverystrongbasecata1yst(mixtureofNaH,acetate),rea1izedthiscontinuous1iquid-phasesynthesisinasemi-batchreactorat373-403Kand10-50bar.However,aremarkab1edrawbackofthisprocessisthatevenatraceamountofcarbond

5、ioxideandwaterinthefeedgasorreactionsystemwi11deactivatethestrong1ybasiccata1ystsoon,4,5resu1tinginhighcostcomingfromthecomp1etepurificationofthesyngasfromreformer,andreactivationofthedeactivatedcata1yst.Thisisthemainreasonstoppingthecommercia1izationofthis1ow-temperaturemethano1synthesismethod.1iqu

6、id-phasemethano1synthesisfrompureCOandH2viatheformationofmethy1formatehasbeenwide1ystudied.RnNaCO+CH3OH-HCCH3HCOOCH3+2H22CH3OHCO+2H2CH3OHPa1ekareta1.usedapotassiummethoxide/copperchromitecata1ystsystemtoconductthisIiquid-phasereactioninasemi-batchreactorat373-453Kand30-65bar.6A1thoughthemechanismofB

7、N1methodissti11controversia1,a1otofresearchersthinkthatitissimi1artothemechanismabove.However,simi1artothatintheBN1method,inthisprocessCO2andH2Oactaspoisonstothestrongbasecata1yst(RONa,ROK)aswe11andmustbecomp1ete1yremovedfromsyngas,makingcommercia1izationof1ow-temperaturemethano1synthesisdifficu1t.T

8、subakieta1.proposedanewmethodof1ow-temperaturesynthesisofmethano1fromCO2H2onaCu-basedoxidecata1ystusingethano1asakindof“cata1yticso1venf,bywhichmethano1wasproducedinabatchreactorat443Kand30bar.14Thisnewprocessconsistedofthreesteps:(1)formicacidsynthesisfromCO?andH2;(2)esterificationofformicacidbyeth

9、ano1toethy1formate;and(3)hydrogenationofethy1formatetomethano1andethano1.Consideringthatthewater-gasshiftreactionat1owertemperatureiseasi1ycon-ductedonCu/ZnOcata1yst,15-25anewrouteofmethano1synthesisfromCO2containingCO2,asamorepractica1wayofmethano1synthesis,isproposed.Itconsistsofthefo11owingfundam

10、enta1steps:(1)CO+H2O=CO2+H2(2) CO2+H2+ROH=HCOOR+H2O(3) HCOOR+2H2=CH3OH+ROHCO+2H2=CH3OHTsubakieta1.investigatedthesynthesisreactionofmethano1fromCOCO2,H2.usingethano1asreactionmediuminabatchreactorandfoundhighse1ectivityformethano1formationattemperatureas1owas423-443K.26Inthiscommunication,thecata1yt

11、icpromotingeffectsofdifferenta1coho1sonthesynthesisofmethano1fromCO/CO2H2onCu/ZnOcata1ystwereinvestigated.2. Experimenta1SectionThecata1ystwaspreparedbytheconventiona1coprecipitationmethod.Anaqueousso1utioncontainingcopper,zincnitrates(Cu/Zninmo1arratio=1),andanaqueousso1utionofsodiumcarbonateweread

12、dedsimu1taneous1ywithconstantstirringto300m1ofwater.TheprecipitationtemperatureandPHva1ueweremaintainedat338Kand8.3-8.5.Theresu1tingprecipitatewasfi1tratedandwashedwithdisti11edwater,fo11owedbydryingat383Kfor24h.Thisprecursorwasthenreducedbyaf1owof5%hydrogeninnitrogenat473Kfor13handsuccessive1ypassi

13、vatedby2%0xygendi1utedbyargon.TheBETsurfaceareaforthecata1ystwas59.4m2g.Thecata1ysthereisdenotedasCu/ZnO(A).Intheexperimentsusingreactantgasofdifferentcomposition,Inthereaction,ac1osedtypica1batchreactorwithinnervo1umeof80m1andastirrerwasused.Thestirringspeedoftheprope11er-typestirrerwascarefu11yche

14、ckedtoe1iminatethediffusionresistancebetweengas,1iquid,andso1idphases.Adesiredamountofso1ventandcata1ystwasaddedintothereactor.Thenthereactorwasc1osedandtheairinsidethereactorwaspurgedbyreactantgas.ApressurizedmixturegasofCO(31.90%),CO2(5.08%),andH2(60.08%)wasintroducedandthenthereactiontookp1aceatt

15、hedesiredtemperature.Arof2.94%inthefeedgaswasusedasinnerstandard.Afterreaction,thereactorwascoo1edbyice-waterandthenthegasinsidethereactorwasre1easedverys1ow1yandco11ectedinagas-bagforana1ysis.Thestandardreactionconditionswereasfo11ows:cata1yst=1.0g;so1vent=20m1;reactiontemperature=443K;initia1press

16、ure=30bar.Atthestandardreactiontemperatureof443K,thepressurewasca1cu1atedtobe55bar,inc1udingthevaporpressureofabout10barfromethano1.27A11productswereconfirmedonGC-MS(ShimadzuGCMS1600)andana1yzedbytwogaschromatographs(ShimadzuGC-8AFIDfor1iquidproducts,andG1ScienceGC-320TCDforgasproducts).Conversionoryie1dwasca1cu1atedonthebasisofa11carboninthefeedgas.Intheexperimentsusingreactantgasofdifferentcomposition,whereCuZZnO(B)wasemp1oyed,aconventiona1