CO2的轉(zhuǎn)化和利用以及其中催化的作用

Theconversionandutilization

ofCO2andtheroleofcatalysis

易光銓

ChunshanSong.CatalysisToday115(2006)2–32

Introduction

TheatmosphericCO2concentrationhasrisensharplyinthe20thcenturyThereareincreasingconcernsforglobalclimatechangeandthusheightenedinterestworldwideforreducingtheemissionsofCO2

Introduction

FivebroadlydefinedtechnicaloptionsforcontrolofCO2emissions:

energychoices

energyefficiency

CO2capture

CO2sequestration

CO2utilizationChancefor

catalysisUtilizationofCO2CO2:O=C=O

UseCO2forenvironmentallybenignphysicaland/orchemicalprocessingthataddsvaluetotheprocess

UseCO2toproduceindustriallyusefulchemicalsandmaterialsthataddsvaluetotheproducts

UseCO2asabeneficialfluidforprocessingorasamediumforenergyrecovery,contaminantremoval,andemissionreductionSourceofcarbonandcarbonylgroupSupercriticalfluidforextractionDryiceforrefrigerationUreasynthesisReformingofCH4Replacephosgene:dimethylcarbonatesynthesisUtilizationofCO2

ChallengesforCO2utilization:

CostsofCO2capture,separation,purification,andtransportationtousersite.

Marketsizelimitations,littleinvestment-incentivesandlackofindustrialcommitmentsforenhancingCO2-basedchemicals.

Lackofsocio-economicaldrivingforcesforenhancedCO2utilization.Using‘‘MolecularBasket’’adsorbentforCO2separationCO2separationisoftenviewedasthefirststepforchemicalutilization.CombiningtheadvantagesofbothMCM-41andpolyethylenimine(PEI)mayleadtohighly-selectiveandhigh-capacityadsorbentofCO2.Using‘‘MolecularBasket’’adsorbentforCO2separation

WiththeincreaseinPEIloading,thesurfaceareaandporevolumeoftheadsorbentdecreased.

AtPEIloadingof50wt.%,thehighestCO2adsorptioncapacityof246mg/g-PEIwasobtained,whichis30timeshigherthanthatoftheMCM-41andisabout2.3timesthatofthepurePEI.

Impregnationwasfoundtobeabettermethodthanmechanicalmixingmethod.

one-stepimpregnationmethodhadahigherCO2adsorptioncapacitythanthatofpreparedbyatwo-stepimpregnationmethod.

ThehighertheSi/AlratioofMCM-41orthesolvent/MCM-41ratio,thehighertheCO2adsorptioncapacity.

UsingpolyethyleneglycolasadditiveintotheMCM-41-PEIadsorbentincreasednotonlytheCO2adsorptioncapacity,butalsotheratesofCO2adsorption/desorption.

SomerecentstudieshaveshownthatlithiumcontainingoxidessuchaslithiumzirconateandlithiumsilicatecanbeeffectiveCO2absorbents.Using‘‘MolecularBasket’’

adsorbentforCO2separationUsingCO2toreplacephosgene:dimethylcarbonatesynthesis

NewCO2-basedrouteCO2+2CH3OH=CH3OCOOCH3+H2OUsingCO2toreplacephosgene:dimethylcarbonatesynthesisCO2+2CH3OH=CH3OCOOCH3+H2O

SelectiveformationofDMChasbeenobservedoversomesolidoxidecatalystssuchasZrO2

andCeO2–ZrO2solidsolution.Summaryandconclusions

Whenapplicable,usingCO2inconcentratedsourceswithoutCO2separationisdesired.

ForapplicationswherepureCO2isneeded,moreefficientCO2separationmethodisdesired.

CO2canbeusedeffectivelyinchemicalprocessingtoreduceenvironmentalimpact,althoughtheamoun