绿色化学与化工导论Chapterintroduction

Chapter1IntroductionJAMESH.CLARK,1.1ChemistryPast,PresentandFuture1.2TheCostsofWaste1.3TheGreeningofChemistrySustainabledevelopment,Cleanerproduction,Atomeconomy,Efactor,PrinciplesofGreenChemistry,Life-cycleassessment,1.1ChemistryPast,PresentandFuture,Chemicalproductsmakeaninvaluablecontributiontothequalityofourlivesandplayafundamentalroleinalmosteveryaspectofmodernsociety.PharmaceuticalsproductsIntwentiethcentury,Worldpopulation:from1.6to6billion,Lifeexpectancy:almost60%CropprotectionandgrowthenhancementchemicalsTheenormouspopulationsdemandwesternlevelsThepublicimageofthechemicalindustryhasbadlydeterioratedinthelasttenyears.Insomeofthemajorcentresofchemicalsmanufacturingmorepeoplegavepositivethannegativeviews,butformanyEuropeancountriestheratioofunfavourabletofavourableviewswasalarminglyhigh.,1.1ChemistryPast,PresentandFuture,Figure1.1Trendsinthefavourabilitytothechemicalindustryofthegeneralpublic(smoothedplots)(basedonMORIOpinionPollfiguresintheperiod19802000).,IntheUK,asteadydeclineinpublicperceptionofthechemicalsindustriesovermanyyearsisclearlyevident.Itisespeciallydisturbingtoanalysethesurveydatamorecloselyandtonotethatthe1624yearagegrouphasthelowestopinionofthechemicalsindustries.,1.1ChemistryPast,PresentandFuture,Figure1.2TrendinthenumberofapplicationstostudychemistryinUKuniversities(source:UCASUniversitiesandCollegesAdmissionsServices).,Atpresent,thepoorimageofchemistryisadverselyaffectingdemand.IntheUK,thenumberofapplicantstoreadchemistryatuniversityhasbeenfallingsteadilyforseveralyears,Thenumberofapplicantstoreadchemicalengineeringisevenmorealarming(1000intheyear2000intheUK),Viewoftwentiethcenturychemicalmanufacturing,(1)Startwithapetroleum-basedfeedstock.(2)Dissolveitinasolvent.(3)Addareagent.(4)Reacttoformanintermediatechemical.(5)Repeat(2)(4)severaltimesuntilthefinalproductisobtained;discardallwasteandspentreagent;recyclesolventwhereeconomicallyviable.(6)Transporttheproductworldwide,oftenforlong-termstorage.(7)Releasetheproductintotheecosystemwithoutproperevaluationofitslong-termeffects.,Therecipeforthetwenty-firstcentury,(1)Designthemoleculetohaveminimalimpactontheenvironment(shortresidencetime,biodegradable).(2)Manufacturefromarenewablefeedstock(e.g.carbohydrate).(3)Usealong-lifecatalyst.(4)Usenosolventoratotallyrecyclablebenignsolvent.(5)Usethesmallestpossiblenumberofstepsinthesynthesis.(6)Manufacturetheproductasrequiredandascloseaspossibletowhereitisrequired.Wemusttrainthenewgenerationofchemiststothinkoftheenvironmental,socialandeconomicfactorsinchemicalsmanufacturing.,1.2TheCostsofWaste,Inthemid-1990sintheUSA,forexample,onlyabout300orsoofthe75000commercialsubstancesinusewereclassifiedashazardous.CompliancewithexistingenvironmentallawswillcostnewEUmemberstateswellover10billion;asimilaramountisspenteachyearintheUSAtotreatanddisposeofwaste.Costofwastecaneasilyamountto40%oftheoverallproductioncostsforatypicalspecialitychemicalproduct.,Productioncosts,Figure1.3Productioncostsforspecialitychemicals.,TheCostsofWaste,Figure1.4Thecostsofwaste.,1.3TheGreeningofChemistry,Figure1.5Optionsforwastemanagementwithinachemicalmanufacturingprocess.,Hierarchyofwastemanagementtechniques,Prevention,byfarthemostdesirableoptionRecycling,thenextmostfavourableoptionDisposal,theleastdesirableoptionCleanerproduction:Thecontinuousapplicationofanintegratedpreventativeenvironmentalstrategytoprocessesandproductstoreduceriskstohumansandtheenvironment.Forproductionprocesses,cleanerproductionincludesconservingrawmaterials,andreducingthequalityandtoxicityofallemissionsandwastesbeforetheyleaveaprocess.,Atomeconomy,Table1.1Atomaccountsforatypicalpartialoxidationreactionusingchromate,Atomeconomy:howmanyatomsofthestartingmaterialareconvertedtousefulproductsandhowmanytowaste.Atypicaloxidationreaction:analcoholacarboxylicacidchromium(VI)asthestoichiometricoxidant,EnvironmentalfactorItisusedtoquantifytheeffectsofproductionprocesstotheenvironmentIdea:AllothercompoundsformedotherthanthetargetproductareconsideredtobeWASTE.,AtomEconomyandenvironmentaleffects,Wheredoesthewastecomefrom?,Environmentalfactor,ThemorewasteformedThemoreseriousthepollution,IftheatomUtilization=100%E=0,Environmentalfactor,Environmentalfactor,Table1.2Relativeefficienciesofdifferentchemicalsmanufacturingsectors,Areastraditionallythoughtofasbeingdirty(oilrefiningb11021J.,Weseektosatisfyourneedandnotourgreed,life-cycleassessment,Thelife-cycleofaproductcanbeconsideredas:Pre-manufacturing(materialsacquisition)Manufacturing(processingandformulation)Productdelivery(packaginganddistribution)ProductuseEndof(first)life,Wecannolongeraffordsingle-useproducts.,life-cycleassessment,Figure1.7Life-cycleassessmentforchemicalproducts(E=energyinput;C=consumablesinput;W=waste).,Pollutionpreventionoptions,Figure1.8Pollutionpreventionoptionsinthelife-cycleofachemicalproduct.,Pollutionpreventionoptions,Pollutionpreventionoptionscanbeconsideredateverystageinthelife-cycleofachemicalproduct.Adoptalife-cycleperspectiveregardingchemicalproductsandprocessesRealisethattheactivitiesofyoursuppliersandcust