绿色化学与化工导论Chapter 1 introduction

Chapter1IntroductionJAMESH.CLARK1.1Chemistry—Past,PresentandFuture1.2TheCostsofWaste1.3TheGreeningofChemistrySustainabledevelopment,Cleanerproduction,Atomeconomy,Efactor,PrinciplesofGreenChemistry,Life-cycleassessment1.1Chemistry—Past,PresentandFutureChemicalproductsmakeaninvaluablecontributiontothequalityofourlivesandplayafundamentalroleinalmosteveryaspectofmodernsociety.•PharmaceuticalsproductsIntwentiethcentury,Worldpopulation:from1.6to6billion,Lifeexpectancy:almost60%↑•Cropprotectionandgrowthenhancementchemicals•Theenormouspopulationsdemandwesternlevels•Thepublicimageofthechemicalindustryhasbadlydeterioratedinthelasttenyears...•Insomeofthemajorcentresofchemicalsmanufacturingmorepeoplegavepositivethannegativeviews,butformanyEuropeancountriestheratioofunfavourabletofavourableviewswasalarminglyhigh.1.1Chemistry—Past,PresentandFutureFigure1.1Trendsinthefavourabilitytothechemicalindustryofthegeneralpublic(smoothedplots)(basedonMORIOpinionPollfiguresintheperiod1980–2000).IntheUK,asteadydeclineinpublicperceptionofthechemicalsindustriesovermanyyearsisclearlyevident.Itisespeciallydisturbingtoanalysethesurveydatamorecloselyandtonotethatthe16–24yearagegrouphasthelowestopinionofthechemicalsindustries.1.1Chemistry—Past,PresentandFutureFigure1.2TrendinthenumberofapplicationstostudychemistryinUKuniversities(source:UCASUniversitiesandCollegesAdmissionsServices).Atpresent,thepoorimageofchemistryisadverselyaffectingdemand.IntheUK,thenumberofapplicantstoreadchemistryatuniversityhasbeenfallingsteadilyforseveralyearsThenumberofapplicantstoreadchemicalengineeringisevenmorealarming(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.•CompliancewithexistingenvironmentallawswillcostnewEUmemberstateswellover€10billion;asimilaramountisspenteachyearintheUSAtotreatanddisposeofwaste.•Costofwastecaneasilyamountto40%oftheoverallproductioncostsforatypicalspecialitychemicalproduct.ProductioncostsFigure1.3Productioncostsforspecialitychemicals.BreakdownofTypicalSpecialityChemicalManufacturingCostWasteMaterialsLabourCapitalDepreciationEnergy&UtilitiesCostofWasteBreakdownMaterialsTreatment&DisposalCapitalDepreciationLabourTheCostsofWasteFigure1.4Thecostsofwaste.1.3TheGreeningofChemistryFigure1.5Optionsforwastemanagementwithinachemicalmanufacturingprocess.Hierarchyofwastemanagementtechniques•Prevention,byfarthemostdesirableoption•Recycling,thenextmostfavourableoption•Disposal,theleastdesirableoption•Cleanerproduction:‘Thecontinuousapplicationofanintegratedpreventativeenvironmentalstrategytoprocessesandproductstoreduceriskstohumansandtheenvironment.Forproductionprocesses,cleanerproductionincludesconservingrawmaterials,andreducingthequalityandtoxicityofallemissionsandwastesbeforetheyleaveaprocess.’AtomeconomyTable1.1‘Atomaccounts’foratypicalpartialoxidationreactionusingchromateElementFateAtomutilisationCProduct(s)Upto100%HProduct(s)+wasteacid100%CrChromiumwaste0%NaSaltwaste0%SSaltwaste(afteracidneutralisation)0%OProduct(s)+waste100%Atomeconomy:howmanyatomsofthestartingmaterialareconvertedtousefulproductsandhowmanytowaste.Atypicaloxidationreaction:analcohol→acarboxylicacidchromium(VI)asthestoichiometricoxidantEnvironmentalfactorItisusedtoquantifytheeffectsofproductionprocesstotheenvironmentIdea:AllothercompoundsformedotherthanthetargetproductareconsideredtobeWASTE.AtomEconomyandenvironmentaleffectsWheredoesthewastecomefrom?EnvironmentalfactorE=TheamountofwasteTheamountoftargetproductThemorewasteformedThemoreseriousthepollutionIftheatomUtilization=100%E=0EnvironmentalfactorEnvironmentalfactorTable1.2Relativeefficienciesofdifferentchemicalsmanufacturingsectors•Areastraditionallythoughtofasbeingdirty(oilrefining&bulkchemicalproduction)arerelativelyclean-theyneedtobesincemarginsperKgarelow.•Newerindustrieswithhigherprofitmarginsandemployingmorecomplexchemistryproducemuchmorewasterelatively.IndustrysectorProducttonnageBy-productweight/productweightOilRefining106-1080.1BulkChemicals104-1061-5FineChemicals102-1045–50+Pharmaceuticals1