綠色化學(xué)與化工導(dǎo)論Chapter-1-introduction課件

14三月2024綠色化學(xué)與化工導(dǎo)論Chapter1introduction1.1Chemistry—Past,PresentandFutureChemicalproductsmakeaninvaluablecontributiontothequalityofourlivesandplayafundamentalroleinalmosteveryaspectofmodernsociety.PharmaceuticalsproductsIntwentiethcentury,Worldpopulation:from1.6to6billion,Lifeexpectancy:almost60%↑Cropprotectionandgrowthenhancementchemicals

TheenormouspopulationsdemandwesternlevelsThepublicimageofthechemicalindustryhasbadlydeterioratedinthelasttenyears...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.1.2TheCostsofWasteInthemid-1990sintheUSA,forexample,onlyabout300orsoofthe75000commercialsubstancesinusewereclassifiedashazardous.CompliancewithexistingenvironmentallawswillcostnewEUmemberstateswellover€10billion;asimilaramountisspenteachyearintheUSAtotreatanddisposeofwaste.Costofwastecaneasilyamountto40%oftheoverallproductioncostsforatypicalspecialitychemicalproduct.ProductioncostsFigure1.3Productioncostsforspecialitychemicals.TheCostsofWasteFigure1.4Thecostsofwaste.1.3TheGreeningofChemistryFigure1.5Optionsforwastemanagementwithinachemicalmanufacturingprocess.HierarchyofwastemanagementtechniquesPrevention,byfarthemostdesirableoptionRecycling,thenextmostfavourableoptionDisposal,theleastdesirableoptionCleanerproduction:‘Thecontinuousapplicationofanintegratedpreventativeenvironmentalstrategytoprocessesandproductstoreduceriskstohumansandtheenvironment.Forproductionprocesses,cleanerproductionincludesconservingrawmaterials,andreducingthequalityandtoxicityofallemissionsandwastesbeforetheyleaveaprocess.’AtomeconomyTable1.1‘Atomaccounts’foratypicalpartialoxidationreactionusingchromateElementFateAtomutilisationCProduct(s)Upto100%HProduct(s)+wasteacid<100%CrChromiumwaste0%NaSaltwaste0%SSaltwaste(afteracidneutralisation)0%OProduct(s)+waste<<100%Atomeconomy:

howmanyatomsofthestartingmaterialareconvertedtousefulproductsandhowmanytowaste.Atypicaloxidationreaction:analcohol→acarboxylicacidchromium(VI)asthestoichiometricoxidantEnvironmentalfactorItisusedtoquantifytheeffectsofproductionprocesstotheenvironmentIdea:AllothercompoundsformedotherthanthetargetproductareconsideredtobeWASTE.AtomEconomyandenvironmentaleffectsWheredoesthewastecomefrom?EnvironmentalfactorE=TheamountofwasteTheamountoftargetproductThemorewasteformedThemoreseriousthepollutionIftheatomUtilization=100%E=0EnvironmentalfactorEnvironmentalfactorTable1.2RelativeefficienciesofdifferentchemicalsmanufacturingsectorsAreastraditionallythoughtofasbeingdirty(oilrefining&bulkchemicalproduction)arerelativelyclean-theyneedtobesincemarginsperKgarelow.Newerindustrieswithhigherprofitmarginsandemployingmorecomplexchemistryproducemuchmorewasterelatively.IndustrysectorProducttonnageBy-productweight/productweightOilRefining106-108<0.1BulkChemicals104-1061-5FineChemicals102-1045–50+Pharmaceuticals10-10325-100+Environmentalquotient(EQ)

E-----EnvironmentalfactorQ-----Theextentofhazardousnessofthewastetotheenvironmentobtainedfromtheperformanceofthewasteintheenvironment.EQ＝E×QTheE

factorjustgivestheratioofthewasteandthetargetproduct.Buttheenvironmentalpollutionisstronglyassociatedwiththeharmfulperformanceofthewaste.EnergyEfficiencyTable1.3Global‘lostwork’inmajorchemicalprocessesProcessTheoreticalworkpotential(kJ·mol-1finalproduct)RawmaterialsFinalproductaThermodynamicefficiency(%)Naturalgas+air→methanol113671763Naturalgas+air→hydrogen40923658Ammonia(fromnaturalgas+air)→nitricacid995434Copperore→copper15371309Bauxite→aluminium470388819aExcludesany‘steamcredit’.Energyefficiencyvia‘lostwork’BiomassutilisationFigure1.6Biomassutilisationin2040.BiomassutilisationTable1.4FromfossiltogreenEnergysourcePercentageofenergysources199