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MONDAY, FEB. 8, 2016
12:00 P.M.
WSB-122
SEMINAR CHEMISTRY
KEITH VOELLER (2013 SCSU GRAD)
DEPARTMENT OF CHEMISTRY
U. OF NORTH DAKOTA
"THERMAL CARBON ANALYSIS ENABLING COMPREHENSIVE
CHARACTERIZATION OF LIGNIN AND ITS DEGRADATION PRODUCTS"
Abstract:Atpresent,methodsaddressingligninanditsdecompositionproductscharacterizationarelimited;liquid-liquidextractionfollowedbygaschromatographywithmassspectrometry(GC-MS)targetsonlyvolatilecompoundswhileliquidchromatographymethodsarenotidealforunknownproductsduetolimitedavailabilityofoligomericproductsasidentificationstandards.Previously,pyrolysis(pyr)coupledwithGC-MSwasusedforcharacterizationoflignin.However,thismethodisnotapplicabletodegradationproductsasitdoesnotdifferentiatebetweentheoccurrencesofevaporatingmonomericandthermallydecomposinglargemolecularweightcompounds.Inthisstudy,thermalmethodssuchasthermalgravimetricanalysis,pyrolysis-GC-MS(Pyr-GC-MS),andtotalcarbonanalysis(TCA)areusedforcharacterizationofligninandligninproductsofhydrothermaldegradation.
Thermaldesorption(TD)coupledwithpyr-GC-MSallowedforthedifferentiationofmonomericspeciesevolvingatlowtemperaturesteps(200,300°C)fromlargemolecularweightspeciespyrolyzedat400–850°C.Itisessentialtonotethepyrolyticportionofcarbon(i.e.,coke)cannotbeobservedwithpyr-GC-MSinstruments.Toachieveanalysisincludingmassbalanceclosure,TCAwasusedobtainingaquantitativethermalevolutionprofilethroughTDandpyrolytictemperatureswith/withoutoxygen.DuringanalysisofrawligninwithTCA,upto55%evolvedunderaerobicconditionsaselementalcarbon(i.e.,coke).Bycontrast,productsofligninhydrothermaltreatmentsat200°Cand300°Cshowedonly19%and28%pyrolyzedcarbonrespectively.Ligninhydrothermallytreatedat300°CevolvedsignificantlymorespeciesatlowertemperaturesduringTCAthanthatofhydrothermaltreatedsamplesat200°Cwhichindicatedtheformationofmonomersathighertemperatures.TCAhasthusshownthatrelativelylowtemperature(200–300°C)hydrotreatmentofligninproducednoteworthyamountsofmonomersandsmalloligomerswithoutsignificantre-polymerizationofligninfragments.