Lignin is the world's most abundant source of naturally occurring aromatic carbon.  Lignin is a complex polymer comprised of p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol, which is resistant to de-polymerization due to its polydisperse nature of oligomeric cross linking.  While lignin is currently considered a waste product of cellulose processing, lignin has the potential to be a source of useable aromatic carbon through development of selective oxidative, reductive and electrochemical deconstructive processes.  We have been investigating earth-abundant transition metal catalysts as oxidants of model lignin substrates by hydrogen peroxide.  We are also exploring the oxidation of lignin models with Lewis acid-activated TEMPO, and we recently demonstrated that B(C6F5)3 can coordinate and activate the TEMPO moiety.  Through electrochemical approaches, we are developing redox mediators to access bulk lignin; this approach also takes advantage of the follow up reactions to lower the oxidation potential required to de-polymerize lignin. These chemical oxidation schemes have generated multiple oxidation products showing breakdown and coupling reactions. Initial experiments have been focused on lignin model substrates to determine mechanistic details from the catalytic systems and mediators.

Chemical and electrochemical approaches towards oxidative lignin disassembly

248th National Meeting (2014)

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