Fuel additives from the controlled depolymerization of lignin

Lignin is an abundant biopolymer found in trees and woody plants; its complex 3-​dimensional structure consists of recurring phenolic units. As the largest available source of renewable arom. functionality, there has been much interest in the breakdown of lignin to form higher value species; phenolics from lignin are potentially useful in a range of applications including as antioxidants in fuels. The robust nature of lignin is responsible for the support network in plants, however it also leads to a resistance to chem. degrdn. Homogeneous catalysis has the potential to effect high activity and selectivity in lignin depolymn., notable examples include nickel and vanadium-​based systems.1-​3 To date, the majority of this research has invoked the use of lignin model compds. in order to facilitate mechanistic understanding and simplify anal. Following precedent in the literature for the cleavage of C-​O linkages in lignin model compds. by vanadium Schiff-​base complexes, a range of vanadium complexes with salen type ONNO ligands were synthesized, characterized and investigated for their catalytic activity in the degrdn. of a model lignin compd. Kinetic studies and Arrhenius anal. conducted in order to gain mechanistic insights and inform catalyst design will be discussed. Catalysts developed in the studies were then tested on samples of lignin extd. from wheat straw.