Abstract

Nitrogen-containing graphene material (LCN) has been identified
as an effective catalyst for the oxidation of b-O-4 and a-O-
4 types of lignin model compounds in the presence of tertbutyl
hydroperoxide, to provide aromatic aldehydes, acids and
other organic chemicals in high yield. The transformations of
five lignin model compounds over LCN were investigated systematically.
Instrumentation analysis, kinetic study and radical
trapping experiments highlight the mechanistic features of the
reaction, including: 1) the reaction pathway starts by benzylic
CH or COH bond activation, followed by CaCb or CaO
bond cleavage, and finally further oxidation of intermediate aromatics;
and 2) the reaction follows a free-radical mechanism
with all the key steps involving radical species. In addition, the
LCN proved to be a highly stable catalyst; no significant activity
decrease was observed for four consecutive runs, and X-ray
photoelectron spectroscopy analysis indicates negligible decrease
in the content of the active nitrogen species in the catalyst.
Notably, this new catalytic system can be extended to the
oxidative depolymerisation of real lignin, to produce a significant
portion of liquefied, low-molecular-mass products.