Electrochemical Study of Lignin Derivatives: Protection and Valorization of Biopolymers
Résumé
The continuous exploration of fossils to meet the global carbon demand has aggravated the already exacerbated
environmental and climatic crisis and increasing political strife elicit the hunt for alternate renewable source of carbon. Lignocellulosic biomass has the potential to serve the purpose of replacing fossil feedstock for the
acquisition of renewable carbon, and is considered as the rich source of carbonaceous materials as it is mainly
composed three components namely: cellulose, hemicellulose and lignin. Unlike cellulose and hemicellulose,
lignin holds an esteemed reputation because of its aromatic nature. Since lignin is composed of three
fundamental monolignols or phenylpropanoid such as p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units
connected via different linkages, the depolymerization of lignin can be regarded as a prime renewable source
to obtain platform chemicals. However, this heterogeneous aromatic biopolymer has been undervalued and is
burnt to produce cheaper heat and electricity.
On industrial scale, lignin is produced as a byproduct during pulp and paper processing via acidic hydrolysis of
lignocellulosic biomass. The harsh conditions during acidic hydrolysis induce conformational changes within
the lignin polymeric chain yielding condensed lignin1 and elevated temperature conditions result in the
undesired degradation of lignin into gaseous products. Thus the lignin obtained is recalcitrant and hard to
depolymerize. Developing protection protocols to avoid the condensation within the lignin so to have nearly
native type lignin2 can greatly help to upgrade the biorefinery process and increase the productivity and
profitability. Moreover, conceiving a greener depolymerization strategy, such as electrochemical methods, to
produce value added monomers can uplift the current valorization technologies at industrial scale, therefore
leading to the viable and economical production of commodity chemicals.