Possible use as biofuels of monoaromatic oxygenates produced by lignin catalytic conversion: A review

Small aromatic molecules with oxygen-containing functional groups (monoaromatic oxygenates) are common products of the catalytic depolymerization of lignin, which can be considered as a promising class of fuel additives. This mini-review article starts with an introduction of second generation (2G) of biofuel production from lignocellulose and the further conversion of lignin into fuel performance boosting blends. The discussion is divided into four parts. The first part gives a brief overview of the production of aromatic oxygenates from the catalytic conversion of lignin of different origin. The three following parts are focused on the aromatic oxygenates, for which combustion data can be found. The second part describes their chemical structure and physical properties. The third part is dominated by their global combustion performance, i.e., the commercial fuel parameters as lower heating value, octane and cetane numbers. A few studies on ignition delay times and laminar flame velocities are also described. The fourth part shortly reviews the kinetic studies presenting product quantifications, the proposed detailed kinetic models and the influence of the structure of the aromatic reactant on soot formation. To finish, a perspective on future research directions is given.