Extraction of lignin from coffee (Coffea arabica) hull and its subsequent oxidation for production of aldehydes

The fractionation of lignocellulosic materials into their different polymeric constituents, cellulose, hemicellulose, and lignin, is a key objective aimed at recovering the constituents in a pure and usable form. The importance of biomass delignification technologies depends on the amount of lignin that can be removed. This project evaluated the feasibility of employing coffee (Coffea arabica) hull, an agricultural byproduct, to obtain lignin. The delignification was achieved by the transformation of hull using steam explosion as pretreatment followed by an alkaline extraction. Lignin derived from steam-aqueous treatment was oxidized to produce aldehydes such as vanillin and syringaldehyde. The characterization of Coffea arabica indicates an acid-insoluble lignin content of 13.78%. Results show that at a severity of log10Ro = 2.67, the amount of acid-insoluble lignin recovered was 9.27%, while at log10Ro = 4.25, lignin recovery reached a value of 76.85%. It is demonstrated that the combined aldehydes yield (vanillin + syringaldehyde) can reach 8.2% of the lignin available from Coffea arabica by means of steam-explosion process.