Stabilization of Fast Pyrolysis Oil Derived from Wood through Esterification

Abstract

Abstract In the present work, crude bio-oil obtained from vacuum pyrolysis of babul wood was stabilized by esterification with 1-butanol using the cation exchange resin, Amberlyst-15, as a solid acid catalyst. Ester formation reduces the pH, thereby increasing the shelf-life of the bio-oil. Since esterification is a reversible reaction, simultaneous separation of water during the course of the reaction helps to obtain high conversion. Azeotropic removal of water by reactive distillation was found to be effective in this work. Apart from reducing pH and improving shelf-life, this process also enabled water removal from crude bio-oil, and viscosity was reduced when the bio-oil was blended with alcohol. Amberlyst-15 was found to get deactivated after repeated use. Characterization of fresh and used catalyst by Brunauer–Emmett–Teller (BET) surface area measurement and thermal analysis showed that the deposition of carbonaceous material on the catalyst is responsible for its deactivation. The condensation and oligomerization reactions of unstable compounds (e.g. furfural and its derivatives) are suspected to be the main reasons underlying catalyst deactivation.