Production of ketones from pyroligneous acid of woody biomass pyrolysis over an iron-oxide catalyst

Catalytic upgrading of pyroligneous acid, by-product from slow pyrolysis of woody biomass for char production, was carried out using zirconia-supported iron-oxide catalysts under a steam atmosphere at temperatures ranging from 623 to 723 K, and the effect of ZrO₂ content in the ZrO ₂-FeO_X catalysts on catalytic activity and ketone yields was investigated. It was demonstrated that hydroxyacetone and carboxylic acids (acetic and propionic acids) in the pyroligneous acid were converted into aliphatic ketones (acetone and 2-butanone) via a ketonization reaction over the ZrO₂-FeO_X catalyst. However, reaction inhibition by metal impurities in the pyroligneous acid such as potassium (K) and magnesium (Mg) was also observed. These metal impurities could be removed from the pyroligneous acid without changing the organic composition by using an ion-exchange resin. The removal of the metal impurities was effective in increasing the ketone yields. Moreover, as the W/F value (W: Amount of catalyst, and F: Flow rate of the pyroligneous acid in the feed) increased, the ketone yield increased up to approximately 30 C mol%, and the ketone fraction in the liquid product reached 55 C mol%.