Upgrading of biomass transformation residue: influence of gas flow composition on acetic acid ketonic condensation

Abstract : Acetic acid, a common biomass transformation residue, can be converted into acetone by direct ketonization in the gas phase over gamma-Fe2O3 (maghemite) pre-activated at 450 degrees C under air. This reaction was performed in a continuous flow reactor with varying temperature from 250 to 300 degrees C and different carrier gases. Using N-2 as carrier gas, the activity of the iron based catalyst normally increased with increasing temperature and contact time and remained constant under stationary operating conditions. A slight decrease of activity was observed using a N-2/CO2 mixture as carrier gas. A strong enhancement of the activity was observed when H-2 was introduced in the carrier gas, as a N-2/H-2 or CO2/H-2 mixture. This improvement could be attributed to the modification of the oxidation state of the iron catalyst used for which in situ characterisation is still to be performed.