Effect of metal oxide redox state in red mud catalysts on ketonization of fast pyrolysis oil derived oxygenates

Iron oxide catalysts derived from red mud were reduced at different temperatures and alkali metals extracted to determine the effect of iron redox state and mixed alkali doping on ketonization of key oxygenates (acetic acid, acetol, formic acid, and levoglucosan) found in fast pyrolysis oil aqueous phase. Hydrogen reduction at 300 degrees C, compared to 400 and 500 degrees C, generated the highest level of magnetite and weak and strong acid sites (NH3-TPD), while maintaining base sites (CO2-TPD) in the catalytic material, resulting in the highest acetone and 2-butanone yields from the oxygenate mixture with limited coking. Acid treatment of red mud and subsequent reduction generated higher surface area, yet significantly lower ketonization activity and higher coking activity. This was attributed to the lack of alkali metals, and subsequent base sites generated upon calcination and H-2 reduction, when in the presence of levoglucosan. Similarly, poor results were obtained with iron oxides supported on SiO2/Al2O3 without alkali metals when upgrading the oxygenate mixture. The results indicate the need for a multifunctional catalyst (acid and base sites with oxygen vacancies) when upgrading complex oxygenate mixtures in fast pyrolysis oil.