(206g) Pyrolysis Vapors Upgrading Using Metal Oxides

Pyrolysis Vapors
Upgrading using Metal Oxides

Ayman M. Karim¹,
Donghai Mei¹, Vanessa Lebarbier¹, Changjun Liu^1,2 and Yong Wang^1,2

¹Pacific
Northwest National Laboratory

²Washington
State University

The vapors generated during fast pyrolysis of biomass
contain a significant fraction of light oxygenates (acetic acid, hydroxyacetaldehyde, hydroxyacetone,..) which are produced through undesired fragmentation
reactions during pyrolysis. Hydrodeoxygenation of the light oxygenates would
result in light alkanes which are not useful for
transportation fuels. Therefore. the
light compounds need to be converted to larger molecules before the   hydrodeoxygenation/hydrotreating of
the pyrolysis vapors (or bio-oil).

In this contribution, deoxygenation strategies for the
upgrading of light oxygenates using metal oxides will be presented. The work
combines experimental and density functional theory (DFT) calculations to
identify metal oxide(s) for the

1-     
Upgrading of light oxygenates (building up) to
fuel range compounds (C5+)

2-     
Deoxygenation of
biomass depolymerization products (C5+ molecules)

We will show that ketonization and condensation on CeO₂
based mixed oxides is an effective way of re-building the light oxygenates into
fuel range molecules. CeO₂ based mixed oxides show a 90+%
selectivity to acetone during the ketonization of acetic acid. The ketonization
reaction pathway on CeO₂ was investigated using density functional
theory calculations and the role of the second metal on selectivity and
tolerance to H₂O and CO₂ will be presented.

The deoxygenation of the pyrolysis vapors using partially
reduced metal oxides will also be presented. We show that oxygen vacancies on MoO₃
(010) can selectively cleave the C-O bond over C-C bonds. Finally we will discuss
the strategies and challenges to combine both approaches in a single upgrading
step.