ie9b03242_si_001.pdf (239.09 kB)
110th Anniversary: Microkinetic Modeling of the Vapor Phase Upgrading of Biomass-Derived Oxygenates
journal contribution
posted on 2019-08-12, 19:46 authored by Lauren
D. Dellon, Chun-Yi Sung, David J. Robichaud, Linda J. BroadbeltBio-oil produced from fast pyrolysis
of biomass is a complex mixture
of more than 200 compounds, including oxygenates and acids. As these
species are highly undesirable in fuels, catalytic upgrading of biomass
pyrolysis product vapors, also known as catalytic fast pyrolysis,
is performed to upgrade the vapors to valuable fuels and chemicals.
This work presents a detailed microkinetic model, composed of elementary
steps, of the catalytic upgrading of acetic acid and acetone, two
common oxygenates present in bio-oil. An automated network generator
was utilized to construct
a reaction network composed of 580 unique species and 2160 unique
reactions. The kinetic parameters for each reaction in the network
were estimated using transition state theory, the Evans–Polanyi
relationship, and thermodynamic data. The resulting mechanistic model
is able to describe experimental data presented in the literature
for the transformation of acetic acid and acetone on HZSM-5 in a fixed-bed
reactor, which is modeled as a plug-flow reactor. Additionally, the
model solutions reveal vital information regarding the mechanism by
which acetic acid and acetone are upgraded to valuable fuels and chemicals.
In the first phase of the mechanism, acetic acid is converted to acetone
via acylium ion addition to acetic acid; this is followed by decarboxylation
of acetoacetic acid. The second phase is dominated by the self-aldol
condensation of acetone, which is shown to occur predominantly through
the keto form of acetone rather than the enol form, and subsequent
deoxygenation reactions leading to olefins and aromatics. Finally,
net rate analysis shows that aromatics are primarily formed via a
pathway including aldol condensation of mesityl oxide, whereas olefins
are produced from the addition of isobutene and subsequent cracking.