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Anisole hydrotreatment kinetics on CoMo catalyst in the absence of sulphur: experimental investigation and model construction Daria Otyuskaya, Joris W. Thybaut, Rune Lødeng, and Guy B Marin Energy Fuels, Just Accepted Manuscript • Publication Date (Web): 23 May 2017 Downloaded from http://pubs.acs.org on May 27, 2017
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Energy & Fuels
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Anisole hydrotreatment kinetics on CoMo catalyst
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in the absence of sulphur: experimental
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investigation and model construction
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Daria Otyuskaya1, Joris W. Thybaut1*, Rune Lødeng2, Guy B. Marin1 1
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Laboratory for Chemical Technology, Ghent University, Technologiepark 914, B-9052
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Ghent, Belgium 2
SINTEF Materials & Chemistry, Department of Kinetics and Catalysis, N-7465 Trondheim,
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Norway
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* Corresponding author: Technologiepark 914, 9052 Zwijnaarde, Belgium; +32 9 331 17 52,
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[email protected] 11
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Abstract
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Anisole hydrodeoxygenation over a non-sulphided CoMo/Al2O3 catalyst was investigated as a
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model reaction for fast pyrolysis oil upgrading. Intrinsic kinetics data have been acquired in a
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gas-phase plug-flow reactor at temperatures ranging from 548 to 623 K, a total pressure
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amounting to 0.5 MPa, a space time between 95 and 400 kgcat s molanisole-1 and hydrogen to
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anisole molar ratio from 50 to 400 mol mol-1. A minimum of 16 hours on stream stable
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anisole conversion was observed. The catalyst mainly exhibited anisole demethylation and
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phenol methylation to cresol, rather than hydrogenation or hydrodeoxygenation.
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Demethylation
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Additionally, cresol is formed via phenol methylation. Rival mechanisms were proposed and
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corresponding LHHW elementary steps based kinetic models were derived. Each of the
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proposed models accounted for the interaction of the species with the catalyst surface as well
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as for the surface reactions. For each catalytic cycle a rate-determining step was identified.
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Statistical analysis combined with an assessment of physical meaning of the model
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parameters allowed to propose that for both demethylation and hydrodeoxygenation reactions
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CAr-O bond cleavage is facilitated by a prior hydrogen addition. Cresol is mainly formed from
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phenol methylation rather than from anisole isomerization occurring at a rate which is several
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orders of magnitude slower than that of the other reactions considered.
and
isomerization
reactions
are
followed
by
hydrodeoxygenation.
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Keywords: fast pyrolysis oil upgrading; anisole, hydrodeoxygenation; intrinsic kinetics;
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LHHW kinetic modelling
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List of symbols
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Roman symbols
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A
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anisole [-]
pre exponential factor for reaction j [kg s-1 mol-1 or s-1]
number of carbon atoms in component [-]
AVS
Athena Visual Studio [-]
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B
benzene [-]
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b
model parameter vector [-]
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C
cresol [-]
Ca
Carberry number [-]
43 44 45 46 47 48 49 50 51 52 53 54 55 56 57
component surface concentration [mol kgcat] catalyst pellet diameter [m] reactor internal diameter [m]
. .
degrees of freedom [-]
outlet molar flowrate [mol s-1]
FID
flame ionization detector [-]
GC
gas chromatograph [-]
,
ℎ
activation energy for reaction j [kJ mol-1]
F value of the model significance [-]
Planck constant [J s]
HDO
hydrodeoxygenation [-]
HTK-MI
high-throughput kinetic mechanistic investigation setup [-]
Boltzmann constant [J K-1]
adsorption equilibrium coefficient for component i [MPa-1]
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reaction rate coefficient [kg s-1 mol-1 or s-1]
number of models [-]
number of experiments [-]
P
phenol [-]
reaction order [-]
number of responses [-]
number of parameters [-]
partial pressure of component i [MPa]
R
universal gas constant [J K-1 mol-1]
total pressure [MPa]
R
net rate of formation of component i [mol s-1 kgcat-1]
"
selectivity of anisole towards product [-]
!
""#
%$Page 4 of 38
rate of reaction [mol s-1 kgcat-1]
sum of squares of the residuals between the experimental outlet molar flow
rates and the model calculated ones [-] &
T(
temperature [K] bulk gas temperature [K]
T)
particle surface temperature [K]
Tol
toluene [-]
T*
temperature near the reactor wall [K]
+
catalyst mass [kgcat]
-.
molar anisole conversion [-]
,
weight factor for response i [-]
Greek symbols 4 ACS Paragon Plus Environment
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Energy & Fuels
/
∆12
real parameter value vector [-] standard enthalpy change for component i [kJ mol-1]
3
pressure drop over the catalyst bed [Pa]
3&456
the temperature difference over the film surrounding the catalyst particle [K]
∆"2
3&7
standard entropy change for component i [kJ mol-1 K-1]
internal temperature difference between the external surface and the average in
the particle [K] 3& 8
the radial temperature difference [K]
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stoichiometric coefficient of component in reaction : [-]
=2
chi-square [-]
;
