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An approach to cost reduction in
multi-stage bio-oil hydroprocessing:
applying molybdenum carbide
catalysts
Jae-Soon Choi, Beth Armstrong, Raynella Connatser, Ilgaz Soykal,
Harry Meyer, Viviane Schwartz
Oak Ridge National Laboratory
Alan Zacher, Huamin Wang, Mariefel Olarte, Susanne Jones
Pacific Northwest National Laboratory
Project goal is catalyst development to help reduce
fast pyrolysis bio-oil hydroprocessing costZacher, et al., Green
Chemistry 16 (2014) 491-515.
• Bio-oil hydroprocesing: multi-step processes
1st step: stabilization (mild hydrogenation)
―Low temperature (150-250 °C)
―Ru/C type catalysts
―Can be multi-step
2nd step: deep hydrogenation and hydrocracking
―High temperature (350-400 °C)
―Sulfided Ni(Co)Mo/Al2O3 type catalysts
carbon
Ru Ru Ru Ru
expensive
weak metal-support interaction (leaching)
under reducing conditions
Al2O3
sulfides
hydrothermally unstable
(high water content in bio-oil)
unstable
(low S content in
bio-oil)
coking ubiquitous, but
regeneration proven difficult
Limited long-term
operability is a key
cost driver
We are designing catalysts tailored to bio-oil based on
transition-metal carbides
• Transition metal carbides exhibit precious-metal-like catalytic properties (Mo2C - Ru, WC - Pt…)
• Carbides are active under petroleum hydrotreating conditions
– No need for sulfiding agents (cf. CoMo/Al2O3)
• Carbides can be prepared with high surface area
– No need for supports to disperse active phases (cf. Ru/C, CoMo/Al2O3) => mitigate issues associated with supports
• Performance unproven in real bio-oil upgrading involving hot water & oxygenate-rich environments
– Catalytic reactivity
– Stability (hydrothermal, oxidation, coking) & regenerability
interstitial C
Mo2C, WC
Theory: C insertion to parent
metal lattices makes metal
electronic structures closer to
those of precious metals
2-stage hydrotreater
Techno-economic analysis
• Assess cost reduction potential– Carbides vs. Baseline
– Catalyst cost, regeneration interval,
H2 consumption, oil yield
• Input for project decision making– Research priority
– Go/No-Go decision
Research approach
Catalyst design & synthesis
Shaped bulk
carbides
Reactor evaluation
with real bio-oils
• Activity
• Selectivity
• Stability
• Regenerability
Characterization
• Understand correlations between
synthesis conditions, structures &
performance
• Leverage DOE SC capabilities
Model compound studyMicro-scale analysis
“scale up”
Iterative
process
• Developed doped carbide bead synthesis method
• Synthesis variables
– Dopant type & loading
– MoO3 loading
– Binder type & loading
• Characterization & model compound study guided sample selection for real bio-oil study
– 1st series (BC01-04): assess the impact of dopant type
– 2nd series (BC05-07): assess the impact of dopant loading
– 3rd series (BC09): study regenerability
catalyst code
Bulk Mo carbides selected for detailed evaluation
20 30 40 50 60 70 80 90
Co
un
ts
Position [ 2Theta]
Doped Mo2C
beads
MoO3 powder Doped MoO3
beads
Performance of Mo carbides evaluated with real bio-oil
2-stage reactor (40 ml)• Feed: raw bio-oil obtained from pine
wood via conventional fast pyrolysis
vs.
Baseline
sulfided
Ru/C
+
sulfided
NiMo/Al2O3
Mo2C
Catalyst code Baseline BC01-09
Stage 1 catalyst Sulfided Ru/C Doped Mo2C
Stage 2 catalyst Sulfided NiMo/Al2O3 Doped Mo2C
Stage 1 temperature, °C 190 180
Stage 2 temperature, °C 400 400
Pressure, psia 1800 1750-1820
H2/bio-oil, mL/mL 1935 1676-1715
Stage 1 LHSV, h-1 0.17 0.25
Stage 1 WHSV, h-1 0.44 0.29
Stage 2 LHSV, h-1 0.17 0.25
Stage 2 WHSV, h-1 0.31 0.29
2-stage hydroprocessing reactor parameters
• LHSV: Mo2C > Ru/C ~ Mo sulfide => lower capex
• WHSV: Mo2C ~ Mo sulfide < Ru/C => higher opex– But operating conditions & catalysts not optimized for Mo carbides
– See later that BC09 can perform well at higher WHSV
0.6
0.7
0.8
0.9
1
0 20 40 60
Den
sit
y
Time on stream (h)
BC01
BC02
BC03
BC09
Baseline
Mo carbides can achieve performance similar to Baseline
• Overall comparable hydroprocessing results
– Product yields
– Oil density (degree of deoxygenation: activity)
– Oil composition (fuel product distribution)
• Activity dependent on formulation (e.g., oil density of BC09 vs. BC03)
0
10
20
30
40
50
BC0115h
BC0215h
BC0321h
Baseline49h
Perc
en
tag
e
Oil sample name
Naphtha
Distillate
Fuel oil
Oil density → 0.84 0.83 0.87 0.84
Product yields
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 20 40 60
Yie
ld
Time on stream (h)
aqueous
oil
gas
Oil composition
(SimDist)
Oil density
Bio-oil can be sufficiently upgraded over Mo carbides
• Net improvements in H/C ratio, residual O & H2O content, TAN, and density
TOS (h) C
(wt %, dry)
H
(wt %, dry)
H/C ratio
(dry)
O
(wt %, dry)
H2O
(wt %)
N
(wt %,
wet)
S
(wt %,
wet)
TAN
(mg
KOH/g)
Density
(g/mL)
Feed bio-oil
N/A 53.3 6.8 1.53 39.9 30.0 <0.05 <0.02 77 1.200
BC01
48-54 NM NM NM NM NM NM NM <1 0.869
BC02
48-54 88.2 12.0 1.63 1.54 0 0.10 0 0 0.876
BC03
48-54 87.2 11.1 1.53 3.24 0 0.24 0 0.58 0.893
BC09
48-54 85.8 12.9 1.79 1.29 <0.5 <0.05 <0.02 <0.01 0.824
Baseline (RuS2/C + NiMoS/Al2O3)
43-55 86.3 13.0 1.79 0.65 <0.5 <0.05 <0.02 <0.01 0.835
Stability of Mo carbides sensitive to formulations
0.7
0.8
0.9
1
0 20 40 60
Den
sit
y
Time on stream (h)
BC01
BC02
BC03
BC04
BC05
BC07
BC09
Baseline
BC06 fouled before reaching steady state
(i.e., within 12 h TOS)
Extensive catalyst bed
fouling/plugging
• 2 modes of deactivation: gradual activity loss vs. bed plugging
• Stability highly dependent on dopant type & loading: some formulations
(BC04, 06, 07) suffered bed plugging before completion of a 60-h run
• Elucidating structure-stability relationship needed
0
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100 120 140
Co
nce
ntr
ati
on
(a
t.%
)
Depth (nm)
Mo oxide
BC05 fresh
BC05 tested stage 1
BC05 tested stage 2
XPS Mooxide
0
1
2
3
4
5
6
7
8
9
10
0 20 40 60 80 100 120 140
Co
nce
ntr
ati
on
(a
t.%
)
Depth (nm)
Mo oxide
BC06 fresh
BC06 tested stage 1
BC06 tested stage 2
XPS Mooxide
Mo carbide structure robust in bio-oil hydroprocessing
& deactivation mainly due to “coking”
• No significant oxidation
• Carbon accumulation on the surface was a major change
20 30 40 50 60 70 80
Inte
nsit
y (
a.u
.)
2θ ( )
BC05 fresh
BC05 tested stage 1
BC05 tested stage 2
XRD
20 30 40 50 60 70 80
Inte
nsit
y (
a.u
.)
2θ ( )
BC06 fresh
BC06 tested stage 1
BC06 tested stage 2
XRD
0
10
20
30
40
50
60
70
80
0 20 40 60 80 100 120 140
Co
nce
ntr
ati
on
(a
t.%
)
Depth (nm)
C surface
BC05 fresh
BC05 tested stage 1
BC05 tested stage 2
XPS Ccont.
0
10
20
30
40
50
60
70
80
0 20 40 60 80 100 120 140C
on
ce
ntr
ati
on
(a
t.%
)Depth (nm)
C surface
BC06 fresh
BC06 tested stage 1
BC06 tested stage 2
XPS Ccont.
BC05 run 60 h w/o plugging
BC06 run 12 h w/ stage 2 entrance plugging
Deposited carbon species quite reactive toward H2
• Most of C deposited during hydroprocessing removable
well below 700 °C (carbide synthesis temperature)
– Non-destructive (w/o sintering & carbidic C removal) in situ
regeneration seems feasible
– Lower temperature likely enough under higher H2 pressures
Temperature programmed reduction in H2 at atmospheric pressure
0.0E+00
5.0E-12
1.0E-11
1.5E-11
2.0E-11
2.5E-11
3.0E-11
100 200 300 400 500 600 700 800
m/z
15
sig
na
l (a
.u.)
Temperature ( C)
BC05 fresh
BC05 stage 1
BC05 stage 2
0.0E+00
5.0E-12
1.0E-11
1.5E-11
2.0E-11
2.5E-11
3.0E-11
100 200 300 400 500 600 700 800
m/z
15
sig
na
l (a
.u.)
Temperature ( C)
BC06 fresh
BC06 stage 1
BC06 stage 2
Mo carbides are in situ regenerable
• Reduction in H2 recovers catalytic performance
– Consistent w/ characterization results: coking is the major
deactivation route, but C species are reactive
• Bulk structure of Mo2C robust over 240-h operation + regen.
20 30 40 50 60 70 80
Inte
nsit
y (
a.u
.)
2θ ( )
fresh
60 h, S1
60 h, S2
240 h, S1U
240 h, S1L
240 h, S2
4 consecutive 60-h runs with a doped Mo2C (BC09)
High-level techno-economic analysis performed to
assess cost reduction potential
• PNNL performance & cost models updated with carbide results
• Catalyst cost estimated to be Ru/C ~$70/lb, Mo carbide ~$20/lb
Baseline
Mo carbide
StabilizerRu/C
StabilizerRu/C
Stage 1Ru/C
Stage 1Moly
carbide
Stage 2Moly
carbide
Stage 2Metal sulfide
Pyrolysis Oil
Pyrolysis Oil
HydrocarbonOil
HydrocarbonOil
H2
H2H2H2
H2H2
Data derived from PNNL 40 mL hydrotreater
In situ regenerability can be a key advantage of Mo carbides
• Regenerability can lead to significant cost reduction vs. Baseline
• Improving activity (WHSV) & oil yield can further improve economics
Catalyst type Baseline BC01 BC02 BC05 BC09
Minimum fuel selling price
% change - 0% 1% 11% 18%
% change (with 1 regen) - -18% -17% -13% -9%
Conversion costs
% change - 2% 3% 13% 20%
% change (with 1 regen) - -21% -20% -17% -9%
Catalyst-related op costs
% change - 52% 52% 53% 53%
% change (with 1 regen) - -19% -19% -19% -19%
Installed upgrading capex
% change - -15% -23% -16% -16%
% change (with 1 regen) - -33% -38% -34% -34%
“-” sign indicates cost reduction
Conclusions
• Molybdenum carbides have potential as bio-oil hydroprocessing
catalysts
– Substitutes for both sulfided Ru/C and NiMo/Al2O3 type catalysts
– Major advantages: low cost, durability and in situ regenerability
• Significant cost reduction could be achieved by optimization
– Performance dependent on carbide formulation and structure
– Reactor operating conditions need to be tailored (feedstock, temperature,
pressure, regeneration, coupling with other catalyst systems)
– More fundamental understanding needed
• Future research
– Start optimizing catalyst formulation and structure, operating conditions,
and regeneration procedure to maximize the cost reduction potential
– Performance metrics: WHSV, oil yield, C-retention, long-term operability
Acknowledgments
• Research sponsored by U.S. DOE Bioenergy
Technologies Office
• Access to Center for Nanophase Materials Sciences at
ORNL, a DOE Office of Science User Facility
• Technical assistance and discussion
– Daniel Santosa (PNNL)
– Kevin Cooley, Will Brookshear and Josh Pihl (ORNL)
Thanks for your attention!
Jae-Soon Choi