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

choijs@ornl.gov