Heterogeneous Catalysis Research at Argonne National Laboratory

Chemical Reaction Engineering Laboratory Washington University, St. Louis, MO

October 24, 2006

Christopher L. Marshall

Group Leader, Heterogeneous Catalysis

Chemical Engineering Division

CLMarshall@anl.gov

2

“A catalyst is a substance that promotes a chemical reaction with no net participation

in it.” Berzelius, 1836

The impact of catalysis on the nation's economy – Generate U.S. sales in excess of $400

billion per year.– Net positive balance of trade of $16

billion annually. The fuel and chemical industry is a

primary producer and consumer of energy. – > 90% of all chemical processes are

catalytic. – Catalysis is essential

• energy production• energy conservation• environmental maintenance and

clean up

E

Reaction Coord.

A + B AB* C

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Catalysis – Science Combining Three Disciplines

Chemistry

Material Science

Chemical Engineering

Key Knowledge at the Interfaces

Collaboration is not only key—it is ESSENTIAL

Collaboration is not only key—it is ESSENTIAL

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Goals of the Heterogeneous Catalysis Group

Develop fundamental understanding of the mechanisms of catalyst activity and deactivation.

Use new synthesis techniques to improve catalyst supports and active phases.

Develop new spectroscopic techniques for understanding catalysts under working conditions.– In situ characterization

• Synchrotron x-rays Interface with industrial and academic institutions to

bring new techniques and technology into the market.

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Current Catalysis Projects

Novel Nanoporous Membrane Catalyst for Selective Oxidation

Hydrocarbon Based NOx Reduction Catalysis Ethanol Synthesis via Synthesis Gas Feed

– 2 projects New Nanoscale Fischer Tropsch Catalysts Dense Membrane Catalysts for the Synthesis of

Green Olefins Microporous Membranes for the Purification of

Hydrogen

Novel Nanoporous Membrane Catalyst for Selective Oxidation

Hydrocarbon Based NOx Reduction Catalysis Ethanol Synthesis via Synthesis Gas Feed

– 2 projects New Nanoscale Fischer Tropsch Catalysts Dense Membrane Catalysts for the Synthesis of

Green Olefins Microporous Membranes for the Purification of

Hydrogen

Novel Nanoporous Membrane Catalyst for Selective OxidationChristopher L. Marshall

Stephanie Mucherie, Jeffrey W. ElamPeter C. Stair, Michael J. PellinLennox E. Iton, Larry A. CurtissHao Feng, Hsien-Hau Wang, Guang Xiong

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Concept: Nanostructured Membrane Catalysis(nano monoliths)

Contact Control– Identical Diffusion Paths– Short Contact Time

Reagent Size Control– Pore-size Selection

Site Isolation– One site in each channel– Barrier layers at ends

Sequenced Sites– Different sites at

entrance/exit

Reactants Products

Hydrophobic Hydrophilic

Reactants Products

Reactants ProductsIntermediate

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Pore Growth Mechanism

E field assist dissolution of the barrier layer (effective only on the bottom of the pores)

Generation of new alumina barrier layer (on the Al/alumina interface)

Field Assist Dissolution of the barrier layers

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The Porous Alumina Film

G. Patermarakis, J of Catalysis 147 141 (1994) AAO made in 0.3M oxalic acid

Al2O3

Pores

po

rou

s la

yer

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Whatman Anopore Membranes

http://www.whatman.com

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AlCH3

CH3

CH3OH OH OH

AlCH3

CH3

CH3

A)

B)

OHAl(CH3)3OH OH

Trimethyl Aluminum(TMA)

CH4

AlCH3

AlCH3CH3

H2O

Water

AlCH3

CH3

CH3OH OH OH

AlCH3

AlCH3CH3 Al

CH3

CH3

CH3

CH3

OH OH OHAl Al

CH3CH3

H2O

H2OOH

CH4

OHOH

Atomic Layer Deposition (ALD)

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Materials

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Synthesis Strategy

ALDAl2O3

AAO40 nm pores

ALDTiO2

ALDV2O5

shrink poresto 10 nm

depositcatalytic support

depositcatalyst

ALD Viscous Flow Reactor

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Pore Diameter Control: ALD

ALD Enables Extremely Conformal Coating

500 nm

L=50 m

d=65 nm

Cross-SectionalSEM:

L/d ~ 103

Coat Nanoporous Membrane with Al2O3 Using ALD Techniques

NanomaterialsResearch Corp.

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ALD Results

A) B)

C)

D)

E)

ZnO on AAO

15 nm ALD ZnO2

40 nm AAO pores

Al2O3 on AAO

15 nm ALD film

40 nm AAO pores

AAO

40 nm AAO pores

Al2O3 on AAO

15 nm ALD film

40 nm AAO pores

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Al ring around AAO as a supporter

• Stable > 550°C

• ΔP > 10 psi

• Flow 10 sccm

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C3H8

C3H6

COx

ODH rates on supported vanadium depend on • support composition • VOx surface density.

Increasing VOx surface density for all supports, • Activity , Selectivity to propylene • Activity:

• Polyvanadate > monovanadate

Khodakov, A., B. Olthof, Bell, A. T., Iglesia, E. (1999). J. Catal. 181: 205.

Formation of propylene but also undesired carbon oxides (CO and CO2) products

Oxidative Dehydrogenation (ODH) of propane

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Objective

Study of the catalytic performance of VOx supported on AAO membrane – oxidative dehydrogenation of propane

Comparison with a conventional VOx/Al2O3 powder catalyst

Effect on the reactivity of the AAO membrane catalyst of– method of deposition– V loading– nature of the support oxide – activity & selectivity to propylene

Characterization of the supported vanadia species on the AAO membrane by XAS

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0

10

20

30

40

50

60

70

80

90

100

1 2 3

Conversion of propane Conversion of oxygenCO2 COPropylene

Co

nve

rsio

n-

Sel

ecti

vity

(%

)

Selectivity to propylene at 500°C: Membrane (60 %) > Powder (25 %)

470 °C 500 °C 500 °C

VOx/Al2O3/AAO Membrane catalyst

VOx/Al2O3 Powder catalyst

Selectivity improves moving to membrane

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V-loading: S (propylene)80 % vs. 35 %

For ~ V-loading Selectivity to propylene:

2 ML VWI > 2 ML ALD

0

10

20

30

40

50

60

70

80

90S

ele

cti

vit

y (

%)

1/2 ML ALD Al2O3 8.5 V/nm2

1 ML ALD Al2O3 14.5 V/nm2

2 ML WI Al2O3 16 V/nm2

CO2

CO

propylene

1 ML V8.5 V/nm2

2 ML V IWI 16 V/nm2

Sel

ecti

vity

to

pro

pyl

ene

(%)

2 ML V

14.5 V/nm2

Selectivity

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Support Effects

ActivityTiO2 > Al2O3 > Nb2O5

0

0.005

0.01

0.015

0.02

0.025

520 530 540 550 560 570 580

Reaction temperature

Act

ivit

y (m

ol

C3H

8 c

on

vert

ed.m

in-1.g

V-1)

Nb2O5

TiO2

Al2O3

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Selectivity to Propylene

Selectivity to propyleneAl2O3 > Nb2O5 > TiO2

Sel

ecti

vity

to

pro

pyl

ene

(%)

0

10

20

30

40

50

60

70

80

90

1/2 ML ALD Al2O3 8.5 V/nm2

1 ML ALD Nb2O5 10 V/nm2

1 ML ALD TiO2 7.5 V/nm2

CO2

CO

Propylene

1 ML ALD Al2O3

8.5 V/nm2

1 ML ALD TiO2 7.5 V/nm2

1 ML ALD Nb2O5

10 V/nm2

530 °C

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X-ray Absorption Fine StructureXAFS = XANES + EXAFS

XANES EXAFS

Type of Central Atom,

Amount, and Oxidation

State

Distance to Neighboring Atoms

Number of Neighboring Atoms

Type of Neighboring Atoms

Ab

sorp

tio

n

X-ray Energy (eV)

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In Situ Cell Design

Kapton Windows

1” Quartz Tube

SS Sample Holder

(~ 0.5 cm2)

Gas Flow Valves

SS Flanges

Thermocouple

X-raypath

Gas In

Gas Out Design allows for wide range of

reactive conditions

– Temperature controlled to provide ramping and rapid temperature changes

– Effluent gas can be monitored by GC, MS, etc.

– Transmission or Fluorescence mode

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ODH Membranes (XANES)

0.0

0.5

1.0

5440 5460 5480 5500 5520 5540

E (eV)

No

rma

lize

d µ

(E)

0.7 eV

Al2O3 – 1c V2O5

Al2O3 – 2c V2O5

Al2O3 – 3c V2O5

TiO2 – 2c V2O5

Nb2O5 – 1c V2O5

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Conclusion

VOx/Al2O3/AAO membrane catalyst

– Higher selectivity to propylene than conventional VOx/Al2O3 powder catalyst

• 60 % vs. 25 % For membrane catalyst prepared by ALD

– ODH activity of propane increases as the VOx loading increases

– Attributed to the formation of polyvanadates species (V-O-V bonds)

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Conclusion

The selectivity to propylene depends on– Amount of V- loading

• 1 ML ALD (80 %) > 2 ml ALD (35 %)– Method of Vanadium deposition

• 2 ML VWI (63 %) > 2 ML ALD (35 %)– Chemistry of the support

• Al2O3 (80 %) > Nb2O5 (55 %) > TiO2 (45 %).

The lower selectivity to propylene (Nb2O5 & TiO2) correlated to the pre-edge feature in the XANES spectra.

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Questions ??