Catalytic Processes for the Production of Chemicals and Fuels

from Biomass Carsten Sievers

October 1, 2014Atlanta, GA

Platform Compound from Biomass

GlucoseVery low vapor pressure

GlycerolBoiling point: 290 °C

5-Hydroxymethylfurfural (HMF)Boiling point: 114-116 °C at 1 Torr

SorbitolBoiling point: 295 °C

HO

OH

OH

OH

OH

OH

OH

OH

HO

O

HOO

O

OH

OHOH

HOHO

Many processes for biomass conversion will occur in solution – in particular in water. Catalysts with a sufficient hydrothermal stability are needed. Reactants compete with water of surface sites.

Requirements for CatalystsStability

Specific and uniform active sites ActivityFast processesSelectivity

Affordable materialsEase of separation Reusability

Predictable kinetics Process models

Stability of γ-Al2O3Based Catalysts in Hot

Liquid Water

2θ / °

ppm

ppm

t / h

t / h

R.M. Ravenelle, J.R. Copeland, W.-G. Kim, J.C. Crittenden, C. Sievers, ACS Catal. 1 (2011) 552.R.M. Ravenelle, J.R. Copeland, A. Van Pelt, J.C. Crittenden, C. Sievers, Top. Catal. 55 (2012) 162.R.M. Ravenelle, F.Z. Diallo, J.C. Crittenden, C. Sievers, ChemCatChem 4 (2012) 492.A.L. Jongerius, J.R. Copeland, G.S. Foo, J.P. Hofmann, P.C.A. Bruijnincx, C. Sievers, B.M. Weckhuysen, ACS Catalysis 3 (2013) 464.

Hydrolysis of Alumina Supportsγ-Al2O3

Pt/γ-Al2O3 or Ni/γ-Al2O3

In hot liquid water, alumina supports are converted to boehmite. During this process, the structure collapses and favorable properties are lost. Metal particles delay the initial stage of boehmite formation.

R.M. Ravenelle, J.R. Copeland, W.-G. Kim, J.C. Crittenden, C. Sievers, ACS Catal. 1 (2011) 552.

R.M. Ravenelle, J.R. Copeland, A. Van Pelt, J.C. Crittenden, C. Sievers, Top. Catal. 55 (2012) 162.A.L. Jongerius, J.R. Copeland, G.S. Foo, J.P. Hofmann, P.C.A. Bruijnincx, C. Sievers, B.M. Weckhuysen, ACS Catalysis 3 (2013) 464.

Carbonaceous Layers

γ-Al2O3

Protective carbonaceous

layerMetal particle

Polyols and lignin oligomer can form protective layers of carbonaceous deposits on the surface of alumina.

Accessibility of metal particles is essential for catalytic performance. Hydrogen chemisorption shows that 40% of the metal surface area remain

accessible. Alternatively, stabilization can be achieved with additives in the alumina support.

Surface Chemistry of Glycerol

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.J.R. Copeland, I. Santillan, S.M. Schimming, J.L. Ewbank, C. Sievers, J. Phys. Chem. C 117 (2013) 21413.

G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, ACS Catalysis 4 (2014) 3180.

H1

C1

O3

H2

H3H4

H5

H6

H7

H8

C2C3

O1

O2

O4

Al1Al2

Upgrading of Glycerol

B. Katryniok, S. Paul, M. Capron, F. Dumeignil, ChemSusChem 2 (2009) 719-730.A. Alhanash, E.F. Kozhevnikova, I.V. Kozhevnikov, Catal. Lett. 120 (2008) 307.

Dehydration of glycerol can provide acrolein and acetol (hydroxyacetone).

The initial dehydration step determines the selectivity.

Acrolein is an important intermediate in the chemical and agricultural industry.

Transmission IR in vacuumHeating

WireThermocouple

To UHV Chamber

Sample Holder

Wafer

Cell Body

Front View

IR Beam

ZnSeWindow

Side View

Method: Ex-situ, wet impregnation of catalyst

with aqueous polyol solutions Removal of co-adsorbed water in air

and vacuum

SlurryImpregnated

γ-Al2O3Wafer

“Dry” Press

(30% water)

γ-Al2 O

3

Polyol in w

ater

IR Studies on Surface Interactions of Polyols

Surface Interactions of Glycerol on γ-Al2O3

1200 1150 1100 1050 1000 Wavenumber / cm-1

11511124

11081075 1030

RTPHV

Pure glycerol

H2O

J.R. Copeland, X.-R. Shi, D.S. Sholl, and C. Sievers, Langmuir, 29 (2013) 581.

HO

H

C

OHO

CC

HH

HH

H2OH2OOH

H

C

OHO

CC

HH

HHVacuum

OHOH

H2O Vapor

OH

H

C

OHO

CC

HH

HH

H2OH2OGly

cero

l

RT and ambient pressure RT in vacuum H2O Vapor

Al2O3 Al2O3 Al2O3

Further interactions with surface OH groups.

Surface species formed in presence of water remain stable.

Alkoxide species form.Acid-base interactionswith another OH group.

Vibrational Frequencies

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.

Vibrational frequencies calculated by DFT are in good agreement with experiments. To compensate the systematic offset frequencies were scaled with a factor of 1.008.

H1

C1

O3

H2

H3H4

H5

H6

H7

H8

C2C3

O1

O2

O4

Al1Al2

O4 O3

O2 C1C2

C3

Al1 Al2

H2H5

H4

H7

H3H8

H1 H6

b

O4 O3

O2 C1C2

C3

Al1 Al2

H2H5

H4

H7

H3H8

H1 H6

b

Experimental: 1151 cm-1

Theoretical: 1151 cm-1Experimental: 1125 cm-1

Theoretical: 1124 cm-1Experimental: 1083 cm-1

Theoretical: 1090 cm-1

1 2 3

1200 1150 1100 1050 1000Wavenumber / cm-1

1 23

1800 1700 1600 1500 1400 1300 1200 1100 1000 Wavenumber / cm-1

1518 1474

1492

25 °C

350 °C

Increased uptake prevents hydrogen bonding of secondary alcohol group. The peak at 1714 is attributed to the νC=O vibration of acrolein. Peaks at 1518, 1492 and 1474 cm-1 are attributed to the formation of aromatics,

such as phenols.

3 wt% Glycerol on NB350

1614

15751714

1140

1103

1044

O

OH

OH

BAS : LAS = 0.63HO O

OHHO

OHO

HO

HO

HO

G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, ACS Catalysis 4 (2014) 3180.

Glycerol Dehydration over Nb2O5

Lewis acid sites activates the primary alcohol groups. Dehydration only occurs when Brønsted acid sites are present. Dehydration of the secondary alcohol group is preferred over Brønsted acid sites

due to the higher stability of the carbenium ion transition state.G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, ACS Catalysis 4 (2014) 3180.

OH

OHO

OH

HO OH

O

LAS/BAS 2-Propene-

1,2-diolHydroxyacetone

-H2O

1,3-Propenediol

Acrolein

Aromatics

HO OHOH

GlycerolBAS

LAS

O OHOH

Chemisorbed Glycerol

HO O3-Hydroxypropionaldehyde

BAS -H2O

-H+

-OH-

In-situ Studies on Surface Reactions

J.R. Copeland, G.S. Foo, L.A. Harrison, C. Sievers, Catal. Today 205 (2013) 49-59.

Experimental MethodA slurry of Pt/γ-Al2O3 in water is deposited on the ZnSe crystal and the

water is allowed to evaporate, 5 times

Several solutions are used as mobile phaseConcentrations can be variedResponses to stimuli are tracked

In-situ ATR-IR Spectroscopy

Catalyst layer

IR beam To detector

Mobile phase Evanescent wave

ATR crystalOrtiz-Hernandez, I.; Williams, C.T. Langmuir, 2006, 19, 2956-62.

HPLC Pump

Liquid ReservoirsFTIR

Heated ATR-IR CellHeO2H2

Exhaust

HPLC

Time-Resolved Analysis of Intermediates

Different surface species are identified based on their IR spectra. Time-resolved profiles for the concentration of each species can be obtained.

Linear bound CO accumulates until all of its sites are saturated.

J.R. Copeland, G.S. Foo, L.A. Harrison, C. Sievers, Catal. Today, 205 (2013) 49.

0.0

0.5

1.0

1.5

2.0

2.5

0 30 60 90

Inte

grat

ed A

rea

/ Abs

.*cm

-1

Time / min

0.0

0.2

0.4

0.6

0.8

1.0

0 30 60 90

Inte

grat

ed A

rea

/ Abs

.*cm

-1

Time / min

νCOL/H2O νCOB

Gly H2O O2 Gly H2O O2

CO

1777

H H

2000

CO

OH

2

OH

2

Ptγ-Al2O3

Water-Gas Shift

Sites that bind CO in bridging coordination appear to be active for water-gas shift at room temperature.

Adsorbed hydrogen prevents repopulation of some of these sites.

J.R. Copeland, G.S. Foo, L.A. Harrison, C. Sievers, Catal. Today, 205 (2013) 49.

Pt

H2

CO

H2

H2O

Pt

H2O

Pt

H OH

Pt

CO2OHHOOH

CO

CO

H2H2

CO

CO

CO

H2 H2 H2H2

CO

CO

H2 H2 H2H2

H H

Operando IR Studies on DeoxygenationObjectives: Identification of surface species and reaction

pathways in deoxygenation reactions with and without hydrogen

Understanding pathways leading to deactivation

Elucidation of the role of specific active sites in different reactions

Design of highly efficient deoxygenation catalysts

Approach: In-situ IR studies on time-resolved evolution of

surface species under reaction conditions Complementary analysis of reaction products

by online mass spectrometry and offline GC-MS

IR beam

Reactants

Products

1800 1700 1600 1500 1400 1300

1627

15951529

1491

1440

1380

Time

Abso

rban

ce /

a.u

Wavenumber / cm-1

Conclusions Carbonaceous layers can stabilize solid catalysts for reactions in hot

liquid water.

Spectroscopic studies can provide essential insight into surface chemistry of biomass-derived oxygenates.

Understanding such surface interactions is important for many research areas: Heterogeneous catalysis Biomass-based composite materials Glucose sensors Flotation

AcknowledgementsRyan RavenelleJohn CopelandGuo Shiou FooSarah SchimmingJessica EwbankLindsey HarrisonIvan Santillan

Christopher JonesSankar NairKrista WaltonJohn CrittendenJohannes LeisenXuerong ShiDavid Sholl

Funding:

GT startup funds

GT Strategic Energy Institute

Brook Byers Institute for Sustainable Systems

Department of Energy

Department of Energy Report (2005)

Hirsch, R.L., Bezdek, R., Wendling, R. “Peaking of World Oil Production: Impacts, Mitigation & Risk Management”, DOE report, 2005.

World oil peaking is going to happen, and it will be abrupt and revolutionary.

Oil peaking will adversely affect global economies, particularly those most dependent on oil.

The problem is liquid fuels (growth in demand mainly from the transportation sector).

Mitigation efforts will require substantial time - 20 years is required to transition without substantial impacts

Late initiation of mitigation may result in severe consequences.

Both supply and demand will require attention.

Government intervention will be required.

Biomass – A Sustainable FeedstockAvailability of biomass (without affecting food and feed production):US production capacity (per year):4.7 .108 metric tons 1.4 .109 barrel of oil equivalents (boe)

Current oil consumption in the US:7.109 barrels per year

Up to 20% of the of the oil currently consumed could be replaced by biomass.

With improved biomass production, this fraction could increase to 46% by 2030.

Sugar cane Corn

LignocellulosicSoy beans

Lignocellulosic biomass can be produced in the US for $60 per barrel of oilequivalent.

L. Park Ovard, T.H. Ulrich, D.J. Muth, J.R. Hess, S. Thomas, and B. Stokes. 2011. U.S. Billion-Ton Update: Biomass Supply for a Bioenergy and Bioproducts Industry. In U.S. DOE report. Oak Ridge National Laboratory.

Conversion of Biomass FeedstocksGasification to syngas (CO + H2)

Fischer Tropsch Alkanes or mixed alcoholsWater-gas shift reaction HydrogenMethanol synthesis

Bio-oil production by pyrolysisZeolite upgrading or HDO Alkanes and Aromatics

Controlled depolymerization to platform moleculesFermentationChemical reactions to fuels or chemicalsTransesterification

G.W. Huber, S. Iborra, A. Corma, Chem. Rev. 106 (2006) 4044-4098.

O

O

O

O

O

O

O

O

O

O

O

O

Acid or base catalyst

OH

OH

OH+

+CH3OH

CH3OH

CH3OH

Biodiesel Production from Triglycerides

Triglycerides are converted into esters (up to 99.7 % yield) and glycerol. All reaction steps are reversible Excess alcohol required.

Large amounts of glycerol are produced as byproduct. Conversion of glycerol to value added chemicals is crucial for the commercial

success of biodiesel.

Aqueous Phase Chemistry

The ion product of water increases up to ca. 270 °C and decreases as the temperature increases further.Increasing temperature also leads to: Increasing vapor pressureDecreasing dielectric constant of waterDecreasing extent of hydrogen bonding Increasing volume of the hydration spheres around ionic species

W.L. Marshall, E.U. Franck, J. Phys. Chem. Ref. Data 10 (1981) 295.

10

11

12

13

14

15

16

0 50 100 150 200 250 300 350

pKW

Temperature / °C

Self-dissociation of water

H+H

OH

HO

H

HO H

HOH

H

OH

HO

H

H OH

HO

H HO H H

O HHO

HO

H

H

OHHO

H

HH

Frank, H. S.; Evans, M.W. J. Chem Phys. 1945, 13, 507.

Primary hydration sphere: water molecules are tightly bound to the ion through electrostatic forces.

Secondary hydration sphere: water molecules have not direct contact to the ion but are influenced by its charge.

Bulk: water molecules are not influenced by the presence of the ion.

Association of Water at High Temperature

The entropy of molecules in the first and second hydration sphere is lower than that of uncoordinated water molecules. At high temperatures the reaction H+ + OH- H2O becomes more favorable.

Composition of Biomass

HCCH

OHC [CH2OH]

H3COO CH

CH2OH

CHOH

O CHCH2OH

HC O

OCH3H2COCH

H3COO CH

CH2OH

CHOH

H3COOH OH

OCH3

C

[O C]

OHC O

CH2OHH3CO

CHOHHC

CH2OHO

H3CO O

CHOHCH

H3CO

HOCH2OH

OCH3

HC O CH2

CHHCH2C CH

O

OCH3OH

OCHHOH2C C

O

HH3CO

CHOHHC O

CH2OH

H3CO OCH3

CHOHHC

CH2OHO

OCH3

CHOHCH

OH

CHOH3CO HC O

CH2OH

CH2

CH2

CH3

CH2OH

O

OO

OO

OO

OOHO

HOH2 C

OH

HOH2 CHO

HO

OH

OH

HO

HOH2 C HOH2 C

OH

O

OO

OO

OO

HOH2C

OHHO

OO RO

RO

OH

ROOR

OH

OR

HO

HOH2C

HOH2C

OH2C

O

OROH

HOH2C

Cellulose

Hemicellulose

Lignin

Triglycerides

O

O

O

O

O

O

Aqueous Phase Reforming

R.D. Cortright, R.R. Davda, J.A. Dumesic, Nature 418 (2002) 964.G.W. Huber, J.W. Shabaker, J.A. Dumesic, Science 300 (2003) 2075.G.W. Huber, R.D. Cortright, J.A. Dumesic, Angew. Chem.-Int. Ed. 43 (2004) 1549.

Aqueous Phase Reforming (APR) is used to convert sugar alcohol to hydrogen and/or alkanes.

High hydrogen yields are obtained over catalysts with a high activity for C-C bond cleavage (e.g. Pt, Ni).

Alkanes are produced by a combination of acid catalyzed dehydration and metal catalyzed hydrogenation.

Alkane Route

13H2 + 6CO2

Raney Nickelor

Pt/Al2O3

225 - 265°C

Hydrogen Route

Sorbitol

+ 6H2O

Catalyst: Pt or Pd on Al2O3 or SiO2-Al2O3

Hydrolysis of Carbohydrates

OH

OH

H

H

OHH

H

OH

OO

OH

H

H

OHOHH

H

OH

O

HO

H

OH

H

H

OHOHH

H

OH

H2O

[H+]

OH

H

O

HO

H

OH

H

H

OHOHH

H

OH

Carbohydrates can be hydrolyzed using enzymes or mineral acids as catalysts.

Monomeric sugars can be converted to chemicals and fuels in catalytic processes or fermentation.

APR: Open questions

Pt

H2

CO

H2

H2O

Pt

CH3OHH2O

Pt

H2

CO H2

OHH

Pt

H2

CO2

H2H2

How does the composition and size of metal particles affect the rate of formation and conversion of CO?

What influence do co-adsorbed reactants and products have? Why is APR of larger oxygenates less efficient? How can we stabilize the catalysts under reaction conditions?

C3H8O3 3H2O 3CO2 7 H2Glycerol:

Surface Interactions

H

O

HH

OH

OH H

H

H

Metal particle

Pore wall

Dispersive and Directed Forces

Adsorption of alkanes on faujasite type zeolites is dominated by dispersive van-der-Waals forces.

Interaction with Brønsted acid sites adds ca. 6 kJ/mol to Hads. At high uptake sorbate-sorbate interactions contribute to the heat of adsorption. Directed interactions play an important role when functional groups can interact with

specific surface sites.F. Eder, J.A. Lercher, Zeolites 18 (1997) 75.

C. Sievers, A. Onda, R. Olindo, J.A. Lercher, J. Phys. Chem. C 111 (2007) 5454.

0102030405060708090

3 4 5 6 7 8 9Carbon number

Hea

t of a

dsor

ptio

n / k

J.m

ol-1

LaXHY (2.7)FAU (300)

Adsorption of n-alkanesAdsorption of n-alkanes

Adsorption of Polyols on Zeolites

The Henry (Kads) constant increases exponentially with increasing carbon number of diols.

Additional hydroxyl groups reduce Kads. Adsorption of polyols on zeolites is controlled by dispersion forces. The polarity of the framework only affects adsorption in large pore zeolites.

E.E. Mallon, A. Bhan, M. Tsapatsis, J. Phys. Chem. B 114 (2010) 1939.

1,2-Butane-diol

1,2-Propylene-glycol

Ethylene glycol

Diols on MFI Silicalite-1 Kads for 1,2-propylene glycol

Adsorption Isotherms

♦ = Ethylene Glycol■ = 1,2-Propanediol▲ = 1,3-Propanediol● = Glycerol

Polyol uptake on γ-Al2O3 is limited. Measurable uptake is only observed at high glycerol concentrations.

The limited uptake is attributed to competitive adsorption of water and glycerol. Continuous exchange between water and glycerol appears to occur on the surface.

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 200 400 600 800Concentration / mM

Upt

ake

/ mm

ol/g

Cat

alys

t

ZSM-5 (Si/Al = 60)

γ-Al2O3

Adsorption isotherm based on HPLC analysis of solutions.T = 25 °Ct = 4 h

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.

2H “Pake” NMR of Oxygenates on Al2O3

Sharp lines indicate mobile species, broad lines immobilized species. D4-Ethylene glycol Surface interactions strongly depend on co-adsorbed water.

D5-Glycerol Co-adsorbed water has less of an influence.

2000 0 -2000 Frequency / Hz

2000 0 -2000 Frequency / Hz

D4-Ethylene glycol

D5-Glycerol

Dry Air FlowHumid Air Flow

Ambient T and P

D

OH

OH

HO

DD

DD

CCC

OH

D

C

OH

CD D

D

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.

Glycerol on γ-Alumina

Changes in CH2 stretching bands.New C-O stretching modes at 1151, 1125, and 1081 cm-1

indicate strong surface interactions of the OH groups in glycerol.

Alkoxy bonds form in presence of water and remain stable when water is reintroduced.

The changes in the νCO region do not necessarily correlate with change in the νOH region.

Estimated loading: ¼ monolayer

1800 1600 1400 1200 1000

1650

HV

RTP

Glycerol

1151 1125 1080

1108 993 1030

1458

3000 2900 2800 2700 2600

2933

2880

H

OH

OH

HO

HH

HH

C

CC

1108

1030 1030

993 993 1458 1458

Wavenumber / cm-1

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.

Specific Adsorption Sites

Coordinatively unsaturated, Lewis acidic AlIII sites can exist even in the presence of a certain amount of water.

The presence of AlIII sites becomes less favored as the amount of adsorbed water increases.

It is likely that CUS sites exist as transient species with a finite lifetime. Certain polyols can replace surface bound water with stable multi-dentate surface

species.R. Wischert, C. Coperet, F. Delbecq, P. Sautet, Angew. Chem.-Int. Ed. 50 (2011) 3202.

Adsorption of Oxygenates

OH

H

C

OH

CH H

H

OHOHH2O H2O

H

CCH H

H

HOO

Vacuum

OHOH

H2O VaporH

CCH H

H

OHOH2O H2O

RT and ambient pressure RT in vacuum H2O Vapor

Eth

ylen

e G

lyco

l

Weak physisorption of ethylene glycol.

Alkoxy bonds form.Further interaction with surface OH groups.

Bridging alkoxide remains.Linear bond disappears. Chemisorption is partially reversible.

Al2O3 Al2O3 Al2O3

J.R. Copeland, X.-R. Shi, D.S. Sholl, C. Sievers, Langmuir 29 (2013) 581.

HO

H

C

OHO

CC

HH

HH

H2OH2OOH

H

C

OHO

CC

HH

HHVacuum

OHOH

H2O Vapor

OH

H

C

OHO

CC

HH

HH

H2OH2OGly

cero

l

RT and ambient pressure RT in vacuum H2O Vapor

Al2O3 Al2O3 Al2O3

Further interactions with surface OH groups.

Surface species formed in presence of water remain stable.

Alkoxide species form.Acid-base interactionswith another OH group.

Boehmite

X-Ray Diffraction 27Al MAS NMRUntreated

1 h

2 h

6 h

4 h

10 20 30 40 50 60 70 2θ / °

10 h

10 20 30 40 50 60 70 2θ / °

Al Al

100 80 60 40 20 0 -20 -40 -60 Chemical shift / ppm

0 h

1 h

2 h

4 h

6 h

10 h

Stability of γ-Al2O3 in Hot Water

γ-Al2O3 is converted into boehmite. At 200 °C the conversion is completed within 10 h.

R.M. Ravenelle, J.R. Copeland, W.-G. Kim, J.C. Crittenden, C. Sievers, ACS Catal. 1 (2011) 552.

Kinetics based on27Al MAS NMR

Metal particles delay the formation of boehmite.

The transformation accelerates after 6 h.

0

20

40

60

80

100

0 2 4 6 8 10

Boe

hmite

fract

ion

/ %

Treatment time / h

γ-Al2O3 Ni/γ-Al2O3

Pt/γ-Al2O3

Stability in Polyol Solutions

10 20 30 40 50 60 70 2θ / °

Untreated

5% sorbitol

5% glycerol

water

1 wt% Pt/Al2O3, 10 h, 225 °C

Polyols stabilize γ-Al2O3 in hot liquid water.

The effect is more pronounced for sorbitol.

100 80 60 40 20 0 -20 -40 -60 Chemical shift / ppm

Sample Boehmite / %1 % Pt/Al2O3 H2O 100

1 % Pt/Al2O3 Glycerol 151 % Pt/Al2O3 Sorbitol 2

R.M. Ravenelle, J.R. Copeland, A. Van Pelt, J.C. Crittenden, C. Sievers, Top. Catal. 55 (2012) 162.

XRD 27Al MAS NMR

Surface AreaBET Surface Area (N2 physisorption)

Active metal surface area (H2/O2 titration)

BET

sur

face

are

a / m

2· g

-1

Acce

ssib

le m

etal

sur

f. ar

ea /

m2 ·

g-1

0

20

40

60

80

100

120

0.0

0.4

0.8

1.2

1.6

2.0

The BET surface are remained constant during treatment with polyol solution. The accessible metal surface area decreased by ca. 60%. TEM indicated that the decrease is due to blockage rather than sintering. Dramatic sintering was observed during treatment in pure water.

1 wt% Pt/Al2O3Treated water or polyol solutiont =10 h T = 225 °C

R.M. Ravenelle, J.R. Copeland, A. Van Pelt, J.C. Crittenden, C. Sievers, Top. Catal. 55 (2012) 162.

Influence of Lignin Derived Compounds

after 4 h

1 g of 1 wt% Pt/Al2O3Treated in ethanol/water and oxygenate solutionsT = 225 °C, t =4 h

A stabilizing effect is also observed in the presence of lignin-derived oxygenates. Multi-dentate surface species appear to be necessary for effective stabilization.

X-Ray Diffraction

A.L. Jongerius, J.R. Copeland, G.S. Foo, J.P. Hofmann, P.C.A. Bruijnincx, C. Sievers, B.M. Weckhuysen, ACS Catalysis 3 (2013) 464.

Surface Chemistry of Glycerol on Acidic and

Basic Metal Oxides

J.R. Copeland, I. Santillan, S.M. Schimming, J.L. Ewbank, and C. Sievers, J. Phys. Chem. C 117 (2013) 21413.G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, ACS Catalysis, accepted.

Interactions of Glycerol with Metal Oxidesγ-Al2O3

Lewis acidic Weak base sites

ZrO2 Few Lewis acid sites Moderate base sites

TiO2 Few Lewis acid sites Moderate base sites

MgO No strong acid sites Strong base sites

Goals: Understand the role of acidity/basicity in surface interactions with oxygenates. Identify dominant surface species.

CeO2 Lewis acid sites Moderate base sites Redox active

J.R. Copeland, I. Santillan, S.M. Schimming, J.L. Ewbank, C. Sievers, J. Phys. Chem. C 117 (2013) 21413.

Polarization of Surface Species

The frequencies of the primary νCO vibrations increases linearly with increasing electronegativity of the metal atom.

This indicates increasing polarization of the C-O bond with increasing EN.

δ+ δ+δ-δ-

1040

1070

1100

1130

1.00 1.25 1.50

νCO

Freq

uenc

y /

cm-1

Metal Atom Electronegativity

γ-Al2O3 (♦)basic γ-Al2O3 (■)TiO2 (▲)ZrO2 (Χ)Alfa ZrO2 (○)CeO2 (+)

J.R. Copeland, I. Santillan, S.M. Schimming, J.L. Ewbank, and C. Sievers, J. Phys. Chem. C 117 (2013) 21413.

Synthesis and Characterization of Nb2O5Synthesis: Niobic acid (CBMM) was calcined at different temperatures to form Nb2O5. Named as NBX, where X is the calcination temperature. Na+/Nb2O5 was synthesized by ion-exchange with NaCl in aqueous NaOH.

020406080

100120140160180200

Conc

entr

atio

n (μ

mol

/g)

Concentration of Lewis and Brønsted Sites

Lewis sites

Brønsted Sites

00.020.040.060.080.10.120.140.160.18

0

20

40

60

80

100

120

300 400 500 600 700 800

Pore

Vol

ume

(cm

3 /g)

Surf

ace

Area

(m2 /g

)

Calcination Temperature (°C)

N2 Physisorption

BET Surface AreaPore Volume

(0.71)

(0.63)(0.60)

(0.14)(0.06)

(0)

(0)

Surface area, pore volume, and acid site concentration decrease with increasing calcination temperature.

Brønsted acid sites are removed at lower temperatures than Lewis acid sites.

G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, ACS Catalysis, accepted.

Selectivity for Dehydration of Glycerol

5

10

15

20

25

0.5 1 1.5 2 2.5

Sel

ectiv

ity to

Hyd

royx

acet

one

(%)

Lewis acid density (μmol/m2)

NB700

NB350

NB400 NB500

NB600(A)

20

30

40

50

60

0 0.1 0.2 0.3 0.4 0.5 0.6

Sel

ectiv

ity to

Acr

olei

n (%

)

Brønsted acid density (μmol/m2)

NB350

NB400

NB700

NB600 NB500

(B)

G.S. Foo, D. Wei, D.S. Sholl, C. Sievers, submitted.S.H. Chai, H.P. Wang, Y. Liang, B.Q. Xu, J. Catal. 250 (2007) 342.

The selectivity to hydroxyacetone scales linearly with the density of Lewis acid sites.

The selectivity to acrolein scales linearly with the density of Brønsted acid sites.

Brønsted acid sites can be formed from Lewis acid sites at elevated temperature in the presence of steam.

Fixed bed reactorT = 315 °CFeed: 36.2 wt%

glycerol in H2OGHSV = 80 h-1

Aqueous Phase Reforming: Mechanism

Aqueous phase reforming consists of decomposition of oxygenates to form CO and hydrogen followed by water-gas shift.

CO and H adsorb strongly on the metal surface. Co-adsorbed reactants and products seem to affect the surface reaction. Kinetic studies on these surface reactions are needed for efficient

catalyst design. R.D. Cortright, R.R. Davda, J.A. Dumesic, Nature 418 (2002) 964.G.W. Huber, J.W. Shabaker, J.A. Dumesic, Science 300 (2003) 2075.R. He, R.R. Davda, and J.A. Dumesic, J. Phys. Chem. B 109 (2005) 2810-2820.

Pt

H2

CO

H2

H2O

Pt

CH3OHH2O

Pt

H2

CO H2

OHH

Pt

H2

CO2

H2H2

C3H8O3 3H2O 3CO2 7 H2Glycerol:

Glycerol is converted over Pt/Al2O3 to linearly bound and bridging CO as well as surface bound hydrogen.

Dissolved O2 oxidizes surface bound hydrogen and CO. Co-adsorbed hydrogen reduces the number of sites for CO. Kinetic studies require a reproducible pretreatment procedure.

2050 1950 1850 1750

Glycerol on partially oxidized Pt/γ-Al2O3

2000

2067

1777

Wavenumber / cm-1

Linearly bound CO

Bridging COLinearly boundCO near H

J.R. Copeland, G.S. Foo, L.A. Harrison, C. Sievers, Catal. Today, 205 (2013) 49.

Pt/Al2O30.3 M glycerol in waterFlow rate: 1 ml/minRoom temperature

Glycerol on Pt/Al2O3

CO

H

2067

H CO

1777

H H

2000

CO

OH

2

OH

2

Ptγ-Al2O3

Pretreatment of catalyst layers is required prior to in-situ IR studies. Dissolved O2 and H2 remove deposits from the surface of the catalyst.

Surface Species and Pretreatment

I. Ortiz-Hernandez, D.J. Owens, M.R. Strunk, C.T. Williams, Langmuir 22 (2006) 2629.D. Ferri, T. Bürgi, A. Baiker, J. Phys. Chem. B 105 (2001) 3187.

Peaks at 2060 and 1990 cm-1 are observed during pretreatment with H2. Almost identical spectra are observed upon reduction with D2. The peaks are assigned to linearly bound CO in the vicinity of hydrogen

and water, respectively.

Hydrogen Yield from Glucose

The hydrogen yield from glucose is significantly lower than the hydrogen yield from fructose.

Side reactions, such as dehydration and retro-aldol condensation, play a more significant role during APR of glucose.

These side reactions are much less pronounced with the glucose concentration is kept low.

Davda, R. R.; Dumesic, J. A. Chem. Commun. 2004, 36.Kabyemela, B. M.; Adschiri, T.; Malaluan, R. M.; Arai, K. Ind. Eng. Chem. Res.1999, 38, 2888.

Conversion of Different Oxygenates

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

0 10 20 30

Inte

gral

Are

a / A

bs*c

m^-

1

Time / min

Glycerol

Glucose

Sorbitol

Initial rate of zero indicates that CO is formed as secondary product. Rate of CO formation decreases in the order glycerol > glucose > sorbitol. The observations support the formation of aldehydes as intermediates.

Linearly bound CO on Pt/Al2O3

Glycerol

Sorbitol

Glucose

1 wt% Pt/Al2O30.3 molar oxygenate solution in water

T = 25 °CP = 1 atm

Path Forward: ATR-IR We recently competed the construction of an in-situ ATR IR cell for reactions at high

temperature. Operating conditions:

Room temperature and pressure up to 200 °C and >20 bar 0.000 to 10.000 ml/min

Pressure around the IRE kept constant by N2

Eliminates pressure gradient across the IRE.

Precise temperature control Feed preheater (not shown) Two independent control

zones around IRE All components are removable Can change IRE for optical

purposes Easily replaced Easily upgraded

Feed InletEffluent

N2 Inlet

IR InletIR Outlet

TC

Heating Element

Gasket

Window

IRE