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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