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The Route to Better Catalysts:From Surface Science to Nanotechnology
by Francisco Zaera
Department of ChemistryUniversity of California
Riverside, CA 92521, USAPhone: 1 (951) 827-5498
Fax: 1 (951) 827-3962Email: zaera@ucr.edu
http://www.zaera.chem.ucr.edu
Haldor Topsøe Catalysis ForumMunkerupgaard, Denmark
August 27, 2015
1
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
F. Zaera, J. Phys. Chem. B, 106(16), 4043-4052 (2002).F. Zaera, Catal. Lett., 142(5), 501-516 (2012).
A selective process:• Consumes less reactants
• Avoids separation problems• Produces less polluting byproducts
2
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
IntroductionKey Issues in Catalysis
∆G°
Reactant
Product 1 Product 2
Selectivity Stability
T, Gases
Sintering:• Reduces surface area
• modifies surface structure• Requires priodic catalyst recycling
F. Zaera, Chem. Soc. Rev., 42(7), 2746-2762 (2013).F. Zaera, ChemSusChem, 6(10), 1797-1820 (2013).
F. Zaera, Prog. Surf. Sci., 69(1-3), 1-98 (2001).F. Zaera, Int. Rev. Phys. Chem., 21(3), 433-471 (2002).
F. Zaera, J. Phys. Chem. Lett., 1(3), 621-627 (2010).
Surface Science withModel Systems
3
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
IntroductionExperimental Approach
• Well-defined samples• Controlled environments
• Multiple techniques
Nanotechnology toPrepare Real Catalysts
1 nm
Outline
4
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
1. Surface Science of Olefin Hydrogenation
2. Shape Selectivity
3. Catalyst Nano-Architectures
A
B
Outline
5
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
1. Surface Science of Olefin Hydrogenation
2. Shape Selectivity
3. Catalyst Nano-Architectures
Surface Chemistry of Olefin ConversionHydrogenation, Isomerization, and H-D Exchange
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
H3C CH3C=CHH
cis-2-buteneH3C
CH3C=CH
H
trans-2-butene
C–C
butane
CH3H
H
H3CH
H
HC2H5C=CH
H
1-butene
2-butyl (ads)
H3C CH3C HH CH
Hydrogenation
Cis-TransIsomerization
Double BondMigration
Horiuti-Polanyi mechanism. Does not account for:effect of coadsorbed H, carbonaceous layers, stereoselectivity.
M. Polanyi, J. Horiuti, Trans. Faraday Soc., 30, 1164-1172 (1934).F. Zaera, Catal. Lett., 91(1-2), 1-10 (2003).
6
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
F. Zaera, Langmuir, 12(1), 88-94 (1996).
Surface Chemistry of Olefin ConversionHydrogenation under UHV: TPD
Olefin hydrogenation and H-D Exchange easily detected by
temperature programmed
desorption (TPD).
Not catalytic.
7
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
F. Zaera, T. V. W. Janssens and H. Öfner, Surf. Sci., 368(1-3), 371-376 (1996).H. Öfner and F. Zaera, J. Phys. Chem. B, 101(3), 396-408 (1997).
Surface Chemistry of Olefin ConversionHydrogenation under UHV: Molecular Beam
Ethylene can be hydrogenated with H2-rich molecular beams,
but not catalytically.
8
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Surface Chemistry of Olefin ConversionModel of Working Catalyst Surface
F. Zaera, Isr. J. Chem., 38, 293-311 (1998).F. Zaera, Catal. Lett., 91(1-2), 1-10 (2003).
Olefin hydrogenation takes place not on clean metalsbut in the presence of a carbonaceous layer (alkylidynes).
Ethylidyne
-Ethylene
Ethylene Hydrogenation
9
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
A. Tillekartne, J. P. Simonovis, M. F. López Fagúndez, M. Ebrahimi, F. Zaera, ACS Catal. 2, 2259-2268 (2012).
Ethylidyne is present on the surface during
ethylene hydrogenation.
Surface Chemistry of Olefin ConversionRAIRS Detection of Alkylidynes In Situ
H H
CH C
s(CH3)Ethylidyne (ads)
10
A. Tillekartne, J. P. Simonovis, M. F. López Fagúndez, M. Ebrahimi, F. Zaera, ACS Catal. 2, 2259-2268 (2012). Francisco Zaera
Department of ChemistryUniversity of California, Riverside
Surface Chemistry of Olefin ConversionKinetics of Hydrogenation and H-D Exchange Catalysis
Fast and extensive ethylene
hydrogenation and H-D exchange catalysis in the presence of the
alkylidyne surface layer.
11
-2 -4 -6 -80
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
F. Zaera, Phys. Chem. Chem. Phys., 29, 11988-12003 (2013).
Surface Chemistry of Olefin ConversionIntermediate Hydrogenation Regime
Log[P/Torr]
-10 -8 -6 -4 -2 0 2 4
UHV
Non catalytic
Rate (-C2H4)1
On clean Pt
Atmospheric P
Catalytic
Rate P(C2H4)0
On alkylidyne/Pt
TOF ~ 1 - 10
PressureGap(???)
Log[Reaction Probability]???
Log[Impinging Rate/ML s-1]
-4 -2 0 2 4 6 8 10
12
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
M. Ebrahimi, J. P. Simonovis, F. Zaera, J. Phys. Chem. Lett., 5, 2121-2125 (2014).
Surface Chemistry of Olefin ConversionHigh-Flux Molecular Beam Kinetics
Indeed, reaction probabilities are high (~70%) in the intermediate pressure range.
13
M. Ebrahimi, J. P. Simonovis, F. Zaera, J. Phys. Chem. Lett., 5, 2121-2125 (2014).Francisco Zaera
Department of ChemistryUniversity of California, Riverside
Less surface alkylidyne at the high H2:HC ratios that display high TOFs:Olefin hydrogenation rate may be limited by carbonaceous layer.
Surface Chemistry of Olefin ConversionCarbonaceous Layer at High TOFs
14
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
A. Tillekartne, J. P. Simonovis, F. Zaera (2015).
Olefin hydrogenation rate may depend on the nature of thecarbonaceous deposits present on the surface.
Surface Chemistry of Olefin ConversionHydrogenation Rate vs. Nature of Alkylidyne
15
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
J. P. Simonovis, F. Zaera (2015).
H-D exchange used to evaluate H2 ads as possible rls.Slower under reaction conditions, alkylidyne vs. clean Pt.
Switchover in H-D exchange TOF at intermediate conversion.
Surface Chemistry of Olefin ConversionHydrogenation vs. H-D Exchange
Switchover inH-D exchange
TOF
End of C2H4Hydrogenation
16
Outline
17
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
1. Surface Science of Olefin Hydrogenation
2. Shape Selectivity
3. Catalyst Nano-Architectures
Shape SelectivityStereoselectivity of Cis-Trans Isomerization
CH3HH CH3
H
CH3H
H3CH
H
H3C CH3C=CHH
cis-2-buteneH3C
CH3C=CH
H
trans-2-butene
cis-2-butene (ads)
H3C CH3C–C HH H
trans-2-butene (ads)
HH3C H
C–C CH3H
2-butyl (ads)
H3C CH3C HH CH
I. Lee and F. Zaera, J. Am. Chem. Soc., 127, 12174-12175 (2005).I. Lee, F. Zaera, Top. Catal., 56(15-17), 1284-1298 (2013).F. Zaera, Phys. Chem. Chem. Phys., 15(29), 11988-12003 (2013).
Isomerization depends on stereoselectivity of -H
elimination step from the alkyl intermediate.
18
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
998, 1200, 1376, 1460 cm-1 peaks
indicatecis-2-butene.
Trans-to-cisisomerization.
I. Lee and F. Zaera, J. Am. Chem. Soc., 127, 12174-12175 (2005).I. Lee, F. Zaera, J. Phys. Chem. C, 111, 10062-10072 (2007).
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Shape SelectivityTrans-to-Cis Conversion on Pt(111): IR Evidence
19
1 nm
T. S. Ahmadi, Z. L. Wang, T. C. Green, A. Hanglein, M. A. El-Sayed, Science, 272, 1924-1926 (1996).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).
(111)facets
Tetrahedral Pt Particles
Pt(111)
Pt(111)
Pt(100)
1 nm
Cubic Pt Particles(100)facets
20
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Shape SelectivityPreparation of Shape-Selected Pt Nanoparticles
H2H2PtCl6
PVP
Pt ColloidalParticle Preparation
+ SiO2
Sonication
Rinsing
Drying
Dispersion onSilica Xerogel
Calcination
Oxidation/Reduction
CatalystPretreatment
I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).
Shape SelectivitySupported Shape-Selected Pt Catalysts: Preparation
21
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
I. Lee, F. Delbecq, R. Morales, M. A. Albiter, and F. Zaera, Nature Mater., 8, 132-138 (2009).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).
10 nm
Shape SelectivityPreservation of Nanoparticle Shape during Treatment
3 oxidation-reduction cycles at 475 K
10 nm
3 oxidation-reduction cycles at 575 K
22
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
H3CCH3C=CH
H
trans-2-butene
H3C CH3C=CHH
cis-2-butene
Shape SelectivityButene Cis-Trans Catalytic Selectivity
I. Lee, F. Delbecq, R. Morales, M. A. Albiter, and F. Zaera, Nature Mater., 8, 132-138 (2009).I. Lee, R. Morales, M. A. Albiter, and F. Zaera, Proc. Nat. Acad. Sci., 105, 15241-15246 (2008).
23
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Trans fats in partially hydrogenated oils have been linked to a variety of free radical and degenerative conditions such as cancer, arthritis, and
cardiovascular disease.
24
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Shape SelectivityOlefin Cis-Trans Isomerization Relevance
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Y. Zhu, F. Zaera, Catal. Sci. Technol., 4, 955-962 (2014).Y. Li, F. Zaera, J. Catal., 326, 116-126 (2015).
Size and shape sensitivity also seen in:• Unsaturated aldehyde (cinammonaldehyde) hydrogenation
• Glycerol oxidation
Shape SelectivityOther Reactions
25
Outline
26
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
1. Surface Science of Olefin Hydrogenation
2. Shape Selectivity
3. Catalyst Nano-Architectures
A
B
Metal Particle StabilizationIn-Situ Growth of Support Around Metal Particles
Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).
EtchingMeso-SiO2 CoatingPt-Deposition
Pt TEOS NaOH
TEOS NaOH
27
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Metal Particle StabilizationXPS and CO-IR Titration Characterization
74.2
73.8
PtO
CO/SiO2
2116
2089
2085
CO/BeadTEOS
NaOH
Pt surface becomes available again after etching.
28
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).
29
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).
Metal Particle StabilizationStability and Reactivity
Stable toward CO adsorptionHigher reactivity after etching.
TEM after CO ads
60 min
40 min
No etching
NaOH
NaOH
Metal Particle StabilizationThermal Stability
Mesoporous layer stops Pt sintering.
300 K 875 K 975 K 1075 KN
aked
Cov
ered
30
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Q. Zhang, I. Lee, J. Ge, F. Zaera, Y. Yin, Adv. Funct. Mater., 20(14), 2201–2214 (2010).I. Lee, J. Ge, Q. Zhang, Y. Yin, F. Zaera, Nano Research, 4(1), 115-123 (2011).
Yolk-ShellNanostructures
Shaped Nanoparticles
Catalysts fromDendrimers
31
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Catalyst Nano-ArchitecturesTandem Catalysis
Self-AssembledMonolayers
Tethering of MolecularFunctionality
Atomic LayerDeposition
Yolk-ShellNanostructures
Shaped Nanoparticles
Catalysts fromDendrimers
32
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Catalyst Nano-ArchitecturesTandem Catalysis
Self-AssembledMonolayers
Tethering of MolecularFunctionality
Atomic LayerDeposition
I. Lee, M. A. Albiter, Q. Zhang, J. Ge, Y. Yin, F. Zaera, PCCP, 13(7), 2449-2456 (2011).I. Lee, J.-B Joo, Y. Yin, F. Zaera, Angew. Chem., Int. Ed., 50(43), 10208-10211 (2011).
AuTiO2
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
33
Catalyst Nano-ArchitecturesAu@Void@TiO2 Yolk-Shell Synthetic Strategy
Au
TiO2
Advantages:• Structural stability, prevents sintering.
• Selective percolation to and from inside.
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
34
50 nm 50 nm
50 nm 50 nm
Au@TiO2
Au/TiO2-P25
As Prepared Calcined, 775K
I. Lee, J. B. Joo, Y. Yin and F. Zaera, Angew. Chem., Int. Ed., 43, 10208-10211 (2011).
Catalyst Nano-ArchitecturesAu@Void@TiO2 Thermal Stability
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
TiO2
TiO2
Pt
TiO2
PtTiO2
CO-TiO2
CO-Pt
• CO, in gas phase or dissolved in a liquid, can reach the metal inside.
• Also works with larger molecules (Cd, Zn-TPP)
and other solvents (EtOH)
35
Catalyst Nano-ArchitecturesAu@Void@TiO2 Shell Porosity
I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Angew. Chem. Int. Ed., 50, 10208-10211 (2011).J. Liang, I. Lee, J.-B. Joo, A. Gutierrez, A. Tillekaratne, I. Lee, Y. Yin, F. Zaera, Angew. Chem. Int. Ed., 51, 8034-8036 (2012).J. Li, J. Liang, J.-B. Joo, I. Lee, Y. Yin, F. Zaera, J. Phys. Chem. C, 117, 20043–20053 (2013).
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Angew. Chem., Int. Ed., 50(43), 10208-10211 (2011).
36
Catalyst Nano-ArchitecturesAu@Void@TiO2 for CO Oxidation
CO oxidation at room temperature with Au@Void@TiO2 comparable to with Au/TiO2-P25.
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
New cryogenic T CO oxidation channel also with Au@Void@TiO2.
37
I. Lee, J. B. Joo, Y. Yin and F. Zaera, Angew. Chem., Int. Ed., 43, 10208-10211 (2011).I. Lee, J.-B. Joo, Y. Yin, F. Zaera, Surf. Sci., (2015).
Catalyst Nano-ArchitecturesAu@Void@TiO2 for CO Oxidation
CryoOxidation
RTOxidation
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Way to combine two or more functionalities in one single catalyst:• Bring together incompatible functionalities (i.e., acid + base)
• Can be used to convert short lived intermediates• Solve homogeneous catalyst solubility problems
38
Catalyst Nano-ArchitecturesTandem Catalysis
Francisco ZaeraDepartment of Chemistry
University of California, Riverside39
Catalyst Nano-ArchitecturesTandem Catalysis
Only acid + base produces
nitrostyrene (3).
Conclusions
Catalyst synthesiswith new
nanotechnology
HighlySelectiveCatalysts
Reaction mechanisms from
surface science
Catalytic site structure from
theory
40
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
F. Zaera, J. Phys. Chem. Lett., 1, 621-627 (2010).I. Lee, M. A. Albiter, Q. Zhang, J. Ge, Y. Yin, F. Zaera,
PCCP, 13(7), 2449-2456 (2011).F. Zaera, Catal. Lett., 142, 501-516 (2012).
F. Zaera, Chem. Soc. Rev., 42 2746-2762 (2013).F. Zaera, ChemSusChem, 6, 1797-1820 (2013).
Acknowledgements
Prof. Yadong Yin
41
Francisco ZaeraDepartment of Chemistry
University of California, Riverside
Ilkeun Lee
Juan SimonovisYujung Dong
A
B
Alejandro NegreteZhihuan Weng
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