polymer-stabilized nickel nanoparticle catalysts · steric stabilization steric stabilization1:...
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Polymer-stabilized Nickel Nanoparticle Catalysts
Olivier NguonUniversity of WaterlooGauthier LaboratoryMay 1, 2009
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Outline
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Overview
Utilization of metallic nanoparticles as high performance catalysts
Performance maximized by preventing aggregation with polymeric stabilizers
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NanoparticlesNanoparticles (10-9 m) New properties New applications
Size effect: High surface-to-volume ratio
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Catalysis
5A. I. Frenkel, C. W. Hills, R. G. Nuzzo, J. Phys. Chem. B (2001) 105: 51.
Increased surface area Increased density of reactive sites (kinks, edges: low coordination sites )
Increased activity, selectivity
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van der Waals Interactions
Attractive interactions
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HAaV
12−
=
A: Effective Hamaker constant
a: Radius of the particles
H: Distance between particles
δ-δ+δ- δ+δ-δ+δ- δ+
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Steric Stabilization
Steric stabilization1:
Independent of electrolyte concentrationApplicable to polar and non-polar solventsReversible flocculation (non solvent/good solvent)
71. Napper (1983). “Polymeric Stabilization of Colloidal Dispersions”, p. 20. Academic Press, London.
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StabilizersSmall molecule surfactants: CTAB, SDS, etc.
Polymers: Homopolymers, telechelic polymers, block copolymers
Advantages of polymers:Increased colloidal stabilityProtection from oxidation“Polymeric field” (hydrophobic, electrostatic, acidic, etc.)
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Outline
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Nickel Nanoparticles
Supplied by Vale-Inco
Synthesized by gas condensation technique
Ni(CO)4 Ni + 4 CO
Control over size, composition (residual C,O)
10E. Kauffeldt, T. Kauffeldt, J. Nano. Res. (2006), 8: 477.
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Inco Nanoparticles – Size Distribution
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Average particle size: 60 nm
Broad size distributionIP
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Hydrogenation Reactions
Adiponitrile: Precursor in nylon-6,6 synthesis
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NCCN NH2NH2
H2
Adiponitrile 1,6-HexamethylenediamineNi
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Hydrogenation Reactions (cont’d)
Mesityl oxide: Precursor for methyl isobutyl ketone (solvent)
W.K. O’Keefe, M. Jiang, F.T.T. Ng, G.L. Rempel, Chemical Engineering Science (2005), 60: 4131. 13
Mesityl oxide MIBK MIBC
CH3CH3
CH3O
CH3CH3
CH3OH
CH3CH3
O CH3
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Hydrogenation Reactions (cont’d)
Nickel particles (under N2)Addition of substrate (mesityl oxide) and particles to solvent (2-propanol)Sonication
Reaction: 200 psig, 50°C, 330 rpmConversion monitoring
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Outline
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Polymeric StabilizersTelechelic polymers:
PEO-diethylenetriaminePEO-bis-2-picolylaminePEO-COOH
Diblock copolymers:PS-block-PMMAPS-block-P2VP
Triblock copolymers:PEO-block-PS-block-PEOP2VP-block-PS-block-P2VP
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n nm
N N
HC CH2 CH2 CH CH2 HCH H
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Synthesis: Triblock Copolymer
Electron-transfer Initiator:
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Synthesis: Triblock Copolymer (cont’d)PS addition:
P2VP addition:
18Termination: HCl/MeOH
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Outline
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Nanoparticles Activity: AdiponitrileNanoparticles more than 3X more active than Raney nickelImportant variations among nanonickel samples
0.44
0.11 0.09 0.090.05 0.03 0.02 0.02 0.02 0.01 0.01 0.00
0.0
0.1
0.2
0.3
0.4
0.5
Rate
of A
DN H
ydro
gena
tion
mol
/(L/g
Cat.h
)
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Nanoparticles Activity: Mesityl Oxide
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Increased activity
Solubilization of nickel oxide surface
Diethylenetriamine (DETA) treatment
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Inco 982174 – 97 m²/g
Activity variation for bare nanoparticles
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Inco 982174 (cont’d)
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Outline
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Conclusions
Different stabilizing polymers synthesized
Triblock copolymers work best
Protective effect from oxidation
Catalytic activity and colloidal stability of nanoparticles enhanced
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Applications
Mixed catalyst systems (Ni+Fe, Co)
Applications as efficient catalytic systems (fuel cells, specialty chemicals synthesis, etc.)
Tailoring of polymer structure and composition
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Acknowledgements
Supervisor: Prof. Mario Gauthier
Co-supervisor: Prof. Flora T.T. Ng
Vale - Inco: Vladimir PaserinSteve BaksaJun ShuNam Nguyen
Colleagues in the Gauthier and Duhamel Labs
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Thank You
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Any questionsIPR 20
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Size EffectSize decreases:
High surface-to-volume ratioQuantum effects
D.B. van Wyck, Anna CE Symposium, New Orleans, LA, 2004.29
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Size Dependence
M. Valden, X. Lai, D.W. Goddman, Science (1998), 281: 1647.
Increased activity with decreasing size
Maximum in activity can be observed
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London Interaction Energy
Hamaker constant for 60 nm particles: Ni = 22.10-20 JEthanol = 4.20 10-20 J
-4.0E-19
-3.5E-19
-3.0E-19
-2.5E-19
-2.0E-19
-1.5E-19
-1.0E-19
-5.0E-20
0.0E+000 20 40 60 80 100 120 140R (nm)
Va
(J) IP
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Rate Constant Determination
Kinetics:SamplingGC analysis
0.00.10.20.30.40.50.60.70.80.91.0
0 0.5 1 1.5 2 2.5 3
Time (hour)
[M]/[
M] 0 y = -2.4599x + 0.0898
R2 = 0.9843
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
0 0.2 0.4 0.6 0.8 1 1.2
Time (hour)
Ln ([
M]/[
M] 0)
Inco 982174 + 5% polymerIP
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Nanoparticles Activity: Adiponitrile (cont’d)
0.52
0.35
0.200.15 0.12 0.11 0.11 0.10 0.07 0.05 0.04 0.02
0.00.10.20.30.40.50.6
Quantu
mSphere
Inco 928
31Aldr
ich 827
36Inc
o 11237
6Inc
o 10877
5
Raney N
ickel
2800
Inco 113
132
Inco 959
11Inc
o 85109
Inco 730
11
Raney N
ickel
2400
Inco 928
31 (h
eptan
e)R
ate
of H
ydro
gena
tion
mol
/(L.m
².h)
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Rate of hydrogenation normalized per surface area
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Colloidal Stability in WaterInco 82325 (23 mg) in Water (10 mL) with Stabilizer
01020304050607080
0 5000 10000 15000 20000 25000 30000 35000
Time (s)
% T
rans
mitt
ance
Water Ref
PEO 2k (123 mg)
MPEG2k-DETA (65 mg)
PVP 10k (62 mg)
MPEG2k-DETA (125 mg)
PVP 1.3M (65 mg)
PEI 60k (60 mg)
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Polymer Bridging Effect
Interactions of stabilizing polymer with two different particles
Significant at low polymer concentration
May induce catalyst flocculation
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Inco 85109 in Methanol
Polymer/Particles(mg/mg)
0 10 1 0.1 0.003
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t = 0 min
t = 30 mint = 1 h
t = 2 h 30
t = 1 min
t = 2 h
t = 4 h
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372. Napper (1983). “Polymeric Stabilization of Colloidal Dispersions”, p. 16. Academic Press, London.
Polymer Effects
“Enormous complexity of the effects [of] polymer chains…”2
D.H. Napper
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Effect of Polymer Degree of Polymerization
H.Hirai. In “Tailored Metal Catalysts” (Ed. Y. Iwasawa). P.132, Reidel Publishing, Dordrecht (1986).
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