Nanoscale perspective on the effect of acid washing carbon catalyst supports
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Transcript of Nanoscale perspective on the effect of acid washing carbon catalyst supports
Dennis Dowden Commemoration 3rd April 2013 1
Surface Science &
catalysis Cardiff Catalysis Institute
A nanoscale perspective on the effect of acid
washing of carbon catalyst supports
Emir Bouleghlimat, Philip R. Davies,Robert J. Davies, Jiri Kulahvy, David J. Morgan
Cardiff Catalysis Institute, School of Chemistry, Cardiff University
Dennis Dowden Commemoration 3rd April 2013 2
Surface Science &
catalysis Cardiff Catalysis Institute
Title Journal YearCatalysis and the electronic-structure of solids Abstracts of American chemical society 1985
Ammonia-synthesis and related reactions over iron-cobalt and iron-
nickel alloy catalysts .1. Catalysts reduced at 853-KApplied catalysis 1982
Hydrogen spillover on alumina-supported Pt-Re catalysts JCS Chem Comm 1977
Design of heterogeneous catalysts Chimica & lndustria 1973
Crystal and ligand field models of solid catalysts Catalysis reviews 1971
Principles for selection of catalyst carriers Chemie ingenieur technik 1968
Surface valencies chemisorption and catalysisAnales de la real sociedad espanola de
fisica y quimica seria b-quimica1965
New ideas in catalysis Chemistry & industry 1962
The selective hydrogenation of acetylene Transactions of the Faraday society 1958
The significance of patterns of activity in chemisorption and catalysis Angewandte chemie 1958
Hydrogen-deuterium exchange on the oxides of transition metals Advances in catalysis 1957
The testing of heterogeneous catalysts Advances in catalysis 1957
Heterogeneous catalysis .1. Theoretical basis Chemistry & industry 1949
The heat of adsorption of gases on chromium sesquioxide at low
pressures and room temperaturesJ. Chem. Soc 1939
Heats of adsorption of gases on chromic oxide at low temperatures JACS 1938
Selection of papers by Dowden
Dennis Dowden Commemoration 3rd April 2013 3
Surface Science &
catalysis Cardiff Catalysis Institute
Carbon as a Catalyst Support for Gold
Hydrochlorination of ethyne
C2H2 + HCl C2H3ClAu/C
Vinyl chloride PVC
“Aqua Regia Activated Au/C Catalysts for the Hydrochlorination of Acetylene.”
Marco Conte, Peter Johnston, Graham J. Hutchings et al.
Journal of Catalysis 297 (2013) 128
“Aqua regia …… prepare the most efficient catalysts for the hydrochorination of acetylene by impregnation of HAuCl4 on carbon …….. due to a combination of the oxidising effect of HNO3
on the carbon support and gold, as well as a nucleation effect of HCl …. the two acids ….. act synergistically.”
Dennis Dowden Commemoration 3rd April 2013 4
Surface Science &
catalysis Cardiff Catalysis Institute
Preparation of Carbon Supported Metals
1. Washing:• HCl, HNO3, Aqua Regia (HCl & HNO3)
2. Impregnation• HAuCl4, H2PdCl4 and H2PtCl4• H2O, HCl, HNO3, Aqua Regia
3. Drying• 290 oC - 200 oC
4. Regeneration• H2O, HCl, HNO3, Aqua Regia
Dennis Dowden Commemoration 3rd April 2013 5
Surface Science &
catalysis Cardiff Catalysis Institute
Direct synthesis of H2O2
“Switching Off Hydrogen Peroxide Hydrogenation in the Direct Synthesis Process.”
Edwards, Hutchings et al. Science 323 (2009) 1037
Table 2. Activity and selectivity of pretreated and untreated carbon-supported catalysts
Fig. 2. STEM-XEDS particle size distributions acid-pretreated and non treated catalysts.
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Surface Science &
catalysis Cardiff Catalysis Institute
Carbon supports
Dennis Dowden Commemoration 3rd April 2013 7
Surface Science &
catalysis Cardiff Catalysis Institute
Nanoscale investigation:
can we connect UHV and catalysis?
Catalyst• Carbon powder• Preparation in air• Deposition from solution
HOPG
Surface Science• Graphite crystal• UHV• Vapour deposition• Surface science tools
HOPG
“Bench top” surface science• Graphite crystal• Preparation in air• Deposition from solution• Surface science tools
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Surface Science &
catalysis Cardiff Catalysis Institute
Experimental methods:
Sample preparation:1. Graphite peeled with sticky tape2. Solutions added by dropper – 1 drop ~ 0.2ml3. Allowed to stand in air 30 seconds4. Dried in clean helium stream
Spectroscopic & Microscopic methods
Atomic ForceMicroscopy
X-ray photoelectronspectroscopy
Scanning TunnellingMicroscopy
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Surface Science &
catalysis Cardiff Catalysis Institute
Clean HOPG surface
Deionised water
Control experiments
Ultra pure water
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Surface Science &
catalysis Cardiff Catalysis Institute
The effect of acid treatment on HOPG
Clean HOPG surface
0.2 M HCl, 30 min
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Surface Science &
catalysis Cardiff Catalysis Institute
Low concentration HCl
0.2 M HCl, 30 min
0.1 M HCl, 30 min
Surface coverage of features ~ 20% surface area
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Surface Science &
catalysis Cardiff Catalysis Institute
Comparison of HCl and HNO3:
Effect of acid concentration
0.1 M HCl, 30 min
0.1 M HNO3, 30 min
Dennis Dowden Commemoration 3rd April 2013 13
Surface Science &
catalysis Cardiff Catalysis Institute
Comparison of HCl and HNO3:
Effect of acid concentration II
0.5 M HCl
10 M HCl10 M
0.5 Mx10
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Surface Science &
catalysis Cardiff Catalysis Institute
Models to account for the features
Dennis Dowden Commemoration 3rd April 2013 15
Surface Science &
catalysis Cardiff Catalysis Institute
XPS
HNO3
HCl
Clean
HNO3
HCl
Clean
Dennis Dowden Commemoration 3rd April 2013 16
Surface Science &
catalysis Cardiff Catalysis Institute
HNO3
HCl
HNO3
HCl
XPS
• No Ca, K, Na• Maximum O(a) ~ 4% monolayer
Dennis Dowden Commemoration 3rd April 2013 17
Surface Science &
catalysis Cardiff Catalysis Institute
Models to account for the features
Dennis Dowden Commemoration 3rd April 2013 18
Surface Science &
catalysis Cardiff Catalysis Institute
STMClean graphite 0.1 M HCl treated
0.1 M HCl treated 0.1 M HCl treated Conclusion
• The graphite lattice extends over the features
• “Bubbles” not deposits
Dennis Dowden Commemoration 3rd April 2013 19
Surface Science &
catalysis Cardiff Catalysis Institute
Local delamination
HCl
Dennis Dowden Commemoration 3rd April 2013 20
Surface Science &
catalysis Cardiff Catalysis Institute
Gold deposition on acid treated surfaces6.2 x10-5 M HAuCl4
Sample preparation:1. Clean graphite treated with 0.5 M HCl2. 6x10-5 M HAuCl4 solution, 1 drop ~ 0.2ml3. Stand 1 minute, blown dry in clean helium stream
Gold “doughnuts”!
Dennis Dowden Commemoration 3rd April 2013 21
Surface Science &
catalysis Cardiff Catalysis Institute
Gold nucleation on acid treated surfaces0.5M HCl, 6.2 x10-6 M HAuCl4
0.5M HCl HAuCl4
Au nucleation on acid induced defects HCl
Au
Dennis Dowden Commemoration 3rd April 2013 22
Surface Science &
catalysis Cardiff Catalysis Institute
XPS of Gold on Acid Treated Carbons
• Auo dominates
• % Auo/Au+/Au3+ similar
• Au nucleation greater on HCl treated surface
Dennis Dowden Commemoration 3rd April 2013 23
Surface Science &
catalysis Cardiff Catalysis Institute
Gold deposition on acid treated surfaces6.2 x10-6 M HAuCl4
HNO3
HCl
HNO3
HCl
HNO3
HNO3
HCl
HCl
Dennis Dowden Commemoration 3rd April 2013 24
Surface Science &
catalysis Cardiff Catalysis Institute
Au deposition ona HCl treated
surface
Dennis Dowden Commemoration 3rd April 2013 25
Surface Science &
catalysis Cardiff Catalysis Institute
Gold deposition on acid treated surfaces6.2 x10-6 M HAuCl4
HNO3
HCl
HNO3
HCl
HNO3
HNO3
HCl
HCl
Dennis Dowden Commemoration 3rd April 2013 26
Surface Science &
catalysis Cardiff Catalysis Institute
Au deposition with an acid
HCl dosed with AuHNO3 dosed with Au
Sample preparation:1. Clean graphite2. 6x10-6 M HAuCl4 solution in 0.5 M HCl or HNO3, 1 drop ~ 0.2ml3. Stand 1 minute, blown dry in clean helium stream
HNO3
HCl
Dennis Dowden Commemoration 3rd April 2013 27
Surface Science &
catalysis Cardiff Catalysis Institute
Conclusions
• Mild acid treatment of graphite results in local delamination
• Au nucleation occurs at defect sites
• Pretreatment with acid HCl enhances Au nucleation & deposition HNO3 generates larger gold nanoparticles
• Au depositon in acid HCl enhances nucleation of smaller particles HNO3 generates larger particles
Dennis Dowden Commemoration 3rd April 2013 28
Surface Science &
catalysis Cardiff Catalysis Institute
Next steps: Aqua Regia
Fig. 3 Conversion () after 5 h and Au3+ () for Au/C catalysts containing different amounts of Au3+. The catalysts were obtained from impregnation using solutions containing different HNO3 volume fraction in the HCl/HNO3 mixture.
“Modifications of the Metal and Support During the Deactivation and Regeneration of Au/C Catalysts for the Hydrochlorination of Acetylene.” Marco Conte, Catherine J. Davies, Graham J. Hutchings et al.Catalysis Science & Technology 3, (2012) 128
Dennis Dowden Commemoration 3rd April 2013 29
Surface Science &
catalysis Cardiff Catalysis Institute
Funded by EP/I038748/1Cardiff University CUROP awards