ACS Catalysis
Research Article
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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We acknowledge the support of the Engineering and Physical
Sciences Research Council (EP/E006345/1) of the U.K.
REFERENCES
■
(1) Adebowale, K. O.; Adewuyi, A.; Ajulo, K. D. Int. J. Green Energy
2012, 9, 297−307.
(2) Demirbas, A. Prog. Energy Combust. Sci. 2005, 31, 466−487.
(3) Tong, D.; Hu, C.; Jiang, K.; Li, Y. J. Am. Oil Chem. Soc. 2011, 88,
415−423.
(4) Moser, B. R. Energy Fuels 2008, 22, 4301−4306.
(5) Reutmann, W.; Keiczka, M. Ullmann’s Encyclopedia of Industrial
Chemistry, 5th Ed.; Wiley-VCH: New York, 1989; Vol. A12, p 13.
(6) Liu, H.; Iglesia, E. J. Phys. Chem. B 2005, 109, 2155−2163.
(7) Huang, H.; Li, W.; Liu, H. Catal. Today 2012, 183, 58−64.
(8) Lichtenberger, J.; Doohwan, L.; Iglesia, E. Phys. Chem. Chem.
Phys. 2007, 9, 4902−4906.
Figure 9. DRIFT spectra of a used (in situ activated) 1 wt % Au−Pd/
TiO2 (water-refluxed) catalyst treated under a N2 flow (with H2O
present) as a function of time, to replicate leaving the catalyst in a
reactor overnight under flowing He in the presence of H2O.
retention/increased presence of formate ions on the surface
that are available to react with methanol when normal reaction
conditions are resumed explains the renewed high methanol
conversion and methyl formate selectivity of the in situ
activated catalyst.
This finding can also be used to explain the opposite trend in
low activity of the in situ activated catalyst removed from the
reactor (left in air overnight) prior to reuse. To replicate these
conditions, the in situ activated catalyst was placed in static air
for 16 h. This study revealed a noticeably lower intensity of
bands associated with formate, with only weak bands at 1360
and 1059 cm−1 still being present (SI Figure S4). Therefore, an
absence of these adsorbed surface intermediate species
essentially relates to a “fresh” catalyst again, leading to low
reactivity.
(9) Cubeiro, M. L.; Fierro, J. L. G. Appl. Catal., A 1998, 168, 307−
322.
(10) Wojcieszak, R.; Gaigneaux, E. M.; Ruiz, P. ChemCatChem 2012,
4, 72−75.
(11) Enache, D. I.; Edwards, J. K.; Landon, P.; S-Espriu, B.; Carley, A.
F.; Herzing, A. A.; Watanabe, M.; Kiely, C. J.; Knight, D. W.;
Hutchings, G. J. Science 2006, 311, 362−365.
(12) Tsunoyama, H.; Sakurai, Hi.; Negishi, Y.; Tsukuda, T. J. Am.
Chem. Soc. 2005, 127, 9374−9375.
(13) Abad, A.; Almela, C.; Corma, A.; Garcia, H. Tetrahedron 2006,
62, 6666−6672.
(14) Buonerba, A.; Cuomo, C.; Sanchez, S. O.; Canton, P.; Grassi, A.
Chem.Eur. J. 2012, 18, 709−715.
(15) Abad, A.; Conception, P.; Corma, A.; Garcia, H. Angew. Chem.,
Int. Ed. 2005, 44, 4066−4069.
(16) Kosuda, K. M.; Wittstock, A.; Friend, C. M.; Baumer, M. Angew.
̈
Chem., Int. Ed. 2012, 51, 1698−1701.
3. CONCLUSIONS
(17) Marx, S.; Baiker, A. J. Phys. Chem. C 2009, 113, 6191−6201.
(18) Wittstock, A.; Zielasek, V.; Biener, J.; Friend, C. M.; Baumer, M.
Supported bimetallic Au−Pd catalysts were demonstrated to
achieve high activity at low reaction temperatures for the
oxidation of methanol to methyl formate. The use of sol-
immobilized 1 wt % Au−Pd/TiO2 catalysts prepared using
different water extraction and calcination treatments to remove
PVA ligands was investigated, with several characterization
techniques displaying a strong interplay between metal
nanoparticle size, residual PVA ligand content, and catalytic
activity. The bimetallic Au−Pd/TiO2 catalyst washed with hot
water demonstrated higher activity at low reaction temperatures
than the corresponding calcined and nontreated catalysts.
Remarkably, we observed that a subsequent in situ activation
step leads to a significant enhancement in catalytic activity at
low temperatures. Using in situ DRIFTS, we ascribed this effect
to the increased quantity of adsorbates, particularly formate
species, present on the catalyst surface.
̈
Science 2010, 327, 319−322.
(19) Liu, X. Y.; Madix, R. J.; Friend, C. M. Chem. Soc. Rev. 2008, 37,
2243−2261.
(20) Kegnæs, S.; Mielby, J.; Mentzel, U. V.; Christensen, C. H.;
Riisager, A. Green Chem. 2010, 12, 1437−1441.
(21) Oliveira, R. L.; Kiyohara, R. K.; Rossi, L. M. Green Chem. 2009,
11, 1366−1370.
(22) Hvolbæk, B.; Janssens, T. V. W.; Clausen, B. S.; Falsig, H.;
Christensen, C. H.; Nørskov, J. K. Nano Today 2007, 2, 14−18.
(23) Zhou, Y.; Wang, C. Y.; Zhu, Y. R.; Chen, Z. Y. Chem. Mater.
1999, 11, 2310−2312.
(24) Kesavan, L.; Tiruvalam, R.; Rahim, M. H. A.; Saiman, M. I. B.;
Enache, D. I.; Jenkins, R. L.; Dimitratos, N.; Lopez-Sanchez, J. A.;
Taylor, S. H.; Knight, D. W.; Kiely, C. J.; Hutchings, G. J. Science 2011,
331, 195−199.
́
(25) P-Santos, I.; L-Marzan, L. M. Langmuir 2002, 18, 2888−2894.
(26) Jaramillo, T. F.; Baeck, S.-H.; Cuenya, B. R.; McFarland, E. W. J.
Am. Chem. Soc. 2003, 125, 7148−7149.
ASSOCIATED CONTENT
* Supporting Information
The following file is available free of charge on the ACS
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(27) Lopez-Sanchez, J. A.; Dimitratos, N.; Hammond, C.; Brett, G.
L.; Kesavan, L.; White, S.; Miedziak, P.; Tiruvalam, R.; Jenkins, R. L.;
Carley, A. F.; Knight, D.; Kiely, C. J.; Hutchings, G. J. Nat. Chem.
2011, 3, 551−556.
S
(28) Grunwaldt, J. D.; Kiener, C.; Wogerbauer, C.; Baiker, A. J. Catal.
̈
Materials and Methods, accompanied by figures support-
1999, 181, 223−232.
(29) Comotti, M.; Li, W.-C.; Spliethoff, B.; Schuth, F. J. Am. Chem.
Soc. 2006, 128, 917−924.
AUTHOR INFORMATION
Corresponding Author
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(30) Wang, R.; Wu, Z.; Chen, C.; Qin, Z.; Zhu, H.; Wang, G.; Wang,
H.; Wu, C.; Dong, W.; Fan, W.; Wang, J. Chem. Commun. 2013, 49,
8250−8252.
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ACS Catal. 2015, 5, 637−644