Abstract
In the present study we have used in situ EXAFS to provide experimental evidence for a reversible change in the morphology of the metallic particles in a high surface area, porous catalyst system, Cu/ZnO, containing small metallic copper particles. By changing the oxidation potential in the synthesis gas mixture, it is found that the apparent Cu-Cu coordination number changes in an essentially reversible manner suggesting that the small metallic Cu particles dynamically change morphology. This indicates that a wetting/non-wetting phenomenon takes place in the Cu/ZnO system with changing partial pressures of oxygen. Under similar conditions, these effects are not observed when copper is supported on, for example, SiO2. A model based on surface and interface free energies provides a simple explanation for the observed results. Since the wetting/non-wetting processes are accompanied by a change in the active surface area, the observed behavior has important general implications and such effects must be incorporated into microkinetic models in order to provide a proper description of the catalyst performance.
Similar content being viewed by others
References
K. Klier, Appl. Surf. Sci. 19 (1984) 267.
G.C. Chinchen, K.C. Waugh and D.A. Whan, Appl. Catal. 25 (1986) 101.
R. Burch, S.E. Golunski and M.S. Spencer, Catal. Lett. 5 (1990) 55.
K. Shimomura, K. Ogawa, M. Oba and Y. Kotera, J. Catal. 52 (1978) 191.
K. Tohji, Y. Udagawa, T. Mizushima and A. Ueno, J. Phys. Chem. 89 (1985)5671.
B.S. Clausen, B. Lengeler, B.S. Rasmussen, W. Niemann and H. Topsøe, J. Phys. (Paris) C 8 (1986)237.
T.L. Neils and J.M. Burlitch, J. Catal. 118 (1989) 79.
D. Duprez, Z. Fer-Hamida and M.M. Bettahar, J. Catal. 124 (1990) 1.
B.S. Clausen and H. Topsøe, Catal. Today 9 (1991) 189.
G.D. Moggridge, T. Rayment, R.M. Ormerod, M.A. Morris and R.M. Lambert, Nature 358 (1992)658.
B.S. Clausen, G. Steffensen, B. Fabius, J. Villadsen, R. Feidenhans'l and H. Topsøe, J. Catal. 132 (1991)524.
C.V. Ovesen, P. Stoltze, J.K. Nørskov and C.T. Campbell, J. Catal. 134 (1992) 445.
B.S. Clausen, B. Hammershøi, I. Chorkendorff, J.K. Nørskov, C.V. Ovesen, P.B. Rasmussen, P. Stoltze and P. Taylor, in preparation.
P.B. Rasmussen, P.M. Holmblad, T. Askgaard, C.V. Ovesen, P. Stoltze, J.K. Nørskov and I. Chorkendorff, submitted.
F. Jensen, F. Besenbacher and I. Stensgaard, Surf. Sci. 269 (1992) 400.
L. Ryan, I. Stensgaard, E. Lægsgård and F. Besenbacher, Surf. Sci. 296 (1993) 275.
T.F. Hayden and J.A. Dumesic, J. Catal. 103 (1987) 385.
T. F. Hayden, J.A. Dumesic, R.D. Sherwood and T.K. Baker, J. Catal. 105 (1987) 299.
J. Leyrer, M.I. Zaki and H. Knözinger, J. Phys. Chem. 90 (1986) 4775.
H. Knözinger, in:Proc. 9th Int. Congr. on Catalysis, Calgary 1988, eds. M.J. Phillips and M. Ternan (Chem. Inst. of Canada, Ottawa, 1988).
J. Leyrer, D. May and H. Knözinger, J. Catal. 124 (1991) 349.
B.S. Rasmussen, P.E. Højlund Nielsen, J. Villadsen and J.B. Hansen, in:Preparation of Catalysts, Vol. IV, eds. B. Delmon, P. Grange, P.A. Jacobs and G. Poncelet (Elsevier, Amsterdam, 1987) p. 785.
J.A. van Dillen, J.W. Geus, L.A.M. Hermans and J. van der Meijden, in:Proc. 6th Int. Congr. on Catalysis, eds. G.C. Bond, P.E. Wells and F.C. Tompkins (The Chemical Society, London, 1976) p. 677.
B.S. Clausen, L. Gråbæk, H. Topsøe, L.B. Hansen, P. Stoltze, J.K. Nørskov and O.H. Nielsen, J. Catal. 141 (1993) 368.
B.S. Clausen, H. Topsøe, L.B. Hansen, P. Stoltze and J.K. Nørskov, Japan J. Appl. Phys. 32 (1993) 95.
G. Wulff, Z. Krastallog, 34 (1901) 449.
I. Dybkjær, P.E. Højlund Nielsen and J.B. Hansen, paper presented at the 73rd Annual Meeting AIChe, New Orleans 1980.
M. Muhler, E. Törnqvist, L.P. Nielsen, B.S. Clausen and H. Topsøe, Catal. Lett. 25 (1994) 1.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Clausen, B.S., Schiøtz, J., Gråbæk, L. et al. Wetting/ non-wetting phenomena during catalysis: Evidence from in situ on-line EXAFS studies of Cu-based catalysts. Top Catal 1, 367–376 (1994). https://doi.org/10.1007/BF01492289
Issue Date:
DOI: https://doi.org/10.1007/BF01492289