Metal-support interactions during the CO2 reforming of CH4 over model TiOx/Pt catalysts
To obtain insight into the importance of metal-support interactions (MSI) in the CO2 reforming of CH4, the reaction was studied using pure TiO2, high-purity Pt powder, and two model TiOx/Pt systems. The latter two TiOx/Pt catalysts, prepared by oxidation of Ti nonylate deposited on the Pt powder surface, contained either one (θ=1) or ten (θ=10) theoretical monolayers of TiO2. The H2 and CO chemisorption capacities showed respective decreases of 1/3 and 1/2 on the latter two catalysts although the N2 BET surface areas were essentially unchanged. XRD analysis of either TiOx/Pt sample detected no TiOx structures. Specific rates (μ mol/(s gcat)), areal rates (μ mol/(s m2)) and turnover frequencies (s-1) for the CO2 reforming of CH4 decreased in the order TiOx/Pt (θ=10)TiOx/Pt( θ=1)>>Pt powder>TiO2. Neither pure Pt powder nor pure TiO2 showed appreciable activity for CH4-CO2 reforming; thus the dramatic increase in activity is attributed to the creation of new sites in the metal-support interfacial region which promote CH4 dissociation, CO2 dissociation and reduction, and subsequent CHxO decomposition. In addition, temperature-programmed hydrogenation of used catalyst samples clearly showed that TiOx overlayers on the Pt surface suppress carbon deposition during reaction via an ensemble effect, thus improving activity maintenance.
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- M.C.J. Bradford and M.A. Vannice, J. Catal. (1997), in press.Google Scholar
- (a)M.A.Vannice and D. Poondi, J. Catal., submitted. (b) D. Poondi, PhD Dissertation, The Pennsylvania State University, USA (1996).Google Scholar
- B.D. Cullity, Elements of X-ray Diffraction, 2nd Ed. (Addison-Wesley, Reading, 1978).Google Scholar
- J.W. Edington, Practical Electron Microscopy in Materials Science (N.V. Philips Gloeilampenfabrieken, Eindoven, 1976).Google Scholar
- [ 19]
- A. Rodes, E. Pastor and T. Iwasita, Anal. Quim. 89 (1993) 458.Google Scholar
- C.R. Prichard and C.N. Hinshelwood, J. Chem. Soc. 127 (1925) 806.Google Scholar
- T.P. Beebe Jr., D.W. Goodman, B.D. Kay and J.T. Yates Jr., J. Chem. Phys. 87 (1987) 2305.Google Scholar
- M. Sigl, M.C.J. Bradford, H. Knözinger and M.A. Vannice, Topics Catal., submitted.Google Scholar
- D.J. Dwyer, J.L. Robbins, S.D. Cameron, N. Dudash and J. Hardenbergh in: Strong Metal Support Interactions, ACS Symposium Series 298 (Am. Chem. Soc., Washington, 1986) p. 21.Google Scholar
- A.A. Davydov, M.P. Komarova, V.F. Anufrienko and N.G. Maksimov, Kinet. Catal. 14 (1973) 1342.Google Scholar