Use of methanol as an IR molecular probe to study the surface chlorination of ceria

Abstract

Ceria has been chlorinated either by CCl₄ treatment at 473 K or by impregnation with an aqueous HCl solution and the surface studied by IR spectroscopy using methanol as a probe. It was shown that methanol was molecularly adsorbed on the CCl₄-treated ceria, being H bonded to Cl^- surface species and O bonded to reduced Ce³⁺ surface cations. This assumes the reductive surface substitution of O^2- species by Cl^- ions during the CCl₄ treatment with the formation of CeOCl species (Ce^III). With the HCl-impregnated ceria sample, methanol was either molecularly adsorbed or dissociated into methoxy species, indicating a mainly unreduced (Ce^IV) surface that is homogeneously chlorinated by HCl-chemisorption. The importance of CeOCl surface species was further evidenced when methanol was adsorbed on a reduced Pd/CeO₂ catalyst prepared from the PdCl₂ precursor.

References

1. F. Le Normand, L. Hilaire, K. Kili, G. Krill and G. Maire, J. Phys. Chem., 1988, 92, 2561.
2. F. Le Normand, J. Barrault, R. Breaut, L. Hilaire and A. Kiennemann, J. Phys. Chem., 1991, 95, 257.
3. S. Bernal, J. Calvino, G. Cifredo, J. Gatica, J. Pérez Omil, A. Laachir and V. Perrichon, Stud. Surf. Sci. Catal., 1995, 96, 419.
4. C. Contescu, D. Macovei, C. Craiu, C. Teodorescu and J. Schwarz, Langmuir, 1995, 11, 2031.
5. G. Munuera, A. R. Gonzalez-Elipe, J. P. Espinos, A. Muñoz, J. C. Conesa, J. Soria and J. Sanz, Catal. Today, 1988, 2, 663.
6. W. Wolcyrz and L. Kepinski, J. Solid State Chem., 1992, 99, 409.
7. L. Kepinski, M. Wolcyrz and J. Okal, J. Chem. Soc., Faraday Trans., 1995, 91, 507.
8. A. Badri, C. Binet and J. C. Lavalley, J. Chem. Soc., Faraday Trans., 1997, 93, 1159.
9. C. Binet, A. Jadi, J. C. Lavalley and M. Boutonnet-Kizling, J. Chem. Soc., Faraday Trans., 1992, 88, 2079.
10. A. Badri, C. Binet and J. C. Lavalley, J. Phys. Chem., 1996, 100, 8363.
11. A. Serralach, R. Meyer and H. Gunthard, J. Mol. Spectrosc., 1972, 52, 91.
12. C. Binet, A. Jadi and J. C. Lavalley, J. Chim. Phys. Phys.-Chim. Biol., 1992, 89, 1441.
13. A. Badri, Thesis, University of Caen, France, 1994.
14. N. Bakkas, Y. Bouteiller, A. Loutellier, J. P. Perchard and S. Racine, J. Chem. Phys., 1993, 99, 3335.
15. J. P. Gallas and C. Binet, Adv. Mol. Relax. Interact. Proc., 1982, 24, 191.
16. C. Binet, A. Jadi and J. C. Lavalley, J. Chim. Phys. Phys.-Chim. Biol., 1992, 89, 31.