Abstract
Measurements of the heat of adsorption of hydrogen on Ir/Al2O3 catalysts of different metal particle size were made by employing adsorption microcalorimetry. The values of this quantity were different for each sample and the results also indicated the heterogeneity of the iridium surface. In contrast to this, the heat of adsorption of oxygen measured on the same samples in the same manner was practically the same for all of them. The heat of oxygen adsorption as presented in the differential calorimetric isotherms was constant up to half the monolayer coverage for all the samples. This result is unexpected and in contradiction to the presence of surface heterogeneity in the iridium crystallites, as revealed by hydrogen adsorption. To clarify these anomalies the energetics of oxygen adsorption was determined using a different method. Titration experiments with hydrogen of preadsorbed oxygen were carried out. The heat of adsorption of oxygen was calculated from these results by means of adopting a thermochemical cycle. The values of heat of adsorption obtained as a function of the amount adsorbed unveiled the heterogeneity of the iridium surface. The differences found between the samples can be correlated to both the different particle size and degree of sintering of the samples.
Similar content being viewed by others
References
K. Foger and J.R. Anderson, J. Catal. 59 (1979) 325.
S. Taniguchi, T. Mori, Y. Mori, T. Hattori and Y. Murakami, J. Catal. 116 (1989) 108.
M.F. Mark and W.F. Maier, J. Catal. 164 (1996) 122.
C.G. Walter, B. Coq, F. Figueras and M. Boulet, Appl. Catal. A Gen. 133 (1995) 95.
A. Erdohelyi, K. Fodor and G. Suru, Appl. Catal. A Gen. 139 (1996) 131.
O. Alexeev and B.C. Gates, J. Catal. 176 (1998) 310.
P. Reyes, J. Fernandez, G. Pechi and J.L.G. Fierro, J. Chem. Techn. Biotechnol. 73 (1998) 1.
J.C. Rasser, W.H. Beindorf and J.J.F. Scholten, J. Catal. 59 (1979) 211.
M.J. Dees and V. Ponec, J. Catal. 115 (1989) 347.
M. Ogura and E. Kikuchi, Chem. Lett. (1996) 1017.
L.I. Ali, A.-G. Ali, S.M. Aboul-Fotouh and A.K. Aboul-Gheit, Appl. Catal. A 177 (1999) 99.
Y.J. Huang, S.C. Fung, W.E. Gates and G.B. McVicker, J. Catal. 118 (1989) 192.
D. Kelly and W.H. Weinberg, J. Chem. Phys. 105 (1996) 271, 7171, 11313.
D.C. Seets, M.C. Wheeler and C.B. Mullins, Chem. Phys. Lett. 266 (1997) 431.
A. Charron, Ch. Kappenstein, S. Balcon, S. Rossignol and E. Gengembre, Appl. Catal. A 182 (1999) 317.
M. Cabrejas Manchado, J.M. Guil and A. Ruiz Paniego, J. Chem. Soc., Faraday. Trans. 185 (1989) 1775.
M. Cabrejas Manchado, J.M. Guil and A. Ruiz Paniego, J. Catal. 136 (1992) 598.
J.M. Guil, A. Pérez Masiá, A. Ruiz Paniego and J.M. Trejo Menayo, Thermochimica Acta, 312 (1998) 115.
B. Sen and M.A. Vannice, J. Catal. 129 (1991) 31.
J.M. Guil, A.P. Masiá, A.R. Paniego and J.M.T. Menayo, Stud. Surf. Sci. Catal. 75 (1993) 1859.
D.H. Everett, Pure Appl. Chem. 31 (1972) 579.
J.M. Guil, A. Pérez Masiá, A. Ruiz Paniego and J.M. Trejo Menayo, J. Chem. Thermodynamics 26 (1994) 5.
M. Cabrejas Manchado, J.M. Guil, A. Pérez Masiá, A. Ruiz Paniego and J.M. Trejo Menayo, Langmuir 10 (1994) 685.
B.J. Kip, F.B.M. Duivenvoorden, D.C. Koningsberger and R. Prins, J. Catal. 105 (1987) 26.
J.M. Rojo, J.P. Belzunegui, J. Sanz and J.M. Guil, J. Phys. Chem. 98 (1994) 13631.
TRC Thermodynamic Tables, Texas Engineering Experimental Station (1991).
G. Della Gatta, B. Fubini and G. Venturello, J. Chim. Phys. 70 (1973) 64.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Guil, J.M., Herrero García, J.E., Ruiz Paniego, A. et al. Gas/Surface Titration Microcalorimetry. Energetics of Oxygen Adsorption on Supported Iridium Catalysts. Topics in Catalysis 19, 313–321 (2002). https://doi.org/10.1023/A:1015340929427
Issue Date:
DOI: https://doi.org/10.1023/A:1015340929427