Abstract
A series of activated carbon supported Ru catalysts have been reduced at different temperatures under hydrogen flow, and in some cases under ammonia flow, in order to modify the morphology and the particle size of the metallic active sites. CO chemisorption and transmission electron microscopy have been applied to follow the variations of these particles. The samples have been tested in the ammonia decomposition reaction, where systematic differences in catalytic activities as consequence of the support modification as well as due to the changes in the Ru particle sizes have been detected. Furthermore when potassium is added as catalyst promoter the sintering of Ru particles is significantly diminished and thus the changes in catalytic activities are inhibited. The electronic states of the Ru particles have been evaluated by determination of the chemisorption heats of the CO probe molecule. A part of other promoter or support effects it seems to exit a critical mean size for Ru particles on where maximum of catalytic activity is achieved. This behavior can be rationalized by the presence of surface highly active B5 sites, which consist of an arrangement of three Ru atoms in one layer and two further Ru atoms in an internal layer. These especial surface sites are expected to be in a higher proportion over Ru crystallites of those critical sizes, namely for Ru diameter sizes in the rage of 3–5 nm.
Similar content being viewed by others
References
Chellappa AS, Fisher CM, Thomson WJ (2002) Appl Catal A 227:231
Choudhary TV, Sivadinarayana C, Goodman DW (2001) Catal Lett 77:197
Hashimoto K, Toukai N (2000) J Mol Catal A 161:171
Raróg-Pilecka W, Szmigiel D, Komornicki A, Zielinski J, Kowalczyk Z (2003) Carbon 41:579
Yin SF, Xu BQ, Ng CF, Au CT (2004) Appl Catal B 48:237
Yin SF, Xu BQ, Zhou XP, Au CT (2004) Appl Catal A 277:1
Raróg-Pilecka W, Miskiewicz E, Szmigiel D, Kowalczyk Z (2005) J Catal 231:11
Bielawa H, Hinrichsen O, Birkner A, Muhler M (2001) Angew Chem Int Ed 40:1061
Jacobsen CJH, Dahl S, Hansen PL, Tornqvist E, Jensen L, Topsoe H, Prip DV, Moenshaug PB, Chorkendorff I (2000) J Mol Catal A 163:19
Strongin DR, Carrazza J, Bare SR, Somorjai GA (1987) J Catal 103:213
Bachiller-Baeza B, Rodríguez-Ramos I, Guerrero-Ruiz A (1998) Langmuir 14:3556
Bachiller-Baeza B, Guerrero-Ruiz A, Rodríguez-Ramos I (2000) Appl Catal A 192:289
Nevskaia DM, Castillejos-Lopez E, Guerrero-Ruiz A, Munoz V (2004) Carbon 42:653
Figueiredo JL, Pereira MFR, Freitas MMA, Orfao JJM (1999) Carbon 37:1379
Cerro-Alarcon M, Maroto-Valiente A, Rodríguez-Ramos I, Guerrero-Ruiz A (2005) Carbon 43:2711
Aika K, Ohya A, Ozaki A, Inoue Y, Yasumori I (1985) J Catal 92:305
Zheng W, Zhang J, Xu H, Li WZ (2007) Catal Lett 119:311
Acknowledgments
The financial support of the MEC of Spain under projects CTQ2005-09105-CO4-01 and CTQ2005-09105-CO4-03 is recognized. Also the help of the Complutense University Microscopy Services for the TEM determination is acknowledged.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
García-García, F.R., Guerrero-Ruiz, A. & Rodríguez-Ramos, I. Role of B5-Type Sites in Ru Catalysts used for the NH3 Decomposition Reaction. Top Catal 52, 758–764 (2009). https://doi.org/10.1007/s11244-009-9203-7
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11244-009-9203-7