Particle size effects in Rh/Al2O3 catalysts as viewed from a structural, functional, and reactive perspective: the case of the reactive adsorption of NO
- 183 Downloads
The structural-dynamic behaviour of γ-Al2O3 supported Rh nanoparticles under He, H2/He, and NO/He has been investigated using a newly developed methodology that permits dispersive EXAFS (EDE), diffuse reflectance infra red spectroscopy (DRIFTS), and mass spectrometry (MS) to be applied simultaneously to the study of gas-solid interactions. This reveals a considerably variability in nanoparticle habit (for 11 Å diameter nanoparticles as a function of temperature), and between 8 Å and 11 Å particles in their response to NO. The selectivity (N2/(N2 + N2O)) of the reactive interaction between NO and the supported Rh shows essentially no particle size dependence above 473 K: it is apparent, however, that considerable differences in some aspects of the structural behaviour of the 8 Å and 11 Å Rh particles do nonetheless, exist. At 373 < T < 473 K a clear divergence in structural, functional, and reactive response of the different sized supported Rh nanoparticles toward NO is observed. These observations are discussed in terms of the ability of different sized Rh particles to change structure in response to the reactive environment, the subsequent effect this has on the nitrosyl functionality that different phases may support, and the reactive pathways for NO conversion that may therefore arise.
KeywordsNitrosyl Dinitrosyl Size Dependent Effect Particle Size Dependence Oxidative Disruption
This work was funded by the EPSRC UK (Grant Number GR/60744/01) and the authors thank the EPSRC for the provision of post doctoral and PhD funding to MAN and BJ respectively. The ESRF are thanked for the provision of facilities within a long-term proposal awarded for this research. John James (University of Southampton), and Florian Perrin (ESRF) are gratefully acknowledged for their technical contributions to this work. Dr Gordon McDougall is also greatly thanked for the technical schematics of a novel DRIFTS cell designed and constructed at the department of chemistry, University of Edinburgh, Scotland. MAN would further like to thank the directors of the ESRF for funding for the continued development and implementation of this methodology at the ESRF for the wider use of the scientific community.
- 1.For example, Che M, Bennett CO (1989) Adv Catal 36:55Google Scholar
- 2.For example, Nieuwenhuys BE (2000) Adv Catal 44:259Google Scholar
- 12.Solymosi F, Bansagi T, Novak E (1988) J Catal 112:183Google Scholar
- 14.Newton MA, Jyoti B, Dent AJ, Fiddy SG, Evans J (2004) Chem Comm 2382Google Scholar
- 16.Newton MA, Fiddy SG, Guilera G, Jyoti B, Evans J (2005) Chem Comm 118Google Scholar
- 18.See, for example, (a) Harkness IR, Cavers M, Rees LVC, Davidson JM, McDougall GS (1999) In: Marcus BK, Treacy MMJ, Higgins JB, Bisher ME (eds) Proceedings of the 12th International Zeolite Conference, vol IV. Materials Research Society, Warrendale, PA, p 2615; (b) Cavers M, Davidson JM, Harkness IR, McDougall GS, Rees LVC (1999) In: Froment GF, Waugh KC (eds) Reaction Kinetics and the development of catalytic processes, vol 122. Elsevier, Amsterdam, p 65Google Scholar
- 19.Binsted N (1988) PAXAS: Programme for the analysis of X-ray adsorption spectra. University of SouthamptonGoogle Scholar
- 20.Binsted N (1998) EXCURV98, CCLRC Daresbury Laboratory computer programmeGoogle Scholar
- 24.Vant Blik HFJ, Banzon JBAD, Huiznga T, Vis JC, Koningsberger DC, Prins R (1983) J Phys Chem 87:13Google Scholar
- 30.For instance, Salanov AN, Savchenko VI (1994) Kinet Catal 35:722Google Scholar
- 36.Burch R, Lloader PK, Cruise N (1996) Appl Catal A 375Google Scholar