Development of ceria-supported sulfur tolerant nanocatalysts: Rh-based formulations

• Published in: Applied catalysis. A, General General, 2007-10, Vol.330, p.77-88
• Main Authors: Azad, Abdul-Majeed, Duran, Martin J.
• Format: Article
• Language: English
• Subjects: Catalysis; Chemistry; Coking phenomenon; Electron microscopy; Exact sciences and technology; General and physical chemistry; Logistic fuels; Metal oxides; Nanoscale doped-ceria supports; Noble metals; Steam reforming; Sulfur tolerance; Theory of reactions, general kinetics. Catalysis. Nomenclature, chemical documentation, computer chemistry
• ISSN: 0926-860X; 1873-3875
• DOI: 10.1016/j.apcata.2007.06.036

Performance of nominally doped nanoscale ceria-supported rhodium catalyst matrices in sulfur-laden fuel streams was evaluated. Catalysts with bimetal (Rh + Pd) dispersion were found to be very promising in terms of sulfur tolerance and percent H 2 yield. Addition of a metal oxide additive provides even higher stability and sulfur tolerance. ▪ The conversion of logistics fuels to hydrogen by steam reforming is attractive but poses great challenge since they contain sulfur up to about 3000 ppm leading to catalyst deactivation due to sulfur poisoning. In this paper, we report the fabrication of nominally doped nanoscale ceria-supported rhodium catalyst matrices for their performance evaluation in sulfur-laden fuel streams. Systematic structural and microstructural characterization of the catalysts was carried out before and after the steam reforming and simulated experiments in sulfur-containing streams (50 ppm < S < 1000 ppm) over a wide range of temperature and duration, to speculate and understand the deactivation mechanism and the sulfur tolerance aspects. Steam reforming of toluene as a model fuel without or with 50 ppm sulfur (as thiophene) was carried out at 825 °C and steam-to-carbon (S/C) ratio of 3. The performance of catalysts with bimetal (Rh + Pd) dispersion in small but equal concentrations was found to be the best both in terms of sulfur tolerance and percent H 2 yield. It was found that the addition of metal oxide additives yielded more stable and sulfur-tolerant formulation. Rhodium-alone and the rhodium + metal-oxide formulations outperformed their palladium-bearing analogs.