Temperature-Programmed Reduction and CO Hydrogenation of La2O3-Promoted Rh/SiO2 Catalysts

✍ Scribed by A.L. Borer; R. Prins

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 765 KB
• Volume: 144
• Category: Article
• ISSN: 0021-9517
• DOI: 10.1006/jcat.1993.1344

✦ Synopsis

(\mathrm{Rh} / \mathrm{SiO}{2^{-}}, \mathrm{Rh} / \mathrm{La}{2} \mathrm{O}{3^{-}}), and (\mathrm{La}{2} \mathrm{O}{3})-promoted (\mathrm{Rh} / \mathrm{SiO}{2}) catalysts were investigated by temperatureprogrammed reduction (TPR) and (\mathrm{CO}) hydrogenation. When the (\mathrm{La}{2} \mathrm{O}{3}-\mathrm{Rh} / \mathrm{SiO}{2}) catalysts were prepared by sequential impregnation with La impregnation as the final step, the Rh particles were partly covered by (\mathrm{La}{2} \mathrm{O}{3}). When the impregnation sequence was reversed, and also when coimpregnation was applied, well dispersed Rh particles were formed, which showed a distinct interaction with the promoter but no covering. The presence of (\mathrm{La}{2} \mathrm{O}{3}) shifted the TPR reduction of (\mathrm{Rh}{2} \mathrm{O}{3}) to higher temperatures and enhanced the oxygenate selectivity in the (\mathrm{CO}) hydrogenation. Catalysts exposed to air showed different TPR results and higher (\mathbf{H}{2}) consumptions than in sith calcined catalysts due to the presence of La carbonate. After removal of carbonate, no (\mathrm{H}{2}) consumption other than for the reduction of (\mathrm{Rh}^{3+}) to (\mathrm{Rh}^{0}) was observed, demonstrating that no reduction of (\mathrm{La}{2} \mathrm{O}_{3}) takes place. 1993 Academic Press, Inc.