Characterization and catalytic performances of alkali-metal promoted Rh/SiO2 catalysts for propene hydroformylation

✍ Scribed by Laura Sordelli; Matteo Guidotti; Daniele Andreatta; Gilberto Vlaic; Rinaldo Psaro

• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 213 KB
• Volume: 204-205
• Category: Article
• ISSN: 1381-1169
• DOI: 10.1016/s1381-1169(03)00333-9

✦ Synopsis

The influence of the cationic promoters (M = Li, Na, K, Rb, Cs) on silica-supported rhodium catalysts was examined in the hydroformylation of propene at 413 K and atmospheric pressure. The catalysts were prepared by aqueous co-impregnation of RhCl 3 •3H 2 O and alkali-metal chloride. The rhodium to promoter molar ratio was 1. A pre-treatment cycle under O 2 /H 2 /O 2 at 673 K was carried out on the catalyst before the admission of the hydroformylation mixture. By in situ Rh K-edge extended X-ray adsorption fine-structure (EXAFS) characterization of the activated catalyst, two different Rh and alkali-metal oxide phases, highly dispersed and in intimate contact with each other, were detected on the support surface. Under catalytic conditions, small Rh metal particles are formed, with a mean diameter of 3.2 nm, as detected by HRTEM. The activity in aldehyde formation depends on the alkali-metal promoter in the following order: Li > Na > K > Rb Cs. This behavior parallels the trend of the polarizing power of the cation within the Group 1.