The role of the support in CO hydrogenation selectivity of supported rhodium

Manganese-promoted Rh/Al2O3 for C2-oxygenates synthesis from syngas

“…The nature of sites where the CO insertion process occurs is not completely clear. In this sense, Watson and Somorjai [44,45] proposed that CO insertion takes place on Rh + sites, whereas Katzer et al [46] failed to find a correlation between oxygenate yield and the number of Rh + sites. Recently, Wang et al [16] have proposed the following structure as the active sites for the formation of C 2 -oxygenates: (Rh 0…”

Mechanism of C2+ oxygenate synthesis on Rh catalysts

“…The most dramatic effect of support on the product selectivity has been observed with ethanol synthesis over Rh catalysts. The selectivity for ethanol decreased in the order: Rh/La 2 O 3 >Rh/TiO 2 >Rh/ SiO 2 >Rh/Al 2 O 3 [46]. The variation of alcohol selectivity has been attributed to the electron withdrawing/ donating capability of an acidic/basic support, morphology of the metal, and effect of support on the reducibility of the metal.…”

Different Mechanisms for the Formation of Acetaldehyde and Ethanol on the Rh–Based Catalysts

“…On the other hand, there are disagreements on the active sites for the CO insertion process. Watson and Somorjai (18,19) proposed that CO insertion to form C 2+ -oxygenates occurs on the Rh + sites, whereas Katzer et al (20) reported from an XPS study that there was no correlation between the yields of C 2 -oxygenates and the number of Rh + sites on the catalyst. In recent years, most of the reports agreed that single Rh atom sites are active for CO insertion, whether it is the Rh 0 or the Rh + entity (21)(22)(23).…”