New insights into the role of the electronic properties of oxide promoters in Rh-catalyzed selective synthesis of oxygenates from synthesis gas
Visualitza/Obre
New insights into the role of electronic properties...pdf (1,964Mb) (Accés restringit)
Sol·licita una còpia a l'autor
Què és aquest botó?
Aquest botó permet demanar una còpia d'un document restringit a l'autor. Es mostra quan:
- Disposem del correu electrònic de l'autor
- El document té una mida inferior a 20 Mb
- Es tracta d'un document d'accés restringit per decisió de l'autor o d'un document d'accés restringit per política de l'editorial
Cita com:
hdl:2117/13094
Tipus de documentArticle
Data publicació2011-06-13
Condicions d'accésAccés restringit per política de l'editorial
Tots els drets reservats. Aquesta obra està protegida pels drets de propietat intel·lectual i
industrial corresponents. Sense perjudici de les exempcions legals existents, queda prohibida la seva
reproducció, distribució, comunicació pública o transformació sense l'autorització del titular dels drets
Abstract
A series of 2.5% Rh/M@Al2O3 model catalysts were prepared by supporting Rh on high-area c-Al2O3, resulting in a surface covered by a monolayer (4.5–7 atoms/nm2) of MOx promoter oxides (M = Fe, V,Nb, Ta, Ti, Y, Pr, Nd,Sm). The catalysts were extensively characterized and evaluated for the conversion of synthesis gas to oxygenates at 553 K, 5.0 MPa, H2/CO = 1, and space velocity adjusted to attain CO conversion around 15%. The broad range of products formed depending on the specific promoter were, for the first time, quantitatively described using the selectivity parameter (Φ) defined here, which indicates, for a given reaction product, the contribution of carbon atoms derived from dissociative (Cdis)
and nondissociative (Cins) activation of CO. Both the catalytic activity and, more interestingly, the selectivity pattern given by the Φ parameter were correlated with the electronic properties of the MOx promoters (i.e., electron-donating/electron-withdrawing capacity) for an extensive series of catalysts. Low-temperature and at-work CO-FTIR experiments suggested that the high activity and hydrocarbon selectivity displayed by catalysts promoted by more electron-withdrawing (acidic) oxide promoters (e.g., TaOx) were related to a higher proportion of bridged Rh2(CO)B adsorption sites and to a higher electron
density (i.e., a higher electron back-donation ability) of the Rh0 surface sites, both factors promoting CO dissociation events. In contrast, linear CO adsorption on Rh0 sites displaying decreased electron backdonation in catalysts promoted by electron-donating (basic) oxides (e.g., PrOx, SmOx) was likely related to
nondissociative CO activation and thus to the selective formation of oxygenates. TEM, XPS, and CO-FTIR results pointed to differences in morphology, rather than size or partial electronic charge, of the nanosized Rh0 crystallites as the likely cause for the different proportions of CO adsorption sites. The Rh0 NP morphology, both as-reduced and at-work, is a function of the electronic properties of the underlying promoter oxide.
CitacióPrieto, G. [et al.]. New insights into the role of the electronic properties of oxide promoters in Rh-catalyzed selective synthesis of oxygenates from synthesis gas. "Journal of catalysis", 13 Juny 2011, vol. 280, núm. 2, p. 274-288.
ISSN0021-9517
Col·leccions
Fitxers | Descripció | Mida | Format | Visualitza |
---|---|---|---|---|
New insights in ... lectronic properties...pdf | 1,964Mb | Accés restringit |