IFLP   13074
INSTITUTO DE FISICA LA PLATA
Unidad Ejecutora - UE
artículos
Título:
Tuning the ring-opening reaction of 1,3-dimethylcyclohexane with the addition of potassium over Ir-containing catalysts
Autor/es:
SERGIO L. GONZÁLEZ-CORTÉS; SIRAPRAPHA DORKJAMPA; PHUONG T. DO; ZHONGRUI LI; JOSÉ M. RAMALLO-LÓPEZ; FÉLIX G. REQUEJO
Revista:
CHEMICAL ENGINEERING JOURNAL
Referencias:
Año: 2008 vol. 139 p. 147 - 156
ISSN:
1385-8947
Resumen:
The Ir/SiO2 and K ion-promoted Ir/SiO2
catalysts were fully characterized and catalytically studied using the
ring-opening reaction of 1,3-dimethylcyclohexane (1,3-DMCH) as a probe
reaction. This reaction could take place during the catalytic process
underwent either by gasoline or by diesel fuel for enhancing of octane
numbers or cetane numbers (CNs), respectively. The Ir catalysts were
characterized by chemisorption of CO and H2,
temperature-programmed techniques, X-ray photoelectron spectroscopy
(XPS), extended X-ray absorption fine structure spectroscopy (EXAFS)
and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy.
The addition of potassium ions to Ir/SiO2 catalyst produce
severe superficial changes that are reflected in its ability for
catalyzing the ring-opening reaction of 1,3-dimethylcyclohexane and the
selectivity to primary product from substituted to unsubstituted CC
cleavages. Ir dispersions slightly increased with rising K surface
density up to 3.1 atoms nm−2, but strongly decreased at higher K loadings due to the non-uniform decorative effect of potassium over Ir particles.
This contribution also reveals that the opening of CC
bonds at substituted or unsubstituted positions can be tuned varying
the promoter loading. That is, the dicarbene reaction path typically
occurs on Ir/SiO2 catalyst, facilitating the formation of branched products through the opening of CC
bonds at unsubstituted positions. On the other hand, the
metallocyclobutane intermediates become operative over K ion-promoted
Ir/SiO2 catalysts. This involves a metal atom and three C atoms to form cyclic intermediate specie that undergoes the opening of CC
bonds at substituted positions and facilitates the formation of
unbranched products, which are more desirable in the production of
diesel fuel.