Autori: J. Bódis

Editorial: J.E. Puskas, T.E. Long and R.F. Storey, Kluwer Academic/Plenum Publishers, In situ spctroscopy of monomer and polymer synthesis, book, p.187-205, 2003.

Rezumat:

Rhodium on different supports (active carbon, zeolite, SiO2, Al2O3, polymers, etc.) was found to be the most active and selective among supported transition metal catalysts for the vapor phase carbonylation of alcohols and hydrocarboxylation of alkenes to carboxylic acids. High catalyst activities and good selectivities were obtained for the carbonylation of methanol over carbon supported rhodium catalysts in tubular reactor. A detailed parameter study of the carbonylation reaction led to the experimental establishment of the kinetic equation. Fourier transform infrared (FT-IR) transmission spectroscopy was used to verify the validity of homogeneous methanol carbonylation mechanisms for two-phase (vapor-solid) applications. FT-IR spectra of adsorbed species obtained on RhCl3/Cab-O-Sil 5 catalyst treated successively with CO, CH3I and CH3OH gave valuable information on the reaction mechanism. The absorption band appearing at 1717-1723 cm-1 after CH3I adsorption on the catalyst surface is close to the acetyl C=O stretching frequency (1708-1711 and 1723 cm-1) obtained under homogeneous conditions, proving that the surface complex of type [Rh(CO)2AcIxLy]- (Ac = CH3CO-, L = OH-, H2O, SiO-, and x + y = 3) can be assumed as reaction intermediate, and the similarity of the mechanisms in both liquid and vapor-solid reaction conditions as well.

Cuvinte cheie: carbonylation of methanol, catalysts, heterogeneous catalysts, rhodium, FT-IR spectroscopy