Fourier-transform infrared study of Rh/SiO2 catalysts exposed to CO–H2 mixtures at high pressure and temperature

Abstract

FTIR spectra are reported of Rh/SiO₂ exposed to 1 : 2 and 2 : 1 mixtures of CO : H₂ at 3 atm total pressure and 503, 523 and 553 K. Linear and bridged CO existed on Rh during reaction which led to methane, methanol and ethanol as the dominant products. IR bands due to adsorbed CH₃ and CH₂ groups primarily resulted from alcohol adsorption on the silica support giving surface methoxy and ethoxy groups. An IR band at 3124 cm^–1 is ascribed to an unsaturated hydrocarbonaceous residue, the build-up of which displaces linearly bonded CO from the Rh surface and also decreases the catalyst selectivity for methane formation.