DRIFT Studies of Adsorbed CO Over Sulfided K–Rh–Mo/Al2O3 Catalysts: Detection of Rh–Mo–S Phase

Abstract

Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy was used to study the nature of active species in K–Rh–Co–MoS2/Al2O3 catalyst by means of probing with CO molecule. The effects of K addition to Rh and interaction between Mo and Rh were studied with varying K and Mo loadings over 1 wt% Rh/Al2O3 catalyst. In sulfided Rh–Mo/Al2O3, the formation of Rh–Mo–S phase was evidenced first time by a band at 2,095 cm−1. The introduction of Co to K–Rh–MoS2/Al2O3 catalyst showed the existence of both Rh and Co promoted MoS2 sites, but the CO absorption frequencies in DRIFT spectra are significantly at lower side compared to Co free Rh–Mo catalyst. The stabilities of CO band from Rh and Co promoted and unpromoted MoS2 sites are studied at different temperatures. When activated carbon used as support, bands for both promoted and unpromoted MoS2 sites were appeared, but the intensity of these bands were decreased largely compared to alumina based catalyst, resulted from the coverage of added K not only on the support surface but also on the active metal components due to the neutral nature of activated carbon.