Kinetic Study of a Novel Active and Stable Catalyst for the Water Gas Shift Reaction

Abstract

Two types of catalysts were synthesized and used in the Water Gas Shift Reaction (WGSR): Rh/La 2 O 3 and Rh/La 2 O 3 -SiO 2 . The fresh and used catalysts were characterized through X-ray diffraction (XRD), laser raman spectroscopy (LRS), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The stability tests performed at 673 K (50 h time-on-stream) showed that the Rh/La 2 O 3 slowly deactivated while Rh/La 2 O 3 -SiO 2 exhibited high stability at least for 50 h on stream. The instrumental techniques offered some clues to explain the possible causes of deactivation of one formulation and the high stability of the other. The latter catalyst was more active than most high-temperature formulations reported in the literature. The kinetic measurements were made at atmospheric pressure and reaction temperatures between 598 and 723 K. The results obtained were fitted by a Langmuir−Hinshelwood mechanism assuming that the rate-determining step was the surface reaction of adsorbed CO and H 2 O. The parity plot showed a good correlation between the experimental and calculated reaction rates. The thermal parameters calculated with this model were all physically consistent. They were compared to kinetic, thermodynamic, and calculated data reported in the literature.