Rh/Al 2 O 3 –La 2 O 3 catalysts promoted with CeO 2 for ethanol steam reforming reaction

Abstract

Abstract Rh-based catalysts supported on γ-Al2O3–La2O3 modified with CeO2 promoter were prepared in the present work. The objective was to study the promotional effect of the addition of different CeO2 contents and 15 wt% La2O3 on the stability of Rh/γ-Al2O3 catalysts for ethanol steam reforming reaction. The physico-chemical characteristics of the catalysts, activity and the deposition of carbon on the catalyst surface were surveyed by NH3-TPD, XRD, TPR, XPS, DRIFT, TPO-TG and Raman. The stability of Rh/γ-Al2O3 catalyst was effectively improved by the addition of 15 wt% La2O3 and 5 wt% CeO2, as the carbon deposition rate was reduced significantly (from 2.3 to 0.16 mgcoke gcat−1 h−1). The role of the promoter was to decrease the selectivity to ethylene by modification of Lewis acid sites on the support and the removal of carbon deposits during the reaction. This is achieved through the formation of lanthanum oxycarbonate from La2O3 and higher amount of mobile lattice oxygen induced by the CeO2 promoter. This catalyst exhibited good selectivity to H2, with no presence of C2 intermediates above 723 K; in addition this catalyst was stable up to 48 h of time on stream at 773 K. Furthermore, the original activity of the catalyst was recovered through regeneration by the removal of some carbon deposits which are potential causes of deactivation.