Improved stability of Ni/Al2O3 catalysts by effect of promoters (La2O3, CeO2) for ethanol steam-reforming reaction

Abstract

Ni-based catalysts supported on γ-Al2O3 modified by La2O3 and CeO2 promoters were prepared in the present work. The objective was to study the promotional effect of addition of 15wt% La2O3 and different CeO2 contents on stability of Ni/Al2O3 catalysts for ethanol steam-reforming reaction. The physical chemical characteristics of the catalysts, activity and the carbon deposition on the catalyst surface were carried out by TEM, NH3-TPD, XRD, TPR, XPS, DRIFT, TPO-TG and Raman. The stability of Ni/γ-Al2O3 was effectively improved by addition of 15wt% La2O3 and 10wt% CeO2 as the carbon deposition rate was reduced 72% compared with catalyst supported on bare alumina. The role of promoters was to decrease the selectivity to ethylene by reduction of strong Lewis acid sites of γ-Al2O3 and the removing carbon deposits during reaction, through both lanthanum oxycarbonate formations from La2O3 as the higher amount of mobile lattice oxygen induced by the CeO2 promoter. This catalyst showed good results of selectivity to H2, no presence of C2 intermediates above 723K and it was stable up to 48h of time-on-stream at 773K. In addition, it was possible to recover part of the original catalyst activity after a reactivation process, in order to remove some carbon deposits as potential causes of deactivation.