Characterization of CeO2 doped MgAl2O4 prepared by the chelating agents-assisted impregnation method

Abstract

MgAl2O4 spinel employed as support of reforming catalysts was doped by CeO2. The samples were prepared by wet impregnation from aqueous solutions of cerium nitrate, with and without chelating agents. The chelating agents used were ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and citric acid (CA) at different pH of impregnation. The solids were characterized by TG, XRD, SBET, TPR, SEM-EDX and CO2−TPD. Nanoparticles of CeO2 between 5 and 6.8 nm were obtained by the thermal decomposition in air at 600 °C. The surface cerium reduction occurred in a wide temperature range of 450° to 670 °C. The use of citric acid at pH= 8 led to the lowest crystallite size of CeO2 and the lowest interaction with the spinel. The H2 consumption and extent of CeO2-support interaction did not show a clear dependence with the CeO2 crystallite sizes. The use of chelating agents in the impregnation step did not modify the total basicity. Slight changes in the strength of weak basic sites were observed.