CeαMn1-αO2 CATALYSTS SUPPORTED OVER g-Al2O3 PREPARED BY MODIFIED REDOX-COPRECIPITATION METHODS FOR n-HEXANE COMBUSTION

Abstract

A series of Ce α Mn 1-α O 2 catalysts supported on g-alumina with various molar concentrations of Ce (α, from 0 to 0.90) was synthesized by coprecipitation, applying two different precipitating agents, namely, sodium hydroxide (method 1) and sodium carbonate (method 2), with the use of sodium permanganate as a redox agent for precipitation. XRD profiles of the supported samples revealed the predominant abundance of a typical fluorite crystalline structure. TPR thermograms of supported samples were displaced towards lower temperatures with increasing Mn concentration, in contrast with the bulk samples. The supported Ce-Mn samples exhibited a greater performance in n-hexane elimination than did the corresponding simple oxides. The sample Ce 0.33 Mn 0.67 O 2 obtained by method 2 presented the best activity, probably due to the enrichment of Ce 4+ , Mn 3+ and Mn 4+ surface species, an excess of superficial oxygen species and an easy reducibility as well as the lowest apparent activation energy.