Carbon Monoxide Oxidation on LaCoO3 Perovskite Type Catalysts Prepared by Reactive Grinding

Abstract

Perovskite oxides are used as promising three way catalysts for the removal of exhaust gases because of their low cost, thermal and mechanical stability at relatively high temperature, great diversity and excellent redox properties. The major traditional drawback of perovskites is the low specific surface area (usually several m2/g) due to their preparation that involves a rather high temperature (often as high as 800 0C) to ensure the formation of the crystalline phase. This suppresses their activity and to some degree limits their application. A new preparation method called reactive grinding was developed for the synthesis of perovskites at room temperature via high-energy ball milling resulting in a relatively high surface area. Perovskite type mixed oxides LaCoO3 with high specific surface area was prepared by reactive grinding. These catalysts was characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM) - Energy dispersive Xray spectroscopy (EDX or EDS) and BET surface analysis. The formation of the perovskite structure has been shown by X-ray diffraction (XRD) for all samples. The catalytic performance of the samples for carbon monoxide was evaluated. LaCoO3 found significantly more active than a reference sample prepared by conventional synthesis method using amorphous citrate complexes. The activity per unit surface area was found to depend on grinding conditions and calcinations temperature. These enhanced activities are associated with both rather high surface area and high defect density reached by the reactive grinding synthesis method.