Removal of automotive emissions by modified three-way catalysts

Abstract

The objective of this study is to modify the conventional three-way catalysts using base metals. The catalytic performance of the modified catalyst was compared with the conventional three-way catalyst. The composition of the modified catalyst was selected by using atomic mass ratio as criterion. Pd and Co were selected because they have atomic mass ratios near that of Pt/Rh of the conventional three-way catalyst. The result shows that the active site for NO reduction may be the combination between Pd and Co in a suitable ratio. The suitable ratio of palladium to cobalt for preparing the modified three-way catalyst is 1 : 1. In addition, it was observed that the calcination of the catalyst under a reducing atmosphere and at a high temperature (700 degree celsius for 7 hrs.) or pretreat by simulated exhaust gases (rich condition) could enhance the efficiency of the modified three-way catalyst, especially for carbon monoxide and propane oxidation. However, NO reduction is inversely and simultaneously affected. The reason for this phenomenon may be because the strength of oxygen adsorption of a reduced modified three-way catalyst is higher than that of a conventional three-way catalyst. In addition, the window operation of a modified three-way catalyst is 1 ± 0.03