Tandem Base-Metal Oxide Catalyst for Automotive Three-way Reaction: MnFe2O4 for Preferential Oxidation of Hydrocarbon

Abstract

A combination of two base-metal oxides in tandem configuration can realize three-way reaction without platinum group metals. For this purpose, catalysts for hydrocarbon preferential oxidation (HC-PROX) and for NO reduction by CO are required. For the design of HC-PROX catalysts, competitive oxidation of propene and CO on spinel-type MFe2O4 (M= Co, Cu, Mg, Mn, Ni, Zn) was investigated. MnFe2O4 preferentially oxidized propene in the co-presence of CO showing the best propene oxidation activity. Among the series of MFe2O4, the activity controlling factor was correlated to the M-O bond energy of the second metal oxides, and the HC preferential oxidation property was dependent on the electronegativity of the second ion. A tandem catalyst using MnFe2O4 for HC-PROX and CuCo2O4 for NO-CO reaction showed TWC activity comparable to a Rh/CeO2.