An Efficient Cu/BaO/La2O3 Catalyst for the Simultaneous Removal of Carbon Soot and Nitrogen Oxides from Simulated Diesel Exhaust

Abstract

A three-component Cu/BaO/La2O3 catalyst has been developed as a highly efficient catalyst for the simultaneous removal of carbon soot and NO gas from diesel emissions. The influence of transition metals (Cu, Pd, Ni, Co, and Pt) deposited on BaO/La2O3 supports and cosupports (BaO, SrO, CaO, and CeO2) combined with La2O3 were investigated. The Cu/BaO/La2O3 catalyst completely combusted 50 wt % carbon soot under an O2 atmosphere, with a T50% temperature of 375 °C. This catalyst also exhibited the highest activity among the investigated catalyst systems for the simultaneous removal of carbon soot and NO gas, even at low temperatures. The absence of carbon soot substantially decreased the NO conversion rate that suggested carbon soot acts as a solid reductant for the NO reduction. The high activity of the Cu/BaO/La2O3 system can be attributed to the high oxygen storage capacity (OSC) of the BaO phase on La2O3 and to the redox properties of the Cu species that are attributable to strong Cu–BaO interactions. The Cu/BaO/La2O3 also exhibits high durability and good recyclability without any appreciable loss of catalytic activity. We propose that the present catalytic reaction consists of two reaction pathways: (i) direct soot oxidation by surface oxygen species and (ii) NOx-assisted soot oxidation. The use of significantly cheaper Cu rather than noble metals makes the Cu/BaO/La2O3 catalyst a strong candidate to satisfy today’s industrial requirements because of its lack of a precious metal.