Investigation of performances of commercial diesel oxidation catalysts for CO, C₃H₆, and NO oxidation

Authors: HANDE GÜNEŞ, DENİZ ŞANLI YILDIZ, HÜSEYİN BARKIN ÖZENER, GÖKHAN HİSAR, SELMİ ERİM BOZBAĞ, CAN ERKEY

Abstract: Four commercial monolithic diesel oxidation catalysts (DOCs) with two different platinum group metal (PGM) loadings and Pt:Pd ratios of 1:0, 2:1, 3:1 (w/w) were investigated systematically for CO, C₃H₆, and NO oxidation, CO-C₃H₆ co-oxidation, and CO-C₃H₆-NO oxidation reactions via transient activity measurements in a simulated diesel engine exhaust environment. As PGM loading increased, light-off curves shifted to lower temperatures for individual and co-oxidation reactions of CO and C₃H₆. CO and C₃H₆ were observed to inhibit the oxidation of themselves and each other. Addition of Pd to Pt was found to enhance CO and C₃H₆ oxidation performance of the catalysts while the presence and amount of Pd was found to increase the extent of self-inhibition of NO oxidation. NO inhibited CO and C₃H₆ oxidation reactions while NO oxidation performance was enhanced in the presence of CO and C₃H₆ prob-ably due to the occurrence of reduced Pt and Pd sites during CO and C₃H₆ oxidations. The optimum Pt:Pd ratio for individual and co-oxidations of CO, C₃H₆, and NO was found to be Pt:Pd = 3:1 (w/w) in the range of experimental conditions investigated in this study.

Keywords: aftertreatment systems, diesel oxidation catalyst, bimetallic catalyst, platinum, palladium, commercial monolith

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