Abstract
Diesel oxidation catalysts (DOC) were investigated for oxidation activity, NO conversion stability, and sulfur poisoning/regeneration on Pd/Al2O3, Pt/Al2O3, and Pd-Pt/Al2O3 catalysts. The Pd/Al2O3 catalyst was more active for CO and hydrocarbon (C3H6 and C3H8) oxidation, while the Pt/Al2O3 catalyst efficiently oxidized NO. The formation of a Pd-Pt alloy in the Pd-Pt/Al2O3 catalyst maintained Pd in a more reduced phase, resulting in the superior activity of this catalyst for the oxidation of CO, C3H6, and NO in comparison with its monometallic counterparts. The Pd-Pt alloy not only provided more low-temperature activity but also retained the stability of NO oxidation. The Pd-Pt alloy also favored the spillover of SO2 to the alumina support, resulting in significantly higher adsorption capacity of the Pd-Pt/Al2O3 catalyst, extensively prolonging its lifetime. However, the stable sulfates on Pd-Pt/Al2O3 made it difficult to completely regenerate the catalyst. The bimetallic sample showed higher activity for CO, C3H8, and C3H6 after sulfur poisoning and regeneration.
Highlights
The diesel oxidation catalyst (DOC) is a key unit in the exhaust after-treatment system (EATS) of diesel engines
The results suggest that the bimetallic Pd−Pt/Al2O3 catalyst contains Pd−Pt alloy, in which the metallic Pt maintained the Pd in a more reduced form unlike Pd/Al2O3, in which Pd was fully oxidized in the form of PdO
This work investigated the activity of diesel oxidation catalysts focusing on three main aspects: (i) oxidation activity of CO, NO, C3H6, and C3H8, (ii) NO oxidation stability, (iii) sulfur poisoning and regeneration ability
Summary
The diesel oxidation catalyst (DOC) is a key unit in the exhaust after-treatment system (EATS) of diesel engines. The. DOC primarily oxidizes CO, unburned hydrocarbons (HCs), and NO and thereby plays an important role in meeting emission regulations.[1] The efficiency of the DOC unit is usually evaluated by the conversion of CO into CO2, HCs into CO2 and H2O, and NO into NO2. NO2 still must be removed, an optimum level of NO2 (i.e., NO/NO2 = 1) would enhance the functions of other downstream units such as regeneration of the diesel particulate filter (DPF) and selective catalytic reduction of NOx (SCR-deNOx).[2,3] Several types of catalysts have been investigated considering both catalyst support and active phase.[1] Pt-based catalysts, especially bimetallic Pt−Pd, are often used in DOC units.[1] The addition of Pd into Pt could improve both the durability of a catalyst against sintering and the catalytic performance of CO and hydrocarbon oxidation.[4−7] Bimetallic Pt−Pd catalysts are prepared by an impregnation method with different synthesis routes. The most common route is coimpregnation.[6,8,9]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
