Search Results

For diesel exhaust aftertreatment applications with space limitations, as well as to move the selective catalytic reduction system (SCR) to a warmer location closer to the engine, DOC on CSF technology can be used. This technology combines the diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) functionalities in one component, thereby enabling volume reduction. DOC on CSF maintains the abatement of hydrocarbon (HC), carbon monoxide (CO), and particulate matter (PM), and the oxidation of nitric oxide (NO) to nitrogen dioxide (NO2) for passive soot oxidation and fast SCR reaction of NOx on a downstream SCR catalyst. In this study, the performance of DOC on CSF was compared to a DOC + bare diesel particulate filter (DPF) and a DOC + CSF system, to understand the performance benefits and challenges. All the components were optimized individually for their respective functions. The DOC on CSF was optimized for NO oxidation and passive soot oxidation performance.

Future heavy-duty diesel (HDD) engines are designed to have higher engine out NOx, for improved fuel economy, while reduction of the emission control technology footprint is also desired. Consequently, higher NOx reduction across compact emission control systems is required. Selective catalytic reduction (SCR) catalyst coating combined with a wall flow particulate filter (SCRF®1) is a technology that enables abatement of NOx emissions in addition to oxidation of soot from diesel engine exhausts. Vanadia based-SCR is well known for NOx reduction and is active for hydrocarbon (HC) and particulate matter (PM) oxidation. This dual functionality (oxidation and reduction reactions) of the V.SCR catalysts plus the filtration achieved by the filter substrate can help certain diesel engine applications achieve the legislative limits with a reduced packaging volume.

A combined experimental and modeling study was carried out to investigate the effects of Pt:Pd ratio on the performance of diesel oxidation catalysts (DOC) for heavy-duty applications1 (PGM<50 g/ft3). In the first part of this work, transient light-off and steady-state experiments were performed over a series of hydrothermally aged DOCs with different Pt:Pd ratios and PGM loadings. It was found that n-decane and NO oxidation activities increased monotonically as the Pt:Pd ratio was increased while the oxidation of unsaturated hydrocarbons (HC) (C3H6 and C7H8) first increased with an increase in Pt:Pd ratio and then plateaued at higher Pt content. In contrast, the CO oxidation exhibited opposite trend, with the catalyst containing low Pt (high Pd) level being more active. The presence of HC lowered the outlet NO2/NOx ratio by reducing the NO2 generated via NO oxidation back to NO. The negative effect of HCs on NO2/NOx ratio increased in the order: C3H6

The use of vanadia selective catalytic reduction (V-SCR) catalysts for NOX reduction from diesel engine exhaust is well known. These catalysts are also active for hydrocarbon (HC) and particulate matter (PM) oxidation. This dual functionality (oxidation and reduction) of V-SCR catalysts can help certain applications achieve the legislative limits with an improved margin. In this work, NOX reduction, HC and CO oxidation over V-SCR were studied independently and simultaneously in microreactor tests. The effect of various parameters (HC speciation, concentration, ANR, and NO₂/NOX ratio) was investigated and the data was used to develop a kinetic model. Oxidation of CO, C₃H₆, and n-C₁₀H₂₂ is first order in CO/HC, while C₇H₈ oxidation is less than first order in C₇H₈. All these reactions were zero order in O₂. Oxidation activity decreased in order: C₇H₈ ≻ n-C₁₀H₂₂ ≻ C₃H₆ ≻ CO. HC oxidation was inhibited by NH₃.

Aftertreatment devices are exposed to exhaust poisons from fuel, oil and coolant. Studies on fuel- and lubricant-based poisoning have been widely published. However, diesel oxidation catalyst (DOC) and catalyzed soot filter (CSF) performance after exposure to constituents of coolant is not fully understood. Exhaust gas recirculation (EGR) cooler failure can cause a coolant leak into the exhaust that can reach the exhaust aftertreatment system. Coolant contains elements that can cause deterioration of aftertreatment components. This study focuses on the poisoning effect of coolant on the performance of a DOC + CSF system. The coolant introduction simulates an engine failure such as an EGR cooler internal fracture. DOC NO oxidation, quenching and hydrocarbon (HC) slip control performance during active regenerations are evaluated after slow and after consecutive fast coolant introduction and compared to the performance before the coolant exposure.