DOC Diesel Oxidation Catalyst EU4/5/6 Ceramic/Metal Honeycomb Substrate

DOC (Diesel Oxidation Catalyst)

Used as stand-alone emission control devices, most commercial DOCs were optimized for the reduction of diesel particulate matter emissions. The DOC accomplishes that goal through the removal of the particulate matter’s heavy organic fraction (OF). Certain emission regulations—for instance EU standards for diesel passenger cars—include stringent limits for gaseous HC and CO emissions, which must be reduced over the catalyst as well, often with high efficiencies. DOCs designed for PM/HC/CO control also reduce several unregulated emissions, such as aldehydes and PAHs, as well as the diesel odor.

In their auxiliary catalyst capacity in DPF/SCR systems, DOCs are used primarily as (1) NO2 generating catalysts, and/or (2) “heat-up” catalysts for thermal management of DPF/SCR aftertreatment. An increased NO2/NOx ratio promotes passive DPF regeneration (i.e., oxidation of soot collected in the filter), and can enhance NOx reduction efficiency in SCR catalysts. The role of the heat-up catalyst is to oxidize hydrocarbons—introduced via diesel fuel injection into the exhaust system or post-injection in the engine—to increase the exhaust gas temperature and facilitate active DPF regeneration. If both of these functions are required on a given engine, they are typically combined in one DOC by zone-coating of two DOC formulations optimized for the respective activity.

Diesel engines normally run lean (more air than fuel), and therefore a diesel autocatalyst usually operates as an oxidation catalyst (which is why it is known as a diesel oxidation catalyst or DOC) cutting CO and HC emissions by more than 90%.

• CO + ½ O2 → CO2
• [HC] + O2 → CO2 + H2O

Many diesel particulate filter (DPF) systems incorporate an oxidation catalyst, either as a coating on the filter or as a separate element.

WFEC has developed a series of DOCs to meet China Stage VI or Euro 6, non-road mobile machinery Tier IV, and above emission regulations. The DOCs shows more excellent catalytic performance with improving coat materials and coating process technology.