DOC (Diesel Oxidation Catalyst)

The diesel oxidation catalyst (DOC) owes its name to its ability to promote oxidation of exhaust gas components by oxygen, which is present in ample quantities in diesel exhaust. When passed over an oxidation catalyst, carbon monoxide (CO), gas phase hydrocarbons (HC), the organic fraction of diesel particulates (OF), as well as non-regulated emissions such as aldehydes or PAHs can be oxidized to harmless products, and thus can be controlled using the DOC. In modern diesel aftertreatment systems, an important function of the DOC is to oxidize nitric oxide (NO) to nitrogen dioxide (NO2)—a gas needed to support the performance of diesel particulate filters and SCR catalysts used for NOx reduction. A comprehensive discussion of DOC reactions, reaction kinetics, and other aspects of the technology can be found in the literature [Russell 2011].

The reaction mechanism over the diesel oxidation catalyst is explained by the presence of active catalytic sites on the surface of the catalyst carrier, that have the ability to adsorb oxygen. In general, the catalytic oxidation reaction includes the following three stages:

1. oxygen is bonded to a catalytic site,
2. reactants, such as CO and hydrocarbons, diffuse to the surface and react with the bonded oxygen, and
3. reaction products, such as CO2 and water vapor, desorb from the catalytic site and diffuse to the bulk of the exhaust gas.

Diesel Oxidation Catalysts (DOC) are catalytic converters designed specifically for diesel engines and equipment to reduce carbon monoxide (CO), hydrocarbons (HC), and soluble organic fractions (SOF). It can be used in combination with CDPF or SCR/SCRF due to its ability of oxidizing NO to NO₂ which improves the passive regeneration and fast-SCR reaction. Injected fuel can also be fast catalytically ignited to initiate the active regeneration of DPFs.

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.