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BIR 2024

What Are Diesel Oxidation Catalysts?

Diesel oxidation catalysts (DOCs) play a crucial role in reducing harmful emissions from modern diesel vehicles. As the automotive industry seeks to maximize the value of catalytic converters through recycling, understanding the functionality and significance of DOCs becomes increasingly important. In this article, Edmund Schwenk, Metallurgist/CEO from Noble6, a US-based automotive precious metals experts explores the purpose of DOCs and their contribution to diesel emission control systems.


What Are Diesel Oxidation Catalysts? p
Edmund Schwenk

Everyone is interested in the distinctions between the various types of catalytic converters. This is because catalytic converters are incredibly valuable scrap components which generate extra revenue for the automotive industry. All original equipment manufacturer (OEM) catalytic converters from gasoline-powered vehicles can be sold for a good price, but many people are unsure whether diesel converters can be sold with the same success. The diesel oxidation catalyst and diesel particulate filters will be discussed in detail in this article’s discussion of diesel emission control systems.

There are several abbreviations to be aware of when dealing with diesel-related automotive components. DOC stands for Diesel Oxidation Catalytic Converter. DPF is an abbreviation for Diesel Particulate Filter. DPR stands for Diesel Particulate Reduction System. SCR is an abbreviation for Selective Catalytic Reduction.

Diesel fuel contains more energy per gallon than gasoline, making it more cost-effective overall.

Diesel catalytic converters are either two-way catalytic converters with a diesel oxidization catalyst or three-way converters with SCR reduction. Before being released into the atmosphere, diesel engine gases go through the following four processes:

  • Exhaust Gas Recirculation
  • Diesel Particulate Filtration
  • Diesel Oxidization Catalyst
  • Selective Catalytic Reduction

What Are Diesel Oxidation Catalysts? p two

Diesel Oxidation Catalyst

Every modern diesel vehicle contains diesel oxidation catalysts. They are usually the first part to encounter the toxic gases released by the engine. The diesel oxidation catalyst’s function is to convert carbon monoxide into carbon dioxide and decompose unspent fuel. Although it is the smallest unit in the catalytic converter, it is the most valuable because it contains palladium and platinum, which gives it a high recycling value.

Diesel Particulate Filters

These units, also known as DPFs, deal with the second polluting byproduct of diesel engines that gas engines do not produce: soot or diesel particulates. DPFs, like diesel oxidation catalysts, contain trace amounts of palladium and platinum to aid in catalysis. Diesel particulate filters are also worth considering recycling due to their palladium and platinum content.

Overall, diesel catalytic converters have a lower precious metal load than gasoline-powered OEM catalytic converters, making them less valuable. One significant difference is that DOCs lack the precious metal rhodium, which is the most valuable precious metal found in catalytic converters found in gasoline-powered engines.