Diesel Particulate Filters: Catalyst Types

Depending on the application, Nett® S-Series or F-Series particulate filters can be ordered with one of the following catalyst types:

• Standard catalyst
• Sulfate-suppressed catalyst

The standard catalyst provides the best activity and the lowest regeneration temperature requirements. However, if high sulfur fuels are used, the catalyst may generate sulfate particulates at elevated temperatures. As a general guideline, the standard catalyst should be used in the following applications:

• All applications with ultra low sulfur fuel (S < 50 ppm).
• All applications, regardless of fuel sulfur level, where sulfates are not considered a particulate emission and are not regulated. Examples of such applications include underground non-coal mining in the U.S. (particulates measured as total carbon) or occupational health environments in Germany (particulates measured as elemental carbon).

The sulfate-suppressed catalyst eliminates the sulfate creation at the expense of a slightly increased regeneration temperature requirement, typically 10-15°C. This catalyst is used for applications with high sulfur fuel (S > 50 ppm) which are sensitive to sulfate particulate emissions, such as most urban buses operated on high sulfur fuels.