Diesel Oxidation Catalyst

Do you have a backup diesel generator that causes you odor problems every time you test it?

Diesel engines are characterized by relatively low exhaust gas temperatures. When diesel engines operate at idle or with low engine load, the catalyst temperature may be lower than required for catalytic conversion. At such conditions, the exhaust pollutants may pass untreated through the catalytic converter.  When this occurs, the odors sent to atmosphere have a high probability of being introduced into a nearby building through outside air intakes or open doors.

GPS has developed a diesel catalyst technology to enhance the low temperature performance of the traditional diesel oxidation catalyst. This technology incorporates hydrocarbon trapping materials into the catalyst washcoat. Zeolites, also known as molecular sieves, are most frequently used as the hydrocarbon trap. These zeolites trap and store diesel exhaust hydrocarbons (diesel odors) during periods of low exhaust temperature, such as during engine idling. Then, when the exhaust temperature increases, the hydrocarbons are released from the washcoat and are oxidized on the catalyst. Due to this hydrocarbon trapping mechanism, the catalyst exhibits low hydrocarbon (HC) light-off temperatures (Figure 1) and excellent diesel odor control.

Hydrocarbon Chart

GPS offers the hydrocarbon trap technology in its D-Series diesel catalysts. All GPS’ D-Series catalysts incorporate zeolites in their washcoat. They are capable of 40-50% HC conversion and effective diesel odor control at very low exhaust temperatures.

GPS-DOC GraphicGPS-DOC Cut Away View

The HC trapping catalysts are designed to work at transient engine conditions.  Since the low temperature performance occurs through adsorption rather than through catalytic conversion, periods of hot exhaust temperature are needed for hydrocarbons desorption and regeneration of the catalyst; otherwise, the adsorption capacity will become saturated and increasing HC emissions will pass through the catalyst. The amount of zeolites in the GPS D- Series catalysts are sufficient for effective low temperature HC and odor control for a period of 15-30 minutes, before the trap saturates.

As long as the diesel generator is tested under a sufficient load, the exhaust gas will be high enough to regenerate the catalyst making the zeolites empty and ready to adsorb the odors at the next cold start.