Diesel Particle Filter with Catalytic Oxidation.

The DPX-Filter is a patented technology and a registered trademark of Engelhard Corp. USA



  • Mere passive diesel particle filter system without major operation effort
  • Independent regeneration starting at 230°C
  • Broad area of application
  • Simple regeneration upon operation,
  • Very good filter properties



  • Appropriate for all engines starting at 18kW up to 500kW
  • Implies sulfur-free fuels
  • Mandatory for functioning is a specific temperature range between 230°C and 450°C as well as a specific ratio of NO2 towards carbon dioxide (12:1). In contrast to active regeneration the reaction does not need any additional energy



  • VERT certified and accredited
  • Requirements according to TRGS554 fulfilled for Germany
  • Verified and examined by the Swiss Bundesamt für Umwelt (Federal Department for Environment) BAFU as well as by the Suva as far as retrofitting of diesel engines are recommended

(BILD VERT-Zertifikat)





Operating Principle and Technology

The operational principle of a „Wall flow“ particle filter (Image 1) is illustrated in the example of a ceramics monolith with alternately closed channels.

Image 1: „Wall flow“ Principle     

The inflowing exhaust gas is being forced to flow into the porous walls of the input channel into a neighboring channel (output channel) leading into the exhaust tract. The particles themselves deposit on the surface of the channels and within the porous walls thereof.


Image 2: 100 cpsi Cordierite Filter structure

The Engelhard DPXTM –Diesel Particle Filter is a catalytic coated filter made from cordierite (Image 2), being manufactured by PHYSITRON’s technology partner Engelhard/BASF under the trade mark of DPX. This results in a decrease of the soot oxidation temperature from 600°C to approximately 250°C. The filters are based on a monolithic ceramics honeycomb which is equipped with a patented coating made from precious metal and rare earth metals.

In the presence of a catalyst the diesel soot may also be combusted with nitrogen oxide (NO2) instead with oxygen thereof. This combustion process already starts at approximately 230° C, so the filter regeneration’s boundaries are yet pushed downwards further on this behalf. However, the „fuel“ NO2 has yet to be generated within the exhaust stream by oxidation of NO. Where our regeneration strategy is concerned (Image 3) this takes place in an Oxidation Catalyst located upstream to the filter. Within the diesel particle filter this process is reverse (the NO2 reacts with the soot), continuously combusting the soot deposited within the diesel particle filter thereof. Thus the name „Continuous Regeneration Trap“ (CRT), meaning a filter continuously regenerating. This effect is also called passive regeneration.

The DPX-Diesel particle filters with BASF technology (former Engelhard) depend on exhaust temperature and operating conditions from the machine. An appropriate usage profile, namely an exhaust temperature frame of 250°C > 50% of the operating time at DPX-1 (without pre-filter) or 230°C > 35% operating time at DPX-2 (with pre-filter) hast o be reached in order to guarantee safe and full oxidation oft he soot.