Why The Need for Aftertreatment?

Particle Matter (PM)

Oxides of Nitrogen (NOx)

  • Made up of Carbon Soot (C), Ash, Organic material and sulphates.
  • Worsens preexisting respiratory conditions such as asthma and allergies .
  • Made up of colorless nitric oxide (NO) and reddish-brown, very toxic and reactive nitrogen dioxide
  • (NO2) Contribute to photochemical smog and acid rain

Hydrocarbons (HC)

Greenhouse Gas (GHG)

  • Some have irritating odor, toxic and/or carcinogenic.
  • Contribute to photochemical smog .
  • Comprised of Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Fluorinated Gases
  • Gases that trap heat in the atmosphere raising temperatures

Carbon Monoxide (CO)

  • Colorless, odorless and tasteless gas .
  • Toxic in high concentrations .

WHAT IS A DOC?

dIESEL oXIDATION CATALYST

WHAT does DOC do?

  • PM reduction product
  • Flow-through substrate
    • made of cordierite or metal
    • No maintenance necessary
  • Substrate is coated with precious metals
    • Platinum (Pt) and Palladium (Pd) as catalyst
    • Enables conversion at a lower temperature
    • In general, increasing Pt increases conversion efficiency
  • Compatible with ULSD and 15 PPM & 500 PPM sulfur diesel fuels
  • Provides >90% reduction of CO, HC
  • Provides 25 – 50% reduction of PM
  • Removes Soluble Organic Fraction of PM particle
  • Promotes passive regen of DPF by creating NO2
  • Enhances combustion of diesel fuel in the exhaust stream to generate heat for active regen of DPF
  • Enhances performance of SCR catalyst with creation of NO2

WHAT does DOC do?

  • Provides >90% reduction of CO, HC
  • Provides 25 – 50% reduction of PM
  • Removes Soluble Organic Fraction of PM particle
  • Promotes passive regen of DPF by creating NO2
  • Enhances combustion of diesel fuel in the exhaust stream to generate heat for active regen of DPF
  • Enhances performance of SCR catalyst with creation of NO2

What is DPF? (DIESEL PARTICULATE FILTER)

  • PM reduction product
  • Wall flow filter
    • Every other channel is closed, forcing exhaust gas through walls of filter
    • Made of cordierite or silicon carbide
  • Substrate is typically coated with precious metals
    • Platinum (Pt) as a catalyst
    • Palladium (Pd) as catalyst
  • Requires ULSD at 15 PPM



  • Porous ceramic walls capture soot and ash from exhaust .
    • Soot is removed by periodic regeneration (active / passive)
    • Ash accumulates, requiring DPF removal and maintenance
  • Provides >90% PM reduction
  • Traps Carbon Soot, Ash and Soluble Organic Fraction of particle



WHAT IS regeneration?

Active Regeneration

  • Process of removing accumulated soot by conversion into harmless CO2.
  • Two types of regeneration:
    • Active regeneration
      • Temp achieved by engine management, dosing diesel fuel into exhaust stream or alternative heat source, eg. burner .
    • Passive regeneration, enabled by DOC
      • Requires 18:1 NO2:Soot minimum and Temperature >250°C
      • Conditions occur naturally during normal engine operation .
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What is SRC?

how does it work?

  • Chemical process in which toxic NOx is converted to harmless N2 and H2O
    • Reductant: Ammonia (NH3)
    • Catalyst: Copper Zeolite (CuZ) or Iron Zeolite (FeZ) or Vanadia
  • Flow through substrate, no cleaning necessary
  • Requires ULSD (<50PPM)
  • Ammonia is generated by the use of liquid urea (known as Diesel Exhaust Fluid (DEF) or AdBlue)