GF49.10-P-2010MAR Three-Way Catalytic Converter, Component Description

GF49.10-P-2010MAR Three-way Catalytic Converter, Component Description
ENGINE 156.981 in MODEL 230.470 as of Model Year 09 /Modification Year 08 model refinement package





Front view of exhaust system

157 Firewall catalytic converter
158 Underfloor catalytic converter

Location
Two separate catalytic converters each are used per exhaust chain.

Task
Reducing the exhaust gas emissions:

- Nitrogen oxides (NOX)
- Hydrocarbon (HC)
- Carbon monoxide (CO)





Design
Schematic diagram

1 Ceramic monolith
2 Wire mesh (embedded)
3 Double-walled housing (insulation)
4 Substrate (washcoat) with a coating of rare metal

Ceramic monoliths are ceramic bodies through which pass several thousand small passages. The exhaust gas flows through these passages. The ceramic consists of high temperature-resistant magnesium aluminum silicate.
The monolith, which is extremely sensitive to voltages, is embedded in an elastic wire mesh made of high-alloy steel wires and fitted in a double-walled stainless steel housing.

Ceramic monoliths require a substrate (washcoat) of aluminum oxide (Al2O3) that expands the active surface of the catalytic converter by an approximate factor of 7000.

The active catalytic layer coated on the substrate consists for three-way catalytic converters of platinum, rhodium and palladium.
Platinum and palladium accelerate oxidation of hydrocarbons (HC) and carbon monoxide (CO). Rhodium assists reduction of nitrogen oxides (NOX).





Function
Schematic diagram

A Unpurified exhaust
B Purified exhaust
F Rich mixture
M Lean mixture
Lambda (air/fuel ratio)

CO Carbon monoxide
CO2 Carbon dioxide
HC Hydrocarbon
H2O Water
N2 nitrogen
NOX Nitrogen oxides

The exhaust gases flow through the catalytic converter and, in so doing, come into contact with the rare metals platinum, rhodium and palladium.
^ Through oxidation, carbon monoxide (CO) is converted into carbon dioxide (CO2) and hydrocarbons (HC) into water (H2O)+carbon dioxide (CO2).
^ Through reduction, nitrogen oxides (NOx) are converted into nitrogen (N2)+ carbon dioxide (CO2).

Crucial for pollutant conversion of pollutants is the residual oxygen content in the exhaust. The best pollutant conversion is obtained at lambda equals 1.

Operating conditions
For a catalytic converter the operating temperature is decisive.
Significant pollutant conversion only begins from an operating temperature of about 250°C.
Ideal operating conditions for high conversion rates and a long life prevail at temperatures between around 400 to 800°C.
A temperature >850°C, as can occur when there are combustion misfires, leads to thermal destruction of the catalytic converter (melting of the monoliths).

Owing to its property of being able to reduce three polluting components simultaneously, it is called a "three-way catalytic converter".