Carbon Monoxide is a fatal poison for any air-breathing animal. (CO)
Nitrogen Oxides leads to smog and acid rain. (NOx)
Hydro Carbons produce environmentally unsafe smog. (HC)
The catalyst also converts Diesel Particulate Matter (DPM) which consists of soot, ash, dirt, sand and dust.
So A Catalytic Converter heats up and then increases the reactions of CO, HC, NOx and DPM. The higher the temperature, the better the catalyst works. A minimum exhaust temperature of 200°C is needed for “light off” of the catalyst. The higher the temperature of the exhaust is, the more efficient the catalyst will be.
They can be used and are efficient, on all CNG, LPG and Diesel Petrol engines.