What is the working principle of a three-way catalytic converter?
2 Answers
The working principle of a three-way catalytic converter is to transform harmful gases such as CO, HC, and NOx emitted from vehicle exhaust into harmless carbon dioxide, water, and nitrogen through oxidation and reduction reactions. It is the most important external purification device installed in a vehicle's exhaust system. Composition of a three-way catalytic converter: A three-way catalytic converter generally consists of four parts: the shell, vibration damping layer, substrate, and catalyst coating. The shell is made of stainless steel to prevent the shedding of oxide scales, which could clog the substrate. The vibration damping layer is composed of padding or wire mesh padding, serving to seal, insulate, and secure the substrate. To protect the substrate from damage caused by vibration, thermal deformation, and other factors, the padding is made of expanded mica and aluminum silicate fibers, which are then bonded with adhesive. The substrate is made of honeycomb-shaped ceramic material, though many are also made of metal (including stainless steel) materials. The catalyst is composed of precious metals such as platinum, rhodium, and palladium, which are sprayed onto the substrate to form the purifying agent.
I've studied the automotive exhaust system, and the three-way catalytic converter is truly a marvel of exhaust purification. Installed in the exhaust pipe, it resembles a metal honeycomb box coated with catalysts like platinum, palladium, and rhodium. When hot exhaust gases flow in from the engine, these catalysts trigger chemical reactions that convert toxic carbon monoxide into harmless carbon dioxide, burn unburned hydrocarbons into water and carbon dioxide, and reduce nitrogen oxides – those irritating compounds – into plain nitrogen. Its operation requires two key conditions: the engine must maintain an air-fuel ratio around 14.7:1, neither too lean nor too rich, and the converter needs to reach an optimal temperature of about 400 to 600 degrees Celsius to function effectively. Performance is slightly reduced during cold starts, so driving gently after warming up can improve efficiency. I've also noticed that when it gets clogged or dirty, the vehicle's power and fuel consumption are affected, making regular maintenance crucial.
