Catalyst operation
In a car, a catalyst is a ceramic particle coated with noble metals - platinum and rhodium, placed in a special container. Exhaust gases passing through this container flow around the particles, which have a very large total active surface. The total amount of noble metals contained in the catalyst is 2-3 grams (5 parts platinum to 1 part rhodium). Thanks to the three-stage catalyst, it is possible to get rid of harmful substances such as CO, CH and CNx.
CO and CH, oxidized by oxygen, turn into harmless carbon dioxide CO ₂.
To neutralize NOx, a chemical reaction is used to remove oxygen. This produces nitrogen (N ₂) and CO ₂. Both substances are harmless.
Information copied from the website mitsubishiman.ru
The catalyst only works under certain conditions. For this, there must be a certain ratio of fuel and air. The greatest difficulty is to maintain this ratio constant when operating conditions change. This is the task of lambda regulation.
The catalyst can only work when the temperature reaches 300°C. This is usually achieved in 25-28 seconds, but in city traffic conditions it may take up to three minutes. On the other hand, the catalyst is very sensitive to overheating. At a temperature of 900°C, its efficiency drops sharply. At a temperature of 1200°C, it can be destroyed. If the catalyst is present, unleaded gasoline is required. When using leaded gasoline, the catalyst stops working after 2-3 refuelings.
Operating mode with a catalyst
When operating a car with a catalytic converter, the remains of unburned mixture are especially dangerous, as they can ignite inside the hot catalytic converter, and the temperature can exceed the critical value. As a result, the catalytic converter can partially melt and stop functioning.
That's why:
Rolling, idling and towing the vehicle are all possible without problems if the starter is unable to start the engine due to a discharged battery.
Push starting of the engine is not allowed, since it allows a large amount of unburned fuel to enter the exhaust system, which can damage the still hot catalytic converter.
If there are interruptions in the ignition, which may indicate its malfunction, it is necessary to take urgent measures. When driving further, high revs should be avoided.
Small amounts of unburned mixture do not pose a danger, especially if it enters a cold catalytic converter.
Overheating of the catalyst cannot occur during prolonged movement at full throttle, since in this mode the catalyst cools down.
Besides:
In the summer heat after a long drought, do not park your car on dry grass. Under unfavorable conditions, a fire may occur under the car.
When installing underbody protection, do not allow it to touch the catalytic converter or heat shields.
From time to time, support the car and check that the heat shields are not damaged or missing.
What else is useful to know:
High oil consumption is harmless to the catalytic converter. Since oil consists essentially of the same elements as gasoline, burnt oil is deactivated by the catalytic converter in the same way as burnt fuel.
Additives added to fuel and motor oil do not harm the catalyst.
Defects in the catalytic converter or lambda probe are detected only by properly performing exhaust gas testing. A catalytic converter damaged by high temperatures can be identified by a knocking sound, since the ceramic filler, when partially melted, crumbles and begins to roll around inside the metal container.