How does a Catalytic Converter Work in Cars?


In populous cities of any country, vehicles are no less than a gift of God. However, these vehicles are also the source of air pollution besides providing use ease to move. Their engine produces harmful gases to cause air pollution, affecting our health.

Thanks to concern authorities, they had introduced some laws to reduce the pollution caused by vehicles. These laws had forced the automaker to make some changes in their designs. One of those changes is the Catalytic converter. The purpose of the catalytic converter is to convert harmful gases into harmless gases before they leave the car engine through the exhaust system.

Are you wondering what is a catalytic converter? And how does a catalytic convert work? If so, you’re at the right place. We would guide you thoroughly about the catalytic systems. For instance, we’ll learn what pollutants the car engine produces and how catalytic convert works to remove them.

What are the pollutants produced by car engines?

Petroleum products, such as gasoline that we use to fuel our cars, are made up of hydrocarbons and some additives. These products burn to produce carbon dioxide, water, and some by-products. By-products contain many air pollution-causing components.

These components include:

  • Carbon dioxide: It’s the primary cause of global warming.
  • Carbon monoxide: It’s a colourless gas that is poisonous to humans. CO causes dizziness, unconsciousness, and sometimes death.
  • VOCs: These pollutants are produced by unburned fuel and are the primary cause of smog.
  • Nitrogen oxides: the oxides of nitrogen, such as nitrogen dioxide and nitrogen peroxide, are the reasons for acid rain. Moreover, these oxides are also responsible for smog. When it comes to human health, they can irritate eyes and reduce visibility. Furthermore, they also result in a decrease in vegetation.

What is a catalytic converter?

A catalytic converter is the most crucial part of the vehicle’s engine. It aims to reduce air pollution by converting harmful substances such as oxides of nitrogen and Carbon monoxide into harmless substances such as water vapors and carbon dioxide.

In simple words, you can say that it’s a metal box that works for cleaning emissions of the engine. As a result, clean and less harmful emissions come out of the engine. However, it’s not as simple as it seems. The science behind this process of cleaning emissions is quite complex.

The molecules of harmful pollutant gases consist of harmless atoms. The Catalytic converter function breaks down these gas molecules into harmless particles before they leave the engine. Some catalysts such as platinum, palladium, and rhodium are also present in the catalytic convertor to speed up the reaction.

A temperature of about 400 ℃ is required for the catalytic converter to carry out this reaction. That was why the catalytic converter was present near the engine to achieve the optimum temperature quickly. But, it results in some other engine issues.

In modern cars, auto companies have changed the position of the catalytic converter. It’s now present beneath the vehicles near the outlet pipe.

What are the different parts of a catalytic converter?

To understand how a catalytic converter works, it’s essential to know the catalytic converters basics. These parts are as follows:

  • Stainless Steel Body:

The catalytic converter has a stainless-steel body, ensuring durability and long life. Moreover, its body is in the ribbed form that minimizes the distortion and form pockets. As a result, the cushioning mat will have no direct contact with exhaust gases.

  • Monolithic Free-Flowing Substrate:

The substrate is the backbone of the catalytic converter. It’s the place where wash coat and metal come in contact to allow the chemical reaction to occur. While engineering coatings, it was made sure that they can withstand the high temperature.

  • Catalyst mat:

The catalyst cushions the converter substrate of the car. Moreover, it aligns the ceramic catalyst in place.

  • Heat Shields:

Heatshield protects the undercarriage of the car from heat.

  • Metal catalysts:

Precious metals, such as platinum act as a catalyst for the conversion reaction.

How does the catalytic converter work?

When it comes to catalytic converter types, these are of two types:

  • Two-way converter:it undergoes only two types of chemical reaction. These reactions are only two oxidation reactions. That’s why it’s less effective.
  • Three-way converter:it means three types of reactions are occurring in it.

Both these types of converters work with the help of catalysts. Catalyst is the substance that speeds up the chemical reaction without being consumed. When it comes to catalyst construction, it’s straightforward.

Ceramics and catalyst coated honeycomb-like structures allow the flow of gases. This honeycomb-like structure makes the surface area more prominent. The more the surface area, the quicker the reaction would be. This catalyst construction also minimizes the number of catalysts, minimizing the cost.

There are two types of catalysts for cars. In this section, we’ll learn how a catalyst works.

  1. Catalysts are catalyzing the reduction reactions:These catalysts remove nitrogen oxides by reduction. They convert the nitrogen oxides into harmless oxygen and nitrogen. Platinum and palladium are the main catalysts for this reaction. These catalysts get attached with the nitrogen of the nitrogen oxides, letting the oxygen-free. The oxygen atoms combine to form oxygen gas, and nitrogen atoms combine to form nitrogen molecules.

2NO => N2 + O2 or 2NO2 => N2 + 2O2

  1. Catalysts are catalyzing the oxidation reactions:Other catalyst works by catalyzing the oxidation reaction. It catalyses in two ways:
    • Convert CO into CO2. The reaction for this conversion is represented as:

2CO + O2 => 2CO2

  • Unburned hydrocarbons into water and carbon dioxide.

After the catalyst converter has completed all the reactions, harmless gases are released through the exhaust pipe. These harmless gases are carbon dioxide, oxygen, nitrogen, and steam.

Do catalyst converters work for diesel engines?

Catalyst converters also work in diesel engines but in different ways:

Diesel engines contain only two-way converters. So, they can catalyse just the oxidation reaction for the removal of gases.

Diesel catalytic converter doesn’t contain reduction catalysts, leaving nitrogen catalysts in the atmosphere.

These types of engines are present in large vehicles such as trucks. So, these converts have to deal with massive engines with more exhaust volume. A single catalytic convert becomes useless in such a situation. That’s why; more than one catalyst converters fitted in line are used to tackle this issue


So, it’s always important to know how a catalytic converter works as your car also has one. If there were no catalyst converter, there might be a lot of unhealthy smoke around you. Not only smoke, but you also have to encounter smog more often, especially in bigger cities.

In such a situation, a catalyst converter plays its role in keeping you and your environment safe from harmful gases. As you know very well, for every good, there is a bad. The same is the case here. According to the Intergovernmental Panel for Climate Change, a catalytic converter provides short-term benefits and long-term disadvantages. According to them, nitrous oxide produces them is the reason for long-term damage to the environment.

However, advancement in technology has updated the catalytic converters. The new catalytic converters produce less amount of nitrous oxide. Moreover, their role in reducing harmful components such as hydrocarbons and CO is also appreciable.


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