What Is a Catalytic Converter & What Does It Do?



The exhaust fumes from the engines of vehicles running on diesel, gasoline, and other gases emit toxic gases, which can harm people and the environment in the surrounding area. Smoke from vehicle exhaust contains a variety of unburned hydrocarbons and harmful gases. Catalytic converters are used to convert these hydrocarbon gases into compounds. In this article, we will learn about the catalytic converter in detail. What is a catalytic converter, and how does it work?

What Is A Catalytic Converter?

The catalytic converter in vehicles is an important part of the exhaust system, converting the combustion gases of the internal combustion engine into water vapor and carbon dioxide into less harmful substances and reducing the number of toxic pollutants emitted into the air. It is installed in the exhaust systems of vehicles. The catalytic converter consists of a metal casing, inside which is a monolith with a ceramic core.

The shape of the catalytic converter is like a honeycomb, in which three types of oxidants, platinum, palladium, and rhodium, are used. Typically, the design of the catalyst in vehicles can be round or square. Which depends on the model of the vehicle.

Catalytic converters are installed in the exhaust systems of nearly all diesel, gasoline, and other gas-powered vehicles. Some vehicles have a single catalytic converter, and some larger vehicles have a dual catalytic converter.

Types Of Catalytic Converters

In general, there are three types of catalytic converters. You will read about them in detail.

1. Oxidation Catalyst (Two-Way Catalyst)

The oxygen in the catalyst reacts with CO and HC and converts them into CO2 and H2O. This reduces the pollution caused by the exhaust gases from the vehicle’s engine combustion process.

In this way, the exhaust manifold receives purified air from the outside to improve this oxidation process. To do this, the exhaust gases are returned to the engine through the EGR valve system. This reduces the NOX in the smoke. This helps to reduce the gases polluted by smoke.

2. Three-Way Catalyst

The three-way catalyst ensures that NOx is removed from the engines of vehicles in addition to the toxic and polluting elements CO and HC. This catalyst NO and O2 reactions activate it as components. This can lead to oxidation, which burns in the smoke. Conversely, CO and HC react as combustion components. As a result, CO2 forms N2 components with H2O. This can greatly reduce the pollutants emitted from the smoke.

3. Three-Way Catalyst & Oxidation Catalyst

Vehicles with catalytic converters vary depending on engine power and size. Such catalysts are designed on the basis of the operation of oxidation catalysts and three-way catalysts. The catalytic converter converts toxic gases and pollutants from engine exhaust into less polluting substances during combustion in the vehicle’s engine by catalyzing a redox reaction in the vehicle’s exhaust gas purification system.

This type of catalytic converter is commonly used in engines that run on diesel and gasoline fuels, as well as lean-burn internal combustion engines. In 1981, a three-way catalytic converter was introduced in modern vehicles at the time.

This is because this catalytic converter helped reduce nitrogen oxides significantly. However, some lean-burn engines use a two-way catalyst. Because the three-way catalyst in this type of engine requires the engine to burn rich or stoichiometric fuel to successfully reduce NOx,.

How Does A Catalytic Converter Work?

The smoke coming out of the engine contains carbon monoxide, nitrogen oxides, CO2, and carbon dioxide. In this, platinum-rhodium is used as the first step in the elimination of nitrogen oxides. Nitrogen oxides enter the catalyst, which contains thousands of tiny microscopic tubes used to transport air.

When nitrogen dioxide enters the catalytic system, The bond of nitrogen to oxygen is then weaker than the bond to the catalyst; once the nitrogen dioxide bonds with the catalyst, it binds to the catalyst, weakening the bond of nitrogen to oxygen. As a result, two oxygen molecules from the smoke are separated and either bind together or combine. Ultimately, however, these two oxygen molecules combine with a third oxygen to form O2.

Thus, once these nitrogen molecules are present alone on the catalyst, they move around to the surface in search of a partner nitrogen and prefer to make this bond there rather than on the catalyst. Once they form a bond with the additional nitrogen, their affinity for the catalyst weakens, and they dissociate to proceed to the next step. This leaves the catalyst with only the safe gases of nitrogen and oxygen, and the surface is now ready to do the work with other elements and molecules.

After eliminating NO2 and NO in the first step, we are left with N2, O2, CO, CO2, H2O, and hydrocarbons. The next step is platinum- and palladium-based oxidation catalysts. In this situation, the surface of the catalyst starts combining with oxygen.

Next, oxygen and carbon monoxide molecules reach the surface and form a bond with it. As a result, the bond between oxygen molecules and carbon monoxide becomes stronger. When they separate after attaching to the surface, they combine with carbon monoxide to form carbon dioxide.

This reaction then stops inside the catalyst and continues outside, where it removes carbon monoxide until the catalyst surface is clean again. In short, your hydrocarbons and oxygen create H2O and CO2. They burn in it and react with the catalyst, producing harmless H2O and ultimately dangerous CO2. After this cycle, only N2, O2, CO2, and H2O remain, and the catalyst is only 90% effective. Some of these poisonous gases still exist. But they can be controlled to a great extent.

What Is Inside A Catalytic Converter?

The catalytic converter is designed to reduce emissions of harmful pollutants from the engine. Inside a catalytic converter, you’ll find a complex structure consisting of several elements:

  • Catalytic Converter: The catalytic converter is made of precious metals like platinum, palladium, and rhodium. These metals act as catalysts to trigger chemical reactions that convert harmful gases into less harmful gases. These include the oxidation of carbon monoxide to carbon dioxide (CO2) in smoke, the reduction of nitrogen oxides (NOx) to nitrogen (N2) and oxygen (O2), and the conversion of unburned hydrocarbons (HC) to carbon dioxide and water.
  • Substrate: The catalyst is supported by a substrate material, often a ceramic or metal honeycomb-like structure. The substrate provides a large surface area to conduct exhaust gases to the catalyst and helps distribute them evenly over the catalyst surface.
  • Shell: The substrate and catalyst are enclosed within a metal shell, usually made of stainless steel. This shell protects the internal components and helps direct the flow of exhaust gases through the substrate.
  • Reduction catalysts: These help reduce nitrogen oxide pollution by removing oxygen. Nitrogen oxides break down into nitrogen and oxygen gases, rendering them harmless.
  • Oxidation catalyst: It is used to convert carbon monoxide into carbon dioxide through the reverse process of adding oxygen, thereby rendering the toxic gases emitted from the smoke harmless.

Why Are Catalytic Converters Stolen?

The main reason for the theft of catalytic converters is the precious platinum, palladium, and rhodium metals used in them. These precious metals are used in catalytic converters to reduce harmful emissions from vehicle exhaust.

The high price of these metals in the catalytic converter makes them an attractive target for thieves who want to make a quick profit by selling them for scrap. To prevent catalytic converter theft, many jurisdictions are implementing regulations that require scrap sellers to verify the identity and maintain records of the catalytic converter buyer.

How To Protect Catalytic Converters From Theft?

  • First, parking in well-lit and secure areas can deter potential thieves. Parking the vehicle in deserted and dark places can be a golden opportunity for thieves.
  • Use a vehicle security system in your vehicle, such as an alarm or immobilizer.
  • Install a catalytic converter cage or shield to physically block access to the converter, making theft more difficult.
  • A unique identification number must be imprinted on the converter.
  • Additionally, some states have enacted laws regulating the sale of used catalytic converters, which may prevent theft.
  • By being alert and taking these precautions, the risk of catalytic converter theft can be reduced to a great extent.
  • Get your vehicle repaired by an independent mechanic in front of you as soon as possible.


Q. What is a catalyst?

Catalytic converters are used to reduce harmful emissions of hydrocarbons, carbon monoxide, and nitrogen oxides into the atmosphere. They convert the harmful gases from the vehicle engine into water vapor and less harmful emissions.

Q. What does a catalytic converter do?

A catalytic converter is an important component in the exhaust system of vehicles. It reduces harmful emissions from the vehicle’s engine. The tailpipe of vehicles converts hydrocarbons, carbon monoxide, and nitrogen gases into oxygen, nitrogen, and carbon dioxide.

Q. How much does a catalytic converter cost?

More expensive metals and other materials are used to make a vehicle’s catalytic converter. Depending on the catalytic converter installed in a normal vehicle, the cost can range from $800 to $1500. But the cost of a catalytic converter for some light and modest vehicles is less than $1000. And the cost of a catalytic converter for some large and luxury vehicles can range from $1800 to $2800.

Q. What happens if you drive without a catalytic converter?

When you drive a car without a catalytic converter, harmful gases from the engine go directly into the atmosphere, and a successful catalytic converter will muffle the vehicle’s engine noise. Without a catalytic converter, the vehicle’s engine will make more noise. And without a catalytic converter, your vehicle will not be fit to pollute because of the higher pollution.

Q. Why do catalytic converters get stolen?

Rhodium, palladium, and platinum are valuable substances used in catalytic converters, and the price of rhodium can average $20,000 per ounce. The reason for this is the theft of the catalyst. And at some point, the theft of catalysts increased.

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