What is a Catalytic Converter? How Do Catalytic Converters Work?

Let’s start with the short answer; The catalytic converter, also known as the catalyst, is a component that enables the harmful gases from the exhaust to be converted into harmless ones.

You must have heard that the gases emitted from the exhausts of vehicles are harmful. Moreover, these harmful gases are one of the primary causes of air pollution. It is a well-known fact that in cities where the population is crowded, the rates of air pollution due to exhaust gases are higher. In order to reduce this pollution, studies have been made for many years and finally the catalytic converter has been introduced.

The catalytic converter has eliminated the emission of harmful gases from the exhausts to the environment by filtering them in a way. This system, which started to be used in 1975, works with a simple logic; but it plays a big and important task. These parts, also known as oxidation catalysts, are mandatory for use in cars. Cars that do not pass emission controls are prohibited from entering the traffic. There are legal limit values ​​determined by the countries in the exhaust emission standards.

The most widely used type today is the three-way catalytic converter. It renders three different exhaust gases harmless. In other words, it renders the gases harmless with 3 different reactions. It is also possible to say that it is a chemical reaction-based filtration system. In order to be sensitive to air pollution, you should pay attention to this issue and have it checked whether it works properly in the car to be purchased.

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What is a Catalytic Converter?

Catalytic converters are used to prevent toxic gases from the fuel consumed by cars from directly mixing into the air. We can say that it is a kind of filter system of vehicles. It is located in the outlet pipe of the exhausts. They resemble a steel box. Compared to other systems in the car, they work quite simply compared to them. But their task is just as important as theirs.

Cars and their fuel are the main cause of air pollution. Especially in big cities where the population is crowded, this means serious environmental pollution. Scientists decided to do some work to stop this bad trend and designed catalytic converters. Countries have introduced a number of restrictions to reduce the amount of air pollution from vehicles.

Automobile manufacturers also made positive changes in their engine and fuel systems in order to support these studies. Catalytic converters produced for this purpose are a system that started to be used in cars in 1975 in order to reduce air pollution. In fact, the working system is quite simple compared to other systems of cars.

The so-called catalytic converter is a device that converts the harmful gases that engines give out from their exhausts to the environment, into less harmful ones. The task undertaken by catalytic converters, which has a very simple mechanism in terms of construction, is extremely important.

What Does a Catalytic Converter Do?

The catalytic converter, which can operate at temperatures between 480-650 °C, undertakes the task of minimizing the harmful effects that may occur due to the gases formed as a result of combustion in the engine as much as possible. This part, which is sometimes referred to as a catalytic converter or oxidation catalyst, contributes to preventing problems such as carbon monoxide, hydrocarbon, nitrous oxide-induced dirty fog cloud and acid rain formation as a result of the combustion of the air-fuel mixture.

Thus, an important step has been taken for the protection of the environment and human health. Today, the catalytic converter is used in both diesel and gasoline cars. Three-way converters are preferred for gasoline engines and two-way converters are preferred for diesel engines. The number of gases that the part can react with stands out as the most important factor in the name difference. Three-way catalytic converter; It renders carbon monoxide, hydrocarbons and nitrogen oxides harmless. Two-way converters interact only with carbon monoxide and hydrocarbons.

How Do Catalytic Converters Work?

Catalytic converters work as follows; The gases that emerge from the fuels consumed by the vehicles combine with the air and enter the combustion chamber. It is ensured that this air-gas mixture is at the optimum level in the combustion chamber. Otherwise, more polluted air will occur. One of the tasks of the combustion chamber is to prevent the spread of this air-gas mixture.

Three chemical reactions occur in the operation of the three-way catalytic converter, which is the most commonly used model. First, oxygen is separated from nitrous oxides, leaving nitrogen and oxygen behind. The nitrogen released here is released into the atmosphere. Oxygen is used in subsequent reactions, namely the combustion of carbon monoxide and hydrocarbons.

The first step is followed by two oxidation reactions. When oxygen and hydrocarbons and carbon monoxide are added, water and carbon dioxide remain. These are ejected from the exhaust.

Inside the catalytic converter are ceramic honeycombs with very small holes. Catalyst elements are coated on them and the contact surface of the exhaust gases with the catalyst elements is increased thanks to its structure. It is even known that if this honeycomb structure had been opened, its surface area would have been the size of a football field.

Inside the catalyst are elements that chemically react with the exhaust gases. These are listed as platinum, palladium, iridium and radium. These elements in the catalytic converter, which do not work when the car is cold, are active at high temperatures. It has a location close to the engine so that it can warm up quickly. The operating temperature is between 400 and 500 degrees Celsius.

Why Is Engine Speed ​​Important When Catalytic Converters Are Running?

One of the points to be considered here is the speed of the engine. Considering whether the engine speed is low or high, the most appropriate amount of fuel to be burned by the vehicle is calculated. Then the amount of air at the optimum level to be used is also taken into account. Afterwards, the gas and fuels are operated in the most efficient way by the computers in the vehicle.

The purpose of this is to minimize the amount of unburned harmful gas. After these processes, the gases undergo numerous reactions in Catalytic converters. After these reactions, the impurity ratios decrease to almost 0.5%. These gases, which are almost completely harmless, are now released into the atmosphere.

Are All Gases Released From Car Fuels Harmful?

Not all gases released after fuel consumption are harmful. On the contrary, some of them are gases that must be present in the atmosphere, and they are released into the atmosphere without much reaction. For example, nitrogen gas (N2) and water vapor (H2O).

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What is the Main Function of Catalytic Converters?

The main task of catalytic converters; It is to prevent the release of Carbon Monoxide (CO) and Nitrogen Oxides (NO – NO2) containing toxic substances into the atmosphere.

What Are Harmful Gases Produced While Vehicles Are Working?

Some of the toxic gases produced when vehicles are operating are:

Carbon monoxide (CO): It is one of the most dangerous toxic gases. Because it has neither color nor smell. It poisons people slowly without realizing it. It consists of the combination of incompletely burned fuels and vaporized gas particles producing smoke.

Nitrogen oxide(s): (They have 2 different forms, NO and NO2. They are also symbolized as NOx) Nitrogen oxides cause dirty fog clouds in the atmosphere and acid rain that destroys forests. It has negative effects on the nervous system of humans. They are quite dangerous for the mucous membranes in our body.

What Are Harmless Gases Produced While Vehicles Are Working?

Harmless gases from the exhaust; nitrogen, carbon dioxide gas and water vapor. Let’s take a look at their details now:

Nitrogen Gas (N2): It is also known as “Nitrogen” among the people. This Nitrogen Gas, which we call “Nitrogen”, constitutes about 78% of the air above the atmosphere. It is one of the gases that come out with the fuel consumption in cars. However, since they are harmless, they are released into the atmosphere without undergoing much processing in Catalytic converters.

Carbon Dioxide Gas (CO2): It is one of the gases produced by the combustion of car fuels. It contains a composition consisting of the formula “1 Carbon + 2 Oxygen”. Carbon dioxide is formed from the combination of 2 oxygens for each carbon atom. It is harmless when it is in reasonable amount, but it is harmful in the environment where it is more than necessary.

There should be 0.03% carbon dioxide gas in the atmosphere. More or less is harmful. One of its functions is to keep oxygen in the atmosphere. If carbon dioxide gas is less than necessary in a region; Oxygen cannot hold in that atmosphere and disperses. This leads to air pollution due to lack of oxygen in that area. If carbon dioxide is more than necessary in a region; Oxygen is excessive in that region. This, in turn, leads to air pollution due to the excess of oxygen in that area.

Water Vapor (H2O): No harm. When hydrogen and oxygen combine, a chemical bond is formed and this is how water vapor is formed. Since they are harmless, they are emitted directly from vehicles to the atmosphere without much reaction.

How Many Types of Catalysts Work Inside Catalytic Converters?

2 different types of catalytic work inside Catalytic converters: These are Reduction Catalytic and Oxidation Catalytic.

In addition, converters contain chemicals such as aluminum oxide, platinum and rhodium. The task of these chemicals is to enter into a reaction with carbon monoxide, hydrocarbons and NOx, which are found in gases and are toxic to the atmosphere. After this reaction, the toxic gases we have mentioned are converted into water vapor and carbon dioxide, which are harmless to the atmosphere.

Reduction Catalytic: Its purpose is to prevent the NOx chemical from being released into the air. Utilizes platinum and rhodium. After the NO and NO2 molecules enter the catalyst, these nitrogens are captured by the catalyte and after this process Oxygen is released. This oxygen combines with another nitrogen atom and the result is N2.

Oxidation Catalytic: In the catalytic converter, after the reduction catalytic has completed its task, it is the turn of the oxidation catalytic. Its task is to remove unburned carbon and carbon monoxide in vehicles; to react with platinum and aluminum oxides and then combine them. In this way, harmful gases; it becomes harmless or the least harmful. And then it is released into the atmosphere.

Source: https://www.carbibles.com/catalytic-converter-explained/