Catalytic Converter Two Way & Three Way Cat-Con.

  The Indian government introduced Bharat Stage Emission Standard Norms which regulates vehicle exhaust emitting air pollutants gases, which was based on Euro Emission Standard Norms. In the year 2001 1st April Bharat Stage II implemented for all Indian vehicles than every four years upgraded emission norm updated. All vehicles manufacturers follow the emission norm so that vehicle installed catalytic converters into the engine exhaust system to the heavy and light-duty vehicles.

Catalytic Converter 

In an automobile, the catalytic converter has been used in the vehicle emissions control system. It is located in the vehicle's exhaust system and all exhaust gas must flow through it. The catalytic converter has to convert harmful pollutants in the exhaust gases into harmless gases. The major three emissions which the vehicle's tailpipe emits exhaust gases that contain pollutants are Hydrocarbon  (HC), Carbon monoxide (CO) and Nitrogen oxides (NOx). These air pollutants are harmful to plants and animals, including human beings as well as our environment. 

In other words,  the catalyst converter cleans the exhaust reducing the pollutants to harmless substances. 

CO + HC + NOx change to   CO2 + H2O + N.

The exhaust gases flow through the catalyst converter. Catalytic inside the catalytic cause these changes. The catalyst is a material in the catalytic converter that causes a chemical change without being a part of the chemical reaction.

The catalytic converter mainly three different types of catalysts used in the vehicles: 

• Two-Way Catalytic Converter.

• Three-Way Catalytic Converter

• Duel-Bed Catalytic Converter 

Two-Way Catalytic Converter

The two-way catalytic converter treated hydrocarbons (HC) and Carbon monoxide (CO) exhaust gases. In this design, the converter is an oxidizing converter, because it oxidizes the HC and CO. To oxidise means to combine with oxygen. It contains precious metals that coat platinum and palladium with a ceramic honeycomb shape of catalytic converter inside the structure are used as oxidizing catalyst, which allows the chemical reaction to occur.

The catalyst for HC (Unburned hydrocarbon) to change CO2 (carbon monoxide) and H2O (water).

Carbon Monoxide (CO) changes (less harmful) with oxygen to become Carbon dioxide (CO2).

When the engine is running the catalysts converters get hot the heat shields around the catalytic converter shield help prevent unwanted heat transfer.

A two-way catalytic converter as an oxidation process catalyst, oxidizing carbon monoxide (CO) and hydrocarbon (HC). The two-way catalytic converter, not effectively treated with Nitrogen oxides (NOx) so then the all-new modern vehicle introduced the Three-Way Catalytic Converter especially on the spark ignition engine(petrol engine).

Three-Way Catalytic Converter 

A Three-way catalytic converter does the same function as the two-way catalytic converter but it reduces the nitrogen oxides change to nitrogen by an oxidizing and reducing process with chemicals reaction in the catalyst converter. Three-way catalyst converter treats with major three harmful exhaust gases which emit from vehicles. These include nitrogen oxides (NOx), hydrocarbon(HC) and carbon monoxide.

Construction and working of the three-way catalytic converter:

Vehicle emission catalytic converter comprises of a special combination of precious metal such as platinum, palladium and rhodium-coated with the catalyst. The rhodium help reduce the Nox to nitrogen and oxygen. Platinum and palladium are used as oxidized HC and Co catalysts in the catalytic converter.

Inside the catalyst converter, the exhaust gases pass over a large surface area coated with the catalyst. This surface is a ceramic honeycomb-shaped structure.

The whole mechanism of catalytic converter consists of the ceramic monolith of cordierite dealing with high-temperature resistance this design allows a high rate of flow of exhaust gases cordierite is used because it can withstand the high temperature in the exhaust with chemical outcomes.

The oxidation and reduction chemical reactions occur on the three-way catalytic converter.

• Unburned hydrocarbon is oxidised to CO2 (carbon dioxide) & H2O (water).

• HC+O2- change to - CO2 + H2
• H2 +O2- change to - H2O

• Carbon monoxide is oxidized to carbon dioxide (CO2).

• CO+O2 - change to - O2 + CO2

• Nitrogen oxides (NOx)  are reduced to nitrogen(N2) and oxygen (O2).

• NOx + CO - change to - H2 + CO2
• NOx + H2 - change to - H2O + N2

This catalytic converter is most effective for nowadays all-new model cars on spark-ignition engines (Petrolenginese) in the Indian auto markets. This engine withstands on Bharat Stage -VI emissions standard norm.

Duel - Bed Catalytic Converter

A dual-bed catalytic converter has two pellet beds, one over the other. An air chamber separates the two. The upper bed contains pellets coated with a three-way catalyst. This catalyst mainly reduced NOx to nitrogen and oxygen, but it also oxidized HC and CO. The lower bed serves as a two-way catalyst. When the engine warm-up secondary air from the air pump feeds the air chamber separate the beds. Air supply help for the increased oxygen level in the catalytic converter.

 Some engines using a three-way catalyst are not supplied with air from an air injection system. The design of the combustion chamber and electronic control of the fuel system produces cleaner combustion.No extra air is needed. This type of catalyst converter is very rarely used in Indian vehicles.