Editorial Feature

What Materials are Used in Catalytic Converters?

A catalytic converter is a vehicle emissions control device that is used to convert toxic byproducts of combustion (occurring in the exhaust of an internal combustion engine) to less toxic substances by performing catalyzed chemical reactions. The reactions tend to vary depending on the type of catalyst installed. What materials are used in catalytic converters?

Image Credit: Setta Sornnoi/Shutterstock.com

This vehicle emission control device was invented by Eugene Houdry, a French mechanical engineer involved with catalytic oil refining. In 1973, former General Motors President Robert Stempel decided to begin their implementation in automobiles.

Since then, many scientists have been working on the development of the catalytic converter and as of 2010, they are mandatory on all cars in the US.

Although these devices are primarily used in exhaust systems in automobiles, they are also modified and used on trucks, buses, forklifts, mining equipment, generator sets, locomotives, motorcycles, airplanes, and other engine-fitted devices. They are also used on some wood stoves to control emissions.IFrame

What Materials are Used in Catalytic Converters?

The catalytic converter is made up of several materials. The catalyst core or substrate varies according to the vehicle. For example, when these devices are used in automobiles, the core is usually a ceramic monolith with a honeycomb structure.

When manufactured in large quantities, ceramic cores can be inexpensive. Metallic foil monoliths are made of an iron-chromium-aluminum combination and are used in some applications. Metallic cores are less expensive when manufactured for use in small production runs, such as in sportscars in which low back pressure and reliability under constant high load are essential. Both these materials are designed to provide a high surface area to support the catalyst washcoat.

The catalyst washcoat is a carrier for the catalytic converter materials, which is used to disperse the materials over a high surface area. Titanium dioxide, aluminum oxide, silicon dioxide, or a combination of silica and alumina can be used. The catalytic materials are suspended in the washcoat before application to the core. Washcoat materials have rough, irregular surfaces to increase surface area, which helps to maximize the catalytically active surface available to react with the engine exhaust.

The catalyst used in the converter is mostly a precious metal such as platinum, palladium, and rhodium. Platinum is used as a reduction catalyst and as an oxidation catalyst. Although platinum is a very active catalyst and widely used, it is very expensive and not suitable for all applications. Rhodium is used as a reduction catalyst, while palladium is used as an oxidation catalyst.

In some cases, cerium, iron, manganese, and nickel are also used. However, some companies forbid the use of some of these.

Different Variations of Catalytic Converter Materials

The key types of catalytic converters are listed below with a brief introduction:

  • Two-way oxidation - The two-way oxidation instruments performs the two simultaneous tasks of oxidation of carbon monoxide to carbon dioxide and oxidation of hydrocarbons to carbon dioxide and water. This converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. However, this is no longer used in the U.S. and Canada due to their inability to control oxides of nitrogen.
  • Three-way oxidation-reduction - The three-way oxidation-reduction devices are used in vehicle emission control systems in most parts of the world including the U.S. and Canada. The strict vehicle emission regulations have almost made it mandatory to use three-way converters on gasoline-powered vehicles. These converters have come to be recognized as one of the most important inventions in the history of automobiles. These perform three simultaneous tasks, namely, the reduction of nitrogen oxides to nitrogen and oxygen, oxidation of carbon monoxide to carbon dioxide, and oxidation of unburnt hydrocarbons to carbon dioxide and water.
  • Diesel Oxidation Catalyst (DOC) - DOC's are most commonly used for compression ignition such as in diesel engines. This device uses oxygen in the exhaust gas stream to convert carbon monoxide to carbon dioxide and hydrocarbons to water and carbon dioxide. These converters are known to perform at 90% efficiency, wherein they manage to remove diesel odor and reduce visible particulates.

Environmental Impact

The catalytic converter was specifically invented to decrease harmful pollution caused by gases produced from the combustion of hydrocarbon-based fossil fuels in cars. Studies reveal that these devices can decrease hydrocarbon emissions by about almost 87%, carbon monoxide by 85%, and nitrous oxide by 62% during the expected life of a vehicle.

More from AZoM: How are Graphene Batteries Made?

References and Further Reading 

  • The 3-Way Catalytic Converter - arb

Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.

G.P. Thomas

Written by

G.P. Thomas

Gary graduated from the University of Manchester with a first-class honours degree in Geochemistry and a Masters in Earth Sciences. After working in the Australian mining industry, Gary decided to hang up his geology boots and turn his hand to writing. When he isn't developing topical and informative content, Gary can usually be found playing his beloved guitar, or watching Aston Villa FC snatch defeat from the jaws of victory.


Please use one of the following formats to cite this article in your essay, paper or report:

  • APA

    Thomas, G.P.. (2022, October 26). What Materials are Used in Catalytic Converters?. AZoM. Retrieved on February 24, 2024 from https://www.azom.com/article.aspx?ArticleID=8094.

  • MLA

    Thomas, G.P.. "What Materials are Used in Catalytic Converters?". AZoM. 24 February 2024. <https://www.azom.com/article.aspx?ArticleID=8094>.

  • Chicago

    Thomas, G.P.. "What Materials are Used in Catalytic Converters?". AZoM. https://www.azom.com/article.aspx?ArticleID=8094. (accessed February 24, 2024).

  • Harvard

    Thomas, G.P.. 2022. What Materials are Used in Catalytic Converters?. AZoM, viewed 24 February 2024, https://www.azom.com/article.aspx?ArticleID=8094.


  1. Otto Nicator Otto Nicator United States says:

    I need a catalytic converter that is aflame and which I can reroute the gases produced from it's burning, to fuel my vehicle. Like a Worm.

  2. Joel Galvão Joel Galvão Brazil says:

    Hi, what are the advantages in use of talc in the composition of automotive catalysts?

  3. Edna Elliott Edna Elliott Canada says:

    yes I no beads are not used any more , but is it true they used 90% more palladium back then because no one new much about palladium back then and cheaper.

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

Tell Us What You Think

Do you have a review, update or anything you would like to add to this article?

Leave your feedback
Your comment type
Azthena logo

AZoM.com powered by Azthena AI

Your AI Assistant finding answers from trusted AZoM content

Azthena logo with the word Azthena

Your AI Powered Scientific Assistant

Hi, I'm Azthena, you can trust me to find commercial scientific answers from AZoNetwork.com.

A few things you need to know before we start. Please read and accept to continue.

  • Use of “Azthena” is subject to the terms and conditions of use as set out by OpenAI.
  • Content provided on any AZoNetwork sites are subject to the site Terms & Conditions and Privacy Policy.
  • Large Language Models can make mistakes. Consider checking important information.

Great. Ask your question.

While we only use edited and approved content for Azthena answers, it may on occasions provide incorrect responses. Please confirm any data provided with the related suppliers or authors. We do not provide medical advice, if you search for medical information you must always consult a medical professional before acting on any information provided.

Your questions, but not your email details will be shared with OpenAI and retained for 30 days in accordance with their privacy principles.

Please do not ask questions that use sensitive or confidential information.

Read the full Terms & Conditions.