Understanding the Functions of Catalytic Converters (Catalysts) in Automotive Exhaust Systems

Catalytic Converters AKA Catalysts – play a vital role in modern automotive exhaust systems, helping to mitigate harmful emissions emanating from internal combustion thereby reducing air pollution by converting toxic gases such as Nitrogen Oxides (NOx), Carbon Monoxide (CO) and Hydrocarbons (HC) into less harmful gases – Carbon Dioxide (CO₂), Nitrogen (N2) and then Water (H2O) which are subsequently released into the atmosphere through the exhaust pipe. These devices have become a standard component in vehicles worldwide due to increasingly stringent emission regulations. In this article, we will delve into the detailed functions of catalytic converters, exploring how they work, their importance in environmental sustainability, why they’re “sought after” and much more.

But before we progress further, in order to acquire a better understanding or obtain a vivid image in your mind about a catalytic converter works – I suggest you watch this short video:
https://www.youtube.com/watch?v=PG7NI-bAt-8

Functions of Catalytic Converters

Conversion of Harmful Pollutants: Catalytic converters primarily function to convert harmful pollutants present in vehicle exhaust gases into less harmful substances. The pollutants targeted include Nitrogen Oxides (NOx), Carbon Monoxide (CO), and Hydrocarbons (HC), all of which contribute to air pollution and have adverse effects on human health and the environment as well. Catalytic converters employ the processes of oxidation and reduction reactions to convert harmful pollutants into less harmful substances. The core components responsible for these reactions are typically platinum, palladium, and rhodium catalysts coated onto a ceramic or metallic substrate within the converter.

The platinum and palladium catalysts facilitate the oxidation of Carbon Monoxide (CO) and Hydrocarbons (HC) present in the exhaust gases, converting them into Carbon Dioxide (CO₂) and water vapour. The chemical reactions involved in these processes help to reduce the concentration of these harmful pollutants that are emitted into the atmosphere.

Reduction of Nitrogen Oxides: Rhodium catalysts within the catalytic converter facilitate the reduction of Nitrogen Oxides (NOx) present in the exhaust gases. These reactions involve the conversion of Nitrogen Oxides
(NOx) into Nitrogen (N₂) and Oxygen (O₂) molecules, which are less harmful to the environment. This process is known as Selective Catalytic Reduction (SCR).

Oxygen Storage and Release: Catalytic converters also incorporate an oxygen storage component, typically cerium oxide or other metal oxides, which helps to regulate the oxygen concentration in the exhaust gases. This oxygen storage and release mechanism enables more efficient conversion of pollutants during varying engine operating conditions, such as during cold starts or sudden accelerations.

Monitoring and Control: Modern catalytic converters are equipped with oxygen sensors and Electronic Control Units (ECUs) that monitor exhaust gas composition in real-time. Based on sensor feedback, the ECU adjusts engine parameters such as fuel-air mixture and ignition timing to optimise the catalytic converter’s performance and ultimately – minimise emissions.

Temperature Management: Catalytic converters operate most effectively within a specific temperature range. To ensure optimal performance, they often incorporate heat shields, insulation materials, and Exhaust Gas Recirculation (EGR) systems to ensure systematic temperature regulation of the exhaust gases reaching the converter.

How to tell if your Catalytic Converter is bad/malfunctioning

Catalytic converters are designed to withstand high temperatures and harsh operating conditions encountered in automotive exhaust systems. However, factors such as engine misfires, fuel contamination, and physical damage can degrade their performance over time. Regular maintenance and adherence to recommended service intervals are essential for ensuring the longevity and durability of catalytic converters.

With that being said, detecting a malfunctioning or failing catalytic converter is extremely important for maintaining vehicle performance and ensuring compliance with emission regulations. Here are several signs that can indicate that there’s a problem with a catalytic converter:

Check Engine Light (CEL) Illumination: The most common indicator of a catalytic converter issue is the illumination of the Check Engine Light on the vehicle dashboard. The onboard diagnostic system (OBD-II) in modern vehicles monitors various engine parameters, including catalytic converter efficiency. If the system detects abnormal converter performance, it will trigger the CEL instantly to alert the driver.

Decreased Engine Performance: A failing catalytic converter can lead to decreased engine performance, including reduced power output, sluggish acceleration, or difficulty starting the engine. This can result from increased exhaust backpressure caused by a partially clogged or damaged converter.

Unusual Odours: A malfunctioning catalytic converter may produce unusual odours emanating from the exhaust system. The presence of a strong sulfur-like smell (similar to that of a rotten egg) can indicate that the converter is not effectively converting hydrogen sulfide into odourless sulfur dioxide.

Excessive Exhaust Smoke: If the catalytic converter is failing due to internal damage or overheating, it may produce excessive exhaust smoke. This smoke can vary in colour, ranging from white (indicating coolant contamination), to blue (indicating oil consumption), or black (indicating excessive fuel combustion) which is quite common with public transportation vehicles here in Naija – then the owners/drivers keep on wondering why the fuel consumption of their vehicle(s) is high, but won’t fix up the “visibly” faulty exhaust system.

Rattling or Hissing Noises: Internal damage to the catalytic converter substrate or honeycomb structure can cause rattling or hissing noises during vehicle operation. These noises may become more pronounced during acceleration or when the vehicle is idling.

Inspection: During vehicle inspections or emissions testing, a malfunctioning catalytic converter can cause the vehicle to not meet up with present-day emissions standards. Elevated levels of Carbon Monoxide (CO), Hydrocarbons (HC), or Nitrogen Oxides (NOx) in the exhaust gases can indicate catalytic converter inefficiency.

Excessive Heat Under the Vehicle: A failing catalytic converter may generate excessive heat, leading to elevated temperatures in the vicinity of the exhaust system components. Carefully check for signs of heat damage, discolouration, or melting of nearby heat shields, wiring, or undercarriage components.

Fuel Efficiency Issues: In some cases, a failing catalytic converter can contribute to decreased fuel efficiency as mentioned – which can also be due to altered air-fuel ratios or increased engine load. Monitor changes in fuel consumption or unexpected drops in fuel economy, which may indicate underlying catalytic converter issues.

If you suspect a problem with your vehicle’s catalytic converter based on these signs, it is advisable to have the vehicle properly inspected by a qualified mechanic or automotive technician. They can perform diagnostic tests, such as exhaust gas analysis or catalytic converter temperature measurements, to accurately identify the root cause of the issue and recommend appropriate repairs or replacements.

Why are Catalytic Converters frequently targeted by thieves?

Precious Metal Content

Catalytic converters contain precious metals such as platinum, palladium, and rhodium, which act as catalysts in the conversion of harmful pollutants in vehicle exhaust gases. These metals have significant monetary value, particularly in the secondary market for recycling and resale. As a result, thieves target catalytic converters to extract and sell these precious metals for profit.

Accessibility and Ease of Theft

Catalytic converters are located underneath vehicles, typically attached to the exhaust system between the engine and the muffler. This positioning makes them relatively accessible to thieves, who can quickly remove them using basic hand tools such as saws, wrenches, or cordless power tools. The theft process can be completed in a matter of minutes, making catalytic converters an attractive target for opportunistic thieves, unfortunately.

Lack of Serial Numbers or Identification

Unlike other vehicle components, catalytic converters generally lack unique serial numbers or identifiable markings, making them difficult to trace once stolen. This anonymity reduces the risk of detection and apprehension for thieves, as stolen catalytic converters can be sold and resold on the market or to metal recyclers without immediate suspicion.

High Demand for Replacement

With the increasing prevalence of stricter emission regulations and the high level of theft, the demand for replacement catalytic converters remains high. Legitimate buyers often require one as soon as theirs might have been stolen or damaged and this demand in turn – creates a lucrative market for stolen catalytic converters, incentivising theft. A vicious cycle.

Vulnerability of Specific Vehicles

Certain vehicle models are more susceptible to catalytic converter theft due to factors such as ground clearance, ease of access, and the type of catalytic converter used. Vehicles equipped with larger, more valuable catalytic converters or those with hybrid powertrains containing higher concentrations of precious metals are often targeted by thieves.

Limited Security Measures

Despite efforts to deter theft, such as installing catalytic converter shields or aftermarket security devices, many vehicles still lack sufficient anti-theft measures to protect catalytic converters effectively. Thieves may exploit vulnerabilities in vehicle security systems or easily bypass existing deterrents to steal catalytic converters successfully within a short amount of time without detection.

Due to these factors, catalytic converter theft has become a prevalent crime worldwide, posing financial burdens and safety concerns for vehicle owners and communities. Therefore, there lies an urgent need to come together and put in serious efforts to combat catalytic converter theft and safeguard vehicles globally.


Hopefully, you now have a better understanding about the intricate functions of catalytic converters and their importance in modern automotive technology and emission control efforts.

In many other parts of the world, emission regulation is not clumsily responded to – so, you might want to get yours replaced or fixed if it’s malfunctioning/non-functional. Also, you may want Google VW DieselGate Scandal: https://en.wikipedia.org/wiki/Volkswagen_emissions_scandal which was mildly an interesting episode in automotive history – especially as regards emission.

https://autohub.ng/blog/understanding-the-functions-of-catalytic-converters-catalysts-in-automotive-exhaust-systems/

The mods no dey see this kind post to push go front page?

PrinceJoeWan:
The mods no dey see this kind post to push go front page?

No wahala. 😁 Dem don try push a couple go front page in the past. Wetin dey important nah awa regular readers lyk U wen we dey giv update steady...

Thanks for reading.