Any combustion car needs to reject the particles being emitted by the engine. These particles are released into nature through an exhaust system. These rejected particles are harmful to the environment and to health. This is how we had the idea of creating a catalyst, also called a catalytic converter (not to be confused with the exhaust), which serves to significantly reduce polluting emissions.
The first prototypes of catalytic converters made their appearance in France at the end of the 19th century. They will obviously evolve over time, but the primary function remains the same. If its interest was taken into consideration much later, we witnessed a boom in the 1970s and became compulsory for the first time in the United States of America in 1975, while in Europe it was not until 1988 with the arrival of new anti-pollution standards starting with the Euro0 standard intended only for heavy goods vehicles and public transport.
It was not until 1992 that the first standards intended for light vehicles were promulgated with the Euro1 standard intended for diesel engines, European legislation was made more severe every 5 years or so with new even stricter standards. The standards differ between the different types of engines. The Euro 2 standard, which entered into force in 1996 for indirect injection engines developed mainly by the engine manufacturer Mitsubishi (even if the invention dates back to the 1920s and is the invention of the Frenchman Georges Regembeau), it is in this period that we see the disappearance of leaded petrol in favor of unleaded petrol. There were no regulations for gasoline engines before the arrival of the Euro 3 standard. As of today we have arrived, for light vehicles in Europe, at the Euro6d standard since 2020 and in the USA, manufacturers will be able to breathe, because the standards limiting the pollution of cars which were to come into force in 2022 will be reviewed and made more flexible, nicknamed "CAFE" (Corporate Average Fuel Economy), the standards for the period 2022-2025 had been set by Barack Obama's previous Democratic administration shortly before Republican Donald Trump arrived at the White House. They provided for gradual increases in vehicle range to reach a target of 54.5 miles per gallon of gasoline (4.32 liters per hundred kilometers) by 2025. In the rest of the world there are also other standards. relating to each country, the least structured countries using the most used standards or having no standards in this area.
It should also be noted that anti-pollution standards are a primordial issue both in politics for states and in strategic terms for car manufacturers. We sometimes witness real wars and deceptions like the scandal of "Dieselgate" incriminating VW.
But how does a catalyst work?
The exhaust catalyst is a component of the exhaust system that consists of a stainless steel shell and a ceramic core (also known as a honeycomb) impregnated with precious metals such as platinum or rhodium.
In the automotive sector, catalytic exhausts oxidize certain toxic residues from the combustion reaction of the air-gasoline mixture. Enough to reduce the release of these harmful gases - such as carbon monoxide (CO) - into the atmosphere.
For a diesel engine, the exhaust catalyst converts carbon monoxide and hydrocarbons into carbon dioxide and water (more and more it is connected to a DPF particle filter). On the other hand, for a gasoline engine, the catalyst quite simply transforms carbon monoxide and nitrogen dioxide into non-polluting substance. The catalytic converter is efficient at high temperatures, which is why it is placed very close to the engine to heat up quickly and reach a good operating temperature. The catalyst must be changed every 100,000 to 120,000 kilometers or so on pain of ending up with a faulty component that no longer meets the standards in force. Indeed, a vehicle with an exhaust catalyst in poor condition can adversely affect the air quality due to an excessively high level of pollution. If there is a failure, you will see strange smoke coming out of the exhaust or a metallic noise coming from the exhaust system are the first signs of a failing catalyst. The risks involved: A faulty exhaust line generates an increased loss of engine power, an increase in sound volume as well as an increase in fuel consumption.
Catalyzed pots have thus made it possible to reduce the emissions of 3 pollutants: carbon monoxide (CO, toxic), nitrogen oxides (precursors of ozone) as well as unburned hydrocarbons (pollutants and sometimes mutagenic and carcinogenic), and indirectly lead (by promoting unleaded fuels).
However, despite the increasingly satisfactory results of new engines associated with catalysts, the future will give way to another even less polluting technology, namely the electric car.