Autocatalyst is a part of the vehicle used for both decreasing the fuel consumption and the amount of hazardous chemical gases produced during the burning process. Autocatalysts basically provide a cleaner exhaust gas release and also include valuable metals such as platinum, palladium and rhodium in different amounts; which change as per both the brand and the model of vehicle. There are two main types of autocatalysts; ceramics and metallics. Ceramic autocatalysts are mostly preferred and used ( 95% ) all through the world.Evciler, having an experience of recycling spent autocatalysts for over 15 years, performes operations both in Turkey and in 40 different countries resulting in collection of 1500 tonnes annually. For refining and the purification of valuable metals within the catalysts, Evciler co-operates with authorized and established hi-tech refineries all over the Europe and Far East.
Catalyst is a Greek-originated word used for subtances that increase the rate of a chemical reaction by reducing the activation energy; and after which are left unchanged by the reaction. The effect of a catalyst in a reaction is known as catalysis and mainly grouped in two parts; homogeneous catalysis in which both the reactants and the catalyst is in same phase, and heterogenous catalysis in which the phases of reactants and catalyst differ. The process taking place in autocatalysts is heterogenous and is realized between metals with high atomic numbers such as palladium, osmium, rhodium, ruthenium, platinum and exhaust gases. To increase the efficiency of such a process, metal particles are decreased in size, which enables a bigger reaction surface. Beside the catalysts used in automotives, there are also industrial versions which are used mainly in petro-chemical areas.
Today there are millions of vehicles all over the roads polluting air steadily and causing a serious enviromental problem especially in big cities. As a prevention, the goverments try to apply enviromental policies including laws and regulations with the purpose of lowering the hazardous exhaust gas contents.
In order to comply with these regulations, the automobile companies constanly improve their engine and fuel systems. Such improvements resulted in the invention of the device called “autocatalyst” which pre-processes the exhaust gas filtering the hazardous parts before releasing it into the air.
To minimize the polluting agents, controlling mechanisms within the engine is established. These mechanisms include keeping fuel / air ratio at an optimum level for the combustion which is ratioed as 14:7:1 in non-diesel engines. Though such a ratio cannot be reached in many occasions in reality, discrepancies may result in a lower or a higher proportion.
The contents of exhaust gas are as follows:
- Nitrogen: Major component of air, by 78%
- Carbondioxide: The major polluting agent
- Water vapour
- Besides these three, the burning process taking place in the engine is a polluting series of reactions itself, it also produces various hazardous gases such as:
- CO ( carbon monoxide): highly toxic to the human health, odorless and colorless
- Hydrocarbons and Volatile Organic Compounds (VOCs): These gases oxidize in the presence of sunlight and produce O3, a hazardous free radical ion.
- NitrogenOxides( NOx) : Causing polluted fog layers and acid rains. They also cause irritation in throat.
- These three are the main components which are the main aim of the autocatalysts; tobe taken under control by autocatalysts and lowered in amount.
Today’s technological vehicles mostly use “three-way autocatalysts”. The three-way name comes from the three major pollutants mentioned above; of which the autocatalysts try to decrease in exhaust gases; carbon monoxides, hydrocarbons (VOCs) and NitrogenOxides (NOx). Catalytic converters use two other different types of catalysts also; the one named “limiting/decreasing catalyst” and the one called “oxidation catalyst”. In both types, the ceramic structure is covered by either platinum, rhodium or palladium. The main idea is developing a chemical reaction by using the minimum amount of catalyst and the maximum surface area to reduce the exhaust gases.