- Mechanism
Broken down, the catalytic converter gives its’ meaning in its’ root compounds. Catalyst, or anything (person, substance or thing) which produces a change without undergoing a permanent change itself. Convert, or to change from one thing to another thing of different structure. The chemical compound that automobiles emit is Oxygen (O2) combined with carbon monoxide (CO) and unburned hydrocarbons (HC). When filtered through the catalytic converter they produce a safer carbon dioxide (CO2) and water (H2O). This was called a “two-way” converter. Later in the 1980’s the two-way became obsolete as a three-way converter also reduced oxides of nitrogen (NOx). A French mechanical engineer, Eugene Houdrey, moved to the United States in 1930. At the time he became interested in the smog study publications in Los Angeles and wondered what role the smokestacks and automobile exhaust were playing in the production of these toxins in the atmosphere. He began with forklifts early on that used low grade and unleaded gasoline. Later in his research, the catalytic converter became developed into primarily gasoline engines. Specifically those in automobiles. As emissions became a larger concern in the United States, these emission controlling devices were put into mass production in 1973. Into the 80’s Canada and the United States primarily required automobiles to have catalytic converters to pass their inspections and reduce harmful toxins into the environment with other countries gradually enforcing emissions regulation steadily through the turn of the century. Emissions are regulated by the Environmental Protection Agency (EPA) and mandatory use of the oxidation-reduction catalytic converters has been enforced since 1975.
- Construction
In order to maintain the aforementioned structural integrity of the device while exacerbating the chemical reaction, the catalytic converter itself is made up of several precious metals. These strong metals are able to withstand very high temperatures without heavy damage or corrosion. 4 components are integral to the construction of catalytic converters beginning with the support or substrate. These have a large surface area for use to provide very high heat resistance. The wash coat is a conductor for the components to be carried over that surface area using a rough surface thus further increasing surface area. The use of aluminum oxide, silicon dioxide, titanium dioxide or a mixture of silica and alumina suspend the compounds in the wash coat before progressing to the core of the converter. Next, two oxides (ceria or ceria-zirconia) provide extra oxygen stores to maximize the clean output. Lastly, the core, the catalyst, is this foundation of precious metals. The best active converter is platinum, however, it is not always the best choice due to cost and reactions less desirable in the oxidation process. Rhodium is the other most common metal used in catalytic converters, of iron, manganese, nickel, and cerium frequently implemented as well. Each metal has its own set of desired and undesired reactions at various temperatures based on the fuel being burned.
- Common Applications
In everyday life, catalytic converters are found primarily in our automobiles but can also be found in heavy construction equipment, passenger trains (locomotives), motorcycles, trucks, and generators. Any systems where combustion of accellerant fuels the movement and power of an engine. Most vehicles since 1975 have been equipped with catalytic converters in North America. Globally, countries are seeing the effects of toxins on the air quality as traffic increases. High traffic areas suffer such toxicities as poisoning to humans and animals, acid rain, ecosystem damage as well as structural damage to buildings. This makes the modest cost of the catalytic converter worth its weight in precious metals. By the same measure, catalytic converters should be cleaned up to four times a year to maximize efficiency and removal of toxic buildups. For more information on catalytic converter prices, ensure you shop around.
