Wednesday, May 7, 2014
Catalytic Converter Theory
Catalytic converters are used to clean up car exhaust by burning left over fuel, not burned by the engine. They use particular properties of precious metals to catalyze the burning of hydrocarbons at temperatures below their normal ignition point. These precious metals include palladium, platinum, and rhodium.
The Facts
Catalytic converters were first installed into cars approximately 30 years ago. Prior to this, no emission regulations existed and cars put out a lot of pollutants into the atmosphere. California was the first state to begin monitoring emission levels and the first law appeared in 1968. In the early 1970s, the federal government also began to monitor and impose strict regulations on emissions. As a result, today cars are 99 percent cleaner.
Introduction
The cars exhaust is cleaner, the closer the ratio of fuel vapor to oxygen is kept to the perfect ratio of 14.7:1. This ratio is hard to maintain due to the vehicles fuel/ignition system and its range of operations. If the fuel is too rich, the emissions exit the engine through the exhaust and include chemicals such as nitrogen, carbon dioxide, and water vapor. Furthermore, the chemicals mix to form carbon monoxide, hydrocarbons and other volatile organic compounds.
Function
Catalytic converters have been developed and are installed into cars to chemically alter the emissions that leave the exhaust into more environmentally friendly chemical compounds. This is accomplished with the use of the reduction catalyst (a large surface coated with a catalyst). The surface area is located within the converter and is made as large as possible through the use of layers and honeycomb like structures. These metallic structures affect the largest possible volume of exhaust gas in the shortest period of time.
Features
The exhaust gas comes in contact with the catalyst, within the converter. The catalyst metal has a unique property of being able to break the nitrogen atom from the pollutant molecule and free the oxygen atom. As a result, nitrogen atoms bond with other nitrogen atoms on the catalyst and are later emitted into the atmosphere.This type of emission is considered clean.
Considerations
Catalytic converters only work at high temperatures because otherwise the chemical reaction discussed above will not happen. As a result, they get very hot and require a specifically designed heat shield. This heat shield protects the bottom of the car and any flammable materials underneath (on the road).
