Catalytic Converters :: science

Catalytic Converters Introduction There are millions of cars on the road in the United States, and each one is a source of air pollution. Especially in large cities, the amount of pollution cars produce everyday is a lot. To solve those problems, many laws have been enacted restricting the amount of pollution that cars can produce. To make their cars as pollution-free as possible, automakers have made many refinements to car engines and fuel systems and have developed the catalytic converter. The catalytic converter treats the exhaust before it leaves the car, and removes a lot of the pollution. In this project, we will study catalytic converters to find out how they work, and what their effects on our planet and society are. We predict that catalytic converters can change the amounts of products that result from the burning of gasoline, and think that these devices do a good job of making cars as pollution-free as possible. How does a catalytic converter work? In order to reduce emissions, modern car engines carefully control the amount of fuel they burn. They try to keep the air-to-fuel ratio very close to the stoichiometric point, when all of the fuel will be burned using all of the oxygen in the air. For gasoline, the stoichiometric ratio is about 14.7:1. However, this fuel mixture actually varies from the ideal ratio quite a bit during driving. The main emmissions of a car engine are nitrogen gas, carbon dioxide, and water vapor. Nitrogen gas makes up about 78% of the air, and most of this gas just passes right through the car. Carbon dioxide is one of the products of combusion. The carbon in the fuel bonds with the oxygen in the air to form carbon dioxide. Water vapor is the other product of combusion. The hydrogen in the fuel bonds with the oxygen in the air to form water vapor. However, the combustion process is never perfect, so some smaller amounts of more harmful emissions are also produced in car engines. They include carbon monoxide, hydrocarbons or volatile organic compounds, and nitrogen oxides. These are the three main regulated emissions, and also the ones that catalytic converters are designed to reduce. Most modern cars are equipped with three-way catalytic converters. Three-way catalytic converters regulate the three harmful emmissions produced from car engines. The converter uses two different types of catalysts, a reduction catalyst and an oxidization catalyst. Both types consist of a ceramic structure coated with a metal catalyst.