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 Term Paper on Catalytic Converter In Automobile
... fuel catalytic converter solved the problem that the three-way catalytic converter has in creating secondary pollution, the magnetic fuel catalytic converter ... located upstream of the catalytic converter acts as an instrument that detects the amount of oxygen that exists. ... Oxidation Catalysis-Two-Way catalysis The earlier catalytic converters used commercially on cars during 1975-1980 were two-way, [ ...
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. Since catalyst is very expensive, manufacturers try to create a structure that exposes the maximum surface area of catalyst to the exhaust stream, while also minimizing the amount of catalyst required. There are two main types of structures used in catalytic converters, honeycomb and ceramic beads. Most cars today use a honeycomb structure.
The reduction catalyst is the first stage of the catalytic converter. It uses platinum and rhodium to help reduce the nitrogen oxide emissions. When a nitrogen oxide or nitrogen dioxide molecule contacts the catalyst, the catalyst rips the nitrogen atom out of the molecule and holds on to it, isolating and freeing the oxygen, forming O2. The nitrogen atoms bond with other nitrogen atoms that are also stuck to the catalyst, forming N2.
The oxidation catalyst is the second stage of the catalytic converter. It reduces the unburned hydrocarbons and carbon monoxide by burning them over a platinum and palladium catalyst. This catalyst helps to reduce the carbon monoxide and hydrocarbons with the remaining oxygen in the exhaust gas. It combines carbon monoxide with oxygen to form carbon dioxide. The oxygen comes from the control system that monitors the exhaust stream, and uses this information to control the fuel injection system. There is an oxygen sensor mounted upstream of the catalytic converter that tells the engine how much oxygen is in the exhaust. The engine can increase or decrease the amount of oxygen in the exhaust by adjusting the air-to-fuel ratio. This allows the engine to make sure that it is running at close to the stoichiometric ratio, and also makes sure that there is enough oxygen in the exhaust to allow the oxidization catalyst to burn the unburned hydrocarbons and carbon monoxide.
The Term Paper on Microporosity And Surface Functionality Of Activated Carbon
Abstract Activated carbons have been prepared from jute stick by both chemical and physical activation methods using ZnCl2 and steam, respectively. The activated carbons were characterized by evaluating surface area, iodine number, pore size distribution, surface functional groups and surface textural properties. Based on the analysis, the activated carbon prepared by chemical activation method, ...
