~Air Pollution~

-Introduction

-Pollutants
-Sulphur dioxide
-Nitrogen dioxide
-Carbon monoxide
-Ozone
-Particulates
-Lead

-API
-What's API?
-In Hong Kong
-Equipment
-API figures

-Photochemical Smog
-What is it?
-Problems
-Effects

-Acid Rain
-How it is formed?
-Effects

-Global warming
-Greenhouse effect
-Effects
-What can you do?

-Measures
-Part 1
-Part 2
-Part 3
-What can you do../1
-What can you do../2

Premature combustion of petrol in the car engine results in knocking which causes a loss in power of the car. To prevent knocking, lead compounds such as tetraethyllead (IV) are commonly added to the fuel. However, in the combustion process, the lead compound reacts to form volatile lead halides. This lead product can inactivate the catalysts in the catalytic converter. Thus, it is essential to use unleaded petrol in cars fitted with catalytic converter. The introduction of unleaded petrol can also reduce the amount of toxic lead compounds in the air. The use of unleaded petrol in automobiles is being enforced in some parts of the world. In Hong Kong, the use of unleaded petrol was introduced in April 1991.

Installation of catalytic converters in car exhaust systems

The nitrogen oxides, carbon monoxide and unburnt hydrocarbons present in car exhaust make it a major source of air pollution. The installation of catalytic converter in car exhaust system can help to reduce the emission of these pollutants. In the three-way catalytic converter, both oxidation and reduction take place to convert CO to CO₂, unburnt hydrocarbons to CO₂ and H₂O, and NO to N₂. The converter usually contains platinum as catalysts.

However, the catalysts are poisoned by lead compounds so that it is essential to use unleaded petrol. This is the major reason for the introduction of unleaded petrol into Hong Kong in April 1991. All new vehicles with petrol engines registered after 1st January 1992 are required by the Air Pollution Control Regulations to be equipped with catalytic converters and to operate only on unleaded petrol.