To add interest when teaching about catalysts you can show the class different uses for them, including catalytic converters, which have helped to reduce harmful polluting gases in the atmosphere.

Catalytic converters – how catalysts help reduce air pollution

Take a few moments to think about how different your life would be without petrol or diesel engines: you wouldn’t be able to travel long distances in a car or bus, food you eat would have be grown locally and a letter could take weeks to arrive.

However, the number of vehicles on Britain’s roads is continually increasing and this has resulted in an increase in polluting gases in our atmosphere. This is a good example of how science can both improve our lives and lead to negative consequences.

The main polluting gases produced by petrol and diesel engines are carbon dioxide, carbon monoxide, sulfur dioxide and nitrogen oxides. Carbon dioxide is a greenhouse gas and an increase in its concentration in the atmosphere is linked to climate change. Sulfur dioxide and nitrogen oxides both contribute to smog and acid rain. Carbon monoxide is a toxic gas that can cause brain damage and even death. So, should we stop burning petrol and diesel, or is there a way of reducing their harmful impact?

Since 1993 all new cars in the European Union have been fitted with a catalytic converter. This device is fitted to the car exhaust and converts toxic polluting gases from the engine into less harmful ones.

Inside is a honeycomb structure covered with a thin layer of the metals rhodium and platinum. The metals are catalysts. As the hot exhaust gases pass over the metals, reactions between them take place. The two main reactions that happen are:

Nitrogen oxides –> nitrogen + oxygen

Carbon monoxide + oxygen –> carbon dioxide

You can find out more by watching this video:

Many people argue that even though the use of catalytic converters has provided cleaner air, they are not a long term solution. We need to reduce our use of petrol and diesel vehicles and think about alternatives such as electric cars.

Some questions for your students to think about:

Does the use of catalytic converters help to reduce the problem of climate change?

Catalytic converters do not help reduce the amount of carbon dioxide that cars produce, in fact they lead to an increase.

The use of the honeycomb structure increases the surface area of the metal catalysts (in fact it is around the size of two football pitches). How does this help to increase the rate of the reactions?

The catalyst speeds up the reaction as it provides a place for the reacting particles to meet and collide. Increasing the surface area increases the rate of the reaction as it provides more area for these collisions to take place.

More Resources

You students can carry out their own investigation into catalysts at home by following the instructions on Free Homework Activity: Investigating apple browning.