I got questions about catalytic converter. Can someone please help me out? Thanks in advance

1. Why is it necessarty to have additional air in exhaust before it enters the catalytic converter?

2. A catalytic converter is not effective when cold. Use the concept of activation energy to explain why.

My guess: Is it that when cold, the molecules cannot overcome the energy barrier, so that's why the catalytic converter is not effective?

My best guess is that your guess is correct. Here is a site from which you may find information about the first question. http://en.wikipedia.org/wiki/Catalytic_converter

I can't get the first one still though I had looked up the website you gave me. Can u explain it to me?

Thanks

1. The additional air in the exhaust before it enters the catalytic converter serves an important purpose. The main role of the catalytic converter is to reduce harmful emissions from the exhaust gases generated by the engine. These emissions contain pollutants such as carbon monoxide (CO), nitrogen oxides (NOx), and unburned hydrocarbons (HC). To effectively reduce these pollutants, a chemical reaction needs to take place inside the catalytic converter.

The catalytic converter contains a catalyst, typically consisting of metals like platinum, palladium, and rhodium. These metals facilitate the necessary chemical reactions. In the case of a three-way catalytic converter (used in gasoline engines), there are two main reactions involved:

- Oxidation of carbon monoxide (CO) to carbon dioxide (CO2):
2 CO + O2 → 2 CO2

- Reduction of nitrogen oxides (NOx) to nitrogen (N2) and water (H2O):
2 NOx + CO → x N2 + x/2 O2 + CO2 + H2O

Now, the additional air injected before the catalytic converter provides oxygen (O2) necessary for these reactions to occur. The oxygen combines with carbon monoxide and unburned hydrocarbons to form carbon dioxide and water, respectively. This oxidation reaction is essential to reduce the harmful emissions.

2. Your guess is partially correct. The concept of activation energy can indeed help explain why a catalytic converter is not effective when cold. Activation energy is the minimum amount of energy required for a chemical reaction to occur. In the case of the catalytic converter, the reactions necessary to reduce harmful emissions have a certain activation energy barrier that needs to be overcome.

When the catalytic converter is cold, the metals in the catalyst are not yet at their optimal operating temperature. As a result, the chemical reactions that reduce the emissions require more energy to reach the activation energy barrier. This means that when the catalytic converter is cold, the reactions are slower or may not even occur effectively.

However, once the catalytic converter reaches its optimal operating temperature (typically around 400-600°C), the catalyst heats up, allowing the reactions to happen more efficiently. The higher temperature provides the necessary energy to overcome the activation energy barrier, resulting in effective emission reduction.

It is important to note that modern vehicles are equipped with various strategies to accelerate the warm-up process of the catalytic converter, allowing it to reach its optimal operating temperature more quickly. This improves its effectiveness in reducing harmful emissions even during cold start conditions.