Why Burning of Automobile Gasoline Produce Pollutants?


Before we speak about why gasoline does not burn quickly, it’s important to understand what gasoline is.

Gasoline is a liquid formed of carbon and hydrogen which is made up of carbon chains of different lengths ranging from C7H16 through C11H24. Imagine, if we could burn gasoline as a vapor with a hot flame and plenty of oxygen, we would get almost pure carbon dioxide and water as the combustion products. However, when it comes to an automobile exhaust, we need to consider that unfortunately it contains a lot more than carbon dioxide and water; for example, pollutants like carbon monoxide, nitrogen oxides, unburned hydrocarbons are part  of it and might include some impurities like sulfur as well.

As we already said, gasoline doesn’t burn cleanly because of the arrangement of its carbon chains. Why and what are these pollutants exactly?

What is carbon monoxide (CO)? It is a colorless, odorless, and tasteless poisonous gas that is slightly less dense than air. Although it has no detectable odor, CO is often mixed with other gases that do have an odor. It is a poison that is produced when fuel is burned in an automotive engine because of incomplete combustion or from the incomplete burning of natural gas. One very important thing to know is to never let your engine run in a garage with closed doors. Carbon monoxide poisoning is a serious life threatening condition so be very cautious and always ensure that the exhaust of your car is not trapped in the garage.

Nitrogen oxides (NO) are produced from the reaction among nitrogen, oxygen and even hydrocarbons (during combustion), especially at high temperatures, formed from the heat and pressure found in a car engine.

Unburned hydrocarbons (UHC’s). UHCs are the hydrocarbons emitted after petroleum is burned in an engine. When unburned fuel is emitted from a combustor, the emission is caused by fuel avoiding the flame zones. During the combustion phase there is so little time that not all of the hydrocarbons participate in the reaction.

In my next post I will talk about technologies that make internal combustion engines better.

Stay tuned.