Cars and the Environment | Clearing the air

Compressed natural gas, sold at this station, is one product chemical engineers are working on to reduce the air pollution generated by fossil fuel-burning vehicles. Courtesy DOE/NREL.

Cars, trucks, and buses are essential for transportation and freight delivery around the world. However, the exhaust from the gasoline- and diesel-powered engines required to propel these vehicles has been a major cause of air pollution.

Chemical engineers, working with scientists and other engineers, have helped devise ways to cost effectively reduce the amount of pollution produced by petroleum-derived, fuel-burning engines. Key developments include

  • Improved engines with more efficient fuel- and air-management systems,
  • Catalytic devices that destroy pollutants found in exhaust tailpipes, and
  • Advanced petroleum-refining techniques that produce cleaner-burning fuels.

Catalytic converters

The catalytic converter is considered one of the most important contributions to the field of air-pollution control. It is now a standard feature on vehicles everywhere. It destroys the three main pollutants found in engine exhaust.

The converter consists of a porous honeycomb ceramic base material coated with a precious metal catalyst. The honeycomb structure provides high catalyst surface area, which maximizes the contact between the catalysts and the pollutants in the hot exhaust gases.

When this novel structure was first invented, it featured two distinct chemical engineering advantages:

  • It maximized the amount of catalyst-coated surface area to which the engine exhaust may be exposed, and
  • It minimized the amount of expensive precious-metal catalyst required.

To recognize how important catalytic converters are in environmental protection, President George W. Bush awarded the inventors of the catalytic converter, the chemical engineer John Mooney and the chemist Carl Keith, with the 2002 National Medal of Technology, the highest honor given for innovation in the United States.

Cleaner-burning fuels

Another way chemical engineers help reduce automotive air pollution is through advanced petroleum-refining techniques. One example is hydrotreatment, which uses hydrogen gas and a catalyst to produce gasoline and diesel fuel with significantly lower levels of sulfur and lead.

These techniques have made it possible to produce reformulated fuels that function as effectively as earlier leaded fuels, while releasing fewer pollutants.