Catalytic Converters vs Greenhouse Gases

[OldCowboy]

All of a sudden, folks seem to think that CATs have something to do with greenhouse gases, even though CATs have been around for over 40 years and greenhouse gasses have only been of note outside of certain communities for a decade or so.

Those of you who have been around long enough will remember the terrible smog problems large cities had by the late 1960s. This smog was caused by increased concentrations of CO, NO, unburned hydrocarbons, and sulfur dioxide. The sulfur dioxide could be controlled by reducing the amount of sulfur in motor fuels, but the other components required something different. As it turned out, a catalytic converter, in the absence of tetraethyl lead, could convert CO to CO2, NO to N + O2, and unburned hydrocarbons to CO2 + H2O. The unmitigated success of unleaded gasoline and CATs can be seen by the dramatic reducion in smog. So much so that it is rare to hear of smog in North America today.

The biggest contribution of CATs to reducing greenhouse gases is the conversion of nitrous oxide to nitrogen + oxygen by the use of 3-way CATs. Since 3-way CATs were introduced, they have effectively halved motor vehicle nitrous oxide production.

Again, however, we need to look at the timeline for the introducton of 3-way CATs. They were introduced in 1981 and the justification for their implemintation had nothing to do with greenhouse gases. The issue at the time was acid rain and ozone depletion, which were significant problems caused by nitrous oxide.

[Bob Denman]

Thank you, for this explanation.
If I'm understanding this correctly; the converters are turning CO (The SmogMaker), into CO2 (Greenhouse Gas).
Is that correct?

[jcthorne]

CO2 is also a greenhouse gas, just does not cause localize smog at low elevations in the atmosphere. The Cat simply exchanges emitting one pollutant for another. The only way to reduce greenhouse gas emissions is by the reduction of quantity of hydrocarbon fuel burned. How we do that seems to always turn into a political discussion not appropriate here.

[Chupaca]

thanks for the info. Do remember the sequence of events. Rest of the world did not follow too well...