5.12 What does "reactivity" of emissions mean?
Description
This article is from the Gasoline FAQ, by Bruce Hamilton with numerous contributions by others.
5.12 What does "reactivity" of emissions mean?
The traditional method of exhaust regulations was to specify the actual HC,
CO, NOx, and particulate contents. With the introduction of oxygenates and
reformulated gasolines, the volatile organic carbon (VOC) species in the
exhaust also changed. The "reactivity" refers to the ozone-forming potential
of the VOC emissions when they react with NOx, and is being introduced as a
regulatory means of ensuring that automobile emissions do actually reduce
smog formation. The ozone-forming potential of chemicals is defined as the
number of molecules of ozone formed per VOC carbon atom, and this is called
the Incremental Reactivity. Typical values ( big is bad :-) ) are [74]:
Maximum Incremental Reactivities as mg Ozone / mg VOC
carbon monoxide 0.054
alkanes methane 0.0148
ethane 0.25
propane 0.48
n-butane 1.02
olefins ethylene 7.29
propylene 9.40
1,3 butadiene 10.89
aromatics benzene 0.42
toluene 2.73
meta-xylene 8.15
1,3,5-trimethyl benzene 10.12
oxygenates methanol 0.56
ethanol 1.34
MTBE 0.62
ETBE 1.98
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