trough@ihuxa.UUCP (Chris Scussel) (02/02/84)
Several recent net articles have claimed that catalytic converters increase sulfur compound emissions from autos. What happened to the sulfur before the converters? Do the converters catalyze the production of "worse" sulfur compounds? If we're talking about acid rain, then it would seem that sulfuric/ous oxides are important, and the "ous" doesn't need a catalyst to change to "ic". What gives?
sebb@pyuxss.UUCP (S Badian) (02/03/84)
I think catalytic converters produce both sulfuric and sulfurous oxides. Both of these combine with water in the atmos- phere to produce strong acids(strong enough to change the pH of rain and lake water so that the wildlife notices; they're pro- bably pretty sensitive. I know trout are.) I don't know the exact way the sulfur in gasoline gets changed into sulfur oxides but if I had to venture a guess I would say it's because of the high temperatures in catalytic converters. Are there any chemists out there to shed some light on the matter? It's been a while since college chemistry. Sharon Badian
jrt@hou5g.UUCP (Jaime Tormos) (02/03/84)
Is that why my car smells of rotten eggs once in a while? It seems to come from the bottom of the car, when it is just warming up, or at times when it is real hot. For a while I thought it was the undercoating burning off the exhaust system. (** FRODO **)
glass@houxf.UUCP (K.GLASS) (02/03/84)
Often, when I stop my car, I notice a very distinct sulfur smell, especially after I've driven it at high engine revs. Whew, it's bad at times.... Ken Glass houxf!glass
stekas@hou2g.UUCP (J.STEKAS) (02/03/84)
Since converters can't create sulfer, how can they increase sulfur
emissions? They probably affect the mix of sulfur compounds coming
out the tailpipe, which sulpher emissions are the worst? Is H S
2
worse than SO ?
2
Jimchris@umcp-cs.UUCP (02/06/84)
[Begin EQN convention: delim($$)]
Catalytic converters work by bonding oxygen to things (oxidizing).
This helps reduce unburned and partially burned carbon emissions
by converting $C$ and $CO$ to $CO sub 2$ -- carbon dioxide.
Unfortunately it also changes $S$ to $SO$ and $SO sub 2$ and $N$
to $NO$ and $NO sub 2$. The sulfur and nitogen oxides combine with
water to form sulfuric acid and nitric acid (and -ous versions too,
but let's not worry about them for the moment).
The source for the sulfur is impurities in the gasoline. The
nitrogen is already present in the atmosphere as $N sub 2$; while
$N sub 2$ is pretty stable, it does get broken up occasionally.
The basic results are that catalytic converters cut down on smog
and carbon monoxide at the expense of an increase in sulfur dioxide
and nitrogen dioxide (and thus acid rain).
I don't have enough information to actually compute the smog and
acid-rain differences between "with catalytic converter" and
"without". Also, I don't know enough about catalytic reactions
and how they affect things. Any takers?
--
In-Real-Life: Chris Torek, Univ of MD Comp Sci
UUCP: {seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet: chris@umcp-cs ARPA: chris.umcp-cs@CSNet-Relaymat@hou5d.UUCP (02/07/84)
It seems to me that if the sulfur is being dumped into the atmosphere, it will eventually be oxidized into some nasty substance. The only question is whether it is in this nasty form when it comes out of the tailpipe, or if it gets nto the upper atmosphere before it is converted. In the former case you rot out roadways and curbstone. In the latter you poison Canadian lakes. And we breathe it either way. Ya pays yer money an ya takes yer cherss. Mark Terribile Duke Of deNet