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Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!mhuxv!pdt
From: pdt@mhuxv.UUCP (tyma)
Newsgroups: net.auto
Subject: more on catalytic converters
Message-ID: <1182@mhuxv.UUCP>
Date: Wed, 8-Feb-84 09:55:46 EST
Article-I.D.: mhuxv.1182
Posted: Wed Feb  8 09:55:46 1984
Date-Received: Fri, 10-Feb-84 01:55:25 EST
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 37

Just a few facts to help confuse the discussion on
catalytic converters:

	>I think catalytic converters produce both sulfuric and
	>sulfurous oxides.

By far, more sulfur oxides are produced by the *combustion*
process within the engine.  The catalytic converter affects the
distribution of the sulfur species--some sulfur (IV) oxides are
converted to sulfur (VI) oxides, and some highly reduced
sulfur forms (like hydrogen sulfide, the rotten-egg odor) are oxidized.
The role of catalysis is to lower the energy barrier to a chemical
reaction, allowing it to proceed faster at a lower temperature.
The catalyst does this for the carbon monoxide oxidation (good),
but it also does it for the sulfur and nitrogen compounds.  Interestingly,
the (unconverted) hydrogen sulfide gas is far more toxic than
the sulfur-oxide gases.

	>Both of these combine with water in the atmosphere to produce 
	>strong acids (strong enough to change the pH of rain and lake
	>water...

ALL acids change the pH of water; that's what makes them acids.  The
acid formed by dissolving sulfur dioxide in water, sulfurous acid,
is a weak acid; that formed from sulfur trioxide, sulfuric acid,
is a strong one.

	>I don't know the exact way the sulfur in gasoline gets changed
	>into sulfur oxides...

Burning.

	>Catalytic converters work by bonding oxygen to things (oxidizing).

Not really--see above.  Catalysis is also possible for the opposite
of oxidation (reduction).