Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
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Path: utzoo!watmath!clyde!akgua!dlp
From: dlp@akgua.UUCP (D.L. Philen [Dan])
Newsgroups: net.auto
Subject: Catalytic Converters
Message-ID: <553@akgua.UUCP>
Date: Wed, 8-Feb-84 11:06:27 EST
Article-I.D.: akgua.553
Posted: Wed Feb  8 11:06:27 1984
Date-Received: Fri, 10-Feb-84 01:53:51 EST
Organization: AT&T Technologies, Atlanta
Lines: 48


	    On the subject of catalytic	converters, let	me add a
       little more confusion.  First, the use of catalytic
       converters is not the cause of acid rain.  Acid rain is
       occurring because the EPA mandated lower	stack emissions
       from such companies as power plants.  Since most	ground
       sampling	is done	near the stack,	one solution to	lower
       emissions is to increase	the length of the stack.  Power
       plant stacks of 200-500 feet are	not uncommon.  This has	the
       effect of injecting the power plant emissions (sulfur
       oxides) higher into the troposphere.  In	the troposphere
       there is	a mixing layer.	 Air above this	layer does not mix
       (in general) with air below.  This sulfur oxides	injected
       high into the troposphere combine with rain to form acid
       rain.  (The mixing layer	is generally from 500 to 3000 feet.
       The next	time you fly notice when you take off that a few
       minutes after takeoff you leave a layer of general haze and
       enter an	area of	clearer	air.  This is the mixing layer.
       Also on a day with many fluffy clouds, the bottom of the
       cloud layer is near the mixing zone.  When flying this is
       also marked by a	region of increased turbulence.)

	    On catalytic converters they convert the nitrogen
       oxides (NO^2) to	nitrogen and compounds which can not be
       photochemically reacted to produce smog.	 It is to reduce
       the nitrogen oxides (they produce smog) that the	converters
       were originally proposed.  As a result of this massive
       oxidation, one also oxidizes the	sulfur.	 Since you don't
       produce free sulfur, you	produce	sulfur oxides.	The oxides
       do not mix with the upper atmosphere to produce acid rain,
       but do tend to be corrosive in their own	right.

	    As an added	"oh my gosh!" catalytic	converters also
       produce HCN (hydrogen cyanide).	As we all remember from	our
       basic chemistry,	HCN is produced	in a reducing condition	by
       passing a hydrocarbon, and nitrogen, over a platinum
       catalyst.  Reducing conditions are EASILY encountered in
       automobiles by 1) carb out of tune ie. too little air 2)
       engine not warmed up ie.	too much fuel or 3) going down hill
       ie. engine warm,	too much fuel and too little air.  The
       rotten eggs smell encountered is	usually	from S0^2 and all
       the H2S should be oxidized to the oxide,	unless of course
       the engine is running the converter in a	reducing condition.
       This, by	the way, is the	commercial method for producing
       HCN.  Add to all	this mess that trace amounts of	lead poison
       the platinum catalyst and you wonder if the catalysts are
       worth all the trouble.