Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site akgua.UUCP 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.