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From: (Bruce Hamilton)
Subject: Re: catalytic converter is a conspiracy
Date: Sat, 21 Nov 1998 18:09:15 GMT

"Richard Flynn" <> wrote:

><some stuff snipped>
>>> I notice you didn't deny my remark that unleaded fuel
>>> contains benzine

Given that, by definition, benzine is:-
" Benzine ( ligroin ) was a saturated hydrocarbon fraction
  that boiled between 20C and 135C. Gasoline/petrol fractions
  are still called benzine by some older people."
  [ extracted from the Sci.chem FAQ ]
then virtually all spark ignition fuels on modern engines
contain benzine, and leaded fuels probably contained more
than unleaded...

>>Some of it does.  US unleaded fuel contains little to none.
> Actually, unless there has been a major change in the
> formulation of unleaded gasoline, benzene makes up 2-3
> percent of unleaded gas.

Actually, benzene content has been regulated in most parts
of the world, and it's not uncommon for some leaded fuels
to have higher benzene levels that the unleaded. The US
set an overall maximum limit of 1.0 volume% ( 0.95 volume%
period average, with 1.3 volume% of benzene as the absolute
maximum ) in 1995.

Some countries still have limits of 5% volume for benzene
for both leaded and unleaded. Many leaded gasolines had
2-4 volume% of benzene, and unleaded gasolines may have more
( 3-5 volume% ) if the regulations allow. Over the last
decade many countries have moved the Benzene maximum to
3.0 volume %, and it continues to drift down as new fuel
regulations are introduced. Most of the anti-benzene
hysteria arises from the propaganda put out by the alkyl
lead producers - such as Associated Octel.

> The aromatics (benzene, toluene, ethyl benzene and the
> xylenes) make up about 10-15 percent by volume.

For many unleaded fuels, the total aromatics ( not just
the BTEX above ) can climb to 50% if oxygenates aren't
used and the regulations allow. Leaded fuels used to
have around 30-45% aromatics. In the USA, some gasoline
regulations indirectly control the aromatics to the high
20s %, which is lower than leaded gasolines.

The Gasoline FAQ covers most of the informtion necessary
to reassure the original poster that exhaust catalytic
converters aren't a conspiracy, and they are good for
both humanity and the environment. It also covers the
chemical differences, the effects on older cars, and
the toxicity issues of moving from leaded to unleaded.

The FAQ should be available at any good Usenet FAQ archive
site in the rec/autos/tech directory.

[ Followups set to only ]

          Bruce Hamilton

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