Gasoline-Long, somewhat opinionated but highly illuminating

[James <nyb@xxxxxxx>]

Impformative post.  However, not everything here is a bad thing, and I'm
not necessarily coming from a militant environmentalist view.  Increasing
the vapour pressure, or volatility, of the fuel does increase the amount
of VOCs directly entering the atmosphere, from filling stations for
example.  However, it also increases the amount of fuel that enters the
gas phase in the combustion chamber, meaning that more of the fuel that
goes in gets burned and fewer VOCs exit the tail-pipe.  There are far
worse things to be entering the environment than ethanol.  Finding
something that does not affect groundwater at all is very difficult and
it is frequently a matter of choosing the lesser evil.  A greater evil
would be the aromatic compounds, not miscible in water, but definitely
capable of sitting on the surface of the water table.  Aromatics are very
stable and it is difficult to break their intramolecular bonds, this is
why they increase octane (octane is higher with more stable compounds
because radical chain reactions are reduced).  However, aromatics have a
nasty habit of being carcinogenic.  If you ask what I'd rather play with
in my lab, its ethanol and methanol over benzene any day.  As for
increased water vapour from methanol and ethanol combustion, well that is
what you get if you increase the completion of your combustion.  Ideally,
what you want is complete conversion of your hydrocarbon to CO2 and H2O.
Incomplete combustion leaves you with a myriad of possible hydrocarbons
to chuck out there, far worse than water vapour.  Although, for those of
you watching the Kyoto debate, water vapour is the most offending
greenhouse gas there is.  As for TBME (proper naming under International
Union of Pure and Applied Chemistry guidelines) it has both benefits and
possible drawbacks.  It prevents the oxidation of gasoline when it is
exposed to air (in other words, acts as a gasoline preservative) and does
increase the octane value of fuel because it acts as a "radical
catcher."  It is indeed soluble in water, but conclusions about its
effect on humans are wishy washy at best.  It causes mild
gastrointestinal irritation in rodents, and there is the suggestion of
liver damage, but the evidence is far from concrete.  So what am I really
saying?  Simply that just because there are drawbacks to the current
solutions to pollution associated with gasoline, it doesn't mean that
they are worse than the original problem.

James

Crownking wrote:

> Hello Folks:
> Lots of discussion about gasoline recently.  Gasohol is produced by
> adding either methanol or ethanol to a gasoline blend stock.  This is
> done for one of two reasons: economics or product regulation.
> Ethanol is heavily subsidized by the US taxpayer and can therefore be
> used as a cheap gasoline additive; manufacturers do this to the tune
> of about 10% by volume to make gasohol.  To the extent a gallon of
> ethanol is cheaper to the manufacturer than a gallon of gasoline, the
> manufacturer benefits and pours as much of the stuff in his product
> as he can unload.  Without subsidy, ethanol is neither economic nor
> sound from an energy balance perspective.  Ethanol is popular in
> states that produce corn, for obvious reasons.
>
> Methanol can be added but since it is derived from a catalytic
> process starting with natural gas and is not subsidized, it is rarely
> seen in the marketplace in a gasohol formulation.
>
> Both methanol and ethanol suffer from environmental risk.  Ethanol is
> quite soluble in water so any leaks into the environment end up in
> the food chain.  Ethanol in high concentration is an anesthetic and
> causes numerous widely known health problems.  Methanol is known to
> cause even worse health problems.  In countries that burn straight
> methanol a problem of visibility has also been noted because of the
> much higher water content of the exhaust compared with conventional
> gasoline.  This particular problem is much worse when hydrogen is
> burned, by the way--all of the combustible material in hydrogen
> generates water upon burning.
>
> The regulatory cause for the existence of gasohol has to do with the
> requirement that reformulated fuels (RFG) be offered in certain ozone
> nonattainment areas per the Clean Air Act Amendments of 1990 (CAA).
> That bill was so outrageous it caused me to vote for Ross Perot, by
> the way. CAA requires RFG to have a certain percentage of oxygen
> contained within the molecules making up gasoline.  These sorts of
> molecules are not found in crude oil so some additive had to be
> devised to meet the oxygenate standard.  Ethanol fits the oxygen bill
> but it causes the vapor pressure of the blend to increase.  Higher
> vapor pressures lead to increased emissions of volatile organic
> compounds (VOC).  Despite current pseudoscience blaming ground level
> ozone on VOC in conjunction with nitrogen oxides, politics--in the
> form of Bob Dole's tie-breaking vote in the senate--foisted gasohol
> on us by virtue of a waiver for higher vapor pressure in gasolines
> using ethanol.  Ostensibly this is because ethanol is a renewable
> resource.  Higher vapor pressure also leads to more vapor lock in our
> beloved Imperials, by the way.  Oh, vapor pressures were required to
> be reduced for RFG during the ozone season which is roughly the late
> spring to early fall.  In addition, the aromatics content of
> gasolines had to be reduced.  Aromatics are the highest octane
> blending components available to the refiner.  You might know
> aromatics as benzene, isomers of toluene or xylene.  Naphthalene is a
> multi-ring aromatic that is marketed as moth balls; there has been a
> discussion here about using moth balls to increase octane--now you
> know why it works.   Having to pull those out of gasoline meant some
> other means of getting octane to the saleable point be developed.
>
> That brings me to methyl tert-butyl ether or MTBE.  This molecule has
> a high percentage of oxygen so it competes with ethanol as an
> oxygenate.  It also has a 100+ octane number so it is a decent
> blending component as well.  Like the alcohols, MTBE is not found in
> crude oil and has to be made.  There are a couple ways to do it--one
> starts with methanol (or natural gas) and the other robs feedstocks
> from the alkylation unit which itself produces aviation gasoline.
> Refiners have a tremendous economic incentive to produce every drop
> of aviation gasoline they can.  The costs associated with building
> MTBE production units, purchasing methanol or robbing avgas
> feedstocks make MTBE an expensive proposition.  It does have the
> advantage of not increasing the vapor pressure of the gasoline it is
> blended with.  Oil companies chose MTBE over ethanol except for those
> who chose to slop from the socialist trough of ethanol subsidies.
> Unfortunately, as always happens when the nanny state tries to
> regulate industry, MTBE is now being blamed for various health
> problems, primarily headaches and nauseau.  Consequently, we'll be
> gearing up to invest in the stupid idea of the day in order to meet
> the myriad regulations associated with producing fuels.
>
> By the way, most states tax gasoline at a rate that is at least 60%
> of the cost of the price your local service station pays for the
> gasoline.  I can publish a state by state chart of the various taxes
> if anybody is interested.  Last I looked, our price to the marketer
> was on the order of 50 cents a gallon.  That's right, 50 cents.  The
> rest is tax and dealer markup.
>
> Gasoline is the cheapest fluid on earth, bar none.
>
> __________________________________________________