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that Make a Difference! Green
Go'Fer Distributing
Green Go'Fer Juice Soltron®
Enzyme Fuel Treatment What
is Gasoline?
We
put it into our cars and trucks every day - but what is
is exactly? What is Gasoline?
Gasoline
(or petrol) is a petroleum-derived liquid mixture consisting
primarily of hydrocarbons, used as fuel in internal combustion
engines.
Before internal combustion engines were invented in the
mid-1800s, gasoline was sold in small bottles as a treatment
against lice and their eggs. At that time, the word "Petrol"
was a trade name. This treatment method is no longer common
because of the inherent fire hazard and the risk of dermatitis.
The
word "gasolene" was coined in 1865 from the word gas and
the chemical suffix -ine/-ene. The modern spelling was first
used in 1871. The shortened form "gas" was first recorded
in American English in 1905.
Gasoline originally referred to any liquid used as the fuel
for a gasoline-powered engine, other than diesel fuel or
liquefied gas. Methanol racing fuel would have been classed
as a type of gasoline. The word "petrol" was first used
in reference to the refined substance as early as 1892 (it
previously referred to unrefined petroleum), and was registered
as a trade name by English wholesaler Carless, Capel & Leonard.
Gasoline
is produced in oil refineries. Material that is separated
from crude oil via distillation, called natural gasoline,
does not meet the required specifications for modern engines
(in particular octane rating; see below), but will form
part of the blend. The various refinery streams blended
together to make gasoline all have different characteristics.
Some
important streams are:
· Reformate, produced in a catalytic reformer with a high
octane rating and high aromatic content, and very low olefins
(alkenes).
· Cat Cracked Gasoline or Cat Cracked Naphtha, produced
from a catalytic cracker, with a moderate octane rating,
high olefins (alkene) content, and moderate aromatics level.
Here, "cat" is short for "catalyst".
· Hydrocrackate (Heavy, Mid, and Light), produced from a
hydrocracker, with medium to low octane rating and moderate
aromatic levels.
· Natural Gasoline (has very many names), directly from
crude oil with low octane rating, low aromatics (depending
on the crude oil), some naphthenes (cycloalkanes) and zero
olefins (alkenes).
· Alkylate, produced in an alkylation unit, with a high
octane rating and which is pure paraffin (alkane), mainly
branched chains.
· Isomerate (various names) which is made by isomerising
Natural Gasoline to increase its octane rating and is very
low in aromatics.
(The terms used here are not always the correct chemical
terms. Typically they are old fashioned, but they are the
terms normally used in the oil industry. The exact terminology
for these streams varies by oil company and by country.)
Overall a typical gasoline is predominantly a mixture of
paraffins (alkanes), naphthenes (cycloalkanes), aromatics
and olefins (alkenes).
The
exact ratios can depend on
· the oil refinery that makes the gasoline, as not all
refineries have the same set of processing units.
· the crude oil used by the refinery on a particular day.
· the grade of gasoline, in particular the octane rating.
Currently
many countries set tight limits on gasoline aromatics in
general, benzene in particular, and olefins (alkene) content.
This is increasing the demand for high octane pure paraffin
(alkane) components, such as alkylate, and is forcing refineries
to add processing units to reduce the benzene content.
Gasoline
can also contain some other organic compounds: such as organic
ethers (MTBE no longer allowed by the EPA ), plus small
levels of contaminants, in particular sulfur compounds such
as disulfides and thiophenes. Some contaminants, in particular
thiols and hydrogen sulfide, must be removed because they
cause corrosion in engines.
The
bulk of a typical gasoline consists of hydrocarbons with
between 5 (Pentane) and 12 (Duodecane) carbon atoms per
molecule.
The
Octane Rating Unveiled
Octane
is measured relative to a mixture of isooctane (2,2,4-trimethylpentane,
an isomer of octane) and n-heptane. An 87-octane gasoline,
for example, has the same knock resistance as a mixture
of 87 vol-% isooctane and 13 vol-% n-heptane. This does
not mean, however, that the gasoline actually should contain
these chemicals in these proportions. It simply means that
it has the same autoignition resistance as the described
mixture. A high tendency to autoignite, or low octane rating,
is undesirable in a gasoline engine but desirable in a diesel
engine. The standard for the combustion quality of diesel
fuel is the cetane number. A diesel fuel with a high cetane
number has a high tendency to autoignite, as is preferrednce
there is no ignition spark in a diesel engine.
Fuel
Additives
Fuel additives designed to improve the performance
of vehicles, equipment, vessels, and other sorts of engines
have been around for a long time. Even at the gas pump,
we find that the petroleum companies enhance the composition
of the gasoline and diesel fuel with various other chemicals.
These chemicals include such compound classes as detergents,
dispersants, lubricants, and performance enhancing compounds.
Some of these additives and conditioners are used seasonally
in order to counteract the effects of cold weather. This
is especially true with diesel fuel.
Lead
The mixture known as gasoline, when used
in high compression internal combustion engines, has a
tendency to ignite early (pre-ignition or detonation)
causing a damaging "engine knocking" (also called "pinging")
noise. Early research into this effect was led by A.H.
Gibson and Harry Ricardo in England and Thomas Midgley
and Thomas Boyd in the United States. The discovery that
lead additives modified this behavior led to the widespread
adoption of the practice in the 1920s and therefore more
powerful higher compression engines. The most popular
additive was tetra-ethyl lead. However, with the recognition
of the environmental and health damage caused by the lead,
and the incompatibility of lead with catalytic converters
found on virtually all automobiles since 1975, this practice
began to wane in the 1980s.
Most countries are phasing out leaded fuel;
different additives have replaced the lead compounds.
The most popular additives include aromatic hydrocarbons,
ethers and alcohol (usually ethanol or methanol).
In the U.S., where lead was blended with
gasoline, primarily to boost octane levels, since the
early 1920s, standards to phase out leaded gasoline were
first implemented in 1973. In 1995, leaded fuel accounted
for only 0.6 % of total gasoline sales and less than 2,000
tons of lead per year. From January 1, 1996, the Clean
Air Act banned the sale of leaded fuel for use in on-road
vehicles. Possession and use of leaded petrol in a regular
on-road vehicle now carries a maximum $10,000 fine in
the United States. However, fuel containing lead may continue
to be sold for off-road uses, including aircraft, racing
cars, farm equipment, and marine engines until 2008. The
ban on leaded gasoline was presumed to lower levels of
lead in a person's bloodstream and led to thousands of
tons of lead being removed from the air. A side effect
of the lead additives was protection of the valve seats
from erosion. Many classic cars' engines have needed modification
to use lead-free fuels since leaded fuels became unavailable.
However, "Lead substitute" products are also produced
and can sometimes be found at auto parts stores.
Gasoline, as delivered at the pump, also
contains additives to reduce internal engine carbon buildups,
improve combustion, and to allow easier starting in cold
climates.
MMT
Methylcyclopentadienyl manganese tricarbonyl
(MMT) has been used for many years in Canada and recently
in Australia to boost octane. It also helps old cars designed
for leaded fuel run on unleaded fuel without need for
additives to prevent valve problems. There are currently
ongoing debates as to whether or not MMT is harmful to
the environment and toxic to humans. However, US Federal
sources state that MMT is suspected to be a powerful neurotoxin
and respiratory toxin. The addition of Manganese to fuel
is being monitored closely and it is just a matter of
time before their removal is mandated.
Oxygenate
Blending
Oxygenate blending adds oxygen to the fuel
in oxygen-bearing compounds such as MTBE, ethanol and
ETBE, and so reduces the amount of carbon monoxide and
unburned fuel in the exhaust gas, thus reducing smog.
In many areas throughout the US oxygenate blending is
mandatory. For example, in Southern California, fuel must
contain 2% oxygen by weight. The resulting fuel is often
known as reformulated gasoline (RFG) or oxygenated gasoline.
The federal requirement that RFG contain oxygen has been
dropped, effective May 6, 2006.
MTBE use is being phased out in some states
due to issues with contamination of ground water. In some
places it is already banned. Ethanol and to a lesser extent
the ethanol derived ETBE are a common replacements.
Especially ethanol derived from biomatter
such as corn, sugar cane or grain is frequent, this will
often be referred to as bio-ethanol. An ethanol-gasoline
mix of 10% ethanol mixed with gasoline is called gasohol.
An ethanol-gasoline mix of 85% ethanol mixed with gasoline
is called E85.
The most extensive use of ethanol takes
place in Brazil, where the ethanol is derived from sugarcane.
Over 3,400 million US gallons (13,000,000 m³) of ethanol
mostly produced from corn was produced in the United States
in 2004 for fuel use, and E85 is fast becoming available
in much of the United States. The use of bioethanol, either
directly or indirectly by conversion of such ethanol to
bio-ETBE, is encouraged by the European Union Biofuels
Directive.
However since producing bio-ethanol from
fermented sugars and starches involves distillation, ordinary
people in much of Europe cannot ferment and distill their
own bio-ethanol at present (unlike in the US where getting
a BATF distillation permit has been ever so quick and
easy since the 1973 oil crisis.)
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