Vehicular Pollution

1
Vehicular Pollution
2
Sulfur Dioxide

• Reduction of sulfuric acid aerosols in urban
  areas made by building tall smoke stacks to
  disperse plumes over wider areas
• alleviates local problems
• creates problems downwind
• Abatement requires reducing SO2 emissions and/or
  limiting sulfur content of fuels
• (i) coal-fired power plants use SO2 scrubbers
  in stacks
• gas passes through a slurry of limestone to give
  calcium sulphite
• CaCO3 SO2 ? CaSO3 CO2
• (must be disposed)

3
Sulfur Dioxide

• Also use regenerable amine salts as the scrubbing
  agents.
• Heating the products recovers the amine salt and
  produces SO2 which can be converted to
  commercial-grade H2SO4
• (ii) Remove sulfur from coal before or during
  combustion
• major sulfide mineral in FeS2 (iron pyrite)
• can be removed by grinding the coal and floating
  the mineral products away with water / oil /
  surfactant mixture
• (coal still contains organically bound sulfur).

4
NOxs, CO and Hydrocarbons

• Combustion inevitably leads to the production of
  NO
• N2 O2 ? 2NO ?Hº 180 kJ / mole
• and also accounts for much of the atmospheric CO
  and hydrocarbons

5
NOxs, CO and Hydrocarbons

• NOx emissions are difficult to control
• (trade-off between NOxs and unburned gases)
• NO production rate is maximum near the
  stoichiometric ratio where the highest
  temperatures are reached.
• If less air is admitted (fuel-rich), NO
  production falls, combustion is less complete and
  CO and unburned hydrocarbons (HCs) are emitted
  in larger concentrations.

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NOxs, CO and Hydrocarbons

• Production of CO can be described in terms of the
  gas phase equilibrium when there is a shortage of
  O2 to burn the fuel
• High T favours production of CO
• High O2 concentrations favours CO2
• (but engines usually run fuel-rich)

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Stoichiometric point

• stoichiometric point the ideal ratio of air to
  fuel.
• Theoretically, at this ratio, all of the fuel
  will be burned using all of the oxygen in the
  air.
• For gasoline, the stoichiometric ratio is about
  14.71,
• for each pound of gasoline, 14.7 pounds of air
  will be burned.
• The fuel mixture actually varies from the ideal
  ratio quite a bit during driving.
• Sometimes the mixture can be lean (an air-to-fuel
  ratio higher than 14.7), and other times the
  mixture can be rich (an air-to-fuel ratio lower
  than 14.7).

9
Car Emissions

• The main emissions of a car engine are
• Nitrogen gas (N2) - Air is 78-percent nitrogen
  gas, and most of this passes right through the
  car engine.
• Carbon dioxide (CO2)
• Water vapor (H2O)

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Abatement Strategies

• (i) possible to reduce NOx , CO and HC emissions
  by carrying out combustion in two stages
• step 1 fuel-rich
• step 2 air-rich (fuel lean)
• temperatures never as high as for stoichiometric
  ratio. (fuel burned more completely)
• (newer power plants, less successful in cars)

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Catalytic Converters

• Catalytic converters are designed to reduce
• Carbon monoxide (CO), a poisonous gas that is
  colorless and odorless.
• Hydrocarbons or volatile organic compounds
  (VOCs), a major component of smog produced mostly
  from evaporated, unburned fuel.
• Nitrogen oxides (NO and NO2, together called
  NOx), a contributor to smog and acid rain, which
  also causes irritation to human mucus membranes.

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Abatement Strategies

• (ii) Remove pollutants from the exhaust gases
• three-way catalytic converter reduces emissions
  of HCs, CO and NO

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Peak ozone levels cut by half between 1970 and
1990 even with a 60 increase in vehicle miles
driven
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Catalytic Converter

• In the catalytic converter, there are two
  different types of catalyst at work, a reduction
  catalyst and an oxidation catalyst.
• Both types consist of a ceramic structure coated
  with a metal catalyst, usually platinum, rhodium
  and/or palladium.
• The idea is to create a structure that exposes
  the maximum surface area of catalyst to the
  exhaust stream, while also minimizing the amount
  of catalyst required, as the materials are
  extremely expensive.
• Some of the newest converters have even started
  to use gold mixed with the more traditional
  catalysts. Gold is cheaper than the other
  materials and could increase oxidation, the
  chemical reaction that reduces pollutants, by up
  to 40 percent

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Most modern cars are equipped with three-way
catalytic converters. This refers to the three
regulated emissions it helps to reduce.
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The reduction catalyst is the first stage of the
catalytic converter. It uses platinum and rhodium
to help reduce the NOx emissions. When an NO or
NO2 molecule contacts the catalyst, the catalyst
rips the nitrogen atom out of the molecule and
holds on to it, freeing the oxygen in the form of
O2. The nitrogen atoms bond with other nitrogen
atoms that are also stuck to the catalyst,
forming N2. For example 2NO ? N2 O2 or 2NO2 ?
N2 2O2
The oxidation catalyst is the second stage of the
catalytic converter. It reduces the unburned
hydrocarbons and carbon monoxide by burning
(oxidizing) them over a platinum and palladium
catalyst. This catalyst aids the reaction of the
CO and hydrocarbons with the remaining oxygen in
the exhaust gas. For example 2CO O2 ? 2CO2
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There are two main types of structures used in
catalytic converters -- honeycomb and ceramic
beads. Most cars today use a honeycomb structure.
Ceramic honeycomb catalyst structure.
http//auto.howstuffworks.com/catalytic-converter2
.htm
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The catalytic converter consists of several
components

• The core, or substrate. In modern catalytic
  converters, this is most often a ceramic
  honeycomb, however stainless steel foil
  honeycombs are also used. The purpose of the core
  is to "support the catalyst" and therefore it is
  often called a "catalyst support". The ceramic
  substrate was invented by Rodney Bagley, Irwin
  Lachman and Ronald Lewis at Corning Glass for
  which they were inducted into the National
  Inventors Hall of Fame in 2002.

21
The catalytic converter consists of several
components

• The washcoat. In an effort to make converters
  more efficient, a washcoat is utilized, most
  often a mixture of silica and alumina. The
  washcoat, when added to the core, forms a rough,
  irregular surface which has a far greater surface
  area than the flat core surfaces, which is
  desirable to give the converter core a larger
  surface area, and therefore more places for
  active precious metal sites. The catalyst is
  added to the washcoat (in suspension) before
  application to the core.

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The catalytic converter consists of several
components

• The catalyst itself is most often a precious
  metal. Platinum is the most active catalyst and
  is widely used. However, it is not suitable for
  all applications because of unwanted additional
  reactions and/or cost. Palladium and rhodium are
  two other precious metals that are used. Platinum
  and rhodium are used as a reduction catalyst,
  while platinum and palladium are used as an
  oxidization catalyst. Cerium, iron, manganese and
  nickel are also used, though each has its own
  limitations. Nickel is not legal for use in the
  European Union (due to reaction with carbon
  monoxide). While copper can be used, its use is
  illegal in North America due to the formation of
  dioxin.

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• Controlling Pollution and Improving Performance
• The third stage of conversion is a control system
  that monitors the exhaust stream, and uses this
  information to control the fuel injection system.
  
• An oxygen sensor mounted upstream of the
  catalytic converter tells the engine computer how
  much oxygen is in the exhaust.
• The engine computer can increase or decrease the
  amount of oxygen in the exhaust by adjusting the
  air-to-fuel ratio.
• This control scheme allows the engine computer to
  make sure that the engine is running at close to
  the stoichiometric point, and also to make sure
  that there is enough oxygen in the exhaust to
  allow the oxidization catalyst to burn the
  unburned hydrocarbons and CO.

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Controlling Pollution and Improving Performance

• One of the biggest shortcomings is that it only
  works at a fairly high temperature.
• When you start your car cold, the catalytic
  converter does almost nothing to reduce the
  pollution in your exhaust.
• One simple solution to this problem is to move
  the catalytic converter closer to the engine.
• This means that hotter exhaust gases reach the
  converter and it heats up faster, but this may
  also reduce the life of the converter by exposing
  it to extremely high temperatures.
• Most carmakers position the converter under the
  front passenger seat, far enough from the engine
  to keep the temperature down to levels that will
  not harm it.

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Controlling Pollution and Improving Performance

• Preheating the catalytic converter is a good way
  to reduce emissions.
• The easiest way to preheat the converter is to
  use electric resistance heaters.
• Unfortunately, the 12-volt electrical systems on
  most cars don't provide enough energy or power to
  heat the catalytic converter fast enough.
• Most people would not wait several minutes for
  the catalytic converter to heat up before
  starting their car.
• Hybrid cars that have big, high-voltage battery
  packs can provide enough power to heat up the
  catalytic converter very quickly.

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Controlling Pollution and Improving Performance

• Catalytic converters in diesel engines do not
  work as well in reducing NOx.
• One reason is that diesel engines run cooler than
  standard engines, and the converters work better
  as they heat up.
• Some of the leading environmental auto experts
  have come up with a new system that helps to
  combat this.
• They inject a urea solution in the exhaust pipe,
  before it gets to the converter, to evaporate and
  mix with the exhaust and create a chemical
  reaction that will reduce NOx. Urea, also known
  as carbamide, is an organic compound made of
  carbon, nitrogen, oxygen and hydrogen. It's found
  in the urine of mammals and amphibians. Urea
  reacts with NOx to produce nitrogen and water
  vapor, disposing more than 90 percent of the
  nitrogen oxides in exhaust gases source
  Innovations Report.

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Diesel engines

• For compression ignition (i.e., Diesel) engines,
  the most commonly used catalytic converter is the
  diesel oxidation catalyst. The catalyst uses
  excess O2 (oxygen) in the exhaust gas stream to
  oxidize CO (Carbon Monoxide) to CO2 (Carbon
  Dioxide) and HC (hydrocarbons) to H2O (water) and
  CO2. These converters often reach 90
  effectiveness, virtually eliminating diesel odor
  and helping to reduce visible particulates
  (soot), however they are incapable of reducing
  NOx as chemical reactions always occur in the
  simplest possible way, and the existing O2 in the
  exhaust gas stream would react first.

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Diesel engines

• To reduce NOx on a compression ignition engine it
  is necessary to change the exhaust gas - two main
  technologies are used for this - selective
  catalytic reduction (SCR) and NOx (NOx) traps (or
  NOx Adsorbers).
• Another issue for diesel engines is particulate
  (soot). This can be controlled by a soot trap or
  diesel particulate filter (DPF), as catalytic
  converters are unable to affect elemental carbon
  (however they will remove up to 90 of the
  soluble organic fraction). A clogging soot filter
  creates a lot of back pressure decreasing engine
  performance. However, once clogged, the filter
  goes through a regeneration cycle where diesel
  fuel is injected directly into the exhaust stream
  and the soot is burned off. After the soot has
  been burned off the regeneration cycle stops and
  injection of diesel fuel stops. This regeneration
  cycle should not affect performance of the
  engine.
• All major diesel engine manufacturers in the USA
  (Ford, Caterpillar, Cummins, Volvo, MMC) starting
  January 1, 2007 are required to have a catalytic
  converter and a soot filter inline, as per new
  United States Environmental Protection Agency
  (EPA) regulation.

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Oxygen storage in three-way converters

• In order to oxidize CO and HC, the catalytic
  converter also has the capability of storing the
  oxygen from the exhaust gas stream, usually when
  the air fuel ratio goes lean. When insufficient
  oxygen is available from the exhaust stream the
  stored oxygen is released and consumed. This
  happens either when oxygen derived from NOx
  reduction is unavailable or certain maneuvers
  such as hard acceleration enrich the mixture
  beyond the ability of the converter to
  compensate.
• Note that diesel catalysts do not use this
  feature as there is sufficient O2 in the exhaust
  gas stream to handle the CO HC reductions
  needed.

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Are lawn mowers next?

• Gallon for gallon, new lawn mower engines
  contribute 93 times more smog-forming emissions
  than new cars.
• The EPA and the state regulators of California
  are trying hard to get golf ball-sized catalytic
  converters into lawn mower and other small
  engines.
• However, just like in the 1970s, the lawmakers
  are being met with a powerful lobby.
• Briggs Stratton, the leading manufacturer of
  small engines, says that these regulations would
  make for an unsafe product that emits too much
  heat. Four smaller lawn mower engine
  manufacturers have refuted this charge.
• Briggs Stratton also contends that the
  overheating could cause brush fires if the mowers
  are left running and sitting still. California
  democrats and the EPA think it has more to do
  with the bottom line.
• Pending regulations proposed in California could
  reduce emissions by the equivalent of 800,000
  cars per day source Barringer.

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Catalytic Converter Theft

• All over the country, SUVs and trucks are
  becoming targets for opportunists looking to cash
  in on the valuable precious metals used inside
  catalytic converters.
• A standard catalytic converter contains several
  hundred dollars worth of platinum, palladium and
  rhodium. The ground clearance on trucks and SUVs
  makes for easy access to the converters, so all a
  thief needs is a reciprocating saw and about 60
  seconds.
• This trend has police on the lookout in many
  parts of the country where this kind of theft has
  been a problem. Police caution SUV and truck
  drivers to park in busy, well-lit areas.

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Environmental impact

• Catalytic converters have proven to be reliable
  devices and have been successful in reducing
  noxious tailpipe emissions. However, they may
  have some adverse environmental impacts in use
• The requirement for a rich burn engine to run at
  the stoichiometric point means it uses more fuel
  than a "lean burn" engine running at a mixture of
  201 or less. This increases the amount of fossil
  fuel consumed and the carbon dioxide emissions of
  the vehicle. However, NOx control on lean burn
  engines is problematic at best, and many lean
  burn engine manufacturers are considering rich
  burn variations.
• The manufacturing of catalytic converters
  requires palladium and/or platinum a portion of
  the world supply of these precious metals is
  produced near the Russian city of Norilsk, with
  significant negative environmental effects.

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Failed Converters

• There are two ways a converter can fail
• It can become clogged.
• It can become poisoned.
• There really is no "inspection port" for the
  consumer or mechanic to see an actual clog in a
  converter.
• Often, the only way to tell if a catalytic
  converter is malfunctioning (plugged) is to
  remove it and check the change in engine
  performance.
• When a clogged converter is suspected, some
  mechanics temporarily remove the O2 sensor from
  the exhaust pipe ahead of the catalytic converter
  and look for a change in performance.

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Failed Converters

• A catalytic converter relies on receiving the
  proper mix of exhaust gases at the proper
  temperature. Any additives or malfunctions that
  cause the mixture or the temperature of the
  exhaust gases to change reduce the effectiveness
  and life of the catalytic converter. Leaded
  gasoline and the over-use of certain fuel
  additives can shorten the life of a catalytic
  converter.
• A catalytic converter can also fail because of
• Bad exhaust valves on the engine
• Fouled plugs causing unburned fuel to overheat
  the converter

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Failed Converters

• Sometimes you can tell that a converter is
  clogged because you don't go any faster when you
  push the gas pedal.
• Also, there usually is a noticeable drop in gas
  mileage associated with a clogged catalytic
  converter.
• A partially clogged converter often acts like an
  engine governor, limiting the actual RPMs to a
  fast idle.
• A totally clogged converter causes the engine to
  quit after a few minutes because of all the
  increased exhaust back pressure.

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Failed Converters

• Here is a safety reminder Do not park your car
  over tall grass or piles of dry leaves. Your
  car's perfectly running catalytic converter gets
  very hotenough to start fires! You can keep it
  running well by keeping the ignition system in
  top shape, to prevent any unburnt fuel from
  entering the catalytic converter.

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Gasoline and its Formulations

• Urban pollution has lead to extensive research in
  design of fuel formulations
• (i) Knocking and Octane
• combustion is a radical chain process
• ignition occurs in a compressed fuel-air mixture.
  Compression can cause heating and pre-ignition
• spontaneous fragmentation premature explosion

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Gasoline and its Formulations

• temperature required for radical generation
  depends on the structure of the fuel molecule
• branched HCs more resistant to radical chain
  formation than straight chain HCs
• C-H methyl group bonds (423 kJ/mol)
• C-H methylene group bonds (410 kJ/mol)

40
Gasoline and its Formulations

• branched compounds have more CH3 groups and are
  less susceptible to attack
• Gasoline mixture of low-boiling HCs (C7, C8)
• resistance to pre-ignition ? octane rating

41
Diesels and Cetane

• In diesel engines, air in the piston is
  pre-heated by compression and the fuel is sprayed
  into the hot chamber, burning on contact
• efficient engine ? large trucks and buses
• long lifetime
• Want easy fragmentation to enhance combustion of
  the injected fuels
• i.e. straight-chain HCs (usually C11 C16)
• quality of fuel set by cetane
• n-hexadecane has cetane number 100
• heptamethylnonane (highly branched) has cetane
  number 15

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Diesels and Cetane

• Higher particulate emissions than spark engines
• molecules at the air/fuel interface burn
  completely but molecules at the centre of the
  injected fuel plume heat up before combusting and
  decompose to solid carbon

43
Lead

• 1920s knocking could be avoided by adding
  organo-lead compounds to gasoline (tetraethyl- or
  tetramethyl-lead)
• suppress the radical chain reactions in
  pre-ignition
• weak alkyl-lead bonds break to produce Pb atoms
  which react with O2 to form PbO and PbO2. These
  particles act as attachment sites for HC radicals
  and terminate the chain reaction.
• to avoid build up of lead deposits, gas also
  contains ethylene dichloride (or dibromide)

44
Lead

• organo halogens are lead scavengers and give PbX2
  (X Cl, Br) which are volatile at combustion
  temperatures
• By mid 1970s unleaded gasoline displaces
  leaded gasoline
• (poisoning of catalysts in catalytic converter,
  health problems)

45
Lead

• Lead was outlawed as an automotive gasoline
  additive in this country in 1986--more than sixty
  years after its introduction--to enable the use
  of emissions-reducing catalytic converters in
  cars (which are contaminated and rendered useless
  by lead) and to address the myriad health and
  safety concerns that have shadowed the toxic
  additive from its first, tentative appearance on
  US roads in the twenties, through a period of
  international ubiquity only recently ending.

46
Lead

• Since the virtual disappearance of leaded gas in
  the United States (it's still sold for use in
  propeller airplanes), the mean blood-lead level
  of the American population has declined more than
  75 percent.
• A 1985 EPA study estimated that as many as 5,000
  Americans died annually from lead-related heart
  disease prior to the country's lead phaseout.
• According to a 1988 report to Congress on
  childhood lead poisoning in America by the
  government's Agency for Toxic Substances and
  Disease Registry, one can estimate that the
  blood-lead levels of up to 2 million children
  were reduced every year to below toxic levels
  between 1970 and 1987 as leaded gasoline use was
  reduced. From that report and elsewhere, one can
  conservatively estimate that a total of about 68
  million young children had toxic exposures to
  lead from gasoline from 1927 to 1987.

http//www.thenation.com/doc/20000320/kitman
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The lead issue

• the severe health hazards of leaded gasoline were
  known to its makers and clearly identified by the
  US public health community more than seventy-five
  years ago, but were steadfastly denied by the
  makers, because they couldn't be immediately
  quantified
• other, safer antiknock additives--used to
  increase gasoline octane and counter engine
  "knock"--were known and available to oil
  companies and the makers of lead antiknocks
  before the lead additive was discovered, but they
  were covered up and denied, then fought,
  suppressed and unfairly maligned for decades to
  follow

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The lead issue

• the US government was fully apprised of leaded
  gasoline's potentially hazardous effects and was
  aware of available alternatives, yet was
  complicit in the cover-up and even actively
  assisted the profiteers in spreading the use of
  leaded gasoline to foreign countries
• the benefits of lead antiknock additives were
  wildly and knowingly overstated in the beginning,
  and continue to be. Lead is not only bad for the
  planet and all its life forms, it is actually bad
  for cars and always was

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The lead issue

• for more than four decades, all scientific
  research regarding the health implications of
  leaded gasoline was underwritten and controlled
  by the original lead cabal--Du Pont, GM and
  Standard Oil such research invariably favored
  the industry's pro-lead views, but was from the
  outset fatally flawed independent scientists who
  would finally catch up with the earlier work's
  infirmities and debunk them were--and continue to
  be--threatened and defamed by the lead interests
  and their hired hands

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The lead issue

• confronted in recent years with declining sales
  in their biggest Western markets, owing to lead
  phaseouts imposed in the United States and, more
  recently, Europe, the current sellers of lead
  additives have successfully stepped up efforts to
  market their wares in the less-developed world,
  efforts that persist and have resulted in some
  countries today placing more lead in their
  gasoline, per gallon, than was typically used in
  the West, extra lead that serves no purpose other
  than profit

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The lead issue

• faced with lead's demise and their inevitable
  days of reckoning, these firms have used the
  extraordinary financial returns that lead
  additive sales afford to hurriedly fund
  diversification into less risky, more
  conventional businesses, while taking a page from
  the tobacco companies' playbook and
  simultaneously moving to reorganize their
  corporate structures to shield ownership and
  management from liability for blanketing the
  earth with a deadly heavy metal.

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Poisonous Lead

• Lead is poison, a potent neurotoxin whose
  sickening and deadly effects have been known for
  nearly 3,000 years and written about by
  historical figures from the Greek poet and
  physician Nikander and the Roman architect
  Vitruvius to Benjamin Franklin. Odorless,
  colorless and tasteless, lead can be detected
  only through chemical analysis. Unlike such
  carcinogens and killers as pesticides, most
  chemicals, waste oils and even radioactive
  materials, lead does not break down over time. It
  does not vaporize, and it never disappears.

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Poisonous Lead

• For this reason, most of the estimated 7 million
  tons of lead burned in gasoline in the United
  States in the twentieth century remains--in the
  soil, air and water and in the bodies of living
  organisms. Worldwide, it is estimated that modern
  man's lead exposure is 300 to 500 times greater
  than background or natural levels. Indeed, a 1983
  report by Britain's Royal Commission on
  Environmental Pollution concluded that lead was
  dispersed so widely by man in the twentieth
  century that "it is doubtful whether any part of
  the earth's surface or any form of life remains
  uncontaminated by anthropogenic man-made lead."

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Poisonous Lead

• While lead from mining, paint, smelting and other
  sources is still a serious environmental problem,
  a recent report by the government's Agency for
  Toxic Substances and Disease Registry estimated
  that the burning of gasoline has accounted for 90
  percent of lead placed in the atmosphere since
  the 1920s. (The magnitude of this fact is placed
  in relief when one considers the estimate of the
  US Public Health Service that the associated
  health costs from a parallel problem--the
  remaining lead paint in America's older
  housing--total in the multibillions.)

http//www.thenation.com/doc/20000320/kitman/2
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Tetraethyl lead

• Tetraethyl lead was first discovered by a German
  chemist in 1854. A technical curiosity, it was
  not used commercially on account of "its known
  deadliness." It is highly poisonous, and even
  casual cumulative contact with it was known to
  cause hallucinations, difficulty in breathing
  and, in the worst cases, madness, spasms,
  palsies, asphyxiation and death. Still unused in
  1921, sixty-seven years after its invention, it
  was not an obvious choice as a gasoline additive.

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Tetraethyl lead

• "Ethyl" brand leaded gasoline versus ethyl
  alcohol -- which was the best anti-knock additive
  for gasoline? Three grams of tetra ethyl lead and
  15 percent ethyl alcohol both improved a fuel's
  power. One was cheap, but it was a well known
  poison. The other was a clean, renewable fuel
  that helped farmers and kept nations independent
  of political oil pressures. Dozens of countries
  were already using ethyl alcohol fuels.

57
Tetraethyl Lead

• In 1922, General Motors researchers discovered
  that adding tetraethyl lead (TEL) to gasoline
  reduced engine "knock", allowing development of
  large, powerful automobiles with high compression
  engines.
• In 1924, Du Pont and General Motors (GM) created
  Ethyl Corp. to market and produce TEL.
• But "as early as the 1920s, public health
  experts, government officials, scientists,
  corporate leaders, labor, and the public were
  acutely aware of the dangers posed by the
  introduction of lead into gasoline." (Rosner
  Markowitz, 1985)

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Tetraethyl Lead

• Despite such awareness, the massive use of TEL
  went forward.  Why? -- In the 1920s, Du Pont, GM
  and Ethyl, together with Standard Oil of N.J.
  forcefully presented 3 self-serving arguments
• 1.  Leaded gasoline was essential to the
  industrial progress of America--they promoted
  lead as a "gift of God".
• 2.  Any innovation entails certain risks (which
  they said were minimal).
• 3.  Deaths and illnesses at TEL processing plants
  were due to worker carelessness -- "blame the
  victim" strategy. (E.g., in 1924, 80 of Standard
  Oil's 49 TEL plant workers died or were severely
  poisoned from organic lead)

59
Tetraethyl Lead

• So, for the sake of massive private profits,
  leaded gasoline was promoted and sold for
  decades, resulting in millions of tons of toxic
  lead pollution in the U.S. In 1973, EPA initiated
  incremental reduction of TEL in gas.
• In 1982, leaded gasoline contained 1.25 gram/gal
  ( accounted for 86 of the lead in the
  atmosphere).
• By 1986, down to 0.1 gram/gal. But by then, lead
  used in U.S. gasoline since 1920s totaled 7
  million metric tons (15.4 billion pounds)!

60
Tetraethyl Lead

• Since 31 December 1995 it has been illegal to
  sell for use in on-road vehicles any gasoline
  which contains lead or lead additives.  (But in
  1999 leaded gasoline still is produced in the
  U.S. and is being used in nonroad vehicles--
  primarily as aviation fuel, but also in farm
  machinery and race cars.)
• From 1986 to 1995, average lead concentrations in
  U.S. urban air decreased 78.   But abundant
  "legacy" lead remains in soil and dust.
• During the 1990s, TEL use expanded abroad!

http//www.uwsp.edu/geo/courses/geog100/Lead-Scien
ce.htm
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http//www.uwsp.edu/geo/courses/geog100/Lead-Ads.h
tm
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Reformulated Gasoline

• Alternative to free radical scavengers to reduce
  knocking is to alter gas composition
• (more highly branched HCs)
• initially benzene, toluene and xylenes (BTXs)
  but negative health effects and high POCPs
  (photochemical ozone creation potentials)

69
Reformulated Gasoline

• Being replaced by oxygenates fuels that contain
  molecules with one or more oxygen atoms
• Conversion to CO2 is more complete cleaner
  burning
• ethanol, methanol, MTBE and ETBE
• methyl tertiary-butyl ether
• OH reaction rates no higher than alkanes and
  octane ratings gt 100
• EtOH corn fermentation (ADM, subsidies)
• MTBE - petroleum fractions

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