ChemCases.com
Pollution: Reducing the Smog, Removing the Lead

Dr. Matt Hermes

A. Introduction:

B. Reducing the Smog, Removing the Lead Concept Map


Atlanta Today
Live image courtesy WAGA-TV Skyview Cam

Atlanta, Oct. 2, 1998
Atlanta on a very clear morning, Oct. 2, 1998.  But you can see the brown haze of nitrogen oxides that are part of our smog.

Taming the Pollution that Threatens Us

Photochemical Smog: Sometimes the sky over Atlanta, Georgia is crystal clear.  At other times, visibility is reduced to very short distances because of the smog. 

Photochemical smog is the brownish haze we see over our cities.  It consists of reactive nitrogen oxide pollutants, and ozone along with dust, aerosols and acid-containing water droplets. It arises from the oxidation of nitric oxide (NO) in the presence of sunlight. 

Airborne pollutants are toxic, particularly to those with other respiratory illnesses

Our smog is a penetrating factor of modern urban life.  Electric power generation and fuel burning for locomotion and heat distribute pollutants worlwide.

Toxic Lead Residues: From the early 1930's until the mid 1970's motor fuel contained an additive, tetraethyllead, that improved fuel performance by preventing pre ignition in the cylinders. Preignition resulted in damaging and efficiency reducing knocking in the cylinders.

But combustion spread an almost universal roadside mist of toxic lead oxides that penetrated our ground and water.

This ChemCases.com unit describes the chemistry and decisions that have removed the lead and that continue to reduce the burden of photochemical smog.

 

A. Introduction:

The automobile and its fuel are parts of a single, critically linked transportation system. From the beginning of the automobile at the turn of the 20th century, cars and the fuel that powers them have been irrevocably tied together.


We could manufacture autos at our leisure and we could sell them. But without approriate fuels designed for their engines, or correspondingly, without engines designed for the fuels, we had no way to use the automobile.

But even this was not enough. We had to develop a grid of fueling stations, "gas stations", and the means of transporting fuel in bulk to those stations before we had a national transportation system.

So when pollution issues arise as result of our driving, both the automobile and its fuel must be modified in an integrated, seamless way.

This ChemCases.com case study shows us how chemistry and our culture teamed to reduce the airborne pollution of our automobile-based industrial culture by:

  • removing the lead compounds from motor fuel and
  • reducing toxic nitrogen oxides from burning gasoline without disrupting the transportation systems of the country.

You may wish to go now to the concept map outlining this study.

About ChemCases.com

ChemCases.com is a series of curriculum units that link responsible decision making in product development with chemical principles taught in General Chemistry. 

We expect ChemCases.com curriculum supplements will lead interested students toward the sciences, medicine, pharmacy and engineering by:

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Developing Knowledge of how the tools of chemistry are used in the service of society.
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Comprehension of the conflicting information necessary to move an idea  to the marketplace.
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Application of this information to show how chemical principles are used to make decisions.
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Evaluation of the data to synthesize solutions to technical and non technical challenges.

Visit ChemCases.com Home Page.

t_logo.gif (12525 bytes) ChemCases.com is a National Science Foundation supported curriculum development project. 

About the Author

Dr. Matt Hermes took his first chemistry course in 1949 as a thirteen year old high school student. He has made the fascination of chemistry his career ever since.


2000 Kennesaw State University.
Principal Investigator
Laurence Peterson; Project Director Matthew Hermes.

NSF Grant DUE-9652889

Pollution of Ground, Water and Air

We have had pollutants of our ground, water and air with us for centuries. Smoke from the heating fires of the 18th century blackened the skies over London. In the 19th century, chemical ash from the manufacture of zinc filtered across Palmerton, Pennsylvania, killing most of our plants.


Defoliated Hillside, Palmerton, PA

This site resulted from 70 years of operation by New Jersey Zinc. It has been a
US Superfund cleanup location for nearly 20 years.

Contamination from copper smelting at the Anaconda site in Anaconda, Montana covered 1500 acres. But there is a golf course on the site now as a result of taxpayer and legislative support of the US EPA's Superfund effort. 


Jack Nicklaus plays the golf course constructed on the site of the Anaconda smelter. (Courtesy, Asarco)

We continue to tackle pollution problems. We once put a compound, tetraethyllead (TEL) in gasoline to make our automobiles run smoothly only to find the lead compounds emitted from the tailpipe poisoned our environment.  We removed TEL and continue to reformulate our fuels.

Now we know our engines and power plants and engines exhaust nitrogen oxides as products of high temperature processes and we work to eliminate or curb these damaging pollutants.

 

B. ChemCases - Reducing the Smog, Removing the Lead - Concept Map

Chemical Concepts - Thermochemistry, Kinetics, Catalysis, Intermolecular Forces:
Fuel chemistry requires an understanding of thermochemistry - the energy and heat consequences of chemical reactions.

We might think that the only chemistry in the cylinder of an internal combustion engine would be the oxidation of fuel hydrocarbons. But that is not the complete story. Temperatures are so high in the cylinder as hydrocarbons react that nitrogen - generally inert - reacts with oxygen to give nitric oxide (NO).

Then in the atmosphere, driven by the energy of the sun, a cascade of pollutant forming reactions occurs. These reactions that produce nitrogen dioxide and ozone are catalytic chain reactions in which the product of one reaction is a reactant in the next. Only by placing catalysts in the exhaust of an engine - a catalyst that increases the kinetic rate of the reverse reaction of NO back to oxygen and nitrogen, do we reduce the impact of the polluting exhaust gases.

Tetraethyllead (TEL) is soluble in gasoline! We understand the intermolecular forces that allow this metal-based material to be compatible. But its oxidation products are solid particles that pervasively introduced themselves into land and water.

Issues and Decision Making:
To remove TEL from fuels we needed replacement formulations that would retain the engine efficiency yet not be too costly. And coincedently the catalytic converters that would reduce NO required that TEL be removed since the lead residues would inactivate the catalysts.

How do we make a systematic change of ALL gasoline fuels and ALL gasoline engines in the United States withour seriously disrupting the entire system of transportation in the country? Who must cooperta in the dynamic process that allows new fuels to be introduced for the new vehicles with catalysts and modified engines, yetrespects the rights of those tens of millions of owners of vehicles requiring the older fuel systems?

1.  Thermochemistry of Fuel Combustion    arrow2.jpg (895 bytes)
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2.  Standard Oil, Refining Oil to Kerosene, Makes Gasoline as Autos Develop   4.  Henry Ford Develops the Model T, Makes Millions of Them    
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3.  Midgley Finds  Tetraethyllead Makes Engines Run Smoothly arrow2.jpg (895 bytes)
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5.  Unbelievable Levels of Gasoline in Motor Transportation    
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13.  Transition Metals as Catalysts   8.  Health Effects from Lead in the Atmosphere   7.  Pollution from Nitrogen Oxides and Atmospheric Chemistry arrow2.jpg (895 bytes)

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6.  Equilibrium and Rates of Reaction Between N2 and O2
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14.  Sinfelt's Observations of Petroleum Cracking   9.  Nationwide Health Concerns and 10.  Health Effects of Photochemical Smog in the Great Cities    
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  15.  Catalysts for High Rates of Fuel Production arrow2.jpg (895 bytes)
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11.  Fuels Containing no Tetraethyl Lead arrow2.jpg (895 bytes)
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12.  Catalytic Converter to Reduce NOx arrow2.jpg (895 bytes)
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16.  Transition Metals as Catalysts
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    17.  Conversion of the Entire Fuel Manufacture and Distribution System   18.  Conversion of All Automobile Engines and Exhaust Systems    
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    19.  Enormous Resources and Effort by Fuel Companies   and concerted 20.  Enormous Resources and Effort by Auto Companies
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21.  Who Should Pay for Removal of Lead and Introduction of Catalytic Converter?