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CHEM 2500 Tulane Exam 1 (1).
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CHEM 2500 Tulane Exam 1 (1).
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✅✅sustainability - -Arises from the perception that human activity is using up
nature's resources at rates beyond the capacity of nature to restore them. The
maintaining of these resources for future generations. There are legal requirements
for companies that may put these resources in danger.
sustainable logging - ✅✅-extracting wood in ways the permit the regeneration of
forests
sustainable agriculture - ✅✅ -feeding people without depleting the nutritive capacity
of the soil or biodiversity by protecting the natural habitats.
natural energy flows - ✅✅-The energy flowing through the Earth and it's
environment, powered by the sun and geothermal energy both directly and indirectly.
albedo - ✅✅ -About 30% of the overall quantity of energy that comes from the sun
to the Earth (54.4 x 10^20 kJ/year). Contributes significantly to the overall energy
balance of the Earth.
"avaliable" energy resources - ✅✅ -the availability of these resources depends on
the cost and energy needed to extract and process these resources.
Origins of Fossil Fuels: Coal - ✅✅ -Coal deposits are the remains of plant matter
from huge, thickly wooded swamps that flourished 250 million years ago, when the
climate was mild and moist. These wooden remains are made up of lignin and
cellulose. The cellulose is broken down (oxidized) by aerobic bacteria into carbon
dioxide and water when the plant dies. Lignin is much more resistant to bacterial
action. It is a complex 3-dimensional polymer based on benzene rings. The lignin
accumulated under water, became peat, and then metamorphosed into coal by the
loss of oxygen atoms via the expulsion of water and carbon dioxide gas.
Origins of Fossil Fuels: Petroleum and Natural Gas - ✅✅ -Petroleum and natural
gas deposits are of marine origin, A minute fraction of the reduced carbon settles at
the bottom of the ocean where there is no access to oxygen. The biological debris is
the covered by sand and clay particles and compacted into a layer of organic matter.
Anaerobic bacteria digest the biological matter, releasing most of the oxygen and
nitrogen. As the deposit becomes more deeply buried the temperature lowers and
the pressure rises. This causes organic rearrangement reactions to occur. These
reactions release methane and other light gases which become trapped in pockets
under impermeable rocks, this forms natural gas. Petroleum or oil is produced from
the remaining heavy compounds which migrate as a water emulsion, from witch the
water is squeezed out as the sediment is compacted.
Fuel Energies - ✅✅ -The chemical energy stored in fuels, it resides in the bonds
that hold the atoms together. But wait... doesn't it take energy to break bonds? The
, chemical energy of a hydrogen molecule resides in its propensity to react with
oxygen. The energy GAINED by forming these new bonds (of water and carbon
dioxide) more than offsets the energy lost by breaking the bonds in the first place.
The fuel energy of a particular fuel can be calculated by using the bond dissociation
energies of all the bonds involved in the chemical reaction (products - reactants).
Petroleum - ✅✅ -Oil is a complex mixture of hydrocarbons and small quantities of
other substances, such as sulfur, nitrogen, and traces of metallic elements. Most of
the hydrocarbon bonds are saturated (no multiple bonds) and a good amount are
made up of benzene rings (aromatic).
Petroleum Fractions - ✅✅ -Petroleum molecules range widely in various fractions,
and all these different fractions have different functions.
# of Carbon Atoms
Gaseous 1-4
Gasoline 5-12
Kerosene 10-16
Gas oil 15-22
Lube oil 19-35
Residue 36-90
Cracking - ✅✅ -Some reactors transform molecules chemically in order to match
the needs of the markets. The fraction of carbon atoms for gasoline is at high
demand.
This process takes larger hydrocarbons (in the kerosene or gas-oil range) and
breaks them down into smaller hydrocarbons in the gasoline range. This is
accomplished at high temperatures (400-600 Celsius) with the aid of a catalyst, an
aluminosilicate material impregnated with potassium.
Alkylation -✅✅ -Some reactors transform molecules chemically in order to match
the needs of the markets. The fraction of carbon atoms for gasoline is at high
demand.
This process enhances the gassoline fraction by building up mid-sized molecules
from two smaller ones. This process is catalyzed by strong acids.
Catalytic Reforming - ✅✅ -This process reforms straight-chain alkanes and
converts them into aromatic ring structures. These run at high pressure (15-20 atm)
and high temperatures (500-600 Celsius).
Advantages of Petroleum - ✅✅ -It is a liquid = easily transported
relatively clean; because sulfur and metallic containing compounds stay in the
residue they are not released into the atmosphere
very efficient extraction, transport, refining, and delivery technologies
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