Fuels & EnergyFuels & Energy

IB OptionIB Option

AP/IB ChemistryAP/IB Chemistry

Chanlder High SchoolChanlder High School

Present Sources of Energy – Present Sources of Energy – Fossil FuelsFossil Fuels

A.A. Fossil fuelsFossil fuelsPetroleum Petroleum

thick, dark liquid composed mainly of thick, dark liquid composed mainly of hydrocarbonshydrocarbons

formed from the remains of marine formed from the remains of marine organisms that lived ~500 million years agoorganisms that lived ~500 million years ago

Fossil FuelsFossil Fuels

hydrocarbon chains range from 5 to hydrocarbon chains range from 5 to 25+ carbons25+ carbonschains separated based on number of chains separated based on number of

carbonscarbonsseparation occurs through a boiling separation occurs through a boiling

processprocesschains with fewest number of carbons chains with fewest number of carbons

boil off first, leaving heavier chains boil off first, leaving heavier chains behindbehind

Fossil FuelsFossil Fuels

commercial uses of petroleum fractions commercial uses of petroleum fractions summarized in table below:summarized in table below:

Petroleum Fraction with Respect to # of Carbons

Major Uses

C5 – C10 Gasoline

C10 – C18 Kerosene; Jet fuel

C15 – C25 Diesel fuel; Heating oil; Lubricating oil

>C25 Asphalt

Fossil FuelsFossil Fuels

importance of gasoline led to a new importance of gasoline led to a new separation process called pyrolytic separation process called pyrolytic crackingcrackingheavier petroleum molecules are heated heavier petroleum molecules are heated

to very high temperaturesto very high temperatureshigh temperatures cause the large high temperatures cause the large

molecules to break into smaller molecules to break into smaller molecules that can be used as gasolinemolecules that can be used as gasoline

Present Sources of Energy – Present Sources of Energy – Natural GasNatural Gas

Natural GasNatural Gas

combination of methane, ethane, combination of methane, ethane, propane, and butane (predominantly propane, and butane (predominantly methane)methane)

formed in conjunction with petroleumformed in conjunction with petroleum

Present Sources of Energy – Present Sources of Energy – CoalCoal

CoalCoal

complex organic molecule with complex organic molecule with empirical formula of CH2O and empirical formula of CH2O and molecular mass of ~500,000 g/mol.molecular mass of ~500,000 g/mol.

formed from the remains of plants that formed from the remains of plants that were buried and subjected to high were buried and subjected to high pressure and heatpressure and heat

CoalCoal

matures through four stagesmatures through four stageslignite (71% C, 4% H, 23% O, 1% N, 1% S)lignite (71% C, 4% H, 23% O, 1% N, 1% S)

subbituminous (77% C, 5% H, 16% O, 1% N, subbituminous (77% C, 5% H, 16% O, 1% N, 1% S)1% S)

bituminous (80% C, 6% H, 8% O, 1% N, 5% bituminous (80% C, 6% H, 8% O, 1% N, 5% S)S)

anthracite (92% C, 3% H, 3% O, 1% N, 1% S)anthracite (92% C, 3% H, 3% O, 1% N, 1% S)

CoalCoal

currently supplies 20% of energy currently supplies 20% of energy consumed in U.S.consumed in U.S.

expensive and dangerous to mineexpensive and dangerous to mine

burning high sulfur coal burning high sulfur coal sulfur sulfur dioxide air pollutants dioxide air pollutants acid rain acid rain

burning coal adds to the greenhouse burning coal adds to the greenhouse gas problemgas problem

New Energy Sources –New Energy Sources –Coal ConversionCoal Conversion

Coal conversionCoal conversionCoal is broken down into smaller, more Coal is broken down into smaller, more

economical molecules via coal economical molecules via coal gasificationgasificationcoal is treated with oxygen and steam at coal is treated with oxygen and steam at

high temperatureshigh temperaturesthis breaks carbon-carbon bonds, and new this breaks carbon-carbon bonds, and new

carbon-hydrogen or carbon-oxygen bonds carbon-hydrogen or carbon-oxygen bonds are formedare formed

this produces a product called synthetic this produces a product called synthetic gas (syngas)gas (syngas)

Coal ConversionCoal Conversion

Syngas is used both as a fuel and as Syngas is used both as a fuel and as a raw material to produce other fuelsa raw material to produce other fuels

The process of producing syngas The process of producing syngas involves both exothermic and involves both exothermic and endothermic reactionsendothermic reactionsIf correct concentrations of coal, oxygen, If correct concentrations of coal, oxygen,

and steam are maintained, no external and steam are maintained, no external energy is requiredenergy is required

New Energy Sources –New Energy Sources –HydrogenHydrogen

HydrogenHydrogen Combustion of hydrogen is highly exothermic Combustion of hydrogen is highly exothermic

(2.5 times that of natural gas per gram)(2.5 times that of natural gas per gram)

No harmful product produced, only waterNo harmful product produced, only water

Produced from the reaction of methane with Produced from the reaction of methane with waterwater

CHCH44 + H + H22O O 3H 3H22 + CO + CO

**this is not very economical because it is a **this is not very economical because it is a highly endothermic reactionhighly endothermic reaction

HydrogenHydrogen

Three main problems to using Three main problems to using hydrogen as fuelhydrogen as fuelexpensive to produce – virtually no expensive to produce – virtually no

hydrogen exists as free hydrogen hydrogen exists as free hydrogen moleculesmolecules

storage – hydrogen decomposes to atoms storage – hydrogen decomposes to atoms on metal surfaces; these small atoms on metal surfaces; these small atoms cause structural damage to the metalcause structural damage to the metal

transport – amount of energy per unit transport – amount of energy per unit volume is small; very large amounts must volume is small; very large amounts must be transported to be usefulbe transported to be useful