2 Petroleum Composition Petroleum is a complex mixture of hydrocarbonsMostly saturated or aromatic (~10%)Small amounts of S (up to 10%), O (up to 5%), N (up to 1%), can have trace amounts of V, Fe, Al, Ca, Cu, Ni, Na, UMolecules range greatly in size and are separated into fractions based on boiling point
6 Distillation Fractions The demand for different fractions varies with the time of year.Gasoline is consumed in large amounts during summer.Fuel oil is consumed for heating in winterDemands also vary with regional climatesRefineries are able to alter the ratios of the fractions produced to meet demand & maximize profit
7 Oil ProcessingThe distilled fractions can be altered in chemical reactors to produce increased amounts of high demand fuels.
9 Catalytic Reforming Produces high octane gasoline feedstocks are heated to 500oC & passed through a series of reactors containing Pt/Al2O3 catalystProducts are aromatic hydrocarbons
10 Alkylation Produces high octane gasoline Requires an acid catalyst (usually H2SO4 or HF)Products have high degree of branchingoctane rating:aromatic>branched chain>straight chain
11 Fluidized Catalytic Cracking Breaks large molecules into smaller onesRequires a large amount of heat inputReaction quickly fouls the catalyst (SiO2/Al2O3) with a coke covering on the catalytic surfaceCoke burned off exothermically in a regeneratorRegeneration provides heat for cracking process
12 Hydroprocessing Two steps: hydrotreating & hydrocracking Hydrotreating (hydrogenation)- increases saturation without breaking moleculeHydrocracking- breaks molecule into smaller molecules in the presence of a metal catalyst.Hydrocracking requires more heat and pressure than hydrotreating
13 Formation of Oxygenates Gasoline additives intended to reduce CO emissions (Reformulated gas)MTBE (methyl tert-butyl ether) is produced in refineries where isobutene is produced via cracking.
14 Advantages of Petroleum Easily transported liquidPetroleum fuels are quite cleanS & metal contaminants remain in refinery residue
15 Disadvantages of Petroleum Oil SpillsFragile coastal ecosystems at risk from oil tanker and oil rig spillsa significant amount of petroleum enters marine environment via natural seepage at continental marginsnatural hydrocarbons metabolized by microbesOil removed by microbes, evaporation and photo-oxidation processes
16 Disadvantages of Petroleum EmissionsFossil fuel combustion yields CO2 (greenhouse gas)Gasoline releases 33% more CO2 than natural gas (coal 60%>gasoline)NO is produced form N2 and O2 in an internal combustion engine (energy for this process obtained from the exothermic combustion of the gasoline)
17 Advantages of Natural Gas Clean fuel requiring little processingEasily transported via pipelinesCO2 emission per unit of energy lower than other fossil fuelsUnburned molecules released into the atmosphere contribute less to smog formation than gasoline moleculesmethane’s single C is reactive than carbons of longer hydrocarbon chains
18 Disadvantages of Natural Gas Requires high pressures or low temperatures to compress into a volume suitable for applications such as automotive transport.An unburned CH4 molecule is 20x more potent than a CO2 molecule as a greenhouse gas .Methane’s unreactivity results in a long atmospheric lifetime.
19 Advantages of Coal Large resource base Relatively cheap to mine and transport by rail
20 Disadvantages of CoalTransportation usage ended when diesel replaced the steam locomotive
21 Disadvantages of CoalLow C/H ratio results in more CO2 production per energy unit than other fossil fuelsSO2 & NO emissions from power plants a primary source of acid rain. Amount of SO2 & NO vary with the type of coal.