Lesson 5 Notes

Lesson 5 Notes - Lesson 5 Learning Objectives Your success...

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Lesson 5 Learning Objectives Your success in this lesson will be based on your ability to do the following; Articulate how crude oil is transformed into fuels Discuss fuel changes for vehicle pollution reduction Discuss fuel chemistry, identify chemical species Calculate molecular weights Articulate weather impacts on supply and demand Discuss SPR issues (security) Articulate price variability Crude Quality Issues Crude oil is a highly variant natural resource. The quality ranges are similar to coal and depending on the maturation of the crude the quality can be high or low (younger crude's are of lower quality). One of the first indications of quality is color. But don't take my word for it - take Chevron's. The variations in oil color can be dramatic, and very indicative of the quality of that crude. Not all crude oil is black - higher quality oils can be a golden or amber in color. In the U.S., about 50% of the oil is converted into gasoline. So an oil that produces a higher % of gasoline "cuts" is more desirable and have a higher quality oil. Viscosity is the resistance to flow. Do not use the term "Thickness" which is a length measurement. The higher the viscosity the slower the liquid will flow and the lower the quality. The viscosity process is a measure of quality, because the chemical structure of the crude influences its flow ability. Longer chain molecules for example are harder to flow than short chains because of non-bonding interactions. If you have had any chemistry you will recall ionic (type of bonding in salt crystals) and covalent bonding (the type of bonding between 2 carbon atoms). Those are bonding interactions. There are several non-bonding interactions that occur which attract (and repel) molecules. It is the relative strength of these non-bonding interactions that influences the resistance to flow. For coal we used the correct terminology, which was ultimate analysis. For crude, that terminology we use is Elemental Analysis. Crude oil is complex, it contains C, H, N, S, O, and metals too. But the bulk of the composition is C and H, the rest being the N, S, O and metals. S is a good indication of the quality of the crude because as the oil is heated underground the weak S-C bond can break producing H2S (hydrogen sulfide gas). So, older crudes - higher quality - will have lower S content. Higher S crudes also cost more to process as S is a catalyst poison it has to be removed or the extensive catalysts used in the petrochemical industry would be damaged, as would your catalytic converter. The atomic H/C ratio is also an indicator of quality. Elemental Composition of Typical Crude: Carbon 84 - 87% Hydrogen 11 - 14% Sulphur 0 - 6% Nitrogen 0 - 1% Oxygen 0 - 2%
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Hydrocarbons are molecules that contain only the elements of carbon and hydrogen. These are the bulk of the crude oil. We find 4 types of chemical structure of hydrocarbon
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Lesson 5 Notes - Lesson 5 Learning Objectives Your success...

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