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11.8 – NOTES Altering Fuels

11.8 – NOTES Altering Fuels. B.9 Altering Fuels The gasoline fraction only represents 18% of the total crude oil (5-12 carbons in a chain) Using certain techniques can get up to 47% of crude oil. Cracking

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11.8 – NOTES Altering Fuels

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  1. 11.8 – NOTESAltering Fuels

  2. B.9 Altering Fuels • The gasoline fraction only represents 18% of the total crude oil (5-12 carbons in a chain) • Using certain techniques can get up to 47% of crude oil

  3. Cracking • Taking large chain hydrocarbons and breaking them into smaller chains, using catalysts and heat

  4. Catalyst • Something that increases the speed of a reaction and lowers the temperature needed to start the reaction • They are not used in the reactions – they are not part of the product • Allows the burning of fuel to be cracked more efficiently because it takes place at a lower temperature (500 C rather than 700C), which needs less energy

  5. A 16 carbon chain could be made into two 8 carbon chains • Can produce molecules of up to 14 carbons through cracking • C5-C12 are used in gasoline

  6. Octane rating • Gas is made of mostly straight chain alkanes • Premature burning results in pinging/knocking • Branched chains don’tknock as much • Octane rating tests efficiency • Free running and under a load and then the average is taken • Higher octane numbers result in betteranti-knock characteristics • Prior to the 70s, lead was added to increase octane rating • Tetraethyl lead ((C­2H4)4Pb) • Why was lead banned from fuels? • Bad for the environment, can cause many health problems

  7. Oxygenated fuels • Fuels that have extra C, H and O to enhance octane • Less energy is delivered, but the octane increases and reduces pollutants

  8. Types of addititives to make oxygenated fuels • Methanol • Formula: CH3OH • Made from: natural gas, coal, corn, wood • Structure:

  9. Ethanol • Formula:C2H5OH • Gasohol - 10% ethanol, 90% gasoline • Can usually run in cars without modifications • Structure:

  10. MTBE- methyl tertiary-butyl ether • Has an octane rating of 116 • Most common additive in the 1990s • Contaminates groundwater/drinking supplies • Results in unpleasant taste or odor in drinking water • Under consideration to reduce/ban

  11. Other ways to boost octane rating • Alter the structure by turning straight chains to branched chains • Isomerization • Conversion of straight chain hydrocarbons into branched chains • Newly made branched chains are mixed with cracked hydrocarbons to produce high quality fuel • One of the largest problems with isomerization is the high cost • Isomerization Graphic:

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