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25sec5

  1. 1. 25.5 Hydrocarbons from Earth
  2. 2. Natural Gas <ul><li>Fossil fuels provide much of the world’s energy </li></ul><ul><li>Natural gas and petroleum contain mostly the aliphatic (or straight-chain) hydrocarbons – formed from marine life buried in sediment of the oceans </li></ul><ul><li>Natural gas is an important source of alkanes of low molecular mass </li></ul>
  3. 3. Natural Gas <ul><li>Natural gas is typically: </li></ul><ul><ul><li>80% methane, 10% ethane, 4% propane, and 2% butane with the remainder being nitrogen and higher molar mass hydrocarbons </li></ul></ul><ul><ul><li>also contains a small amount of He, and is one of it’s major sources </li></ul></ul>
  4. 4. Natural Gas <ul><li>Natural gas is prized for combustion, because with adequate oxygen, it burns with a hot, clean blue flame: </li></ul><ul><ul><li>CH 4 + 2O 2  CO 2 + 2H 2 O + heat </li></ul></ul><ul><li>Incomplete burning has a yellow flame, due to glowing carbon parts, as well as making carbon monoxide </li></ul>
  5. 5. Petroleum <ul><li>The compounds found in petroleum (or crude oil) are more complex than those in natural gas </li></ul><ul><li>Usually straight-chain and branched-chain alkanes, with some aromatic compounds also </li></ul><ul><li>Crude oil must be refined (separated) before being used </li></ul>
  6. 6. Petroleum <ul><li>It is separated by distillation into fractions, according to boiling pt. </li></ul><ul><li>Fractions containing higher molar mass can be “ cracked ” into more useful shorter chain components, such as gasoline and kerosene </li></ul><ul><ul><li>involves catalyst and heat </li></ul></ul><ul><ul><li>starts materials for plastics and paints </li></ul></ul>
  7. 7. Coal <ul><li>From huge fern trees and mosses decaying millions of years ago under great pressure of rocks / soil. </li></ul><ul><li>Stages in coal formation: </li></ul><ul><li>1. Peat - soft, fibrous material much like decayed garden refuse; high water content. After drying will make a low-cost, smoky fuel </li></ul>
  8. 8. Coal <ul><li>2. Lignite - peat left in the ground longer, loses it’s fibrous texture, and is also called brown coal </li></ul><ul><ul><li>harder than peat; higher C content (50%); still has high water content </li></ul></ul><ul><li>3. Bituminous , or soft coal- formed after more time; lower water content, higher C content (70-80%) </li></ul>
  9. 9. Coal <ul><li>4. Anthracite , or hard coal </li></ul><ul><ul><li>carbon content exceeding 80%, making it an excellent fuel source </li></ul></ul><ul><li>Coal may be found close to the surface (strip-mined), or deep within the earth </li></ul><ul><li>Pollutants from coal are common; soot and sulfur problems </li></ul>
  10. 10. BIG BRUTUS Dragline used to remove the overburden of a strip mining coal field near West Mineral, Kansas Note the man standing beside it
  11. 11. Coal <ul><li>Coal may be distilled for many products </li></ul><ul><ul><li>coal gas, coal tar, coke, and ammonia </li></ul></ul><ul><ul><li>further distilled into benzene, toluene, naphthalene, phenol- the aromatics </li></ul></ul><ul><ul><li>Coke is almost pure carbon; produces intense heat and little or no smoke, thus used in industrial processes </li></ul></ul>

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