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What is special about oil?

  1. Jan 11, 2010 #1
    What is so special about oil that it is used for
    - energy generation
    - plastic production
    - ...?

    What are possible replacements for oil as it is used today?
     
  2. jcsd
  3. Jan 11, 2010 #2

    mgb_phys

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    It's rather conveniently liquid and there is loads and loads of it.

    Coal and gas
     
  4. Jan 11, 2010 #3

    russ_watters

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    1. It burns. Pretty well.
    2. It contains carbon and forms long molecular chains.
     
  5. Jan 11, 2010 #4
    But what is "special"? What does oil have that not many other material have?
     
  6. Jan 11, 2010 #5

    mgb_phys

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    You mean what's special about oil as a source of hydrocarbons, or whats special about hydrocarbons?
     
  7. Jan 11, 2010 #6
    I dunno. How does oil compare to rocks?
     
  8. Jan 11, 2010 #7
    Basically which properties does oil have that you wouldn't find in any other substance.
     
  9. Jan 11, 2010 #8

    russ_watters

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    These questions are way too vague. One of thousands of possible answers to #1:

    Oil burns, water doesn't.

    If you can't be more specific, you may want to pick up a chemistry or chemical engineering textbook to start reading through.
     
  10. Jan 11, 2010 #9
    You know, Gerenuk. At first I thought you were messing with us. Now I think you are asking "what are the values of oil, and how can these values be replaced?".

    Am I wrong?
     
  11. Jan 12, 2010 #10
    In my view people just have not understood the question. They say oil burns. Then I could say, "Well, wood also burns so just being inflammable is no special".

    The question which properties does oil have that no (or hardly any) other substance has?

    A good answer probably starts with
    "Oil releases more energy when being burned than most other materials and plastics can be made from oil since only oil [...] Al these properties together can be found only in oil"
     
  12. Jan 12, 2010 #11
    But you still haven't specified what properties you're looking for!

    Unless your answer is something like magic faeries, the question is still too vague.
     
  13. Jan 12, 2010 #12
    Just any properties you can think of. Anything that distinguishes oil as a whole from all other materials.
     
  14. Jan 12, 2010 #13
    Its a hydrocarbon.
     
  15. Jan 12, 2010 #14
    Hmm, maybe I don't know enough about the chemistry of nature.

    Are there no other hydrocarbons in nature?
    And if there are, why don't they substitute oil?
    Isn't there a lot of hydrocarbons in plants?
    How does oil take a special position?
     
  16. Jan 12, 2010 #15
    Im sure there are many hydrocarbons existing in nature but they don't exist in the quantities that oil exists in. Remember oil is the derivative of plant and animal matter over a long period of time.
     
  17. Jan 12, 2010 #16
    Thanks. That sounds like an answer I was looking for.
    So it's about being hydrocarbon that is treated in a special way (long time) and quantity matters, so that only oil is left.

    What does the "special treatment" over millions of years do to hydrocarbon to make it unique?
    Why can we not use normal plants for burning/plastics?

    And the continuation question is:
    What is most likely to be able to substitute oil? (for burning, plastics etc.)
     
  18. Jan 12, 2010 #17

    mgb_phys

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    They burn, both the ingredients - carbon and hydrogen burn very well, so they are a good source of energy. But so is coal and natural gas. It's just a little more convenient to have it as a liquid.

    Carbon forms a lot of compounds (>6 million?) so hydrocarbons are very useful in chemistry to make plastics etc. There are other sources of carbon (coal) that you can make into a hydrocarbon or you can turn carbo-hydrates (from living plants) into hydrocarbons. But this extra step costs time/money/energy
     
  19. Jan 12, 2010 #18
    So it's the reaction to CO2 and H20 that matters for burning?

    So in plants there are carbo-hydrates and we need hydrocarbons instead? This conversion is costly? Are we effectively collecting the energy that was stored (in this process) over million of years by applying pressure on the sealed plants?

    Are there no hydrocarbons in nature that we can extract? Are there any at all without this conversion "carbo-hydrates -> hydrocarbon"?
     
  20. Jan 12, 2010 #19
    Crude oil can be easily processed into a variety of fractions (through "fractionation") into mostly, simply connected oxygen-free hydrocarbons, the paraffins, ranging from C=5 to C=40 in length.

    For fuel, it is easily "cracked" to yield higher proportions containing weights around C=8. Gasoline has mostly octane, or there abouts. Gasoline is a high density energy source in a liquid form convenient for storage, delivery and conversion. Heavier fractions can be used for jet fuel and fuel oil. Half the energy source doesn't require storage, but comes out of the air, which is readily available.

    Most synthesis of plastics, drugs, dyes and other organic chemical compounds, require as precursors, the shorter hydrocarbons I think, so that natural gas is probably also a source. You could look this up as easily as I, I think. In any case one would want uniform, short molecules that are oxygen-free for the most part.
     
    Last edited: Jan 12, 2010
  21. Jan 12, 2010 #20

    mgb_phys

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    Yes, you can also burn coal but then you only get CO2 so you get a little less energy / ton.

    You are using the pressure that has driven off the water and most of the none carbon or hydro-carbon. So you can burn trees but they contain a lot of empty space and a lot of water and a lot of oxygen that you can't burn. Coal is just the carbon part of trees.

    You can extract oils from plants (or whales) but running a car on olive oil is expensive.
    You can use bacteria to convert plant carbo-hydrates into diesel or you can let millions of years of heat and pressure do it for you.
    It's a little more practical to use plants as a feedstock for certain plastics.
     
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