Uses Of Pitch And Asphalt

  1. 1. The problem statement, all variables and given/known data

    Here is question in objective form. I have tried answering it but am confused with the answer I got.
    Instruction: shade A if only IV is correct. Shade B if only I and III are correct. Shade C if only III and IV are correct. Shade D if I, II, III are correct. Shade E if only I, II, III and IV are correct.
    The question:
    pitch and asphalt are residual products from the fractional distilation of petroleum. These substances are used as I. protective coatings for road surfaces. II. binding agents for roofing materials. III. organic solvent. IV. catalyst cracking.
    If this problem is set before you, which of the options lettered A-E will you shade and why? Please explain in detail.



    2. Relevant equations

    No equation is involved.

    3. The attempt at a solution

    I know that pitch and asphalt are residual products from the fractional distilation of coal which can be used for the following:
    I. protective coating for road surfaces.
    II. binding agents for roofing materials.
    III. organic solvents.
    Because I read that from my chemistry text book. Since I have been reading my chemistry texts book, I have never came across any part where pitch or asphalt is used as a catalyst, talkless of catalyst for cracking or is there any?
    Judging from my statements above, I choose option I, II and III as correct for the uses of pitch and asphalt and IV not correct for the uses of pitch and asphalt, therefore wrong.
    The above is my own opinion, anyperson who has a contrary view to my opinion is free to come in let's discuss with the hope of arriving at the correct answer. Thank you as you forward in your replies.
     
  2. jcsd
  3. chemisttree

    chemisttree 3,723
    Science Advisor
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    Could IV have meant that asphalt was used in catalytic cracking? (Asphalt as substrate)
     
  4. No, it meant that asphalt was used as catalyst.

    Even if it meant that the asphalt is substrate which an enzyme is acting on, what then will you infer from my post?.
     
  5. NascentOxygen

    Staff: Mentor

    I doubt it. Almost certainly it is the tar and pitch that is being cracked into lighter compounds.
    Enzyme? Where was an enzyme mentioned? [​IMG]

    I would infer that you have a biology background. :wink:
     
  6. chemisttree

    chemisttree 3,723
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    Probably that it isn't too pressing. Eleven days is a long time to wait for an answer...
     
  7. Sorry, I mean to say catalyst.
     
  8. NascentOxygen

    Staff: Mentor

    Can you tell me, chikis, of an application where pitch is used as an organic solvent? (If that is indeed what you are saying.)
     
  9. I believe the asphalt can be distillated farther to get other high boiling solvents.
     
  10. NascentOxygen

    Staff: Mentor

    Okay. That's not how I would have interpreted the question, but I can see it may be interpreted that way. I understood the option as proposing that the tar itself is the solvent, not that a solvent can be derived from it.

    But let's look at IV. The Alaskan tar sands are being mined for their hydrocarbon content. The raw material (can it be called "tar") is being cracked for petroleum products. Is the process accurately described as catalytic cracking?

    If the two questions in color can be answered "yes", then I think we have to say IV is correct. (I'm using the terms tar, pitch and asphalt interchangeably, though maybe your course intends pitch and asphalt to be different from tar?)
     

  11. Can what be called tar. Please put question clearly. You mean the raw material, pitch and asphalt. If that is what you mean, then wait for sometime while I go find out and then come back and feed you with whatever information I had about what you asked.
     
    Last edited: Apr 6, 2012
  12. Tar is modified pitch obtained from the wood and roots of a pine tree by destructive distillation by pyrolysis.
    Remember pitch can be made from both petroleum products and plant products. Tar- like products can also be derived from petroleum. Tar is used mainly to describe pitch made from plant products but my question from begining of this thread is dealing with the type obtained from petroleum by defining it:
    There is no much difference in the nomenclature, "tar". The name tar, is just used to differenciate between the type made from plant products and the type made from petroleum, but in general, the both are collectively known as pitch.
    I hope I have answered the first part of the question, so wait patiently for the second part.
     
    Last edited: Apr 6, 2012
  13. NascentOxygen

    Staff: Mentor

    I'll try too. :smile:

    I'm referring to the stuff that is being dug out of Alaskan "tar sands". It is being converted to petroleum fuels. Is that stuff they are mining correctly (according to your definition) termed tar, though obviously mixed with soil?

    Believe it or not, I am still trying to help you arrive at the correct answer to your original question. :wink:
     
  14. Okay, then take a look at my reply below which I have posted previously in an attempt to give an answer to your question but reposted it for reference:
    tar is modified pitch obtained from the wood and roots of a pine tree by destructive distillation by pyrolysis.
    Remember pitch can be made from both petroleum products and plant products. Tar- like products can also be derived from petroleum. Tar is used mainly to describe pitch made from plant products but my question from begining of this thread is dealing with the type obtained from petroleum by defining it:
    There is no much difference in the nomenclature, "tar". The name tar, is just used to differenciate between the type made from plant products and the type made from petroleum, but in general, the both are collectively known as pitch.
    I hope I have answered the first part of the question, so wait patiently for the second part.
     
    Last edited: Apr 7, 2012
  15. NascentOxygen

    Staff: Mentor

    chikis, is the wording of the question your translation from another language? If so, can you reexamine the original question and see whether you have missed some subtlety in the part dealing with organic solvent?
    We both agree that I. and II. are correct.

    I can't think of any application where these heavy products are used as a solvent, so I say III. is incorrect. (Disclaimer: I'm not a chemist.)

    As I understand catalytic cracking, its whole purpose is to take the residual products from fractional distillation and break them down into shorter length molecules that when returned to the fractionation column will yield useful petroleum products. So IV. is definitely correct.
    I need an option giving a big ✔ to statements I,II and IV. There isn't one.

    Post Script: apparently it is not totally unheard of to use pitch as a solvent, so maybe III. can be considered not incorrect? http://www.sciencedirect.com/science/article/pii/0016236187900196 Perhaps the person who set you this question is a researcher in industrial chemistry?

    [​IMG]The nearest, most-correct option now looks like (E). :smile:

    PPS. I see you got a more complete answer in that other forum, where they likewise questioned what is implied by the "organic solvent" and "catalyst" answers.
     
  16. @NascentOxygen,
    which other forum are you refering to?
    Which other forum do you say that I got a more complete answer?
     
  17. Back to your second question
     
  18. Back to your second question:

    to answer that question, we need to understand what catalytic cracking is all about. Catalytic cracking is a process employed in petroleum refinery industry whereby complex hydrocarbon are broken into simpler molecule in order to increase the quality and quantity of more desirable products and decrease the amount of residuals.
    In cracking that involves the use of catalyst, some carbonaceous material (coke) are produced. The coke deposit on the catalyst and weakens it catalytic ability. The catalytic strenght of catalyst is reawakened (regenerated) by burning off the deposited coke with air blown into the regenerator. If the coke is burnt off then I don't see any of it help here. The catalyst used in cracking of hydrocarbon are zeolite, aluminum, hydrosilicate, bauxite and silica- alumina. Since pitch or asphalt was not mention in the list of catalyst, rather is burnt off, I see none of it use in catalytic cracking of hydrocarbon.
    I therefore dsmiss the idea that E is correct but accept the fact is only D that contain all the uses of pitch and alsphalt.
    Back to your question, "Is the process accurately described as catalytic cracking?"? The answer is yes because catalyst is used to facilitate such cracking process. I hope I have answered all your question in colour?
     
    Last edited: Apr 14, 2012
  19. NascentOxygen

    Staff: Mentor

    Hello chikis. I'm pleased to see you are still thinking about this problem, as I dislike leaving off when things are only half-finished. Back to your original question:
    I should have asked right at the start: have you translated this into English from another language? If so, can you go back to the original question and take a closer look at it and verify that the translation is precise. Better still, can you also post the original here in its original language?

    I say this because the question as you present it is not grammatically correct. This raises doubt in my mind that we can rely on subtle shades of meaning to count or discount any options. When the question is not correct, what chance do we have of getting the answer correct? [​IMG]

    In my mind I am confident that (E) is intended to be the correct answer, because it is very rare for a physical sciences examiner to set a multichoice question that tests the student's grasp of grammar and not of science.
    In this case it may be the examiner who scores a FAIL—for grammatical errors.
     
  20. Can you point out the gramatical errors? Let's see how we can fix it.
     
  21. you choose E as the correct answer, fine. Option E and D are almost the same if not for the IV, which described pitch and asphalt as catalyst for cracking. Now, if you are very confident that E is the correct answer, can you give one of the area where either pitch or asphalt or both are being used as catalyst in cracking of hydrocarbon and then explain?
     
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