DFliyerz
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Demethylation of Xylene to Toluene/Benzene
Lately, I've noticed that most hardware stores have simply stopped carrying toluene, instead opting for a mixture of xylene isomers with a little
ethylbenzene. However, while looking at some patents regarding the demethylation of aromatic hydrocarbons, I noticed one specifically on demethylating
xylene to toluene/benzene. The temperatures required aren't particularly high, and the catalyst is fairly simple. Additionally, the boiling points of
benzene, toluene, and ethylbenzene are different enough that they could be separated by either fractional or perhaps even simple distillation. So,
what do you guys think about this idea?
Link to the patent: http://www.google.com/patents/US2786876
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Hellafunt
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This doesnt address your question, but I wanted to throw this out there. My local hardware store stopped displaying toluene, and I thought they had
stopped carrying it. Actually, they just stopped displaying it, and it is available if one asks for it. Maybe this can be of help to someone.
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Loptr
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Quote: Originally posted by Hellafunt  | | This doesnt address your question, but I wanted to throw this out there. My local hardware store stopped displaying toluene, and I thought they had
stopped carrying it. Actually, they just stopped displaying it, and it is available if one asks for it. Maybe this can be of help to someone.
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I would imagine that would only be available until the stock runs out.
Would you mind stating in what country you reside, Hellafunt? I know here in the USA, or at least my area, toluene is readily available.
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Hellafunt
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i live in the good ole USA, in Washington State. I didnt infer that they were just running out the stock on hand, but it could be. This was at a local
chain. The big box hardware stores near me have stopped carrying toluene, although a certain chain painting store still has it.
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Dr.Bob
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The interconversion of aromatics is done in the gasoline industry to create higher octane additives (xylene:toluene:benzene have octane ratings of
about 120:110:100), so mostly that type of chemistry is used to alkylate benzene to the more preferred xylene to boost octane ratings. Since xylene
likely is even safer (by some toxicity measure) than toluene, that may be part of it. But it would be very hard and cost inefficient to make toluene
from xylene. If you look around, I can't imagine that you can't find a source of toluene. It is found in many other things. Do a search for
toluene in the forum search engine or in google along with "sciencemadness" and you will find many threads on it. Some will be useful. Plus the
chemicals thread that is at the top of the apparatus and reagents section.
[Edited on 17-3-2015 by Dr.Bob]
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Dr.Bob
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I love the apparatus in IrC's patent, looks like something the home chemist could build in about 20 years with enough money. Almost Rube
Goldbergian.
But a quick glance at the original patent shows how practical this is for home use:
" A specific object is to provide a process for producing benzene from methylbenzenes, such as toluene and xylenes, by contacting the methylbenzene
with a bead-form silica-alumina catalyst, in the presence of hydrogen under pressure and at specific critical temperatures .... between
about 900 F. and about 1200" F., for a contact time of between about 40 seconds and about 1000 seconds, and in the presence of hydrogen gas under
superatmospheric pressures. "
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Loptr
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| Quote: Originally posted by DFliyerz | Lately, I've noticed that most hardware stores have simply stopped carrying toluene, instead opting for a mixture of xylene isomers with a little
ethylbenzene. However, while looking at some patents regarding the demethylation of aromatic hydrocarbons, I noticed one specifically on demethylating
xylene to toluene/benzene. The temperatures required aren't particularly high, and the catalyst is fairly simple. Additionally, the boiling points of
benzene, toluene, and ethylbenzene are different enough that they could be separated by either fractional or perhaps even simple distillation. So,
what do you guys think about this idea?
Link to the patent: http://www.google.com/patents/US2786876 |
Another idea is for members that live in the same country are proxy purchases. For a fee and an additional shipping/handling charge, a reputable
member that has access to cheap chemicals that are available locally to them could purchase quantities of a requested chemical, and then ship it to
the purchaser.
It should be expected the shipping should include a material fee that would cover the purchase a combination of the follow hazmat shipping supplies.
http://www.uline.com/Product/Detail/S-14748/Sorbents-and-Spi...
http://www.uline.com/BL_5304/Paint-Can-Shippers?keywords=haz...
http://www.uline.com/BL_5303/Paint-Cans-Pails-and-Rings?keyw...
http://www.uline.com/BL_5306/F-Style-Metal-Shipper-Kits?keyw...
http://www.uline.com/BL_5305/Gallon-Jug-Shipper-Kits?keyword...
A lot of the problems that members have with accessing things like sulfuric acid, toluene, mek, acetone, hydrochloric acid, etc., etc., could easily
be solved by sourcing through other members.
[Edited on 17-3-2015 by Loptr]
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IrC
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| Quote: Originally posted by Dr.Bob | I love the apparatus in IrC's patent, looks like something the home chemist could build in about 20 years with enough money. Almost Rube
Goldbergian.
But a quick glance at the original patent shows how practical this is for home use:
" A specific object is to provide a process for producing benzene from methylbenzenes, such as toluene and xylenes, by contacting the methylbenzene
with a bead-form silica-alumina catalyst, in the presence of hydrogen under pressure and at specific critical temperatures .... between
about 900 F. and about 1200" F., for a contact time of between about 40 seconds and about 1000 seconds, and in the presence of hydrogen gas under
superatmospheric pressures. " |
I posted it so people could look at the chemistry/method involved in the patent, specifically the catalyst.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Loptr
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| Quote: Originally posted by IrC |
I posted it so people could look at the chemistry/method involved in the patent, specifically the catalyst.
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Are you referring to this mention.
| Quote: | | aluminum oxide forms, such as bauxite, acid-treated bauxite, aluminum hydrate, alumina gel, activated alumina, partial or completely peptized aluminum
or alumina gels, slilica-alumina gels, and hydrofluoric acid-treated alumina together with 1 to 50% by weight of an oxide or a sulfide of a metal of
the IV, V, VI, VIII groups of the periodic system. |
| Quote: | | The catalyst in reaction zone should be one which promotes catalytic reforming. |
What exactly does this mean, catalytic reforming?
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Loptr
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| Quote: Originally posted by IrC | I am not the author of the patent, I suggest common sense would indicate your question should be directed to the patent recipient. It was one of the
patents in the references of the patent posted by the OP. Some people are able to look at the work of others and glean ideas from it. Which was the
point of my post.
Preferring not to listen to two people complain about it I deleted the post.
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IrC, I was actually asking you a question about it. Not complaining about a thing. I briefly browsed through the patent, found what I thought was the
catalyst information you were referring to, and pasted in my comment so that others could see the mention without having to grab the patent first.
Then I asked what is catalytic reforming was, as I am a software developer, and not a real chemist by any means. My specialty is elsewhere, and I was
hoping you could clear up the concept for me.
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IrC
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I am not a chemist either. I have been interested in the subject and doing experiments for decades when the need for something else I was working on
required it. So I cannot enlighten you about it other than to say studying the catalysts mentioned seemed worthwhile.
I merely saw a patent reference studying the OP's posted patent which I thought might be useful to mention. Then I read:
| Quote: Originally posted by Dr.Bob | I love the apparatus in IrC's patent, looks like something the home chemist could build in about 20 years with enough money. Almost Rube
Goldbergian.
But a quick glance at the original patent shows how practical this is for home use:
" A specific object is to provide a process for producing benzene from methylbenzenes, such as toluene and xylenes, by contacting the methylbenzene
with a bead-form silica-alumina catalyst, in the presence of hydrogen under pressure and at specific critical temperatures .... between
about 900 F. and about 1200" F., for a contact time of between about 40 seconds and about 1000 seconds, and in the presence of hydrogen gas under
superatmospheric pressures. " |
Reading "something the home chemist could build in about 20 years with enough money" "Almost Rube Goldbergian" and "But a quick glance at the
original patent shows how practical this is for home use" it appeared to me to be sarcasm, in effect insulting me for posting the patent.
So this was already on my mind when I read your post. Not realizing it was an honest question it seemed to be yet another member going after me for
trying to be helpful and for not being a professional chemist well grounded in theory. Sorry if I was wrong my irritation stemmed from the perception
of an atmosphere which would cause people not well grounded in chemistry to be hesitant to speak, in effect squashing the desire for this site to be a
place where ideas can be freely exchanged without fear of repercussion.
"Science is the belief in the ignorance of the experts" Richard Feynman
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Loptr
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I wouldn't take what Dr.Bob said to heart.
I think that if it was stated that yes, these are extreme reaction conditions, and likely not attainable in the amateur setting, but that it might be
possible to take this and the catalyst as an example to go on, so that a more amateur friendly procedure might be derived, that it might have been
better received.
[Edited on 17-3-2015 by Loptr]
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Bert
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Gentlemen, please be excellent to each other, and keep any speculations limited to the chemistry and engineering, rather than intended degrees of sarcasm or
rancor!
[Edited on 17-3-2015 by Bert]
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
that way.”
2. List any points of agreement (especially if they are not matters of general or widespread agreement).
3. Mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
Anatol Rapoport was a Russian-born American mathematical psychologist (1911-2007).
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subsecret
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Here's a paper that details the movement of alkyl groups around a benzene ring, and sometimes even de-alkylating it to benzene itself. Aluminum
chloride and HCl are used in the reaction. The yields are not high, however.
Attachment: Migration of Alkyl Groups in Benzene Nucleus.pdf (287kB)
This file has been downloaded 414 times
Fear is what you get when caution wasn't enough.
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Dr.Bob
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Sorry if I offended anyone. I am a scientist, and like Sheldon, sometimes look at the science, not the people.
My point was that many patents are often purposefully vague about what they are actually describing, and often use equipment that is not suitable for
home chemistry. If you ask a question about a patent or catalyst without really knowing what it is, that leaves a huge uncertainly as to what answer
might be useful. Also, people here often post patents and ask if the method would be useful for making something at home, and I think you should
look at it, and if it mentions anything about high pressure hydrogen, then it is not likely a good candidate for home chemistry.
Books like Vogel, Feiser, and Org Synth are much more likely to have useful routes to chemistry than can be done at home, compared to a large majority
of industrial scale petrochemical patents, many of which are hard to scale down. That is not to say that a patent cannot be used at home, but if it
does not contain experimental procedures with specific examples using chemical conditions achievable in a lab, then it won't likely be useful at home.
And the word "catalytic reforming" means to take a mixture of compounds and transfer some atoms between the constituents such as to change the
equilibrium percentages of the components. For instance, in most cases, a mixture of mostly benzene is reformed by adding methyls to form a mixture
of benzene, toluene, and ortho, meta and para xylenes. Or straight chain hydrocarbons are reformed to branches isooctane like molecules to increase
octane ratings of gasoline. The key to these reactions is that they are designed for complex mixtures, most often, in the petrochemical world, so
they, in general, are not as suitable for making specific single compounds, but for mixtures with certain characteristics, like a high octane rating,
a certain boiling point, or the like.
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