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Author: Subject: Demethylation of Xylene to Toluene/Benzene
DFliyerz
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[*] posted on 16-3-2015 at 09:56
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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[*] posted on 16-3-2015 at 11:35


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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[*] posted on 16-3-2015 at 11:48


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.


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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[*] posted on 16-3-2015 at 13:10


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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[*] posted on 16-3-2015 at 16:24


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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[*] posted on 17-3-2015 at 05:34


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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[*] posted on 17-3-2015 at 06:09


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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[*] posted on 17-3-2015 at 07:36


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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[*] posted on 17-3-2015 at 07:44


Quote: Originally posted by IrC  


I posted it so people could look at the chemistry/method involved in the patent, specifically the catalyst.


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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[*] posted on 17-3-2015 at 10:29


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.


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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[*] posted on 17-3-2015 at 12:10


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.




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Loptr
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[*] posted on 17-3-2015 at 12:31


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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[*] posted on 17-3-2015 at 12:44


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]




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[*] posted on 17-3-2015 at 17:27


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 346 times





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[*] posted on 18-3-2015 at 05:40


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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