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Author: Subject: toluene --> benzaldehyde
blogfast25
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[*] posted on 30-1-2016 at 09:36


I'm certainly interested in your results.

You don't seem to have a lot of oxygen in your system though: maybe about 0.008 mol of O2? Or am I missing something?




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[*] posted on 30-1-2016 at 09:52


Where is the excess air (N2) vented?

Did you wind the kanthal or did you buy/salvage it as a coil?

Do you have a reference for this method or is it your invention?

;)




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[*] posted on 30-1-2016 at 11:13


blogfast you are right, the O2 concentration in the reactor is very low. 10ml of air to 3-5 drop of toluene, but this is exactly hat you want, too much O2 and the CHO goes to COOH or even CO2 & H2O

Magpie, of course it was salvaged, it is from an old air heater, the kanthal wire is so old that I tried to wind out the other one and it broke in many points so I just left this one as it was.

Actually I did not find any ref for continuous recycling lab procedure, all the patents around describing yield based on one pass due to high conversion rates, also note that every patent describes net oxidizing air+toluene mixtures, so in my case benzoic acid formation should not be significant, still... copper can facilitate in its formation even in net reducing mixtures because its too strong catalyst if you only want aldehyde. Molybdenum trioxide would be much better, or tungsten.

So I have many ideas if this experiment fails.
1, Decrease the toluene flow and ramp up temps in the current design
2, Increase toluene flow and ramp down temp... you never know:))
3, oxidation with heated copper filament
4, oxidation with heated tungsten filament
5, oxidation with heated molybdene filament

The N2 exhaust point is at the end of the condensor, you can see it in the first picture, it is the highest point of the setup.

[Edited on 30-1-2016 by Jimmymajesty]
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[*] posted on 31-1-2016 at 13:42


After the run, I let everyting cool, then take out 5ml yellow toluene, shook with 25ml water, then I let it settle and smelled the watery phase to find out there is hardly any benzaldehyde in it, as a result I bypassed "Idea 1 and 2".

I did a run today by "idea 3" but with a vertical reactor design.
After 1hr I sampled it and the presence of benzaldehyde was evident.

So I am gona run the vertical reactor for a whole weekend sometime.
Damn I wish I had more time for chemistry...
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[*] posted on 12-3-2016 at 10:23


Hi,

I gave it a decent try today. The toluene vapors went through a column which provided some degree of separation. Air inlet connection, then raschig packing to help air mix into the toluene vapor, then kanthal wire wound around a mica sheet and copper oxide pellets (see pic). After the reaction all condensable liquid went back into the flask. This was basically the setup used at my first attempt but an improved version.

I added 50ml water to the toluene to increase the vapor pressure of the benzaldehyde after the reaction zone. I gradually adjusted the voltage on the kanthal to intitiate self pyrolysis of toluene, then decreased it a lil bit and adjusted the air inlet to be ~2ml/sec.

I sampled the condensed liquids from time to time shook it with water then smelled the watery phase. I went from the above condition till the kanthal was orange (~5sampling) to find out there was not any benzaldehyde in the condensate.

Now I am kinda puzzled since this means that a simple ethanol => acetladehyde setup with brute force produces more benzaldehyde than the current one...?! I do not really know how to improve from here. I will sample the watery phase in the flask when it cools, but I am skeptic that it will contain any benzaldehyde.

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[*] posted on 13-3-2016 at 16:50


So... I also tried out copper plated kanthal wire and manganin as the heating element. Chunks of diesel catalytic converter and copper sponge as the catalyst. Countless air and wattage settings but not a single molecule of benzaldehyde, during the 12hours torturing the initially yellow toluene turned into a somewhat viscous black crap, so I managed to find a new way to turn half a litre toluene to useless crap.

I took a picture to show how hard I kicked the toluene molecules in the ass, there is black tar coming down as condensate (bottom-right side small black bulb). This run was with diesel catalyst chunks, the condenser filled up with uncodensable myst which I believe was benzoic acid, still no benzaldehyde...

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[*] posted on 15-3-2016 at 05:30


Benzaldehyde is sensitive to auto-oxydation into benzoic acid

Also you may request this document in document request section:

THE PYROLYSIS OF BENZALDEHYDE AND OF BENZYL BENZOATE

Charles D. Hurd, C. W. Bennett
J. Am. Chem. Soc., 1929, 51 (4), pp 1197–1201
DOI: 10.1021/ja01379a030
Publication Date: April 1929
First page




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[*] posted on 15-3-2016 at 17:19


Quote: Originally posted by Jimmymajesty  
Magpie, is hiring a glassblower really such big a deal? In every town there are at least two, they always complaining not to have enough work so the one I usually go to quite happy when he sees me.

It can be. I'm in a depressed part of the us and a lot of glassblowers have gone under. To make matters worse the local U is a private rich kids school and they don't repair any glassware and don't have very creative chemists. The guy I have to use is 60 miles away and spends a lot of his time on ebay.
The other guy does quartz for the med school and charges too much for simple mods and repairs.




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[*] posted on 21-3-2016 at 13:53


I have other ideas that I want to try out like, oxidizing the toluene with NO2 I just have to take a break when handling these aromatics, gas mask or not I just can not avoid getting some when handling it... also when I try to identify the product my only instrument is my nose and my gf smelled something gasoline-ish in my breath when I spent the whole day in my lab... my fume hood sucks like a hooker since it can only accomodate a test tube confortably, so most of my time goes with silver recovery from relays and such benigh things.

As for the glassblower mine just diagnosed with cancer so I do not really know who to turn to if he can not work anymore... so I feel your situation. I always use the local flea market search engines with the words "lab, labware, lab instrument, flask, chemistry, chemical, etc. from week to week there is a hit and usually the seller do not know what they are selling so the glass comes fairly cheap I bought this on the weekend for 4USD do not know what to do with it but it sure looks lovely isnt it?:)

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[*] posted on 19-5-2016 at 12:12


Which metal can you use instead of lead?
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[*] posted on 19-10-2016 at 14:06
Air oxidiser


I have wanted a way to make p tolualdehyde fairly easily, this post using air oxidation schemes sounded attractive as a semi industrial route. What I found was that there are limitations to the air oxidation schemes. Perhaps this might be useful in some way for the production of the TM on this forum.

"The autoxidation of p-xylene is known to proceed through a free radical process. The Mn(III) and Co(III) metals alone are not strong enough oxidizers to start the radical chain reaction, but instead initiate it by forming bromine radicals from the ions in solution. These bromine radicals then decompose hydroperoxides that are ligated to the metals as well as abstract hydrogens from the methyl groups on p-xylene to form free radicals and propagate the reaction. The following are the proposed initiation, propagation and terminations steps for the first of four oxidations involved in the autoxidation:" [https://en.wikipedia.org/wiki/Terephthalic_acid]

An initial study was run using a heated catalyst surface with different transition element oxides and a promoter. p-xylene vapour and air were passed through the reaction zone and condensed then returned to the flask. Runs were about 6hrs each with 50mls p-xylene, and the flask then distilled to observe the quantity and nature of the residue. The quartz reactor (from an old heater) has a nichrome filament inside and a glass fiber soaked in catalyst wrapped on the outside and held in place with nichrome. The catalyst surface reached a maximum temperature of 350C.

In all cases only a very small amount of oxidised residue was formed, 5ml at the most, catalysts tested were- in order of perceived activity: V2O5/FeCl3, Co2O3/FeCl3, Ni2O3/FeCl3, Fe2O3/FeCl3, SnO/FeCl3.

The quick and dirty conclusion is that surface areas need to be huge in order to generate any meaningful quantity in a reasonable time. Optimising the choice of catalyst/promoter and cleaning the inlet air to prolong the catalyst activity is a secondary concern with regards to the practicality of the scheme.


V2O5 sml.JPG - 173kB SchemeSml.JPG - 94kB ReactionZoneSml.JPG - 160kB ReactionSml.JPG - 151kB
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[*] posted on 12-12-2016 at 18:17


Quote: Originally posted by Jimmymajesty  
I have other ideas that I want to try out like, oxidizing the toluene with NO2 I just have to take a break when handling these aromatics, gas mask or not I just can not avoid getting some when handling it... also when I try to identify the product my only instrument is my nose and my gf smelled something gasoline-ish in my breath when I spent the whole day in my lab... my fume hood sucks like a hooker since it can only accomodate a test tube confortably, so most of my time goes with silver recovery from relays and such benigh things.

As for the glassblower mine just diagnosed with cancer so I do not really know who to turn to if he can not work anymore... so I feel your situation. I always use the local flea market search engines with the words "lab, labware, lab instrument, flask, chemistry, chemical, etc. from week to week there is a hit and usually the seller do not know what they are selling so the glass comes fairly cheap I bought this on the weekend for 4USD do not know what to do with it but it sure looks lovely isnt it?:)


That's a sort-of steam-distillation bulb/head. I've seen it in Vogel's OChem. Basically, you stick the long part into a flask where the boiling solution surrounds the test-tube-like bulb with the glass tube inside. The vapors go down into the 'test tube' via the curved glass tube, and bubble through there (which should already contain the liquid you are to steam distill). They exit containing what is to be stilled over with the vapors at the top ground glass port. The stopcock is to ensure that the process of cooling doesn't suck the compound you are steam distilling into the solvent (or vice versa, I forget).




My write-ups are on here...
http://www.MeltThe.Ga or http://ptp.x10.mx
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[*] posted on 6-5-2017 at 10:41


Could you use nitric acid as an oxidiser?
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