Organikum (Hive Bee)
10-02-02 18:52
No 363270
      TiO2 + UV for oxidation ?  Bookmark   

Has somebody applied such a catalytic oxidation system for example for benzaldehyde as product from the correspondending alcohol?

if yes, I would love to know how the catalyst has been applied, just mixed and stirred or suspended over a substrate? Has the TiO2 been activated somehow? How was the oxygen feeded to the reaction?

And of course: is this a feasible way to go at all for the advanced hobbyist?


~ Love is the law, love under will. ~
(Hive Bee)
11-06-02 08:47
No 376974
      I was working on this a few months ago, but I ...  Bookmark   

I was working on this a few months ago, but I came under some heavy scrutiny all of a sudden.  Had my house surrounded in fact.  So I never got to finish anything, but I have a book on green chemistry which I paid over $200us that has a moderately good writeup.

I will try to scan the reference, as well as one other on using Zeolites to catalize Tol->Benz oxidation.

I do remember that they were using flame deposition of a Ti salt on a polymer substrate as the physical catalyst.  They were bubbling O2, sorry I don't remember if any additional solvent was used.  I also remember that plenty of UV made a real difference to the reaction.

I intended to try suspending TiO2 in the tol, bubble O2, slam it way some MAD FUNKY UV radiation and see what happened.

I had one other odd idea, which seemed like it might be interesting...

If tol were evapped on a steam bath and then condensed above a reaction chamber

          | |
  Water  /| |\
  out   = | ||
         || ||
         || || -- Toluene condenses to
         || ||    drop onto catalyst
  Water = | ||
  in     \| |/
          | |
          | |     Toluene vapor passes from
          |  \   / boiling flask around column
          | |\\ /
          | | \\
         /|%|\ \\
         ||%|| ||
 UV   /  ||%|| ||  % Column packed with TiO2
Light -  ||%|| ||  % on polymer, carbon or something
      \  ||%|| ||   
         ||%|| ||
         \|%|/ ||
          | | //
          | |//
  Oxygen  |  /
  inlet->=  |
          | |     boiling flask
         /   \   /
        /     \ / 
       /       \
    ---|       |---
    |   \_____/   |
    |             |
      Steam Bath 

Toluene boils in the flask, passes mostly around the packed column, condenses and drips into a column packwith with a supported TiO2 catalyst.  O2 is passed in through a side adapter to bubble through the Tol and catalyst while being iluminated with intense UV from a mercury lamp.

When the tol exits the column, hopefully a portion has tol has oxidised to benz.  If so, then the benz would remain in the flask as the tol continued through the evap/condense/seep through catalyst cycle.  This would seem to be the likely outcome because benz, unlike tol, has a higher boiling point than H2O. 

So the benz would collect in the flask, and the flask would remain at the boiling point of tol until all the tol had been converted to benz(or something else), at which point the temp should rise even with the steam bath.  Since the benz would not continue cycling it should have a low likelyhood of being over oxidised to benzoic acid.  And a jump in the flask contents internal temp would be a good indicator of a nearly complete reaction.

I read of another reaction being done like this, acetone -> cloroaceton, I think.  But I have no references on whether it might work for tol->benz, but it seems reasonable from my feeble understanding of chemistry.

Let me know what you think,

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
(Hive Bee)
11-06-02 19:26
No 377086
      Nice idea  Bookmark   

If it really works like this and higher temperatures are not necessary, you could adapt a Soxhlet extractor, filled with the catalyst and irradiated with UV light. But for heating you should use an oil bath, as toluene boils at about 110 C...wink

Quidquid agis, prudenter agas et respice finem!
(Hive Bee)
11-07-02 18:54
No 377341
      I have a Sox... but the glass blocks most ...  Bookmark   

I have a Sox... but the glass blocks most UV(correct if wrong).  Also, I think Tol boils below H20.  That is why I went with steam.  Check that if you will, and so will I to make sure I not mistaken.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
(Hive Bee)
11-07-02 20:06
No 377357
      "Also, I think Tol boils below H20.  Bookmark   

"Also, I think Tol boils below H20.  That is why I went with steam.  Check that if you will, and so will I to make sure I not mistaken."

Nope, it boils slightly higher than water.

(Synaptic Self-Mutilator)
11-07-02 20:18
No 377361
      BP of toluene / water  Bookmark   

Water boils at 100C, toluene at 110.6C. The azeotrope of toluene and water that boils boil the BP of both.
(Hive Bee)
11-07-02 20:26
No 377362
      azeotrope  Bookmark   

The azeotrope of toluene and water boils @ 84.1C
(Hive Bee)
11-08-02 14:13
No 377647
      My bad, the azeotrop boils below H2O.  Bookmark   

My bad, the azeotrop boils below H2O.  I havn't found mention of any similar action with benz, but even if present it would not seem likely to lower its ~180 deg boiling point to below that of water.

Leaving asside the mechanism of oxidation which I casually inserted, what about the aspect of seperation of converted benz from tol.  There seem to be reason to believe that the widely seperated boiling points of tol/h20 and benz which lie on opposing sides of H2O, ie steam. 

So whatever method were used to achieve the partial oxidation, if the mixture were condensed and steam distilled as a part of a continuous cycle then the benz should be reliably seperated.  The ease of a continuous cycle further aids in the selectivity of the reaction due to the reduced per pass conversion required to make the process practical.

I am cautiously optimistic that one of the many known low yield-per-pass method, could be coupled to a continious distillation seperation strategy.

Or maybe I'm just high...

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
(Hive Bee)
11-08-02 16:27
No 377667
      Benzene-water azeotrope  Bookmark   

The azeotrope of water and benzene boils at 69.40C. The link on Rhodium archive is dead but  this is where is should lead to: .
(Chief Bee)
11-08-02 17:41
No 377681
      Link corrected.  Bookmark   

Link corrected.
(Hive Bee)
11-09-02 06:28
No 377900
      I appologize again, since we had been discussing ...  Bookmark   

I appologize again, since we had been discussing toluene oxidation to benzaldehyde, I got lazy and confused the issue further...

I was referring to the difference in boiling points of toluene/h20 and benzaldehyde/h20.  I know that tol/h20 form a aze... lowering the boiling point to below that of water, which is good for what I had proposed.

I have no real info on benzaldehyde/h20, but am hoping that the ~170(from memory sorry) boiling point will stay at least in the ~140+ range.  Given that tole dropped about 20deg, 140+ would seam a reasonable hope.

If so, does the seperation scheme have any obvious holes in the boat?  I have read of this kind of seperation being used from cloro-acetone, and though maybe it could be adapted.


And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
(Hive Bee)
11-09-02 20:33
No 378124
      Extraction + distillation  Bookmark   

Benzaldehyde steam distills with water (as does toluene), so you can't separate a mixture of toluene, water and benzaldehyde by simple distillation. What you should do is to draw the water from your organic phase in a sep funnel, save the organic phase and extract the water phase 2-3 times with about 1/10 of its volume of toluene. Then the toluene phases are pooled and dried over anhydrous magnesium or sodium sulfate. Then the distillation is performed, toluene boils as stated before at 110.6 C, benzaldehyde at 178.1 C. So a simple fractional distillation will work, but for sake of efficiency and purity of the end-product I recommend the use of a short Vigreux column (20 cm will be sufficient).
Remember: Benzaldehyde is soluble in water, at 20 C about 0.3g benzaldehyde will dissolve in 100g of water. But benzaldehyde is much more soluble in toluene...wink

Quidquid agis, prudenter agas et respice finem!
(Hive Bee)
11-09-02 22:43
No 378168
      Ok, bummer. I knew that method of extraction, but ...  Bookmark   

Ok, bummer.  I knew that method of extraction, but it would not be easy to make continuous.  And since the selectivity of the different reaction is almost always coupled inversely with conversion... I thought a continuous cycle targeting low conversion but easy continuus seperation would be a good option.

Well back to the drawing board...

And on the eight day, God created Meth...
... and hasn't done much of anything usefull since!
(Hive Bee)
08-20-03 07:24
No 454633
      oxidation of toluene->benzaldehyde in zeolite  Bookmark   

While on the subject of toluene->benzaldehyde routes, here's an interesting one I didn't find with TFSE using O2 and toluene on zeolite, the molecular structure of which is cage-like,

 allowing small molecules to become trapped  meaning a "high steady-state concentration of collisional pairs can be achieved".
Toluene to benzaldehyde
"..When we loaded a dehydrated BaY matrix with toluene (5 Torr) and O2 (1 atm) from the gas phase and exposed it to visible light at room temperature, we found that benzaldehyde is produced without side reaction "

e( i*pi)+1=0
(Hive Bee)
09-07-03 03:35
No 457536
      Zeolites  Bookmark   

An addendum to Praes' post:

Has these references:

 1. Photooxidation of Hydrocarbons in Cation-Exchanged Zeolites, Vicki H. Grassian and Sarah C. Larsen, invited review article in Handbook of Photochemistry and Photobiology, in press.

2. A Kinetic Study of the Thermal and Photochemical Partial Oxidation of Cyclohexanewith Molecular Oxygen in Zeolite Y, R.G. Larsen, A. C. Saladino, T. A. Hunt, J. E. Mann, M. Xu, V.H. Grassian, and S.C. Larsen, Journal of Catalysis, 204, 440-449 (2001).

3. Photooxidation of Toluene and Para-Xylene in Cation-Exchanged Zeolites X, Y, ZSM-5 and Beta: The Role of Zeolite Physicochemical Properties in Product Yield and Selectivity, A. G. Panov, R. G. Larsen, N. I. Totah, S. C. Larsen and V. H. Grassian, Journal of Physical Chemistry B, 104, 5706-5714, (2000).

4. Photooxidation of Toluene in Cation-Exchanged Zeolites, Y. Xiang, V. H. Grassian, S. C. Larsen, invited chapter in Green Chemical Syntheses and Processes, ACS Symposium Series767 (ed. P. T. Anastas, L. G. Heine, and T. C. Williamson), 2000, pp. 206-216, American Chemical Society.

5. CO Adsorption as a Probe of Acid Sites and the Electric Field in Alkaline Earth-Exchanged Zeolite Beta Using FTIR and ab initio Quantum Calculations, Ping Li, Yan Xiang, Vicki H. Grassian, Sarah C. Larsen, Journal of Physical Chemistry B, 103, 5058-5062, (1999).

I'd never heard of the shit before I independently came across the same site Praesedonym posted, usedTFSE and low and behold - this thread... Nifty stuff