Manganous-Ammonium alum and derivatives for use of toluene oxidation to benzaldehyde

Inspired by Cycloknight's posts in the Toluene--->Benzaldehyde thread, I decided to have a go at making the manganous-ammonium alum descibed in US patent 808095. Basically the patent gives details on preparing manganese-ammonium sulfate from ammonium sulfate, manganese sulfate, and 60% sulfuric acid. To oxidize the compound to the desired manganous ammonium alum (MAA), the mixture then has current passed through it in an undivided cell, using lead electrodes. I believe, after looking at the numbers in the patent that the amount of current necessary to complete the reaction is ~0.12 amp hours per gram of oxidant.

Using scaled down ratios from the patent, I started with the following: (Note that the amounts listed are not 100% correct, going off of the patent. So anyone who has more patience than me can probably be much more precise in the measurements)

448g MnSO4 (2.97 mol)

204g (NH4)SO4 (1.79 mol) (The actual ratio in the patent is 2:1, but I am using about a .30 molar excess per CycloKnight)

690g H2O

1096g H2SO4 (~600ml 93% Rooto brand)

With stirring, I added the acid to about half the water, then dissolved all 204 grams of the ammonium sulfate in the water/acid mix. Then the MnSO4 was added, followed by the rest of the water. This mixture was stirred for a 24 full hours before all the MnSO4 dissolved. The yellowish precipitate did appear. However, the overall color of the mixture was a very pale pink color instead of the orangy-yellow color I was expecting. Im guessing it was from the MnSO4, but the drain cleaner has a bit of a brown tint to it, and that may have effected the color somewhat as well, but I'm not for sure. The (NH4)SO4 was 99% pure and the MnSO4 was hydroponic grade, and seemed to be free from any major contaminates. It was finely powdered similar to talc, with a whitish-pink color.

After the mixture had been stirring for over 24 hours, and everything was about as dissolved as it was going to get, I put the lead electrodes into the jar and hooked up the power supply. I am using a computer PSU which can supply 3, 5, or 12 VDC at 30 amps. (Only 10 amps for the 12v output) I am using the 5v output, which is actually about 4.8v across the cell. I am not using a power resistor in the circuit, since I am only using 5 volts. I am using an old ammeter from an automobile to measure the current (all my fancy electronic measuring equipment is at work at the moment). It is obviously not the most precise instrument in the world, but it's close enough for what I need it for. It is currently reading about 3.5 amps, and has been holding steady there for the whole time so far. I will try to remember to bring my electrical meters home with me tomorrow, so I can get a more accurate current measurement.

As soon as I switched on the power to the cell, a dark red color started pouring off of the anode, and within 5 minutes the entire mixture had turned a light red color. Within 15 miutes, the mixture was a suprisingly dark red color, and after about an hour, the mixture was a deep purpleish color. (See the photos below) Using the calculations I mentioned earlier, I figure it should take about 22.5 hours to complete the reaction. (652g oxidizer x 0.12 amp hours per gram = 78.24 amp hours. 78.24ah / 3.5 amps = 22.35 hours) I'll take some more pictures after the 22 hours is up, so we can see the difference in color.

Here is what the mixture looked like between 5 - 15 minutes after I switched on the power:





This is how it looked after an hour:





My caveman electrical test equipment; 4.88 volts across the cell



About 3.5 amps.....I think.



And last but not least........My ghetto fabulous 12v PC fan-harddrive magnet-2x4 lumber magnetic stirrer!



I'll be adding more to this in the near future.

Edit by Chemoleo: Changed title and merged threads!

[Edited on 24-1-2007 by chemoleo]

There haven't been too many times when I've had to make my own ammeter, but the times that I did, I always had the appropriate sized resistor. Point being, I've never actually tried using a wire for a shunt, but I think I'll stick one in this circuit for curiosity's sake just to test the accuracy compared to a high end digital ammeter. I'm sure it's better than my old automobile ammeter anyway.

Also, I got to looking at the ratios in the patent again, and I think I need to add about another 110 grams H2SO4 to the mix to make it 60%. But seeing as how it's about 4:00am, my brain cannot be fully trusted. I think I'll do it anyway. I think too much acid is better than not enough in this case.

***Never mind. It's close enough to 60% already.

[Edited on 19-10-2006 by Hilski]

I almost forgot. Here are a couple of pictures of the cell after about running at 4 amps for 22+ hours. The mixture has settled some, making it appear as though there are 2 phases. It was VERY thick at that point, and the magnetic stirrer was having a very hard time. I need to get some smaller stir bars for this, but ultimately I will rig up an overhead stirrer with either glass or nickle rods. But, for now I will be stirring by hand for the actual oxidation reaction to make sure there is complete mixing of the oxidant with the toluene (or ethanol, methanol, glycerine, or whatever)

Just a few pictures

Here is how the mixture looks after the reaction is complete:




If you look closely at picture #2, you can see that there is a pretty nasty emulsion. I'm not sure what this is from, but I'm hoping I will be able to get rid of it by filtering the top layer.
Cycloknight wasn't kidding when he said the whole house smells like benzaldehyde, because it damn sure does.

***Addon: After adding about 150ml toluene to the mix and stirring a bit with a glass rod, the emulsion cleared up for the most part and I was able to extract the benzaldehyde without too much problem. I know there is at least a little bit of benzoic acid left, because after I removed the benzaldehyde, I could smell it in the reaction vessel. I'm guessing that its from leftover toluene from the last reaction/extraction. I doesn't appear to have caused any problems at all, so I'm not too worried about it. I use 4 -5 amps when regenerating the oxidant, and it still regenerates in about the same amount of time as it did originally.

Here is the really ghetto mechanical stirrer I used to stir the mixture. It worked very well, and I will continue to use it for this purpose.



-Hilski

[Edited on 6-11-2006 by Hilski]

Possibly another (easy) oxidizer for toluene to benzaldehyde?

Looks like another good method .

I would bet that this same manganic oxidation reagent
would also be an effective reduction reagent when it
is in the reduced "ous" manganous state .

For example it possibly would reduce a phenylnitropropylene
to a phenylisopropylamine ....if a reaction like that might possibly have similar usefulness

And it would possibly also reduce nitrobenzene to aniline ,
picric acid to picramic acid .....ect.

Of course the electrical regeneration to the reduced state
would require a porous cell around the anode and plain acid
anolyte .

Anyway , here is the patent you mention above attached

Attachment: US3985809 manganic sulfate oxidizer for production of aldehydes.pdf (341kB)
This file has been downloaded 2635 times

Thanks for that post, Roscoe.
I had been thinking about ways one could go about regenerating the oxidizer in a more expedient manner. KMNO4 had came to mind, but I have no idea how to go about calculating proper proportions. I also wondered how adding another element (K) would effect the behavior of the oxidizer both during the reaction with toluene, and during electrolytic regeneration.
Perhaps a small specific amount of the permanganate could be used in addition to the electrolytic process to say, cut regeneration times in half. I also wonder if something like ammonium or potassium persulfate could be used to achieve the same results?
I guess seeing as how I already have about 2 liters of the alum prepared and fully functional, that I should be the one answering these questions instead of asking them. But what fun is that?

I have wondered if even hydrogen peroxide , or
perhaps acetone peroxide , or MEKP could be used for regeneration of the manganous alum to the manganic alum . It sure would save hours of electrolysis to be able to stir in the stuff and boil off the inert byproduct .

Yeah I would think that the persulfates should also
work the same way with their respective potassium
or ammonium alums . You would have to keep an
inventory of your reaction mixture content with the
desired proportions of the respective ions , and
work out the amounts of what you add during regeneration , so that you keep the composition
of the reagent consistent with its proper stoichiometric proportions for the desired alum formation .

I haven't done the math , so I am not sure how the
numbers crunch on this idea ....it just looked like an
interesting possibility , particularly on the initial formulation of the potassium alum ....it looked like
that making the reagent in the manganic form ready
for use without electrolyzing for the first run , could
be done by forming some of the potassium sulfate and
manganic sulfate content from potassium permanganate
plus H2SO4 , eliminating or reducing the need for the
electrolysis . I think there is even some surplus oxidizing
capability there for oxidizing the bulk manganous sulfate
to the manganic state . So it appeared to be a way of shortcutting the workup for the initial alum ....if nothing else . What would be the economy of this as compared
with just using electrolysis alone on the manganous sulfate alum is another matter which could make it not worthwhile .

BTW I found an analogous process is possible for chromium also , as is used here for manganese compounds ....but of course the chromium reagent
would be a way more expensive method .

I am still inclined to believe that the ferrous salt and
its alums would also work for this process , and also
other polyvalent metal salts .....although my interest
would be focused on the cheap ones like manganese
and iron

I guess all in all, passing current through a non-divided cell for 24 hours isn't really all that bad. Unless one needs to regenerate the oxidizer like RIGHT NOW, then there just isn't a more economical way to do so. Here are a couple of pictures of the electrolytic cell regenerating the MAA recently. 4 amps have been passing through the cell for about 10-12 hours in the photos. I think it was still needing about 10-12 more to be fully regenerated. You can see the large quantity of yellow precipitate (MAS) still sitting at the bottom of the jar. This is because I have crammed so much oxidizer into this jar with not enough acid that the mag stirrer has a hard time keeping it all in suspension. A little poking around with a glass rod gets everything mixed up again though, so it really isn't a problem. If you look at the second picture, you can see a brown substance floating on top, in the center of the jar. This is mostly benzoic acid floating on top of the saturated acid solution. It is due to left over toluene and/or benzaldehyde from a previous reaction. It's hard to get every last little bit of organic material out of the mix, but it really doesn't affect anything. It just smells REALLY strong once too much builds up in the cell.

@Organikum

As I think I understand this process so far .....

That patent which I posted above , US837777 , is directly related .....but superior to
the " neograviton method " which you posted early on the Benzaldehyde from Toluene thread .

The earlier patent US780404 , by the same inventor Max Bazlen , is a patent which you listed among others in the other thread . The yield of benzaldehyde from toluene by oxidation with manganese (IV) sulfate , manganese persulfate , is reported as nearly quantitative , which generally means >95% , with no byproduct benzoic acid
from any overoxidation .

The subsequent patent US837777 simply advances the
same process using Potassium Permanganate for generating the dark brown colored
Manganese ( IV ) "per"sulfate , Mg(SO4)2 .

The (IV) valency variant is a yet still more active oxidizer than the also useful *green* colored Manganese ( III ) analogue , or Mangan " ic " Sulfate , Mg2(SO4)3 .

Reduction of the (IV) and/or the (III) compound during oxidation of toluene to benzaldehyde produces
the fully reduced Manganese ( II ) Mangan " ous " Sulfate , MgSO4 as the spent reagent , which is regenerated ,
by electrolytic oxidation , stepped back up to its (III) and
further to its original (IV) oxidation state for reuse .

CRC gives a range of colorations from pink through red for the ( II ) manganous sulfates depending upon the level of hydration , including the alum with ammonium sulfate , which BTW is a hexahydrate .

Oxidation to the ( III ) state is described as producing a
green color for the pure manganese(III) or mangan" ic "
sulfate .

I am thinking that the mixing of the green in with the incompletely regenerated red is what gives the darkening towards brown .....it could even pass through a tar black color first and then lighten slightly to more distinct brown for the final transition to the brown coloration of the manganese ( IV ) sulfate , manganese persulfate . IIRC the persulfate is only quasi-stable and only in a range of fairly concentrated H2SO4 .

Anyway I suppose the advantage realized for any
"hyper-regeneration" being applied chemically using permanganate , or perhaps peroxide if possible , or by electrolysis of the manganic sulfate to the even higher (IV) persulfate is that an additional amount of toluene may be converted to benzaldehyde by the same quantity of Manganese ion present , if its oxidation state is at maximum , which is the persulfate .

I haven't gone back and checked the details on the
regenerations by electrolysis which have been pictured
and described , to see if anyone allowed the regeneration
to keep running longer than required to produce the pink
or red material , even where the alum double salt is being
used ......to see if it will continue to oxidize further to the
solid brown color as would indicate the persulfate .

Edit: I just went back and reviewed this thread , and it looks like the ammonium alum manganese sulfate follows the US808095 patent description nicely , with regards to color
changes , and other details . Whether or not the yield or
the volume efficiency for this method could be improved by running the regeneration electrolysis longer , might be a worthwhile experiment . It might be necessary to have some
additional amount of manganese sulfate present which is
beyond that amount which will form the alum in combination with the ammonium sulfate present . The alum itself may be limiting with respect to formation of the persulfate .....and
of course the acid concentration would have to be within the allowable range also in order to permit its formation from
any added time of electrolysis . Color change and gas evolution from the anode would tell the tale on whether
this effort is worthwhile , along with of course comparison of the yield and how much toluene may be reacted with a given quantity of the regenerated oxidation reagent .

But the typical yield for the alum Mn(III) process is 80% , compared with >95% reported for the non-alum Mn(IV)
process , which should also have a better volume yield ,
although it would depend on the volume of acid ( I haven't checked this to be sure ) . So it would seem that using the
Bazlen patent method based on the Mn (IV) sulfate would be superior .

Quantitative yield is as good as it gets

[Edited on 26-1-2007 by Rosco Bodine]

Some experiments

As I mentioned in another thread, I would like to set up a functional electrolytic cell that would produce Manganese(IV) sulfate aka (MnSO4)2 from MnSO4 in 55% H2SO4. I loosely followed the guidelines from This Patent to know what reagents/ratios etc to use. Also, one of my goals was to find out whether Tyvek (a commonly available material manufactured by Dupont) would make a sufficient membrane for a divided electrolytic cell. The following are some details and a few pictures of what I've come up with so far.

Chemicals and materials:

Anolyte:

MnSO4 - 50 grams disolved in 504 grams H2SO4 (55%)


Catholyte:

55% H2SO4

Cell construction:

Cathode compartment: A small HDPE container with holes drilled in the sides. Inside the HDPE container is placed a Tyvek bag which acts as a microporous membrane to allow for ion echange. The cathode is 0.5 inches wide X 6 inches long and is made of lead sheet. The compartment is filled with 55% H2SO4 and placed inside the glass beaker which will serve as the anode compartment.

Anode compartment: A 600ml Kimax beaker was used as the anode compartment. A lead anode, 1 inch wide X 6 inches long was placed in the compartment along with a solution of 50 grams MnSO4 dissolved in 504 grams 55%H2SO4. This compartment is where (hopefully) a solution of Manganese(IV) sulfate will be produced electrolytically.

The empty cell:



The cell after the pink MnSO4/H2SO4 solution has been added:



I hooked up the computer power supply I used for this project, and set the voltage to 5 volts. I chose this voltage because it's what I had used in the past to regenerate the manganous ammonium alum, and it has worked well. I switched on the power, and a dark red color, similar to that of the aforementioned alum, poured off of the anode.





I didn't use any kind of magnetic or mechanical stirring for this project, but if I decide to scale it up, I will definately add that to make the process a lot faster and more efficient. For this small cell I just used a glass rod to stir things up occasionally.

Here is the cell after about 10 minutes:



And again at about 1 hour:



After about an hour and a half, the solution in the cell had turned a very dark, opaque burgundy color and didn't appear to be making any further progress. I checked the current and saw that it was only pulling about 1.5 amps, and was generating almost no heat at all. So at that point I decided to switch from 5 volts to 12 to see if that made a difference. Immediately upon switching on the 12 volt power, a brown color was generated at the anode, along with more vigorous oxygen production. The hydrogen evolution at the cathode was enough that it started splashing the catholyte out of the compartment. I also noticed the the cell started to heat up a good bit (as expected) and the current draw shot up to over 6 amps.

Note the brown color starting to form around the anode



At that point, I decided to place a 50 watt DC lightbulb in series with the cell to help control the current. As of now, the cell is pulling about 3 amps, and gas evolution is not nearly as bad as it was before. There doesn't seem to be nearly as much heat produced as before either.



The cell has been running for a couple of hours now, and as soon as there has been significant change (or lack thereof) I will update the post with further results. At this point, I am optimistic that Tyvek does indeed make for a suitable membrane for divided electrolytic cells.

UPDATE:

At about the 3 hour mark I went to check on the cell and found what appears to be a successful experiment. Even with no stirring, the contents of the anode compartment were a deep brown, almost black color. The heat in the cell was a lot lower than I expected, less than 40C for sure. Now I just need to figure out exactly how long to this thing go to get 100% conversion to the persulfate.







Here are some links to high res copies of the last 3 images. The small ones are a little hard to see.

http://www.sciencemadness.org/scipics//Hilski/persulfate_cel...
http://www.sciencemadness.org/scipics//Hilski/persulfate_cel...
http://www.sciencemadness.org/scipics//Hilski/persulfate_cel...

Questions, comments or suggestions about any of this are welcome. Ideas for scaling up would be great as well.

-Hilski









[Edited on 1-2-2007 by Hilski]

It would probably be better to put the tyvek around the *outside* of the perforated plastic form , as opposed to
having it inside like a liner bag . I just think that using
the rigid compartment as an inner form around which the
tyvek is stretched .....would simplify things greatly all around .....instead of " all inside "

This would definitely be a better arrangement with the smaller diameter cathode compartments .

Since this is the cathode also , a carbon rod or a piece of
copper or stainless rod or pipe might work fine , as no worries about oxidation and the hydrogen blanket on the surface should provide a lot of " anti-erosion " by " cathodic protection " .

[Edited on 1-2-2007 by Rosco Bodine]

Maybe one of these would work:



http://www.maycocolors.com/shapes/shapeDetails.cfm?shape=101...

Low fired porous ceramic bisque.

yeah I know but Im in another country and customs dont like chems. And although it was interesting to do,if I was to need it again I'll drive the 3hrs one way and buy it.The trouble is the beautiful women there........can't leave till I get one

Nice work Hilski, lots of potential with this manganous-alum route. Great pics BTW !
This thread sure brings back memories


[Edited on 13-2-2007 by CycloKnight]

Ok, I got a case of these, and they seem to be perfect for electrochemistry experiments. When filled with water, the outside gets wet and "sweats" on the lower half after about 5 minutes. The clay is an off white low iron type.




http://www.maycocolors.com/shapes/shapeDetails.cfm?shape=101...

Low fired porous ceramic bisque.

[Edited on 14-2-2007 by Eclectic]

Hehehe ....looks like the mother of all porous cups

It should work very well too , *if* it holds up okay in the
pretty strong H2SO4 which is used for the electrolyte in this process .

Buying a case of them , hmmmm ...you must be confident .

Let's just hope it isn't a "case" of only .......
"hope springs eternal" and/or
advance christmas shopping for that perfect gift
for all your wino friends

I just had an idea that maybe a 100 ml mixing cylinder is placed inside , it would make a perfect water cooled cathode form for wrapping sheet lead around .....fitted with a two whole stopper with one long tube nearly to the bottom , and one short tube .....circulate cooling water through the cylinder , and you could really put some Amps through the thing . It would keep the electrode nicely centered too .

[Edited on 14-2-2007 by Rosco Bodine]

Outstanding . You could build a serious electrolytic cell
of coaxial electrode arrangement , having that component as the porous cup . This is great , it looks like the tyvek works for a divided cell , and this will probably work fine too

Hmmm. I'm thinking maybe as this progresses we should have a new specific topic category for Electrochemistry , for all related reactions and equipment , literature , ect.
I know it is included as a part of " Technochemistry " now
but that is sort of an ambiguous name ....
since *all* chemistry is actually pretty " technical "

What do you fellows think about this ?

[Edited on 14-2-2007 by Rosco Bodine]

There is a smaller part that may work also
with a smaller scale cell .

This is 3.25"D X 4"H

http://www.maycocolors.com/shapes/shapeDetails.cfm?shape=203...

Also see this page for all the Mayco bisque .

http://www.ceramicssf.com/maycobisqueware.htm

About halfway down the page on the right is a " message bottle " and it looks like it might make a better substrate
for PbO2 and using an electrolyte inside for the connection .
I am not quite sure if in the case for this being used as the anode , that there may not be some gassing on the surface of the electrode in the interior electrolyte due to the slight
voltage drop ....or what electrolyte would be useful . It seems possible that some series voltage differences might
be problematic for making the connection internally via an
electrolyte . That whole idea is very interesting , but not guaranteed to work because of the unknowns ...I think

[Edited on 23-2-2007 by Rosco Bodine]

Since the site got hacked, and was going to be down for a few days, I figured I should try something constructive in the meantime. So I decided to make some more Mn(SO4)2 aka. Manganese persulfate, or Mn(IV), and oxidize something with it. So I preceded to use a terracotta cylinder I picked up at a local craft type store and make a divided cell.
I dissolved 450 grams MnSO4 in about 2.5 liters of 55% H2SO4, and placed it in the anode compartment of the cell. I decided to use the inside of the terracotta vessel as the anode compartment, because it was just more convenient. I electrolyzed the mixture at 12 volts, 3 amps for about 24 hours, with current control being provided by a 50 watt DC light bulb in series with the cell. There was no heat created at all, so next time I will add another 50 watt light bulb in parallel with the other one to up the current to around 6 amps. I stirred the mixture vigorously 4 or 5 times during the 24 hours, and that seemed to be enough.
After the electrolysis was complete the mixture was kind if thick, and a very deep brown color. Most of the Mn(IV) was dissolved in the acid, but there was some black sludge at the bottom of the cell that needed to be stirred around in the acid so it could be poured out into the reaction vessel.
I used a 1 gallon glass jar for the reactor, which worked pretty well. To the reactor I added the 450 grams Mn(IV) in about 2.5 liters 55% H2SO4, along with about 210 ml toluene. I decided to try the reaction at room temperature, so a homemade overhead stirrer was set up and the mixture was stirred vigorously overnight (probably about 12 hours).
When I went back to check on things, I was somewhat surprised to see the the reaction had proceeded nicely and was totally complete. The deep brown solution had turned to a light brown sand color, and the the smell of benzaldehyde inside the vessel was almost overwhelming . The scent of toluene was not detectable at all, so I am guessing that nearly 100% conversion was achieved. This is not a good thing though, since some benzoic acid was produced, and was floating in a layer between the acid and the benzaldehyde as can be seen in the picture. This problem can be remedied by simply using a larger volume of toluene, so that there is an excess compared to the oxidizer.
Extraction was a little bit tedious because of the benzoic acid, but not too bad. I added another 100ml of toluene to mixture and decanted most of the product, and used a syringe to remove the remainder that I couldn't pour off. I haven't distilled anything yet, so I can't give any info on yield. But I am guessing that it will be pretty good, probably between 150 and 250 ml. I will update this post once I do have the final results.

I forgot to take a picture of the Mn(IV) before I started the reaction, but here it is after it has been reacting for a few hours. You can see some of the lighter colored brown oxidizer at the bottom that has already been reduced by the toluene. Remember that the mixture was totally black before I started.




Here is the reactor after the oxidation is complete. You can see the organic layer, which was a bright yellow color after it was extracted.



So far I am pleased with the results of this experiment, and if yields turn out to be pretty good, I would definitely consider this a good, relatively simple method for producing aldehydes.





[Edited on 8-3-2007 by Hilski]

AEM’s in general

What are the short comings of the tyvex membranes? I rather liked the concept…
Thinking about using Teflon tape PTFE maybye too.

Reading about the preparation of these membranes, it seems that net positive charges are impregnated in the polymer matrix as they make it….

Is the SiO2 or some component of the terra cotta pots giving it a net positive charge to repel cations?

Also what is the cathode reaction?

From: http://ocw.mit.edu/NR/rdonlyres/Materials-Science-and-Engine...

PbO2 + 4 H+ +2e- + SO42- ---> PbSO4 + H2O


Alittle benzoic acid doesn’t seem to cancel the show good stuff....

so you placed a terra cotta container inside another larger one - and used the ceramic as the membrane (generating the alum inside the pot instead of outside) - the larger container catching most of the bubbling? this worked very well from what it looks like..

Correct. I used a big glass jar for the outer container, and set the clay vessel inside of it in a coaxial type arrangement. The glass jar could just have well have been a plastic bucket, or anything else that is acid resistant. Pretty much all the foaming took place in the outer container like you said, and presented no problem at all. I'll post a picture of the contraption as soon as I get a chance. I still need to get off my arse and distill the stuff so I can see what the actual yield was. But I'm crossing my fingers that it will be 70% to 80% or better.


*Edit* I just noticed that you were referring to this oxidizer as 'alum'. This stuff is just MnSO4 oxidized to Mn(SO4)2. No alum this time.

[Edited on 11-3-2007 by Hilski]

Impurities in Pottery-Grade MnO2

My first go

Ok so I've finally gotten around to making my first cell. I decided to just make a cell the same size as Cycloknight's in order to get a feel for the reaction conditions, and then do a bucket-size scale up once I am confident. The cell runs at around 3.5A as measured by my digital multimeter. Naturally I won't be conducting any oxidations in the plastic container. The contents of the cell will be transferred into a glass jar which will allow it to be heated with toluene. Here are some pictures:

The computer power supply I am using. Capable of 40A at 5V:

The overall setup

The purple colour from the anode

The MMO electrodes from a pool chlorinator. They are rated at 25A over 25 years at an extremely low chloride concentration, would be very exciting to try out a chlorate cell with them! I do not know their composition, but the grey one is 1m long and flexible and the black one is 50cm long and rigid. In the cell the black electrode is the anode and the grey one is the cathode.

The lid of the container consists of a rigid outer section and a removable centre.



I turned off the electrolysis as I noticed that after a couple of hours no more purple was being produced. It was also noted that the colour of the liquid had not shifted to the expected dark purple after a period of time. I put this down to not allowing the MnSO4 time to dissolve, so the cell will be stirred overnight.

What follows is the overhead stirrer I made from a beater I obtained at a charity shop which sells second hand goods (called Lifeline in Australia), a pen and a coke bottle. I used a hacksaw to liberate the metal part of the part of the beater that "beats" and used hot glue to attach this to the casing of a cheap pen which was almost a perfect fit. A coke bottle was then cut up with a Stanley knife and a section of plastic hot glued to the pen lid to serve as an agitator. I originally planned to use the part of the pen which allows it to be hung from a pocket for this purpose but it was too streamlined. The only downside to this stirrer is that it obviously cannot be used in the more plastic-unfriendly solvents, so it will not be able to stir the mixture during the actual oxidation. But manual stirring should be sufficient for this.

The beater itself has three different speeds, but the slowest is usually more than enough. The stand is also very handy as it provides a solid base and eliminates shaking. I cut a hole in the lid which allows the shaft to pass through but stops any stray acid coming out. Overall pretty successful for $15.00!

The part that does all the work, quite sophisticated!



It can be seen that the stirrer achieves adequate agitation. All of the off-white precipitate is in suspension when it is running. Unlike magnetic stirring:

Stirrer

Magnetic




One odd thing I did notice was that upon addition of a couple of drops of 6% hydrogen peroxide solution, the electrolyte turns an odd yellow colour, which is replaced by the normal "strawberry milkshake" colour after several minutes of electrolysis. I found this by seeing if any purple alum would be made upon addition of oxidiser, as has been previously posted.



Would someone like to throw a guess at what this material is? I've tried mixing the peroxide with both acidified ammonium and manganese sulfate solutions by themselves and have not been able to replicate the precipitate. Obviously this leaves the conclusion that it is an oxidation product of the manganese ammonium sulfate, but wouldn't the oxidation product be the purple compound we are seeking?

Another thing I noticed was that when the 1m long electrode was used as the anode, the reaction would not proceed at all and only 0.04A would be recorded on the multimeter. I thought this was strange as that electrode would presumably be used as the anode in the chlorinator cell it was designed for as it is the longest electrode and therefore has more surface area. It doesn't affect the experiment, though as the electrodes have shown no wear in the past when they were used in similar electrolytes.

If anybody wants some more specific pictures, don't hesitate to ask!

Formula409

Quote: Originally posted by DyD

I'm planning to attempt to construct an MAA electrochemical oxidation cell to oxidize toluene and methanol. In my attempts at sourcing manganese compounds, I've constructed the following chart: -------------------- Source Material PricePerPound Shipping Purity PercentMetal CC MnCO3 5.80 15usd/15lb 100% 45-47% CC MnO2 1.50-.8 15usd/15lb 96.8-81% 51-55% 1-5% Fe2O3 1-5% SiO2 1-7% Al2O3 0.2-2% BaO EBay MnO2 3.99 5.99usd/1lb 99% 63% -------------------- My question is this: As one can see, the cheapest source of manganese per mol is the manganese dioxide from "Columbus Clay" at 1.50usd for one pound, and eight dollars for ten pounds. However, the manganese dioxide is, at worst, 81% pure, with Fe2O3 and Al2O3 making up the most relevant impurities. Would either of these compounds or their respective sulfates negatively impact the performance of a MAA cell? Thanks!

Quote: Originally posted by sabbath06

Yeah, by heating it more I got all of the purple oxidizer to turn back to it's original color, toluene layer was tinted yellow but does not smell like benzaldehyde at all. This run was in a 400ml beaker. Will try scaling up to about 1 L and watch the temps more closely

Quote: Originally posted by sabbath06

Yeah, by heating it more I got all of the purple oxidizer to turn back to it's original color, toluene layer was tinted yellow but does not smell like benzaldehyde at all. This run was in a 400ml beaker. Will try scaling up to about 1 L and watch the temps more closely

A little enlightenment.

Hello,

I constructed and ran such a cell some years ago (about 6 liters total volume of all reagents) and after much the same results as I read now here regarding low yields, it finally occurred to me that what was occurring was that the toluene was simply evaporating out of the top of the open cell before it was able to be reacted.

Upon sealing the cell and using a conventional condenser to manage pressure build up I was able to achieve the claimed yields.

If you look at the illustration in the old patent where they used several hundred KG of reagents, you can see that the 'tardis' or I guess even phallic shaped steel (I assume) reactor they used was a closed unit with a condensing pipe running from the top back down into the main body of the reactor.

Hope this helps everyone with their frustrations

P.S. Computer power supplies connected in parallel are a cheap source of lots of amps if you can scrounge old discarded PC's which is very easily done as you may be aware.

I had about 10 or so CPU power supplies (about 3 plugged into each household circuit) in parallel at up to 35 amps a piece... I did not need any heating in the cell I did need thick, thick copper braid !

This regenerates fast.

Lead is easily obtained on the cheap from your metal recyclers, melted by a propane flame and poured onto ceramic tiles to create beautiful sheets of almost pure lead that you can cut up with tin snips or whatever for your anode etc.

Overhead stirring using a medium speed/high torque motor is a must and a bitch to seal. Failing going pro and purchasing a proper lab quality nipple setup, you can use the brass/s steel combo bearing out of the bottom of a food blender or similar appliance and use silicone or epoxy to jig it up.

Such a setup requires constant replacement of silicone or ptfe based lubricant or the sulfuric will eat the SS. You couple/join the SS center originally from the blender to a glass stirring shaft and paddle with a plastic "shaft coupler" from a hobby/model shop (looks like a hollow cylinder standing on its short end with two horizontal plastic hex head screws on the side that grasp the two vertical shafts) as anything else will work loose in my experience.

I am sure others will think of better ways, this was just what occurred to and worked for me.