Sciencemadness Discussion Board - Phosphorus via reduction of phosphoric acid with carbon in a microwave

Phosphorus via reduction of phosphoric acid with carbon in a microwave

Z8320 - 3-6-2010 at 17:58

The patent attached describes a process for reducing phosphoric acid with carbon to white phosphorus. The patent gives a laboratory scale example in which a quartz test tube is charged with carbon and phosphoric acid and irradiated under conditions fairly similar to those in a conventional microwave oven. An inert or reducing gas flow is required, but the temperature reached by the reaction mixture is only 540 °C.

It seems simpler and safer than some of the other methods I've heard such as the decomposition of phosphine into its elements at 375 degrees celsius which has a significant explosion risk if your setup is shoddy or you haven't thought it through. I'll probably try this once I get around to getting myself a tank of inert gas. The reaction possibly produces enough carbon monoxide and hydrogen that I don't need to worry about an external gas supply but can instead rely on the evolution of these gases to protect the phosphorus from air.

Has anyone made any attempts like this?

Attachment: Phosphorus-Microwave.pdf (67kB)
This file has been downloaded 1658 times

neptunium - 9-3-2013 at 11:16

have you tried it? i would need a quartz reactor and som nitrogen but i REALLY want to try this!

zed - 9-3-2013 at 16:05

According to reports, conventional microwave ovens can often be used for such reactions.

elementcollector1 - 9-3-2013 at 17:47

Of course, finding a quartz test tube is another matter. Could potentially use borosilicate, but that would be pushing it (temp. resistance up to something like 600 C)...

Lambda-Eyde - 9-3-2013 at 18:06

Quote: Originally posted by elementcollector1

Of course, finding a quartz test tube is another matter. Could potentially use borosilicate, but that would be pushing it (temp. resistance up to something like 600 C)...

Finding a quartz tube isn't a problem. The price isn't either. This site sells them for 30$ or so, which isn't too bad. I wouldn't try borosilicate, 540 is around the annealing point, and when you consider what you're doing - producing deadly white phosphorus and carbon monoxide at >500 degrees in a microwave - you really don't want to take any shortcuts.

I have a quartz test tube, but not a suitable microwave...

Anyways, I have a buttload of WP as well - so it's not very interesting to me.

neptunium - 9-3-2013 at 21:10

although the challenge of getting it is more rewarding....are you selling any WP?

Endimion17 - 10-3-2013 at 06:15

Quote: Originally posted by elementcollector1

Of course, finding a quartz test tube is another matter. Could potentially use borosilicate, but that would be pushing it (temp. resistance up to something like 600 C)...

Electric heaters such as this one contain quartz tubes which host resistive heating wire.
Find a defunct heater and take it apart. Collect the tubes and the wires. Profit.

quartz tube

cal - 11-3-2013 at 05:02

I have quartz tube pieces from 12 inches up to 36 inches.

elementcollector1 - 11-3-2013 at 07:22

Quote: Originally posted by cal

I have quartz tube pieces from 12 inches up to 36 inches.

How does one close them at one end? I don't think my blowtorch can do quartz...

neptunium - 12-3-2013 at 06:24

i think an inert gas is required for this reaction (non oxydasing environment ) and it would be convienient to carry the Phosphorus along to a cold trap . so both end dont need to be sealed,

AndersHoveland - 12-3-2013 at 13:59

Quote: Originally posted by Z8320

the temperature reached by the reaction mixture is only 540 °C.

500 °C is just slightly beyond the temperature an ordinary stove top can achieve.

One factor that should not be neglected is that sodium salts have a way of fusing with glass (and likely fused quartz also) at higher temperatures. One should never heat dry sodium phosphate in a glass flask over a flame, because salt will just fuse with the glass, forming a glassy fusion that melts at a lower temperature, and this can cause a hole to melt in the bottom of the flask.

bahamuth - 12-3-2013 at 14:23

Well I can tell you quartz won't hold up to phosphoric acid at 540 degrees C.

http://www.advaluetech.com/clear_fused_quartz_technical_info...

Phosphoric acid is actually used to dissolve quartz for trace element analysis.

zed - 12-3-2013 at 18:31

Be that as it may. There is a good chance a conventional microwave will do the trick.

At least, I have that impression. I might have gotten that impression via the Science Madness Archives.

At any rate, such microwave ovens can be obtained "used" in the U.S., at a Goodwill Store, generally in the $10 to $20 dollar range.

I realize some folks are located in other parts of the world, and local availability may vary.

AndersHoveland - 12-3-2013 at 22:04

Quote: Originally posted by bahamuth

http://www.advaluetech.com/clear_fused_quartz_technical_info...

"phosphoric acid which attacks quartz at temperature above 150°C "

I wonder how the phosphoric acid is able to attack the quartz?
Possibly form some sort of pyrolic acid with the silica?
something like: (HO)₂Si(OPO₃H₂)

Can phosphoric acid attack regular glass also at elevated temperatures?

bahamuth - 12-3-2013 at 23:21

Quote: Originally posted by AndersHoveland

Quote: Originally posted by bahamuth

http://www.advaluetech.com/clear_fused_quartz_technical_info...

"phosphoric acid which attacks quartz at temperature above 150°C "

I had hot phosphoric acid etch my ceramic tabletop stove, with the stove set to max (so around 250-350 °C).

It's a 1st generation ceramic tabletop stove so there are no markings but looks very much like the Schott Ceran brand glass, composition unknown but I guess it's not far from borosilicate.

But I have been using Schott Boro 3.3 glassware to boil phosphoric acid in, but have yet to see the same beaker used repeatedly suffer any etch marks.

AndersHoveland - 13-3-2013 at 02:11

Found this warning for fused quartz:

Quote:

Do not use hydrofluoric acid (or hot phosphoric acid).
Alkaline solutions attack slowly at room temperature , but much faster at elevated temperatures.

neptunium - 13-3-2013 at 06:09

damn! what else is microwave transparent and hot acid resistant? its going to be much harder than espected...

but thats what makes it so interesting and rewarding!

[Edited on 13-3-2013 by neptunium]

testimento - 5-2-2014 at 15:22

This is most interesting. I was thinking of making magnesium silicate retort (MgOH + SiO2 = MgSiO2 etc.), which is supposed to be transparent on the microwaves and has a melting point of 1900C and is regarded as having high resistance towards chemicals in high temps. Options are to use direct heating with coke up to 1600C, or then applying the microwave.

The problem with the microwave seems to be the reaction energy. The patent cites that they were able to produce about 2 grams in 2 hours using 1kW of microwave power. This is far off scale of what would be feasible even for amateur.

Essentially my concept is of magnesium silicate "bottle", which would have, probably solid fitted steel tubing retort which would be impregnated underwater. This pot would be placed within microwave, or then into coke bed and fired up. The gases would be led into the water tank aside the hopefully forming phosphorus, and the waste gases would be safely exhausted via meters long chimney up to the skies for the birds' and green partys' trouble.

Though phosphine is denser than air, it should be destroyed in situ. This provocates the need to lead the exhaust gases via tubing and bubble them through something. What will react with PH3? NaOH? Hypochlorites? Acids? Something that won't interfere with carbon monoxide, of course.

[Edited on 6-2-2014 by testimento]

Fantasma4500 - 8-2-2014 at 04:07

i suppose you could fill the entire microwave with butane, it requires a whole lot of oxygen to burn just decently, and if it has just enough oxygen it wont probably be able to knock the microwave door open
you can probably connect a hose to the inside of the microwave, then connect hose to butane lighter refiller and take a metal plate with a hole in and press against the valve, in my country we have coins with perfect holes for this..
otherwise 'dolomite' with sulfuric acid should give a good amount of CO2, bfesser got 25kg dolomite approx to give 11kg CO2

Metacelsus - 8-2-2014 at 06:44

Quote: Originally posted by Antiswat

i suppose you could fill the entire microwave with butane

No, really, you shouldn't, at least if you like your house/life.

testimento - 8-2-2014 at 06:57

Why in devil should the mic be filled with butane? You can generate CO2 very easily, if you really need to fill it with anything.

I was thinking of something like this:

Just essentially a refractory ceramic (MgSiO is best afaik, ceramics are higly transparent to microwaves) bottle, most likely DIY, with steel tube attached to the mouth and aligned down to water trap. The williepete will melt at 44C and evaporate at 280C and the reaction heat should be sufficient to allow it to condense and flow into the tube, the vessel preferably aligned few degrees down so the liquid phossy will flow out. The reaction vessel will be filled with copious amounts of CO and H2 and it will dispace any air present long before wp is produced.

Although this source cites that hot phossy acid is compatible with quartz:

http://www.sciencedirect.com/science/article/pii/S0168583X12...

So, if it is so, by far the easiest way is to just find quartz flask, put in the reactants and dump this into micro.

http://fusedquartz.qsiquartz.com/viewitems/quartz-boiling-fl...

A suitable flask with joint seems to be in the 200usd price range. Jointing substantially simplifies the apparatus setup, since conventional lab glassware can be used past the boiling phosphoric acid point.

For europeans, non-jointed model may be an option.

http://www.witeg.de/1749797951/1/PD61/8610/art/8610/0/1/61+P...

[Edited on 8-2-2014 by testimento]

[Edited on 8-2-2014 by testimento]

Zyklon-A - 8-2-2014 at 07:36

Quote:

500 °C is just slightly beyond the temperature an ordinary stove top can achieve.

My hot plate can melt lead, zinc, and even aluminum once. So a least 660°C. My hot plate is not necessarily an 'ordinary' stovetop though.

[Edited on 8-2-2014 by Zyklonb]

testimento - 8-2-2014 at 08:21

All of my market bought hotplates can easily reach red hot temps. They're all in dumpyard at the moment though, since they failed - and I didn't even mishandled them, but used them to heat conductively as they're supposed to. After wasting loads of money for that crap, I switched to propane burners and had any problems. For high temp ops I use my oven which I've posted details on the other topic.

testimento - 8-2-2014 at 09:15

There's just one point regarding the patent cited in the first post. The amount of phosphorus produced per power of the microwave. With 1000 watts the test shows only of 4.4 grams in two hours. This does not state the time curve of formation - does it all form within first 10 minutes or is the production rate steady?

Because this means that one would need several kilowatts of magnetron power over very long period of time to produce even minimum amounts of phosphorus with this method, thus if this is the case, rendering this method obsolete for most amateur chemists.

Unless the reaction could be hastened by heating the reaction vessel all the way up to 1000C...?

Fantasma4500 - 15-3-2014 at 08:15

butane needs alot of oxygen to burn.. it can get somewhat violent when it reaches that amount however, but filling a bottle with butane and attempting to light it will often result in a failure as you can very easily add too much butane