making potassium (per) chlorate

[WSM]

I took a quick peek at them yesterday. I think I can fix it. It looks like the difference between parts 5 and 6, and the ones from before, are that the previously the pictures looked like they were hosted in the gallery as opposed to being directly attached. I don't know why it makes such a difference. There's a roundabout way to fix them though. I'll play around a little bit this weekend. Happy holidays.

 

That's awesome, Mumbles. Thanks.

 

Merry Christmas!

 

WSM

[WSM]

I just added Part Seven to the blogs, which begins to discuss perchlorate manufacture. When Mumbles fixes the other recent blogs, maybe he'll add this one to the list (Thanks, Mumbles).

 

WSM

[WSM]

In the spirit of the season, I just added Part Eight to the blogs. This part continues the preparation of electrodes and attendant equipment to run the sodium perchlorate cell.

 

In the next article (Part Nine) is shown the operation of the Platinum & LD cells and their production of sodium perchlorate.

 

After that, the following article (Part Ten) details the purification of the sodium perchlorate and it's conversion to (chlorate-free) potassium perchlorate.

 

WSM

Edited December 25, 2015 by WSM

[pyrojig]

Thanks for taking the time to share your work with us. It s a real pleasure learning and getting inspired to making one's own oxidizers . I have fallen more in love with electrochemistry lately ( last few years) .

[WSM]

Happy New Year!

 

I plan to set up my initial sodium chlorate cell experiments soon. If I can make lots of sodium chlorate, it's going into the sodium perchlorate cells.

 

I want to see if homegrown sodium chlorate will make sodium perchlorate as simply as the commercial sodium chlorate samples did. If so, I plan to test the longevity of both the platinized titanium and the lead dioxide anodes in their respective perchlorate cells. Those tests will be featured in future articles for the PGI Bulletin (and eventually posted as blogs here at APC).

 

WSM

Edited January 2, 2016 by WSM

[WSM]

Thanks for taking the time to share your work with us. It s a real pleasure learning and getting inspired to making one's own oxidizers . I have fallen more in love with electrochemistry lately ( last few years) .

 

To start my sodium chlorate cell (and because I want a large amount of NaClO₃ for feeding the sodium perchlorate cells), I've taken a large PVC tank I built years ago for a huge KClO₃ continuous system (that was never finished), and I'm re-purposing it for large volume sodium chlorate production.

 

The PVC tank is fabricated from a 20" long (~48 cm) piece of 12" Schedule 40 PVC pipe, cemented to a square piece of 1/2" thick clear PVC plate. The tank has a 1/2" PVC ball valve on the bottom side wall, and a 1" PVC union, 14" up from the bottom, 90^o counterclockwise from the bottom valve. The working volume is calculated to be about 27 liters, or a bit more than 7 gallons of liquid.

 

The tank has a rough cut lid of 1/2" thick clear PVC plate with a PVC support ring glued on with PVC cement, and a silicone tubing seal, attached with silicone RTV; to keep salt creep to a minimum.

 

I still need to drill and tap the lid for various fittings to accommodate the electrodes, vent and assorted sensors. For safety, I'll place the cell in a low, wide tub as a containment reservoir in case a leak forms (safety first).

 

I'll try to take photos later and attach them, so this setup is clearer than just verbal descriptions.

 

WSM

[WSM]

The large tank I referred to this past week is a bit rough in appearance but I've water tested it and it's sound and leak free.

 

 

The 1" union has a reducing bushing and a 1/2" threaded plug inserted to temporarily close it till I get a chance to set the cell up to run.

 

More later...

 

WSM

[WSM]

I hope to fabricate an electrode set Monday since I have it off as a holiday (Thank you, MLK).

 

The power supply I'm considering using is a (physically small) 5 Vdc, 55 A dc unit I bought on eBay some time ago. The anode is some laserred MMO I got from Swede about 6 or 7 years ago, if I'm not mistaken.

 

Sized to demand 44 amps I'm cutting the MMO mesh to 2.875" by 4" and planning on using two cathode plates to surround it (for higher efficiency). I think I'll use 1/2" OD titanium tubing for leads and fill them each with (up to) a 3/8" copper rod (threaded on the end sticking out) and lead-free solder for higher conductivity, lower resistance and hopefully cooler running.

 

This should be a grand experiment for my first sodium chlorate cell. We'll see how it goes...

 

WSM

 

Edit: If the small power supply doesn't work out, I have a rack-mount beast, rated at 5 Vdc and 60 A that should handle the job easily.

Edited January 17, 2016 by WSM

[WSM]

As I was studying the subject this morning, it re-occurred to me that the fundamental differences between perchlorates of sodium and potassium dictate separate approaches to the cell setup.

 

Due to the solubilities, I think sodium system electrodes are better placed close to each other, and potassium system electrodes are better placed further away from each other. In fact, the higher the solubility of the material being produced, the closer the electrodes can be.

 

Mesh anodes work fine and are preferred with higher solubility compounds in solution. I suspect solid sheet and smooth surfaced anodes would work better in a system designed to do something so difficult as potassium chlorate to perchlorate conversion, probably also with greater spacing between them (plus higher fluid temperatures and greater velocity of the liquor).

 

I'd like to try the experiment some time on a small scale, and test my theory. It would be interesting to see if it works at all, and also how well it works.

 

WSM

Edited January 17, 2016 by WSM

[Arthur]

IMO electrolysing KCl is for when you make K chlorate only. NaCl electrolyses to sodium chlorate as an ingredient to the sodium perc and K perc stages.

[WSM]

IMO electrolysing KCl is for when you make K chlorate only. NaCl electrolyses to sodium chlorate as an ingredient to the sodium perc and K perc stages.

 

That's what I've done so far. My main focus at this point in time is electrolyzing NaCl to NaClO₃ and using that for sodium perchlorate feed stock.

 

Direct electrolysis of KClO₃ to KClO₄ is a possible side trip (or maybe just a distraction).

 

WSM

Edited January 18, 2016 by WSM

[MrB]

I admit, if i ever run out of perclorate, i'm not going to skip through hoops, and go from NaCl to KClO4. For it to be a useful process it has to be possible to go straight from KCl to KClO4, With pretty much only time and electricity as the factors involved.

We know this is possible, but getting a chlorate free product will still require an extra step, heating it to get the chlorate to decompose back to KCl, and dissolve it in water, to go back in to the system as top-up water. It has it's drawbacks, any organic matter in the system at that point, and you might be looking at a poorly optimized flash charge, that will go off. Not something to stand to close to. Relying on KClO4's lower solubility and try to wash out the KClO3, is safer, but might produce "to much" top-of feedstock, forcing you to reduce it by evaporation.Also, the result of heating to decompose back to KCl is supposedly more reliable, leaving less chlorate in the end product. Something that might be important, depending on your use for it.

In my case, i pretty much only use potassium perchlorate for colors, and then using the Veline color-system, so i might just skip that step, try and run the cell for as long as possible without damage to the anode, and take the chlorate contamination for what it is.

 

Direct electrolysis of KClO₃ to KClO₄ is a possible side trip (or maybe just a distraction).

 

What ever you end up doing, i'll read it, if put on the blog. If nothing else, it gives some insights to the workings of a functioning system.

B!

[Arthur]

The issue with the K salt process is the much lower solubility, so it's far too easy to destroy the expensive platinum electrode or all but the best lead dioxide electrode.

[taiwanluthiers]

I couldn't really make any perchlorate using the potassium process. It was impossible to keep the temperature up (and therefore solubility) and even then the current draw was less than 1 amp. I also completely destroyed a platinum anode this way. I have no idea how Swede did it...

[schroedinger]

Well didn't swede just heat the cell?

If you have problems with to rapid cooling od the cell, maybe it could be interesting to make a cell from a eski. That should provide sufficient insulation.

 

My first cell used a dewar bottle. Don't use them, you will be amazed how fast a cell will cook.

[MrB]

Insulating it, quite possibly use a titanium aquarium heater in the system, but if the container is made of something with reasonable heat transfer properties, wrap a terrarium heater around it, and then add the insulation. It shouldn't be hard to keep the system between 35 and 50c which is the "temperature zone" to be in, if i remember right. The main problem would be the size of the system, since i'd like to make it somewhat larger, from acid-proof stainless steel, and use the reaction chamber as the cathode. (Acid-proof stainless steel grades shouldn't lead to chromium contamination, and the performance reduction on the LD anode. Easy enough to tell if it does happen, the liqueur turns yellowish.)

 

Anyway, it's not anywhere near happening.

B!

[taiwanluthiers]

If you are using acid proof stainless steel, use the container as cathode and it will be protected.

[WSM]

IMO electrolysing KCl is for when you make K chlorate only. NaCl electrolyses to sodium chlorate as an ingredient to the sodium perc and K perc stages.

 

My thought is: I'm only considering duplicating Swede's conversion of KClO₃ to KClO₄, and only as a small scale experiment; to satisfy my curiosity.

 

I'm convinced the best route to perchlorates for me is through the sodium pathway. It is MUCH, much more convenient than the uphill battle and costliness of a strictly potassium system for perchlorates.

 

WSM

Edited January 24, 2016 by WSM

[WSM]

I admit, if i ever run out of perclorate, i'm not going to skip through hoops, and go from NaCl to KClO4. For it to be a useful process it has to be possible to go straight from KCl to KClO4, With pretty much only time and electricity as the factors involved.

We know this is possible, but getting a chlorate free product will still require an extra step, heating it to get the chlorate to decompose back to KCl, and dissolve it in water, to go back in to the system as top-up water. It has it's drawbacks, any organic matter in the system at that point, and you might be looking at a poorly optimized flash charge, that will go off. Not something to stand to close to. Relying on KClO4's lower solubility and try to wash out the KClO3, is safer, but might produce "to much" top-of feedstock, forcing you to reduce it by evaporation.Also, the result of heating to decompose back to KCl is supposedly more reliable, leaving less chlorate in the end product. Something that might be important, depending on your use for it.

In my case, i pretty much only use potassium perchlorate for colors, and then using the Veline color-system, so i might just skip that step, try and run the cell for as long as possible without damage to the anode, and take the chlorate contamination for what it is.

What ever you end up doing, i'll read it, if put on the blog. If nothing else, it gives some insights to the workings of a functioning system.

B!

 

Thanks for the comments, MrB. After all my efforts over the past >decade; I've found the most effective means of producing potassium chlorate is directly from potassium chloride electrolytically.

 

Potassium perchlorate on the other hand has been a major hurdle, and primarily because of the solubilities involved. Even Swede's efforts, as successful as he was, didn't overcome that one major fact; if you try to make a potassium-only perchlorate cell (except with extreme conditions) it will get clobbered with crystals. It'll be comparable to casting concrete in your system and then trying to re-use everything.

 

The simplest (and least expensive) method of potassium perchlorate manufacture out there (at this point in time) is to:

• electrolyse sodium chlorate to sodium perchlorate
• remove residual chlorates from the sodium perchlorate solution
• convert the purified solution to potassium perchlorate by metathesis with KCl
• purify the new potassium perchlorate of the soluble sodium contaminants
• dry and store the potassium perchlorate for future use

It's much more difficult involved than making potassium chlorate, but certainly NOT impossible. It's a different process.

 

WSM

Edited January 24, 2016 by WSM

[WSM]

The issue with the K salt process is the much lower solubility, so it's far too easy to destroy the expensive platinum electrode or all but the best lead dioxide electrode.

 

This is true. Moderate success is had with tight controls of the power and cell conditions. Using a chlorate setup and perchlorate electrodes will lead to premature failure of the electrodes, as evidenced by the many headaches others here have shared.

 

I think I succeeded, so far, only through careful research and control of the system with deliberate controls put in place before I started.

 

WSM

[WSM]

Insulating it, quite possibly use a titanium aquarium heater in the system, but if the container is made of something with reasonable heat transfer properties, wrap a terrarium heater around it, and then add the insulation. It shouldn't be hard to keep the system between 35 and 50c which is the "temperature zone" to be in, if i remember right. The main problem would be the size of the system, since i'd like to make it somewhat larger, from acid-proof stainless steel, and use the reaction chamber as the cathode. (Acid-proof stainless steel grades shouldn't lead to chromium contamination, and the performance reduction on the LD anode. Easy enough to tell if it does happen, the liqueur turns yellowish.)

Anyway, it's not anywhere near happening.

B!

 

I considered, long ago, an immersion heater like you describe. I think it would only work if the titanium shell were electrically connected to the cathode, which would afford the titanium a measure of protection.

 

I avoided the problem by keeping any metals out of the cell (except the electrodes, of course) and so I don't have to worry about unwanted side reactions.

 

The nice thing about our cells is heaters can be eliminated by careful and deliberate design. All of my electrochemical experiments generate heat and too often that heat is seen as a problem. The heat generated also improves the performance of the cell, so it's not all a waste.

 

A well designed system heats itself, and can be fine tuned to be very effective.

 

 

WSM

Edited January 24, 2016 by WSM

[MrB]

I considered, long ago, an immersion heater like you describe. I think it would only work if the titanium shell were electrically connected to the cathode, which would afford the titanium a measure of protection.

 

Doable, but less then ideal. In my case, i would forgoe the Ti heater, and use the terrarium style, just wrap the heater around the outside of my reaction chamber, and use the stainless steel it's made from as the cathode. In a attempt to try and eliminate the build up of crystals below the anode, i want to run a 2 chamber system, and use a magnetic stirrer in the smaller and "up top" placed reaction chamber, using the centripetal force to push both fluids, and solids out in to the larger chamber. Creating a downwards flow past the anode, which should help keeping it cooled as well.

In theory that would let me run a overcharged KCl system, where chloride would dissolve as it goes along, the (per)chlorate should end up at the bottom of the larger chamber, where it can be collected, possibly through siphoning it out. Return the liqueur, or boil it down to make room for the washwater produced in a bit, and then proceed to heat the crystals to 400c. Some of it should melt, and slowly return to solid as it decomposes, clearing away the chlorate, and leaves you with chloride, and perchlorate. At this point, washing it with purified water should dissolve mostly chloride, and leave me with fairly pure perchlorate. The washwater will contain some perchlorate as well, and i wont lose it since it gets used as top up for the system. At this point i would just add more salt, and start it again. I'm sure there is a number of ways this isn't going to work, or at least could fail, and over time, impurities from the purified water, handling it, or even the stainless steel, will build up, and the system needs to be flushed. That is, assuming the anode survives in the first place. As luck might have it, LD anodes is supposedly the best, and quite possibly the only option for a useful, surviving anode in a system like this.

PT apparently gets eaten if there is chloride in a perchlorate producing system, and nothing else gets close.

 

 

I avoided the problem by keeping any metals out of the cell (except the electrodes, of course) and so I don't have to worry about unwanted side reactions.

 

Yeah. If at all possible, i intend to use insulation, and possibly the terrarium heater. If memory serves me right the system "should" be benefiting from having the heat applied to the larger chamber, and not the reaction chamber, but i think we mentioned that briefly earlier, and the general opinion was that there wont be enough secondary reactions to make that relevant. So i will most likely just apply it to the reaction chamber, since the larger vessel might be plastic, with a couple of bulkheads to connect my stainless steel reactor.

 

 

The nice thing about our cells is heaters can be eliminated by careful and deliberate design. All of my electrochemical experiments generate heat and too often that heat is seen as a problem. The heat generated also improves the performance of the cell, so it's not all a waste.

 

A well designed system heats itself, and can be fine tuned to be very effective.

 

Higher temps means more dissolved salts, which in turn means a more productive system. But in the case of LD anodes the few advice i've seen all suggest keeping it below 50c, preferably "as low" as 45. "Safe limit" being 55c, and catastrophic failure limit around 75c. Running it anywhere near the 300mA limit of the LD anode suggested current for perchlorate production should ensure a steady heatsource, but i think i much rather play safe, and drop lower.

 

Anyway, it's just theory, and wishful thinking. I might have screwed up badly somewhere, and will, when it gets pointed out, head of in shame, never to bee seen again. (Yeah.... right. I have no shame.) If i did screw up, it's a lot better to get it pointed out well before investing a lot of time and effort in it. It can either get fixed, or replaced with a different idea.

B!

Edited January 25, 2016 by MrB

[WSM]

Doable, but less then ideal. In my case, i would forgoe the Ti heater, and use the terrarium style, just wrap the heater around the outside of my reaction chamber, and use the stainless steel it's made from as the cathode. In a attempt to try and eliminate the build up of crystals below the anode, i want to run a 2 chamber system, and use a magnetic stirrer in the smaller and "up top" placed reaction chamber, using the centripetal force to push both fluids, and solids out in to the larger chamber. Creating a downwards flow past the anode, which should help keeping it cooled as well.

In theory that would let me run a overcharged KCl system, where chloride would dissolve as it goes along, the (per)chlorate should end up at the bottom of the larger chamber, where it can be collected, possibly through siphoning it out. Return the liqueur, or boil it down to make room for the washwater produced in a bit, and then proceed to heat the crystals to 400c. Some of it should melt, and slowly return to solid as it decomposes, clearing away the chlorate, and leaves you with chloride, and perchlorate. At this point, washing it with purified water should dissolve mostly chloride, and leave me with fairly pure perchlorate. The washwater will contain some perchlorate as well, and i wont lose it since it gets used as top up for the system. At this point i would just add more salt, and start it again. I'm sure there is a number of ways this isn't going to work, or at least could fail, and over time, impurities from the purified water, handling it, or even the stainless steel, will build up, and the system needs to be flushed. That is, assuming the anode survives in the first place. As luck might have it, LD anodes is supposedly the best, and quite possibly the only option for a useful, surviving anode in a system like this.

PT apparently gets eaten if there is chloride in a perchlorate producing system, and nothing else gets close.

Yeah. If at all possible, i intend to use insulation, and possibly the terrarium heater. If memory serves me right the system "should" be benefiting from having the heat applied to the larger chamber, and not the reaction chamber, but i think we mentioned that briefly earlier, and the general opinion was that there wont be enough secondary reactions to make that relevant. So i will most likely just apply it to the reaction chamber, since the larger vessel might be plastic, with a couple of bulkheads to connect my stainless steel reactor.

Higher temps means more dissolved salts, which in turn means a more productive system. But in the case of LD anodes the few advice i've seen all suggest keeping it below 50c, preferably "as low" as 45. "Safe limit" being 55c, and catastrophic failure limit around 75c. Running it anywhere near the 300mA limit of the LD anode suggested current for perchlorate production should ensure a steady heatsource, but i think i much rather play safe, and drop lower.

Anyway, it's just theory, and wishful thinking. I might have screwed up badly somewhere, and will, when it gets pointed out, head of in shame, never to bee seen again. (Yeah.... right. I have no shame.) If i did screw up, it's a lot better to get it pointed out well before investing a lot of time and effort in it. It can either get fixed, or replaced with a different idea.

B!

 

I ran my LD anode at 100mA and it was very happy (it ran at almost textbook levels and was "happy" [no serious degradation]), plus much less ozone production.

 

I think most people try to run their LD and Pt anodes like MMO and kill them in the effort. Maybe we need to think differently about the perchlorate process and treat the anodes so they'll go the distance instead of get destroyed trying to do things they weren't designed to do.

 

WSM

[Arthur]

Fortunately the first process is adding three oxygen atoms to a chloride but the second process is adding only one oxygen to a chlorate ion so the current used for electrolysis can be one third of the chlorate cell current (OK there are some side reactions in both cells and some IR heating.).

[WSM]

Fortunately the first process is adding three oxygen atoms to a chloride but the second process is adding only one oxygen to a chlorate ion so the current used for electrolysis can be one third of the chlorate cell current (OK there are some side reactions in both cells and some IR heating.).

 

Yes, the perchlorate cells (both types) got warm as they ran, but not to an excessive level (between 45^o C and 46^o C). The current density for my two cells were 0.1A/cm² for the LD and 0.2A/cm² for the Pt cells. As I recall, the heat rise was gradual and stabilized after, say, maybe 10 hours?! I have notes somewhere but will have to record the details better during my next runs (after I get more NaClO₃).

 

The main focus of my current research is building and running a sodium chlorate cell so I can build up a supply of feed-stock for my perchlorate experiments.

 

WSM