making potassium (per) chlorate

[WSM]

I have a 5 liter reaction vessel (round bottom borosilicate glass) which I'm going to make into a little experimental sodium chlorate cell.

 

I plan to use a fairly thick polymer lid, drilled and tapped for compatible compression fittings, and plumb it for as many useful components as I feel will be useful for the purpose.

 

The plan, borrowed mostly from a patent Arthur kindly shared, involves running the cell at or near 110 degrees C, which will boil off excess water as the system runs.

 

This will naturally concentrate the chlorate product, to where crystalline NaClO3 will drop out of solution at room temperature, removing the need and expense of chilling the electrolyte in a refrigerator to harvest the chlorate.

 

Chlorides can be replaced using purified brine instead of laboriously preparing purified NaCl to use.

 

I have lots of ideas, developed over the past few years. If the cell is successful, I'll see if I can adapt it to run as a continuous system, to produce a large enough stock of pure sodium chlorate to continue my perchlorate experiments.

 

WSM

Edited September 13, 2019 by WSM

[WSM]

I forgot to mention that the 5 liter reaction flask has a large opening (+-150mm) and there's a groove for an O-ring in the flat flange around the opening.

 

With a compatible O-ring seal, a flat plate of thick polymer will make an excellent lid and closure for the cell.

 

We'll see...

 

WSM

[markx]

I have a 5 liter reaction vessel (round bottom borosilicate glass) which I'm going to make into a little experimental sodium chlorate cell.

 

I plan to use a fairly thick polymer lid, drilled and tapped for compatible compression fittings, and plumb it for as many useful components as I feel will be useful for the purpose.

 

The plan, borrowed mostly from a patent Arthur kindly shared, involves running the cell at or near 110 degrees C, which will boil off excess water as the system runs.

 

This will naturally concentrate the chlorate product, to where crystalline NaClO3 will drop out of solution at room temperature, removing the need and expense of chilling the electrolyte in a refrigerator to harvest the chlorate.

 

Chlorides can be replaced using purified brine instead of laboriously preparing purified NaCl to use.

 

I have lots of ideas, developed over the past few years. If the cell is successful, I'll see if I can adapt it to run as a continuous system, to produce a large enough stock of pure sodium chlorate to continue my perchlorate experiments.

 

WSM

You do not need to run the cell at boiling hot temperature to drop out the crop of sodium chlorate. Electorlysis/synthesis will spend some water and some will find it's way out as vapours leaving through the off gas conduit. By replenishing the spent water with concentrated brine you will eventually reach a critical concentration buildup of chlorate in the cell liqour and it will start to cristallise out from the solution. This crop can be regularly removed and you do not need to operate at high temperature for that. The question is how are you going to remove that crop without having to switch off and dissassemble the whole setup. From a technical perspective cooling is about the best method to remove the excess product in a continuous production scheme. The solution can be fed into a different vessel where it cools....drops out the chlorate and then flows back into the reactor vessel. This way the system can keep operating and no dissassembly is required to remove the product.

 

A boiling hot cell is really hard to control.....your rate of water loss shall not match up with the amount of chlorate produced and you have to replenish the electrolyte constantly with additional water instead of brine. Otherwise you shall quickly start to precipitate chlorides instead of chlorates. Not to mention a boiling system can not be left unsupervised: not good from the viewpoint of a continuous production concept. Also the high temperature limits the choice of materials you can use in the construction of the cell. Simpler and cheaper plastics like PP or PE which perform reasonably well in a moderate temperature cell will soften too much at 110C to provide structural integrity. Deformation, shrinkage and serious leaks are the result. Even 80C will make PP parts creep out of shape when they are under constant mechanical strain in/on an operating cell. My cell has a PP top plate that is grooved and seated with a PTFE gasket to keep the gases and liqour from creeping out. I operated it a about 80C maximum for a few days during chlorate synthesis and this was enough to warp the PP plate causing serious leaks and salt creep.

[WSM]

You do not need to run the cell at boiling hot temperature to drop out the crop of sodium chlorate. Electorlysis/synthesis will spend some water and some will find it's way out as vapours leaving through the off gas conduit. By replenishing the spent water with concentrated brine you will eventually reach a critical concentration buildup of chlorate in the cell liqour and it will start to cristallise out from the solution. This crop can be regularly removed and you do not need to operate at high temperature for that. The question is how are you going to remove that crop without having to switch off and dissassemble the whole setup. From a technical perspective cooling is about the best method to remove the excess product in a continuous production scheme. The solution can be fed into a different vessel where it cools....drops out the chlorate and then flows back into the reactor vessel. This way the system can keep operating and no dissassembly is required to remove the product.

A boiling hot cell is really hard to control.....your rate of water loss shall not match up with the amount of chlorate produced and you have to replenish the electrolyte constantly with additional water instead of brine. Otherwise you shall quickly start to precipitate chlorides instead of chlorates. Not to mention a boiling system can not be left unsupervised: not good from the viewpoint of a continuous production concept. Also the high temperature limits the choice of materials you can use in the construction of the cell. Simpler and cheaper plastics like PP or PE which perform reasonably well in a moderate temperature cell will soften too much at 110C to provide structural integrity. Deformation, shrinkage and serious leaks are the result. Even 80C will make PP parts creep out of shape when they are under constant mechanical strain in/on an operating cell. My cell has a PP top plate that is grooved and seated with a PTFE gasket to keep the gases and liqour from creeping out. I operated it a about 80C maximum for a few days during chlorate synthesis and this was enough to warp the PP plate causing serious leaks and salt creep.

 

 

In a sodium chlorate cell, the product is more soluble than the starting electrolyte. To be perfectly clear, sodium chlorate is much more soluble than the sodium chloride brine.

 

As the cell runs, the chlorate concentration increases as the chlorides decrease. When the run nears "competition" the depleted electrolyte is saturated with sodium chlorate but so much more water, that to remove the chlorate, one is required to either/or boil the electrolyte/chill it, to concentrate the product enough for it to drop out crystals of NaClO3.

 

Only a small portion of the sodium chlorate drops out of the electrolyte, leaving the remainder in solution.

 

I prefer not to boil down the electrolyte in recovering sodium chlorate, because it wastes a lot of energy and may also drop out some sodium chloride if I don't gauge the cutoff correctly between optimal chlorate recovery and the chlorides beginning to precipitate.

 

The beauty of the method described in the patent Arthur shared, is in it uses the nature of the component chemicals to the best advantage in the recovery of the desired product (sodium chlorate crystals) while keeping the chloride in solution and recharging the cell with brine rather than laboriously produced purified salt.

 

The whole process described minimizes the energy spent and maximizes the yield produced, so the initial expenditure (more specialized materials and setup of the high temperature cell) is overcome soon after it is run for a few cycles.

 

Due to the anticipated temperatures and compatibility issues, polymers aren't used in contact with the electrolyte. The choice of cell container in this case is borosilicate glass. Less compatible polymer components are designed to function away from direct contact with the cell liquor, besides PTFE or other such tubing allowed to transfer hot electrolyte to a room-temperature crystallization chamber for crystal recovery. The remaining solution in the recovery container is then mixed with fresh, purified brine and returned to the cell for continued runs.

 

By utilizing the temperature and solubilities to the greatest advantage, more product can be produced with less energy expenditure and time consumption.

 

WSM

Edited September 19, 2019 by WSM

[markx]

In a sodium chlorate cell, the product is more soluble than the starting electrolyte. To be perfectly clear, sodium chlorate is much more soluble than the sodium chloride brine.

 

As the cell runs, the chlorate concentration increases as the chlorides decrease. When the run nears "competition" the depleted electrolyte is saturated with sodium chlorate but so much more water, that to remove the chlorate, one is required to either/or boil the electrolyte/chill it, to concentrate the product enough for it to drop out crystals of NaClO3.

 

Only a small portion of the sodium chlorate drops out of the electrolyte, leaving the remainder in solution.

 

I prefer not to boil down the electrolyte in recovering sodium chlorate, because it wastes a lot of energy and may also drop out some sodium chloride if I don't gauge the cutoff correctly between optimal chlorate recovery and the chlorides beginning to precipitate.

 

The beauty of the method described in the patent Arthur shared, is in it uses the nature of the component chemicals to the best advantage in the recovery of the desired product (sodium chlorate crystals) while keeping the chloride in solution and recharging the cell with brine rather than laboriously produced purified salt.

 

The whole process described minimizes the energy spent and maximizes the yield produced, so the initial expenditure (more specialized materials and setup of the high temperature cell) is overcome soon after it is run for a few cycles.

 

Due to the anticipated temperatures and compatibility issues, polymers aren't used in contact with the electrolyte. The choice of cell container in this case is borosilicate glass. Less compatible polymer components are designed to function away from direct contact with the cell liquor, besides PTFE or other such tubing allowed to transfer hot electrolyte to a room-temperature crystallization chamber for crystal recovery. The remaining solution in the recovery container is then mixed with fresh, purified brine and returned to the cell for continued runs.

 

By utilizing the temperature and solubilities to the greatest advantage, more product can be produced with less energy expenditure and time consumption.

 

WSM

Yes of course chlorate is way more soluble in a sodium dominated electrolyte system compared to chloride. I apologize for the fact that I have not read the patent that was mentioned, hence my understanding of the final objective related to this approach is somewhat vague. What I was trying to say is that the electrosynthesis cell, as long as it is run, will keep creeping towards the increase of chlorate concentration indiscriminate of cell temperature or the way it is replenished with chlorides.

Do I understand correctly that you wish to operate the reactor at an excess of 100C to increase the evaporative removal of water for concentrating the electrolyte faster? Then drop out the maximum cristal crop in a separate cooling vessel and turn it to solid chlorate stock for further perchlorate conversion?

[WSM]

Do I understand correctly that you wish to operate the reactor at an excess of 100C to increase the evaporative removal of water for concentrating the electrolyte faster? Then drop out the maximum cristal crop in a separate cooling vessel and turn it to solid chlorate stock for further perchlorate conversion?

 

Yes, evaporating the water to concentrate the chlorate is a major part of making this system work efficiently.

 

When the concentrated electrolyte cools from 110 degrees C to room temperature, a portion of the sodium chlorate will drop out of solution as crystals. The remainder of the electrolyte is then recharged with purified brine and returned to the cell to continue making more chlorate.

 

Making the NaClO3 crystals is crucial to my KClO4 research because I don't have an available source for sodium chlorate, so I'm creating it from materials I can get.

 

I use the sodium chlorate to form the electrolyte that is processed in a perchlorate cell to sodium perchlorate, using either lead dioxide or platinum anodes with titanium cathodes.

 

I separate the two processes (chloride to chlorate and chlorate to perchlorate) because it's simpler to keep the quality up of the products if I watch each step carefully. These two systems so different from each other that I treat and run them completely differently.

 

WSM

Edited September 20, 2019 by WSM

[markx]

Yes, evaporating the water to concentrate the chlorate is a major part of making this system work efficiently.

 

When the concentrated electrolyte cools from 110 degrees C to room temperature, a portion of the sodium chlorate will drop out of solution as crystals. The remainder of the electrolyte is then recharged with purified brine and returned to the cell to continue making more chlorate.

 

Making the NaClO3 crystals is crucial to my KClO4 research because I don't have an available source for sodium chlorate, so I'm creating it from materials I can get.

 

I use the sodium chlorate to form the electrolyte that is processed in a perchlorate cell to sodium perchlorate, using either lead dioxide or platinum anodes with titanium cathodes.

 

I separate the two processes (chloride to chlorate and chlorate to perchlorate) because it's simpler to keep the quality up of the products if I watch each step carefully. These two systems so different from each other that I treat and run them completely differently.

 

WSM

 

May I ask why you insist on bringing the sodium chlorate stock into dry form? Would it not be more convenient to keep it in the form of concentrated solutions prior to workup into perchlorate?

 

At least that is the way I've done it and it simplifies the process considerably: standard Ti/MMO electrosynthesis to form chlorate from chlorides which is fed into perchlorate cell in the form of concentrated solution as the next step. Your approach seems to go through a lot of effort to temporarily remove the water from a system that will have to be finally handled in the form on solutions anyway.

 

If you are worried about contaminants and trying to increase the purity of the stock by bringing it into dry form for perchlorate synthesis, then ease your mind: chloride content is not a problem for Pt anode and the rest of impurities seem to always precipitate in the form of a gel like sediment in the last stages of perchlorate conversion. Even visibly contaminated chlorate stock solutions (e.g. contaminated by metallic salts formed from alloying elements in low grade Ti) clear up completely in perchlorate synthesis stage, yielding a very clean solution.

[WSM]

May I ask why you insist on bringing the sodium chlorate stock into dry form? Would it not be more convenient to keep it in the form of concentrated solutions prior to workup into perchlorate?

 

 

I have a few reasons for striving to make dry crystalline sodium chlorate.

 

First, I feel it's easier to calculate the end-of-run in my perchlorate cell if I start with a known concentration in the electrolyte. This way I know the exact quantity of chlorate that's in my starting electrolyte.

 

Also, my goal in making sodium chlorate is to make a large enough stock of it that I can do a good amount of perchlorate research all at one time, and with the same stockpile, without waiting for several different runs of chlorate to be completed.

 

Finally, in my opinion; I think it's safer, more controllable and convenient to store NaClO3 as a dry, crystalline substance than as a liquid.

 

WSM

Edited September 20, 2019 by WSM

[Arthur]

Perhaps there is some reason why industrial oxidiser producers use the process that they do, extracting the dried chlorate first. Most times recrystalisation is done to increase the purity and get rid of reaction by-products, and get rid of surplus water.

 

One real issue for amateurs is keeping the waste minimised! A few gallons of chlorate waste will be enough to stop a local waste water plant, or kill vegitation for miles.

[WSM]

One real issue for amateurs is keeping the waste minimised! A few gallons of chlorate waste will be enough to stop a local waste water plant, or kill vegitation for miles.

 

Arthur makes a good point. We need to contain our experiments or we're likely to cause an environmental disaster.

 

Chlorate, and sodium chlorate in particular, is an indescriminant herbicide. It kills all plants, and "salts" the earth so nothing will grow there for a long time, if ever.

 

It behooves us to keep our cell in a compatible containment, such as a plastic tub or some other form to prevent a spill from causing harm.

 

There are other considerations but I'll leave it at that for now.

 

WSM

Edited September 22, 2019 by WSM

[Arthur]

Another point is that we start with hot saturated brine and add brine solution as the reaction progresses so there is increasing cell liquid volume which we wish would not increase so some water losses by evaporation are very helpful in maintaining a reaction liquor of reasonable concentration and saturation.

 

When the second stage cell reaches completion we add saturated KCl to cause the Na perc to ppt out as crystals (rate of addition and temperature govern final crystal size). This means that this cell increases in volume too. This exhausted liquor becomes the NaCl solution that needs saturating to reuse as chlorate cell feedstock. You concentrate it either by adding NaCl and getting an increasing volume of liquor or by removing water.

 

In practice there will be other losses of chemicals and gain of hazards, Simply wiping up spills or drips leaves a oxidiser filled cloth or paper to dry and become easily or spontaneously flammable.

[WSM]

In practice there will be other losses of chemicals and gain of hazards, Simply wiping up spills or drips leaves a oxidiser filled cloth or paper to dry and become easily or spontaneously flammable.

 

 

Arthur has made another good point. When you have a hot sodium chlorate solution, it's extremely important not to let it come into contact with organic material.

 

This is a problem when we use cellulose filter paper to separate crystals from the remaining electrolyte, because the wet filter paper becomes a serious flame hazard when it dries.

 

This came home for me when I had several such papers to dispose of. I took them out to the barbecue grill and when I "carefully" lit the corner of one, imagine my surprise when it burned VERY quickly, almost like flash paper. Luckily, I was wearing an FR (flame resistant) T-shirt, which did its job and protected my skin. Unfortunately, my FR T-shirt was afterwards peppered with a fair number of very small, black spots (holes) after this experience.

 

Sodium chlorate coated organic material can be treacherous. Be careful, and dispose of it safely, in SMALL quantities, one at a time and using an ignition device that separates you from the hazard.

 

WSM

Edited October 4, 2019 by WSM

[pyrojig]

To chime in , I believe industry produces dried materials v.s. in solution because of volume and weight for storage.cost and storage space is crucial.

I too have been surprised by how reactivate filter paper and or a clean up rag can be with chlorate in it. Very sobering. I lost arm hair in my experience. Lol, wsm is smart to have proper attire.

I often wonder if the chlorate contaminated soils they used to spray with herbicide eventually went inert. I've almost considered attacking poison oak with that stuff, but fear the lasting results or contamination would not be desirable.

[WSM]

Things are starting to come together. I think that 2020 will be the year I'll be getting back to working on my research.

 

The plans include an independent power source, a pure water source and improved cells to run & evaluate.

 

It'll be a busy and (hopefully) productive year.

 

WSM

[WSM]

I have a new RO (reverse osmosis) system in its original box, and acquired a DI (de-ionizing) filter to add to the partially pure water output which will remove the remaining 10% or less of dissolved solids to yield 0% dissolved solids (i.e.,PURE water) to use in my experiments!

 

I'm anxious to get started on this phase of my experiments!!!

 

WSM

Edited November 7, 2019 by WSM

[WSM]

US patent 3,043,757 (originally filed over 60 years ago) is the source of the information I'm using in my "high temperature" sodium chlorate cell experiment.

 

The patent explains the MANY benefits of running the cell this way, and the more I study it, the more I'm convinced it's worth trying their system out as a "proof of concept" test.

 

Many thanks to Arthur for finding and sharing this patent with me.

 

I plan to run a 4 liter cell and see if it works as well as I hope it will.

 

WSM

Edited November 7, 2019 by WSM

[WSM]

US patent 3,043,757 (originally filed over 60 years ago).

I plan to run a 4 liter cell and see if it works as well as I hope it will.

WSM

 

The tank I'm using is a 5-liter, round bottom, borosilicate glass reaction flask with a large gasketed opening, which I plan to fill with 4 liters of electrolyte.

 

I'm planning to fabricate a 3/4" (+-19mm) thick PVC lid for the cell from flat sheet stock. This lid will be prepared with a lot of tapped ports for many fittings and purposes; not just the leads and a vent. The patent mentions several of these options (for research and "proof of concept" of the system) and are worth considering.

 

I'm not sure if the laboratory glass is resistant to the effects of strong alkali (which chlorate cells generate naturally), so one of the ports will be for pH control by acid injection to keep the mother liquor at or slightly below a neutral pH (which will also create optimal conditions for the highest performance and efficiency within the cell!).

 

I plan to work on the custom lid and put the experimental cell into service before next Summer.

 

WSM

Edited November 17, 2019 by WSM

[abc159201]

The tank I'm using is a 5-liter, round bottom, borosilicate glass reaction flask with a large gasketed opening, which I plan to fill with 4 liters of electrolyte.

 

I'm planning to fabricate a 3/4" (+-19mm) thick PVC lid for the cell from flat sheet stock. This lid will be prepared with a lot of tapped ports for many fittings and purposes; not just the leads and a vent. The patent mentions several of these options (for research and "proof of concept" of the system) and are worth considering.

 

I'm not sure if the laboratory glass is resistant to the effects of strong alkali (which chlorate cells generate naturally), so one of the ports will be for pH control by acid injection to keep the mother liquor at or slightly below a neutral pH (which will also create optimal conditions for the highest performance and efficiency within the cell!).

 

I plan to work on the custom lid and put the experimental cell into service before next Summer.

 

WSM

 

 

In my experience, those laboratory glassware aren't able to withstand the harsh condition very well. I had used 3L beaker(Borosilicate) as my cell without any pH control before. It got corroded and leave lots of small dents within 1~2 months. Now I use normal glass jar(bought from IKEA , pretty sure it's not Borosilicate) with crappy pH control, and it seems untouched after 3 months of usage.

[WSM]

In my experience, those laboratory glassware aren't able to withstand the harsh condition very well. I had used 3L beaker(Borosilicate) as my cell without any pH control before. It got corroded and leave lots of small dents within 1~2 months. Now I use normal glass jar(bought from IKEA , pretty sure it's not Borosilicate) with crappy pH control, and it seems untouched after 3 months of usage.

Thanks for the input. I was thinking it may be a problem, so I planned to use pH control to maintain the hot electrolyte between a pH reading of 6.5 and 7.0, if I can.

 

I'm using borosilicate glass because the plan is to run the cell at about 110 degrees Celsius. I can't think of anything else to use that's affordable, but I'm open to suggestion.

 

WSM

Edited November 24, 2019 by WSM

[Arthur]

One cell that used Swedes MMO had a suspect issue with the glass being forced into the cell liquid and passivating the MMO.

[WSM]

One cell that used Swedes MMO had a suspect issue with the glass being forced into the cell liquid and passivating the MMO.

 

That's true, but we didn't discover which type of glass it was, did we?

 

I did a little research on borosilicate glass and one source claimed a pH range of 3-10. I'm sure temperature plays in this as well...

 

WSM

[abc159201]

Thanks for the input. I was thinking it may be a problem, so I planned to use pH control to maintain the hot electrolyte between 6.5 and 7.0 if I can.

 

I'm using borosilicate glass because the plan is to run the cell at about 110 degrees Celsius. I can't think of anything else to use that's affordable, but I'm open to suggestion.

 

WSM

 

If you design your cell adding brine constantly instead of batched, I think maybe using normal glass is still a viable idea.

Also,pH control will be difficult since HCl vapor should escape pretty easily. Looks like this experiment gonna needs a lot of work.

BTW I think use PVC as cell lid at such high temp is a bad idea. Although it has decent thickness, I doubt it will hold more than a week. Deformation and degradation will be a serious issue. Maybe cPVC or PTFE ?

Edited November 20, 2019 by abc159201

[Arthur]

The issue for the amateur constructor is always price. If a big entity is to produce millions worth per year then a few hundred for a sheet of PTFE is viable. For an amateur truly minimising the cost is important even at some reduction in performance. For each of us the price vs lifetime calculation has to be different.

[abc159201]

The issue for the amateur constructor is always price. If a big entity is to produce millions worth per year then a few hundred for a sheet of PTFE is viable. For an amateur truly minimising the cost is important even at some reduction in performance. For each of us the price vs lifetime calculation has to be different.

 

Base on wiki, PVC max operating temperature is around 60°C,and start degrading around 70°C.And more importantly, its Tg is 82°C. Using PVC at 110°C will definitely make it become soft and malleable. I'm not quite sure whether making the lid thicker will solve this problem or not...

[WSM]

If you design your cell adding brine constantly instead of batched, I think maybe using normal glass is still a viable idea.

Also,pH control will be difficult since HCl vapor should escape pretty easily. Looks like this experiment gonna needs a lot of work.

BTW I think use PVC as cell lid at such high temp is a bad idea. Although it has decent thickness, I doubt it will hold more than a week. Deformation and degradation will be a serious issue. Maybe cPVC or PTFE ?

 

If you read through Swede's blog, the acid injection problem is solved by introducing it slowly, deep UNDER the surface of the electrolyte so the HCl stays in the solution (doing its work), rather than boiling off.

 

Remember, the PVC is not in direct contact with the hot electrolyte, but several inches above it. The temperature the PVC rises to is yet to be determined by experimentation. The original patent writer used 1" thick plexiglas for a lid, in a similar setup.

 

We'll see how it works in practice, rather than doom it before we try.

 

WSM

Edited November 24, 2019 by WSM