Sciencemadness Discussion Board - Cheapest Source of Chlorine

Cheapest Source of Chlorine

4-Stroke - 19-11-2024 at 12:12

Hello. I am wondering what the cheapest source of chlorine is. It seems like calcium hypochlorite and TCCA are most often used by amateurs to generate chlorine. They both are, however, expensive. Where I live, TCCA costs about $8 per kilogram (when bought in 10kg tubs, the largest size available in Canadian Tire), and calcium hypochlorite costs about $5 per kilogram (when bought in 18kg tubs, also the largest size available). Calcium hypochlorite is a little cheaper, but requires more hydrochloric acid, so the cost comes out pretty much equal. Muriatic acid costs about $16 per 4L. Both TCCA and Ca(OCl)₂ have around ~50% chlorine available by mass, so the total cost per kg of chlorine gas generated is close to $20 per kilogram. Even when bought in bulk (>1000kg), TCCA costs about $1 per kg, and so does Ca(OCl)₂. But that still is expensive. If only there was a way to convert chloride ions into chlorine ions... Oh wait there is

. But while electrolysis is the preferred industrial method for chlorine generation, it is hard to perform for an amateur on any useful scale. Sodium hypochlorite cells are available on Alibaba for reasonably cheap, but all of them are meant for chlorinating pools, and thus have a very low output concentration (around 0.8%). Concentrating large amounts of it is not an easy task. Moreover, about 4kW/h is required for each kg of chlorine generated. Electricity is not always available (or even if it is, accesses to tens of thousands of watts is not easy to get regardless). And even if one manages to produce enough concentrated sodium hypochlorite, HCL is still required to generate chlorine gas (which at a price of $4 per liter for a 31.45% solution defeats the whole purpose of generating cheap chlorine). I wanted to know, is there any process that uses heat (molten salt electrolysis?) to produce chlorine? Considering that wood contains about 5kW/h of "power" per kilogram, is readily available for free if one lives near a forest, and the efficiency of direct heat transfer from combustion is significantly higher than that of gasoline engines, generators, transformers, and electrolytic cells, it seems very lucrative (if viable). If only it was possible to convert a kilo of wood into a kilo of chlorine...

So, is it?

palico - 19-11-2024 at 12:53

The cheapest and more available source to generate chlorine gas, are the one you mentioned in the beginning: TCCA and hypochlorite.

Another way is the oxidation of HCl with manganese dioxide or potassium permanganate.

Alkoholvergiftung - 19-11-2024 at 13:16

you can use the weldon process to recycle the MnO2 after reaction with Hcl it forms the weldon mudd. MnCl2 +2CaOH heating to 55C and bubling air throught it forms Caliummanganite CaMnO3 it reacts like KMnO4 with HCl no heating only droping it in the acid. This process was used from 1865 to somewhat late 1920s. The CaCl2 is essecial for the process it helps desolfe the manganchloride the more CaCl2 the more % yield less works faster but less yield. Somewhere i have an table how much hours but i think it was less then 12hours for 90%
If you have an Kipp you can make with this methode great amounts of Chlorine and you only need CaOH as for regeneration and HCl for the Chlor generation.And they wrote the Weldon process give 35% Chlorine calculated form HCl the older MnO2 methode only 32% or 30% not sure.

[Edited on 19-11-2024 by Alkoholvergiftung]

bnull - 19-11-2024 at 14:50

The main advantage of TCCA over hypochlorite is that the rate of release of chlorine gas is pretty much constant. Hypochlorite generates too much chlorine in the beginning and the rate decays rapidly; it is basically a series of puffs of gas. Another advantage is that the residue (cyanuric acid) has low solubility in water and is easily filtered off.

Check out Leonid Lerner's Small-Scale Synthesis of Laboratory Reagents with Reaction Modeling and Bretherick's Handbook of Reactive Chemical Hazards. The former has a procedure in chapter 15. The latter is exactly what it says.

The downside of electrolysis is hydrogen: it is inflammable and there's too much of it. I chlorinated naphthalene some ten years ago by electrolysing a solution of hydrochloric acid, with ethanol as solvent for naphthalene. It worked fine, there was a yellow oil (chloronaphthalenes plus addition products due to ethanol) at the bottom, but the hydrogen flowing still bothered me.

Perhaps there is a photocatalyst for the decomposition of HCl that could be regenerated by heating alone. Something that takes up hydrogen and leaves chlorine free, with the regeneration process combining the hydrogen with air to form water and leaving the something ready for another run. I don't remember seeing one like that, unfortunately.

Be careful and don't poison yourself or your neighborhood with chlorine gas. It wasn't fun in WWI and it isn't now.

j_sum1 - 19-11-2024 at 18:02

I admit to being surprised at the question.
Chlorine is already one of the cheapest chemicals to make. And the prices you have quoted for HCl, TCCA and Ca(OCl)2 are already very reasonable. The cost of glassware to do the reaction are greater than your material cost by a significant margin.
And it is not like a significant quantity of Cl2 is usually needed.

A much bigger concern than cost is producing (and neutraising) it safely. If someone is cutting costs to this degree, I wonder how many other corners are being cut.

Texium - 19-11-2024 at 19:31

Regarding your “free wood as fuel” idea, this raises the problem that while the wood may be “free” for you in the short term, you’re not considering the externalities. It may not cost you anything to cut down and burn up a whole forest, but by doing so you’ve had a significant impact on the local environment, and you’ve put a lot of CO2 into the air that contributes to global warming. When you factor in the costs of the consequences of climate change- damage to infrastructure, impacts on ecosystems and food chains, agriculture, and human health- burning “free” fuel suddenly starts to look a lot less appealing. Now compare your tree-guzzling monstrosity to a solar powered facility. Sure, the required solar panels are going to have an upfront cost and there will be some environmental impact from extracting the materials needed to make them, but once it’s built, you’d have virtually no operating cost and break even in no time, essentially turning salt into chlorine using sunlight, without any need to raze a forest.

But regardless of all the above, I agree with J. These are very cheap chemicals. You’re going to have a hard time saving money against readily available commodity chemicals that are produced on an industrial scale. If you think they’re too expensive, just work on a smaller scale.

Precipitates - 19-11-2024 at 20:20

Quote: Originally posted by 4-Stroke

I wanted to know, is there any process that uses heat (molten salt electrolysis?) to produce chlorine? Considering that wood contains about 5kW/h of "power" per kilogram, is readily available for free if one lives near a forest, and the efficiency of direct heat transfer from combustion is significantly higher than that of gasoline engines, generators, transformers, and electrolytic cells, it seems very lucrative (if viable). If only it was possible to convert a kilo of wood into a kilo of chlorine...

So, is it?

You can mix sodium chloride and a metal oxide e.g., iron, strongly heat, and there should be the release of at least some chlorine.

High temperature interactions of metal oxides with NaCl

Edit: Problem with link.

[Edited on 20-11-2024 by Precipitates]

paulll - 19-11-2024 at 21:37

Quote: Originally posted by j_sum1

I admit to being surprised at the question.
Chlorine is already one of the cheapest chemicals to make. And the prices you have quoted for HCl, TCCA and Ca(OCl)2 are already very reasonable.

Exactly. 4-stroke, I'm using the same materials as you, ie muriatic acid and TCCA from crappy tire. I've tried the hypochlorite, but as bnull notes, the TCCA is just so much more civilised that it's more than worth the slight additional outlay.
I'm not exactly wealthy but with the crappy tire feedstock I could constantly churn out as much chlorine as I'm comfortable being responsible for, for fewer $-per-week than I typically spend on chocolate and cheesy snacks.
How cheap could you possibly want it?

Sulaiman - 20-11-2024 at 00:30

As a hobby chemist I don't count the cost of generating chlorine,
as it's not expensive for the quantities that I use.

My priorities are safety and convenience.
(Both HCl and TCCA should be stored in a ventilated space)
Large volumes of chlorine can be controllably produced in not-too-large glassware, which helps at clean-up time.
Dilute sodium thiosulphate solution in a spray bottle helps with clean-up.

My main concern when generating and using chlorine is that I waste a lot,
which requires gas scrubbing or polluting the air

j_sum1 - 20-11-2024 at 00:53

Or from another perspective...
The cost of sulfuric acid to dry chlorine is greater than the reagents to produce it.

4-Stroke - 20-11-2024 at 11:40

Quote: Originally posted by palico

The cheapest and more available source to generate chlorine gas, are the one you mentioned in the beginning: TCCA and hypochlorite.

Another way is the oxidation of HCl with manganese dioxide or potassium permanganate.

I know it's the most available, but I am looking for the cheapest. But yes, it seems like you are right so far. But I wonder why Ca(ClO)₂ and TCCA cost about the same industrially even though one has significantly more available chlorine.
The main problem with oxidizing HCl is the price and the reusability of the MnO₂ (as well as the inefficiency of the conversion).

Quote: Originally posted by Alkoholvergiftung

you can use the weldon process to recycle the MnO2 after reaction with Hcl it forms the weldon mudd. MnCl2 +2CaOH heating to 55C and bubling air throught it forms Caliummanganite CaMnO3 it reacts like KMnO4 with HCl no heating only droping it in the acid. This process was used from 1865 to somewhat late 1920s. The CaCl2 is essecial for the process it helps desolfe the manganchloride the more CaCl2 the more % yield less works faster but less yield. Somewhere i have an table how much hours but i think it was less then 12hours for 90%
If you have an Kipp you can make with this methode great amounts of Chlorine and you only need CaOH as for regeneration and HCl for the Chlor generation.And they wrote the Weldon process give 35% Chlorine calculated form HCl the older MnO2 methode only 32% or 30% not sure.

Thank you! I'll look into this more. Also do you mean that the yield is 35%?

Quote: Originally posted by bnull

The main advantage of TCCA over hypochlorite is that the rate of release of chlorine gas is pretty much constant. Hypochlorite generates too much chlorine in the beginning and the rate decays rapidly; it is basically a series of puffs of gas. Another advantage is that the residue (cyanuric acid) has low solubility in water and is easily filtered off.

Yes that's true, and also for some reason the hypochlorite costs about the same as TCCA industrially while having much less available chlorine. But why is cyanuric acid's low solubility an advantage? Doesn't it make it harder to remove from the flask? Apart from it's use as a reagent itself (e.g. for making cyanide) what's the point of filtering it out?

Quote: Originally posted by bnull

The downside of electrolysis is hydrogen: it is inflammable and there's too much of it. I chlorinated naphthalene some ten years ago by electrolysing a solution of hydrochloric acid, with ethanol as solvent for naphthalene. It worked fine, there was a yellow oil (chloronaphthalenes plus addition products due to ethanol) at the bottom, but the hydrogen flowing still bothered me.

Oh yeah I remember when a couple years ago I had an HHO explosion. But I hope it is possible to mitigate the risk using good ventilation.

Quote: Originally posted by bnull

Perhaps there is a photocatalyst for the decomposition of HCl that could be regenerated by heating alone. Something that takes up hydrogen and leaves chlorine free, with the regeneration process combining the hydrogen with air to form water and leaving the something ready for another run. I don't remember seeing one like that, unfortunately.

Yeah something like that would be perfect form what I need. Considering the price of HCl (or generating it from sulfuric acid) that would make chlorine generation MUCH cheaper. They used to use the Deacon process, but that requires some extreme conditions which would be hard replicate.

Quote: Originally posted by bnull

Be careful and don't poison yourself or your neighborhood with chlorine gas. It wasn't fun in WWI and it isn't now.

Quote: Originally posted by j_sum1

I admit to being surprised at the question.
Chlorine is already one of the cheapest chemicals to make. And the prices you have quoted for HCl, TCCA and Ca(OCl)2 are already very reasonable. The cost of glassware to do the reaction are greater than your material cost by a significant margin.
And it is not like a significant quantity of Cl2 is usually needed.

A much bigger concern than cost is producing (and neutraising) it safely. If someone is cutting costs to this degree, I wonder how many other corners are being cut.

I wouldn't say that it is the cheapest, but yes the price is reasonable. But who doesn't want stuff for cheaper?
Yes, the glassware is more expensive, but I already have it.
For me, the cost usually determines the amount I make

Can't a gas mask can substitute for most safety precautions (assuming that nobody else is near during the experiment)?

Quote: Originally posted by Texium

Regarding your “free wood as fuel” idea, this raises the problem that while the wood may be “free” for you in the short term, you’re not considering the externalities. It may not cost you anything to cut down and burn up a whole forest, but by doing so you’ve had a significant impact on the local environment, and you’ve put a lot of CO2 into the air that contributes to global warming. When you factor in the costs of the consequences of climate change- damage to infrastructure, impacts on ecosystems and food chains, agriculture, and human health- burning “free” fuel suddenly starts to look a lot less appealing. Now compare your tree-guzzling monstrosity to a solar powered facility. Sure, the required solar panels are going to have an upfront cost and there will be some environmental impact from extracting the materials needed to make them, but once it’s built, you’d have virtually no operating cost and break even in no time, essentially turning salt into chlorine using sunlight, without any need to raze a forest.

I absolutely do not support razing forests, and that isn't what I'm proposing. I see no damage in going to the forest once in a while and collecting some wood (no need to even chop down trees, just collect some twigs, dead trees, sticks, or even just take some free firewood that is often available here). Plus, even if I got the money to buy the solar panels, where do I put them? I don't own land (yet). About 100Wh per m² is a reasonable estimate for solar panels during day in the summertime. That means that 100m² of square panels could make ~2.5kg of chlorine per hour (during sunny summer days). The upfront cost for 100m² is quite a lot. You also need the land, permissions, chloroalkali cells... Or just go and get some free wood

Quote: Originally posted by Precipitates

Thank you! Do you by any chance have access to the article, because I can only read the abstract

. Sounds promising it it produces useful amounts of chlorine. How much does it have to be heated?

Quote: Originally posted by paulll

Ah nice to see a fellow Canadian! Which province are you in?
I just usually like to make as much as I can (of everything), so cheaper feedstock = more chlorine. Also, TCCA needs less HCl (and has more available chlorine), so it is really more expensive than calcium hypochlorite?
One more question, I remember that in some of them sell a product which is mostly formaldehyde, but I wasn't able to find it here. Is it available where you are?

Quote: Originally posted by Sulaiman

As a hobby chemist I don't count the cost of generating chlorine,
as it's not expensive for the quantities that I use.

My priorities are safety and convenience.
(Both HCl and TCCA should be stored in a ventilated space)
Large volumes of chlorine can be controllably produced in not-too-large glassware, which helps at clean-up time.
Dilute sodium thiosulphate solution in a spray bottle helps with clean-up.

My main concern when generating and using chlorine is that I waste a lot,
which requires gas scrubbing or polluting the air

I unfortunately don't have the money to not consider the cost of anything I do, so I do consider the cost of chlorine. For me the main priority is price per kilo, but safety is also important (not really convenience). Why do you waste chlorine?

Quote: Originally posted by j_sum1

Or from another perspective...
The cost of sulfuric acid to dry chlorine is greater than the reagents to produce it.

Sulfuric acid isn't the only thing that can be used to dry it (e.g. CaCl₂ works well too), and it can be regenerated as it is just diluted, not used up. Plus, industrially, sulfuric acid is very cheap (about $200 per ton, compared to $1000 for TCCA), so it is a lot cheaper than the chlorine it dries.

Alkoholvergiftung - 20-11-2024 at 13:38

Yes i think counted on HCl.
Reaction :6 HCl + MnO₂CaO = MnCl₂ + CaCl₂ + Cl₂ + 3 H₂O
They wrote the Weldon chlorine is purer than with natural MnO2 and CO2 free.
The Calciummagnite is an black water insoluble substance.The higest yield was 6 parts CaCl2 pressent give 95% if you have only CaCl2 1 part to one part MnCl2 pressent you only reach 50% but in an hour.It is the solvent for the CaO and the MnCl

There are two Weldon process this one with Weldon mud and the
Weldon Pechiney's process : Magnesiumoxychlorid=Magnesiumchloride solution mixed with MgO 1,3 part MgO to 1 MgCl2 .Than dryd at 260C after it was dried brocken heated to 300C yield 50% but i dont think thats something for home use.

[Edited on 20-11-2024 by Alkoholvergiftung]

bnull - 20-11-2024 at 18:56

Quote: Originally posted by 4-Stroke

But why is cyanuric acid's low solubility an advantage? Doesn't it make it harder to remove from the flask? Apart from it's use as a reagent itself (e.g. for making cyanide) what's the point of filtering it out?

You don't have to boil the solution or wait a lifetime until water has gone to discard the stuff. To remove residues from the flask use a solution of an alkaline carbonate or hydroxide.

Quote: Originally posted by 4-Stroke

For me, the cost usually determines the amount I make

The amount should be determined by necessity. It skips the whole hassle of storage, purification if the substance degrades with time, disposal of residues, dealing with accidents. When I need chlorine, I take a chip off the TCCA block and use it. If I were to make chlorine gas and store it, I would need a suitable container and all the precautions that involve safe storage of a toxic gas. The same applies to sulfur chlorides; if you need them, make just enough. You don't cook twenty pounds of pasta at once for the whole month. You cook just enough to eat for a day or two. At least that's my policy.

Precipitates - 20-11-2024 at 20:16

Quote: Originally posted by 4-Stroke

Thank you! Do you by any chance have access to the article, because I can only read the abstract

. Sounds promising it it produces useful amounts of chlorine. How much does it have to be heated?

Attachment: High_Temperature_Interactions_of_Metal_Oxides_with_NaCl.pdf (807kB)
This file has been downloaded 1 times

I've no idea how much chlorine it will produce, but from the equations, it looks somewhat promising:

2 NaCl + 1/2 O₂ <-> Na₂O + Cl₂

Chlorine produced will boil off, shifting the equilibrium to the right.

1100-1200K

So it would be better to turn some of that wood into charcoal, which isn't too difficult, just a bit time consuming.

clearly_not_atara - 20-11-2024 at 21:00

I think you'd have to make an awful lot of chlorine to pay off the equipment you use to generate it in any case, regardless of how it's generated.

I think you could easily regenerate MnO2 by:

MnCl2 (aq) + Na2CO3 (or NaHCO3) >> MnCO3 (s) + 2 NaCl (aq)

MnCO3 + heat + O2 >> MnO2 + CO2

Wiki says the latter reaction gives "a mixture of Mn (II) and Mn (IV) oxides", which is probably still enough to make more chlorine.

paulll - 20-11-2024 at 22:29

Quote: Originally posted by 4-Stroke

Quote: Originally posted by paulll

Brit in AB. I understand the warm-and-feelies of maximum efficiency, but as I hinted and Sulaiman elaborated-upon, the chances that you're going to use the chlorine, let alone the reagents, at anything like 100% efficiency are zero. Even if you wanted to set a more reasonable efficiency goal, chlorine is so cheap to make that it's never going to be worth the ballache compared to giving your attention to whatever you're using the chlorine *for*. OTOH, there is very much such a thing as too much chlorine. Priorities are safety and convenience.
Cig-packet calculation for doing it OTC in Canada, the hypochlorite comes in a bit cheaper, especially with those small bags of the stuff, but even figuring-in the annoyance of breaking up TCCA tablets, not worth it; You can get it running comfortably and be free to monitor what you're *doing* with the chlorine for an extended period - maybe even read a book and take in the same rays as your chlorine lol.
Home Hardware do a, I think it was RV Septic Flush? Towing your own toilet is such a popular pastime that it's hard to keep up, but it was in a "gallon" jug that looks like the Klenk's acetone, clear liquid, high formaldehyde and looked not to have anything in it that would be hard to get rid of. I passed it up as I'd just got some from a lab supplier but it is a thing. Look in Home Building Supply, rather than HH.

Alkoholvergiftung - 20-11-2024 at 23:53

clearly_not_atara this reaction was used before the weldon process but you need to heat the MnCO3 to 200-300c and the powder was pressed into prills but the brills where to birttl and releases to much chlorine at once and the amount of Chlorine was smaller because of the oxide mix. More HCl needed.

Sulaiman - 21-11-2024 at 01:52

Quote: Originally posted by 4-Stroke

...Why do you waste chlorine?...

1) due to impatience and/or inattention combined with sub-optimal equipment configurations,
I usually had unreacted gas escaping when bubbling chlorine
2) to compensate for this I put excess TCCA in the gas generator,
because adding TCCA during operation is undesirable,
so I have to waste some of my potential chlorine source whether it is used or not.
3) if reacting with solids the ratio of lost to used chlorine was massive
(sorry, no data but I think more than 10x wasted compared to used due to my poor procedures)

For most of my experiments I'm not really interested in efficiency,
my main concerns are
A) can I do it: cost/safety etc., B) can I test and purify it, C) how do I dispose of my waste.
.............................
I'm having difficulty understanding your requirements because you mention budget constraints, and large scale production of chlorine and ( in another thread) ethylene.
Maybe you could explain your actual requirements?