Sciencemadness Discussion Board

HCl from SiO2/NaCl/water/heat

Aqua_Fortis_100% - 28-2-2009 at 11:41

There is a time (about 1-2 years) that I have look a thread where a person talk about SiO2 reacting with NaCl and water vapour forming HCl and silicate , unfortunately I didnt found that thread.

But searching somewhat I was able to find a patent (attached) confirming such process that may be interesting on future since at least here they are trying to replace good OTC muriatic acid for trash, mix of several acids (H3PO4, HF, sulfamic acid, etc..) and full of various other additives , detergents, etc..
So old methods becoming "new" alternatives...

The patent claims that CaCl2 is more effective in reaction than NaCl, although NaCl is everywhere and generaly much cheaper than CaCl2, so it can be a very good alternative for home manufacturer..

Have anyone attempted such process?
Thanks..

[Edited on 28-2-2009 by Aqua_Fortis_100%]

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Ebao-lu - 2-3-2009 at 13:06

At least, it is possible to calculate the min. tepmerature at which the reaction
H2O + 2NaCl + SiO2 = 2HCl + Na2SiO3
can proceed in theory. Unfortunately i can't find right now the thermodinamical data of these 5 compounds to calculate.

kclo4 - 2-3-2009 at 16:51

I bet it is very high and not worth it.
I think the best alternative to hydrochloric acid would be to go to a garden shop that sells aluminum sulfate to adjust pH in soil. This could be mixed with NaCl, and water and distilled giving you HCl.

Al2(SO4)3 + 6NaCl = 3 Na2SO4 + 2 AlCl3

2 AlCl3 + H2O = Al2O3 + 6 HCl

You could go about making the Aluminum sulfate various ways. boiling a solution originally of NaCl, CuSo4, and Al foil will produce HCl, Na2SO4, Cu, and Al2O3 - I believe.

err I think it is the hydroxide that would form in all of the reactions actually.. well the idea still holds :P

chief - 3-3-2009 at 01:37

The next electric welder with carbon-electrodes will reach any temperature ! If the discharge is immersed under the sand/NaCl-mixture, there is a confinement, so not even any vessels needed. Then just make water/steam be present, and see how it runs !

byko3y - 28-5-2015 at 06:09

For those who encounters this thread and will try to perform the reaction
Al2(SO4)3 + 6NaCl = 3 Na2SO4 + 2 AlCl3
2 AlCl3 + H2O = Al2O3 + 6 HCl
it is not working without some solvent and anhydrous reagents - heating to 400°C does nothing, and at 700°C Al2(SO4)3 starts decomposing into SO2 and Al2O3. You need a water or some other solvent, so the two compounds will be liquified and contact each other. However, I have no idea about yields when using different amounts of water as a solvent-reagent, you might be able to obtain a dillute muriatic acid by adding a lot of water, as well as a nice stream of concentrated 50% HCl by using a minimum amount of water.
I doubt this reaction can give anhydrous AlCl3, with or without water.

And this method barely works
H2O + 2NaCl + SiO2 = 2HCl + Na2SiO3
it gives 1/3 conversion of NaCl after few hours at 900-1000°C

blogfast25 - 28-5-2015 at 07:52

Quote: Originally posted by kclo4  
I bet it is very high and not worth it.
I think the best alternative to hydrochloric acid would be to go to a garden shop that sells aluminum sulfate to adjust pH in soil. This could be mixed with NaCl, and water and distilled giving you HCl.

Al2(SO4)3 + 6NaCl = 3 Na2SO4 + 2 AlCl3

2 AlCl3 + H2O = Al2O3 + 6 HCl

You could go about making the Aluminum sulfate various ways. boiling a solution originally of NaCl, CuSo4, and Al foil will produce HCl, Na2SO4, Cu, and Al2O3 - I believe.

err I think it is the hydroxide that would form in all of the reactions actually.. well the idea still holds :P


Aluminium sulphate can be dehydrated thermally.

Intimately mixing the anhydrous product with an excess of a high boiling anhydrous ionic chloride (like NaCl) and strongly heating may indeed yield AlCl3 vapour, because AlCl3 sublimes easily at about 180 C.

So Al2(SO4)3(s) + 6 NaCl(s) <===> 2 AlCl3(g) + 3 Na2SO4(s) would be pulled to the right by the escaping aluminium chloride. Condense it in a cooler part of the apparatus. Worth trying, IMO...

[Edited on 28-5-2015 by blogfast25]

byko3y - 28-5-2015 at 21:12

My fault, I forgot to mention that my aluminium sulfate was completely dehydrated before the reaction - otherwise I would not be able to heat the mixture to 400°C without hydrolysis of AlCl3 by water. Not more than traces of AlCl were detected.

blogfast25 - 29-5-2015 at 06:16

My simple preparation of AlCl3: Reduction of anh. ZnCl2 with Al powder:

http://www.sciencemadness.org/talk/viewthread.php?tid=30150&...

But it would be a ridiculous way to prepare HCl (by hydrolysing the AlCl3)...

[Edited on 29-5-2015 by blogfast25]