Sciencemadness Discussion Board

HCl from common fertilizers

BASF - 13-11-2002 at 17:19

(NH4)2SO4>NH3 + NH4HSO4

NH4HSO4 + NaCl>1/2Na2SO4 + HCl
+ 1/2(NH4)2SO4

The hot HCl gas could be cooled and dissolved in water to give the common hydrochloric acid solutions, or dissolved in diethyl ether.

Just for the fun of having the opportunity:

The HCl gas could also be extracted out of a cold solution of sodium chloride and ammoniumhydrogensulfate with diethylether.

HCl is rather as good soluble in Et2O as it is in H2O, high salt conc. and presence of Cl- from NaCl(preferably in excess) will shift the equilibrium to the Et2O, keeping the reaction running to the right.

IodineForLunch - 19-11-2002 at 13:57

I really like this idea, especially since it uses such readily available chemicals.

In the last step, you'll actually get NH4NaSO4 as the byproduct...

David Hansen

BASF - 19-11-2002 at 17:23

1/2Na2SO4 + 1/2(NH4)2SO4 <> NaNH4SO4

Somebody has to write a good manual for the prod of HCl out of fertilizer...once.
I think this would also be an asset to the library.

Marvin - 21-11-2002 at 12:00

Nice idea in theory, but I dont think it would work well. Heat any ammonium compound with a chloride and NH4Cl will sublime. I doubt NH4HSO4 is a very strong acid, so the equilibrium mixture of that and NaCl would not be a very strong acid, resulting in a very small amount of HCl being in the water, or ether layers.

One way to make HCl is to electrolyse hot concentrated NaCl solution, to hydrogen, and chlorine (with a little oxygen), leaving mainly NaOH, collecting the gasses *seperatly*, then placing the outputs very close together, and lighting the jet. As will all electrolysis, in order to get sizable amounts you need a very high current power supply, modified computer PSUs are supposed to work fairly well. To work this properly, you should have a small cell volume and run in NaCl solution, you wont get neer complete decomposition of the salt, but it is cheep. The hot NaOH will attack glass slowly, and aluminium very quickly, bear this in mind when making the cell.

BASF - 22-11-2002 at 09:24

You might have a point there, but the electrolysis of NaCl followed by burning the gases is the best known method anyway, but it is far too complicated and quite dangerous too.
We can only speculate about the yields of the NH4HSO4 method, so somebody just has to try it one time.

If it HAS very bad yields, then converting NH4HSO4 to NaHSO4 could be considered to improve the method(this reaction was originally proposed by rikkitikkitavi for H2SO4-synthesis).


rikkitikkitavi - 24-11-2002 at 14:35

german patent DE 1151 492 describes a method where (NH4)2SO4 is decomposed into NH4HSO4 , and this is further reacted with X2SO4 (X= k, Na) to NH3 and
XHSO4 at about 300 C

The latter bisulfate is decomposed into
X2SO4 and SO3 at about 600C.

After some literature research I have found out that it is much more feasible to use K2SO4 since the reaction
X2SO4 + NH4HSO4 <=> 2 XHSO4 + NH3

forms a equilibrium and this is stronger shifted to the right with X= K than Na.

According to Gmeling the eqilibrium konstant is 36 @ T = 240 and 2690 @ T= 370 C.

The patent describes a mthod where the heating is done by injecting superheated steam into the molten salt mixture, since this removes any formed NH3 to further shift the equlibrium.


BASF - 25-11-2002 at 10:20

I am quite aware of teh fact, that Na2SO4 would be really really cheap, as it can be produced at very low costs from CaSO4*2H2O-soil and NaCl.
But for us backyard chemists(hope not to offend anyone:)), it would perhaps be simplyer to make XHSO4 from K2CO3(pot ash) and NH4HSO4.
(NH4)2CO3 decomposes at 50°C, if i remember right, so the process would be simplyfied a lot.


BASF - 25-11-2002 at 10:24

Oops. I meant K2CO3 to produce K2SO4 and not NaCl.