Potassium transformation Process
Potassium transformation Process
(OP)
Hello,
I've been doing researches in patent database, Internet site from companies, chemistry books to retrieve information on the fabrication of KHCO3 and K2CO3.
KCl (Sylvite or potash) is found in nature.
TO produce potassium carbonate or bicarbonate, it is possible to use an amine and/or alcool solution +CO2 to directly transform KCL in to its bi/carbonates (Ref : US patent 4,010,243)
Otherwise, what is done in industry (Oxychem, Armand products - Muscle Shoals), is an electrolysis of KCl to obtain KOH ans then do a carbonation of it to obtain K2CO3 or KHCO3.
My question is : can someone explain me why it is impossible to tranforme directly CO2 and KCl to potassium bi/carbonate with only those reactives.
2 KCL + CO2 +H2O --> K2CO3 + 2 HCl
or
KCL + CO2 + H2O --> KHCO3 + HCl
is it a question of activation energy (which would explain why it is done by electrolysis) Any reference or comments would be useful.
I've been doing researches in patent database, Internet site from companies, chemistry books to retrieve information on the fabrication of KHCO3 and K2CO3.
KCl (Sylvite or potash) is found in nature.
TO produce potassium carbonate or bicarbonate, it is possible to use an amine and/or alcool solution +CO2 to directly transform KCL in to its bi/carbonates (Ref : US patent 4,010,243)
Otherwise, what is done in industry (Oxychem, Armand products - Muscle Shoals), is an electrolysis of KCl to obtain KOH ans then do a carbonation of it to obtain K2CO3 or KHCO3.
My question is : can someone explain me why it is impossible to tranforme directly CO2 and KCl to potassium bi/carbonate with only those reactives.
2 KCL + CO2 +H2O --> K2CO3 + 2 HCl
or
KCL + CO2 + H2O --> KHCO3 + HCl
is it a question of activation energy (which would explain why it is done by electrolysis) Any reference or comments would be useful.





RE: Potassium transformation Process
chris
RE: Potassium transformation Process
The electrolysis of KCl to form KOH is done separatly because by-products of this reaction are pure Chlorine (Cl2) and pure Hydrogen(H2) So there is an economical aspect for doing this operation. Then, bi/carbonate products are made from carbonation. This has been known since the beginning of the 20th century.
Since 1980, several production process started using amine (like MEA) to allow direct reaction of KCL with CO2 to produce bi/carbonates. It seams to work well...
What I don't find in me research is : IS it possible do a direct réaction of KCl with CO2 without amine to creat bi/carbonates. I think it is impossible or it has a very poor yield of reaction. That would explain why some work with amine have been done.
I looking for a technical confirmation of this assumption I just made. (I have a small chemistry knowledge)
By non-catalytic, do you mean that you think the reaction KCl-CO2 could happen even if there was no amine acting as a catalitic ingredient?
RE: Potassium transformation Process
NaCl + CO2 + H4NOH ---> NaHC03 + H4NCL
Isn't this similar to the amine reaction ?
Here the solubility of the NaHC03 is much lower so it
precipitates...
<nbucska@pcperipherals.com>
RE: Potassium transformation Process
Event if K is similar to Na (halide), the same formula could be (replace Na by K in your equation):
KCl + NH4HCO3 ---> KHCO3 + NH4Cl
The problem with this reaction is that KHCO3 has higher solubility than NH4HCO3 (unlike NaHCO3 in the Solvay process reaction) . As a result, the solvant (water) gets saturated in NH4HCO3 before you've reached the point where KHCO3 would be suffisent to precipitate! That is why some scientists are working with an amine to increase the solubility so KHCO3 would be the least soluble molecule of the equation and would be easier to precipitate.
RE: Potassium transformation Process
Returning to your question about:
2 KCL + CO2 +H2O --> K2CO3 + 2 HCl
or
KCL + CO2 + H2O --> KHCO3 + HCl
-------------------------------
What would prevent the reaction from
turning around, and forming KCl
with the loss of CO2 ?
I mean, you could maintain this reaction only if you
could remove the HCl to maintain neutrality.
<nbucska@pcperipherals.com>
RE: Potassium transformation Process
2 KCl(s) + CO2(g) +H2O(l) --> K2CO3 (s) + 2 HCl(g)
DGRxn, 298K = -1063.5 + 2 (-95.3) – 2 (-408.5) – (-394.4) – (-237.1)
= + 194.4 kJ/mol
2 KOH(s) + CO2 (g) --> K2CO3 (s) + H2O(l)
DGRxn, 298K = -1063.5 –237.1 – 2 (-378.7) – (-394.4)
= -148.8 kJ/mol
The first reaction is thermodynamically unfavorable. The second is thermodynamically favorable. I have neglected solution effects in order to use standard DGf values, but the RHS and LHS solution effects would somewhat cancel. Data from CRC Handbook of Chemistry and Physics, 79th Edn. (1998).
RE: Potassium transformation Process
Thanks again, I will also check the reference you gave me kenvlach.