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[Bali]

Hey guys, im currently doing research on production of Hydrofluoric acid.
So far ive found 4 pathways that lead to HF.
1) From Flourspar :CaF2 (s) + H2SO4 = CaSO4 (s) + 2HF (g) yields >90%
2) From Flousilicic Acid :H2SiF6 + H2O = 6 HF + SiO2 (overall)
3)
From ammonium fluoride :
H2SiF6 + 6NH3 + (n+2) H2O = SiO2.nH2O + 6NH4F NH4HF2 + H2SO4 = (NH4)HSO4 + 2HF
4)From silicon tetrafluoride SiF4 + H2SO4 = HF

Based on the readings ive done, ive only manage to obtain the industrial yield from flourspar.
Do you guys have any idea or reference on the other reactions in detail?tried to search for a week and couldnt find any topics similar here..
Thank you.

[kkala]

In a local fertilizer industry a freon unit was built (~1976), producing HF from fluorite and H2SO4 (from fluorspar, as post No 1 mentions). Process was similar to http://www.adpro-stg.com/technologies/fluorine-technologies/hydrofluoric-acid.html (rotary furnace internally heated through fuel burners). I have not been familiar with that HF unit, or with alternative HF processes, http://en.wikipedia.org/wiki/Hydrofluoric_acid; but the latter ones seem to obtain HF as a byproduct of wet phosphoric acid production ( fluoroapatite treatment by H2SO4).
A classical detailed book on phosphoric acid was A. V. Slack's "Phosphoric acid" (Marcel Dekker, 1968 and probably later) in two volumes. I do not remember whether HF byproduct processes are reported there, most probably in the second volume, but it may be worth while looking into this book in a library.

Edited by kkala, 20 October 2012 - 11:50 AM.