JJay
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Removing Hydrogen Sulfide from Ethanol
I have contaminated some ethanol with trace amounts of hydrogen sulfide. I consider any amount of hydrogen sulfide impurity undesirable, so I would
like to remove it. Can I simply let it stand over sodium carbonate and then distill off the ethanol, or do I need to use a stronger base?
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Boffis
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Add a few drops of copper sulphate solution and then filter of the copper sulphide and distill. Neutralise the sulphuric acid liberated with soda etc
if you need to add a lot of copper sulphate solution.
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JJay
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Quote: Originally posted by Boffis  | | Add a few drops of copper sulphate solution and then filter of the copper sulphide and distill. Neutralise the sulphuric acid liberated with soda etc
if you need to add a lot of copper sulphate solution. |
Sounds like a good idea - I have plenty of copper sulphate.
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AJKOER
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To quote Wikipedia on H2S (https://en.m.wikipedia.org/wiki/Hydrogen_sulfide ):
"Hydrogen sulfide reacts with alcohols to form thiols, an important class of organosulfur compounds."
Also:
"Thiols show little association by hydrogen bonding, with both water molecules and among themselves. Hence, they have lower boiling points and are
less soluble in water and other polar solvents than alcohols of similar molecular weight. For this reason also, thiols and corresponding thioether
functional group isomers have similar solubility characteristics and boiling points, whereas the same is not true of alcohols and their corresponding
isomeric ethers."
So try heating the ethanol to boil off the smelly thiol.
Another suggestion is add NaOH which dissolves in Ethanol. Then attempt again to boil off any unreacted thiol followed by distilling.
----------------------------------------------------
Also note, CuSO4 is not soluble in Ethanol per Wikipedia.
[Edited on 18-12-2015 by AJKOER]
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BromicAcid
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Shake with elemental silver or copper or zinc. Didn't this just get some coverage?
http://www.thedrinksbusiness.com/2015/12/reductive-wine-can-...
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JJay
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All good ideas.
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AJKOER
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More precisely, I suspect the thiol is reacting with the oxide coating on the transition metal. Or, in the case of a copper penny, Copper(l) oxide,
Cu2O, in particular.
If the alcohol is for consumption and is also rich in oxygen (and especially exposed to sunlight), I would not be too eager to internally consume
after treating with a copper coin. Based on my prior comments on possible Fenton-like reactions (see, for example, my prior comments at https://www.sciencemadness.org/whisper/viewthread.php?tid=64... ), potentially producing some unfriendly compounds as a result of any formed
hydroxyl radical breaking down the ethanol. This would be, interestingly, in sync with Keith Grainger comments on the drink business link above, to
quote:
"Many winemakers use copper as a treatment for reductivity. However it does scalp both aromas and flavours, and the problem should be avoided by
careful winemaking."
where, I suspect, even a limited Fenton-like reaction may impair favor.
[Edit] I would also note that Fenton and Fenton-like reaction mechanisms can enhance galvanic corrosion reactions, and do proceed better in the
presence of a good electrolyte (see http://aem.asm.org/content/69/4/2245.full , where to quote: "The ionic strength dependence can be seen in the results obtained with and without
NaCl (Fig. 1C, E, and F)" ). As support for the galvanic connection, to quote (link: http://onlinelibrary.wiley.com/doi/10.1002/jbm.a.35165/abstr... ):
"Evidence supports a Fenton-like reaction mechanism driving corrosion in which reactive oxygen species are the major driver of corrosion. Using in
vitro tests, large increases in corrosion susceptibility of CoCrMo were seen (40–100 fold) when immersed in phosphate buffered saline solutions
modified with hydrogen peroxide and hydrochloric acid to represent the chemistry under inflammatory cells. This discovery raises significant new
questions about the clinical consequences of such corrosion interactions, the role of patient inflammatory reactions, and the detailed mechanisms at
play. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 211–223, 2015."
I note this because in ocean waters lacking in oxygen but rich in sulfur, a related chemistry involving corrosion of metals appears to occur with
sulfur replacing oxygen. As such, in the presence of sulfur and limited/no oxygen, still possible unwanted products (see, for example, comments on
copper corrosion under anaerobic conditions from H2S generated by bacteria on page 31 at http://nepis.epa.gov/Exe/ZyNET.exe/P1005PMH.txt?ZyActionD=Zy... ). Also, even sulfur-replaced Fenton-like systems? As support, I quote:
"A series of systems using persulfate (PS) or peroxymonosulfate (PMS) instead of H2O2 is designated as a sulfate radical-Fenton system or
sulfur-replaced Fenton system (SR-Fenton). Comparisons and analogies between Fenton (Fenton-like) systems and SR-Fenton systems are made and some new
SR-AOTs systems without PS or PMS are introduced. The possibility for the substitution of HO• by SO4•− for AOTs is discussed."
Link: http://onlinelibrary.wiley.com/doi/10.1002/jctb.4525/abstrac...
[Edited on 19-12-2015 by AJKOER]
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