March 29, 2024, 10:33:50 AM
Forum Rules: Read This Before Posting


Topic: THF SEPARATION  (Read 5109 times)

0 Members and 1 Guest are viewing this topic.

Offline ramana143

  • Regular Member
  • ***
  • Posts: 9
  • Mole Snacks: +0/-0
THF SEPARATION
« on: May 06, 2017, 12:06:30 AM »
Hi, i am working as  junior engineer. Here my problem was solvent distillation. my solvents was THF+n-hexane+n-heptane+ water. so any one suggest me the right method to extract the THF from this mixture.

Offline pgk

  • Chemist
  • Full Member
  • *
  • Posts: 892
  • Mole Snacks: +97/-24
Re: THF SEPARATION
« Reply #1 on: May 06, 2017, 05:51:56 AM »
You cannot separate that mixture by distillation, due to a quaternary azeotrope at about 61oC and after water removing, a ternary THF-hexane-heptane at about 63oC.
The only thing that can be done, is removing water by saturation with NaCl, followed by extraction and drying with Na2SO4 or by distilling the trace of water as ternary azeotrope.
Please, take a look at the links below, in order to get an idea.
https://blogs.uoregon.edu/tylerlab/files/2014/10/azeotropic-data-of-binary-mixtures-1ascnny.pdf
https://en.wikipedia.org/wiki/Azeotrope_tables
https://www.researchgate.net/file.PostFileLoader.html?.
https://erowid.org/archive/rhodium/pdf/thfrecovery.pdf
« Last Edit: May 06, 2017, 06:11:06 AM by pgk »

Offline pgk

  • Chemist
  • Full Member
  • *
  • Posts: 892
  • Mole Snacks: +97/-24
Re: THF SEPARATION
« Reply #2 on: May 06, 2017, 07:46:33 AM »
Anyway, THF is miscible with water but not with saturated NaCl solution. Thus, THF, could be removed by several extractions with water. Then, the aqueous phases are saturated with NaCl, followed by removing the THF that separates at the top. The remaining mixture of hexane and heptane can easily be separated by distillation, due to the high difference of their boiling points.
But all above is theoretical and in practice, it does not seem convenient.
PS: Remember that THF mixtures must not be distilled until complete dryness, due to the possible formation of peroxides that are high explosive.

Offline phth

  • Chemist
  • Full Member
  • *
  • Posts: 528
  • Mole Snacks: +39/-4
Re: THF SEPARATION
« Reply #3 on: May 06, 2017, 11:21:31 PM »
Anyway, THF is miscible with water but not with saturated NaCl solution. Thus, THF, could be removed by several extractions with water. Then, the aqueous phases are saturated with NaCl, followed by removing the THF that separates at the top. The remaining mixture of hexane and heptane can easily be separated by distillation, due to the high difference of their boiling points.
But all above is theoretical and in practice, it does not seem convenient.
PS: Remember that THF mixtures must not be distilled until complete dryness, due to the possible formation of peroxides that are high explosive.

+1 for extraction 4x 1/4 the total volume H2O, But I have experienced brine will working in place of water.

Offline pgk

  • Chemist
  • Full Member
  • *
  • Posts: 892
  • Mole Snacks: +97/-24
Re: THF SEPARATION
« Reply #4 on: May 07, 2017, 04:02:58 AM »
Indeed, I have used THF/aq.NaCl for extractions, in the past and it satisfactory worked for substances that were insoluble in diethyl ether. But this case here, is a little bit different because almost everything is soluble in everything and azeotrope with everything.
Anyway, a lab assay in small scale, can clarify the issue.
« Last Edit: May 07, 2017, 04:41:29 AM by pgk »

Offline ramana143

  • Regular Member
  • ***
  • Posts: 9
  • Mole Snacks: +0/-0
Re: THF SEPARATION
« Reply #5 on: May 08, 2017, 02:57:38 AM »
I have already done whatever the above suggested methods were discussed but have not got the required purity of THF. The Gas Chromatography of the input sample is THF(57.75%)+n-hexane(32.05%)+n-heptane(1.78%) remaining is the water content. After the distillation of the input sample the results were THF(83.2%)+n-heptane(6.6%)+n-hexane(1.9%). We used the DMSO as entrainer. Can anyone suggest suitable method for THF recovery with purity(>90%) ?

Offline pgk

  • Chemist
  • Full Member
  • *
  • Posts: 892
  • Mole Snacks: +97/-24
Re: THF SEPARATION
« Reply #6 on: May 08, 2017, 09:18:11 AM »
Unfortunately, what you get is the ternary azeotrope mixture: THF/hexane/heptane, which means that you cannot further separate it, by distillation.
On the other hand, preliminary extraction for such a high THF content, is not convenient at all.
If someone can propose any other purification method for solvents (apart the distillation/extraction), is fully welcome.

Offline phth

  • Chemist
  • Full Member
  • *
  • Posts: 528
  • Mole Snacks: +39/-4
Re: THF SEPARATION
« Reply #7 on: May 08, 2017, 09:02:29 PM »
The extraction is working(!), but enough extractions were not performed which can be seen by % differences in the two phases.

Other solvents that will disrupt the azeotrope could be used empirically.  Was a vigoreux column used?? 

I would try to dilute with another organic solvent such as ethyl acetate (5x original volume), and extract 6x 1/2 volume water.

Sponsored Links