Author Topic: Getting Methanol OUT of an extracted product  (Read 97 times)

salat

  • Dominant Queen
  • ****
  • Posts: 276
Getting Methanol OUT of an extracted product
« on: May 23, 2010, 01:50:38 PM »
I used Methanol to do an herbal extraction, usually I use ethanol.  Normally I have a setup where I run the extract in a flask with mild heat.  I use a gas takeoff adapter on my flask and run a tube to a condenser that has an erlenmeyer on the bottom in a cold bath attached to a vacuum.   The erlenmeyer acts as a cold trap as well as collecting vessel for recovering the alcohol.  This works ok on the methanol, except that I need to be 100% sure I've got as much of the methanol as humanly possible out of my extract since I'm going to be taking it and don't think methanol is particulary good for your health.

Most of the stuff I see on the web is concerned with removing methanol for HPLC or other analysis and uses even more toxic chemicals in the separation.

salat
Salat

java

  • Global Moderator
  • Foundress Queen
  • *****
  • Posts: 783
Re: Getting Methanol OUT of an extracted product
« Reply #1 on: May 23, 2010, 02:08:15 PM »
Use the physical properties of methanol .....

Properties
Molecular formula    CH4O
Molar mass    32.04 g mol?1
Appearance    colorless liquid
Density    0.7918 g/cm3
Melting point    

?97 °C, ?142.9 °F (176 K)
Boiling point    

64.7 °C, 148.4 °F (337.8 K)
Solubility in water    miscible
Acidity (pKa)    ~ 15.5
Viscosity    0.59 mPa·s at 20 °C
Dipole moment    1.69 D (gas)


...........hence heating in a water bath your extract to 70?C will mostly evaporate all of the methanol off your extracted oil without heating it too much for the sake of your oil......java
¡Prefiero morir de pie que vivir siempre arrodillado!.Emiliano ZapataIt is better to die on your feet than to live on your knees!.......

lugh

  • Global Moderator
  • Foundress Queen
  • *****
  • Posts: 876
Re: Getting Methanol OUT of an extracted product
« Reply #2 on: May 23, 2010, 04:44:31 PM »
If you heat it with a water bath and keep it under a vacuum for long enough there will be no methanol left  ;) It takes many hours and even longer sometimes to completely remove a solvent using vacuum evaporation, it depends on many factors that aren't the same due to differing circumstances  :-X There are tests for alcohols that can be used as well, some of which are described in the attached file:
Chemistry is our Covalent Bond

salat

  • Dominant Queen
  • ****
  • Posts: 276
Re: Getting Methanol OUT of an extracted product
« Reply #3 on: May 23, 2010, 04:59:58 PM »
Thanks.  I can't evap too long because I wind up with goop in the bottom of the flask.  Also doesn't methanol form an azeotrope with water - I heard it wasn't as tight as ethanol's but that it could still do that.

The tests will be invaluable.  I can heat it higher sometimes, depends on the herb/oil involved. 

salat
Salat

java

  • Global Moderator
  • Foundress Queen
  • *****
  • Posts: 783
Re: Getting Methanol OUT of an extracted product
« Reply #4 on: May 23, 2010, 05:35:10 PM »
http://en.wikipedia.org/wiki/Azeotrope_(data)

   CRC only    Lange's only    other (see references)
Azeotropes of water, BP=100°C
2nd Component    BP of
comp.    BP of
mixture     % by
weight    spef.
grav
with various alcohols
ethanol    78.4°C    78.1°C    95.5    0.804
methanol[3]    64.7°C    No azeotrope
n-propanol    97.2°C    87.7°C    71.7    0.866
iso-propanol    82.5°C    80.4°C    87.9    0.818
n-butanol    117.8°C    92.4°C    55.5
U 79.9
L 7.7    
U 0.849
L 0.990
sec-butanol    99.5°C    88.5°C    67.9    0.863
iso-butanol    108.0°C    90.0°C    70.0
U 85.0
L 8.7    
U 0.839
L 0.988
tert-butanol    82.8°C    79.9°C    88.3    
allyl alcohol    97.0°C    88.2°C    72.9    0.905
benzyl alcohol    205.2°C    99.9    9    
furfuryl alcohol    169.4°C    98.5    20    
cyclohexanol[4]    161.1°C    97.8°C    20    
benzyl alcohol[4]    205.4°C    99.9°C    9    
with various organic acids
formic acid    100.8°C    107.3°C    77.5    
acetic acid ‡[3][5]    118.1°C    No azeotrope
propionic acid    141.1°C    99.98°C    17.7    1.016
butyric acid    163.5°C    99.94    18.4    1.007
iso-butyric acid    154.5°C    99.3°C    21    
with mineral acids
nitric acid    86.0°C    120.5°C    68    1.405
perchloric acid    110.0°C    203°C    71.6    
hydrofluoric acid    19.9°C    120°C    37    
hydrochloric acid    –84°C    110°C    20.24    1.102
hydrobromic acid    –73°C    126°C    47.5    1.481
hydroiodic acid    –34°C    127°C    57
sulfuric acid    290°C    338°C    98    
with various alkyl halides
ethylene chloride    83.7°C    72°C    91.8    
propylene chloride    96.8°C    78°C    89.4    
chloroform    61.2°C    53.3°C    97.0
U 0.8
L 99.8    
U 1.004
L 1.491
carbon tetrachloride    76.8°C    66.8°C    95.9
U 0.03
L 99.97    
U 1.000
L 1.597
methylene chloride    40.0°C    38.8°C    99.6
U 2.0
99.9    
U 1.009
L 1.328
with various esters
ethyl acetate    77.1°C    70.4°C    91.9
U 96.7
L 8.7    
U 0.907
L 0.999
methyl acetate    57.0°C    56.1°C    95.0    0.940
n-propyl acetate[4]    101.6°C    82.4°C    86    
ethyl nitrate    87.7°C    74.4°C    78    
with various other solvents
acetone ‡[3][5]    56.5°C    No azeotrope
methyl ethyl ketone    79.6°C    73.5°C    89    0.834
pyridine    115.5°C    92.6    57    1.010
benzene    80.2°C    69.3°C    91.1
U 99.94
L 0.07    
U 0.880
L 0.999
toluene    110.8°C    84.1°C    79.8
U 99.95
L 0.06    
U 0.868
L 1.000
cyclohexane    80.7°C    69.8°C    91.5
U 99.99
L 0.01    
U 0.780
L 1.00
diethyl ether    34.5°C    34.2°C    98.7    0.720
tetrahydrofuran[3]    66°C    65°C    95    
anisole    153.9°C    95.5°C    59.5    
acetonitrile    82.0°C    76.5°C    83.7    0.818
chloral    97.75°C    95.0°C    93.0    
hydrazine[6]    113.5°C    120.3°C    68.5    

¡Prefiero morir de pie que vivir siempre arrodillado!.Emiliano ZapataIt is better to die on your feet than to live on your knees!.......

salat

  • Dominant Queen
  • ****
  • Posts: 276
Re: Getting Methanol OUT of an extracted product
« Reply #5 on: May 24, 2010, 04:44:07 PM »
Thank you for the azeotrope link.  That will help enormously.  It seems that if I just heat my mixture to 64.7 C and leave it there for long enough I should be able to distill all the methanol off.  It doesn't quite jive with my husbands experience - he's been trying to dry methanol and it doesn't seem to work that way (although I could be confusing it with his efforts to dry ethanol - he's had both of them in the pot over the past week so I can't remember which setup was for which alcohol)
We live in a humid area so maybe that may be his problem and not anything I need to worry about.

I don't entirely trust wiki though.  I'll try it out and let you know how it works.

salat
Salat

jon

  • Foundress Queen
  • *****
  • Posts: 1,883
Re: Getting Methanol OUT of an extracted product
« Reply #6 on: May 24, 2010, 06:11:40 PM »
a little methanol never killed anybody puts hair on your chest ;D
personally my alter ego never had a problem with it a little vacum and water bath temps does the job.
if you want let a capillary into the system to sparge it out under vacuo and heat.
« Last Edit: May 24, 2010, 06:13:52 PM by jon »