| Pages:
1
2
3 |
Microtek
National Hazard
Posts: 869
Registered: 23-9-2002
Member Is Offline
Mood: No Mood
|
|
@ Nitrojet:
When you do the transesterification of castor oil to obtain methyl- or ethyl ricinoleate, which set of reaction conditions do you follow ? In that pdf
they used both high and low temps, both KOH and NaOMe as catalysts, etc.
When I attempted the reaction, I mixed castor oil and ethanol ( 100 % excess ) with ca. 1 % KOH dissolved.
I then capped the flask and shook it vigorously. It quickly became homogenous ( I had thought this would take quite a while ) so I added a magnetic
stir bar and stirred it for 2 hours at room temp.
I then let it sit overnight, but no phase separation occured. If I add some of it to an equal amount of water, slight agitation causes an emulsion to
form, which isn't the case with fresh castor oil so this is promising, I suppose. However, the product doesn't seem to be very soluble in gasoline.
Does this correspond to your experiences on the subject ?
|
|
|
quicksilver
International Hazard
Posts: 1820
Registered: 7-9-2005
Location: Inches from the keyboard....
Member Is Offline
Mood: ~-=SWINGS=-~
|
|
I am pretty sure needle size / shape could be controled with temp and other specifics within the recrystalization process. And I'm also willing to bet
that the actual moxing results in shaving of the material more than would be expected. but a source for industrial / pure PIB...that, I have not
found. (If anyone knows, please U2U me, or post). - IF the process of re-crystalization is done in reverse using a single ice cude as a seed the
length of the needle becomes much shorter and thicker, making them "fit together" in a denser format.
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
I took 100 ml of methanol and 100 ml castor oil. A very large excess of methanol was used since this makes dissolving the NaOH/KOH easier and prevents
this gelatin mass you describe. Then I warmed the methanol slightly to dissolve all of the catalyst, this is easier with KOH than with NaOH btw since
the first is more soluble in alcohols than the latter. All of the catalyst, KOH or NaOH, should have dissolved in the alcohol before you add the
castor oil! When using ethanol be sure though that it is as waterfree as it can possibly be, since using a large excess of water-containing-ethanol
will result in a very bad yield or even no product at all...
After adding the castor oil, warm to near boiling point of the alcohol to reduce the reaction time to about 3 hours IIRC. (could have been 4 hours
 ) Unfortunately, phase separation will not occur. According to the article this
is mostly determined by the catalyst used. IIRC, using sodium ethoxide does result in phase separation, whereas KOH or NaOH (like I used too) does
not...
Not that it really matters, the oil is the only reactant that would be difficult to seperate from the isopropyl rincinoleate, but the conversion of
the oil should be near 100% (when using absolute alcohol). The rest of the products, like potassium oleates, glycerine and the excess ethanol can all
be removed by washing with water. The end product should be a very runny oil, slightly more viscous than water and completely non-volatile...
|
|
|
nitro-genes
International Hazard
Posts: 1048
Registered: 5-4-2005
Member Is Offline
|
|
I took 100 ml of methanol and 100 ml castor oil. A very large excess of methanol was used since this makes dissolving the NaOH/KOH easier and prevents
this gelatin mass you describe. Then I warmed the methanol slightly to dissolve all of the catalyst, this is easier with KOH than with NaOH btw since
the first is more soluble in alcohols than the latter. All of the catalyst, KOH or NaOH, should have dissolved in the alcohol before you add the
castor oil! When using ethanol be sure though that it is as waterfree as it can possibly be, since using a large excess of water-containing-ethanol
will result in a very bad yield or even no product at all...
After adding the castor oil, warm to near boiling point of the alcohol to reduce the reaction time to about 3 hours IIRC. (could have been 4 hours
) Unfortunately, phase separation will not occur. According to the article this
is mostly determined by the catalyst used. IIRC, using sodium ethoxide does result in phase separation, whereas KOH or NaOH (like I used too) does
not...
Not that it really matters, the oil is the only reactant that would be difficult to seperate from the isopropyl rincinoleate, but the conversion of
the oil should be near 100% (when using absolute alcohol). The rest of the products, like potassium oleates, glycerine and the excess ethanol can all
be removed by washing with water. The end product should be a very runny oil, slightly more viscous than water and completely non-volatile...
|
|
|
Etanol
Hazard to Others
Posts: 188
Registered: 27-2-2012
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by nitro-genes  | After numerous attempts to modify the crystal shape of PETN I have only been able to produce needle like structures. Different solvents, temperatures
and concentrations to alter nucleation/growth ratio were tried, but this simply doesn't seem to help... 
The process described by "US2370437 Nitration Process for PETN" was attempted many times with PETN directly from nitration and recrystallized PETN,
but only yielded needles or almost plate like structures from completely saturated solutions...
|
Hmm. I got the same result. Contrary to Urbansky, PETN crystals settling from ethylacetate do not differ from such acetone. There must be a different
way.
I accidentally received rounded crystals in the size of several micrometers, when I was redrawn with a mixture of PETN and di-PEN. These were waste
from purification of PETN obtained by hot re-eterification in a mixture of acids. Initially, I wanted to throw him away. However, I could not get the
same result with pure PETN and affordable solvents yet.
Maybe you need to increase the viscosity of the solution or add surfactants?
|
|
|
| Pages:
1
2
3 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
