I'm kind of new to the list; I've spent a lot of time in the archives already, and I know this ground has been covered. But any advice/input any of you want to share would be great. Oh, and: I'm an English professor, not a chemist, so my apologies for what must seem like sloppy lab documentation to some of you!
Over the weekend, I tried my first test batch of acid/base stuff; I've had plenty of success making this using both the conventional and base/base reactions (I had quite a lot of success with the latter, actually). Here are the specs:
- de-watered vegetable oil (a mixture, fairly clean & used fairly lightly)
- H2SO4 (95%-98%)
- KOH (purity?)
- Methanol
- I warmed the veg oil to 95F & added--while stirring--80mL of Methanol
- I stirred that (on a little magnet stirrer) until a suspension clearly formed and added 1mL of H2SO4
- After 20 minutes or so I paused the stirring to move the beaker back to the heating pad to warm it again
- Continued stirring for 80 more minutes
- Let the mixture rest for 20 hours
- Dissolved 4.9 g of the KOH (because I'm not sure about its purity) into 120ML of Methanol
- Heated the oil-Methanol-H2SO4 blend to 135F
- Slowly added the methoxide to the blend, while stirring
- Twice, during the hour of stirring, I had to pause to re-heat the oil; in all, stirred for about 75 minutes
- Settlement seemed very slow--it took a couple of hours to settle into distinct layers
- The glycerine layer is only about 110mL
- The biodiesel layer is 800mL
- After 4 hours of settling, I washed the biodiesel violently agitating it with about 600mL of fresh (though hard) water
- Two distinct layers formed, but it took a couple of hours
- 12 hours after the first wash, I drained the wash water & added another 600mL of fresh
- This second wash stage is also separating very slowly--still lots of white settling out.
- Would my pauses during mixing (and the fluctuating temperature) have greatly affected the reaction?
- Could the wash difficulty be the result of too much KOH in the initial reaction?
- Should I have around 80mL of additional precipitate from the reaction--or even more, given the total amount of the bd layer?
Any thoughts on how much KOH/Methanol I should try for that?
Thanks much!
Sean
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