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Ten Most Common Ways to Screw-Up Making BD.

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August 28, 2016, 11:16 PM
WesleyB
Ten Most Common Ways to Screw-Up Making BD.
I neglected to write that when figuring the average molecular weight of the type of vegetable oil multiply by the per centage in decimal number like 0.01 for 1% multiplied by the molecular weight of that type of free fatty acid present in that type of vegetable oil. The added up multiplication products will be something like 279 grams per mole average molecular weight of the free fatty acids. For palm kernel oil the average molecular weight will be less. With the average molecular weight of the free fatty acids present you can calculate exactly how much methanol would produce a 100% stoichiometric perfect amount of methanol to produce 100% product, on paper, theoretically, except for equilibrium where organic reactions do not proceed 100% like many inorganic reactions do.
August 29, 2016, 01:45 AM
john galt
quote:
So for best results a minimum amount of water will increase biodiesel product percentage and minimize soap production.


Exactly -- and the most important point in the discussion.
Always use fresh dry reagents.
At the very least the UVO should pass the 'hot-pan-test' for water content, and the methanol be fresh and dry. Like methanol, NaOH also absorbs moisture from the air and must be kept sealed and dry. I purchase methanol in 20L 5gal sealed pails and have adjusted the batch recipe to use full pails of methanol/NaOH mix.



August 29, 2016, 09:20 PM
WesleyB
I'll try again. You take the average molecular weight of the free fatty acids present multiplied by three, since there are three fatty acids bonded to each glycerine ion. You subtract 3 from that number then, Then you add to that number the atomic weight of 3 oxygen atoms and five hydrogen atom to get the average molecular weight of the triglyceride molecules present in your type of vegetable oil. Having the average molecular weight of the triglyceride fatty acid esters in your type of vegetable oil, you determine the mass of your oil sample. Then you divide that number in grams by the average molecular weight of the triglycerides of your type of vegetable oil to get the number of moles of the triglycerides. Since each molecule of triglyceride produces three molecules of fatty acids, you multiply the moles of triglycerides by three to get the number of moles of fatty acids present. One mole of free fatty acids requires one mole of methanol to produce one mole of biodiesel, on paper. So for each mole of fatty acid present you figure to add about 32 grams of perfectly dry methanol. 32 Grams of methanol is about one mole of methanol. Carbon is 12 grams per mole, hydrogen is 1 gram per mole, oxygen is about 16 grams per mole. Methanol has one oxygen atom , one carbon atom and four hydrogen atoms. so the molecular weight of methanol is about 32 grams per mole. you figure the number of moles of free fatty acids present then match that number of moles with methanol in an equivalent number of moles. You multiply the number of moles of free fatty acids by the molecular weight of methanol to get the mass of methanol required to on paper theoretically react 100% the number of free fatty acids present. Then you divide the mass of methanol required by the density of methanol in grams per milliliter to get the theoretical minimum of perfectly anhydrous (dry) methanol to produce a 100% reaction of triglycerides into biodiesel. But equilibrium gets in the way. I read somewhere that a 98% reaction producing the fatty acid methyl ester is very good. You add some extra methanol (on the left of the equation) to push the reaction farther to the right in the reaction equation.
August 29, 2016, 11:11 PM
Tilly
Translation

Originally posted by WesleyB:
I'll try again.
You take the average molecular weight of the free fatty acids present multiplied by three, since there are three fatty acids bonded to each glycerine ion.
You subtract 3 from that number then you add to that number the atomic weight of 3 oxygen atoms and five hydrogen atom to get the average molecular weight of the triglyceride molecules present in your type of vegetable oil.

Having the average molecular weight of the triglyceride fatty acid esters in your type of vegetable oil, you determine the mass of your oil sample.
Then you divide that number in grams by the average molecular weight of the triglycerides of your type of vegetable oil to get the number of moles of the triglycerides.
Since each molecule of triglyceride produces three molecules of fatty acids, you multiply the moles of triglycerides by three to get the number of moles of fatty acids present.
One mole of free fatty acids requires one mole of methanol to produce one mole of biodiesel, on paper.

Carbon is 12 grams per mole, hydrogen is 1 gram per mole, oxygen is about 16 grams per mole. Methanol has one oxygen atom , one carbon atom and four hydrogen atoms,so the molecular weight of methanol is about 32 grams per mole.
So for each mole of fatty acid present you figure to add about 32 grams of perfectly dry methanol.

You figure the number of moles of free fatty acids present then match that number of moles with methanol in an equivalent number of moles.
You multiply the number of moles of free fatty acids by the molecular weight of methanol to get the mass of methanol required to on paper theoretically react 100% the number of free fatty acids present.
Then you divide the mass of methanol required by the density of methanol in grams per milliliter to get the theoretical minimum of perfectly anhydrous (dry) methanol to produce a 100% reaction of triglycerides into biodiesel.
But equilibrium gets in the way.

I read somewhere that a 98% reaction producing the fatty acid methyl ester is very good.
You add some extra methanol (on the left of the equation) to push the reaction farther to the right in the reaction equation.