At the cost of exposing myself as a newbie, which i am, is the acid esterification a complete reaction, meaning is it one step process to conversion of methy esters or is it a "pretreatment" to be able to perform base transesterification by neutalizing most of the FFA's?

pretreatment

Thanks, its kinda confusing as the term pretreatment is used kinda loosely around here or so ive noticed

So after the FFA's are neutralized, what would one do as the commonly accepted next step, titrate for base transesterification and proceed as "usual" or do I need to drain off a layer, remove water before proceeding to base transesterification.

If draining off a layer, what layer as i have heard of a light phase and heavy phase once the esterification is completed.

after acid treatment, if you used the correct amount of methanol, you should be able to drain off the methanol & water mix on the bottom, the wvo will be on top or so ive heard. When i tried it there was a methanol layer on top, and watery wvo on bottom, so what i did was boil off the water from the wvo. either way i think it would be a good idea to heat any remaining water out of the wvo before titrating and then transesterifying.

with all due respect az, what you are recommending is dangerous..boiling out water after an acid stage..there is still methanol in there. methanol boils off before the water, and is not ground a novice wants to tread on until they are familiar with the safety issues.

island, after the acid stage, the titration should be much lower. If its down to an acceptable number for you, the process as normal with the other 40% of the normal amount of methanol, the new titration amount, and the base amount. The only time you need to drain the bottom layer is if your starting titration is over 13 or 14. If you do need to drain, the amount you drain you need to replace with fresh methanol. So if you drain 2 gallons after an acid stage, add 2 more gallons, plus the remaining 40%, plus your lye

hook, since my meth layer was on top, i just drained off the wvo/water which was the bottom phase, and then heated that. im assuming only a small portion of methanol is left in that mix. but you did catch me, i only have experience doing acid esterifications in 1-2 liter batches, the methanol vapors given off are small. if you do bigger batches then yes it becomes a problem if you don't have a recovery system or if you are not in a well ventilated area.

the methanol mix floats when there is too much methanol used. And since it readily mixes with water, there is no way to drain off only the water layer, or only the methanol layer. If you do drain, the remaining oil has methanol in it also.

quote:

Originally posted by islandbiobaron:
. . . is the acid esterification a complete reaction, meaning is it one step process to conversion of methy esters . . . .

The acid esterification reaction is a COMPLETE reaction. The esterification process converts FFA to biodiesel. The esterification process has virtually no effect on the oil (triglycerides) in which the FFA are found.

The acid esterification step must be followed by the transesterification process to convert the TG to Biodiesel.

Ok Thanks alot guys, really clearing it up in my head now.

Now going by what Producer says, i will have a portion of biodiesel from the converted FFAs and some unconverted oil, methanol, acid and water.

now going to what hook and AZ said:

how would you propose i get rid of the water as i hear that tends to make soap when you do the transterification part.

hook, girl mark states in a post that if you use a smaller amount of methanol, like 12% instead of 20% the specific gravity of water will outcompete that of the methanol and the water will drag it down and sink to the bottom...however if you use too much it will float to the top leaving the h20 in the lower phase...im doing an esterification next week and im going to use 12% to see if its true.

island, to get rid of the water in the oil you need to heat it above the boiling pt of h20 100 degrees C, 212 F. But thats where you start getting problems with methanol vapors, unless you are doing it in a system that captures and drains off the methanol.
But like everything im sure there other ways...?

quote:

Originally posted by AZBiodsl:
. . . however if you use too much it will float to the top leaving the h20 in the lower phase . . . .

Water and methanol are miscible. Any portion of water will mix completely with any portion of methanol.

The density/specific gravity of the water/methanol mixture is based on the relative percentages of each in the mixture. If the density of the mixture is greater than the density of the oil, then the mixture will sink and the oil will float above the mixture.

The SG of pure methanol is about 0.79, the SG of pure water is 1.0, and the SG of oil ranges from about 0.88 to 0.92.

If the density of the mixture is less than the density of the oil, then the mixture will float on top of the oil.

In no case will the water separate from the methanol resulting in the situation where the water settles below the oil and the methanol floats above the oil.

Methanol with acid is added to the oil to start the reaction. There is no water at the beginning so the methanol will float. The reaction proceeds and water is produced as a by-product. The water mixes with the methanol. In the early stages of the reaction there is not much water so the water/methanol mixture will float above the oil. Later as the reaction progresses the amount of by-product water produced increases to the point where the density of the water/methanol mixture becomes heavier than the oil.

quote:

Originally posted by producer:
. . . Later as the reaction progresses the amount of by-product water produced increases to the point where the density of the water/methanol mixture becomes heavier than the oil.

My above post can be misleading.

Neither methanol nor water are soluble in the triglycerides (VO). Methanol, and by extension any water mixed in it, is soluble in methyl esters. Methyl esters are soluble in VO.

As the reaction proceeds, the mixture of TG and newly created ME form a solution in which the methanol becomes soluble.

Therefore, it is much more probable to see the methanol/water mixture floating on the top of the oil early in the reaction. It is less probable to see methanol/water mixture sinking below the oil later in the reaction.

Az, it is true
Island, if your titration is below 13,the water produced by the acid esterfication does not impede the reaction, so you dont need to worry about it. That is why its rec that titration over 13 or 14 that you drain. But, remember, if you drain, you are taking out the methanol also. What ever amount you drain, replace with fresh methanol

big 10-4 there AZ.

Trying to be more efficient about it, would it make sense to first heat the mixture till the meth boils off (to be recovered and reused) and then increasing temps until the water boils off (to be eliminated)and then sending sending my coveniently preheated oil/bio (drain biodiesel now???) mix to be completely transesterified?

I would then reuse the recaptured meth in addition to fresh meth mixed in with my KOH (determined by my new titration number) to transesterify the rest of my unconverted oil?

Island, its not neccesary unless your titration is over 13 or 14. Even then, just drain the water methanol mix,and put that in with your glycerol that you plan on demething later. The way you are talking about doing it is a waste of time and energy.

quote:

Originally posted by AZBiodsl:
hook, girl mark states in a post that if you use a smaller amount of methanol, like 12% instead of 20% the specific gravity of water will outcompete that of the methanol and the water will drag it down and sink to the bottom...however if you use too much it will float to the top leaving the h20 in the lower phase...im doing an esterification next week and im going to use 12% to see if its true.

island, to get rid of the water in the oil you need to heat it above the boiling pt of h20 100 degrees C, 212 F. But thats where you start getting problems with methanol vapors, unless you are doing it in a system that captures and drains off the methanol.
But like everything im sure there other ways...?

Az, the reason that your methanol water mix floated was that you used all 20% in the acid stage. 12% for the acid stage, 8-10% for the base stage.

And should i remove the portion on biodiesel(converted from the FFAs) thats in the mix or would i leave that in as well and do a titration on the whole mix??

if you dont have to drain...take a titration while mixed. If you do have to drain, then remix after draining then titrate

quote:

Originally posted by islandbiobaron:
And should i remove the portion on biodiesel(converted from the FFAs) thats in the mix or would i leave that in as well and do a titration on the whole mix??

I do not know of any way to remove the biodiesel from the remaining oil. Titrate the "whole mix".