Quick summary of what I understand from this paper
http://pubs.rsc.org/en/Content/ArticleLanding/2011/GC/c1gc15049aA few quotes
How can we accelerate the formation of FAME in the reaction
between the immiscible oil and methanol? One approach is to
accelerate the reaction by heating and another is to accelerate
it by increasing the contact interface by forming small reactant
droplets through vigorous stirring by ultrasonic irradiation.
Heat and agitation the norm for processing now.
the reaction can still only take place at the interface
between the immiscible reactants present in the heterogeneous
phases. If the FAME formation takes place in a homogeneous
phase, the reaction can be accelerated by a molecular-molecular
reaction.
In english!
immiscible = doesnt mix
heterogeneous = Diverse in character or content
homogeneous = Of the same kind; alike
So the reaction only takes place where the surfaces touch and since the reactants are different they do not mix well, a bit like globules
of oil in water. By making them mix well ie adding acetone which dissolves into the oil and FAME, the mixture allows the oil globules to
break down to a molecular level. This means there is much more surface area for the reaction to occur. ie: faster So heat and agitation is
not as important, hence lower reaction temp required.
we have concluded that the retardation of FAME formation after the
formation of GL can be explained as follows: in the case without
solvent, or with acetone or THF, GL cannot be dissolved in the
oil or FAME, but methanol and KOH catalyst dissolve well in
GL. Therefore, FAME formation is retarded after the formation
of GL due to the dissolution of the important reactant methanol
and the catalyst into the GL phase, which easily precipitates
and is excluded from the reactant solution.
So reaction slows as the methanol and KOH catalyst is taken out of the FAME in the GL(Glycerol)
Acetone does not dissolve in GL so the Acetone stays in the FAME as the GL is formed.
With acetone, which does not dissolve GL, the
separation of FAME from GL was very fast because of the
lower viscosity of the FAME-acetone solution and the large
difference between the low-density FAME-acetone solution and
GL.
Acetone rich FAME has a lower viscocity so the GL drops quicker
Therefore, in the presence of
acetone, the difference in specific gravity between FAME in
acetone (0.8395) and GL with one mole of excess methanol
(1.111) is 0.2715. Due to the large difference in specific gravity
and small viscosities of the two components, GL was rapidly
separated from the FAME solution and precipitated within
30 min.
So thats my take on it had to get it off my chest!
Opinions?
