When making biodiesel, we're mostly concerned with the biodiesel phase, and the thick black syrup is just this annoying stuff that we have to dispose of somehow.

My method overturns this, however, as it produces a glycerol phase that is so thin that it can be tipped down the sink like water. See the videos in my method.

So I thought I'd post up an explanation of this phase, and the location of the various components in the system.

Let's start at the beginning. The state of a substance (gas, liquid, solid) is determined by the intermolecular forces - that is, the degree and type of interaction between molecules of the same type. For our purposes, the two relevant ones are hydrogen bonding and Van der Waals forces. These are the two weakest types of forces between molecules, with VDW being the weakest. Hydrogen bonding occurs when an organic molecule contains and oxhgen-rich atom such as oxygen, nitrogen or sulfor (but mostly O), with whose electron clouds tha naked hydrogen proton can interact.

Consequently, the first four carbon hydrocarbons are gases - methane, ethane, propane and butane. It's not until you get to C5 - pentane, that we get a liquid at RTP. This is simply because the weak VDW forces are not strong enough to overcome the thermal energy at RTP.

Let's now look at propane. C3H8. Let's now add a single oxygen, so we have C3H8O. This is propanol. This is now a liquid at RTP, simply because the oxygen provides a site at which hydrogen-bonding can occur. Add a further two oxygens and we have glycerol. Now with three oxygens, we get three sites per molecule at which hydrogen bonding can occur, and we now have a thick, viscous liquid.

This stuff is not easy to dispose of. It's so thick that it can clog plumbing if you tip it down the sink or toilet, and in any case the foam can cause problems.

So how is my method different? How is it that it is so thin that it can be tipped down the sink, and doesn't foam?

Let's look at the chemistry of the transesterification process:

1. Methoxide solution:

Eq 1: MeOH + KOH <-> KMeO + H2O

2. Transesterification reaction

Eq 2: C6O6H5R3 + 3KMeO + 3H2O -> C3O3H5K3 (potassium salt of glycerol) + 3(MeOCOR) + 3H2O

3. Regeneration of catalyst

Eq 3: C3O3H5K3 + 3H2O -> C3H8O3 (glycerol) + 3KOH

So the final step in the process results in the regeneration of the catalyst and protonation of the potassium salt of the glycerol to form glycerol.

My method differs in that it removes water from the process, which means that the final state of the glycerol is the potassium salt of the glycerol. Since the hydrogen bonding in glycerol is almost entirely due to the electron-poor hydroxy proton, its absence means that there is less interaction between the molecules. What bonding there is, is almost entirely due to the protons on the carbon backbone, somewhat ameliorated by the fact that the highly electronegative potassium cation will have a substantial electron withdrawing effect on the nonbonding electron pair on the oxygen.

Here is my process:

Methoxide solution:

Eq 1: MeOH + KOH <-> KMeO + H2O

Drying of methoxide solution:

Eq 2: H2O + CaO -> Ca(OH)2

Adding Eq 1 and Eq 2:

Eq 4: MeOH + KOH + CaO -> KMeO + Ca(OH)2

Transesterification reaction:

Eq 5: C6O6H5R3 + 3KMeO + 3H2O -> C3O3H5K3 (potassium salt of glycerol) + 3(MeOCOR) + 3H2O

And this is the final reaction. As the water has been removed, the KOH is not regenerated, and the final state of the glycerol is the potassium salt, which is much thinner than the glycerol and therefore more easily disposed of.

One more issue - what happens to the soap?

When the highly alkaline methoxide is added to the WVO it will obviously first react with the Free Fatty Acids:

KMeO + RCOOH -> RCOOK (soap) + MeOH

In other words, the methoxide reacts with the FFA to form soap + methanol.

So what happens to the soap?

Soap, of course, is a surfactant. It will then, obviously, look for interfaces. In this case, it will be the interface between the hydrophilic glycerol phase and the hydrophobic phase.

So the upper phase will be the biodiesel. Below this will be the soap, and underneath that will be the glycerol phase.

And this certainly aligns with my observations. When I leave the raw material to clarify (by bubbling air), when it has done so (by removing all the excess MeOH) I see a light brown layer settling on top of the dark brown glycerol. And, as I would expect, this light brown material is somewhat gelatinous and clumpy in nature, settling out on top of the liquid glycerol.

So that's it. Happy to answer any genuine questions from any genuine people. As with all my posts, I will ignore all contributions from a certain individual, a bloke who sees himself as an expert on biodiesel but who has no qualifications in chemistry, whose understanding of chemistry could be written on the back of a postage stamp, and whose posts are nothing more than noise.