Biodiesel at home - Part 1

The mechanism that I'll be presenting here it's a simple process that anyone can do it by themselves. It is called transesterification and is summed up  as the reaction of  an oil with an alcohol to form esters and glycerol.

Transesterification reaction (Fangrui et al, 1999)

First we will analyse the right side of the chemical equation. Among the alcohols that can be used in the transesterification process are methanol, ethanol, propanol, butanol and amyl alcohol. Methanol and ethanol are used most frequently, especially methanol because of its low-cost and its physical and chemical advantages. We will use methanol in our process. This chemical is toxic so take the necessary protections when handling it. Regarding the oil we can use a diversity of wide commercial oils.

To industry is more interesting to use already used oils, for example food oils. In this case we would be recycling a very prejudicial compound to the environment when it is thrown to the hydric resources. In our case we will use commercial available soya oil.

Now, in the left side of the equation we have two important compounds, esters, that are our biodiesel and glycerol, an important compound largely used in the industry. So we conclude that we have to separate efficiently the two compounds. We will use a basic step of gravitational settling to separate this two products.

The last chemical compound used in this reaction is the catalyst. A catalyst is usually used to improve the reaction rate and yield. Because the reaction is reversible, excess alcohol is used to shift the equilibrium to the products side.We will use NaOH as a catalyst in this reaction. The benefits of using a catalyst are enormous but we encounter a problem that is the water formation. This formation of water can lead to a process called saponification where the esters are attacked by -OH ions in the presence of water. This reaction is undesirable to our process and must be avoided.

Saponification reaction

In the next part of this article we will discuss the production itself. As we saw here it is pretty simple to make biodiesel at home regarding the products that you need to this process.