Question

This is for my biodiesel lab-

This is a biodiesel synthesis... we are using vegetable oil in a trans-esterification reaction.

100%pure vegetable oil + CH3OH --> biodiesel (NaOH) is above the reaction arrow. We stir 2mL of methoxide solution in a beaker for 20 minutes.

The reaction has CH3OH as reactant and NaOH as condition (written on the top of the arrow). This step uses sodium methoxide. WHAT IS THE RELATIONSHIP?

Also, for glycerol and methyl ester (biodiesel)- WHAT PROPERTIES ARE DIFFERENT THAT THEY SEPERATE? WHAT PROPERTIES ARE DIFFERENT THAT GLYCEROL SINKS?

Answer 1

In the transesterification of vegetable oils, with an alcohol in the presence of a strong acid or base, producing a mixture of fatty acids alkyl esters and glycerol

the reaction is :

hIn the given process, triglycerides in vegetable oil reacts with CH3OH and forms esters and glycerol as byproduct.

Methoxide Solution is used as a base-catalyst for the esterification reaction. the methoxide anion attacks the carbonyl carbon to form a tetrahedral intermediate which then decomposes to form the methyl ester. Basic catalysts are less corrosive than acid catalysts (which can be used too).

The reason why methyl ester and glycerine separate and glycerine settles at the bottom of the reaction flask is:

At room temperature,

the density of glycerine is ------  1.261 g/cm³

the density of methyl ester is ----------- 0.88 g/cm³

As u can see, glycerine has a higher density than methyl ester and hence it settles at the bottom of the flask, also the huge density difference causes the two solutions to form 2 distinct layers.