Question

1) What is happening on the molecular level when the biodiesel is being “dried” by sodium

carbonate?

2) Why do vegetable oils need to be converted to fatty acid methyl esters in order to be used for fuel in diesel engines?

3) How specifically does the NMR help determine purity?

4) Glyceryl tristearate is the principle component of olive oil. Why does Sigma-Aldrich sell 1 gram of 97% pure glyceryl tristearate for (the high cost of) $57.30?

Answer 1

1. Any water in biodiesel is absorbed by treatment with sodium carbonate.

2. Vegetable oil contains free fatty acids which act as impurities in fuel. So, free fatty acids need to be converted to methyl esters. This is the easiest and most cost effective way to treat this impurity.

3. NMR shows characteristic peaks for C and H present in the molecule. Any extra peak like for solvent or grease can be detected to be an impurity.

4. It is expensive probably because of difficulty of isolation .