Biodiesel

Biodiesel: "What is still widely unknown is that it is easy to make biodiesel for diesel engines using vegetable oil or animal fat. Biodiesel is sold commercially in Europe, America and Australia.
On a small scale, vegetable oil is relatively expensive, but used products from the cooking industry is abundant and can easily and cheaply be converted into a biodiesel fuel that will mix in any quantity with conventional diesel. During heating, the amount of polymers in the oil may increase up to 15 wt% and thus may have negative influence on fuel characteristics. Therefore, the amount of polymers in waste oil is a good indicator for biodiesel production (Mittelbach M et al. JAOCS 1999, 76, 545).
The transesterification process involves mixing at room temperature methanol (50% excess) with NaOH (100% excess), then mixing vigorously with vegetable oil and letting the glycerol settle (about 15% of the biodiesel mix). The supernatant is biodiesel and contains a mixture of methylated fatty acids and methanol, the catalyst remaining dissolved in the glycerol fraction. Industrially, the esters are sent to the clean-up or purification process which consists of water washing, vacuum drying, and filtration.
An in situ alkaline transesterification was shown to be efficient in preparing fatty acid esters, the simple and direct process eliminating the expense associated with solvent extraction and oil cleanup (Haas MJ et al., JAOCS 2004, 81, 83).
Transesterification may be processed using methanol, ethanol, isopropyl alcohol, or butanol, the catalyst being either sodium or potassium hydroxide. It was shown that the methanol/oil molar ratio influences largely the efficiency of the reaction and has important implications for the optimal size of methyl ester plants (Boocock DGB et al. JAOCS 1998, 75, 1167). Optimization of methanolysis"