CONTEXT

The industrial production of biodiesel in Europe, USA and Japan is carried out by chemical processes based on transesterification catalysed by strong bases. Such processes show several problems such as the difficulty to recover the by-product glycerol, the necessity to eliminate the base catalyst from the reaction medium by washing with water, which produces large amounts of alkaline wastes. Over the last years,the enzymatic synthesis of biodiesel by transesterification from vegetable oils has been widely described. However the use of volatile organic solvents as reaction media in enzymatic processes shows also several disadvantages such as the necessity of recovery, as a consequence of the high price and environment impact. Ionic liquids have emerged as green solvents due to their capacity to constitute a clean alternative, non pollutant and reusable as compared to volatile organic solvents

TECHNICAL DESCRIPTION

The invention concerns a process for the production of biodiesel using a recyclable solvent with low environmental impact. The invention relates to the use of a combination of:

-at least one ionic liquid which is lipophilic, solid at room temperature but liquid at the reaction temperature (~60°C) and non miscible with water and,

-at least one enzyme for the implementation of an esterification and/or transesterification process of a substrate consisting of oils , fats , fatty acids or their mixtures with at least one alcohol in a single homogeneous phase at the temperature at which esterification and/or transesterification process is performed.

Very importantly, three phases are formed at the end of esterification and/or transesterification process making them easily separable by a simple decantation:
-a first phase containing the ionic liquid and the enzyme,
-a second phase consisting of glycerol, excess alcohol and water,
-a third phase consisting of fatty acid alkyl esters, i.e., the biodiesel.

The invention enables to process a mixture of mono, di and triacyl glycerides and fatty acids into biodiesel.

BENEFITS

–       Improved reaction kinetic
–       Easy separation of reaction products leading to biodiesel just by decantation
–       No catalyst poisoning and easy recycling of the catalytic mixture
–       After four cycles, 99% yields of biodiesel are still obtained
–       Presence of water and/or free carboxylic acids in the raw oil or fat do not severely impair the process

The reaction mixture is free from inorganic acid and base. That’s advantageous because no aqueous extraction is required to remove the traces of acid or base as it is the case in the traditional synthesis.

INDUSTRIAL APPLICATIONS

This method aims at a green synthesis of biodiesel.