Comparison of purification methods for biodiesel

In order to meet the very high purity requirements laid down on the European Standard for biodiesel fuel (EN 14214), a significant amount of post transesterification purification is needed. Until recently the preferred method was water washing but considerable interest is now being shown in purification by ion exchange resins and the use of magnesium silicate as a solid adsorbent. The three methods have been tested under several reaction conditions (temperature, concentration, agitation rate, etc.) in order to compare which gives better results. It has been found that it is necessary a previous methanol removal to avoid the saturation of the adsorbents. Glycerol and soap content have been removed in all the processes. Not many differences have been found on the other tested parameters.