Biodiesel purification in one single stage using silica as adsorbent

Abstract

In this paper a simple biodiesel purification method consisting of one single stage treatment with silica as adsorbent is described. The presented method seems a solution for biodiesel refining saving water, money and process time. The treatment is made under conditions of vacuum (0.2 bar) and mild temperature (65–90 °C). The method allows for the removal of the excess of methanol and water (present in the crude biodiesel and adsorbed on the adsorbent material) simultaneously with the adsorption of the impurities. Silica Trisyl 3000 retains 23% of its weight when the process is conducted at atmospheric pressure and nearly 235% when performed under vacuum conditions. This greatly improves the utilization of the adsorbent and reduces the cost of the process. Under these conditions, the silica behaves as a non-selective adsorbent of high capacity that is able to adsorb different types of impurities, which makes it an excellent adsorbent to purify biodiesel. On the other hand, the adsorption phenomenon is not limited to the formation of a theoretical “monolayer” of adsorbed impurities; it is more complex and includes the formation of multiple layers.