Hydration—Dehydration Technique: From Low Cost Materials to Highly Active Catalysts for Bio-Diesel Production

Abstract

An efficient technique for increasing the trans esterification activity of low cost natural rocks (calcite and dolomite) was proposed in order to make them highly suitable for use as heterogeneous catalysts for biodiesel. This technique involves water treatment of the oxide phase under mild conditions followed by thermal decomposition at an elevated temperature. The transformation of oxide to hydroxide phase and the reverse occurred simultaneously during the hydration–dehydration step with changes in the chemical and textural properties of the sample. The effectiveness of the hydration interaction appears to be due to a change in pore-size distribution, which is created by particle expansion in the formation of the hydroxide structure and the formation of more porosity and surface area during the dehydration and re-crystallization of oxide structure. Trans esterification of palm olein was used to determine the activity of catalysts to show that this technique make catalyst has higher activity than the typical calcinations method. This study provides an understanding regarding how this hydration–dehydration process influences the properties and activity of dolomite.