(332e) Advances in Base-Catalyzed Transesterification of Soybean Oil Using Nanocrystalline Oxides

The reaction of vegetable oil glycerides to produce biodiesel typically occurs when a glyceride present in the oil reacts with an alcohol, usually methanol, to form a mixture of alkyl esters that is termed ?biodiesel.? Current base-catalyzed biodiesel production is performed batch-wise using an alkali salt base catalyst. After reaction, the salt remains dissolved in the by-product glycerin phase, leaving an unreactive phase that must be recovered, neutralized with an acid, and discarded. As an alternative, many basic heterogeneous catalysts have been used successfully to produce biodiesel from various vegetable oils at up to 100% selectivity. However, when regenerated, these catalysts lose a significant portion of its biodiesel yield due to large oil molecules that remain trapped in the catalyst pores. Not being able to recover full catalytic activity limits their integration into current facilities.

In order to enhance the reusability of heterogeneous catalysts for the production of biodiesel from vegetable oils, we have prepared high surface area nanocrystalline oxide catalysts, primarily MgO and Mg-Al binary oxides, as solid base catalysts with minimal pore structure, which reduce the possibility of the large glyceride molecules getting trapped and allow for regeneration with higher yield recovery than for highly porous catalysts. Kinetic studies for nanocrystalline oxide catalysts of identical composition to hydrotalcite-based catalysts are presented to show the effect of composition on activation energy. Additional surface modifications to enhance surface basicity were performed via the thermal decomposition of supported acetylacetonates (Na, Cu, and Fe). The nanocrystalline oxide catalysts present emerging technology to obtain reusable heterogeneous catalysts with high activity for the base-catalyzed transesterification reaction.