The reaction of vegetable oil triglycerides to produce biodiesel typically occurs when a triglyceride 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 a homogeneous alkali base catalyst. After reaction, the alkali remains dissolved in the by-product glycerin phase or undergoes saponification with available free-fatty acids. The resulting product mixture is then neutralized with an acid and the resulting alkali salt is 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 or leaching of the active catalyst. 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 used high surface area nanocrystalline oxides, primarily MgO and TiO₂, as catalyst supports with minimal pore structure, which reduce the possibility of the large glyceride molecules getting trapped and allow for reusability with higher yield recovery than when using porous supports with similar internal surface area. Attempts to “tether” basic alkali centers on these oxides were performed via the thermal decomposition of supported alkali metal salts and organometallic precursors (such as Li, Na, and K). Catalytic conversions indicate that leaching of the alkali under reaction conditions can be minimized by choosing the proper support and pretreatment conditions. Highly active transesterification catalysts have been produced using Li acetylacetonate that are active for up to seven reaction trials before losing catalytic activity and, most importantly, require no regeneration steps between each reactor charge. The nanocrystalline oxide catalysts present emerging technology to obtain reusable heterogeneous catalysts with high activity for the base-catalyzed transesterification reaction.

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