The Role of Carbon Dioxide As a Solvent for Greener Biodiesel Production over a Heterogeneous Catalyst

Within the field of alternative energies, fuels produced from biological feedstocks have great potential to replace petroleum-based products. In order to sustainably produce fuels and materials, biorefineries must be designed for and operated with sustainable processes.  Compressed carbon dioxide – subcritical, supercritical, and CO₂ expanded liquids – can potentially be used in a biorefinery as a green solvent.  Key processes that may be improved via the use of CO₂ are extraction (including fractionation and refinement) and reaction.  In this presentation, supercritical CO₂ (scCO₂) is shown to be an effective solvent for the selective conversion of lipids into biodiesel in combination with a heterogeneous catalyst. Successful transesterification of triglycerides into fatty acid methyl esters is demonstrated via a CO₂-expanded liquid phase.  The role of CO₂ in reaction moderation is explored via kinetics with potential implications for selectivity and system optimization.  While pitfalls do exist for the application of compressed CO₂ in commercial production, this versatile compound holds great promise for utilization as a green solvent in a biorefinery setting.