In order to sustainably produce fuels and materials from renewable feedstocks, 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. Specific to this work, CO2 is shown to improve heterogeneously catalyzed biodiesel production via advantages in terms of kinetics, mass transport, and selectivity. A mixed CO2 and methanol system was used for transesterification of triglycerides into fatty acid methyl esters (FAME, biodiesel). Results indicate that high yields are achieved in a three phase system (not including the solid catalyst as a separate phase) where the reaction mainly occurs in the methanol rich phase expanded with CO2. A fundamental approach was taken to understand the effect of substrate-substrate and substrate-catalyst interactions for reaction yields. The success of this CO2-expanded liquid is likely attributed to improved interactions between triolein and methanol as well as catalyst swelling by CO2. Further work on system kinetics show that differences in substrate as well as catalyst active site availability can influence product fractionation. Optimization of catalyst utilization as well as differential reaction kinetics between system species can enhance system selectivity potentially producing a more effective and efficient process. While pitfalls 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.

Carbon dioxide solvent applications for biodiesel production with a heterogeneous catalyst

250th National Meeting (2015)

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