Role of CO2 in Mass Transfer, Reaction Kinetics, and Interphase Partitioning for the Transesterification of Triolein in an Expanded Methanol System with Heterogeneous Acid Catalyst
2015
Soh, Lindsay | Chen, Chun-Chi | Kwan, Thomas A. | Zimmerman, Julie B.
Fatty acid methyl ester (FAME) production via transesterification of triglycerides (TGs) over a heterogeneous acid catalyst is mediated by carbon dioxide in an expanded methanol system. A representative TG, triolein, is used to determine the mechanisms and interactions responsible for the improved yields over Nafion-NR50 in these system conditions. Namely, the system mass transfer limitations, reaction kinetics, and interphase partitioning behavior are explored by varying mixing conditions and catalyst characteristics over a time series of 4 h. It is found that CO₂ enhances mass transfer leading to improved reaction yields and product profiles due to increased substrate transport to and from the catalyst surface. CO₂ also contributes to catalyst expansion, leading to greater exposure of active sites and faster reaction kinetics. Initial reaction rate constants using methanol-soaked Nafion reflect pseudo-first-order kinetics. Finally, the substrate-reagent mediating properties of CO₂ are discussed in reference to the varying reaction rates of TG and intermediate products. All three of these mechanisms contribute to CO₂’s multifaceted role in facilitating heterogeneously catalyzed reactions.
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