Transesterification of rapeseed oil with methanol using CaO and active carbon powders encapsulated microcapsule under the light irradiation

• CaO-active carbon-loaded microcapsule exhibited high FAME yield at 308 K.
• Active carbon powder acted as a light absorber and the heat supplier.
• Light-driven transesterification with catalyst-loaded microcapsule was proposed.
• The dissolution of Ca species into FAME phase was significantly suppressed.

Transesterification of rapeseed oil with methanol to fatty acid methyl ester (FAME) was conducted using microcapsules loaded with CaO catalyst and active carbon powder under the light irradiation. About 80% of FAME yield was obtained after 6 h of reaction with keeping the temperature of reactant mixture (rapeseed oil, methanol, and tetrahydrofuran (THF)) at 308 K. This is probably because encapsulated active carbon powder in the microcapsule absorbed the near-infrared and visible ranges of irradiated light, and then transferred the heat inside the microcapsule which leads to higher temperature of inside microcapsule than that of reaction media/bulk. The results of ICP analyses for both FAME and glycerol phases showed that the amount of leached Ca species was significantly reduced due to lower reaction temperature and microcapsule usage. XRD patterns of tested catalysts indicated that the formation of calcium diglyceroxide phase during the transesterification was remarkably retarded for the case of CaO-active carbon-loaded microcapsule in contrast to a conventional process with CaO powder. This light-driven transesterification of rapeseed oil with methanol using catalyst-loaded microcapsule is promising system owing to high FAME yield and low amount of Ca species leaching into FAME phase.

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