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From Glycerol to Value-Added Products

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Front. Chem. | doi: 10.3389/fchem.2018.00625

Experimental determination of optimal conditions for reactive coupling of biodiesel production with in situ glycerol carbonate formation in a triglyceride transesterification process

 Luma S. Al-Saadi1,  Valentine C. Eze1* and Adam P. Harvey1
  • 1School of Engineering, Faculty of Science, Agriculture & Engineering, Newcastle University, United Kingdom

This study investigated a reactive coupling to determine the optimal conditions for transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) and glycerol carbonate (GLC) in a one-step process, and at operating conditions which are compatible with current biodiesel industry. The reactive coupling process was studied by transesterification of RSO with various molar ratios of both methanol and dimethyl carbonate (DMC), using triazabicyclodecene (TBD) guanidine catalyst and reaction temperatures of 50 – 80 °C. The optimal reaction conditions obtained, using a Design of Experiments approach, were a 2:1 methanol-to-RSO molar ratio and 3:1 DMC -to-RSO molar ratio at 60 °C. The FAME and GLC conversions at the optimal conditions were 98.0 ± 1.5% and 90.1 ± 2.2% respectively, after 1h reaction time using the TBD guanidine catalyst. Increase in the DMC-to-RSO molar ratio from 3:1 to 6:1 slightly improved the GLC conversion to 94.1 ± 2.8% after 2 h, but this did not enhance the FAME conversion. Methanol substantially improved both FAME and GLC conversions at 1:1 – 2:1 methanol-to-RSO molar ratios and enhanced the GLC separation from the reaction mixture. It was observed that higher methanol molar ratios (> 3:1) enhanced only FAME yields and resulted in lower GLC conversions due to reaction equilibrium limitations. At a 6:1 methanol-to-RSO molar ratio, 98.4% FAME and 73.3% GLC yields were obtained at 3:1 DMC-to-RSO molar ratio and 60 °C. This study demonstrates that formation of low value crude glycerol can be reduced by over 90% compared to conventional biodiesel production, with significant conversion to GLC, a far more valuable product.

Keywords: Reactive coupling, FAME, Glycerol carbonate, Biodiesel, Design of Experiment

Received: 27 Aug 2018; Accepted: 03 Dec 2018.

Edited by:

Mohamed Kheireddine Aroua, Sunway University, Malaysia

Reviewed by:

Matteo Guidotti, Italian National Research Council, Italy
Liandong Zhu, Wuhan University, China  

Copyright: © 2018 Al-Saadi, Eze and Harvey. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Valentine C. Eze, School of Engineering, Faculty of Science, Agriculture & Engineering, Newcastle University, Newcastle upon Tyne, NE1 7RU, United Kingdom, v.eze@newcastle.ac.uk