Abstract

Introduction: Petroleum resources are non-renewable energy sources that pose significant envi- ronmental risks. The transesterification of vegetable oil into biolubricants is recognized as a potential alternative to mineral-based lubricants. In this study, a model reaction between methyl hexanoate (representing diesel derived from vegetable oil; MH) with trimethylolpropane (TMP) was investigated using heterogeneous SrO/MgO–CaO catalysts to determine the optimal reaction conditions for the production of biolubricants from diesel.
Method: SrO/MgO–CaO catalysts were synthesized using a co-precipitation method and analyzed using X-ray diffraction. The transesterification of MH and TMP was evaluated in a batch reactor under different reaction conditions. The products were analyzed using gas chromatography (GC)and gas chromatography–mass spectrometry (GC–MS).
Results: The conversion of MH increased with reaction temperature, while the conversion and yield of diesters and triesters were greatest at a catalyst loading of 3 wt.%, a MH:TMP molar ratio of 3:1, and a reaction time of 3 h. SrO/MgO–CaO (NH4OH) and SrO/MgO–CaO (KOH, K2CO3) cata- lysts achieved MH conversions exceeding 76%, while the SrO/MgO–CaO (NH4OH, K2CO3) catalyst exhibited the greatest diester and triester selectivity (>93%).
Conclusions: SrO/MgO–CaO catalysts were successfully synthesized and demonstrated high di- ester and triester yields of 65–68% following the transesterification reaction between MH and TMP. The high yield of the transesterification reaction highlights the strong potential of SrO/MgO-CaO catalysts in transesterification reactions, such as the production of biolubricants from biodiesel.