Biolubricant production from Indian mustard seed oil through ethyl biodiesel-2G precursor using K2CO3 as heterogeneous catalyst

Abstract

Biolubricants are sustainable alternatives to mineral lubricants and offer environmental, economic and social benefits, including the possibility of producing bioproducts on-farm. Previous research showed that Indian mustard seed oil (IMSO) could be converted into biolubricants by double transesterification using potassium hydroxide as a homogeneous catalyst. The objective of this work was to study the effectiveness of the heterogeneous catalyst potassium bicarbonate (K₂CO₃) for the conversion of IMSO into biolubricant using an ethyl biodiesel precursor in a double transesterification-based process. The first transesterification reaction aimed to convert IMSO into ethyl biodiesel (IMSOEEs) by conducting the ethanolysis under various operating conditions to optimize the process. The optimal operating conditions obtained were: 78 °C, 1.01 bar, 4 wt% K₂CO₃, ethanol to oil molar ratio of 8, and a reaction time of 60 min (with addition of 25 wt% recycled glycerol at 60 min to improve demixing). The second transesterification reaction converted IMSOEEs into biolubricants through reactive distillation with 2-ethylhexanol (2 EH) under the following optimized operating conditions: 100 °C, 0.05 bar, 4 wt% K₂CO₃, 2 EH to IMSOEEs molar ratio of 4, and a reaction time of 120 min. Both ethyl biodiesel and biolubricant were produced with very satisfactory purity (≥96 wt%), thus meeting the expected functional properties.