Optimization of ethanol-based reactive extraction process for spent coffee grounds biodiesel production using duo-function diazabicycloundecene as catalyst and solvent

Abstract

The intention of this master's thesis was conducted to evaluate the potential of using 1,8-Diazabicyclo [5.4.0] undec-7-ene (DBU) as an eco-friendly solvent and catalyst in the in-situ transesterification (in-situ TE) process for producing fatty acid ethyl ester (FAEE) from spent coffee grounds (SCGs) waste. Several parameters were also optimized the FAEE yield in this process by response surface methodology, including temperature, time, ethanol and DBU loading and water content in ethanol. Results showed that promising FAEE yield could achieved under 40 °C. Moreover, FAEE yield tended to decrease under high temperatures due to DBU and ethanol evaporation at 70 °C. The optimal conditions for 5 g SCGs biodiesel production were recorded at 40 °C, 30 minutes, 0.8 ethanol-DBU ratios (total 120 mL), and no moisture, which the FAEE yield was approximately 100%. The presence of water content significantly reduced the yield. However, declining the operating temperature could partly mitigate the detrimental effects of moisture content on FAEE yield. Under low temperature and high ethanol-DBU loading, the FAEE yield was achieved above 80% when the water content in ethanol was 2.5%. The post-ethanol-DBU solution was continued to reuse for the subsequent batch to reduce extra chemical usage. However, the FAEE yield was dramatically lowered to roughly 60% due to the loss of DBU on extracted SCGs from previous batch.