Continuous biofuel production from palm oil in supercritical alcohols

Abstract

The supercritical alcohol (SCA) process is the one of alternatives to produce biofuel because it has several advantages over the conventional homogeneous catalysts in the term of production efficiency and feedstock flexibility. However, the employing high alcohol to oil molar ratio (40:1–42:1) is the main problem of SCA process due to a requirement of a significant energy in preheating and recovering alcohols. The large energy input also produced a significant environmental load. Thus, this work proposes a novel approach to reduce the alcohol to oil molar ratio in biofuel production from lipid–based biomass in SCA. The first objective was to investigate the optimal conditions of biofuel production in a batch reactor. The investigation was successfully done by the response surface methodology (RSM) and found that alcohol to oil molar ratio can reduce to 12:1 at the optimal temperature of 400 ◦C. The second objective was to scale-up the biofuel production with SCA in the continuous reactor. The results showed that the synthesis of biofuel using a lowered alcohol to oil molar ratio of 12:1 at 400 ◦C provided a triglyceride conversion of up to 99% and the maximum ester content in the range of 80–90%. In addition, the side reaction between glycerol and alcohol at 400 °C and 15 MPa showed a positive effect of increasing fuel yield by 2%–15% based on input palm oil weight.