Process Simulation of Biodiesel Synthesis from Microalgae via a Heterogeneous-Catalyzed Hydrolysis–Esterification Process

Abstract

The hydrolysis–esterification route is an alternative process for biodiesel production from wet microalgae biomass that eliminates the energy-intensive drying and lipid extraction. In this route, lipids are hydrolyzed under subcritical water conditions to produce FFA, then esterified using heterogeneous catalyst. Process simulation was conducted using feedstock of 30,000 kg/h of Chlorella sp. biomass. Tripalmitin was selected as the representative triglyceride of microalgal lipids. The hydrolysis stage produced 60 kmol/h of palmitic acid and 20 kmol/h of glycerol. The esterification stage achieved 82% FFA conversion to FAME under optimum operating conditions of 60–70 °C and a methanol-to-FFA molar ratio of 6:1. Sensitivity analysis showed that increasing the methanol-to-FFA ratio enhanced FFA conversion. It also increased energy consumption in separation process. The duty on distillation column increased from 13.71 MW at methanol-to-FFA ratio of 3:1 to 16.04 MW at a ratio of 6:1. Nevertheless, separation and purification sections successfully produced high quality biodiesel (>99 wt% FAME and <0.25 wt% FFA) while achieving methanol recovery of up to 95%. Overall, the process demonstrates promising technical feasibility and process simplification for biodiesel production from microalgae. However, further improvements are required regarding catalyst stability and operating conditions to support industrial scale implementation.