Experimental Optimization of a Continuous-flow Reactive Distillation Reactor for Biodiesel Production

A comprehensive study of biodiesel preparation from canola oil was performed on a continuous-flow reactive distillation (RD) reactor system. Optimization of six process variables was studied experimentally and analyzed statistically on the overall performance of the RD reactor system. These variables include the feed methanol to triglycerides molar ratio, reaction time, reboiler temperature, catalyst concentration, methanol circulation mode, and catalyst formulation. An experimental design was used in the experiments, and statistical multiple response regression models were employed for process optimization. Under the operating conditions explored, product yields ranged from 41.5% to 94.9%, productivity ranged from 16 to 55.8 kmol/m3·h (5.6 to 19.5 m3/m3·h), and soap formation varied from 4.44 to 29.1 mol/100 mol (0.19 to 1.27%wt.). For different optimization criteria, the following optimum variable ranges were found: feed molar ratio from 3.65:1 to 4.50:1, reaction time from 3.76 to 5.56 min, reboiler temperature from 100°C to 130°C, and catalyst concentration from 0.13 to 0.24 mol/mol. Although the process variables individually affected the system performance to a certain extent, the interactive effect of the process variable combinations affected the system efficiency more significantly. When maximized, the product yields and productivity were 98.8% and 55.6 kmol/m3·h (18.5 m3/m3·h), respectively. However, when soap formation was minimized, the yield and productivity were 72% and 9.3 kmol/m3·h (3.1 m3/m3·h), respectively. It is recommended that the optimization of the RD reactor system be based on the maximization of product yield and reactor productivity.