A Continuous-flow Reactive Distillation Reactor for Biodiesel Preparation from Seed Oils

In biodiesel preparation from vegetable oils and alcohol through transesterification process in the presence of a catalyst, excess alcohol, typically 100% more than the theoretical molar requirement, is used in existing batch and continuous-flow processes in order to drive the reversible transesterification reaction to a high enough conversion rate. The excess alcohol needs to be recovered in a separate process which involves additional operating and energy costs. In this study, a novel reactor system using reactive distillation (RD) technique was developed and studied for biodiesel preparation from yellow mustard seed oil. The main objective was to dramatically reduce the use of excess alcohol in the feeding steam, which reduces the cost in downstream alcohol recover processes, and meanwhile maintain a high alcohol-to-oil molar ratio inside of the RD reactor, which ensures the completion of the transesterification of seed oil to biodiesel. A lab scale sieve-tray RD reactor system was developed and used in this study. Process parameters were studied on the effect of reduced alcohol to oil ratio on the overall quality of biodiesel product and the efficiency of such an RD reactor. Product parameters such as methyl ester content, viscosity, total glycerol, and methanol content were analyzed as per ASTM methods. Preliminary results showed that process parameters of methanol-to-oil ratio of 4:1 (molar) and a column temperature of 65°C produced a biodiesel that met the ASTM standards for total glycerol and viscosity.