Biodiesel Production Using Static Mixers

Static mixers, devices used for mixing immiscible liquids in a compact configuration, were found to be effective in carrying out initial transesterification reactions of canola oil and methanol. The objective of this study was to explore the possibilities of using static mixers as a continuous-flow reactor for biodiesel production. Biodiesel (canola methyl ester) was produced under varying conditions using a closed-loop static mixer system. Sodium methoxide was used as the catalyst. Process parameters of flow rate or mixing intensity, catalyst concentration, reaction temperature, and reaction time were studied. A full-factorial experimental design was employed, and samples were analyzed for unreacted glycerides as an indicator for biodiesel quality control. It was found that static mixers can be used for biodiesel production. In fact, given enough residence time, appropriate temperature, and high mixing rate, a reactor could consist solely of static mixers and pumps in a continuous-flow design. Temperature and catalyst concentration had the most influence on the transesterification reaction. The data clearly indicates separate inverse linear relationships between temperature and catalyst concentration verses total glycerin. The ASTM D6584 specification for total glycerin (0.24% wt, max.) was met at three of the four temperatures tested, utilizing two of the four catalyst concentrations. The most favorable conditions for completeness of reaction were at 60°C and 1.5% catalyst for 30 min.