(611d) Continuous Transesterification at Near-Critical and Supercritical Ethanol Conditions

Biodiesel is a renewable petroleum diesel replacement produced predominately through the transesterification of triglycerides using an alcohol, most often methanol, with an alkaline catalyst. Since methanol is typically produced from natural gas, the majority of methanol comes from non-renewable sources. One way to make biodiesel truly renewable is to instead use ethanol in place of methanol; however, reaction times with ethanol are greatly increased over those needed for methanol. It is possible to reduce the reaction time to 30 minutes or less by carrying out transesterification at near-critical and supercritical conditions of ethanol. Since no catalyst is used, saponification is suppressed thus increasing tolerance of water and free fatty acids. For this presentation, a constant molar ratio of 41:1 ethanol to canola oil was used. Temperatures ranging from 250°C to 350°C and residence times of between 2 and 20 minutes were examined to optimize the production of ethyl esters and determine yield and selectivity. Reactions were carried out in a continuous, custom made 101 mL Haynes® 282 Alloy tubular flow reactor.