Investigation of the factors affecting the progress of base-catalyzed transesterification of rapeseed oil to biodiesel FAME

Conventional base-catalyzed transesterification method for large scale biodiesel FAME production is affected by anumber experimental factors. This work investigates, quantifies and establishes the effects of catalyst type,number of reaction stages, the free fatty acid (FFA) andwater content of the reactants on the progress of rapeseedbase-catalyzed transesterification under the optimized reaction conditions used in scale-up production. Firstly,the efficacy of different alkaline-base catalysts: sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodiummethoxide (CH3ONa) were investigated and compared. The order of catalyst efficacy was found to beNaOH N CH3ONa N KOH at 1% m/m concentration: NaOH was most potent achieving the highest conversion toFAME in the shortest time. The effect of performing a 2 stage base-catalyzed reaction, where glycerol wasremoved prior to a second reaction stage, was investigated to determine any increase in the overall conversionto FAME relative to the single stage process. The effects of increasing the reactant FFA and water content oncompleteness of transesterification using 1% m/m NaOH were also studied. End-product FAME content was significantlyreduced at N5% m/macid content (acid value N 10 mg KOH/g). Above ~7% m/macid (~14 mg KOH/g),the reaction was stopped due to excessive soap/gel formation. The FAME content was not especially sensitive toreactant water contamination. Only at a water level of N6000 ppm was the FAME content.