Kinetics and mechanism of the KOHcatalyzed methanolysis of rapeseed oil for biodiesel productionThe reaction of rapeseed oil with methanol catalyzed by KOH is described by a model consisting of two sequences of consecutive competitive reactions. The first sequence expresses the methanolysis of rapeseed oil to methyl esters (biodiesel) whereas the second sequence describes the always present side reaction-saponification of glycerides and methyl esters by KOH. The proposed chemical model is described (after rational simplifications) by a system of differential kinetic equations which are solved numerically by two independent computing methods. The thus obtained theoretical kinetic and equilibrium results are compared numerically and/or graphically with the experimental parameters. The latter were obtained by the determination of the relevant components in the actual reaction mixture by analytical methods. According to the experimental results, the proposed reaction scheme is fulfilled with the probability of ca. 78%. The optimal average rate constants and equilibrium constants of individual reaction steps of the discussed scheme are introduced. The limitations of the proposed reaction model are discussed.

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SummaryWithin the biodiesel production process, glycerol arises as a side product. This free glycerol is included also in biodiesel in a small amount. Several methods are known to determine it. Some of them are based on the GC. In this paper a new method is introduced, which is based on the extraction of free glycerol into water and its subsequent determination in water solution by HPLC with refractometric detection. The comparison of GC and HPLC methods led to the same results.The new method is reliable and comparatively fast for determination of free glycerol in biodiesel.