Samples of palm oil containing 40 wt% of a mixture of naturally occurring fatty acids were converted to methyl esters by simultaneous esterification and transesterification using zinc carboxylates as a bifunctional catalytic system.The reaction was optimized using factorial designs with star projections (central composite designs) in which the effects of several process variables were assessed in two levels.In one of these studies, the effects of varying the methanol:fatty acids molar ratio (RMAG) and the actual catalyst concentration (CAT, expressed in relation to the mass of the starting material) was investigated using a response surface methodology.Through this strategy, we found that the optimum reaction conditions were 4 wt% of CAT and a RMAG of 4:1.In addition, the catalytic system in study, although reusable through several reaction cycles, presented significant structural changes during the process, as demonstrated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and thermal analysis (TGA) of the solids recovered after reaction completion.These same tests showed that laurate or stearate anions, initially present in the layered structure of the original solids, were readily exchanged for carboxylate anions that were found in the chemical composition of the raw material and this new layered structure was maintained in all situations in which the experiments were performed.Finally, the glycerin obtained as co-product showed a glycerol content of at least 86 wt%.With this, layered metal (zinc) carboxylates such as those used in this study are envisaged as a viable alternative for the synthesis of biodiesel using low cost feedstocks of high acid number and moisture content.