This contribution investigates the transesterification of soybean oil with methanol in the presence of demineralized (DM) water plant sedimentation as a heterogeneous catalyst in a microreactor, which has not been studied in previous works. The catalyst systems were characterized by the X-ray diffraction (XRD) method. The effects of catalyst concentration, methanol/oil volume ratio, and residence time on the transesterification efficiency were investigated and the purity of methyl ester was optimized using response surface methodology (RSM). The optimal conditions for the transesterification process were as follows: catalyst concentration of 0.0837 g/g, methanol to oil volume ratio of 1:1.89, and residence time of 10 min during which methyl ester purity was measured at 93.14 %. However, the purity value obtained by experimental model is equal to 87.06 %. Through the analysis of model and experimental data, mean relative error was obtained as 7.17 %. Experimental results indicated that time for the production of methyl ester with high purity (93.14 %) can be shortened significantly in an optimized microreactor compared to conventional stirred reactors (residence time of only 10 min).
