Water scale-derived catalysts were used in transesteri cation reactions carrying out in a batch reactor for the catalytic activity.Soybean oil and methanol were placed in a round-bottom glass ask equipped with a re ux condenser. Next, the designated amount of prepared catalyst was placed in and stirred at 50–80 C for 2–6 h. After the reaction, centrifugation was used to sep-arate the layers (methyl ester, glycerol, and catalyst).Then, the treated sample (0.2 lL) was injected into the GC-122 gas chromatograph, which was equipped with a SE-54 capillary column (0.32 mm 30 m). The column temperature was kept at 160 C for 2 min, raised to 220 C at a rate of 10 C/min, then to 260 C at a rate of 8 C/min, and nally maintained at this temperature for 10 min.