Comparisons of metal oxides activity in the transesterification of triglycerides by С1–С4 alcohols

The activity of heterogeneous catalysts for the transesterification reaction of sunflower oil triglycerides with aliphatic alcohols of normal structure was investigated in this work. Fine-dispersed oxides ZnO, NiO, FeO, CuO and MnO served as catalysts. The following aliphatic alcohols were used in the transesterification process of sunflower oil triglycerides: methanol, ethanol, propan-1-ol and butan-1-ol. The transesterification reaction was performed under the conditions as follows: the content catalyst of 0.25 wt.%, the triglycerides:alcohol molar ratio of 6.5:1 and the temperature of 333 K (methanol) or 348 K (ethanol, propan-1-ol and butan-1-ol). The investigated metal oxides were arranged in series according to their activity towards the transesterification reaction of sunflower oil triglycerides with C1–C3 alcohols. It was established that these series were practically the same for the mentioned alcohols. Similarity between the oil conversion curves of the reaction duration for C1–C3 aliphatic alcohols in the presence of all studied catalysts was shown. The use of the most active catalysts (ZnO and NiO) for the transesterification reaction of triglycerides with C1–C3 aliphatic alcohols allowed achieving the triglycerides conversion of more than 95% at the reaction duration of 2.5 h. Iron and manganese oxides exhibited relatively high catalytic activity in the transesterification reaction with aliphatic C1–C2 alcohols. However, the oil conversion was only 86.7–91.1% for the transesterification reaction by propan-1-ol in the presence of above-mentioned catalysts under the optimal conditions (reaction duration of 2.5 h). Copper oxide exhibited the lowest activity among all catalysts that were tested. The highest initial reaction rate in the presence of metal oxides was achieved in the transesterification of sunflower oil triglycerides by methanol. The reaction rate of triglycerides transesterification by butan-1-ol was by three orders of magnitude lower than that achieved by using of other alcohols.