Solid-base catalysts for biodiesel production by using silica in agricultural wastes and lithium carbonate

•The catalyst, RLi4SiO4 was prepared from rice husk ash silica.•RLi4SiO4 is also successfully tested in the transesterification reaction.•Conversion efficiency of soybean oils to biodiesel using RLi4SiO4 can reach 98.8%.

We investigated the use of Li2CO3 and rice husks (RHs) as Li4SiO4 solid-base catalysts for biodiesel production. Li4SiO4 catalysts were prepared using a simple solid-state reaction, mixing, and grinding rice husk ash (RHA) with Li2CO3 calcined at 800 °C in air for 4 h. The prepared solid-base catalysts were characterized using X-ray powder diffraction, thermogravimetric analysis, and field-emission scanning electron microscopy (FE-SEM) to obtain their physical and chemical properties. The effects of reaction variables, such as catalyst loading, the molar ratio of methanol to oil, and reaction time (conventional heating), were studied. Under the optimal reaction conditions of an methanol/oil molar ratio of 12:1, a 1 wt% catalyst amount, and a reaction temperature of 65 °C for 3 h, this approach achieved a 98.8% biodiesel conversion rate.

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