Hydrated lime as an effective heterogeneous catalyst for the transesterification of castor oil and methanol

► Hydrated lime and CaO were evaluated in the transesterification reaction. ► The catalyst's changes were analyzed by X-ray powder diffraction. ► The active phase after the first use was calcium hydroxide. ► Calcium diglyceroxide was identified as the main crystalline phase after the reuses. ► A 98% conversion was achieved within 14 h of reaction at room-temperature.