Synthesis of the SrO–CaO–Al2O3 trimetallic oxide catalyst for transesterification to produce biodiesel

Calcium oxide is one of the most promising heterogeneous catalysts for biodiesel production . However, an inherent drawback of CaO is the leaching of active species into the reaction solution with the degraded reusability . To strengthen the stability, different supports are composited with the SrO–CaO oxide through the hydrothermal method and mass ratio of SrO to CaO are optimized to get the best outcome of the catalyst. Meanwhile, various characterization methods, including TG , XRD , SEM-EDX, CO 2 -TPD, XPS , ATR-FTIR and ICP-AES, are used to explore the physicochemical properties of catalysts. The 0.4-SrO-CaO-Al 2 O 3 catalyst shows the best catalytic capability in transesterification of palm oil with methanol to produce biodiesel , where the FAME yield of 98.16% is achieved with the molar ratio of methanol to oil of 18:1 and catalyst concentration of 7.5 wt% at 65 °C for 3 h. Besides, ascribed to the greatly reduced leaching out of the active species , this catalyst presents the satisfying reusability and the FAME yield is slightly decreased to 92.61% for the fifth reused cycle. Therefore, this modification method for SrO–CaO–Al 2 O 3 is feasible for enhancing the catalytic stability in transesterification .