Mesoporous solid acid catalysts esterifying waste cooking oil to biodiesel at room temperature

Abstract

This work presented the preparation and characterization of mesoporous AlPO4 and AlSiO4 by the sol-gel method with the help of isopropylamine as a template. Isopropylamine is a microporous template and it creates only 0–2 nm pores but in the present study, the same template creates mesoporosity in AlPO4 and AlSiO4. The synthesized material properties are characterized by XRD, IR, TGA, BET, TPD, SEM-EDX and HR-TEM. The results confirmed that the synthesized materials are crystalline, tetrahedral framework, thermal stability (800 °C), mesoporosity of AlPO4 (9 nm) and AlSiO4 (7 nm), the acidity of AlPO4 is 0.53 mmol/g and AlSiO4 is 1.16 mmol/g and it exhibits crystalline morphology. Catalytic activities are verified by biodiesel synthesis from waste cooking oil (WCO) as a low-cost feedstock by transesterification reaction. It was identified that the maximum selectivity of biodiesel over AlPO4 and AlSiO4 (89 and 96%) was achieved at room temperature. These catalysts are active at room temperature may be due to their porous nature. The results revealed that AlSiO4 is a more effective catalyst to synthesize biodiesel than AlPO4. These catalysts are environmentally friendly and reusable with the same efficiency.