Improved Biodiesel Production from Soybean Oil Using Molybdenum-Zirconium Doped Aluminosilicates as Heterogeneous Catalysts

The efficient conversion of low-grade acidic oils to biodiesel is still a great challenge due primarily to the presented free fatty acids (FFAs) and moisture that significantly activate the used catalysts. In this premise, the acidic aluminosilicates (AAS) were employed as catalyst supports for loading of molybdenum and zirconium metals to synthesize the solid acid catalysts of molybdenum and zirconium doped aluminosilicates (ZrMo-AAS). The so-synthesized composite catalysts were characterized by various physicochemical techniques, and their catalytic activities were evaluated for the efficient biodiesel production by using acidic soybean oils as feedstocks. Results revealed that the targeted solid catalysts featured dual Bronsted-Lewis acidic sites and mesoporous structure with the acidity of 719 μmol/g and surface area of 459.7 m2/g, displaying high catalytic performances for the concurrent transesterification of triglycerides and esterification of FFAs with 92.3% of oil conversion and full FFA conversion to biodiesel at a reaction temperature of 130 °C for 12 h with a methanol/oil molar ratio of 30. This solid catalyst had good water and FFA-resistance capacity even with water content to 1% and FFA content of 40%, and moreover could be easily recovered by filtration with a steady reusability with a slight attenuation in the activity after five time reuses, rendering it to have the potential of cost-effective production of biodiesel from the low-grade oils.