Microwave-assisted one-step production of biodiesel from waste cooking oil by magnetic bifunctional SrO–ZnO/MOF catalyst

Magnetic bifunctional SrO–ZnO/MOF catalyst supported on metal-organic framework (MOF) was synthesized for one-step biodiesel production from high acid value oils. The catalyst presented both basicity (2.84 mmol/g) and acidity (0.02 mmol/g) due to active components of Sr3Fe2O6 and ZnO. MOF support increased catalyst specific surface by 3.7 times and provided Fe3O4 component for magnetic separation. The highest soybean biodiesel yield of 99.5% was obtained at 80 °C with 3 catalyst cycles. Microwave heating significantly reduced reaction time from 20 min to 5 min at 99.0% biodiesel yield and 80 °C. The catalyst was highly active and resistant to free fatty acids with biodiesel yield of 90.0% from waste cooking oil (AV of 3.3 mg KOH/g) at longer reaction time of 30 min. SrO–ZnO/MOF has potential application in biodiesel industry.