Microwaved assisted biodiesel production from WCO using steel slags as catalyst

Nowadays, the circular economy and the reuse of waste materials are crucial points to reach the ecological conversion. The present work reports on the development of an innovative catalytic system for biodiesel synthesis starting from waste biomass (waste cooking oil, WCO) in the presence of waste material (steel slags) as the catalyst. Recently, many attempts for obtaining biodiesel from waste cooking oil (WCO) have been reported 1,2. Secondary waste steel slags have been used as active and selective catalyst for the synthesis of fatty acid methyl esters (FAMEs) starting from soybean oil under conventional heating (120°C), taking several hours (12 h) to reach completion 3. Generally, microwave-assisted conditions allow to shorten reaction times and decrease operation temperature. In this study, microwave (MW) irradiation protocols were developed for fast and low energy consuming biodiesel synthesis from WCO in the presence of secondary steel slags as the catalyst at different temperatures and time conditions. Quantitative WCO conversion into FAMEs was achieved at 110 °C under microwave irradiation taking only 20 min reaction time (Scheme 1). Steel slags were characterised by several analytical techniques, such as Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffraction (XRD) and Thermogravimetric Analysis (TGA).