ZnO/La2O2CO3 layered composite: A new heterogeneous catalyst for the efficient ultra-fast microwave biofuel production

The search for solid state materials with high catalytic activities and with no leaching into the reaction medium is one of the key steps toward reducing the cost of producing biodiesel. We report a high biodiesel yield (>95%) in less than 5 min under mild reaction conditions (<100 °C) on a ZnO/La2O2CO3 heterogeneous catalyst, showing no catalyst leaching into the reaction medium. The ZnO/La2O2CO3 catalyst is prepared by a co-precipitation method and characterized by X-ray diffraction (XRD), thermogravimetric analyses (TGA), transmission electron microscopy (SEM), and transmission electron microscopy (TEM). The fatty acid methyl ester (FAME) yields as function of different amounts of catalyst was also investigated. Less than 1.0 wt.% catalyst can be used in the reaction to get higher than a 95% FAME yield under mild reaction conditions. The catalytic performance is maintained after storing the catalyst in Ar for a month and no catalyst leaching into the products was found based on XRF analysis. The catalyst has a higher reaction rate than the homogeneous KOH catalyst with the assistance of microwave irradiation. All of these results promote the industrial application of the synthesized ZnO/La2O2CO3 as an ideal catalyst for fast biodiesel production, avoiding many of the issues found in both commercial and independently published catalysts.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ First example of low temperature active heterogeneous catalysts for environmentally friendly biodiesel production without a leaching problem. ▶ New and simple synthesis method for preparing La2O2CO3 layered materials. ▶ No leaching of Zn or La was found in the biodiesel product. ▶ First time reporting La2O2CO3 layered materials as active catalyst for transesterification reaction. ▶ Rapid reaction time for almost complete biodiesel conversion (5 min) at low reaction temperatures (85 °C).