Potassium modified layered Ln2O2CO3 (Ln: La, Nd, Sm, Eu) materials: efficient and stable heterogeneous catalysts for biofuel production

Abstract

Potassium modified layered Ln₂O₂CO₃ (Ln: La, Nd, Sm, Eu) biodiesel catalysts were prepared by a coprecipitation method followed by an overnight reflux. A high fatty acid methyl ester (FAME) yield (>95%) was achieved under mild reaction conditions (<100 °C). The FAME yields were investigated as a function of temperature and catalyst weight percentage. Nd₂O₂CO₃ shows a better catalytic performance with a higher reaction rate than the industrial homogeneous KOH catalyst using both microwave irradiation and conventional heating methods. Approximately 100% FAME yield can be reached at 95 °C (microwave radiation) by 1.0 wt% Nd₂O₂CO₃ within 10 min, while the same yield can be reached by 3.0 wt% Nd₂O₂CO₃ at 95 °C (conventional heating method). In addition, leaching tests of the catalysts were performed; no leached rare earth metal ions were detected and the amounts of leached potassium were all under 5 ppm (ASTM standard). The synthesized layered Ln₂O₂CO₃ materials offer a group of ideal alternative catalysts for industrial biodiesel production.