Lithium and calcium based perovskite type oxides for ethylic transesterification

Abstract

ABO3 basic catalysts were synthesized by the nitrate-b-alanine solution combustion method at about 400 °C. The powders were formed by combustion route in times up to 5 min and presented high crystallinity and a single-phase, without the calcination step. XRD analyses showed that the oxides containing calcium (CaZrO3 and Ca0.9Li0.6Zr0.9O3) presented perovskite structure with the orthorhombic system, whereas a monoclinic structure was observed in the oxide Li2ZrO3. The catalysts were characterized by FEG-SEM, TPD-CO2, TGA, N2 physisorption (BET) and ICP OES. The catalytic activity of the materials was tested in the transesterification of both methyl acetate (model reaction) and soybean oil with ethanol to produce biodiesel. Ca0.9Li0.6Zr0.9O3 was the most active oxide in the model reaction, reaching a maximum conversion in ethyl acetate of 92%, followed by the oxide Li2ZrO3, with the conversion of 64%. The CaZrO3 catalyst conversely presented negligible catalytic activity. Reuse tests have indicated that the catalysts containing Li can be reused for up to six reaction cycles, with an average conversion of around 50% up to its sixth reuse. Ca0.9Li0.6Zr0.9O3 also shows promising for the biodiesel production since its FAEEs yield was good (60% m/m) under mild reaction conditions (molar ratio oil/ethanol 1:12 and 50 °C for 30 min). It was noticed that the incorporation of Li to calcium zirconate has resulted in more efficient and promising catalysts for the transesterification, what is possibly related to the textural and basic alterations occurred with the Li insertion. Although the metallic ions leaching of the most active materials has been detected, no reaction was observed in homogeneous phase.