Desenvolvimento de procedimentos para a síntese e caracterização de catalisadores e de biodiesel

Abstract

ABO3 basic catalysts were synthesized by the nitrate-b-alanine solution combustion method. The catalysts powders were produced by self-combustion in times up to 5 min, presenting high crystallinity and single-phase, without the calcination step. XRD analyses showed that the produced calcium oxides (CaZrO3 and Ca0.9Li0.6Zr0.9O3) presented perovskite structure with the orthorhombic system, whereas a monoclinic structure was observed for Li2ZrO3 oxide, results confirmed with the Rietveld refinement. Different techniques were used to characterize the catalysts, such as MEV-FEG, TPD-CO2, TGA, N2 (BET), ICP OES, MIP-OES, WD-XRF and FT-IR. Different methods of acid decomposition were employed, instead of HF, for elemental analysis of the oxides. Recovery values were observed between 92 and 101%, with low deviations and LOQs. The catalytic activity of the synthesized materials was tested by the reaction of ethyl transesterification with methyl acetate (model reaction). The Ca0.9Li0.6Zr0.9O3 was the most active oxide, reaching 92% conversion to ethyl acetate, followed by oxide Li2ZrO3, with 64% conversion. The CaZrO3 had negligible catalytic activity. Reagent tests of Li-containing catalysts indicated average conversion of about 50% up to the 6° recycle. The Li incorporation to zirconate produced changes in the textural and basic properties, resulting in more efficient and promising catalysts for the transesterification. The Ca0.9Li0.6Zr0.9O3 was also evaluated in the oil transesterification reaction for biodiesel production, with a yield of 60% m/m under mild reaction conditions (molar ratio 1:12 oil/ethanol and 50 °C for 30 min). Although the metallic ions leaching from the most active materials has been detected, no reaction was observed in the homogeneous phase. A system composed of a rotating packed bed reactor and a microwave oven (RPB + MW) was developed for the continuous flow biodiesel production by the ethylic transesterification instant reaction under heterogeneous catalysis. Total ester content of 19% was obtained with 1 min of product collect time, demonstrating a promising system for the proposed application.