Desenvolvimento de catalisador heterogêneo para síntese de biodiesel em sistema contínuo

Abstract

The growing interest in biodiesel production has encouraged studies that enable the generation of national technology in this field, considering that, industrially, biodiesel is already produced in continuous systems, but the price of the final product is still high. In the present work, the objective was to synthesize and apply basic catalysts in heterogeneous biodiesel production processes through ethyl and methyl transesterification, aiming at the production of mechanically and chemically stable pellets for application in a system for the continuous production of biodiesel in a rotating reactor under heating. by microwave radiation. To this end, oxides of the x-SrO-CaO-Al2O3 type were synthesized using the hydrothermal method, followed by characterizations regarding their crystallinity, morphology, thermal profile and chemical composition. Initially, the synthesized catalysts were applied in a batch system for the ethyl and methyl transesterification model reaction, evaluating conditions such as contact time, reuse and homogeneous contribution and, then, in the reaction with soybean oil. Pelletization was carried out under different proportions between catalyst and binder, as well as by different heat treatments. After meeting the stipulated requirements, the pellets were applied in a continuous system under microwave irradiation. Conversion analysis was followed by gas chromatography. The results showed effectiveness in the hydrothermal synthesis method, which favored the formation of a catalyst suitable for transesterification (0.8-SrO-CaO-Al2O3). In just 5 minutes of reaction, 95% and 72% conversion for methyl and ethyl transesterifications, respectively, was achieved, with a homogeneous contribution of 5% for both cases. The 0.8-SrO-CaO-Al2O3 catalyst demonstrated stability for reuse, maintaining 95% conversion for 6 reaction cycles in methanolysis and ~80% for 4 cycles for ethanolysis. For the process carried out with vegetable oil in batch, 88% conversion to methanolysis was achieved after 60 min of reaction, however, under the same conditions adopted there was no conversion to ethanolysis. When applying the pellets in the proposed continuous system, it was noticed that the conversions were low (<5%), however, the material did not disintegrate in the process. In general, the need for new investigations to evaluate conditions that can maximize the catalytic activity of the pellet was perceived, since the use of the catalyst in this form represents a promising alternative to overcome the challenges linked to continuous production for packed bed systems.