Avaliação do desempenho e reuso do catalisador nanomagnético Ni0,5Zn0,5Fe2O4 na produção de biodiesel.

Abstract

Worldwide, much attention has been focused on the use of biomass for the production of so-called "engineering materials". Among the variety of products, biodiesel occupies a prominent position, not only in terms of quantity produced worldwide, but also because of its features related to clean energy because combines unique features such as renewability, biodegradability and environmental benefit. Many researches are conducted to produce advanced materials that increase the biodiesel production process, for example, catalysts that exhibit jointly high activity, selectivity, strength, filterability, regeneratable for reuse, and therefore minimize overall costs of obtaining biodiesel. This work aims to synthesize by combustion reaction, in pilot scale, magnetic nanocatalysts of Ni0.5Zn0.5Fe2O4 and evaluate their performance in esterification and transesterification reactions to obtain biodiesel. The nanocatalysts were synthesized in production scale with capacity of 10, 100 and 200 g/output per batch. During the synthesis were measured combustion temperature and time flame reactions, and the products of the reactions were characterized by XRD, EDX, FTIR, BET, SEM, TEM, TG, GD, ED, TPD and magnetic measurements. The bench catalytic tests were performed at temperatures of 160 to 180 °C with molar ratios of oil/ethanol of 1:9, 1:12, 1:15, using 4, 2, and 3% of nanocatalyst, during 2 and 1 h. The reaction products were characterized by gas chromatography, kinematic viscosity, density, and acid and iodine values. Analysis of the results revealed that the three nanocatalysts showed the formation of the major phase of the Ni-Zn ferrite and discrete traces of the segregated phases ZnO and Fe2O3, quantified by Rietveld refinement. The chemical compositions of the present oxides were according to the stoichiometry expected, showed characteristic bands of the inverse spinel type and morphologies formed by agglomerates in the form of irregular blocks. The surface area values between 51 and 65 m2 /g, with the classification of pores in the mesoporous range. They showed characteristic of soft magnetic material, with saturation magnetization values of approximately 20 to 37 emu/g, excellent thermal stability and the presence of acid sites. The three nanocatalysts were active for esterification and transesterification reactions of the soybean oil, with special emphasis on the esterification reactions, whose biodiesel conversion values ranged from 96.7 to 98.59% to the ethyl route and from 97.5 to 99.54% to the methyl route, both above the minimum value required by the applicable law. The nanocatalyst produced in larger scale was recovered by means an external magnetic field (magnet), and reused three times without significant loss of the catalytic activity, with an average conversion into biodiesel of 98.95 ± 0.44%. Therefore, among the obtained results, validates the Ni0,5Zn0,5Fe2O4 ferrite with the differential of the pilot scale production, as potential heterogeneous magnetic nanocatalyst, and environmentally beneficial for biodiesel production.