Avaliação catalítica do óxido de nióbio/óxido de cobre suportados em filossilicatos em reações de pirólise do óleo de cártamo

Abstract

Niobium-based catalysts have gained prominence due to their properties, such as selectivity, chemical stability, and high catalytic activity, with significant potential for technological advancements. Brazil, as a global leader in niobium reserves, plays a strategic role in researching its oxides, such as niobium pentoxide, aiming at improvements in quality of life. Additionally, the use of vermiculite-type clay minerals is appealing due to their surface properties and ability to deposit metal oxides.In this study, safflower oil was used as a raw material for producing high-value-added byproducts. To degrade safflower oil, four catalysts were synthesized: vermiculite (V0), acid-treated vermiculite (V2A), acid-treated vermiculite supported with niobium oxide (V2ANb), and acid-treated vermiculite supported with niobium oxide and copper oxide (V2ANbCu). These catalysts were characterized using X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-Ray Fluorescence (XRF), and acidity analyses. The catalysts' effectiveness was evaluated through a pyrolysis process using Thermogravimetry (TG). Kinetic analyses were performed using isoconversional models, specifically Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The V2ANbCu catalyst demonstrated the lowest activation energy values, with 134.5 kJ mol⁻¹ and 153.10 kJ mol⁻¹ for the FWO and KAS models, respectively. Thermodynamic parameters, including enthalpy (ΔH), Gibbs free energy (ΔG), and entropy (ΔS), were calculated based on the apparent activation energy values obtained from the kinetic models. The compositional characteristics of the bio-oils, influenced by the catalytic environment, confirmed the formation of new catalytically active sites due to the modifications made to the vermiculite. GC-MS analysis of the bio-oils revealed a predominance of acidic compounds in their composition. After subsequent hydrotreatment of the bio-oils using Pd, a hydrocarbon content of approximately 66% was achieved, both in the bio-oil produced with V0 and that produced with V2ANbCu, which showed 26% hydrocarbons. Thus, using catalysts derived from modified vermiculite in thermocatalytic pyrolysis emerges as a promising alternative for transforming safflower oil, as it reduces the process's activation energy and improves selectivity for products with industrial value.