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Browsing by Author "Batista, Maria Clara Carneiro"

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  • Catalytic application of carbon nanotubes obtained from solid waste for oxidative desulfurization of a simulated fuel with a green solvent
    Publication . Batista, Maria Clara Carneiro; Gomes, Helder; Mambrini, Raquel Vieira
    This study focuses the development and evaluation of various carbon nanotubes (CNTs) for biphasic oxidative processes involving the degradation of dibenzothiophene (DBT) in isooctane, a model contaminant in fuel, simulating contaminated fossil fuels, by Oxidative Dessulfurization (ODS). Hydrogen peroxide was used as oxidation source in these processes, and water as extractive phase. The CNTs were synthesized via chemical vapor deposition (CVD) using different polymers as carbon resource, leading to CNT- MIX (from a mixture of polyolefins), CNT-PS (from pure polystyrene), and CNT-MIX-PS (from polyolefins/polystyrene). Nickel ferrite (NiFe2O4) supported on alumina was used as metallic catalyst in the CVD process. The synthesized materials underwent treatment with sulfuric acid and nitric acid, and characterized by Fourier Transformed Infra-Red (FTIR) spectroscopy, metal and ash content analysis, acidity/basicity determination, N2 adsorption-desorption isotherms, and contact angle measurements. The most promising material, CNT-MIX, was further characterized using Raman spectroscopy and Thermogravimetric analysis (TG). The characterizations revealed the presence of metallic residues of Fe and Ni in the nanotubes, besides the incorporation of acidic and basic sites on the surface of the materials. The contact angle measurements revealed variations in hydrophobicity/hydrophilicity among the synthesized materials and specific surface areas (SBET) ranging from 73 to 98 m2 g-1. The DBT removal tests were conducted over a reaction time of 8 hours, and the results demonstrated satisfactory performance, with the best material (CNT-MIX) achieving 77% removal of DBT by ODS. Additionally, the materials were tested in adsorption systems in the oil phase and aqueous medium, with no significant adsorption being observed in either case. Further tests were conducted using CNT-MIX to enhance the results and align the experimental conditions with those reported in the literature. Acetonitrile was employed as extractive phase, and the impact of formic acid on these systems was evaluated. By using acetonitrile as extractive phase and a combination of H2O2 and formic acid as oxidizing agents, complete removal of DBT (100%) was achieved within 8 hours. The findings of this work highlight the effectiveness of these materials as catalysts, adsorbents, and potentially as phase transfer catalysts for facilitating biphasic oxidative reactions.
    2024Master thesis Open access Show more