Browsing by Author "Freitas, Isabella Veronica"
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- Biphasic oxidative denitrogenation with H2O2 of a simulated fuel using sustainable carbon nanotube catalystsPublication . Piccinin, Larissa; Roman, Fernanda; Freitas, Isabella Veronica; Díaz de Tuesta, Jose Luis; Silva, Adrián; Faria, Joaquim; Vieira, Admilson L.; Lenzi, Giane G.; Gomes, HelderThe presence of nitrogenated compounds in liquid fuels (e.g. quinoline (QN), azapyrene, pyrrole, indole or carbazole) is associated with a series of environmental and health issues [1], as upon their combustion, noxious NOx gases are formed. Typically, those heteroatoms are removed by hydrodenitrogenation (HDN), a process based on the application of H2 under high temperature and pressure [2]. However, due to the type of nitrogenated compounds found in crude oils, which consist mostly of cyclic structures containing two double bonds between N and C atoms, HDN fails to efficiently remove nitrogen without affecting the properties of the fuel [1]. Thus, alternatives to HDN have been sought, the removal of those nitrogenated compounds via oxidative processes being found as promising [1]. In oxidative denitrogenation (ODN), nitrogen-based compounds are oxidized towards more polar compounds, which can be further removed from the fuel with an extractant [3]. Furthermore, another contemporary issue is the production and accumulation of residues, especially plastic solid waste (PSW). PSW can be used as precursors for the synthesis of sustainable carbon nanotubes (CNTs), which could be further applied as catalysts in ODN. In this work, a nitrogen-rich fuel was simulated by dissolving QN (CQN-i-octane,0 = 1 g L-1) in 2,2,4-trimethylpentane (i-octane), and ODN was carried out using H2O2 as oxidant and CNTs (derived from a mixture of polymers simulating PSW) as catalysts, under a biphasic system (oxidation and extraction co-occurrence).
- Conversion of plastic solid wastes into carbon nanotubes: effect of operating conditionsPublication . Freitas, Isabella Veronica; Gomes, Helder; Lenzi, Giane Gonçalves; Díaz de Tuesta, Jose LuisAn efficient treatment of plastic waste brings remarkable environmental, social and economic benefits. Therefore, this work proposes the recovery of plastic waste by its conversion to carbon nanotubes (CNTs) by sequential pyrolysis and chemical vapor deposition (CVD). For this purpose, an alumina-supported iron material, prepared by the sol-gel method, was used as catalyst in chemical vapor deposition. This method allows to control the size of the formed carbon nanostructures. To understand the variables affecting the proportion and to maximize material yield, catalyst, flow rate and temperature at which CVD will occur were studied in this work. Three types of pure polymers were used as carbon precursors: low-density polyethylene (LDPE), high-density polyethylene (HDPE) and polypropylene (PP), as well as a mixture of them. The best conditions for the formation of CNTs was found to be 40 mL/min of nitrogen inflow and 800 °C for the polymers, with the following yields, respectively: 16.9 (LDPE), 8.5 (HDPE), 6.7 (PP) and 8.9 (MIX) %. The obtained samples were purified with 50 % H2SO4. Ash content, acidity and basicity, SBET, XRD and FT-IR, were considered for the characterization of the materials. In the ashes, the purification removed a good part of the inorganic content, as the acid-base titration it demonstrated that the CNTs had an acidic character confirmed by the FT-IR. XRD revealed that the iron phase in the catalyst produced was Fe2O3, and the determination of the ash content confirmed the XRD results by the red color of the material at the end. And by porosimetry analysis, they were shown to be materials within the range of 159-242 m2/g, with their adsorption and desorption graphs resulting in a mesoporous material, characteristic of nanotubes.
- Oxidative denitrogenation of a simulated fuel under a biphasic green systemPublication . Roman, Fernanda; Piccinin, Larissa; Freitas, Isabella Veronica; Díaz de Tuesta, Jose Luis; Silva, Adrián; Faria, Joaquim; Vieira, Admilson L.; Lenzi, Giane G.; Gomes, HelderEste trabalho trata da desnitrificação catalítica de um combustível simulado (quinolina (QN) em 2,2,4-trimetilpentano) por oxidação com peróxido de hidrogénio em meio bifásico. Como catalisadores, foram utilizados três materiais: (i) ferro suportado em alumina (Fe/Al2O3) obtido por sol-gel, (ii) nanotubos de carbono (CNT) produzidos através da deposição química em fase de vapor de propileno (PP) sobre o catalisador anterior (Fe/Al2O3), e (iii) os CNT fornecidos pela Sigma Aldrich. A contribuição da adsorção e da extração foi avaliada, sendo ambas consideradas desprezáveis ou pouco efetivas para a remoção da QN. O desempenho de cada material foi analisado em testes de reação de 4 h, a 80 °C, através da monitorização da degradação de H2O2 e da concentração de QN em meio oleoso e aquoso. Como resultados, todos os materiais utilizados atenderam ao objetivo proposto, sendo 100% da QN removida da fase oleosa nos ensaios de oxidação bifásica. Em resumo, todos os catalisadores produzidos foram eficientes no processo proposto e são comparáveis ao desempenho obtido pelo CNT comercial