Browsing by Author "Piccinin, Larissa"
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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).
- Carbon nanomaterials from polyolefin waste: effective catalysts for quinoline degradation through catalytic wet peroxide oxidationPublication . Roman, Fernanda; Piccinin, Larissa; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Freitas, Isabella V. K.; Vieira, Admilson L.; Lenzi, Giane G.; Silva, Adrián; Faria, Joaquim; Gomes, HelderQuinoline (QN) is highly toxic and carcinogenic and has been detected in soil, groundwater, and biological tissues. Advanced oxidation processes (AOPs) have shown promise to address its degradation in wastewater treatment, with catalytic wet peroxide oxidation (CWPO) being highlighted due to its cost-effectiveness and mild operation. However, developing active and inexpensive catalysts is crucial for CWPO’s effectiveness. Another pressing issue is the accumulation of mixed, dirty plastic solid waste (PSW), particularly polyolefins used in packaging. Although recycling rates have increased, much plastic packaging remains in landfills. However, polyolefins can be converted into carbon-based nanostructured materials (CNMs), such as carbon nanotubes (CNTs), through chemical vapor deposition (CVD) using PSW as a carbon precursor. While many studies focus on CNT preparation, their application is often overlooked. In this context, this work proposes the preparation of CNMs, particularly CNTs, through CVD using a single-stage pyrolysis reactor. Polyolefins (LDPE, HDPE, and PP), both individually and in a mixture simulating PSW, were used as carbon sources. Given a sufficiently high temperature, the desired CNT architecture was successfully synthesized regardless of the starting polymer. These CNMs were then tested as catalysts for CWPO in simulated wastewater containing QN. The results showed a rapid degradation of QN (30–120 min) and high removals of total organic carbon (TOC) and aromatic compounds (75% and >90%, respectively), demonstrating the applicability of PSW-derived CNTs in the CWPO process for QN abatement.
- Catalytic application of carbon nanotubes obtained from plastic solid waste in the removal of quinoline from isooctane by selective oxidation with hydrogen peroxidePublication . Piccinin, Larissa; Gomes, Helder; Vieira, Admilson Lopes; Díaz de Tuesta, Jose LuisDifferent carbon nanotubes were tested in two-phase oxidative processes using hydrogen peroxide as oxidant in order to remove and degrade a model contaminant, quinoline, from isooctane, which simulated contaminated fossil fuels. The CNTs were produced by chemical vapor deposition (CVD) from different polymers. The use of low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP) and a mixture of these three in the proportion of 35:25:40, respectively, resulted in the CNTs defined as CNT LDPE 600, CNT LDPE 800, CNT HDPE 800, CNT PP 800 and CNT MIX 800, where 600 or 800 represent the temperature of pyrolysis considered in the synthesis. The use of such polymers simulated the production of CNTs from residual plastic. Prior to the biphasic oxidation runs, the organic phase underwent oxidation tests, being concluded that isooctane was not oxidized under the conditions used. Possible adsorption on the materials was also tested in the organic phase and in the biphasic medium. In both cases no significant adsorption was obtained. The produced CNTs were tested as catalysts in the oxidative processes of hydrogen peroxide in aqueous solution (CWPO) and in the biphasic medium. The performance of each material was analyzed in 24-hour reaction tests, at 80 °C, through monitorization of H2O2 degradation, quinoline concentration in oily and aqueous media, total organic carbon concentration, aromatics concentration in oily and aqueous media, and pH measurement. In addition to the tests carried out with the CNTs produced, a commercial CNT was also tested for comparison. Finally, all catalysts used fulfilled the proposed objective, 100% of quinoline being removed from the oily phase in the biphasic oxidation runs, up to 8 h of reaction, and degrading 100% of the contaminant by CWPO in 4 h. Other analyses revealed a complete degradation of H2O2 with all CNTs in the CWPO tests and in the biphasic oxidation runs, except for the commercial CNT in the biphasic oxidation run. The analysis of TOC and aromatics concentration show significant decreases with all tested carbon nanomaterials, while pH had a slight decrease in the CWPO runs and an increase in the biphasic oxidation runs. In summary, all carbon materials produced were efficient in the proposed process and are comparable to the performance obtained by the commercial CNT.
- 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
- Selective biphasic oxidation of nitrogenated contaminants with H2O2 using polyolefin-derived carbon nanotubesPublication . Roman, Fernanda; Piccinin, Larissa; Silva, Adriano S.; Díaz de Tuesta, Jose Luis; Vieira, Admilson L.; Silva, Adrián; Faria, Joaquim; Gomes, HelderLiquid/liquid biphasic oxidations are extensively employed in the chemical industry to manufacture a variety of chemicals and for environmental issues, such as the oxidative denitrogenated (ODN) and desulfurization of fuels. The ubiquitous presence of nitrogenated and sulfonated compounds in petroleum-derived fuels is associated with environmental and health issues, driving legislation to become stricter regarding the content or related emissions of those impurities. However, catalysts with high performance, low cost and high activity towards selective oxidation of targeted contaminants should be developed. This work deals with the oxidative denitrogenation of quinoline and pyridine, used as model nitrogenated compounds, using carbon nanotubes as catalysts, which were derived from polyolefins (low-density polyethylene, high-density polyethylene and propylene) representative of plastic solid waste (PSWs) mixtures found in municipal solid wastes. The carbon precursor used offers not only a solution to reduce PSWs accumulation in waste management systems but also a cheap feedstock for preparing CNTs. All PSWs-derived CNTs allowed to remove quinoline completely, pyridine, and both of them in a mixture under the same conditions (1 h, 80 ◦C, ccat = 2.5 g L^-1, [H2O2]0 = 247 g L^-1, O/W volume ratio = 80:20, [N]0 = 108 mg L^-1). These results were maintained for up to 5 additional reuse cycles for the catalyst prepared with mixed polyolefins.