Percorrer por autor "Vieira, Admilson L."
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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.
- Effect of plant biostimulants on nutritional and chemical profiles of almond and hazelnutPublication . Pascoalino, Liege; Reis, Filipa S.; Barros, Lillian; Rodrigues, M.A.; Correia, Carlos M.; Vieira, Admilson L.; Ferreira, Isabel C.F.R.; Barreira, João C.M.The increasing interest in natural foods with functional effects demands progressively higher production levels. Nonetheless, there is an orientation towards practicing more sustainable agriculture, free from environmentally harmful pesticides and fertilizers. Plant biostimulants, a class of bio-based agriculture products designed to improve crop development, represent a feasible alternative to chemical fertilizers, or, at least, an effective way of reducing the employed quantities. Herein, different types of plant biostimulants compatible with organic farming (Phytoalgae, Foliar B, Amino Acids, Soil B, Fitoalgas Green® and Sprint Plus®) were tested in two of the most important nut products worldwide: almonds and hazelnuts, which were tested for nutritional parameters, fatty acids profiles and tocopherols contents. Overall, the most notorious effects in almond samples were obtained with phytoalgae (seaweed Ascophyllum nodosum extracts), particularly reflected in the upraising around 10% of -tocopherol and -tocopherol contents. Likewise, hazelnuts treated with NPK + phytoalgae were also characterized by an increase of almost 18% in tocopherols levels, while treatment with NPK alone induced 15.1% higher percentage of linoleic acid.
- 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.
- Simulation of a downdraft gasifier for production of syngas from different biomass feedstocksPublication . Paiva, Mateus Vinicius; Vieira, Admilson L.; Gomes, Helder; Brito, PauloIn the evaluation of gasification processes, estimating the composition of the fuel gas for different conditions is fundamental to identify the best operating conditions. In this way, modeling and simulation of gasification provide an analysis of the process performance, allowing for resource and time savings in pilot-scale process operation, as it predicts the behavior and analyzes the effects of different variables on the process. Thus, the focus of this work was the modeling and simulation of biomass gasification processes using the UniSim Design chemical process software, in order to satisfactorily reproduce the operation behavior of a downdraft gasifier. The study was performed for two residual biomasses (forest and agricultural) in order to predict the produced syngas composition. The reactors simulated gasification by minimizing the free energy of Gibbs. The main operating parameters considered were the equivalence ratio (ER), steam to biomass ratio (SBR), and gasification temperature (independent variables). In the simulations, a sensitivity analysis was carried out, where the effects of these parameters on the composition of syngas, flow of syngas, and heating value (dependent variables) were studied, in order to maximize these three variables in the process with the choice of the best parameters of operation. The model is able to predict the performance of the gasifier and it is qualified to analyze the behavior of the independent parameters in the gasification results. With a temperature between 850 and 950 C, SBR up to 0.2, and ER between 0.3 and 0.5, the best operating conditions are obtained for maximizing the composition of the syngas in CO and H2.