Conversion of plastic solid wastes into carbon nanotubes: effect of operating conditions

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáAn 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.Um tratamento eficiente de resíduos plásticos traz benefícios ambientais, sociais e econômicos notáveis. Portanto, neste trabalho é proposta a valorização de resíduos plásticos em sua conversão para nanotubos de carbono (CNTs). Para que o processo ocorra, é necessário um catalisador que contenha metal de transição. Então é feito um catalisador de ferro suportado em alumina, Fe2O4/Al2O3, pelo método de sol gel no qual seu rendimento foi em torno de 25% de ferro. O método para formação dos nanotubos é a deposição química em fase vapor (CVD) que permite realizar o controle do tamanho das nanoestruturas de carbono formadas, com o uso de catalisadores adequados ao processo. Tanto para o controle do tamanho quanto para maior rendimento do material são diversas variáveis, as estudadas serão: o catalisador, o caudal e a temperatura que ocorrerá o CVD. Também serão usados três tipos de polímeros: polietileno de baixa densidade (LDPE), polietileno de alta densidade (HDPE) e polipropileno (PP), e uma mistura (MIX) entre eles. No qual a melhor condição para formação dos CNTs foi 40 mL/min de nitrogênio e a 800 °C com os seguintes rendimentos: 16.9 (LDPE), 8.5 (HDPE), 6.7 (PP) and 8.9 (MIX) %, respectivamente. A maioria das amostras foram purificadas com 50 % de ácido sulfúrico. Cinzas, acidez e basicidade, SBET, DRX, e FT-IR foram os métodos de caracterização. Nas cinzas, a purificação retirou boa parte do conteúdo inorgânico, assim como pela titulação ácido-base, demostrou que os CNTs tiveram caráter ácido comprovado pelo FT-IR. O DRX mostrou ser Fe2O3 o catalisador produzido, e com as cinzas provou ser o mesmo material pela coloração avermelhada. E por análise de porosimetria demonstrou serem materiais dentro do intervalo de 159-242 m2/g, com seus gráficos de adsorção e dessorção resultando um material mesoporoso, característico de nanotubos.This work is a result of project PLASTIC_TO_FUEL&MAT, with reference POCI 01 0145-FEDER-031439 and CIMO - UIDB/00690/2020 financed through FCT/MCTES (PIDDAC)

Oxidative denitrogenation of a simulated fuel under a biphasic green system

Este 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 comercialThis work deals with the catalytic denitrogenation of a simulated fuel (quinoline (QN) in 2,2,4-trimethylpentane) by oxidation with hydrogen peroxide in a biphasic medium. As catalysts, three materials were used (i) iron supported on alumina (Fe/Al2O3) obtained by sol-gel, carbon nanotubes (CNT) produced by chemical vapor deposition of propylene (PP) growth on the previous catalyst (Fe/Al2O3) and (iii) a commercial sample of CNT supplied by Sigma Aldrich. The contribution of adsorption and extraction was also assessed, both being considered negligible or ineffective for the removal of QN. The performance of each catalyst was analysed in 4 h reaction tests, at 80 °C, by monitoring the degradation of H2O2 and the concentration of QN in the oily and aqueous media. As a result, all catalysts used met the proposed objective, with 100% of QN being removed from the oily phase in the biphasic oxidation tests. In summary, all the catalysts produced were efficient in the proposed process and are comparable to the performance obtained by the commercial CNT sample.This work was financially supported by project “PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials” (PTDC/EQU-EQU/31439/2017), LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM), funded by national funds through FCT/MCTES (PIDDAC) and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the national funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019. Jose L. Diaz de Tuesta acknowledges the financial support through the program of “Atracción al Talento” of “Comunidad de Madrid” (Spain) for the individual research grant 2020-T2/AMB-19836.info:eu-repo/semantics/publishedVersio

iphasic oxidative denitrogenation with H2O2 of a simulated fuel using sustainable carbon nanotube catalysts

The 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).This work was financially supported by project "PLASTIC_TO_FUEL&MAT – Upcycling Waste Plastics into Fuel and Carbon Nanomaterials" (PTDC/EQU-EQU/31439/2017), Base Funding - UIDB/50020/2020 of the Associate Laboratory LSRE-LCM - funded by national funds through FCT/MCTES (PIDDAC), and CIMO (UIDB/00690/2020) through FEDER under Program PT2020. Fernanda F. Roman acknowledges the national funding by FCT, Foundation for Science and Technology, and FSE, European Social Fund, through the individual research grant SFRH/BD/143224/2019.info:eu-repo/semantics/publishedVersio

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)