Navegando por Assunto "Termogravimetria"

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Acesso aberto (Open Access)
Análises cromatográficas por CLAE-DAD, termogravimétricas e morfo-anatômicas de amostras comerciais de Echinodorus macrophyllus (Kunth) Micheli (Chapéu-de-couro)
(Universidade Federal do Pará, 2010) FREITAS, Cristian Barbosa de; BORGES, Fernanda Iikiu; BARBOSA, Wagner Luiz Ramos; http://lattes.cnpq.br/1372405563294070
For quality control of the commercial sample of Echinodorus macrophyllus were analyzed with botanical, pharmacognostic and physical-chemical properties. To achieve the anatomical cuts was rehydrated, sectioned with steel blade and fixed on slides semi-permanent. The sections were cleared in 20% NaClO and stained with astra blue-to-follow basic fuchsin. In cross section the epidermis is uniseriate with cells of rectangular shapes, heterodimensional, smooth and thin cuticle. For realization of thermogravimetry was used both drugs as solids at a heating rate of 5, 10 and 15 degrees Celsius. The chromatography was performed in HPLC and sample was obtained from column chromatography and eluted by gradient with methanol and acidic water. The palisade tissue consists of two layers of cells. The parenchyma spongy cells have thin walls, heterodimensional, different formats and well-developed intercellular spaces. The vascular bundles are collateral. The leaf is amphistomatic with stomata paracytic. Petiole in cross section, has a triangular to hexagonal. The epidermis is uniseriate with cells of polygonal shape, smooth walls, large amounts of aerenchyma which sometimes occur diaphragms. Samples of the leaf have characteristics of the species E. macrophyllus, but the anatomy of the petiole showed different structures from those described for the species, which belong to the genus Echinodorus, however suggests possible contamination of the material supplied with other plant species. Thermogravimetric analysis contributed significantly to establish parameters and characterize the sample.
Acesso aberto (Open Access)
Estudo de processo de upgrading catalítico de vapores da pirólise de resíduos plásticos de equipamentos de informática em reator catalítico com carvão ativado impregnado com NaOH
(Universidade Federal do Pará, 2023-04-03) COSTA, Augusto Fernando de Freitas; MACHADO, Nélio Teixeira; http://lattes.cnpq.br/5698208558551065
This study investigated thermal cracking and catalytic upgrading of plastic waste from computer equipment on a semi-batch reactor coupled to a heated catalyst fixed bed (2-stage vapor cracking). The catalyst used was a Si–Al ash obtained from commercial activated carbon pellets treated with concentrated NaOH solution and calcination. The purpose of the study was to characterize the waste stream through its thermogravimetry (TG) analysis and pyrolysis products, study the effect of temperature (350 - 500 °C) and catalyst quantity (0.0 - 7.5 wt%) on yields of reaction products, physical chemical properties, and chemical composition of organic liquid product in order to understand and evaluate production of fuels and chemical feedstock by recycling of plastic waste from computer equipment through catalytic upgrading. Time fractioned samples were taken in determined reaction times (15 min, 30 min, 45 min, and 60 min) to study the evolution of cracking reactions during experiment runs through changes to chemical composition (GC-MS). A comparison with other previous work was also presented to show similarities between different feedstocks using the same thermal unit. The results indicate composition of brominated acrylonitrile-butadiene-styrene (Br-ABS), polycarbonate (PC), and high impact polystyrene (HIPS) for the plastic waste from computer equipment. The temperature of 350 °C produced better results when considering acid value but presented lower liquid phase yields (38 %) and high gas phase yields (42 %). Catalytic upgrading experiments revealed the increased presence of polycyclic aromatic hydrocarbons (PAH) with an increase in kinematic viscosity of organic liquid product, increase in char yield (from 11 % to 24 %), and decrease in gas yields (15 % to 5 %). Chemical composition showed presence of aromatic hydrocarbons such as styrene, methyl-styrene, and diphenyl-propane and nitrogenated compounds such as benzene butane-nitrile, phenolic compounds, polycyclic aromatic hydrocarbons, and brominated compounds. Plastic waste from computer equipment pyrolysis is a challenging subject due to contaminant presence and varying composition, and chemical composition evaluation according to reaction time provides interesting insights into the evolution of semi-batch pyrolysis/catalytic upgrading experiments. Standardization and reproducibility of the tool should be conducted to continue the evaluation of pyrolysis and catalytic upgrading of a wide range of feedstocks.