Doutorado em Química

URI Permanente para esta coleção

http://repositorio.ufes.br/handle/10/17501

Nível: início
Ano de início: 2014
Conceito atual na CAPES: 5
Ato normativo: Homologação da 85ª Reunião do CTC-ES, Parecer CNE/CES nº 163/2005.
Processo nº 23001.000081/2005-56 do Ministério da Educação.
Publicado no DOU 28/07/2005, seção 1, página 11)
Periodicidade de seleção: Anual
Área(s) de concentração: Química
Url do curso: https://quimica.vitoria.ufes.br/pt-br/pos-graduacao/PPGQ/detalhes-do-curso?id=956/a>

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Agora exibindo 1 - 5 de 15

Qualidade química de suco de uva comercial, perfil químico de bananas e açaí juçara e atividade quimiopreventiva de câncer de extratos de bananas
(Universidade Federal do Espírito Santo, 2019-06-27) Oliveira, Bruno Gomes de; Endringer, Denise Coutinho; Romão, Wanderson; Costa, Helber Barcellos da; Filgueiras, Paulo Roberto; Cunha Neto, Álvaro; Ventura, José Aires
Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT ICR-MS) allied to electrospray ionization (ESI) is a powerful tool for chemical analysis. In this work, a methodology was developed for the identification and quantification of grape juice with apple juiceadulteration. Anunivariate and two multivariate calibration models (PLS and MRL) were developed. The three models presented results with good precision and accuracy. Eleven samples of commercial whole grape juice were tested. Of these eleven samples, two of them presented apple juice content of approximately 24% m/m and the other nine juices investigated they either did not contain apple juice or had a content below the limit of quantification.In addition, using the ESI(-) FT ICR-MS, it was possible to study the glycidic and phenolic profile of bananas of the Pacovan, Ambrosia, Vitória, Japira, Prata Comum and Tropical varieties at four maturation stages. It was possible to observe the increase of the carbohydrate content in the fruits, during maturation. The Prata (Japira, Vitória, PrataComum and Pacovan) bananas had a monosaccharide content higher than the disaccharide content. Conversely, Gros Michel (Ambrosia) and Maçã(Tropical) had a higher disaccharide content than the monosaccharide content. The polyphenolic profile of these samples indicated a predominance of flavonoids and cinnamic acids, of which 20 polyphenols were detected, for example: epicatechin, hexoside ferulic acid, caffeic acid derivative, gallic acid derivative, proanthocyanidin and quercetin deoxyhexosehexoside.The cancer chemopreventive potential associated with quinone reductase induction,inhibition of the nitric oxideproduction, NF-kB and aromatase were also analyzed.Pacovan cultivar, maturation stage 2, showed high inhibition of NF-kB whereas Japira cultivar, at maturation stages 2, 4 and 7 and Ambrosia, stage 4, showed aromatase inhibition higher than 50%. All samples except Pacovan at maturity stage 7, Tropical at maturation stage 7, showed inhibition of iNOS greater than 80%.The polyphenolic profile of seven genotypes ofjuçara was also investigated in this work. Polyphenols were classified into three phytochemical classes: flavonoids, phenolic acids and anthocyanins, with the most abundant flavonoid class.Among the identified compounds are dihydrokaempferol, protocatecuic hexoside acid, syringe hexoside acid, orientin and malvidin-glycoside.
Mecanismo de degradação da Goma Guar submetida a escoamento turbulento
(Universidade Federal do Espírito Santo, 2019-04-16) Motta, Marcus Vinícius Lisboa; Castro, Eustáquio Vinicius Ribeiro de; Silva Filho, Eloi Alves da; Filgueiras, Paulo Roberto; Loureiro, Bruno Venturini; Martins, André Leibsohn
Internal turbulent flows are commonly found in industrial applications in fluid transport. This flow regime is associated with additional energy losses in relation to the laminar flow due to the existence of complex dissipative structures in the flow and to the greater friction suffered by the flow with the internal walls of the pipe. In order to maintain this flow regime, the main flow must supply energy from the pumping unit. Reducing the demand for energy to promote internal turbulent flows can be done by the injection of drag reducing additives, usually polymeric in nature. In the studied condition the polymers undergo mechanical degradation and lose the ability to promote drag reduction over time. Studies indicate that the drag reduction may be related to the flexibility of the polymer and the size of the macromolecules of the additive used, which can interact with the vortices and reduce energy dissipation. In this study, the aqueous solution of the guar gum polysaccharide 400 ppm was subjected to a turbulent flow regime with the objective of monitoring, in an experimental plant, molecular degradation, drag reduction and energy demand. For this purpose, solution samples were removed during two hours of flow and the polysaccharide was isolated for characterization of the degradation. FTIR and NMR spectroscopy suggest that the mechanical degradation occurs with the hydrolysis of the a (1 ? 6) bond of the main chain with (D) -galactose due to the appearance of the carbonyl functional group. Thermal analysis revealed a decrease in the thermal stability of the polysaccharide by the decrease of the polymer chain. Finally, the understanding of this mechanism aims at the use of more efficient polymers in the reduction of drag and the decrease of the demand of energy in pumping processes that use these drag reducing macromolecules. Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and viscosity in diluted solution were analyzed. It was characterized, that the drag reduction efficiency promoted by guar gum is compromised by the polysaccharide undergoes chemical degradation, promoted by mechanical stress. As evidence, the viscosimetric analysis of guar gum showed the reduction of molecular weight in the period. FTIR and NMR spectroscopy suggest that the mechanical degradation occurs with the hydrolysis of the a (1 ? 6) bond of the main chain with (D) -galactose due to the appearance of the carbonyl functional group. Thermal analysis revealed a decrease in the thermal stability of the polysaccharide by the decrease of the polymer chain. Finally, the understanding of this mechanism aims at the use of more efficient polymers in the reduction of drag and the decrease of the demand of energy in pumping processes that use these drag reducing macromolecules.
Reciclagem sustentável do anodo de baterias exauridas deNi-MH: sínteses dos óxidos de níquel e lantanídeos pelos métodosde precipitação seletiva, sol-gel e coprecipitação
(Universidade Federal do Espírito Santo, 2019-04-03) Marins, Antonio Augusto Lopes; Freitas, Marcos Benedito José Geraldo de; Silva Filho, Eloi Alves da; Castro, Eustáquio Vinícius Ribeiro de; Prado, Adilson Ribeiro; Entringer, José Marcos Stelzer
Determinação de propriedade físico-químicas de biodiesel e blendas por RMN de baixo campo e calibração multivariada
(Universidade Federal do Espírito Santo, 2018-11-06) Constantino, André Fazolo; Lacerda Junior, Valdemar; Consalter, Daniel Martelozo; Santos, Reginaldo Bezerra dos; Cunha Neto, Álvaro; Barbosa, Lúcio Leonel
Because the methods specified by regulatory agencies for the determination of the physicochemical properties of biodiesel can be laborious and expensive, the development of alternative methodologies represents a major breakthrough. Thus, low-field nuclear magnetic resonance (NMR) is an advantageous option because it is nondestructive and reduces the cost and time consumption. In this study, the partial least squares (PLS) regression method was used to create models that correlated the decay curves of the Carr–Purcell–Meiboom–Gill (CPMG) signal, Continuous Wave Free Precession (CWFPx-x) orCarr–Purcell Continuous Wave Free Precession (CP-CWFPx-x), obtained fromlow-field NMR equipments(2.2 MHz and 15.0 MHz for 1H), with the kinematic viscosity, specific mass,refractive index and iodine value of biodiesel and their blends. Seventeen oilseeds diversified between edible and non-edible oils were utilized to synthesizethe biodiesel and producebinary blends.Separately, multivariate calibration models were created only with pure biodiesel and blends withcastor bean because these samples showed different tendencies from the others. The best values of root mean square error of prediction (RMSEP) for the kinematic viscosity, specific mass and refractive index were equal to 0.1 mm2/s, 1.9 kg/m3, 0.002 and 15.5 g I2/100 g of sample,respectively, for samples of biodiesel and blends without castor bean and 0.3mm2/s, 1.3kg/m3,0.0003 and 1.9 g I2/100 g of samplefor samples of biodiesel and blends with castor bean. The results reveal that the developed models are very satisfactory to predict the quality parameters of biodiesel and blendswith fairly good efficacy, withthe models created withCPMG andCP-CWFPx-xdata being stood out to those constructedwith CWFPx-xdata. The physicochemical properties were also correlated with the decay curves of seed and oil samples, with the aim of predicting the quality of biodiesel from the analysis of its raw materials. However,the resultswere not very promising, sincethe correlations betweenmeasured physicochemical properties by American Society for Testing and Materials (ASTM) methods and its predicted values from the constructed PLS models resulted in very low coefficients of determination (R2)
Investigação sobre materiais híbridos obtidos a partir de óxido de grafeno com incorporação de sílica ou de grupos contendo fósforo
(Universidade Federal do Espírito Santo, 2018-12-18) Vieira, Mariana Arpini; Freitas, Jair Carlos Checon de; Emmerich, Francisco Guilherme; Lacerda Junior, Valdemar; Dalmaschio, Cleocir José; Alves, Klinger Marcos Barbosa; Porto, Arilza de Oliveira
The reduction of graphene oxide (GO), which can be accomplished by the combination of thermal and chemical treatments, leads to the production of a material known as reduced graphene oxide (rGO); this material exhibits good electrical conductivity and, despite the presence of structural defects and chemical heterogeneity, can represent a viable and low-cost alternative to pure graphene in several applications. In the presentwork GO was produced by both Hummers and Tour methodsfrom an Li-ionbattery recycled graphite powder, varying the final content of phosphorusand sulfurby modifying the proportion of the reactants (H2SO4/H3PO4). After centrifugation the materialsweredried and concomitantly lead to thermal reduction under ambient atmosphere and at different temperatures (80, 100 and 150 °C). The products were characterized by X-ray diffraction (XRD), thermogravimetry, solid-state 13C and 31P nuclear magnetic resonance (NMR) and X-ray fluorescence. 13C NMR results show that the treatment of the materials at higher temperatures causes the progressive disappearance of the peaks associated with the oxygenated functional groups, leading to an NMR spectrum dominated by a largeresonance peak associated with sp2hybridized carbon atoms. 31P NMR results indicate that phosphorus is present in rGOsamples in the form of phosphonate groups (with P-C bonds), polyphosphoric acids (present in chains formed by the condensation of phosphate groups) and orthophosphoric acid.Furthermore, it was possible to synthesize rGO samples containing approximately 5% (m/m) of Pand 2% (m/m) of S, as stated by XRF analysis.A method of synthesizing a GO-SiO2hybrid material was also proposed, using the GOsuspension in the synthesis procedure, eliminating the drying step of the GO for its application in the preparation of the hybrid material. Results of solid-state29Si and 13C NMR,SEM, XRD and FT-IR showed that the proposed method allowed the synthesis of hybrids with different silica contents (~ 22and 46%m/m). In addition, the results of XRD, 29Si NMR, FT-IR and TG/DTG indicated the presence of nanostructured or amorphous silica and suggested the interaction of the silica particles with the GO matrixby hydrogen bonds between the silanol groups and the oxygenated functionalities of GO, and by Si-O-C bonds formed from the reaction of the carboxylic acids of the GOwith the silanol groups

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