3125227 documents found, page 8434 of 312523
Modificação da sílica propiletilenodiamina com formaldeído, estudo do equilíbri...
Aguiar, Franklin PessoaIn this work, modified silica gel with the group aminopropiletanoimina was used as retention capacity for the ions cadmium, lead and cromate. The tests were accomplished in aqueous solutions under different conditions of pH, in constant temperature of 298±1 K. The number of mol of the organic chain anchored to the matrix was 0,97mmol /g. The analysis of the curves TG, for the degradation interval between 0,12 a...
Avaliação da estabilidade oxidativa do biodiesel de pinhão manso (Jatropha curc...
Brasilino, Maria das Gracas AzevedoJatropha curcas L. as a raw to produce biodiesel presents a promising alternative because of the perennial production of its fruits and a high oil concentration on its seeds. The mechanical extraction of the oil yielded 38% while the chemical extraction yielded 44.8% but the oil chemically extracted presented a higher acidity index, in relation to the mechanical extracted oil, factor that interferes in the tran...
Autoxidação de ésteres metílicos de ácidos graxos: estudo teórico-experimental
Albuquerque, Anderson dos ReisIn this work, computational chemistry calculations and thermal analysis experiments were performed in order to determine the oxidative stability of four fatty acid methyl esters (stearate, oleate, ricinoleate and linoleate), whose fatty chains may be inserted in oils and biodiesel. In the computational chemistry investigation the sequence of stabilities, based on the dissociation energy of the C-H bond was: C18...
Estudo teórico de complexos de hidrogênio heterocíclicos com enfoque na determi...
Silva, Jefferson José Soares daIn the present work the molecular properties of heterocyclic hydrogen complexes: oxirane (C2H4O), methyloxirane (H3C-C2H3O) and hydroxi-oxirane (HO-C2H3O), as well as the respective ring open reaction by fluoridric acid has been investigated by using quantum chemistry methods. In this way, molecular properties of hydrogen complexes, such as oxirane---HF (C2H4O---HF), methyloxirane---HF (H3C-C2H3O---HF) e hydrox...
Análise termo-oxidativa do biodiesel de girassol (helianthus annuus)
Tavares, Marileide Lira de AraújoThe present work aims at investing the biodiesel obtained from the transesterification of sunflower oil by means of alkaline catalysis using 30% of ethyl alcohol, 1% KOH for each 100g of oil and (1:6) oil/alcohol molar ratio. The overall content of ethyl esters (99.72%) was determined by gas chromatography coupled to mass spectrometer, confirm the efficiency of the purification process carried out after the bio...
Caracterização ambiental e investigação da presença de metais traço na coluna d...
Barros, Sara Regina Ribeiro Carneiro deDue to the intense activity in the textile business Piranhas River, which traverses the city of São Bento-PB is serving as the depletion for the waste generated in the steps of bleaching and dyeing of yarn, since the networks are made by artisans, many them in the backyards of residences. On this context, for this work, we collected water and sediment samples at three different points of the Piranhas, with the ...
Mecanismo da reação de hidrodessulfurização do Tiofeno empregando o Método PM6
Silva, Liana de SousaAir pollution is of great concern to all of us, and among the main causes are the gases emitted from fossil fuels burning. Therefore, the search for clean technologies is of prime importance nowadays. Thus, in the present work the reaction mechanism for the hydrodesulfurization is investigated. Such reaction is widely used in oil refinery, where new materials, with lowest cost and greater range of application, ...
Um novo critério para seleção de variáveis usando o Algoritmo das Projeções Suc...
Soares, Sófacles Figueiredo CarreiroThis study proposes a modification in the Successive Projections Algorithm (SPA), that makes models of Multiple Linear Regression (MLR) more robust in terms of interference. In SPA, subsets of variables are compared based on their root mean square errors for the validation set. By taking into account the statistical prediction error obtained for the calibration set, and dividing by the statistical prediction er...
Um micro flow-batch para determinação fotométrica e turbidimétrica de taninos e...
Lima, Marcelo Batista deThis study proposed a miniaturized flow-batch system for chemical analysis. The technique used microfabricated urethane-acrylate, a commercial polymer. The microsystem was evaluated and optimized by analysis of synthetic dye samples. Afterwards, it was employed for the determination of tannins in tea samples. The tannins are a group of polyphenols of significant relevance in the food industry and pharmaceutical...
Triagem da qualidade de amostras de GNV e GLP usando espectrometria NIR e quimi...
Dantas, Hebertty VieiraThe search for new energy sources and concern about environmental problems has caused an increase in the use of gaseous fuels like natural gas (CNG) and liquefied petroleum gas (LPG). The main advantages of these fuels besides clean energy, are low production and processing costs, high efficiency and versatility. Given these realities, there is both growing need and demand for quality controls applicable to the...