977 resultados para acid-base indicators


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This work presents a study on the production of biodiesel by esterification reaction of oleic acid with methanol using batch reactor and different catalysts based on CeO2 and WO3 and HZSM-5. Acid treatment was performed in order to increase the catalytic activity. Different characterization techniques were performed, among them X-ray diffraction (XRD), Thermogravimetric analysis TGA/DTA, Spectroscopy in the Region in Fourier Transform Infrared (FTIR) and X-ray fluorescence (XRF). The effects of independent variables: temperature, molar ratio of oil: alcohol and the amount of catalyst and their interactions on the dependent variable (conversion of oleic acid to the corresponding ester). Overall, through the results obtained in the characterization was observed that the applied treatments were efficient, however the XRF technique, indicated that tungsten oxide leaching could occur during the preparation of the materials. The treatments performed on HZSM-5 caused no significant changes in the structure indicating that the zeolite was quite resistant to the treatments used. It was evaluated using complete 23 factorial design. For the catalysts investigated, the best reaction conditions were obtained when using higher levels of the independent variables temperature and amount of catalyst. However, for the variable molar ratio the lowest level showed significant yields for most of the synthesized catalyst, obtaining maximum conversion to the OC (67.97%), OW (74.37%), HZSM-5 (61.16%) OC-OW 1 (75.93%), OC-OW 2 (82.57%), OC-OW 3 (79.15%), S/OC-OW 1 (86.90%), S/OC-OW 2 (91.04%), S/OC-OW 3 (88.60%), S/OC-OW/H 1 (92.34%), S/OC-OW/H 2 (100%) and S/OC-OW/H 3 (98.16%). According to the experimental design, the temperature has the biggest influence on the reaction variable for all the synthesized catalysts. Among the catalysts investigated S/OC-OW/H 2 e S/OC-OW/H 3 were more effective. Reuse tests showed that the catalyst activity decreased after each cycle, indicating that the regeneration process was effective. The leaching test indicated that the catalysts are heterogeneous in the evaluated operating range. The catalysts investigated showed themselves promising for the production of biodiesel.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

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Pós-graduação em Química - IBILCE

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Alimentos e Nutrição - FCFAR

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

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Hydrotalcite like compounds (HT) were prepared by co-precipitation (Mg/Al = 3.5), using an acid solution with blast furnace slag and MgCl2.6H2O and aqueous solutions of NaOH. The following synthesis variables were investigated: temperature (30 and 45 ºC) and pH (9 and 12). Depending of the temperature two systems were observed: Mg-Al-CO3 (T = 30 ºC); Mg-Al-Cl-CO3 (T = 45 ºC). An increase in the pH of synthesis and Mg2+ concentration produced HTs well-crystallized and with greater values of all cell parameters. The study showed the potentiality of BFS in the synthesis of well-crystallized LDHs without the presence of other crystalline phases.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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O regime de macromaré e a pororoca controlam a dinâmica estuarina do Araguari, na qual é muito diferente dos modelos tradicionais dos estuários sob este regime de maré. Objetivando estabelecer zonas estuarinas no Araguari com base em assembléias de foraminíferos, tecamebas, palinomorfos e parâmetros físico-químicos, foram estabelecidas dezesseis estações amostrais ao longo do estuário. A turbidez e a temperatura foram os parâmetros ambientais que permitiram determinar gradiente estuarino. Dezoito espécies de foraminíferos, dez espécies de tecamebas e quatorze espécies de palinomorfos foram identificadas. A análise de agrupamento em modo-R mostrou a existência de assembléias de foraminíferos e quatro de palinomorfos. A análise em CCA demonstrou que a turbidez e a matéria orgânica como os parâmetros de maior influência na distribuição dos foraminíferos tecamebas no Araguari. A análise de agrupamento em Modo-Q usando todos os dados formou quarto grupos de estações que sugerem a existência de três zonas estuarinas: Zona I - composta por tecamebas e palinomorfos continentais; Zona II - compostas por foraminíferos de manguezal, acritacos e todas as assembléias de palinomorfos; e Zona III - composta por foraminíferos de manguezal e estuarinos e por todas as assembléias de palinomorfos.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)