Teses em Química (Doutorado) - PPGQ/ICEN

URI Permanente para esta coleçãohttps://repositorio.ufpa.br/handle/2011/4047

O Doutorado Acadêmico pertence ao Programa de Pós-Graduação em Química (PPGQ) do Instituto de Ciências Exatas e Naturais (ICEN) da Universidade Federal do Pará (UFPA).

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Navegando Teses em Química (Doutorado) - PPGQ/ICEN por Assunto "Biodiesel"

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    Produção de biodiesel metílico e etílico de oleaginosas Amazônicas: caracterização físico-química e estudos térmico e cinético
    (Universidade Federal do Pará, 2016-01-29) LIMA, Rogério Pereira; ROCHA FILHO, Geraldo Narciso da; http://lattes.cnpq.br/7580236895339455
    This study aimed to synthesize methyl and ethyl biodiesel from six amazonian species of vegetable oils and fat through the transesterification reaction process using alkaline homogeneous catalysis, determine the heat capacity values of oils and methyl and ethyl biodiesel by differential scanning calorimetry (DSC) in the temperature range of 55 to 195°C, and correlate with information estimated by the group contribution method, to investigate the thermal stability of oils and biodiesel produced by thermogravimetric analysis (TG/DTG) and perform kinetic study of the decomposition thermal of biodiesels using the Ozawa method. Classic physicochemical analysis for the characterization the vegetable oils and the biodiesel synthesized samples were used. The results for the physicochemical properties of methyl biodiesel samples were consistent with the values specified by the Resolution No. 45 of 2014 of the National Agency of Petroleum, Natural Gas and Biofuels (RANP 45/14). The results of heat capacity determined by DSC showed that the methyl biodiesel pracaxi showed the highest values, while for ethyl, it was observed for the biodiesel buriti, andiroba and pracaxi. Most heat capacity data obtained for the methyl and ethyl biodiesel determined by DSC and by the group contribution method were satisfactory, as they showed smaller relative deviations or equal to 15% and showed good correlation coefficients ranged from 0, 8617 to 0.9947. The studies on the thermal stability by thermogravimetric analysis indicated that the oils and fat were stable in the temperature range of 110 to 220°C, in inert atmosphere and, in an oxidizing atmosphere, were thermally stable to 130 at 165°C. All the synthesized biodiesel samples is degraded at temperatures up to 150°C, which is highly volatile, a very important feature for the application in diesel engines. The kinetic study of the thermal decomposition of the methyl and ethyl biodiesel met activation energy values ranging from the 46.23 124.93 kJ.mol-1 and showed that the ethyl biodiesel were more stable than the methyl biodiesel.
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    ItemAcesso aberto (Open Access)
    Técnicas voltamétricas com eletrodo de filme de bismuto modificado com edta e ebt para determinação de Ca2+ e Mg2+ em biodiesel
    (Universidade Federal do Pará, 2016-08-19) MULLER, Renata Medeiros Lobo; MARQUES, Aldalea Lopes Brandes; http://lattes.cnpq.br/0121030502015990; MÜLLER, Regina Celi Sarkis; http://lattes.cnpq.br/654941494386147
    This study presents the development of alternative electrochemical methods for the determination of Mg2+ and Ca2+ through voltammetry technique of adsorptive stripping voltammetry (VAdR) with anodic scan. Bismuth film electrode modified with eriochrome black-T (EBT) was used for modification of the electrode in the determination of Mg2+ in the pulse differential mode (DPAdSV), while EDTA has been used for determination of Ca2+ in wave mode square (SWAdSV). The determination of Mg2+ was performed using acetate buffer (0.1 mol L-1) at pH = 4.5, EBT as supporting electrolyte and 1.0 x 10-3 mol L-1 as a binder. Successive additions of aliquots of the stock solution were made Mg2+ 1.0 x 10-3 mol L-1 so that the ion was pre-concentrated on the sensor surface under the following conditions optimized voltammetric: deposition potential (EDEP) = - 1.0 V; Pre time - concentration (Tpre) = 120 s; scan speed (v) = 0.050 V s-1; pulse amplitude (Amp) = 0.1 V. The complex formed Mg2+ EBT showed a peak current of about - 0.6 V. The determination of Ca2+ was made using ammonium buffer (0.01 mol L-1) at pH 9.4, as supporting electrolyte and EDTA 1.0 x 10-2 mol L-1 as a binder under the following optimum conditions: deposition potential (EDEP) = -1.0 V; preconcentration time (Tpre) = 90 sec; frequency (freq.) = 15 Hz; width = 0,075V and Step E) = 0.004 V. The complex formed Ca2+ EDTA showed a peak current of approximately - 0.2 V. The result was consistent statistically considering t -test for a 95% confidence level. The levels were lower CV of 11.0% (Mg2+ and Ca2+), recoveries were in the range 95.0 to 108.0% (Mg2+) and from 97.8 to 105.0% (Ca2+) and the values of detection limits were 1.05 x 10-6 mol L-1 (Mg2+) and 2.8 x 10-7 mol L-1 (Ca2+), and quantitation 3.51 x 10-6 mol L-1 (Mg2+) and 9.46 x 10-7 mol L-1 (Ca2+) for the samples analyzed, showing good accuracy and sensitivity of the proposed method. The values obtained for the samples ranged from 1.47 x 10-5 ± 1.28 x 10-6 mol L-1 (Mg2+) and 5.57 x 10-6 ± 3.77 x 10-7 mol L-1 (Ca2+) on samples of biodiesel. The determination of metals such as Ca2+ and Mg2+ by electrochemical techniques with chemically modified electrodes has as main advantages its detectability and the selectivity.
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