João Fernandes de Sousa

Niobium carbide synthesis by solid-gas reaction using a rotating cylinder reactor

A rotating cylinder reactor was designed for the synthesis of niobium carbide powders at 1173 K. Niobium carbide, NbC, was prepared by carbothermal reduction starting from commercial niobium pentoxide powders. The reactor was heated using a custom-made, two-part, hinged, electric furnace with programmable temperature control. The design and operational details of the reactor are presented. The longitudinal temperature gradient inside the reactor was determined. Total reaction time was monitored by a gas chromatograph equipped with an FID detector for determination of methane concentrations. The results show that time of reaction depended on rotation speed. NbC was also prepared in a static-bed alumina reactor using the same conditions as in the previous case. The niobium carbide powders were characterized by X-ray diffraction and compared with commercially available products. Morphological, particle size distribution and surface area analyses were obtained using SEM, LDPS and BET, respectively. Therefore, the present study offers a significant technological contribution to the synthesis of NbC powders in a rotating cylinder reactor.

Characteristics of Bio-oil from the Fast Pyrolysis of Elephant Grass (Pennisetum purpureum Schumach) in a Fluidized Bed Reactor

Bio-oil was obtained from the fast pyrolysis of elephant grass in a semi-pilot scale pyrolysis plant equipped with a 40 kg/h fluidized bed reactor. The temperature varied between 480 and 520°C. The biomass (moisture of 10%) was fed with a rate between 20 and 35 kg/h. Approximately 4.5 kg of sand was used as fluidizing agent. The pyrolytic oil was analyzed for the contents of carbon, hydrogen and nitrogen and sulfur. Water content, acidity, pH, viscosity at 40°C, density and higher heating value were also determined. Chromatographic analysis showed that it was composed mostly of acetic acid, syringol, vinyl-phenol, guaiacol and hexanoic acid. Main results are used to compare the influence of different configurations of a gas-washing column and vapor condensation system on the properties of the bio-oil. Original Research Article Sousa et al.; ACSJ, 14(2): 1-10, 2016; Article no.ACSJ.25843 2

Síntesis y Refinado por el Método Rietveld de la fase perovsquita obtenida a partir del Método de Co-precipitación vía Oxalato

Powders of perovskite SrCo0.8Fe0.2O3-δ were synthesized using oxalate co-precipitation method. According to the thermal gravimetry and differential thermal analysis (TG/DTA), total mass loss was 40 % corresponding to three different steps and the precipitant agent as well the starting chemical elements have no influence on the process. Perovskite phase was identified by x-ray diffraction and the average crystallite size was 77.22 nm using iron nitrate (III) as starting material while 42.23 nm were obtained using iron oxalate (III). Ammonium oxalate and equimolar mixtures of ammonium oxalate and oxalic acid were used as precipitant agents and the results shown that these reactants have no influence on the average crystallite size (42.95 nm and 42.23 nm). The material presents isotherms of type II, with especific surface of approximately 4,41m 2 g -1 .

SIMULAÇÃO SINTÉTICA DO EFEITO DO METABISSULFITO DE SÓDIO NO DESPRENDIMENTO DO OXIGÊNIO DISSOLVIDO EM ÁGUAS

In shrimp culture, sodium metabissulfite is used for the preservation after the harvest. However, large parts are discarded in an irregular manner directly to mangrove swamps and other receptors biotopes. Amongst others, this substance acts by provoking desorption of oxygen, leading to severe damage of the ecosystem. We developed an experimental method to study desorption and consumption kinetics of dissolved oxygen using oxygen saturated distilled water as a reference for maximum saturation. The influence of sodium metabissulfite concentration and temperature were examined. Monitoring was accomplished by a digital oxymeter. Our results were adjusted to a firstorder rate law to obtain the rates of oxygen desorption under the given conditions (yielding heat for the deoxygenating system in question as 11.39 kJ/mol). These results should contribute to widen the JERONIMO et al., v(7), no 7, p. 1261-1271, MAR-AGO, 2012. Rev. Elet. em Gestao, Educacao e Tecnologia Ambiental (e-ISSN: 2236-1170) http://cascavel.ufsm.br/revistas/ojs-2.2.2/index.php/reget/index 1262 knowledge of ambiental factors envolved in shrimp culture and should provide evidence for the effects caused in nature by the given contaminations.

Modelado Cinético y Evaluación de Catalizadores Mo2C, Mo2N y Ni-Mo/C en la Reacción de Hidrogenación de Lactosa

Resumen El objetivo de este estudio fue evaluar los catalizadores Mo 2 C, Mo 2 N y Ni-Mo/C en la hidrogenacion catalitica de lactosa para obtencion de lactitol. Los experimentos de hidrogenacion se realizaron en autoclave agitada mecanicamente a 500 rpm, 120 °C y 68 atm, utilizando una solucion de lactosa comercial, solucion de suero de queso bruto y solucion de suero de queso tras adsorcion de proteinas y de iones cloruros. El contenido de proteinas y de iones cloruros disminuyo, mediante coagulacion con quitosana y desmineralizacion por cambio ionico, respectivamente. Ademas, se hicieron pruebas modificando el pH, en medio acido (3.5) y basico (8). El mejor rendimiento en lactitol fue del 46% con Mo 2 C a pH 8. Los resultados obtenidos en los experimentos de hidrogenacion se modelaron usando la cinetica de Langmuir-Hinshelwoold. Los resultados experimentales de concentracion de lactosa y lactitol concuerdan razonablemente bien con los previstos por el modelo. Palabras clave: modelado cinetico, catalizadores, hidrogenacion, lactosa, quitosana