RCAAP Repository

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

The city of Uberlândia is one of the most populous of Minas Gerais State, and has the second greatest fleet of motor-vehicles of the State. The motor-vehicles are responsible for a great amount of pollutants emitted to the atmosphere. The vehicular pollution added to the diverse sources of existing pollutants, including from industries, speeds up the concern with possible damages to human health and to environment, came from the aggrievement of this problem. By the period of 2003 to 2006, samplings of particle material in suspension were made using great volume samplers, in order to collect total particles (PTS), inhalable particles (MP10), and a sampler of small volumes collecting even more fine particles (MP2,5). The work envisioned getting the scenario of suspended particle material concentration and the and the elemental chemical characterization of the atmospheric air of Uberlândia. For PTS, the annual secondary standards of concentration, available in CONAMA 003/90 Resolution, were surpassed in the whole period of study. The primary standard were surpassed in 2004 and 2005. In the case of inhalable particles, the annual standard was surpassed in 2004. The international standards to the even more fine particles (MP2,5), was not surpassed in none of the occasions in the period of July/06 to June/07. In order to analyse the temporal behaviour of the particle material MP10 and PTS, one used semivariogram models in determining the reach of temporal dependence among data and models of temporal series were used to estimate values of the PTS and MP10 concentration variables in the period from January to June/2007. In the study of series decomposition, one realized the presence of sazonal and of tendency components. Among the temporal series models studied, the one which better represented the behaviour of the series, as for the PTS as for the MP10, was the SARIMA model. The MP10 s filters were analysed by a thermal plasma, induced with optical emission spectrometry (ICP-OES), and the elements which pointed out were Al, Ca, K, Zn and S. The re-suspension of the soil, the vehicular and industry pollution are generating sources of these chemical elements and are part of the region studied. One also made a multivaried analyses of composition data using the technique of the main components, and two of the main components explained the results in more than 86%.

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Fundação de Amparo a Pesquisa do Estado de Minas Gerais

Catalytic reforming of hydrocarbons or other organic species is a technology usually employed in either improving traditional energy sources or producing alternative energy sources. Amongst the technologies employed in improving traditional energy sources, one can include catalytic reforming of petrochemical naphtha. Although being also employed to produce hydrogen, the main goal of this reforming is to transform naphthenic compounds and paraffins in branched-chain isoparaffins and aromatic compounds, used to produce polymers and to increase gasoline octane rating. When the reforming processes are applied to produce alternative energy sources, attention has mostly been given to hydrogen production. Hydrogen is mainly produced from non-renewable fossil fuels, especially by means of steam catalytic reforming of methane, main component of natural gas, and in refineries, through oxidative reforming of higher hydrocarbons. More recently, hydrogen production from catalytic reforming of ethanol has also been studied. It has the advantage of reduced carbon dioxide emission, easiness of storage and distribution of ethanol and a higher yield of hydrogen. The composition of the reformate is very dependent on the variables involved in the process, such as pressure, temperature and reactant feed ratios. The effect of these variables can be studied by means of definition and analysis of some performance parameters such as conversion, yield, selectivity, coke deposition and others. Usually, the first step for this type of investigation is the accomplishment of a thermodynamic analysis for each process through methods of Gibbs free energy minimization. These methods result in non-linear algebraic equation systems, solved numerically with the aid of appropriated software. In this work, a Lagrange Multipliers method based thermodynamic analysis is conducted for the oxidative and autothermal reforming of methane; steam, dry, oxidative and autothermal reforming of ethanol; and naphtha reforming. The main goals of this work are to determine the linearly independent reactions which represent the chemical equilibrium of each reforming system and to foresee the best conditions in which each reaction system should be operated to reach specific goals. To validate the simulations, the results are compared with experimental and simulation data specific of chemical equilibrium. The set of linearly independent reactions of each reforming system was determined and validated through mole balances for each species involved in the process. Ethanol reforming systems showed higher hydrogen yields compared to those of methane reforming. Among all methane reforming systems, oxidative reforming showed the higher yield, with a value of 200%, for a temperature of 1273 K, atmospheric pressure, without feeding oxygen. For ethanol reforming systems, the higher hydrogen yield, with a value of 479%, was obtained for steam reforming in a temperature of 1110 K, 1 atm of pressure and H2O/C2H5OH feed ratio equal to 6. Among the methane reforming systems, autothermal reforming deposited the lesser amount of coke (0,03 moles). Concerning the ethanol reforming systems, autothermal reforming also deposited the lesser amount of coke, with a value of 0,02 moles. For naphtha reforming, it was verified that hydrogen and methane are the most abundant species constituting the reformate. Carbon formation increased a lot when increasing the operational temperature, but it was possible to decrease it in the same magnitude increasing the operational pressure and the H2/Naphtha feed ratio. To increase the aromatics yield, it was necessary to raise both the temperature and the pressure. The resolution of the non-linear algebraic equation systems was carried out with the open-source software Scilab.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Catalysts containing 1.5% (wt) of Pt supported in Nb2O5, LaCoO3, ZrO2, CeZrO2 e CeZrO2-M mesoporous were prepared and characterized using the following techniques: temperature programmed reduction (TPR), x-ray diffraction (XRD) and temperature programmed desorption of CO2 e CO chemisorbed at room temperature after reduction at 500ºC under H2 flow. The catalysts were analyzed by partial oxidation and reforming of methane reactions with CO2 and H2O, at same temperature (800ºC), pression (1 atm) and space velocity (180000 h-1). The results showed that the magnitude of conversion of methane during partial oxidation reaction decreased in the following order: Pt/CeZrO2 > Pt/CeZrO2-M > Pt/ZrO2 > Pt/LaCoO3 > Pt/Nb2O5 &#8776 0. Such results were in accordance with the evolution of existing redox/basic sites and with the balance between these sites and metallic interfacial sites. Reducibility of the catalysts follows the same order, except for Pt/LaCoO3, which was more reducible than Pt/ZrO2. A triangular scheme of mechanism, where direct and indirect steps of synthesis gas formation coexist, explains all the existing results, either modifying reactional condition or changing employed catalyst. The result of reforming of methane with CO2 and H2O revealed the following increasing order of activity: Pt/CeZrO2-M > Pt/CeZrO2 > Pt/ZrO2 >>> Pt/LaCoO3, Pt/Nb2O5 &#8776 0. They are coherent with the bifunctional mechanism, where the balance between metallic and redox sites was of key importance to obtain synthesis gas in a ratio H2/CO = 2, as in partial oxidation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

So as to obtain linter from cotton seeds originating from the chemical delinting process, diluted sulfuric acid was used. This was mixed with cotton seeds originating from the ginning process. The need for removal of the linter remaining on the cotton seeds facilitates sewing as this allows for adequate flow, and so avoids an excess of seeds being placed in the same spot during sewing. The delinting process was carried out at the Cotton Tecnologia de Sementes Company obeying the following stages: 1) mixture of sulfuric acid at concentration of 11 to 12% with the seeds covered with linter; 2) transport of material using conveyor buckets to a worm helix which feeds a reactor; 3) reaction of linter with H2SO4 in perforated rotating drum reactor in which the warm air flowing at a temperature of 120°C, while the reaction time is of 1 h and 15 minutes (at this stage the linter comes off the seed tegument or outer husk); 4) the hydrolyzed linter is transported by exhaust (exit) air and separated in a cyclone separator; 5) at the unloading of the cyclone separator the residue is transported by a worm helix and receives sodium hydroxide at 5 % in the proportion of 20 % mass, and so allowing for the partial neutralization of the sulfuric acid. The neutralized linter was transformed in briquettes at the Maeda S.A company (Itumbiara - GO). The screen analysis showed that the average Sauter diameter of the hydrolyzed and neutralized linter was 0,22 and 0,17 mm, respectively. The density of the hydrolized and neutralized linter was 630 kg/m3 and 520 kg/m3, respectively and the briquettes developed had densities of 1480 kg/m3 and 1580 kg/m3, respectively. The neutralized linter briquettes were analyzed chemically and the following results were obtained (dry base): 82,95 % of volatile matter; 16,57 % of fixed carbon; 0,48 % of ashes; 0,25 % of sulfur. The superior and inferior calorific value of the neutralized linter briquettes were (dry base): 17.432 kJ/kg and 16.095 kJ/kg, respectively. The briquettes were burned, the gases were analyzed and calculated the concentration of SO2 (172,4 mg/m3) emitted in the combustion gases of the neutralized linter briquettes. This concentration was inferior to the CONAMA (280 mg/m3) and CETESB (262 mg/m3) parameters which places it within the Brazilian legislation requirements.

The spouted bed has been increasingly used in coating of particles like pills and seeds, due to the excellent mobility of particles in the bed, to the biggest coating uniformity and the simultaneous coating and drying of the particles. The coating improves the physical and chemical properties of the particles. The spouted has advantages as no mechanical moving components, simultaneous coating and drying, possibility of working with a wide range of particles few agglomerates. Therefore, it requires care when used with fragile particles and coatings, which increase the elutriation. In this work experimental data obtained for the soybean's coating in a spouted bed with draft tube conducted by Duarte (2002) were subjected to a detailed statistical analysis to study the influence of the initial distribution of seeds and effect of the operating variables on the final coating distribution. Besides it, two dynamic balance population models were analyzed, both applied to functional characteristics areas of the conical cylindrical spouted bed with draft tube, to predict the population density function and to evaluate the effect of operational variables on the coating uniformity: the model of Liu and Litster (1993-b) applied to a single domain and the model of Wnukowski and Setterwall (1989) applied to two perfectly mixed regions where occur drying and coating of the particles. Both population balance models have been solved through the Coating1.0 code developed in Maple® and the obtained results were validated against the Duarte (2002) data. The single domain model is used as the basis for the parametric sensitivity and elasticity analysis of the spout air flow, atomization air flow, suspension flow and concentration of the suspension for each of the sixteen experiments through the DDASPK.F code. The analyses showed a great influence of the flow of spout air jet and the flow of suspension on the coating's uniformity. The growth takes place mainly at intermediate mass seeds according to a normal distribution, which is not affected by the initial distribution of uncoated seeds. The parametric sensitivity was more pronounced in seeds of intermediate mass, presenting its highest values for the spout flow air, while the elasticity was more pronounced for seeds of small and big masses.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Conselho Nacional de Desenvolvimento Científico e Tecnológico

In this work was studied the immobilization process β-galactosidase from Aspergillus oryzae by adsorption and cross-linking with glutaraldehyde, using as carrier ions-exchangers such as Duolite A-568, Duolite S-761, Dowex Marathon A, Dowex Marathon C and Amberlite 252 Na. Through innitial results, Duolite A-568 was choosed for the continuance of the work. The influence of the enzyme concentration and pH in the immobilization process was studied using a Central Composit Design (CCD) for a fixed time of 12 hours and temperature of 25°C. The optimal conditions for enzyme immobilization were pH 4,5 and galactosidase concentration 16 g/L. In the sequence, was studied the influence of glutaraldehyde concentration as cross-linking reagent and reaction time in the activity and in stability of the immobilized biocalyst, which were of 3,5 g/L and 1,50 h. The residual activity of the immobilized enzyme without cross-linking with glutaraldehyde after 30 uses was 51% as compared with the initial activity, while the enzyme immobilized with cross-linking was 90%. The immobilized enzyme with cross-linking presented higher pH stabilyt pH when compared to that without the referred treatment. The simultaneous influence of pH and temperature on the immobilized enzyme activity was studied through a PCC with the biocalyst produced in the optimized conditions of immobilization process. With the technique response surface it was possible to obtain the optimized pH of 4,1 and temperature of 34°C. The influence of the lactose concentration was studied in the range of 5 to 140 g/L and the Michaelis-Menten model was adjusted to the experimental results, with values of Vm and Km of 0,71 U and 12.07 g/L, respectively. In the study of the influence of the galactose as inhibitor of the lactose hydrolysis, the competitive inhibition model was adjusted to the experimental results and the values of Vm, Km and Ki were 0,77 U, 12,07 g/L and 4,94 g/L respectively.