Acessibilidade / Reportar erro
Brazilian Journal of Chemical Engineering, Volume: 23, Número: 3, Publicado: 2006
  • Production of aromas and fragrances through microbial oxidation of monoterpenes Biotechnology

    Rozenbaum, H. F.; Patitucci, M. L.; Antunes, O. A. C.; Pereira Jr, N.

    Resumo em Inglês:

    Aromas and fragrances can be obtained through the microbial oxidation of monoterpenes. Many microorganisms can be used to carry out extremely specific conversions using substrates of low commercial value. However, for many species, these substrates are highly toxic, consequently inhibiting their metabolism. In this work, the conversion ability of Aspergillus niger IOC-3913 for terpenic compounds was examined. This species was preselected because of its high resistance to toxic monoterpenic substrates. Though it has been grown in media containing R-limonene (one of the cheapest monoterpenic hydrocarbons, which is widely available on the market), the species has not shown the ability to metabolize it, since biotransformation products were not detected in high resolution gas chromatography analyses. For this reason, other monoterpenes (alpha-pinene, beta-pinene and camphor) were used as substrates. These compounds were shown to be metabolized by the selected strain, producing oxidized compounds. Four reaction systems were used: a) biotransformation in a liquid medium with cells in growth b) with pre-grown cultures c) with cells immobilized in a synthetic polymer network and d) in a solid medium to which the substrate was added via the gas phase. The main biotransformation products were found in all the reaction systems, although the adoption of previously cultivated cells seemed to favor biotransformation. Cell immobilization seemed to be a feasible strategy for alleviating the toxic effect of the substrate. Through mass spectrometry it was possible to identify verbenone and alpha-terpineol as the biotransformation products of alpha-pinene and beta-pinene, respectively. The structures of the other oxidation products are described.
  • Screening of static culture and comparison of batch and continuous culture for the textile dye biological decolorization by Phanerochaete chrysosporium Biotechnology

    Urra, J.; Sepúlveda, L.; Contreras, E.; Palma, C.

    Resumo em Inglês:

    The production of manganese dependent peroxidase (MnP) by Phanerochaete chrysosporium and the level of decolorization of 13 dyes were evaluated using static and agitated batch cultures and continuous cultures. A screening carried out under static conditions showed that the oxidative system has a certain affinity for azoic structures. For concentrations of 100 mg l-1 of Acid Black 1, Reactive Black 5, Reactive Orange 16 and Acid Red 27, decolorization percentages higher than 90% were obtained. In batch cultures with Acid Black 1 and Reactive Black 5 a significant increment in primary post-metabolism biomass was observed. For these last two dyes, it was possible to explore the response of the continuous system during 32 to 47 days, with concentrations between 25 to 400 mg l-1, obtaining decolorization percentages greater than 70% for 400 mg l-1.
  • Review- Alternatives for the separation of drug enantiomers: ibuprofen as a model compound Biotechnology

    Carvalho, P. O.; Cass, Q. B.; Calafatti, S. A.; Contesini, F. J.; Bizaco, R.

    Resumo em Inglês:

    Given the inherent dangers associated with racemic pharmaceuticals, exhaustive studies of techniques designed to separate enantiomers have been conducted. This paper reports a brief review of the different physical, chemical, and enzymatic methods used for the enantiomeric separation of rac-ibuprofen. The possible contribution of each technique to the preparation of enantiomerically pure drugs is reviewed in the context of competitive approaches that depend on the scale of application, with special emphasis on the recent progress achieved in this particular area.
  • A comparison of hyperbolic solvers for ideal and real gas flows Computer And Fluids Engineering

    Coelho, R. M. L.; Lage, P. L. C.; Telles, A. Silva

    Resumo em Inglês:

    Classical and recent numerical schemes for solving hyperbolic conservation laws were analyzed for computational efficiency and application to nonideal gas flows. The Roe-Pike approximate Riemann solver with entropy correction, the Harten second-order scheme and the extension of the Roe-Pike method to second-order by the MUSCL strategy were compared for one-dimensional flows of an ideal gas. These methods require the so-called Roe's average state, which is frequently difficult and sometimes impossible to obtain. Other methods that do not require the average state are best suited for complex equations of state. Of these, the VFRoe, AUSM+ and Hybrid Lax-Friedrich-Lax-Wendroff methods were compared for one-dimensional compressible flows of a Van der Waals gas. All methods were evaluated regarding their accuracy for given mesh sizes and their computational cost for a given solution accuracy. It was shown that, even though they require more floating points and indirect addressing operations per time step, for a given time interval for integration the second-order methods are less-time consuming than the first-order methods for a required accuracy. It was also shown that AUSM+ and VFRoe are the most accurate methods and that AUSM+ is much faster than the others, and is thus recommended for nonideal one-phase gas flows.
  • Activated sludge morphology characterization through an image analysis procedure Environmental Engineering

    Perez, Y. G.; Leite, S. G .F.; Coelho, M. A. Z.

    Resumo em Inglês:

    This work deals with the development of a digital image analysis procedure to characterize microbial flocs obtained in three different WWTP: a bench-scale Sequencing Batch Reactor (SBR) dealing with phenol and nitrogen biological removal, a municipal treatment unit (Ilha do Governador, Rio de Janeiro, Brazil) and an industrial wastewater treatment plant (Ciba - Estrada do Colégio, Rio de Janeiro, Brazil). The developed procedure permits to obtain its morphological parameters like equivalent diameter, compactness, roundness and porosity properties as well as the fractal dimension. This procedure was validated and lead to identify the major relationships between the analysed morphological parameters. A minimum of 300 flocs should be included in the image analysis and a significant influence of the sample dilution step on the mean size of the flocs was verified. The porosity parameter positively correlated with the fractal dimension of microbial aggregates indicating the that highly porous flocs are very irregular.
  • Effects of operating conditions on compositional characteristics and reaction kinetics of liquid derived by delayed coking of nigerian petroleum residue Petroleum Engineering

    Bello, O. O.; Ademodi, B. T.; Macaulay, S. R. A.; Latinwo, G. K.

    Resumo em Inglês:

    The thermal upgrading of Nigerian petroleum residue was studied at relatively low pressure in a delayed coking reactor system. In this work, the intent was to investigate the effects of process variables such as reaction temperature (200(0)C to 600(0)C), reaction time (0 to 120min), additive concentration loading and additive-to-residue ratio on the amounts and quality of organic liquid product (OLP). The liquid products derived from the delayed coking process were characterized by means of instrumental analysis of gas-liquid chromatography. Results obtained from the analyses of the OLP revealed an upward trend of the conversion process and the selectivity of the aromatic compounds with additive-to-residue ratio (ARR) and increase in temperature. This led to maximum yield of 37.2% achieved with ARR of 5 compared to 31% achieved with ordinary thermal conversion. The selectivity for aromatic hydrocarbons was maximum at 83.1wt% the selectivity towards aromatics and aliphatic hydrocarbons were highest for methanol-potassium hydroxide and methanol respectively. In all additive system cases, maximum OLP was produced at an optimum reaction temperature of 370(0)C in the delayed coking reactor and at higher residence time. The gaseous product consisted of carbon monoxide and carbon dioxide and C1 - C6 hydrocarbons, which amounted to about 20 to 30 wt% of liquid distillate. The information obtained in this study show that the organic liquid products are amenable to characterization procedure and provided the basis for the identification of processes for upgrading Nigerian petroleum residue and such other starting materials such as bitumen or fossil fuel coal liquids.
  • Photodecomposition of hydrogen peroxide in highly saline aqueous medium Photodecomposition

    Luna, A. J.; Nascimento, C. A. O.; Chiavone-Filho, O.

    Resumo em Inglês:

    The photodecomposition of hydrogen peroxide was performed in highly saline aqueous medium (60 g.L-1 of NaCl). The Fe3+/H2O2/NaCl/UV system was tested at temperatures from 20 to 50 ºC, while the intervals of concentration of Fe3+ and H2O2 were 1 to 2.5 mM and 230 to 630 mM, respectively. It is known from the literature that chloride is an inhibitor of the oxidation of organic compound in aqueous medium, but this effect has not been observed to be expressive for hydrogen peroxide. Despite this result, experiments were conducted in presence of high concentration of salt (60 g.L-1), emulating the agrochemical process condition. The series of measurements has been evaluated and correlated. Thermal and photochemical dependencies were described satisfactorily by a simplified kinetic model. The apparent activation energy was estimated to be 27.6 kJ.mol-1.
  • Vanadium oxides supported on hydrotalcite-type precursors: the effect of acid-base properties on the oxidation of isopropanol Reactors Engineering And Catalysis

    Meira, D. M.; Cortez, G. G.; Monteiro, W. R.; Rodrigues, J. A. J.

    Resumo em Inglês:

    Vanadium oxide supported on hydrotalcite-type precursors was studied in the oxidation of isopropanol. Hydrotalcites with different y = Mg/Al ratios were synthesized by the method of coprecipitation nitrates of Mg and Al cations with K2CO3 as precipitant. The decomposition of these hydrotalcite precursors at 450°C yielded homogeneous MgyAlOx mixed oxides that contain the Al+3 cations totally incorporated into the MgO framework. The materials were characterized by chemical analysis, BET superficial area, X-ray diffraction, temperature-programmed reduction (TPR) and the reaction of isopropanol, a probe molecule used to evaluate the acid-base properties. The results of TPR showed that the reducibility of V+5 decreased with the increase in magnesium loading in catalysts. The X-ray diffraction patterns of Al-rich hydrotalcite precursors showed the presence of crystalline phases of brucite and gibbsite. It was shown that chemical composition, texture, acid-base properties of the active sites and also Mg/Al ratio strongly affect the formation of the products in the oxidation of isopropanol. The Al-rich catalysts were much more active than the Mg-rich ones, converting isopropanol mainly to propylene.
  • Determination of critical conditions for the esterification of acetic acid with ethanol in the presence of carbon dioxide Thermodynamics

    Platt, G. M.; Henderson, N.; de Medeiros, J. L.

    Resumo em Inglês:

    In this work, we present the calculation of critical coordinates for the esterification of acetic acid with ethanol in compressed carbon dioxide. Determination of the critical pressure for this system is useful, since the conversion of this reaction increases with pressure in the two-phase region, reaching a maximum at the critical point. We used a calculation framework based on a coordinate transformation for molar fractions, producing a new compositional domain. For a system with five components (acetic acid + ethanol + ethyl acetate + water + carbon dioxide) and one equilibrium reaction, the compositional domain is entirely described by three independent transformed coordinates. The results obtained were compared with experimental observations presented in the literature. The results illustrate the capability of the framework used to determine critical coordinates for reactive systems, and thus its usefulness as a tool for pressure tuning for this esterification reaction in compressed carbon dioxide.
  • Liquid - liquid equilibria of the water + butyric acid + decanol ternary system Thermodynamics

    Kirbaslar, S.I.

    Resumo em Inglês:

    Liquid-liquid equilibrium (LLE) data for the water + butyric acid + decanol ternary system were determined experimentally at temperatures of 298.15, 308.15 and 318.15 K. Complete phase diagrams were obtained by determining the solubility curve and the tie lines. The reliability of the experimental tie line data was confirmed with the Othmer-Tobias correlation. The UNIFAC method was used to predict the phase equilibrium of the system using the interaction parameters for groups CH3, CH2, COOH, OH and H2O determined experimentally. Distribution coefficients and separation factors were evaluated for the immiscibility region.
  • Supercritical extraction of carqueja essential oil: experiments and modeling Thermodynamics

    Vargas, R. M. F.; Cassel, E.; Gomes, G. M. F.; Longhi, L. G. S.; Atti-Serafini, L.; Atti-Santos, A. C.

    Resumo em Inglês:

    Baccharis trimera is a native Brazilian plant which has medicinal properties. In this work a method of supercritical extraction was studied to obtain the popularly essential oil from Baccharis trimera, known as carqueja. The aim was to obtain experimental data and to compare two mathematical models used in the simulation of carqueja (Baccharis trimera) oil extraction by supercritical CO2. The two mathematical models are based on mass transfer. One of the models, proposed by Reverchon, is solved numerically and requires two adjustable parameters from the experimental data. The other model chosen is the one proposed by Sovová. This model is solved analytically and requires four adjustable parameters. Numerical results are presented and discussed for the adjusted parameters. The experimental results are obtained in a temperature range of 313.15 K to 343.15 K at 90 bar. The extraction yield of carqueja essential oil using supercritical carbon dioxide ranged between 1.72 % (w/w) at 323.15 K and 2.34 % (w/w) at 343.15 K, 90 bar with a CO2 flow rate of 3.34.10-8 m³/s for a 0.0015 kg sample of Baccharis trimera.
  • Modification of Sako-Wu-Prausnitz equation of state for fluid phase equilibria in polyethylene-ethylene systems at high pressures Thermodynamics

    Gharagheizi, F.; Mehrpooya, M.; Vatani, A.

    Resumo em Inglês:

    In order to model phase equilibria at all pressures, it is necessary to have an equation of state. We have chosen the Sako-Wu-Prausnitz cubic equation of state, which had shown some promising results. However, in order to satisfy our demands, we had to modify it slightly and fit new pure component parameters. New pure component parameters have been determined for ethylene and the n-alkane series, using vapor pressure data, saturated liquid volume and one-phase PVT-data. For higher n-alkanes, where vapor pressure data are poor or not available, determination of the pure component parameters was made in part by extrapolation and in part by fitting to one-phase PVT-data. Using one-fluid van der Waals mixing rules, with one adjustable interaction parameter, good correlation of binary hydrocarbon system was obtained, except for the critical region. The extension of the equation of state to polyethylene systems is covered in this work. Using the determined parameters, flash and cloud point calculations were performed, and treating the polymer as polydisperse. The results fit data well.
  • Development of a robust algorithm to compute reactive azeotropes Thermodynamics

    Reis, M. H. M.; Mascolo, L. F. S.; Wolf-Maciel, M. R.

    Resumo em Inglês:

    In this paper, a novel approach for establishing the route for process intensification through the application of two developed softwares to characterize reactive mixtures is presented. A robust algorithm was developed to build up reactive phase diagrams and to predict the existence and the location of reactive azeotropes. The proposed algorithm does not depend on initial estimates and is able to compute all reactive azeotropes present in the mixture. It also allows verifying if there are no azeotropes, which are the major troubles in this kind of programming. An additional software was developed in order to calculate reactive residue curve maps. Results obtained with the developed program were compared with the published in the literature for several mixtures, showing the efficiency and robustness of the developed softwares.
  • Phase behavior of olive and soybean oils in compressed propane and n-butane Thermodynamics

    Ndiaye, P. M.; Lanza, M.; Tavares, F. W.; Dariva, C.; Oliveira, D.; Vladimir Oliveira, J.

    Resumo em Inglês:

    The aim of this work is to report the experimental data and thermodynamic modeling of phase equilibrium of binary systems containing soybean and olive oils with propane and n-butane. Phase equilibrium experiments were carried out using the static synthetic method in a high-pressure variable-volume view cell in the temperature range from 30 to 70ºC and varying the solvent overall composition from 5 to 98 wt%. Vapor-liquid, liquid-liquid and vapor-liquid-liquid phase transitions were observed at relatively low pressures. The Peng-Robinson and the SAFT equations of state without any binary interaction parameters were employed in an attempt at representing the phase behavior of the systems. Results show the satisfactory performance of SAFT-EoS in predicting qualitatively all phase transitions reported in this work.
  • Modeling and simulation of rapid expansion of supercritical solutions Thermodynamics

    Corazza, M. L.; Cardozo Filho, L.; Dariva, C.

    Resumo em Inglês:

    Rapid expansion of supercritical solution (RESS) is a promising technique for microparticle production. The literature points out that the RESS technique can be applied to process a wide range of materials including ceramics, polymers, biopolymers, pharmaceutics, and organic compounds. In order to achieve an adequate understanding of the RESS process, it is necessary to conduct more comprehensive studies involving the hydrodynamic modeling of the fluid flow through the capillary, the phase behavior of a expanding mixture, and also with regard to the microparticle formation mechanism. In this context, this work is focused on the analysis of process hydrodynamic modeling and on phase equilibrium modeling (thermodynamic modeling of supersaturation), with a phase stability test coupled. The Gibbs tangent plane distance for the phase stability test was minimized using the simulated annealing algorithm. The results showed that the thermodynamic variables exert a remarkable effect simulated variables (temperature, velocity, density and degree of supersaturation) for the profile.
  • A reduction method for phase equilibrium calculations with cubic equations of state Thermodynamics

    Nichita, D. V.

    Resumo em Inglês:

    In this work we propose a new reduction method for phase equilibrium calculations using a general form of cubic equations of state (CEOS). The energy term in the CEOS is a quadratic form, which is diagonalized by applying a linear transformation. The number of the reduction parameters is related to the rank of the matrix C with elements (1-Cij), where Cij denotes the binary interaction parameters (BIPs). The dimensionality of the problem depends only on the number of reduction parameters, and is independent of the number of components in the mixture.
Brazilian Society of Chemical Engineering Rua Líbero Badaró, 152 , 11. and., 01008-903 São Paulo SP Brazil, Tel.: +55 11 3107-8747, Fax.: +55 11 3104-4649, Fax: +55 11 3104-4649 - São Paulo - SP - Brazil
E-mail: rgiudici@usp.br