Resumo em Inglês:

This paper discusses the feasibility of the use of ionic liquids as catalysts in the biodiesel production field, describing some studies already published in the literature on this theme. Ionic liquids are regarded as a new generation of catalysts in the chemical industry, with several uses in different commercial segments. However only a few publications involving this topic can be found in the literature addressing the manufacture of biodiesel from vegetable oils or animal fats. Through the analysis of the data generated in the studies reviewed, it is possible to affirm that ionic liquids present great potential as catalysts for biodiesel production, but there are some challenges to be faced, such as the production of ionic liquids with low cost, easy recovery and with the possibility of reutilization of the catalyst for several cycles.

Resumo em Inglês:

The immobilization of Aspergillus oryzae β-galactosidase was achieved by entrapment in sodium alginate and gelatin and cross-linking with glutaraldehyde. The optimal concentrations of the aforementioned variables in the immobilization process were determined using an orthogonal central composite design with an orthogonal axial value of 1.35313. The concentrations of alginate, gelatin and glutaraldehyde that provided the greatest enzymatic activity were 6.60%, 4.05% and 3.64% (w/v), respectively. The stability of the immobilized enzyme under the optimal conditions was evaluated through daily activity assays. After 25 uses, a 20% decrease in the enzymatic activity was observed, indicating that the immobilization process could be used to produce a stable biocatalyst. This study investigates the influence of lactose and product concentrations on kinetic reaction hydrolysis. The concentration ranges for the studied variables were 10 to 56 g/L for lactose and 0 to 11.5 g/L for glucose and galactose. Only galactose presented a competitive inhibitory effect.

Resumo em Inglês:

The relationship between phenolic content, antioxidant and antiamylolytic activities was investigated in Rhizopus oligosporus-mediated solid-state bioprocessing of pineapple and guava residues. Two different treatments of fruit residues mixed with soy flour (5g of soy flour and 5g of fruit residue; 1g of soy flour and 9g of fruit residue) were inoculated and incubated at 22ºC. Phenol rich extracts (non-concentrated and concentrated 10-fold by boiling) from day 2 and 10 were tested for their ability to inhibit alpha-amylase. In order to correlate the enzymatic inhibition with phenolic-linked antioxidant activity of the extracts, samples were evaluated for total phenolic content and free radical scavenging. Alpha-amylase inhibition was observed for all extracts, concentrated or not, with values ranging from 10.91% to 100% (complete inhibition). A direct correlation between the total phenolic content or the free radical scavenging activity and alpha-amylase inhibition was not found, demonstrating that such an inhibition could be caused by the presence of specific compounds, phenolic or not, rather than by the actual concentration of overall fruit phenolics.

Resumo em Inglês:

Results are presented on the hot water prehydrolysis of sugar cane bagasse for obtaining ethanol by fermentation. The experimental study consisted of the determination of the effect of temperature and time of prehydrolysis on the extraction of hemicelluloses, with the objective of selecting the best operating conditions that lead to increased yield of extraction with a low formation of inhibitors. The study, carried out in a pilot plant scale rotational digester, using a 3² experimental design at temperatures of 150-190ºC and times of 60-90 min, showed that it is possible to perform the hot water prehydrolysis process between 180-190ºC in times of 60-82 min, yielding concentrations of xylose > 35 g/L, furfural < 2.5 g/L, phenols from soluble lignin < 1.5 g/L, and concentrations < 3.0 g/L of hemicelluloses in the cellolignin residue. These parameters of temperature and prehydrolysis time could be used for the study of the later hydrolysis and fermentation stages of ethanol production from sugar cane bagasse.

Resumo em Inglês:

Two microbial lipases from Burkholderia cepacia and Pseudomonas fluorescens were evaluated as catalysts for the enzymatic transesterification of beef tallow with ethanol and the most efficient lipase source was selected by taking into account the properties of the product to be used as fuel. Both lipases were immobilized on an epoxy silica-polyvinyl alcohol composite by covalent immobilization and used to perform the reactions under the following operational conditions: beef tallow-to-ethanol molar ratio of 1:9, 45ºC and 400 units of enzymatic activity per gram of fat. Products, characterized using Fourier Transform Infrared spectroscopy (FTIR), viscosimetry, thermogravimetry and ¹H NMR spectroscopy, suggested that the biodiesel sample obtained in the reaction catalyzed by Burkholderia cepacia lipase has the best set of properties for fuel usage.

Resumo em Inglês:

β-Fructofuranosidase production by Aspergillus oryzae IPT301 was maximized in shake flasks. Response Surface Methodology (RSM) involving Small Central Composite Design was adopted to evaluate the fructosyltransferase (FTase) activity by changing three medium component concentrations: sucrose, urea and yeast extract. The optimal set of conditions for maximum fructosyltransferase production was as follows: sucrose 320.5 g/L, urea 7.13 g/L and yeast extract 2.11 g/L. In this optimal condition, the following improvements were achieved: an increase of 48.8% in cell growth, 112% and 62% in micelial and free FTase activities, respectively, 62.8% in the ratio of fructosyltransferase/hydrolytic activities for enzyme linked to mycelium and 67.5% for free enzyme.

Resumo em Inglês:

The objective of this work was to investigate, on a flask scale, the production of bioemulsifiers by Yarrowia lipolytica in the presence of sea water, supplemented with nitrogen and phosphate sources, using diesel oil as substrate. A full 2(4) factorial design was conducted to investigate the effects and interactions of the nutrient concentrations (diesel oil, urea, ammonium sulfate and monobasic potassium phosphate) on the response variables: emulsification activity and surface tension of the cell-free cultures. High emulsification activities (> 5,4 UEA) were determined after 168 h in all the experiments. The interactions among diesel oil, urea and monobasic potassium phosphate favored the emulsification with statistical significance. A correlation between the increase of emulsification activity and the reduction of surface tension was not identified.

Resumo em Inglês:

The properties of a milk clotting enzyme (MCE) produced by bacteria (Bacillus licheniformis 5A5) were investigated and compared to those of rennet extracted from a plant (Aloe variegata). Production of MCE by B. licheniformis 5A5 was better in static than in shaken cultures. Maximum activity (98.3 and 160.3 U/ml) of clotting was obtained at 75ºC and 80ºC with bacterial and plant rennet, respectively. In the absence of substrate, the clotting activity of Aloe MCE was found to be less sensitive to heat inactivation up to 80ºC for 75 min, retaining 63.8% of its activity, while bacterial MCE was completely inhibited. CaCl2 stimulated milk clotting activity (MCA) up to 2% and 1.5% for bacterial and plant enzymes. NaCl inhibited MCA for both enzymes, even at low concentration (1%). Plant MCE was more sensitive to NaCl at 3% concentration it retained 30.2% of its activity, whereas bacterial MCE retained 64.1%. Increasing skim milk concentration caused a significant increase in MCA up to 6% for both enzymes. Mn2+ stimulated the activity of bacterial and plant enzymes to 158.6 and 177.9%, respectively. EDTA and PMSF increased the activity of plant MCE by 34.4 and 41.1%, respectively, which is higher than those for the bacterial MCE (19.1 and 20.9%). Some natural materials activated MCE, the highest activation of bacterial MCE (128.1%) was obtained in the presence of Fenugreek (with acid extraction). However Lupine Giza 1 (with neutral extraction) gave the highest activation of plant MCE (137.9%). All extracts from Neem plant increased MCA at range from 105.6% to 136.4%. Plant MCE exhibited much better stability when stored at room temperature (25-30ºC) for 30 days, retaining 51.2% of its activity. Bacterial MCE was highly stabile when stored under freezing (-18ºC), retaining 100% of its activity after 30 days. Moreover, bacterial MCE was highly tolerant to repeated freezing and thawing without loss of activity for 8 months.

Resumo em Inglês:

The aim of this research was to evaluate the bioremediation of a soil contaminated with wastes from a plasticizers industry, located in São Paulo, Brazil. A 100-kg soil sample containing alcohols, adipates and phthalates was treated in an aerobic slurry-phase reactor using indigenous and acclimated microorganisms from the sludge of a wastewater treatment plant of the plasticizers industry (11gVSS kg-1 dry soil), during 120 days. The soil pH and temperature were not corrected during bioremediation; soil humidity was corrected weekly to maintain 40%. The biodegradation of the pollutants followed first-order kinetics; the removal efficiencies were above 61% and, among the analyzed plasticizers, adipate was removed to below the detection limit. Biological molecular analysis during bioremediation revealed a significant change in the dominant populations initially present in the reactor.

Resumo em Inglês:

The objective of this research was to study phenol degradation in anaerobic fluidized bed reactors (AFBR) packed with polymeric particulate supports (polystyrene - PS, polyethylene terephthalate - PET, and polyvinyl chloride - PVC). The reactors were operated with a hydraulic retention time (HRT) of 24 h. The influent phenol concentration in the AFBR varied from 100 to 400 mg L-1, resulting in phenol removal efficiencies of ~100%. The formation of extracellular polymeric substances yielded better results with the PVC particles; however, deformations in these particles proved detrimental to reactor operation. PS was found to be the best support for biomass attachment in an AFBR for phenol removal. The AFBR loaded with PS was operated to analyze the performance and stability for phenol removal at feed concentrations ranging from 50 to 500 mg L-1. The phenol removal efficiency ranged from 90-100%.

Resumo em Inglês:

A Pease-Anthony Venturi scrubber is a gas cleaning device that uses liquid, injected in the equipment as jets, to remove contaminants from the gas. The liquid jet is atomized into droplets, which are dispersed throughout the equipment due to the turbulence. The performance of the scrubber is affected by the spatial distribution of the droplets. Although CFD models have been used to predict the droplet dispersion, these models are expensive. Alternatively, the concept of "jet spreading angle" could be used as a simple and quick way to estimate droplet dispersion. The purpose of this paper is to measure the spreading angle of jets transversally injected into the throat of a Venturi scrubber and correlate it with both gas and jet velocities. The throat gas velocities varied between 59 and 74 m/s and the jet velocity between 3.18 and 19.1 m/s. The angles were measured through image analysis, obtained with high velocity photography. The spreading angle was found to be strongly dependent on jet velocity.

Resumo em Inglês:

A simple analytical model is presented for the time-evolution of dissolved CO2 concentration in a batch water column. The application in mind is the removal of the CO2 produced by the propulsion plant of a submarine cruising underwater. The model is based on a constant number of constant size CO2 bubbles within the water column, with uniform gas injection through a porous membrane at the bottom, and bubbles flowing upwards by their own buoyancy through a short water column (the exhaust gas is recirculated). Analytical results are validated with experimental data found in the literature and the advantages of this simple analytical model pinpointed.

Resumo em Inglês:

Molecular modeling is growing as a research tool in Chemical Engineering studies, as can be seen by a simple research on the latest publications in the field. Molecular investigations retrieve information on properties often accessible only by expensive and time-consuming experimental techniques, such as those involved in the study of radical-based chain reactions. In this work, different quantum chemical techniques were used to study phenol oxidation by hydroxyl radicals in Advanced Oxidation Processes used for wastewater treatment. The results obtained by applying a DFT-based model showed good agreement with experimental values available, as well as qualitative insights into the mechanism of the overall reaction chain. Solvation models were also tried, but were found to be limited for this reaction system within the considered theoretical level without further parameterization.

Resumo em Inglês:

Nanophase (Ce, Zr, Pr)O2-doped alumina coatings were prepared by impregnating the cordierite ceramic honeycomb in the sol or in the slurry of already calcined powder, respectively. The effects of preparation methods on the crystal phase, texture, oxygen storage capacity (OSC), reducibility, surface morphology and thermal stability of coatings were investigated by X-ray diffraction (XRD), the Brunauer Emmet Teller (BET) method, the oxygen pulsing technique, H2-temperature-programmed reduction (H2-TPR) and scanning electron microscopy (SEM). These nanophase (Ce, Zr, Pr)O2-doped alumina coatings were used as supports to prepare Pd-only three-way catalysts, and evaluated with respect to catalytic activities. The results indicate that the nanophase (Ce, Zr, Pr)O2-doped alumina coatings prepared by the two methods have high thermal stability. However, the coating derived from the sol shows better crystalline structure, texture, reducibility and oxygen storage capacity than the coating derived from the slurry. SEM observation shows that the morphology of the coating derived from the sol is uniform and smooth. The Pd-only catalyst derived from the sol exhibits high three-way catalytic activity at low temperature and thermal stability, suggesting a great potential for applications.

Resumo em Inglês:

A three-phase reactor model for describing the hydrotreating reactions of bitumen-derived gas oil was developed. The model incorporates the mass-transfer resistance at the gas-liquid and liquid-solid interfaces and a kinetic rate expression based on a Langmuir-Hinshelwood-type model. We derived three correlations for determining the solubility of hydrogen (H2), hydrogen sulfide (H2S) and ammonia (NH3) in hydrocarbon mixtures and the calculation of the catalyst effectiveness factor was included. Experimental data taken from the literature were used to determine the kinetic parameters (stoichiometric coefficients, reaction orders, reaction rate and adsorption constants for hydrodesulfuration (HDS) and hydrodenitrogenation (HDN)) and to validate the model under various operating conditions. Finally, we studied the effect of operating conditions such as pressure, temperature, LHSV, H2/feed ratio and the inhibiting effect of H2S on HDS and NH3 on HDN.

Resumo em Inglês:

Calcium phosphate (CaP) nanoshells were prepared using negatively charged liposomes (1,2-dioleoyl-sn-glycero-3-phosphate sodium salt (DOPA)) as a template by base titration synthesis at various concentrations of NaOH and calcium ions. The elemental composition, morphology, particle size, particle size distribution and zeta potential of the products were determined via various characterisation techniques, such as energy-dispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), laser Doppler velocimetry (LDV) and Fourier transform infrared spectroscopy (FTIR). The best results showed that stable spherical CaP nanoshells with a mean particle size of 197.5 ± 5.8 nm and a zeta potential of -34.5 ± 0.6 mV were successfully formed when 0.100 M sodium hydroxide (NaOH) and 0.100 M calcium ions were used. Moreover, an optimal pH of 10.52 and a final Ca/P molar ratio of 0.97 were achieved under these conditions.

Resumo em Inglês:

The combined effects of Navier slip and Newtonian heating on an unsteady hydromagnetic boundary layer stagnation point flow towards a flat plate in the presence of a magnetic field are studied. The self-similar equations are obtained using similarity transformations and solved numerically by a shooting algorithm with a Runge-Kutta Fehlberg integration scheme. The velocity profiles, temperature profiles, the local skin friction coefficient, and the local Nusselt number are computed and discussed in details for various values of the different parameters. Numerical results are presented both in tabular and graphical forms, illustrating the effects of these parameters on the thermal and concentration boundary layers. It is revealed that the thermal boundary layer thickens with a rise in the flow unsteadiness and as Newtonian heating intensifies, while the local skin friction and the rate of heat transfer at the plate surface change significantly due to the slip parameter.

Resumo em Inglês:

The turbulent flow in a Kenics Static Mixer (KSM) was intensified under the mutual-coupling effect between the twisted leaves and the tube-wall. In order to understand the intrinsic features of turbulent flow in KSM, the Hilbert-Huang Transform based on Empirical Mode Decomposition were first introduced to describe the time-frequency features of the pressure fluctuation. The Hilbert spectra of pressure fluctuation time series were quantitatively evaluated under different Reynolds numbers, and different radial and axial positions, respectively. The experimental results showed that: the fluctuation frequencies of pressure signals in a KSM were mainly distributed below 40 Hz, and more than 68% of the energy of signals is concentrated within 10 Hz. Compared with the other IMFs, the pressure component of C6 in the range of 7.82~15.63 Hz has the maximum fluctuation energy ratio. As the flow rate increases, the energy of fluctuation of fluid micelles and the proportion of low-frequency energy increases. The pressure fluctuation with higher energy ratio of low frequency (0~10 Hz) had lower amplitudes at r/R=0.3 because of the core of forced vortex. Nevertheless, the effect of the free vortex was that the pressure fluctuation with lower energy ratio of low frequency had higher amplitudes at r/R=0.8. The higher amplitudes of pressure fluctuation at cross sections of CS3 (z=420 mm) and CS5 (z=620 mm) proved that the transitions between the adjacent mixing element had better mixing performance.

Resumo em Inglês:

This work deals with a new numerical methodology to solve the Navier-Stokes equations based on a finite volume method applied to structured meshes with co-located grids. High-order schemes used to approximate advective, diffusive and non-linear terms, connected with multiblock partition techniques, are the main contributions of this paper. Combination of these two techniques resulted in a computer code that involves high accuracy due the high-order schemes and great flexibility to generate locally refined meshes based on the multiblock approach. This computer code has been able to obtain results with higher or equal accuracy in comparison with results obtained using classical procedures, with considerably less computational effort.