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Amaral J.S.,University of Porto | Amaral J.S.,Polytechnic Institute of Bragana | Sepulveda M.,Laboratory of Separation and Reaction Engineering LSRE | Cateto C.A.,Laboratory of Separation and Reaction Engineering LSRE | And 5 more authors.
Polymer Degradation and Stability | Year: 2012

In this work, the ability of Aspergillus niger to degrade two lignin-based rigid polyurethane (RPU) foams was evaluated and compared with a control RPU foam based on a commercial polyether-polyol, Lupranol ® 3323. The foams degradation was studied according to different procedures, namely by setting different series of batch cultures, either using liquid media or soil conditions, for 90 days at 30°C. For the soil conditions, two different assays were performed, namely with and without A. niger addition. The changes in the morphology of the RPU foams were evaluated by optical (OM) and scanning electron microscopy (SEM), whereas the structural modifications were inspected by FTIR spectroscopy. After 90 days treatment, morphological changes were clearly visible at the surface (cell wall) of the two lignin-based foams indicating a stronger effect of the microorganisms' activity in these samples. FTIR spectra confirmed that the chemical structure of the polymer suffered modifications after the respirometry assays due to microorganisms attack. Comparatively to the commercial foam, it was observed that both the lignin-based foams presented a higher degradation level. © 2012 Elsevier Ltd. All rights reserved. Source

Grande C.A.,Laboratory of Separation and Reaction Engineering LSRE | Gascon J.,Technical University of Delft | Kapteijn F.,Technical University of Delft | Rodrigues A.E.,Laboratory of Separation and Reaction Engineering LSRE
Chemical Engineering Journal | Year: 2010

Selective adsorption of propylene from mixtures with propane over a lithium-exchanged zeolite 13X has been studied. Adsorption equilibrium of pure gases has been evaluated at three different temperatures by volumetric and gravimetric methods. Propylene is adsorbed preferentially over propane, particularly at low pressures. Adsorption equilibrium can be well described with the multi-site Langmuir and the Virial models. At 1 bar and 323 K, the amount adsorbed of propylene is 2.5 mol/kg while the loading of propane is 2.0 mol/kg. The dynamic behavior of the sample has also been evaluated on the bench scale in a fixed-bed for binary breakthrough performance. Macropore adsorption controls the diffusion process within the extrudates of the zeolite. The mathematical model could satisfactorily predict the behavior of the bed. The data obtained in this work allows to model any adsorption-based process for propane/propylene separation, like vacuum pressure swing adsorption and simulated moving bed. © 2010 Elsevier B.V. All rights reserved. Source

Caleja C.,Polytechnic Institute of Braganca | Caleja C.,Laboratory of Separation and Reaction Engineering LSRE | Caleja C.,University of Porto | Barros L.,Polytechnic Institute of Braganca | And 5 more authors.
Food Chemistry | Year: 2016

Consumers demand more and more so-called "natural" products and, therefore, the aim of this work was to compare the effects of natural versus synthetic antioxidant preservatives in yogurts. Matricaria recutita L. (chamomile) and Foeniculum vulgare Mill. (fennel) decoctions were tested as natural additives, while potassium sorbate (E202) was used as a synthetic additive. The fortification of yogurts with natural and synthetic antioxidants did not cause significant changes in the yoghurt pH and nutritional value, in comparison with control samples (yogurt without any additive). However, the fortified yogurts showed higher antioxidant activity, mainly the yogurts with natural additives (and among these, the ones with chamomile decoction). Overall, it can be concluded that plant decoctions can be used to develop novel yogurts, by replacing synthetic preservatives and improving the antioxidant properties of the final product, without changing the nutritional profile. © 2016 Elsevier Ltd. All rights reserved. Source

Granato M.A.,Laboratory of Separation and Reaction Engineering LSRE | Jorge M.,Laboratory of Separation and Reaction Engineering LSRE | Vlugt T.J.H.,Technical University of Delft | Rodrigues A.E.,Laboratory of Separation and Reaction Engineering LSRE
Chemical Engineering Science | Year: 2010

This paper presents single component diffusion data of propane, propylene and isobutane in zeolite 13X obtained by molecular dynamics (MD) simulations, especially its dependence on temperature and concentration. Our results are critically compared to experiments and previous simulation data, when available. One novelty of this work is that the diffusion coefficients are computed taking the framework cations of zeolite 13X into consideration. Furthermore, to our knowledge, we present the first simulation results for propylene diffusion in faujasite frameworks. From the mean squared displacements, self-diffusion coefficients of 7.5×10-9, 9.1×10-9, and 9.6×10-10 m2 s-1 for 2 molecules/unit cell were calculated for propane, propylene, and isobutane at 373 K, respectively. The simulations show that the diffusivity decreases with increasing loadings for all adsorbates studied. Finally, transport diffusivities were estimated from the self-diffusion coefficient and the equilibrium adsorption isotherms by using the Darken equation. © 2010 Elsevier Ltd. All rights reserved. Source

Liu Z.,East China University of Science and Technology | Liu Z.,Laboratory of Separation and Reaction Engineering LSRE | Grande C.A.,East China University of Science and Technology | Grande C.A.,Laboratory of Separation and Reaction Engineering LSRE | And 3 more authors.
Separation and Purification Technology | Year: 2011

A detailed framework for simulation of VPSA units is presented. Within this framework, a detailed description of the adsorbent column is provided and linked with other ancillary parts of the unit. This modeling strategy is particularly suitable to demonstrate how the entire unit works and to identify operating constraints that may be caused by ancillary equipment. In order to apply this strategy to a practical example, we have simulated different cycles of VPSA processes using zeolite 5A for CO 2 capture from a mixture with 15% CO 2-85% N 2 (resembling post-combustion flue gases of a coal-fired power station). Simulations of VPSA units with two, three and four columns and different cycle configurations were carried out. Inclusion of a rinse step was necessary to improve CO 2 purity. However, using a single VPSA unit, it was not possible to achieve purity higher than 77% and for this reason a two-stage VPSA unit was simulated. The two-stage VPSA simulations include a three-column front VPSA process where CO 2 purity is increased to 70% and then this gas is recompressed to a second, tail two-column VPSA unit where CO2 purity increases to 96%. The overall unit productivity of this process is 0.0146 kgCO 2/(kgads h) with an energy consumption of 645.7 kJ/kgCO 2. © 2011 Elsevier B.V. All rights reserved. Source

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