Vilarrasa-Garcia E.,Associated Unit of Institute Catalisis y Petroleoquimica |
Infantes-Molina A.,Associated Unit of Institute Catalisis y Petroleoquimica |
Moreno-Tost R.,Associated Unit of Institute Catalisis y Petroleoquimica |
Rodriguez-Castellon E.,Associated Unit of Institute Catalisis y Petroleoquimica |
And 3 more authors.
Energy and Fuels | Year: 2010
International regulations have established the decrease on sulfur content in fuels down to as low as 10 ppm in a few years from now. Cyclic sulfur compounds are noticeably refractory to hydrodesulfurization (HDS) processes, which are the usual technology found in oil refineries. To meet the increasingly strict environmental requirements, selective physisorption may be a feasible option toward lowering the sulfur content of the outlet streams of current HDS units. The present work investigates the adsorption of benzothiophene (BT) and dibenzothiophene (DBT) in hydrophobic microporous activated carbons impregnated with PdCl2 . The adsorbents used were commercial samples (Norit, Amersfoort, The Netherlands) modified by wet impregnation of PdCl2 in acidic media, followed by drying at 130 °C under He flow. They were characterized by N2 adsorption isotherms, transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectronic spectroscopy (XPS). Characterization results provide evidence that palladium was effectively supported on the activated carbon as the chloride itself and as metallic palladium. A total of 20 mL of BT and DBT solutions in hexane (500 ppm) were put in contact with 100 mg of each adsorbent, and the adsorbed capacities were measured by the concentration differences. Additionally, Fourier transform infrared (FTIR) spectra were measured upon adsorption of BT vapors. The impregnation of PdCl2 enhances sulfur adsorption capacity for most studied cases, and sulfur compounds with an increasing number of aromatic rings are preferentially adsorbed. © 2010 American Chemical Society.
Silva L.,Campus Universitario Do Pici |
Maia G.,Campus Universitario Do Pici |
Sousa P.,Federal University of Ceara |
Figueiredo R.,Campus Universitario Do Pici |
And 4 more authors.
Acta Alimentaria | Year: 2014
The purpose of this experiment was to evaluate the effect of heat treatment on the rheological properties of mixed nectars, based on cashew apple, mango, and acerola pulps. Ten different formulations with different mass fractions of cashew apple, mango, and acerola pulps were prepared using a simplex centroid design [with a total of 35% (w/w) pulp] and submitted to heat treatment at 90 C for 1 min. Samples were collected before and after heat treatment and characterization of their rheological properties was carried out. The rheological behaviour was obtained at 25 C, with shear rate ranging from 108 to 500 s (upward curve) and from 500 to 108 s (downward curve) for 1 min with 25 readings for each curve. The Ostwald de Waele model showed to be a good fit for all formulations studied, which showed a non-Newtonian behaviour and a pseudoplastic character. Results of apparent viscosity for the non-heated formulations were well fitted by the linear model and the heat treated formulations by the cubic model. The heat treated formulations had higher (P<0.05) values of consistency index and apparent viscosity, as well as lower (P<0.05) values of flow behaviour index compared to non-heated formulations. The rheological characterization of these formulations is a very useful tool during product development and processing control of mixed nectars of fruit juice.
Rodrigues A.K.O.,Campus Universitario Do Pici |
Ramos J.E.T.,Campus Universitario Do Pici |
Cavalcante Jr. C.L.,Campus Universitario Do Pici |
Rodriguez-Castellon E.,University of Malaga |
Azevedo D.C.S.,Campus Universitario Do Pici
Fuel | Year: 2014
Desulfurization of benzothiophene/isooctane mixtures and gasoline (42.5 and 1000 ppmw S) was studied by batch and fixed bed experiments using PdCl 2 supported on mesoporous silica of SBA-15 type (PdCl 2/SBA-15). The Pd-loaded silica was prepared by solid-phase impregnation of the metal halide on the mesoporous siliceous matrix (SBA-15). SBA-15 and PdCl2/SBA-15 were characterized with N2 adsorption/desorption isotherms, small angle X-ray diffraction and transmission electron microscopy (TEM). Then desulfurization of benzothiophene/isooctane mixtures and gasoline (42.5 ppmw S) with these sorbents was investigated by batch and fixed bed experiments. PdCl2/SBA-15 showed much higher capacity for sulfur adsorption than both the starting material and PdCl 2 itself. A mathematical model was used to represent the breakthrough curves for adsorption and desorption runs in fixed bed, providing very good agreement between numerical simulations and adsorption data. The spent PdCl 2/SBA-15 was regenerated using isooctane as eluent, and the regenerated PdCl2/SBA-15 was tested again for the desulfurization of 1000 ppm S gasoline (down to 50 ppm). The results showed that the sulfur adsorption capacity at the break point (C = 50 ppm) remained nearly unchanged for three cycles, even though XPS elemental analysis for the fresh and spent adsorbent revealed some degree of leaching of the metal from the external surface, particularly as Pd(II). In conclusion, PdCl2/SBA-15 appears to be a robust adsorbent for desulfurization of liquid fuels and the model proposed herein was able to predict deep desulfurization of gasoline in cyclic mode. © 2014 Elsevier Ltd. All rights reserved.