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Portilla-Rivera O.M.,Polytechnic University of Guanajuato | Moldes A.B.,University of Vigo
Journal of Agricultural and Food Chemistry | Year: 2010

The results of the present study show that Lactobacillus pentosus can produce extracellular bioemulsifiers by utilizing hemicellulosic sugars from grape marc as a source of carbon. The effectiveness of these bioemulsifiers (LPEM) was studied by preparing kerosene/water (K/W) emulsions in the presence and absence of these emulsifiers. Various parameters such as relative emulsion volume (EV), stabilizing capacity (ES), viscosity, and droplet size of K/W emulsions were measured. The EV values for K/W emulsions stabilized by concentrated LPEM were approximately 74.5% after 72 h of emulsion formation, with ES values of 97%. These values were higher than those obtained with dodecyl sodium sulfate as emulsifier (EV = 62.3% and ES = 87.7%). Additionally, K/W emulsions stabilized by LPEM produced polydisperse emulsions containing droplets of radius between 10 and 40 μm, which were smaller than those obtained for K/W emulsions without LPEM (droplet radius = 60-100 μm). Moreover, the viscosity values of the K/W emulsions without and with LPEM were approximately 236 and 495 cP, respectively. © 2010 American Chemical Society.


Arenas M.C.,National Autonomous University of Mexico | Sanchez G.,Autonomous University of Queretaro | Martinez-Alvarez O.,Polytechnic University of Guanajuato | Castano V.M.,National Autonomous University of Mexico
Composites Part B: Engineering | Year: 2014

Aqueous suspensions of polyvinyl alcohol-polyaniline (PVA-PAni) nanocomposites were prepared by conventional polymerization of aniline in the presence of a PVA solution mixed with either a surfactant (sodium dodecyl sulfate) or organic acids (poly acrylic acid or 2-acrylamido-2-methyl-1- propanesulfonic acid) used as binary dopants, to improve the solubility of the nanocomposites. Films were prepared by casting at different contents of PAni (1-60 wt.%). The best homogeneous films were obtained from the surfactant nanocomposites with a low threshold percolation, between 3 wt.% and 5 wt.% of PAni, achieving an electrical conductivity about 0.044 S/cm, attractive as an antistatic material in electronics, since also their mechanical properties are adequate. © 2013 Elsevier Ltd. All rights reserved.


Arteaga-Arcos J.C.,National Autonomous University of Mexico | Chimal-Valencia O.A.,Polytechnic University of Guanajuato | Yee-Madeira H.T.,National Polytechnic Institute of Mexico | Diaz De La Torre S.,CIITEC IPN
Construction and Building Materials | Year: 2013

The High-Strength Cement (HSC) technology is based on modification of Normal Use Portland Cement (NUPC) by complex admixtures, optimization of mixture design and grinding process. The present work shows the results of preparing and using Ultra-Fine Cement (UFC) as a binder material addition with no extra admixtures of different chemical composition to increase the compressive strength of mortars. The aim of this work is to demonstrate how a NUPC can be converted into a sort of HSC; it was observed that the 70-60 wt%NUPC + 30-40 wt%UFC blend satisfies the goal of increasing mortar's compressive strength. © 2013 Elsevier Ltd. All rights reserved.


Guerra-Rodriguez E.,University of Santiago de Compostela | Portilla-Rivera O.M.,Polytechnic University of Guanajuato | Ramirez J.A.,Autonomous University of Tamaulipas | Vazquez M.,University of Santiago de Compostela
Biomass and Bioenergy | Year: 2012

The hydrolysis of non-commercial potatoes to obtain glucose solutions has a double consequence, the elimination of a waste and the generation of a value-added product. Potato hydrolysates can be used to prepare growth media for fermentative processes. This work deals with the modelling of the acid hydrolysis of potato using sulphuric acid. The effect of temperature, time, acid concentration and liquid/solid ratio were evaluated. Considering the important effect and interactions of the variable involved, a statistical Box-Behnken design was conducted including the cited variables as operational variables and concentrations of glucose, fructose, arabinose, acetic acid, furfural and 5-(hydroxymethyl)-2-furaldehyde (HMF) released as dependent variables. Significant models were obtained. The maximum glucose concentration predicted was 85 kg m-3. The conditions selected as optimal were: Temperature, 120 °C; time, 60 min; acid concentration, 2.4 kg m-3 and liquid/solid ratio, 9.8 g g-1. The acid hydrolysis of dried potatoes gave solutions with 58 kg m-3 of glucose and only 0.47 kg m-3 of HMF. These solutions are adequate for further fermentation process. © 2012 Elsevier Ltd.


Guerra-Rodriguez E.,University of Santiago de Compostela | Portilla-Rivera O.M.,Polytechnic University of Guanajuato | Jarquin-Enriquez L.,Polytechnic University of Guanajuato | Ramirez J.A.,Autonomous University of Tamaulipas | Vazquez M.,University of Santiago de Compostela
Biomass and Bioenergy | Year: 2012

Biotechnological xylitol production can be enhanced if the needed xylose solutions can be obtained from hydrolysis of low-cost lignocellulosic wastes. The hydrolysis of wheat straw to obtain xylose solutions has a double consequence, the elimination of a waste and the generation of a value-added product. The objective of this work was to study the xylose production from wheat straw by sulphuric acid hydrolysis at 130 °C. Several mass fraction of acid (1, 2, 3, 4 or 5%) were evaluated. Kinetic models were developed to explain the variation with time of xylose, glucose, arabinose, furfural, 5-(hydroxymethyl)-2-furaldehyde and acetic acid in the hydrolysates. Optimal conditions found were a H 2SO 4 mass fraction of 2% at 130 °C for 29 min, which yielded a solution with xylose, 18.9 kg m -3; glucose, 3.5 kg m -3; arabinose, 3.1 kg m -3; furfural, 0.6 kg m -3; 5-(hydroxymethyl)-2-furaldehyde, 0.3 kg m -3 and acetic acid, 2.3 kg m -3. In these conditions, 99% of the hemicelluloses and 11% of the glucan were hydrolysed. © 2011 Elsevier Ltd.


Arenas M.C.,National Autonomous University of Mexico | Rodriguez-Nunez L.F.,National Autonomous University of Mexico | Rangel D.,National Autonomous University of Mexico | Martinez-Alvarez O.,Polytechnic University of Guanajuato | And 2 more authors.
Ultrasonics Sonochemistry | Year: 2013

In this work, hybrid nanocomposites based on anatase titania:polypyrrole (TiO2:PPy) were directly obtained from a simple, one-step, ultrasonic (UT)-assisted synthesis. The properties of these crystalline nanocomposites were compared with those of others fabricated using cold (Cold)-assisted synthesis without any UT assistance, which required a hydrothermal treatment (HT) to yield crystalline anatase titania in the nanocomposite (TiO 2:PPy) at low temperature (130°C) and in a short time (3 h). The SEM results demonstrated that the UT-assisted synthesis is a feasible method to obtain anatase TiO2:PPy nanocomposites with controlled morphology using low energy. The Fourier transform infrared (FT-IR) bands of the crystalline nanocomposites exhibited a shift with respect to neat components, which was attributed to the strong interaction between the secondary amine groups (N-H) of PPy and the oxygen from TiO2. The acceptable absorption in the visible region (λmax = 670 nm) indicates that these nanocomposites are good candidates for harvesting energy in solar cells. Devices based on these nanocomposites were built to evaluate their electrical properties. An increase in the photocurrent was observed for the devices prepared with the nanocomposites from the UT-assisted synthesis. © 2012 Elsevier B.V. All rights reserved.


Picon-Nunez M.,University of Guanajuato | Polley G.T.,University of Guanajuato | Canizalez-Davalos L.,University of Guanajuato | Medina-Flores J.M.,Polytechnic University of Guanajuato
Energy | Year: 2011

This paper considers the design of cooling systems in the context of piping costs, exchanger costs, pumping costs and its hydraulic and thermal performance. A methodology for designing coolers in the context of both process needs and cooling water system behaviour is introduced. It is recognised that cooling systems need to be flexible. One way of ensuring this is to design a system for the most demanding load and then use bypasses to control performance under reduced load.The hydraulic modelling is based on new formulations of flow resistance for pipes, pipe fittings and equipment items. By using volumetric flow rate rather than velocity as the prime variable it becomes possible to construct hydraulic models for cooling water systems quickly. These calculations then provide predictions of water flows to the individual heat exchangers in the cooling water network. Knowledge of these flows is fundamental to both the design of new coolers and the prediction of the thermal performance of exchangers of known geometry. Previous studies have ignored this aspect of design. © 2011 Elsevier Ltd.


Medina-Flores J.M.,Polytechnic University of Guanajuato | Picon-Nunez M.,University of Guanajuato
Chemical Engineering Science | Year: 2010

A thermodynamic model for the prediction of the operating performance of back pressure steam turbines with single and multiple extractions is presented. The approach takes the advantage of previous models reported in the literature and incorporates some improvements that allow for the prediction of the shaft work under changes in the operating conditions such as steam flow rate and pressure of each of the extractions. Simulation under changed operating conditions is conducted through the use of expressions that correlate the temperature and enthalpy of the steam as a function of the extraction pressure. The model incorporates the calculation of the isentropic efficiencies of each stage. The validity of the model is demonstrated by comparing the results with those of commercial turbines reported in the open literature. © 2010 Elsevier Ltd. All rights reserved.


Ruiz-Camacho B.,Polytechnic University of Guanajuato | Santoyo H.H.R.,Polytechnic University of Guanajuato | Medina-Flores J.M.,Polytechnic University of Guanajuato | Alvarez-Martinez O.,Polytechnic University of Guanajuato
Electrochimica Acta | Year: 2014

Electrocatalytic activities and stabilities of Pt supported on SnO 2-carbon and TiO2-carbon as electrocatalysts were examined for methanol oxidation and oxygen reduction reactions. The Pt/oxide-C catalysts were synthesized by photo-deposition method at RT. The samples prepared were characterized by X-ray diffraction, TEM analysis, cyclic and lineal voltammetry, CO stripping and chronoamperometry techniques. Electrochemical activities of Pt/oxide-C for methanol oxidation reaction (MOR) and methanol tolerance for oxygen reduction were compared with those of Pt/C (Pt-Etek). The MOR activity of Pt/SnO2-C was enhanced over those of the Pt/TiO2-C and Pt/C at different concentrations due to the small platinum particles size. Pt-Sn interaction produce changes in the platinum electronic properties that improve the electrochemical activity towards the methanol oxidation and stability to the methanol presence. The SnO2-C composite appear to be a promising support material that promote electrochemical reactions and stabilize catalytic particles in direct alcohol fuel cells. © 2013 Elsevier Ltd.


Ruiz-Camacho B.,Polytechnic University of Guanajuato | Martinez-Alvarez O.,Polytechnic University of Guanajuato | Rodriguez-Santoyo H.H.,Polytechnic University of Guanajuato | Granados-Alejo V.,Polytechnic University of Guanajuato
Journal of Electroanalytical Chemistry | Year: 2014

Pt nanoparticles were synthesized by chemical vapor deposition and were deposited on carbon and TiO2-C substrates. The Pt/C and Pt/TiO 2-C catalysts synthesized were characterized by TEM and XRD techniques. Cyclic voltammetry and rotating disk electrode measurements for the Oxygen Reduction Reaction (ORR) were investigated in acid medium in presence of alcohols as methanol and ethanol. A Pt/C commercial sample was tested at the same conditions for comparison purposes. It was found that the catalyst nanoparticles were homogenously distributed over the carbon and TiO 2-carbon substrates with a mean particle size about 3 nm. Significant differences in the electrochemical results and alcohols tolerance are observed in the samples prepared in comparison whit Pt/C commercial catalyst. The methanol tolerance of the catalysts synthesized was higher compared to the ethanol tolerance. The electrochemical activity of Pt/TiO2-C catalyst prepared with TiO2 rutile phase was not affected by the presence of alcohols in comparison with Pt/C samples. It is explained by the thermal treatment over Pt/TiO2-C during the synthesis process that produces a synergetic effect caused by the formation of the interface between the platinum and oxide materials where titanium oxide acts as a protecting agent of platinum nanoparticles. © 2014 Elsevier B.V. All rights reserved.

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