Volume 15, Issue 5 - Special Issue in honor of Prof. Ochoa, Guest Editors: Carlos Castillo Araiza and Benito Serrano

This work is devoted to briefly describe the scientific achievements of J. Alberto Ochoa-Tapia and his research group along almost three decades. The motivation for performing this review is not only to acknowledge his contributions, but also to share with the scientific community a brilliant scientific career. Although an exhaustive and complete review is beyond the scope of this paper, many of Alberto’s scientific contributions are briefly described. In addition, special attention is dedicated to three subjects, namely: Chang’s unit cell, the derivation of boundary conditions between a porous medium and a fluid and the use of Green’s functions to solve boundary-value problems. The first one is a convenient approach to derive analytical expressions of effective-medium coefficients resulting from the volume averaging method. The second one is Alberto’s most referenced work and it is of paramount importance since it provides the means to complete the statement of multiscale modeling. The third focus of attention is about the use of Green’s functions to solve nonlinear boundary-value problems in an efficient manner. Finally, his current and future works are discussed.

In-situ combustion (ISC) is an oil recovery technique where many phenomena can take place simultaneously such as: chemical reactions, phase change, heat transfer, mass transport, thermodynamic equilibrium, and so on. Each one of these phenomena may have important contributions over the ISC behavior at any scale of interest as lab-scale, inter-wells or reservoir-scale. In this work, a mass transport study is presented. Firstly, the appropriate phase and interface governing equations at pore-scale are set up. Later, the volume averaged equations valid at macroscale are rigorously derived using the volume averaging method (VAM). The theoretical analysis is general and applies for typical oil-water-gas-rock systems found in petroleum reservoirs, and for any number of chemical species distributed in the phases. The model also allows the existence of several heterogeneous and homogeneous chemical reactions. From this general point of view, the volume averaged equations governing species and phase mass transport at macroscale, along its closure scheme to predict the effective transport parameters, are presented. We have clearly identified the length scale constraints and assumptions that support our derivations. In future works, we shall expand the range of applicability of the model by relaxing some of these assumptions. To demonstrate the applicability of the average models, we numerically predicted the longitudinal mass dispersion of oxygen for passive and reactive mass transport problems at lab-scale. The general trends of theoretical results are in concordance with previous works.

In this note, the effects of the non-Fickian diffusion on the prediction of effectiveness factor in non-isothermal porous catalytic slab considering external transport resistances are studied. A Green’s function formulation is used to solve the fractional diffusion-reaction model assuming non-Fickian diffusion to describe the internal mass transport in the porous catalytic particle. Evaluation of the effectiveness factor considering linear and nonlinear reaction rates was developed under isothermal and non-isothermal conditions. In both cases, numerical simulations show the relation existent between the anomalous diffusion with the performance of the catalytic slabs.

This work presents the design of a class of finite time observer applied to a nonlinear switched system. The proposed observer is applied to a stirred batch anaerobic bioreactor, described by classic mass balances, where a sulfate-reducing process took place and kinetic regimen alteration is induced by a change in the carbon source. The proposed observer has a simple structure and under an adequate choosing of the observer´s gain the proposed methodology cancels the upper bounds of the system under the different kinetic regimens inducing the required finite time convergence. The performance of the proposed observer is showed via numerical simulations and for comparison purposes a sliding-mode observer is also implemented, both of them are conducted and experimentally corroborated. The convergence of the observer is done with a simple analysis of the estimation error dynamic equations for all the corresponding subspaces and is showed that the convergence of the estimator is reached under the required conditions.

In this paper, a Haar wavelets based numerical method to solve a system of linear or nonlinear fractional differential equations has been proposed. Numerous nontrivial test examples along with practical problems from fluid dynamics and chemical engineering have been considered to illustrate applicability of the proposed method. We have derived a theoretical error bound which plays a crucial role whenever the exact solution of the system is not known and also it guarantees the convergence of approximate solution to exact solution.

Sorbent orange peel based materials activated using NaOH and H 3 PO 4 were prepared and evaluated in order to compare sorbent efficiency, and related to their physicochemical properties. Results of physicochemical characterization demonstrated there are significant changes on surface that promotes an adsorption behavior depending on the activation method. FTIR analysis shows decreasing signal of water at 3422 cm −1 of water, hemicellulose and pectin due to activation process, another decreasing signal is observed at at 1626 cm −1 for CC bond, while an increasing pick is observed at 1435 cm −1 which corresponds to methoxyl groups belonging to cellulosic compounds. Analysis of sorption equilibrium indicated 78 % of methyl orange sorption in orange dry peel (OP) which was sorbed after 5 hour, compared to 84 % and 98 % using 0.1 M activated sorbent material 2(AM2) and 0.6 M activated sorbent material 3 (AM3) H 3 PO 4 respectively, this process was carried out during the first 90 min of sorption process. NaOH activated sorbent material 1 (AM1) promoted 20 % to 65 % sorption. orange dry peel (OP), activated sorbent material 2 (AM2) and activated sorbent material 3 (AM3) obeyed a pseudo-second order kinetic model, while activated sorbent material 1 (AM1) obeys a pseudo-first order model. Sorption equilibrium of methyl orange resulted as follows, orange dry peel (OP) followed a Freundlich equilibrium model, activated sorbent material 1 (AM1) a Langmuir model, while activated sorbent material 2 (AM2) and activated sorbent material 3 (AM3) to Hill model. Activated sorbent materials with H 3 PO 4 showed 750–770 mg/g of methyl orange which represent high sorption capacities. Orange peel sorbent material previously activated with H 3 PO 4 represents a good alternative to reduce water pollution, and also residues of orange peel could be reduced by this alternative treatment.

In this work, the catalytic activity was investigated in the hydrogenation of anthracene by BaSO 3 and Cu(II), Zn(II) and Ni(II) complexes that contain the ligand bis(3,5-dimethyl-1-pyrazolyl) methane ( L ). The compounds were supported on activated carbon ( AC ) and studied as catalysts for the hydrogenation of anthracene over different temperatures and reaction times. The supported catalysts (Cat/ AC ) were prepared by direct impregnation on the support and characterized by surface area determination, FTIR spectroscopy, and X-ray powder diffraction and pore size distribution analysis. The results showed high conversions and selectivity toward hydrogenated products, where the highest value was obtained using LNiCl 2 / AC and the lowest with BaSO 3 / AC . It was established that the selectivity for Tetrahydroanthracene was more highest quantity as a product of hydrogenation using Cat/ AC which is dependent of the temperature, reaching a peak at 450 °C. At this temperature and with very short reaction times, the catalytic activity is influenced mainly by the chemical characteristics of the metal in the complexes and the AC support.

The aim of this work is to discuss the relative contribution of homogeneous and heterogeneous Fenton processes in the treatment of Orange II dye solutions at pH 3 and 7 using an ion exchange resin as iron support. While at pH 3, 99% of the colour was removed, under neutral conditions a decoloration of 56% was observed. Studying the release of iron from the resin, we found a concentration of 1.49 mg/L of ferric ion and 0.31 mg/L of ferrous ion at pH 3 and 1.08 mg/L and 0.11 mg/L at pH 7, revealing that as expected, dissolution of iron ions at pH 3 is larger. Using these concentrations in a homogeneous process, 45% of the colour can be removed at pH 3 and 10% at pH 7, so it was infered that there is an effect of the iron that is still supported on the resin. In this way, a mixed homogeneous/heterogeneous mechanism could be proposed. While the experimental data for the desorption of iron at pH 3 was well suited to a pseudo second order kinetic model, the desorption of iron at pH 7 was fit to pseudo-first order kinetics. Experimental results of dye decolorization were on the other hand, fitted to a pseudo first order kinetics.

Abstarct This study focuses on the investigation of two-dimensional steady Stokes flow inside topographically patterned microchannel. Boundary element method (BEM) is used to solve the Stokes equation and obtain the streamline profiles. The velocity field and pressure gradients are obtained by taking the appropriate spatial derivatives of the stream function and vorticity variables. We restrict ourselves to rectangular stepped geometries and study the effect of variation of step width, step height and step frequency. Interestingly, ‘crown-shaped’ patterns in the horizontal velocity profiles are formed when a sudden contraction is met in the flow region. Pressure gradients, together with the velocity and streamline profiles are analyzed to gain a wholesome understanding of the flow physics.

The photocatalysis, sonocatalysis and their combination operated sequentially have been studied to treat the decolorization and mineralization of a cationic dye, Rhodamine B, using heterogeneous TiO 2 catalyst. Effects of various operating parameters such as catalyst loading, H 2 O 2 addition, and pH on photocatalytic and sonocatalytic processes were investigated. For both photocatalysis and sonocatalysis optimum catalyst and hydrogen peroxide concentrations were observed, while the dye degradation rates were favored at acidic conditions. Photocatalysis resulted in higher color degradation efficiencies compared with sonocatalysis. Coupled photosonocatalytic process showed better efficiencies for color degradation than the achieved by individual photocatalysis and sonocatalysis operating separately, implying possible synergy; however, no synergetic effect was observed for dye mineralization. Apparently the sequential photosonocatalytic operation process was more effective in inducing color degradation than mineralization.

Methane aromatization is a promising technology for the transformation of natural gas to added-value products. The main objective of this work was to obtain a catalyst with suitable performance and good mechanical stability for methane aromatization reaction in fluidized bed reactors. The selected catalyst was Mo/H-ZSM-5/bentonite mixture. Mo/ZSM-5 was chosen as the active material, since it provides good selectivity to aromatics but the particle size of the zeolite was too small for operation in a fluidized bed and a binder was needed. We prepared two series of catalysts with two different zeolites. We tested several heating velocities (1, 7 and 10 °C min ‒1 ) in the different stages of catalyst synthesis. Methane conversion and selectivity to aromatic products improved when using gentle thermal treatments, increasing 2% and 10%, respectively, for the best catalyst tested.

Polymers and specifically hybrid polymeric membranes have been identified as effective formulations in adsorption processes. Nevertheless, the adsorption mechanisms associated with their thermodynamics and kinetics are not fully understood, particularly when these polymeric membranes are used to adsorb 2-Phenylethanol (2-PE) to intensify its production in a specific bioconversion process. This work was aimed at giving phenomenological insights on the adsorption of 2-PE on a set of novel porous hybrid membranes based on polyurethane and keratin biofiber obtained from chicken feathers. Feathers, considered as a waste by-product of the poultry industry, represent an alternative source of keratin, a biopolymer that can be used to design low-cost materials from natural resources. Two types of hybrid membranes were prepared. i. e. composite and copolymer. Firstly, these materials were characterized by scanning electron microscopy (SEM), infrared spectroscopy (FT-IR) (before and after the adsorption process) and X-Ray (WAXD) analysis. Secondly, these materials, including the reference ones (keratin biofiber and polyurethane), were evaluated during the removal of 2-PE, relating their adsorption capabilities to physiochemical properties elucidated during the characterization. Particularly a composite with 0.1 g of chicken-feather-keratin (C1) presented the highest removal percentage (60.68%), a significant initial adsorption rate (0.2340 mg PE .h −1 .g A −1 ), the maximum adsorption capacity (12.13 mg PE .g A −1 ) and the best stability and mechanical properties at studied operating conditions. In comparison with results reported in literature, in this composite carbonyl functional groups from polyurethane showed rather major affinity to 2-PE than amino groups from the keratin biofiber. To this end, parameters associated with its industrial application were obtained, namely thermodynamic and kinetic information was obtained from a proper design of experiments and phenomenological models based on adsorption macroscopic fundamentals.

La-, Mn- and Fe-doped ZrO 2 was synthesized using the sol-gel method, washcoated on cordierite monoliths and used in trichloroethylene (TCE) combustion. A sol from sol-gel synthesis method was used to obtain the zirconia washcoatings. The washcoatings deposited on the cordierite monolith materials were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and N 2 physisorption measurements, being the crystalline phase determination the most correlate with the catalytic activity. The washcoat properties were correlated to their performance in trichloroethylene combustion. The catalytic washcoatings contained a mixture of crystalline tetragonal ZrO 2 and monoclinic ZrO 2 , and the monoclinic phase exhibited strong interactions with the α-cordierite crystalline phase. For the kinetic tests, the mass transfer into the washcoated monolith channels was evaluated using a recently developed model for the internal mass transfer coefficients for diffusion and reactions in catalytic monoliths. This model involves three resistances. In a plot of the overall resistance as function of the Thiele modulus was determinate that he reaction occurred in the kinetically controlled regime. The kinetic data were fit to two Langmuir–Hinshelwood (LH) models, and the reaction rate was fitted as a function of the trichloroethylene inlet concentration. The adsorption parameters obtained with both LH models were validated based on thermodynamic criteria for the changes in the standard enthalpy of adsorption(${\Delta}H_{ads}^0$ΔHads0) and standard total entropy of adsorption (${\Delta}S_{ads}^0$ΔSads0). It was found that adsorbed TCE and oxygen atoms should be more mobile over the catalyst, which had a higher proportion of tetragonal phase than monoclinic phase of zirconia. The La, Fe-doped catalyst exhibited the highest activity, mainly due the presence of tetragonal zirconia.

Hydrogen concentration in a photocatalytic continuous bioreactor was estimated. For the above system, a novel kinetic model of the sulfate-reducing process for hydrogen production was proposed and experimentally confirmed. In addition, we present the design of an estimator based on nonlinear observer, which is robust against modeling errors, to estimate the observable states of the bioreactor. Sulfate, biomass, sulfide, carbon dioxide, cadmium in liquid, cadmium sulfide, and hydrogen concentrations were estimated in spite of errors in the evaluation of the parameters using sulfate concentration as measurable output. The convergence of the proposed observer was analyzed using Lyapunov stability theory. Finally, maximum hydrogen production was 225 mL and 175 mL for batch and continuous processes, respectively.