Papers by Marcelo Santiago Zabaloy
Hydrogenation of Polybutadiene at High Pressure
Industrial & Engineering Chemistry Research, Dec 29, 2021
International Journal of Hydrogen Energy, May 1, 2014
In this work a thermodynamic analysis of the autothermal reforming (ATR) of methane was performed... more In this work a thermodynamic analysis of the autothermal reforming (ATR) of methane was performed. Equilibrium calculations employing entropy maximization were performed in a wide range of oxygen to methane mole ratio (O/M), steam to methane ratio (S/M), inlet temperature (IT), and system pressure (P). The main calculated parameters were hydrogen yield, carbon monoxide formation, methane conversion, coke formation, and equilibrium temperature. Further, the optimum operating oxygen to methane feed ratio that maximizes hydrogen production, at P=1 bar, has been calculated. The nonlinear programming problem applied to the simultaneous chemical and phase equilibrium calculation was implemented in GAMS ® , using CONOPT2 solver. The maximum amount of hydrogen obtained was in the order of 3 moles of hydrogen per mole of fed methane at IT=1000 °C, P=1 bar, S/M=5, and O/M=0.18.
Journal of Supercritical Fluids, Dec 1, 2017
Alternative systematic method for computing ternary phase equilibria Method based on ternary ... more Alternative systematic method for computing ternary phase equilibria Method based on ternary phase equilibrium characteristic maps Method applicable to highly non-ideal systems Multiple critical points and multiple three-phase equilibria are dealt with Method applicable to any equation of state
Industrial & Engineering Chemistry Research, Jan 26, 2011
In this work, we evaluate the potential of a modeling approach for describing the solid-fluid equ... more In this work, we evaluate the potential of a modeling approach for describing the solid-fluid equilibria of highly asymmetric mixtures over a wide pressure range. The model uses a mathematical expression for the fugacity of a pure heavy compound in solid state for which the reference state is the saturated solid under conditions of solid-liquid (melting) equilibrium at the system temperature T. Such a reference state differs from a common choice, which corresponds to the pure solid under conditions of solid-vapor (sublimation) equilibrium at T. By construction, the present modeling approach matches the solidliquid equilibria at high concentration of the heavy component. We discuss and test here a parametrization strategy for avoiding the simultaneous correlation of fluid-fluid and solid-fluid experimental data: first, the fluid-fluid equilibrium experimental data are correlated in the conventional way, and next, the solid-fluid equilibrium data are correlated by fitting a parameter that has no influence on the equation of state that describes the fluid phases. In this work, we study in detail the highly asymmetric system methane þ n-triacontane, for which experimental data are available over a wide range of conditions (Machado, J. J. B.; de Loos, T. W. Liquid-vapour and solid-fluid equilibria for the system methane þ triacontane at high temperature and high pressure. Fluid Phase Equilib. 2004, 222-223, 261-267). To model this system, we use a specific form of the present modeling approach. Such a specific model gives a good quantitative performance even at pressures in the order of 2000 bar. We also present additional modeling results for two other systems, i.e., for methane þ n-eicosane and methane þ n-tetracosane, which are also highly asymmetric.
Industrial & Engineering Chemistry Research, Nov 5, 2008
In this work, we propose a computational strategy and methods for the automated calculation of co... more In this work, we propose a computational strategy and methods for the automated calculation of complete loci of homogeneous azeotropy of binary mixtures and the related Pxy and Txy diagrams for models of the equation-of-state (EOS) type. The strategy consists of first finding the system's azeotropic end points (AEPs). These can exist on vapor-liquid (VL) critical lines (CAEPs), on liquid-liquid-vapor (LLV) lines (HAEPs), and on pure-compound vapor pressure lines (PAEPs). Next, for the chosen binary system, we generate one or two azeotropic lines. Each of these lines has, as its starting point, one of the previously identified AEPs. We calculate the azeotropic lines using a numerical continuation method that solves the nonlinear azeotropic system of equations under a range of conditions and efficiently tracks entire azeotropic curves. We have integrated our strategy for calculating azeotropic lines into a general algorithm for the single-run computation of binary global phase equilibrium diagrams (GPEDs). GPEDs are defined by pure-compound, critical, LLV, and azeotropic lines. We implemented this general algorithm in the computer program GPEC (Global Phase Equilibrium Calculations), which makes it possible to evaluate, at a glance, the behavior of a given model-parameter values combination, for a chosen model and binary system.
A theoretical study on the simultaneous vapor-liquid and chemical equilibria in a highly restricted system
Fluid Phase Equilibria, Jun 1, 2022
Journal of Supercritical Fluids, May 1, 2020
Computation and Analysis of Reactive Isopleths Involving Fluid Phases
Fluid Phase Equilibria, Nov 1, 2023
Journal of Supercritical Fluids, Dec 1, 2012
In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundar... more In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundaries at constant composition, for the systems 'polybutadiene (PB) + n-pentane (C5)', 'PB + dimethyl ether (DME) + C5', 'polyethylene (PE) + DME + C5', and 'PB + PE + DME + C5'. The temperature range of the experiments was from 50 to 184 • C. The maximum pressure was 303 bar. In all cases the overall polymer concentration was less than or equal to 4.1 wt%. At the ranges of conditions of the experiments we have found the following: (a) For PB + C5, the minimum pressure required to guarantee homogeneity is 140 bar. (b) For 'PB + C5 + DME', the cloud point pressure (CPP) curves lie in between the CPP curves of 'PB + DME' and 'PB + C5', and the maximum CPP was 226 bar. The CPP increases with the increase of the DME/C5 ratio in the solvent mixture. (c) For 'PE + DME + C5', there is a substantial decrease in the CPPs with the addition of C5 to the DME + C5 solvent mixture, and the maximum CPP was 303 bar. (d) The CPPs for 'PB + PE + DME + C5' are higher than the CPPs of 'PB + DME + C5' but lower than the CPPs of 'PE + DME + C5'.
Journal of Chemical & Engineering Data, 1996
Experimental liquid-liquid equilibrium data were obtained for systems containing water, NaCl, a l... more Experimental liquid-liquid equilibrium data were obtained for systems containing water, NaCl, a linear hydrocarbon solvent, a straight chain alcohol, and the two-tailed cationic surfactant dioctyldimethylammonium chloride (DODMAC). The experiments were carried out at 296.1 K and at atmospheric pressure. The solvents used were octane, decane, dodecane, tetradecane, and hexadecane. The alcohols utilized were 1-decanol and 1-dodecanol. High concentrations of water in the organic media and three phase transitions were observed for all solvent-alcohol combinations. The experimental results indicate the formation of water + hydrocarbon microemulsions for all systems.
The Journal of Supercritical Fluids, 2020
Midbrain dopamine (DA) neurons are not homogeneous but differ in their molecular properties and r... more Midbrain dopamine (DA) neurons are not homogeneous but differ in their molecular properties and responses to external stimuli. We examined whether the modulation of excitatory synapses on DA neurons by rewarding or aversive stimuli depends on the brain area to which these DA neurons project. We identified DA neuron subpopulations in slices after injection of ''Retrobeads'' into single target areas of adult mice and found differences in basal synaptic properties. Administration of cocaine selectively modified excitatory synapses on DA cells projecting to nucleus accumbens (NAc) medial shell while an aversive stimulus selectively modified synapses on DA cells projecting to medial prefrontal cortex. In contrast, synapses on DA neurons projecting to NAc lateral shell were modified by both rewarding and aversive stimuli, which presumably reflects saliency. These results suggest that the mesocorticolimbic DA system may be comprised of three anatomically distinct circuits, each modified by distinct aspects of motivationally relevant stimuli.
The Journal of Supercritical Fluids, 2017
Alternative systematic method for computing ternary phase equilibria Method based on ternary ... more Alternative systematic method for computing ternary phase equilibria Method based on ternary phase equilibrium characteristic maps Method applicable to highly non-ideal systems Multiple critical points and multiple three-phase equilibria are dealt with Method applicable to any equation of state
A general approach to phase diagrams for binary systems
Supercritical Fluid Science and Technology, 2013
Abstract This chapter illustrates the wide variety of binary fluid phase equilibrium diagrams tha... more Abstract This chapter illustrates the wide variety of binary fluid phase equilibrium diagrams that can be obtained using models based on equations of state (EOS). It also highlights the need for paying attention to the predicted binary key lines, such as the critical and the liquid–liquid–vapor equilibrium lines, when fitting binary interaction parameters of an EOS model. In addition, efficient algorithms for the EOS-based automated computation of complete Univariant Lines Phase Equilibrium Diagrams and of complete restricted binary phase equilibrium diagrams, such as isoplethic, isothermal, or isobaric diagrams, are described.
The application of high water-volatilities over some liquefied near-critical solvents as a means of dehydrating oxychemicals
The Journal of Supercritical Fluids, 1992
ABSTRACT The recovery of dehydrated products is an important feature in the supercritical-fluid e... more ABSTRACT The recovery of dehydrated products is an important feature in the supercritical-fluid extraction of oxychemicals from aqueous solutions. The dehydration takes place in the solvent recovery column if the mole fraction of water in the vapor exceeds that in the equilibrium liquid phase, that is, if the extraction solvent exhibits a “water entrainment” effect. Vapor-liquid equilibrium data for water-supercritical solvent systems are used to investigate this effect. A way of predicting the likely occurrence of the “entrainment” effect from binary data for the water/solvent systems is presented. This analysis shows that even for the binary case, carbon dioxide does not exhibit water entrainment. The influence of an alcohol on the entrainment effect was studied experimentally for two systems: i) isopropanol-water-propane; and ii) isopropanol-water-propylene. Even though there is a reduction of the entrainment effect in the presence of isopropanol, the entrainment effect was observed for both propylene and propane in the presence of significant amounts of alcohol. The data were compared with the predictions from the group contribution equation-of-state model. This model is found to over-predict the water volatilities in the systems studied.
The Journal of Supercritical Fluids, 2007
The use of propane + carbon dioxide mixtures can offer special properties regarding solvent power... more The use of propane + carbon dioxide mixtures can offer special properties regarding solvent power, selectivity and safety. In the present work, we studied the phase equilibrium engineering for the extraction of fixed oils from ground seeds. The selection of operating conditions is based on a ternary diagram that limits the region of complete miscibility and non-flammable mixtures. On the basis of the selected conditions, we carried out extraction experiments of soy oil, sunflower oil and hiprose oil from ground seeds. The extraction studies covered a range of propane + CO 2 solvent mixtures, at conditions of complete and/or partial miscibility with the oil. We observed that the oil extraction rate decreases as the CO 2 concentration in the solvent mixture increases, even in the region of complete solvent + oil miscibility. This behavior is explained on the basis of the effect of the thermodynamic properties of the oil + solvent solution on the mass transfer rate.
The Journal of Supercritical Fluids, 2006
Solvents like propane and carbon dioxide have been studied in previous works at supercritical and... more Solvents like propane and carbon dioxide have been studied in previous works at supercritical and subcritical conditions and also as highpressure liquid solvents for the extraction of lipids and oils. Propane is completely miscible with vegetable oils at room temperature but has liquid-liquid phase equilibrium with typical vegetable oils at temperatures between the lower critical end point (LCEP) and the upper critical end point (UCEP)-around 340 K and 370 K. In this temperature range, the propane solvent power for triglycerides is drastically reduced unless higher pressures are used to recover the single phase region. The use of propane + carbon dioxide mixtures can offer special properties regarding solvent power, selectivity and safety. In the present work experimental data on phase equilibria of sunflower oil + propane + carbon dioxide are measured in a windowed variable volume cell. The CO 2 concentration effect on the emergence of the liquid-liquid equilibrium phenomena in ternary mixtures with propane and oil is studied.
The Journal of Supercritical Fluids, 2012
In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundar... more In this work, we have obtained experimental cloud points, i.e., liquid-liquid equilibrium boundaries at constant composition, for the systems 'polybutadiene (PB) + n-pentane (C5)', 'PB + dimethyl ether (DME) + C5', 'polyethylene (PE) + DME + C5', and 'PB + PE + DME + C5'. The temperature range of the experiments was from 50 to 184 • C. The maximum pressure was 303 bar. In all cases the overall polymer concentration was less than or equal to 4.1 wt%. At the ranges of conditions of the experiments we have found the following: (a) For PB + C5, the minimum pressure required to guarantee homogeneity is 140 bar. (b) For 'PB + C5 + DME', the cloud point pressure (CPP) curves lie in between the CPP curves of 'PB + DME' and 'PB + C5', and the maximum CPP was 226 bar. The CPP increases with the increase of the DME/C5 ratio in the solvent mixture. (c) For 'PE + DME + C5', there is a substantial decrease in the CPPs with the addition of C5 to the DME + C5 solvent mixture, and the maximum CPP was 303 bar. (d) The CPPs for 'PB + PE + DME + C5' are higher than the CPPs of 'PB + DME + C5' but lower than the CPPs of 'PE + DME + C5'.
Journal of Chemical & Engineering Data, 2009
The use of mixed near-critical solvents such as CO 2 + propane, for vegetable oil extraction proc... more The use of mixed near-critical solvents such as CO 2 + propane, for vegetable oil extraction processes, has the advantage of the good solvent capacity of propane together with a nonflammable vapor phase due to the CO 2 content. The modeling of phase equilibria of these near-critical solvents with triglycerides using the GC-EOS model has been studied in several works; however, this model is not able to predict correctly the liquid-liquid-vapor region for mixtures of carbon dioxide and propane with triglycerides using the available group binary interaction parameters. In this work, new experimental phase equilibria data on the binary and ternary systems including CO 2 , propane, and triacetin are presented. These data are useful to properly assess the interaction parameters of CO 2 and propane with the triester group (TG) of the oil molecule. Liquid CO 2 is completely miscible with triacetin, and the addition of propane increases the liquid immiscibility of this ternary mixture. This is the opposite behavior presented by mixtures with long-chain triglycerides, in which addition of CO 2 increases liquid immiscibility.
Journal of Chemical & Engineering Data, 1996
Experimental liquid-liquid equilibrium data were obtained for systems containing water, NaCl, a l... more Experimental liquid-liquid equilibrium data were obtained for systems containing water, NaCl, a linear hydrocarbon solvent, a straight chain alcohol, and the two-tailed cationic surfactant dioctyldimethylammonium chloride (DODMAC). The experiments were carried out at 296.1 K and at atmospheric pressure. The solvents used were octane, decane, dodecane, tetradecane, and hexadecane. The alcohols utilized were 1-decanol and 1-dodecanol. High concentrations of water in the organic media and three phase transitions were observed for all solvent-alcohol combinations. The experimental results indicate the formation of water + hydrocarbon microemulsions for all systems.
Industrial & Engineering Chemistry Research, 2011
In this work, we evaluate the potential of a modeling approach for describing the solid-fluid equ... more In this work, we evaluate the potential of a modeling approach for describing the solid-fluid equilibria of highly asymmetric mixtures over a wide pressure range. The model uses a mathematical expression for the fugacity of a pure heavy compound in solid state for which the reference state is the saturated solid under conditions of solid-liquid (melting) equilibrium at the system temperature T. Such a reference state differs from a common choice, which corresponds to the pure solid under conditions of solid-vapor (sublimation) equilibrium at T. By construction, the present modeling approach matches the solidliquid equilibria at high concentration of the heavy component. We discuss and test here a parametrization strategy for avoiding the simultaneous correlation of fluid-fluid and solid-fluid experimental data: first, the fluid-fluid equilibrium experimental data are correlated in the conventional way, and next, the solid-fluid equilibrium data are correlated by fitting a parameter that has no influence on the equation of state that describes the fluid phases. In this work, we study in detail the highly asymmetric system methane þ n-triacontane, for which experimental data are available over a wide range of conditions (Machado, J. J. B.; de Loos, T. W. Liquid-vapour and solid-fluid equilibria for the system methane þ triacontane at high temperature and high pressure. Fluid Phase Equilib. 2004, 222-223, 261-267). To model this system, we use a specific form of the present modeling approach. Such a specific model gives a good quantitative performance even at pressures in the order of 2000 bar. We also present additional modeling results for two other systems, i.e., for methane þ n-eicosane and methane þ n-tetracosane, which are also highly asymmetric.
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Papers by Marcelo Santiago Zabaloy