Sagrario Beltrán | Universidad de Burgos (original) (raw)

Papers by Sagrario Beltrán

Analytica Chimica Acta, 2002

Several isolation and concentration methods have been developed for the analysis of volatile comp... more Several isolation and concentration methods have been developed for the analysis of volatile components in wine. However, it is generally admitted that none of them fulfill all the requirements for the isolation of aroma compounds and that it is necessary to combine different extraction methods to obtain the complete volatile fraction.

Macromolecules, 1991

Page 1. Macromolecules 1991,24, 549-551 549 Swelling Equilibria for Weakly Ionizable, Temperature... more Page 1. Macromolecules 1991,24, 549-551 549 Swelling Equilibria for Weakly Ionizable, Temperature-Sensitive Hydrogels Sagrario Beltran, John P. Baker, Herbert H. Hooper,' Harvey W. Blanch, and John M. Prausnitz' Chemical ...

Macromolecules, 1991

Monte Carlo simulations are employed to investigate the adsorption of a flexible linear cationic ... more Monte Carlo simulations are employed to investigate the adsorption of a flexible linear cationic polyelectrolyte onto a fluid mixed membrane containing neutral (phosphatidyl-choline, PC), multivalent (phosphatidylinositol, PIP(2)), and monovalent (phosphatidylserine, PS) anionic lipids. We systematically study the effect of chain length and charge density of the polyelectrolyte, the solution ionic strength, as well as the membrane compositions on the conformational and interfacial properties of the model system. In particular, we explore (i) the adsorption/desorption limit, (ii) the interfacial structure variations of the adsorbing polyelectrolyte and the lipid membrane, and (iii) the overcharging of the membrane. Polyelectrolyte adsorbs on the membrane when anionic lipid demixing entropy loss and polyelectrolyte flexibility loss due to adsorption are dominated by electrostatic attraction between polyelectrolyte and anionic lipids on the membrane. Polyelectrolytes with longer chain length and higher charge density can adsorb on the membrane with increased anionic lipid density under a higher critical ionic concentration. Below the critical ionic concentration, the adsorption extent increases with the charge density and chain length of the polyelectrolyte and decreases with the ionic strength of the solution. The diffusing anionic lipids prohibit the polyelectrolyte chain from forming too long tails. The adsorbing polyelectrolyte with long chain length and high charge density can overcharge a membrane with low charge density, and conversely, the membrane charge inversion forces the polyelectrolyte chain to form extended loops and tails in the solution.

Journal of Chromatography A, 1999

The different options MS detection are investigated in order to achieve the best conditions for d... more The different options MS detection are investigated in order to achieve the best conditions for detection and identification of anthocyanins by LC–MS. A method for separation of these compounds that enables the main molecules in wines to be identified by direct analysis, without any previous preparation, is proposed. The anthocyanin composition of different red grape skin extracts and commercial monovarietal

Journal of Chromatography A, 1999

Different options of liquid chromatography-mass spectrometry were used to establish the most suit... more Different options of liquid chromatography-mass spectrometry were used to establish the most suitable ion source and conditions to analyse or detect some low-molecular mass phenols, flavan-3-ols, and apply such conditions to a complex sample (wine). Data presented in this work confirm the great utility of atmospheric pressure-ionisation electrospray mass spectrometry coupled to HPLC for analysis of phenolic compounds, under negative mode in the case of low-molecular mass phenols, and under both positive and negative modes in flavan-3-ol compounds. A fragmentor voltage of 60 V could be the most suitable for analysing the compounds under study.

Process Biochemistry, 2002

The purpose of this investigation was to establish the antioxidant effect of flavonoid epicatechi... more The purpose of this investigation was to establish the antioxidant effect of flavonoid epicatechin (EC) a low concentration (0.75 μM). The relative antioxidant potentials were measured against radicals generated by tert-BOOH in isolated rat hepatocytes and calf thymus DNA. EC is an effective antioxidant, it completely prevents tert-BOOH induced oxidation and thereby prevents subsequent lipid peroxidation. It also plays an

European Journal of Nutrition, 2006

Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the gr... more Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the grape seed that contains different types of phenolic compounds. The present study was designed to evaluate the possible protective effect of DMGS on toxicity induced by adriamycin (ADR) in isolated rat hepatocytes. The study was carried out by examining the results of lactate dehydrogenase (LDH) release to estimate cytotoxicity; the thiobarbituric acid reactant substances (TBARS) and carbonyl group levels were measured as biomarkers of oxidative stress and ATP and GSH levels as estimation of intracellular effect. The results showed that DMGS extract protects the cellular membrane from oxidative damage and consequently prevents protein and lipid oxidation. The levels of ATP and GSH changes for the ADR toxicity were restored to control value in the presence of DMGS extract. The experimental results suggest that this wine by-product may be used to decrease oxidative stress.

Desalination, 2002

Membrane technologies are presented as alternative techniques to purify and fractionate extracts ... more Membrane technologies are presented as alternative techniques to purify and fractionate extracts from winery wastes with the aim of obtaining proanthocyanic fractions with different degrees of polymerization. These fractions, with the appropriate purity, have a great interest nutritionally and pharmacologically. To achieve different streams enriched in proanthocyanidins (PAs) with certain degree of condensation, several cross-flow filtration sequences using several polymeric membranes at different stages in the sequences were carried out. At the same time, several transmembrane pressures, concentrations and filtration designs (with or without diafiltration) were tested in tubular modules. A final sequence with four different membranes at the pilot-plant scale was achieved, which permitted us to obtain different fractions according to the molecular weight, some of them very pure in oligomeric PAs and, therefore, very interesting for the biotechnological industry. The raw material used in all cases was a hydroalcoholic extract from defatted milled grape seeds. Although no high yield was achieved in the whole process, the low value of this raw material (considered a waste in the winery industry) and the purity of the fractions obtained decrease the significance of the global yield.

Journal of Membrane Science, 2009

Pervaporation of the quaternary mixture involved in the synthesis of ethyl lactate, water/ethanol... more Pervaporation of the quaternary mixture involved in the synthesis of ethyl lactate, water/ethanol/ethyl lactate/lactic acid, has been investigated. Pervaporation experiments were performed with the commercial hydrophilic membrane PERVAP ® 2201 at 327.15 and 348.15 K. PERVAP ® 2201 membrane was previously tested for some of the binary mixtures present in the quaternary mixture showing high water selectivity. The effects of pervaporation temperature and water and lactic acid feed concentration on pervaporation performance have been studied in terms of permeation flux and permeance. The concentration range covered in this work was 12-63 wt% for water and 9-30 wt% for lactic acid. The permeation flux was found to increase with water feed concentration and temperature. However, the permeation flux was nearly constant when varying lactic acid concentration in the feed. Water permeance increased with water feed concentration but a slight dependence on temperature was observed.

Chemical Engineering Journal, 2007

The esterification of lactic acid with ethanol and the hydrolysis of the corresponding ester, eth... more The esterification of lactic acid with ethanol and the hydrolysis of the corresponding ester, ethyl lactate, have been studied in the presence of the commercial cation-exchange resin Amberlyst 15. The influence of different operating parameters such as stirrer speed, catalyst particle size, initial reactant molar ratio, reaction temperature and catalyst loading, has been examined. Additionally, the adsorption constants for the four components on Amberlyst 15 were determined by performing adsorption experiments between two non-reacting species. The values found for the adsorption constants follow the order: water > ethanol > lactic acid > ethyl lactate. Experimental kinetic data of the esterification and the hydrolysis reactions were correlated simultaneously with the Langmuir-Hinshelwood (LH) and pseudo-homogeneous (PH) models. The activity coefficients were calculated according to the UNIQUAC model. The LH model gave the best agreement with the kinetic experimental data. The activation energy of esterification and hydrolysis reactions were found to be 52.29 and 56.05 kJ mol −1 , respectively.

Journal of Chemical and Engineering Data, 2002

Isobaric vapor-liquid equilibrium data have been experimentally determined for the binary system ... more Isobaric vapor-liquid equilibrium data have been experimentally determined for the binary system methanol + methyl lactate at (33.33, 66.66, and 101.3) kPa. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC equations for the liquid-phase activity coefficients. The densities and derived excess volumes for the same mixture are also reported at 298.15 K.

Journal of Supercritical Fluids, 2006

A supercritical fluid extraction process for reducing the fat content of pigskin is presented in ... more A supercritical fluid extraction process for reducing the fat content of pigskin is presented in this work. Carbon dioxide has been used as supercritical solvent for fat extraction. Efficiencies close to 100% were reached. The influence of process parameters -such as extraction temperature, pressure and time and solvent ratio -on the extraction yield was studied. The influence of other variables such as initial fat and water content of the pigskin was also considered. The results showed that when using pigskin sheets, for non-interrupted extractions, there was an extraction yield limit, of around 60%, that could not be overcame even using an extraction pressure of 65 MPa. Some experiments that were interrupted for sampling of the pigskin showed that there was a positive influence of the intermediate depressurizations of the extractor on the extraction yield and, in this case, values close to 100% could be reached.

Journal of Chemical and Engineering Data, 2002

Isobaric vapor-liquid equilibrium data of the ternary system benzene + n-heptane + N-methylpyrrol... more Isobaric vapor-liquid equilibrium data of the ternary system benzene + n-heptane + N-methylpyrrolidone (NMP) have been measured with a Röck and Sieg recirculation still at 101.33 kPa. The experimental data reported were thermodynamically consistent when tested by the McDermott-Ellis method. Data were correlated with the Wilson and NRTL, equations for the liquid-phase activity coefficients. Activity coefficients of the components in the mixture indicate positive deviations from Raoult's law. Experimental results show that NMP is a good extractive solvent that reverses the volatility of the binary system benzene + n-heptane.

Journal of Chemical and Engineering Data, 2003

Isobaric vapor liquid equilibrium (VLE) data of the reactive quaternary system methanol (1) + wat... more Isobaric vapor liquid equilibrium (VLE) data of the reactive quaternary system methanol (1) + water (2) + methyl lactate (3) + lactic acid (4) are presented in this paper. The experimental data were correlated using the UNIQUAC model to describe the chemical and phase equilibrium. The UNIQUAC parameters for some of the binary, nonreactive systems involved in the quaternary mixture were obtained from published VLE data and, in the case of the system water + lactic acid, from experimental VLE data reported in this paper. The rest of the binary UNIQUAC parameters were obtained by an optimization of the correlation of the experimental quaternary VLE data. The results obtained from the correlation were found to be in good agreement with experimental data. The reaction equilibrium constant was also calculated for each experimental data point. A three-dimensional phase diagram was constructed for the quaternary reactive system by using transformed composition variables. No reactive azeotrope was found.

Journal of Chemical and Engineering Data, 2004

Chemical Engineering Journal

The synthesis of ethyl lactate from ethanol and lactic acid has been studied in a batch reactor c... more The synthesis of ethyl lactate from ethanol and lactic acid has been studied in a batch reactor combined with a pervaporation unit. The commercial acid resin Amberlyst 15 and the hydrophilic membrane PERVAP ® 2201 were used in the experiments. First esterification-pervaporation experiments were performed for dilute lactic acid aqueous solutions. Results show that the yield of ethyl lactate exceeds the corresponding thermodynamic equilibrium via selective removal of water from the reaction mixture through the membrane. If the process is performed sufficiently long, near total use of lactic acid could be reached. The water production and removal rates obtained from independent reaction and pervaporation experiments were used to simulate the behavior of the coupled system. The simulation results reveal the same trend observed in the experiments. The influence of different kinetic and pervaporation parameters such as initial reactant molar ratio, amount of catalyst, temperature and the ratio of membrane area/initial volume of reaction was analyzed in terms of ethyl lactate yield. For dilute lactic acid aqueous solutions the effect of catalyst loading has been found not to have a great influence, unlike the other parameters. Additionally the effect of the initial concentration of lactic acid aqueous solution was evaluated by performing experiments with different lactic acid aqueous solutions concentrations (20, 50 and 79-81 wt%). Initial water content has a great influence since total permeation is proportional to water concentration in the reactor.

Fluid Phase Equilibria, 2000

... the volatility of the binary system in such a way that the composition of the more volatile c... more ... the volatility of the binary system in such a way that the composition of the more volatile component (benzene) is higher in the liquid than in the vapor phase. That is, n-heptane would be obtained as the overhead product in the extractive distillation column, being benzene and ...

Journal of Supercritical Fluids, 2008

The supercritical fluid extraction (SFE) of the omega-3 rich oil contained in by-products of the ... more The supercritical fluid extraction (SFE) of the omega-3 rich oil contained in by-products of the fish industry has been studied in this work. Specifically, the offcuts obtained from peeling hake (Merluccius capensis-Merluccius paradoxus) to obtain hake fillets have been used as raw material. This raw material was grounded to different sizes and freeze-dried to different moisture contents. Extraction experiments were carried out at different pressure, flow rate and flow sense in order to study the influence of such process parameters on the extraction rate and oil quality. The influence of continuous or intermittent contact solvent-subtract was also evaluated. The extraction temperature was maintained at 40 • C in all cases in order to avoid thermal degradation of the polyunsaturated fatty acids contained in hake oil. The results obtained indicate that internal mass transfer controlled the rate of the process under the conditions studied in this work. The optimum extraction conditions were found to be 25 MPa, 10 kg CO 2 /h and upflow sense over freeze-dried and grounded hake. Under those conditions, more than 96% of the total oil contained in the raw material was extracted after 3 h. The oil extracted presented a high omega-3/omega-6 ratio (around 7) and a high EPA and DHA content (about 6% and 14%, respectively, of the total fatty acids contained in the hake by-product used in this work). Quality and stability of the hake oil were evaluated along 14 days of storage under different conditions. The acidity of hake oil obtained by SFE was high, but it was similar or even lower than the acidity of the oil obtained by conventional solvent extraction. Acidity suffered little further increment along storage. Hake oil was very prone to oxidative modification, enhanced by increasing temperature and light. The oil oxidation process is complex affecting the concentration of parameters related both with primary and secondary steps of oxidation and to sensory properties as smell and colour.

Fluid Phase Equilibria, 2007

... The total pressure of the system was monitored with a digital manometer and controlled to the... more ... The total pressure of the system was monitored with a digital manometer and controlled to the desired value (±0.09 kPa) by means of a pressure controller (Normastat 75). Temperature (±0.05 K) was measured with a digital thermometer (Ertco-Hart, Model 850). ...

Journal of Supercritical Fluids, 2003

The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3,... more The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3, 4-dihydroxycinnamic acid (caffeic acid), and 4-hydroxy-3-methoxycinnamic acid (ferulic acid), in supercritical carbon dioxide (SC-CO2) has been determined at different ...

Analytica Chimica Acta, 2002

Several isolation and concentration methods have been developed for the analysis of volatile comp... more Several isolation and concentration methods have been developed for the analysis of volatile components in wine. However, it is generally admitted that none of them fulfill all the requirements for the isolation of aroma compounds and that it is necessary to combine different extraction methods to obtain the complete volatile fraction.

Macromolecules, 1991

Page 1. Macromolecules 1991,24, 549-551 549 Swelling Equilibria for Weakly Ionizable, Temperature... more Page 1. Macromolecules 1991,24, 549-551 549 Swelling Equilibria for Weakly Ionizable, Temperature-Sensitive Hydrogels Sagrario Beltran, John P. Baker, Herbert H. Hooper,' Harvey W. Blanch, and John M. Prausnitz' Chemical ...

Macromolecules, 1991

Monte Carlo simulations are employed to investigate the adsorption of a flexible linear cationic ... more Monte Carlo simulations are employed to investigate the adsorption of a flexible linear cationic polyelectrolyte onto a fluid mixed membrane containing neutral (phosphatidyl-choline, PC), multivalent (phosphatidylinositol, PIP(2)), and monovalent (phosphatidylserine, PS) anionic lipids. We systematically study the effect of chain length and charge density of the polyelectrolyte, the solution ionic strength, as well as the membrane compositions on the conformational and interfacial properties of the model system. In particular, we explore (i) the adsorption/desorption limit, (ii) the interfacial structure variations of the adsorbing polyelectrolyte and the lipid membrane, and (iii) the overcharging of the membrane. Polyelectrolyte adsorbs on the membrane when anionic lipid demixing entropy loss and polyelectrolyte flexibility loss due to adsorption are dominated by electrostatic attraction between polyelectrolyte and anionic lipids on the membrane. Polyelectrolytes with longer chain length and higher charge density can adsorb on the membrane with increased anionic lipid density under a higher critical ionic concentration. Below the critical ionic concentration, the adsorption extent increases with the charge density and chain length of the polyelectrolyte and decreases with the ionic strength of the solution. The diffusing anionic lipids prohibit the polyelectrolyte chain from forming too long tails. The adsorbing polyelectrolyte with long chain length and high charge density can overcharge a membrane with low charge density, and conversely, the membrane charge inversion forces the polyelectrolyte chain to form extended loops and tails in the solution.

Journal of Chromatography A, 1999

The different options MS detection are investigated in order to achieve the best conditions for d... more The different options MS detection are investigated in order to achieve the best conditions for detection and identification of anthocyanins by LC–MS. A method for separation of these compounds that enables the main molecules in wines to be identified by direct analysis, without any previous preparation, is proposed. The anthocyanin composition of different red grape skin extracts and commercial monovarietal

Journal of Chromatography A, 1999

Different options of liquid chromatography-mass spectrometry were used to establish the most suit... more Different options of liquid chromatography-mass spectrometry were used to establish the most suitable ion source and conditions to analyse or detect some low-molecular mass phenols, flavan-3-ols, and apply such conditions to a complex sample (wine). Data presented in this work confirm the great utility of atmospheric pressure-ionisation electrospray mass spectrometry coupled to HPLC for analysis of phenolic compounds, under negative mode in the case of low-molecular mass phenols, and under both positive and negative modes in flavan-3-ol compounds. A fragmentor voltage of 60 V could be the most suitable for analysing the compounds under study.

Process Biochemistry, 2002

The purpose of this investigation was to establish the antioxidant effect of flavonoid epicatechi... more The purpose of this investigation was to establish the antioxidant effect of flavonoid epicatechin (EC) a low concentration (0.75 μM). The relative antioxidant potentials were measured against radicals generated by tert-BOOH in isolated rat hepatocytes and calf thymus DNA. EC is an effective antioxidant, it completely prevents tert-BOOH induced oxidation and thereby prevents subsequent lipid peroxidation. It also plays an

European Journal of Nutrition, 2006

Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the gr... more Defatted milled grape seed (DMGS) is a wine by-product obtained from the oil extraction of the grape seed that contains different types of phenolic compounds. The present study was designed to evaluate the possible protective effect of DMGS on toxicity induced by adriamycin (ADR) in isolated rat hepatocytes. The study was carried out by examining the results of lactate dehydrogenase (LDH) release to estimate cytotoxicity; the thiobarbituric acid reactant substances (TBARS) and carbonyl group levels were measured as biomarkers of oxidative stress and ATP and GSH levels as estimation of intracellular effect. The results showed that DMGS extract protects the cellular membrane from oxidative damage and consequently prevents protein and lipid oxidation. The levels of ATP and GSH changes for the ADR toxicity were restored to control value in the presence of DMGS extract. The experimental results suggest that this wine by-product may be used to decrease oxidative stress.

Desalination, 2002

Membrane technologies are presented as alternative techniques to purify and fractionate extracts ... more Membrane technologies are presented as alternative techniques to purify and fractionate extracts from winery wastes with the aim of obtaining proanthocyanic fractions with different degrees of polymerization. These fractions, with the appropriate purity, have a great interest nutritionally and pharmacologically. To achieve different streams enriched in proanthocyanidins (PAs) with certain degree of condensation, several cross-flow filtration sequences using several polymeric membranes at different stages in the sequences were carried out. At the same time, several transmembrane pressures, concentrations and filtration designs (with or without diafiltration) were tested in tubular modules. A final sequence with four different membranes at the pilot-plant scale was achieved, which permitted us to obtain different fractions according to the molecular weight, some of them very pure in oligomeric PAs and, therefore, very interesting for the biotechnological industry. The raw material used in all cases was a hydroalcoholic extract from defatted milled grape seeds. Although no high yield was achieved in the whole process, the low value of this raw material (considered a waste in the winery industry) and the purity of the fractions obtained decrease the significance of the global yield.

Journal of Membrane Science, 2009

Pervaporation of the quaternary mixture involved in the synthesis of ethyl lactate, water/ethanol... more Pervaporation of the quaternary mixture involved in the synthesis of ethyl lactate, water/ethanol/ethyl lactate/lactic acid, has been investigated. Pervaporation experiments were performed with the commercial hydrophilic membrane PERVAP ® 2201 at 327.15 and 348.15 K. PERVAP ® 2201 membrane was previously tested for some of the binary mixtures present in the quaternary mixture showing high water selectivity. The effects of pervaporation temperature and water and lactic acid feed concentration on pervaporation performance have been studied in terms of permeation flux and permeance. The concentration range covered in this work was 12-63 wt% for water and 9-30 wt% for lactic acid. The permeation flux was found to increase with water feed concentration and temperature. However, the permeation flux was nearly constant when varying lactic acid concentration in the feed. Water permeance increased with water feed concentration but a slight dependence on temperature was observed.

Chemical Engineering Journal, 2007

The esterification of lactic acid with ethanol and the hydrolysis of the corresponding ester, eth... more The esterification of lactic acid with ethanol and the hydrolysis of the corresponding ester, ethyl lactate, have been studied in the presence of the commercial cation-exchange resin Amberlyst 15. The influence of different operating parameters such as stirrer speed, catalyst particle size, initial reactant molar ratio, reaction temperature and catalyst loading, has been examined. Additionally, the adsorption constants for the four components on Amberlyst 15 were determined by performing adsorption experiments between two non-reacting species. The values found for the adsorption constants follow the order: water > ethanol > lactic acid > ethyl lactate. Experimental kinetic data of the esterification and the hydrolysis reactions were correlated simultaneously with the Langmuir-Hinshelwood (LH) and pseudo-homogeneous (PH) models. The activity coefficients were calculated according to the UNIQUAC model. The LH model gave the best agreement with the kinetic experimental data. The activation energy of esterification and hydrolysis reactions were found to be 52.29 and 56.05 kJ mol −1 , respectively.

Journal of Chemical and Engineering Data, 2002

Isobaric vapor-liquid equilibrium data have been experimentally determined for the binary system ... more Isobaric vapor-liquid equilibrium data have been experimentally determined for the binary system methanol + methyl lactate at (33.33, 66.66, and 101.3) kPa. All the experimental data reported were thermodynamically consistent according to the point-to-point method of Fredenslund. The activity coefficients were correlated with the NRTL and UNIQUAC equations for the liquid-phase activity coefficients. The densities and derived excess volumes for the same mixture are also reported at 298.15 K.

Journal of Supercritical Fluids, 2006

A supercritical fluid extraction process for reducing the fat content of pigskin is presented in ... more A supercritical fluid extraction process for reducing the fat content of pigskin is presented in this work. Carbon dioxide has been used as supercritical solvent for fat extraction. Efficiencies close to 100% were reached. The influence of process parameters -such as extraction temperature, pressure and time and solvent ratio -on the extraction yield was studied. The influence of other variables such as initial fat and water content of the pigskin was also considered. The results showed that when using pigskin sheets, for non-interrupted extractions, there was an extraction yield limit, of around 60%, that could not be overcame even using an extraction pressure of 65 MPa. Some experiments that were interrupted for sampling of the pigskin showed that there was a positive influence of the intermediate depressurizations of the extractor on the extraction yield and, in this case, values close to 100% could be reached.

Journal of Chemical and Engineering Data, 2002

Isobaric vapor-liquid equilibrium data of the ternary system benzene + n-heptane + N-methylpyrrol... more Isobaric vapor-liquid equilibrium data of the ternary system benzene + n-heptane + N-methylpyrrolidone (NMP) have been measured with a Röck and Sieg recirculation still at 101.33 kPa. The experimental data reported were thermodynamically consistent when tested by the McDermott-Ellis method. Data were correlated with the Wilson and NRTL, equations for the liquid-phase activity coefficients. Activity coefficients of the components in the mixture indicate positive deviations from Raoult's law. Experimental results show that NMP is a good extractive solvent that reverses the volatility of the binary system benzene + n-heptane.

Journal of Chemical and Engineering Data, 2003

Isobaric vapor liquid equilibrium (VLE) data of the reactive quaternary system methanol (1) + wat... more Isobaric vapor liquid equilibrium (VLE) data of the reactive quaternary system methanol (1) + water (2) + methyl lactate (3) + lactic acid (4) are presented in this paper. The experimental data were correlated using the UNIQUAC model to describe the chemical and phase equilibrium. The UNIQUAC parameters for some of the binary, nonreactive systems involved in the quaternary mixture were obtained from published VLE data and, in the case of the system water + lactic acid, from experimental VLE data reported in this paper. The rest of the binary UNIQUAC parameters were obtained by an optimization of the correlation of the experimental quaternary VLE data. The results obtained from the correlation were found to be in good agreement with experimental data. The reaction equilibrium constant was also calculated for each experimental data point. A three-dimensional phase diagram was constructed for the quaternary reactive system by using transformed composition variables. No reactive azeotrope was found.

Journal of Chemical and Engineering Data, 2004

Chemical Engineering Journal

The synthesis of ethyl lactate from ethanol and lactic acid has been studied in a batch reactor c... more The synthesis of ethyl lactate from ethanol and lactic acid has been studied in a batch reactor combined with a pervaporation unit. The commercial acid resin Amberlyst 15 and the hydrophilic membrane PERVAP ® 2201 were used in the experiments. First esterification-pervaporation experiments were performed for dilute lactic acid aqueous solutions. Results show that the yield of ethyl lactate exceeds the corresponding thermodynamic equilibrium via selective removal of water from the reaction mixture through the membrane. If the process is performed sufficiently long, near total use of lactic acid could be reached. The water production and removal rates obtained from independent reaction and pervaporation experiments were used to simulate the behavior of the coupled system. The simulation results reveal the same trend observed in the experiments. The influence of different kinetic and pervaporation parameters such as initial reactant molar ratio, amount of catalyst, temperature and the ratio of membrane area/initial volume of reaction was analyzed in terms of ethyl lactate yield. For dilute lactic acid aqueous solutions the effect of catalyst loading has been found not to have a great influence, unlike the other parameters. Additionally the effect of the initial concentration of lactic acid aqueous solution was evaluated by performing experiments with different lactic acid aqueous solutions concentrations (20, 50 and 79-81 wt%). Initial water content has a great influence since total permeation is proportional to water concentration in the reactor.

Fluid Phase Equilibria, 2000

... the volatility of the binary system in such a way that the composition of the more volatile c... more ... the volatility of the binary system in such a way that the composition of the more volatile component (benzene) is higher in the liquid than in the vapor phase. That is, n-heptane would be obtained as the overhead product in the extractive distillation column, being benzene and ...

Journal of Supercritical Fluids, 2008

The supercritical fluid extraction (SFE) of the omega-3 rich oil contained in by-products of the ... more The supercritical fluid extraction (SFE) of the omega-3 rich oil contained in by-products of the fish industry has been studied in this work. Specifically, the offcuts obtained from peeling hake (Merluccius capensis-Merluccius paradoxus) to obtain hake fillets have been used as raw material. This raw material was grounded to different sizes and freeze-dried to different moisture contents. Extraction experiments were carried out at different pressure, flow rate and flow sense in order to study the influence of such process parameters on the extraction rate and oil quality. The influence of continuous or intermittent contact solvent-subtract was also evaluated. The extraction temperature was maintained at 40 • C in all cases in order to avoid thermal degradation of the polyunsaturated fatty acids contained in hake oil. The results obtained indicate that internal mass transfer controlled the rate of the process under the conditions studied in this work. The optimum extraction conditions were found to be 25 MPa, 10 kg CO 2 /h and upflow sense over freeze-dried and grounded hake. Under those conditions, more than 96% of the total oil contained in the raw material was extracted after 3 h. The oil extracted presented a high omega-3/omega-6 ratio (around 7) and a high EPA and DHA content (about 6% and 14%, respectively, of the total fatty acids contained in the hake by-product used in this work). Quality and stability of the hake oil were evaluated along 14 days of storage under different conditions. The acidity of hake oil obtained by SFE was high, but it was similar or even lower than the acidity of the oil obtained by conventional solvent extraction. Acidity suffered little further increment along storage. Hake oil was very prone to oxidative modification, enhanced by increasing temperature and light. The oil oxidation process is complex affecting the concentration of parameters related both with primary and secondary steps of oxidation and to sensory properties as smell and colour.

Fluid Phase Equilibria, 2007

... The total pressure of the system was monitored with a digital manometer and controlled to the... more ... The total pressure of the system was monitored with a digital manometer and controlled to the desired value (±0.09 kPa) by means of a pressure controller (Normastat 75). Temperature (±0.05 K) was measured with a digital thermometer (Ertco-Hart, Model 850). ...

Journal of Supercritical Fluids, 2003

The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3,... more The solubility of three trans-hydroxycinnamic acids, 4-hydroxycinnamic acid (p-coumaric acid), 3, 4-dihydroxycinnamic acid (caffeic acid), and 4-hydroxy-3-methoxycinnamic acid (ferulic acid), in supercritical carbon dioxide (SC-CO2) has been determined at different ...