Equilibrium Solubility Of CO2 Research Articles

Measurement of carbon dioxide solubility in aqueous diisopropanolamine solutions blended by N-(2-aminoethyl) ethanolamine + piperazine and density measurement of solutions

The solubility of CO2 in the aqueous solutions of diisopropanolamine (DIPA) blended with N-(2-aminoethyl) ethanolamine (AEEA) and piperazine (Pz) is measured using a static equilibrium cell through a high pressure double-wall reactor. The different aqueous amine mixtures are used as the following compositions: DIPA (30 wt%), DIPA + AEEA (25, 5 wt%), DIPA + AEEA (20, 10 wt%), DIPA + AEEA + Pz (20, 5, 5 wt%). The solubility data are obtained at 313.15, 328.15, 343.15 K, and pressure range of 100–3800 kPa. The densities of these aqueous blends are also measured using a calibrated 5.7 ml pycnometer. Moreover, two simple correlations are proposed for the solution density versus temperature and the partial pressure of CO2 against gas loading. The solubility results are presented as the partial pressure of CO2 against its loading (mol CO2/mole total amine). It is found that the use of the AEEA and Pz as chemical activators for the DIPA solution lead to enhance the gas loading. On the other hand, the CO2 equilibrium solubility in the present alkanolamine mixtures enhances effectively with increasing pressure or decreasing temperature. Finally, the enthalpy of heat absorption of CO2 is calculated using Clausius-Clapeyron equation and is found that by enhancing the gas solubility the chemical absorption reduces, but the physical absorption intensifies at the gas loading higher than 0.9 so that AEEA needs more heating energy than DIPA and Pz at an amine regeneration column.

Characteristics of Potassium Prolinate + Water + Ethanol Solution as a Phase Changing Absorbent for CO2 Capture

Potassium prolinate + water + ethanol (ProK/W/Eth) solution has potential use as a liquid-to-solid phase-changing absorbent for energy-efficient CO2 capture process. In this study, the equilibrium solubility of CO2 in ProK/W/Eth solutions was measured in a stirred equilibrium cell at a temperature range from 293 to 343 K and CO2 partial pressures up to 200 kPa. Density and viscosity were also measured at temperatures from 293 to 333 K and ProK molality up to 6.09 mol·kg–1 ethanol. Moreover, the CO2 loading and cyclic capacity were compared with aqueous monoethanolamine (MEA) and aqueous ProK solution. The solubility data were well-represented using a Soft model with AAD within 8.0%. The data of density and viscosity were also correlated with empirical models. The predicted results matched well the experimental data with AAD within 0.37% for density and 1.38% for viscosity.

Analysis of CO2 Solubility and Absorption Heat into Aqueous 1-Diethylamino-2-propanol

In this work, the CO2 equilibrium solubility in 2M 1-diethylamino-2-propanol (1DEA2P) solution were determined as function of temperature (in the range of 298-333K), and CO2 partial pressure (in the range of 8-101kPa). The modified Li-shen K2 correlation model was also developed and used to predicate the CO2 equilibrium solubility in 1DEA2P solution. with an excellent ADD of 3.4%. The heat of CO2 absorption in 1DEA2P solution estimated using Gibbs-Helmholtz equation was found to be -45.7kJ/mol. In addition, the ion (1DEA2P, 1DEA2PH+, HCO3-, CO32−) speciation plots of the 1DEA2P-CO2-H2O system were developed in order to further understand the reaction process of 1DEA2P with CO2.

The Comparison of CO2 Absorption Performance between DEAPA (3-Diethylaminopropylamine) and Blends of MEA-MDEA

Amineaffects the absorption performance and energy cost forCO2 capture with chemical solvents. To searchthe desirable amine solvents with higher absorption rate andlower energy penalty would be a challenge task. In the presented study, the CO2 absorption performance for3-(Diethylamino)propylamine (DEAPA), a diamine that contains one primary and one tertiary amine in the same molecule, is investigated and compared with the blended amine system of Monoethanolamine and Methyldiethanolamine (MEA-MDEA), a mixed amine solvent of equal mole of primary and tertiary amine. The absorption rate and CO2 equilibrium solubility are tested for DEAPA (2M) and MEA-MDEA (4M,mole ratio=1:1), and the MEA is served as the base case. The experimental results show that the intramolecular tertiary amino group of DEAPA can promote the CO2 absorption rate of the intramolecular primary amino group and enhance its CO2 absorption capacity. The results from13C NMR technique also indicate that the intermolecular tertiary amine in MEA-MDEA system ismore favored to promote the primary amine in the blend to form the bicarbonate at an earlier CO2 equivalent loading stage and produce less carbamate than that of the intramolecular tertiary amino group of DEAPA to its primary amino group.

Vapor–Liquid Equilibrium and Physicochemical Properties of Novel Aqueous Blends of (2-Diethylaminoethanol + Piperazine) for CO2 Appropriation

Equilibrium solubility of CO2 in aqueous blends of 0.23 mol/kg piperazine (PZ) + 0.92 mol/kg 2-diethylaminoethanol (DEAE), 0.52 mol/kg PZ + 2.08 mol/kg DEAE, 0.92 mol/kg PZ + 3.68 mol/kg DEAE, and 1.49 mol/kg PZ + 5.96 mol/kg DEAE in the low pressure region of 0.1–65 kPa and at temperatures of 303.15–323.15 K is reported in the present article. A thermodynamic model is developed, which correlates the experimentally generated data on CO2 solubility in the newly proposed blend with an excellent agreement. Density and viscosity of DEAE + PZ + H2O have been measured at temperatures of 303.1–323.1 K and total amine mass percentage in all the blends are kept constant at 0.3. The mass % ratios of PZ/DEAE considered for measurements were 3:27, 6:24, 9:21, and 12:18. pKa of aqueous DEAE solution are reported in 298.15–333.15 K temperature range. Generated density data are correlated using Redlich–Kister equation, Grunberg and Nissan, and Gonzalez-Olmos, and Iglesias type models and viscosity data are correlated us...

Modeling of CO2 equilibrium solubility in a novel 1‐Diethylamino‐2‐Propanol Solvent

In this work, the equilibrium solubility of CO2 in a 1‐diethylamino‐2‐propanol (1DEA2P) solution was determined as a function of 1DEA2P concentration (over the range of 1–2 M), temperature (in the range of 298–333 K), and CO2 partial pressure (in the range of 8–101 kPa). These experimental results were used to fit the present correlation for K2 (Kent‐Eisenberg model, Austgen model, and Li‐Shen model). It was found that all of the models could represent the CO2 equilibrium solubility in 1DEA2P solution with ADDs for Kent‐Eisenberg model, Austgen model, and Li‐Shen model of 6.3, 7.3, and 12.2%, respectively. A new K2 correlation model, the Liu‐Helei model, was also developed to predict the CO2 equilibrium solubility in 1DEA2P solution with an excellent ADD of 3.4%. In addition, the heat of absorption of CO2 in 1DEA2P solution estimated by using the Gibbs‐Helmholtz equation was found to be −45.7 ± 3.7 kJ/mol. Information and guidelines about effectively using data for screened solvents is also provided based on the three absorption parameters: CO2 equilibrium solubility, second order reaction constant (k2), and CO2 absorption heat. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4465–4475, 2017

Thermodynamics and ANN models for predication of the equilibrium CO2 solubility in aqueous 3-dimethylamino-1-propanol solution

In this work, the CO2 equilibrium solubility of 3-dimethylamino-1-propanol (3DMA1P) is presented over the concentration range of 1–3mol/L, the temperature range of 298–333K, and the CO2 partial pressure of 3–101kPa. Several thermodynamic models (i.e. Kent-Eisenberg model, Austgen model, Hu-Chakma model, Liu et al. model) were used to correlate and predict the CO2 equilibrium solubility of 3DMA1P solution. It was found that the Liu et al. model could be considered to be an appropriate model to predict the CO2 equilibrium solubility in 3DMA1P solutions with an absolute average deviation (ADD) of 9.4%. In addition, the ANNs models (BPNN and RBFNN model) were developed and used to correlate the CO2 equilibrium solubility of 3DMA1P. It was found that the ANNs models could predict the experimental values very well with excellent ADDs of 3.0% for the BPNN model and 4.4% for the RBFNN model, respectively. In addition, a comparison of thermodynamic models and ANN models was presented in terms of prediction of CO2 solubility in 3DMA1P solution.

A Novel Model for Correlation and Predication of the Equilibrium CO2 Solubility in Seven Tertiary Solvents

In this work, the novel tertiary amines, 4-(dimethylamino)-2-butanol (DMAB), 4-(dipropylamino)-2-butanol (DPAB), 4-((2-hydroxyethyl)(methyl)amino)-2-butanol (HEMAB) and 4-((2-hydroxyethyl)(ethyl)amino)-2-butanol (HEEAB), 1-(2-Hydroxyethyl)-piperidine (1-(2-HE)PP), 1-(2-Hydroxyethyl)pyrrolidine (1-(2-HE)PRLD) and 3-diethylamino-1,2-propanediol (DE-1,2-PD) were synthesized or screened to reduce energy requirement of PCC to 2.0GJ/ton CO2. The CO2 equilibrium solubility of those solvents were provided. A new K2 correlation model, Liu et al. model, was also developed to correlate and predict the CO2 equilibrium solubility in those new amines solution. It was found that the new model could fit the CO2 equilibrium solubility in those newly solution with absolute average deviations (ADDs) for DMAB, DPAB, HEMAB, HEEAB, 1-(2-HE)PP, 1-(2-HE)PRLD, DE-1,2-PD of 5.4%, 24.7%, 8.3%, 4.2%, 1.7%, 4.1%, and 2.3%, respectively.

CO2 capture with aqueous solution of sodium glycinate: Modeling using an ensemble method

As a type of amino acid salt, sodium glycinate (SG) is introduced as a potential solvent for CO2 capture from gas streams like sour natural gas and flue gas. Modeling and assessment of the experimental data of CO2 loading capacity of SG aqueous solution are the main objectives of the present study. To this end, a well-known ensemble method namely the Adaptive Boosting (AdaBoost) technique was utilized in conjunction with the Classification and Regression Tree (CART) algorithm for modeling the CO2 solubility in SG solution as a function of the temperature of the system, CO2 partial pressure, and concentration of SG in the aqueous phase. Then, the Leverage method was employed for investigating the range of applicability of the developed model and quality of the collected experimental data. Furthermore, the AdaBoost-CART was compared to multilayer artificial neural network (MLP-ANN) and least squares support vector machine (LSSVM). It was found that the presented AdaBoost-CART model provides more accurate predictions and has a wide range of applicability. Furthermore, the results suggest that among all the gathered data, six experimental equilibrium CO2 solubility in SG solution are probable outliers.

A new model for correlation and prediction of equilibrium CO2 solubility in N‐methyl‐4‐piperidinol solvent

In this work, the equilibrium CO2 solubility in the aqueous tertiary amine, N‐methyl‐4‐piperidinol (MPDL) was measured over a range of temperatures, CO2 partial pressures and amine concentrations. The dissociation constant of the MPDL solution was determined as well. A new thermodynamic model was developed to predict the equilibrium CO2 solubility in the MPDL‐H2O‐CO2 system. This model, equipped with the correction factor (Cf), can give reasonable prediction with an average absolute deviation of 2.0%, and performs better than other models (i.e., KE model, Li‐Shen model, and Hu‐Chakma). The second‐order reaction rate constant (k2) of MPDL and the heat of CO2 absorption (–ΔHabs) into aqueous MPDL solutions were evaluated as well. Based on the comparison with some conventional amines, MPDL revealed a high‐equilibrium CO2 loading, reasonably fast absorption rate when compared with other tertiary amines, and a low energy requirement for regeneration. It may, therefore, be considered to be an alternative solvent for CO2 capture. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3395–3403, 2017

Experimental study and modeling of CO2 absorption into diethanolamine solutions using stirrer bubble column

In this work, solubility and chemical absorption rate of carbon dioxide into aqueous solutions of diethanolamine (DEA) were studied in a stirred bubble column. In the experiments the effects of stirrer speed, amine concentration, CO2 partial pressure and CO2 loading on absorption rate and solubility were investigated. The experimental conditions are, amine concentration in range of 0.2–2.0M, CO2 partial pressures in range of 2.4–3.6kPa, stirrer speed in range of 0–600rpm, CO2 loading in range of 0.1–0.7mole of CO2 per mole of amine. The results showed that mass transfer flux and absorption percent of CO2 were varied in range of 34–59% and 0.35–4.32kmolm−2s−1, respectively. A thermodynamic model, based on Deshmukh and Mather model is proposed for the equilibrium solubility of CO2 in DEA solutions. It has been found that this model is able to estimate results which are close to the experimental data in terms of the total CO2 loadings of the solution. Predicted partial pressures of the CO2 over diethanolamine solution were also observed good deal with experimental data.

Analysis of CO2 solubility and absorption heat into 1-dimethylamino-2-propanol solution

In this work, the CO2 equilibrium solubility in 1-dimethylamino-2-propanol (1DMA2P) solution was determined as a function of 1DMA2P concentration (over the range of 1–5M), temperature (in the range of 298–333K), and CO2 partial pressure (in the range of 8–101kPa), and the data used to fit the correlations for K2 using Kent-Eisenberg, Austgen, Li-Sheng and Hu-Chakma models. A new K2 correlation model was also developed to predict the CO2 equilibrium solubility in 1DMA2P solution. It was found that all of the models could fit the CO2 equilibrium solubility in 1DMA2P solution data with absolute average deviations (ADDs) for the models by Kent-Eisenberg, Austgen, Li-Sheng, Hu-Chakma and Liu et al. of 14, 15, 12, 6.3 and 10%, respectively. In addition, the heat of CO2 absorption in 1DMA2P solution estimated using Gibbs-Helmholtz equation was found to be −31.67kJ/mol. Information or guidelines about effective utilization of data of screened solvents is provided based on three absorption parameters, namely, CO2 equilibrium solubility, second order reaction constant, and CO2 absorption heat.

Screening tests of aqueous alkanolamine solutions based on primary, secondary, and tertiary structure for blended aqueous amine solution selection in post combustion CO2 capture

In this work, hindered primary, secondary and tertiary aqueous alkanolamine solutions with different numbers of hydroxyl groups were investigated for their initial rates of absorption and desorption which show how fast the amine solution will reach equilibrium and will be regenerated, respectively, and also investigated pKa, equilibrium solubility of CO2, heat duty (Qreg) for solvent regeneration, and heat of CO2 absorption (ΔHabs). These experimental data were used as a screening tool to enable the selection of the best amine components for designing an optimal blended aqueous amine solution system. The absorption experiments were performed at 313K and atmospheric pressure using 15% CO2 (in N2 balance) as feed gas whereas desorption experiments were performed at 363K and atmospheric pressure. Alkanolamines with a larger number of hydroxyl groups exhibited lower performance in all the CO2 capture activities because of the negative electron withdrawing effect of the hydroxyl group. Consequently, based on the results of individual primary, secondary, and tertiary aqueous alkanolamine solutions, the ones with only one hydroxyl group (2-amino-2-methyl-1-propanol (AMP), 2-(ethylamino) ethanol (EAE), and 2-(dimethylaminoethanol) (DMAE)) were selected for formulation into aqueous amine blends. Two binary aqueous amine blends of AMP/DMAE and EAE/DMAE and one ternary aqueous amine blend of AMP/EAE/DMAE at various molar ratios were tested. All solvent combinations showed better performance than 5M MEA, especially in the initial desorption rate and energy efficiency. Of these aqueous amine blends, the 2.5M AMP/2.5M DMAE exhibited the best performance with an equilibrium CO2 solubility of 0.56mol CO2/mol amine, initial absorption rate of 0.26×10−2mol CO2/min, initial desorption rate of 2.62×10−2mol CO2/min, and heat duty of 53.81kJ/mol.

The analysis of solubility, absorption kinetics of CO2 absorption into aqueous 1‐diethylamino‐2‐propanol solution

In this present work, the CO2 absorption performance of aqueous 1‐diethylamino‐2‐propanol (1DEA2P) solution was studied with respect to CO2 equilibrium solubility, absorption kinetics, and absorption heat. The equilibrium solubility of CO2 in 2M 1DEA2P solution was measured over the temperature range from 298 to 333 K and CO2 partial pressure range from 8 to101 kPa. The absorption kinetics data were developed and analyzed using the base‐catalyzed hydration mechanism and artificial neural network models (radial basis function neural network [RBFNN] and back‐propagation neural network [BPNN] models) with an acceptable absolute average deviation of 10% for base‐catalyzed hydration mechanism, 2.6% for RBFNN model and 1.77% for BPNN model, respectively. The CO2 absorption heat of 1DEA2P was estimated to be −43.6 kJ/mol. In addition, the ions (1DEA2P, 1DEA2PH+, , CO32−) speciation plots of the 1DEA2P‐CO2‐H2O system were developed to further understand the reaction process of 1DEA2P with CO2. Based on a comparison with conventional amines (e.g., MEA, DEA, MDEA) and alternative amines (i.e., 1DMA2P and 4‐(diethylamino)−2‐butanol [DEAB]), 1DEA2P exhibited good performance with respect to CO2 equilibrium solubility, reaction kinetics, and CO2 absorption heat. Meanwhile, the overall evaluation of 1DEA2P for application in CCS in terms of absorption and desorption is presented, giving helpful information for the screening of these novel amines. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2694–2704, 2017

Analysis of solubility, absorption heat and kinetics of CO2 absorption into 1-(2-hydroxyethyl)pyrrolidine solvent

The CO2 absorption performance of aqueous 1-(2-hydroxyethyl)pyrrolidine (1-(2-HE)PRLD) was studied with respect to kinetics (i.e., in terms of the pseudo-first-order rate constant (ko) and second-order reaction rate constant (k2), obtained using the stopped-flow apparatus). CO2 equilibrium solubility and heat of CO2 absorption were evaluated at the temperature range of 293–313K in the 1-(2-HE)PRLD concentration range of 0.20–1.00mol/L for kinetics and at 2M for CO2 solubility. The values of ko were then represented using the base-catalyzed hydration mechanism, which gave an acceptable AAD of 10%. In addition, Brønsted plots of k2 vs. pKa were developed to predict k2 using pKa values of various tertiary amines. In addition, the CO2 equilibrium solubility and CO2 absorption heat were obtained in this work. Based on a comparison with other amines such as MEA, MDEA and 1DMA2P, 1-(2-HE)PRLD showed better performance in terms of CO2 equilibrium solubility (DEAB>1-(2-HE)PRLD>1-(2HE)PP>1DMA2P>MDEA>MEA>DEA), kinetics (MEA>DEA>DEAB>1-(2-HE)PRLD>1-(2-HE)PP>DMMEA>1DMA2P>MDEA.) and CO2 absorption heat (MEA>DEA>MDEA>DEAB>1-(2-HE)PRLD>1-(2HE)PP>1DMA2P). Therefore, 1-(2-HE)PRLD could be considered as a good alternative solvent for CO2 capture. A correlation between kinetics and heat of CO2 absorption has been developed to guide the design of what can be considered to be ideal amine solvents for CO2 capture.

VLE of CO2 in aqueous potassium salt of L-phenylalanine: Experimental data and modeling using modified Kent-Eisenberg model

In this study, vapor-liquid equilibrium (VLE) of CO2 in aqueous potassium salt of l-phenylalanine (K-Phe) was investigated. A high pressure solubility cell was used to measure the solubility of CO2 in aqueous solution of (10, 20 and 25) wt% K-Phe at 303.15, 313.15 and 333.15 K over a CO2 pressure range of 200–2500 kPa. Equilibrium CO2 solubility was defined in terms of CO2 loading (mole CO2/mole of amine). The effect of temperature, concentration and equilibrium CO2 pressure on CO2 loading was discussed. Experimental CO2 loading data in aqueous K-Phe solutions show that the solvent has good potential for CO2 capture systems. Also, a modified Kent-Eisenberg model was used to correlate the experimental CO2 solubility data and carbamate hydrolysis and amine deprotonation equilibrium constants were regressed as a function of temperature, concentration and equilibrium CO2 pressure. An average absolute deviation of 7.70% between experimental and predicted data indicated the good prediction capability of the applied thermodynamic model.

Carbon dioxide loading capacity in aqueous solution of Potassium salt of Proline blended with Piperazine as new absorbents

In this work aqueous solution of potassium prolinate (KPr) blended with piperazine (PZ) have been utilized through CO2 solubility measurements in order to investigate the possible use of these salts of amino acid blended with alkanolamine for CO2 absorption. The equilibrium solubility of CO2 for KPr blended with PZ solutions at 1.0, 4.0 and 10.0wt.% overall mass concentration is experimentally measured with an equilibrium cell at CO2 partial pressure ranging from 4.8 to 2383.2kPa and temperatures between 293.15 and 323.15K. Obtained data showed that loading capacity decreases with an increase in temperature and concentration of KPr. Obtained CO2 loadings are very high at low concentration of KPr. In order to predict CO2 solubility in KPr blended with PZ, Deshmkh-Mather model is extended. The values of MSE, ARD and R2 for the extended Deshmukh-Mather model are 0.0363, 10.7770 and 0.9844, respectively.

Experimental and theoretical study of carbon dioxide solubility in aqueous solution of potassium glycinate blended with piperazine as new absorbents

In this work aqueous solution of potassium glycinate, piperazine and potassium glycinate blended with piperazine have been utilized through CO2 solubility measurements in order to investigate the possible use of these salts of amino acid blended with alkanolamine for CO2 absorption. The equilibrium solubility of CO2 for aqueous solutions of potassium glycinate, piperazine and potassium glycinate blended with piperazine at 1.0, 4.0 and 10.0wt.% overall mass concentration are experimentally measured with an equilibrium cell at CO2 partial pressure ranging from 5.1 to 2508.7kPa and temperatures between 293.15 and 323.15K. Obtained data show that loading capacity decreases with increase in temperature and concentration of potassium glycinate and potassium glycinate blended with piperazine. Obtained CO2 loadings are very high at low concentration of potassium glycinate. In order to predict CO2 solubility in aqueous solutions potassium glycinate, piperazine and potassium glycinate blended with piperazine, Deshmkh-Mather model is extended. The values of MSE, ARD and R2 for the extended Deshmukh-Mather model are 0.0741, 8.9582 and 0.9826, respectively. In addition, an artificial neural network (ANN) is developed to predict CO2 solubility in aqueous solutions of piperazine, potassium glycinate and potassium glycinate blended with piperazine. The values of MSE, ARD and R2 for the optimal trained ANN are 0.0179, 4.1528 and 0.9962, respectively.

Characterization of monoethanolamine + potassium lysinate blend solution as a new chemical absorbent for CO2 capture

Selection of an appropriate absorbent can provide a potential breakthrough for the chemical absorption method. In this study, after a prescreening, potassium lysinate (PL), an amino acid with high loading capacity, has been selected to blend with monoethanolamine (MEA), an industrial absorbent with high reaction rate, to improve the performance of MEA for CO2 removal. To evaluate the effect of the addition of PL to MEA in terms of loading capacity, the equilibrium solubility of CO2 in MEA+PL blend solutions was determined experimentally by using a Vapor-Liquid Equilibrium (VLE) at total blend concentration (CT) 2.5mol/L in temperatures between 303 and 323K and CO2 partial pressure ranging from 0 to 50kPa. For further investigation, the density, viscosity (from 303 to 323K) and corrosion rate (at 313K) of blend solutions were also determined. The obtained results indicated that the loading capacity and corrosion rate of blend solutions increase as the blend ratio of PL/MEA increases while viscosity decreases.

Foaming of polymers with supercritical fluids: A thermodynamic investigation

The foaming of polymers using supercritical fluids was investigated, both, from a theoretical and an experimental point of view. Key thermodynamic phenomena that take place during the foaming process were described using the Non Random Hydrogen Bonding (NRHB) equation-of-state, such as the supercritical fluid solubility in the polymer matrix and the plasticization profile of the polymer–supercritical fluid system. Moreover, the NRHB model was combined with the classical nucleation theory in order to describe the energy barrier for nucleation. Subsequently, the foaming of the well-defined polystyrene–CO2 system was experimentally studied. Porous polystyrene structures were prepared using supercritical CO2 as foaming agent at various pressure and temperature conditions that refer to constant amount of dissolved fluid (CO2) inside the polymer matrix, or to constant initial energy barrier for nucleation. The experimental results, which were discussed in the light of the aforementioned theoretical investigation, reveal that at pressure and temperature conditions of constant equilibrium solubility of CO2 inside the polymer matrix, the average pore diameter decreases with increasing foaming temperature, mainly due to the formation of more pores, which is a consequence of the decrease in the energy barrier for nucleation. Furthermore, at conditions that refer to constant initial energy barrier for nucleation, all the produced porous structures presented similar pore diameters and cell population densities, regardless of the foaming temperature. Finally, it is concluded that the energy barrier for nucleation determines the morphology of the final porous structure to a large extent, although other processing parameters, such as the foaming temperature (or pressure) and the amount of the dissolved fluid, may also influence the cell size.