Separation of H2O/CO2 Mixtures by MFI Membranes: Experiment and Monte Carlo Study

The separation of CO2 from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO2. In this work, the applicability of MFI membranes for H2O/CO2 separation is principally demonstrated by means of realistic adsorption isotherms computed by configurational-biased Monte Carlo (CBMC) simulations, then parameters such as temperatures, pressures and compositions were identified at which inorganic membranes with high selectivity can separate hot water vapour and thus make it available for recycling. Capillary condensation/adsorption by water in the microporous membranes used drastically reduces the transport and thus the CO2 permeance. Thus, separation factors of αH2O/CO2 = 6970 could be achieved at 70 °C and 1.8 bar feed pressure. Furthermore, the membranes were tested for stability against typical amines used in gas scrubbing processes. The preferred MFI membrane showed particularly high stability under application conditions

A simple guiding principle for the temperature dependence of the solubility of light gases in imidazolium-based ionic liquids derived from molecular simulations

We have determined the temperature dependence of the solvation behavior of a large collection of important light gases in imidazolium-based ionic liquids with the help of extensive molecular dynamics simulations. The motivation of our study is to unravel common features of the temperature dependent solvation under well controlled conditions, and to provide a guidance for cases, where experimental data from different sources disagree significantly. The solubility of molecular hydrogen, oxygen, nitrogen, methane, krypton, argon, neon and carbon dioxide in the imidazolium based ionic liquids of type 1-n-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Cnmim][NTf2]) with varying alkyl side chain lengths n = 2, 4, 6, 8 is computed for a temperature range between 300 K and 500 K at 1 bar. By applying Widom's particle insertion technique and Bennet's overlapping distribution method, we are able to determine the temperature dependent solvation free energies of those selected light gases in simulated imidazolium based ionic liquids with high statistical accuracy. Our simulations demonstrate that the magnitude of the solvation free energy of a gas molecule at a chosen reference temperature and that of its temperature-derivatives are intimately related to one another. We conclude that this "universal" behavior is rooted in a solvation entropy-enthalpy compensation effect, which seems to be a defining feature of the solvation of small molecules in ionic liquids. The observations lead to simple analytical relations, determining the temperature dependence of the solubility data based on the absolute solubility at a certain reference temperature. By comparing our results with available experimental data from many sources, we can show that our approach is particularly helpful for providing reliable estimates for the solvation behavior of very light gases, such as hydrogen, where conflicting experimental data exist

Exploring the Potential of a Highly Scalable Metal-Organic Framework CALF-20 for Selective Gas Adsorption at Low Pressure

In this study, the ability of the highly scalable metal-organic framework (MOF) CALF-20 to adsorb polar and non-polar gases at low pressure was investigated using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results from the simulated adsorption isotherms revealed that the highest loading was achieved for SO2 and Cl2, while the lowest loading was found for F2 molecules. The analysis of interaction energies indicated that SO2 molecules were able to form the strongest adsorbent-adsorbate interactions and had a tight molecular packing due to their polarity and angular structure. Additionally, Cl2 gas was found to be highly adsorbed due to its large van der Waals surface and strong chemical affinity in CALF-20 pores. MD simulations showed that SO2 and Cl2 had the lowest mobility inside CALF-20 pores. The values of the Henry coefficient and isosteric heat of adsorption confirmed that CALF-20 could selectively adsorb SO2 and Cl2. Based on the results, it was concluded that CALF-20 is a suitable adsorbent for SO2 and Cl2 but not for F2. This research emphasizes the importance of molecular size, geometry, and polarity in determining the suitability of a porous material as an adsorbent for specific adsorbates

Separation of H2O/CO2 Mixtures by MFI Membranes: Experiment and Monte Carlo Study

The separation of CO2 from gas streams is a central process to close the carbon cycle. Established amine scrubbing methods often require hot water vapour to desorb the previously stored CO2. In this work, the applicability of MFI membranes for H2O/CO2 separation is principally demonstrated by means of realistic adsorption isotherms computed by configurational-biased Monte Carlo (CBMC) simulations, then parameters such as temperatures, pressures and compositions were identified at which inorganic membranes with high selectivity can separate hot water vapour and thus make it available for recycling. Capillary condensation/adsorption by water in the microporous membranes used drastically reduces the transport and thus the CO2 permeance. Thus, separation factors of αH2O/CO2 = 6970 could be achieved at 70 °C and 1.8 bar feed pressure. Furthermore, the membranes were tested for stability against typical amines used in gas scrubbing processes. The preferred MFI membrane showed particularly high stability under application conditions

Molecular dynamics simulation of Pt@Au nanoalloy in various solvents: Investigation of solvation, aggregation, and possible coalescence

In this study, a pair of core-shell Pt@Au nanoalloy particles with 309 atoms was simulated in various solvents, including water, benzene, ethanol, water + benzene, and 1-butyl-1,1,1-trimethylammonium methanesulfonate [N1114][C1SO3] ionic liquid (IL) at 300 K and 1 atm. We investigated the aggregation and possible coalescence of Au–Pt nanoalloys based on various thermodynamic, dynamic, and structural simulation results. The findings from our study demonstrated that the tendency for aggregation of nanoalloys is greater in water and benzene + water systems than in other solvents. This tendency is weaker in the solvents such as IL, ethanol, and benzene (weakest in benzene). Our results also showed that there is a very small change in the structure of the nanoalloys in the different solvents even after 100 ns of simulation time. Furthermore, coalescence does not occur between the two (Pt@Au)309 nanoalloys. Our results also indicated that the nanoalloys have lower solvation energy in water than in the other solvents. It is also found that IL has a higher solvation energy compared to other solvents. The dynamic results indicated that the (Pt@Au)309 nanoalloys have higher self-diffusion coefficients in benzene and lower diffusion values in IL. Furthermore, we examined the effects of nanocluster shape and core by simulating truncated octahedral (Au)374 and pure icosahedral (Au)309 nanoclusters in water. The results showed that despite the (Pt@Au)309 nanoalloy, the two pure icosahedral (Au)309 nanoclusters approached each other, and coalescence occurred

Methylene diisocyanate - aided tailoring of nanotitania for dispersion engineering through polyurethane mixed matrix membranes: Experimental investigations

The present focus of environmental science is centred on addressing the significant and controversial challenge of separating acid gases. As a result, scientists are actively engaged in developing high-performance membranes that can effectively transport gases. An important factor in achieving superior gas separation efficiency is the ability to control the rate of chemical component penetration through the membrane. This has led to an increasing interest in mixed matrix membranes (MMMs) that contain inorganic nanoparticles homogeneously dispersed within the polymer matrix, which are becoming a popular alternative to traditional polymeric membranes. In this work, the morphological properties of polyurethane (PU) membrane treated with titanium dioxide (TiO2), which is functionalized with methylene diisocyanate (MDI), were studied, and its gas transport properties, like selectivity and permeability, were evaluated. FTIR, XRD, TG, DTG, and SEM analyses were performed for neat and MMMs to study their morphological properties in phase I of the research. Our results showed that MDI modification improved the dispersion of TiO2 in the PU matrix, resulting in a more uniform and compact membrane structure. Moreover, gas permeability results showed that incorporating up to 1 wt% of unfunctionalized and functionalized TiO2 into the PU matrix enhanced the CO2/N2 selectivity by 71.69% and 78.42%, respectively. Overall, this study demonstrated the potential of MDI-aided tailoring of TiO2 for dispersion engineering in PU MMMs, which can lead to improved gas separation performance. The findings have implications for developing advanced materials for gas separation applications, particularly in industrial processes such as natural gas purification and carbon capture

Exploring the Potential of a Highly Scalable Metal-Organic Framework CALF-20 for Selective Gas Adsorption at Low Pressure

In this study, the ability of the highly scalable metal-organic framework (MOF) CALF-20 to adsorb polar and non-polar gases at low pressure was investigated using grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulations. The results from the simulated adsorption isotherms revealed that the highest loading was achieved for SO2 and Cl2, while the lowest loading was found for F2 molecules. The analysis of interaction energies indicated that SO2 molecules were able to form the strongest adsorbent-adsorbate interactions and had a tight molecular packing due to their polarity and angular structure. Additionally, Cl2 gas was found to be highly adsorbed due to its large van der Waals surface and strong chemical affinity in CALF-20 pores. MD simulations showed that SO2 and Cl2 had the lowest mobility inside CALF-20 pores. The values of the Henry coefficient and isosteric heat of adsorption confirmed that CALF-20 could selectively adsorb SO2 and Cl2. Based on the results, it was concluded that CALF-20 is a suitable adsorbent for SO2 and Cl2 but not for F2. This research emphasizes the importance of molecular size, geometry, and polarity in determining the suitability of a porous material as an adsorbent for specific adsorbates