Computing solubility and thermodynamic properties of H2O2 in water

Hydrogen peroxide plays a key role in many environmental and industrial chemical processes. We performed classical Molecular Dynamics and Continuous Fractional Component Monte Carlo simulations to calculate thermodynamic properties of H2O2 in aqueous solutions. The quality of the available force fields for H2O2 developed by Orabi and English (2018) [67], and by Cordeiro (2014) [69] was systematically evaluated. To assess which water force field is suitable for predicting properties of H2O2 in aqueous solutions, four widely used water force fields were used, namely the TIP3P, TIP4P/2005, TIP5P-E, and a modified TIP3P force field. While the computed densities of pure H2O2 in the temperature range of 253 - 353 K using the force field by Orabi & English are in excellent agreement with experimental results, the densities using the force field by Cordeiro are underestimated by 3%. The TIP4P/2005 force field in combination with the H2O2 force field developed by Orabi & English can predict the densities of H2O2 aqueous solution for the whole range of H2O2 mole fractions in very good agreement with experimental results. The TIP4P/2005 force field in combination with either of the H2O2 force fields can predict the viscosities of H2O2 aqueous solutions for the whole range of H2O2 mole fractions in reasonably good agreement with experimental results. The computed diffusion coefficients for H2O2 and water molecules using the TIP4P/2005 force field with either of the H2O2 force fields are almost constant for the whole range of H2O2 mole fractions. Hydrogen bond analysis showed a steady increase in the number of hydrogen bonds with the solute concentrations in H2O2 aqueous solutions for all combinations except for the Cordeiro-TIP5P-E and Orabi-TIP5P-E systems, which showed a minimum at intermediate concentrations. The Cordeiro force field for H2O2 in combination with either of the water force fields can predict the Henry coefficients of H2O2 in water in better agreement with experimental values than the force field by Orabi & Englis

Molecular Mechanisms for Adsorption in Cu-BTC Metal Organic Framework

We use molecular simulations to analyze the preferential adsorption sites of molecules that differ in size, shape, and polarizability in Cu-BTC metal organic framework. The cage system of the framework can be exploited to enhance adsorption of small gases. We find that nonpolar molecules adsorb preferentially in the small tetrahedral cages, whereas alcohols and water molecules adsorb close to the copper atoms in one of the big cages. Blocking potentially enhances selective adsorption and separation and we therefore investigate how to block these cages in a practical manner. We propose to use ionic liquids for it and we find that the addition of these components reduces the adsorption of polar molecules near the open metal centers. For this reason, the presence of ionic liquids reduces the attack of the molecules of water to the metallic centers improving the framework stability

Micelle Formation in Aqueous Solutions of Room Temperature Ionic Liquids: A Molecular Dynamics Study

1-Alkyl-3-methylimidazolium cations in the presence of water are used as a test system to study by molecular dynamics the formation of micelles in aqueous mixtures of highly anisotropic room temperature ionic liquids (IL). Structural properties, i.e., radial distribution functions (RDF) and transport parameters, such as diffusion coefficients and conductivities, are computed as a function of the IL/water mole fraction. The concentration plots reveal a sharp change of the slope of both the cation self-diffusion coefficient and the first peak of the head–head RDF at approximately the same value of the concentration. This transition, considered as a measure of a critical micellar concentration, appears only for the most anisotropic systems, composed of longer alkyl chains. The formation of the micelles is confirmed from the analysis of the tail–tail and cation–water RDFs. As a general result, we found that the larger the anisotropy of the ionic liquid the lower the critical concentration and the larger the proportion of monomers forming part of the micelles. The molecular dynamics predictions are in line with the experimental evidence reported for these systems

Enhancing Separation Efficiency in European Syngas Industry by Using Zeolites

Syngas is traditionally used in industry for production of fuels in the kerosene, gasoline and diesel range via Fischer-Tropsch, for the manufacture of bulk chemicals like ammonia, methanol and dimethyl ether and for synthesis of a whole array of fine chemicals. The carbon monoxide/hydrogen ratio of the syngas is an important design variable to maximize production of these compounds. Therefore, the search of effective processes that enable said ratio adjustment as well as individual compound purification is an essential and ongoing effort for industry. In this work, we propose a development of a zeolite-based separation process to obtain carbon dioxide-neutral fuels and chemicals. The process designed is based on gas uptake and release, combining separation efficiency with low separation costs. Calculation of separation behavior has been done for mixtures generated by plasmolysis of CO2. Carbon dioxide dissociation into CO and O2 and as a result a mixture of carbon monoxide, oxygen and a residual carbon dioxide is obtained. Therefore, the purification of CO becomes necessary. Here we provide a purification process design based in multicomponent adsorption and separation in commercial available zeolites. The process identifies NaX and NaY as the most suitable zeolites for separation in a wide range of operating conditions

Enhancing Separation Efficiency in European Syngas Industry by Using Zeolites

Syngas is traditionally used in industry for production of fuels in the kerosene, gasoline and diesel range via Fischer-Tropsch, for the manufacture of bulk chemicals like ammonia, methanol and dimethyl ether and for synthesis of a whole array of fine chemicals. The carbon monoxide/hydrogen ratio of the syngas is an important design variable to maximize production of these compounds. Therefore, the search of effective processes that enable said ratio adjustment as well as individual compound purification is an essential and ongoing effort for industry. In this work, we propose a development of a zeolite-based separation process to obtain carbon dioxide-neutral fuels and chemicals. The process designed is based on gas uptake and release, combining separation efficiency with low separation costs. Calculation of separation behavior has been done for mixtures generated by plasmolysis of CO2. Carbon dioxide dissociation into CO and O2 and as a result a mixture of carbon monoxide, oxygen and a residual carbon dioxide is obtained. Therefore, the purification of CO becomes necessary. Here we provide a purification process design based in multicomponent adsorption and separation in commercial available zeolites. The process identifies NaX and NaY as the most suitable zeolites for separation in a wide range of operating conditions.</p