Vapor-liquid interfacial properties of the system cyclohexane + CO2: Experiments, molecular simulation and density gradient theory

Properties of the vapor-liquid interface of the binary mixture cyclohexane + CO2 as well as for the two pure substances are reported. The data were obtained from pendant drop experiments (Exp), molecular dynamics (MD) simulation, and density gradient theory (DGT) in combination with the PCP-SAFT equation of state. The following interfacial properties were studied: surface tension (Exp, MD, DGT), relative adsorption (Exp, MD, DGT), enrichment (MD, DGT), and interfacial thickness (MD, DGT). The measurements were carried out at temperatures between 303.15 K and 373.15 K and pressures up to 6 MPa. Furthermore, bulk VLE properties were computed by MD and PCP-SAFT and compared to experimental data from the literature. Data from experiment, MD, and DGT were found to be in good agreement throughout.

Interfacial Properties of Binary Lennard-Jones Mixtures by Molecular Simulation and Density Gradient Theory

A systematic study of interfacial properties of binary mixtures of simpleuids wascarried out by molecular dynamics (MD) simulation and density gradient theory(DGT). Theuids are described by the Lennard-Jones truncated and shifted potentialwith truncation radius of 2.5 diameters (LJTSuid). The following interfacialproperties were studied: surface tension, relative adsorption, enrichment, and interfacialthickness. A recently developed equation of state for the LJTSuid (PeTS EOS)was used as basis for the DGT. Six binary mixtures (components 1 + 2) were studiedat a constant temperature, which was chosen such that the high-boiling component1 is subcritical while the low-boiling component 2 is either subcritical or supercritical.Furthermore, a parameter ? in the combination rule for the unlike dispersiveinteraction was varied such that the resulting mixtures showed three types of behavior:high-boiling azeotrope, ideal, and low-boiling azeotrope. The parametersof the LJTS potential, including ?, were also used in the PeTS EOS without anyadjustment. Despite this simple approach, excellent agreement between the resultsof the PeTS EOS and the MD results for the phase equilibrium and the interfacialproperties is observed. Enrichment at the interface is only found for the low-boilingcomponent 2. The enrichment increases with decreasing concentration of component2 and is favored by high boiling point di?erences of the pure components 1 and 2 andpositive deviations from Raoult's law for the mixture 1 + 2.

Applicability Analysis of Determination Models for Nanopores in Coal Using Low-Pressure CO2 and N2 Adsorption Methods

The development characteristics of nanopores (with pore sizes <200 nm) in coal are a key factor affecting the accumulation and migration of coalbed methane (CBM). Thus, an appropriate determination method and calculation model are essential for accurate nanopore representation. Based on the experiments of low-pressure CO2 adsorption (LP-CO2GA) at 273 K and low-pressure N2 adsorption (LP-N2GA) at 77 K on four coals with different ranks, the abilities of different models (e.g., Langmuir, Dubinin-Radushkevich (D-R), Dubinin-Astakhov (D-A), Brunauer-Emmett-Teller (BET) and nonlocal density functional theory (NLDFT)) to accurately predict the pore parameters were analyzed. The results showed that (1) for LP-N2GA, the Langmuir model is only suitable for gas adsorptions at low relative pressure conditions (P/P0 < 0.01), and its error value increased with the relative adsorption pressure. The fitting results of the D-R model showed good agreement with the D-A model under low relative pressure of LP-CO2GA (P/P0 < 0.01), and the D-A model had more accurate fitting results. The BET model is more accurate than the other models (φ = −1.2733%) only in the interval of LP-N2GA with 0.05 < P/P0 < 0.35. The data also showed that the NLDFT model can maintain a higher fitting accuracy for LPCO2/N2GA processes at relative adsorption pressures from 0.001–0.9996. (2) Using LP-CO2GA with the Langmuir, D-R, D-A, and NLDFT models, the micropore specific surface area (SSA; 66.9570–248.6736 m2/g) and pore volume (0.0201– 0.0997 cm3/g) were obtained, while the values of meso-/macropore SSA (0.0007–2.3398 m2/g) and pore volume (0.0036–0.04 cm3/g) were calculated by LP-N2GA with the BET and NLDFT models. The results showed that the fitting accuracy in descending order was the D-R, D-A, Langmuir and NLDFT models. (3) In combination with the applicable model range, LP-CO2GA with the NLDFT model was recommended for micropore analysis of the coal pore sizes from 0.36–1.1 nm, while LP-N2GA combined with the NLDFT model was recommended for nanopore analysis of pore sizes from 1.1–200 nm. (4) The characteristics of pore development in the Beiloutian coal were analyzed using LP-CO2/N2GA combined with the NLDFT model. It was found that a pore volume and SSA less than 1.0 nm accounted for 88.82% of the total pore volume and 98.05% of the total SSA, indicating that micropores in coal are the main space for CBM storage and are key physical factors for the occurrence and migration of coalbed methane. The conclusions of this article will provide a basis for the accurate calculation of nanopores in coal.

Core-Shell Molecularly Imprinted Polymer Nanocomposites for Biomedical and Environmental Applications

: Core-shell polymers represent a class of composite particles comprising of minimum two dissimilar constituents, one at the center known as a core which is occupied by the other called shell. Core-shell molecularly imprinting polymers (CSMIPs) are composites prepared via printing a template molecule (analyte) in the coreshell assembly followed by their elimination to provide the everlasting cavities specific to the template molecules. Various other types of CSMIPs with a partial shell, hollow-core and empty-shell are also prepared. Numerous methods have been reported for synthesizing the CSMIPs. CSMIPs composites could develop the ability to identify template molecules, increase the relative adsorption selectivity and offer higher adsorption capacity. Keen features are measured that permits these polymers to be utilized in numerous applications. It has been developed as a modern technique with the probability for an extensive range of uses in selective adsorption, biomedical fields, food processing, environmental applications, in utilizing the plant's extracts for further applications, and sensors. This review covers the approaches of developing the CSMIPs synthetic schemes, and their application with special emphasis on uses in the biomedical field, food care subjects, plant extracts analysis and in environmental studies.

The Steric Effect in Green Benzylation of Arenes with Benzyl Alcohol Catalyzed by Hierarchical H-beta Zeolite

For decades the steric effect was still ambiguously understood in catalytic benzylation reactions of arenes with benzyl alcohol, which limited the green synthesis of phenylmethane derivates in industrial scale. This research applies a series of silica–alumina beta zeolites to systematically evaluate factors like catalyst porosity, reactants molecule size, and reaction temperature on catalytic benzylation. First, a suitable hierarchical beta zeolite catalyst was screened out by X-ray powder diffraction, N2 adsorption−desorption, and probe benzylation with p-xylene. In the following substrates expanding study, for a typical benzylation of benzene, it showed extraordinary performance among literature reported ones that the conversion was 98% while selectivity was 90% at 353 K only after 10 min. The steric effect of aromatics with different molecular sizes on benzylation was observed. The reaction activities of four different aromatics followed the order: benzene > toluene > p-xylene > mesitylene. Combined with macroscopic kinetic analysis, this comprehensive study points out for the first time that the nature of this steric effect was dominated by the relative adsorption efficiency of different guest aromatic molecules on the host zeolite surface.

Synthesis and Applications of Molecularly Imprinted Polymers Modified TiO2 Nanomaterials: A Review

Titanium dioxide (TiO2) nanomaterials have caused a widespread concern in the past several decades for their bulk characteristics and potential applications in many different areas. Lately, the combination between molecularly imprinted polymers (MIPs) and TiO2 nanomaterials have been proven to improve the relative adsorption capacity, selectivity and accelerate the rate of mass transfer of analyte which is not possible using TiO2 alone. Considering the unique performance of the MIPs modified TiO2 nanomaterials, this review intends to give an overview of the recent progresses in the development of MIPs modified TiO2 nanomaterials, the potential applications of their tailor-made characteristics. The limitations and challenges in this practically promising nanomaterials have also been raised and summarized. By means of the points raised in this article, we would like to provide some assistance for further development of preparation methodologies and the expansion of some potential applications in the field of MIPs modified TiO2 nanomaterials.

A Density Functional Theory Study of NH3 and NO Adsorption on the β-MnO2 (110) Surface

The adsorption of NH3 and NO on the β-MnO2 (1 1 0) surface has been investigated by density functional theory using periodic models. The energetically favourable sites of adsorption of the gases on the β-MnO2 surface are 4-fold coordinate Mn (Mn4-top) and 5-fold coordinate Mn (Mn5-top). The relative adsorption energies ( Eads) of these gases on the Mn4-top site and Mn5-top site are in the orders NH3 ( Eads = −1.02 eV) > NO ( Eads = −0.96 eV) and NH3 ( Eads = −0.63 eV) > NO ( Eads = −0.49 eV). The N-H and N–O bond lengths, Mulliken charges and the densities of states of the NH3 and NO molecules are discussed after adsorption. The calculated results indicate that the coordination number of surface Mn ions has a significant influence on the adsorption capacity. Furthermore, the analysis of the results of the density of states determinations shows that when NH3 and NO are adsorbed with the NH3-Mn and NO-Mn configurations, the bonding mechanism is mainly from the interaction between the NH3 or NO molecule and the Mn d orbital, which is the major reason for the strong chemical adsorption of NH3 and NO.

Textile binding and release of body odor compounds measured by proton transfer reaction – mass spectrometry

The creation of axillary body odor and its interaction with worn textiles is of continuing interest to textile manufacturers and finishers, product developers and marketers, and end users. This paper explains a novel proton transfer reaction – mass spectrometry model system to investigate the adsorption and release behavior of three fiber types commonly worn next to the skin (cotton, polyester, wool) for compounds found in body odor (dimethyl disulfide, 2-propanethiol, benzaldehyde, nonanal, butanoic acid, and 3-methyl-2-hexenoic acid). Three different patterns were observed: low relative adsorption and low overall release of the volatiles for cotton, high relative adsorption and continuous release of the volatiles for polyester, and high relative adsorption but low overall release for wool. This investigation, coupled with earlier studies by our group, goes some way to explain why the different fiber types are perceived as enhancing or suppressing body odor.

Research on Assessment Parameters of Adsorption Properties in Cation Exchange Membranes for all Vanadium Redox Flow Battery

The relative adsorption coefficient, a novel parameter was introduced to describe the dominant adsorption ability of ions in cation membrane for all vanadium redox flow battery instead of traditional selectivity coefficient. The parameter as a function of membrane property and vanadium ions in membrane was derived from the relative potential differences in membrane between an isothermal adsorption and an ideal equivalent adsorption. The adsorption isotherms of three kinds of commercial membranes were measured for VO2+/H+ electrolyte system. The results show the reasonable rules that the relative adsorption coefficients increase as the VO2+ contents are increased whereas decrease as the H+ contents are increased in electrolyte.