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Most industrial chemists spend their days separating the components of large quantities of chemical mixtures into pure or purer forms. The processes involved, such as distillation, account for 10-15% of [...]

The first atomically detailed simulations are presented that examine interfacial mass transfer resistance due to internal grain boundaries in zeolites that are relevant for membrane applications. The dual control volume grand canonical molecular dynamics method is used to stimulate the permeance of CH4 and CF4 through thin twinned silicalite crystals.

The first principles density functional theory calculations (DFT) are performed for a large number of potential destabilization schemes. The calculated results are in good agreement with the reaction enthalpies of destabilization reactions, suggesting that DFT calculations could provide quantitative insight into reactions of this type.

The density functional theory is used to study the adsorption and dissociation of carbon monoxide on the W(111) surface. The studies reveal that CO dissociation is a self-poisoning process, as the C atoms locks further dissociation of CO on the surface.

The structures of dense adlayers of glycine and alanine on the Cu(110) and Cu(100) surfaces are studied using plane wave density functional theory. It is observed that adlayers of enantiopure alanine are closely related to the adlayers for glycine, while racemic alanine adlayers on Cu(110) are structurally analogous to those observed for glycine on this surface.

Equilibrium molecular dynamics is used to probe the self-diffusion and transport diffusion of a number of small gas species in several metal-organic framework (MOFs) as a function of pore loading at room temperature. The prospects for exploiting molecular transport properties in MOFs in practical separation process and the future role of molecular dynamic simulations in screening families of MOFs are discussed.

Metal membranes play a vital role in hydrogen purification. Defect-free membranes can exhibit effectively infinite selectivity but must also provide high fluxes, resistance to poisoning, long operational lifetimes, and low cost. Alloying offers one route to improve on membranes based on pure metals such as palladium. We show how ab initio calculations and coarse-grained modeling can accurately predict hydrogen fluxes through binary alloy membranes as functions of alloy composition, temperature, and pressure. Our approach, which requires no experimental input apart from knowledge of bulk crystal structures, is demonstrated for palladium-copper alloys, which show nontrivial behavior due to the existence of face-centered cubic and body-centered cubic crystal structures and have the potential to resist sulfur poisoning. The accuracy of our approach is examined by a comparison with extensive experiments using thick foils at elevated temperatures. Our experiments a[so demonstrate the ability of these membranes to resist poisoning by hydrogen sulfide., The purification of hydrogen from gas mixtures is a crucial process in both existing and envisioned uses of hydrogen as a chemical feedstock and fuel (1, 2). Membranes made from [...]

Quasi-elastic neutron scattering is used to determine the concentration-dependent corrected and transport diffusivities for CF4 adsorbed in silicalite at 200 and 250 K, and equilibrium molecular dynamics simulations are used to compute the diffusivities under the same condition. The results indicate strong support for the use of atomistic simulations to quantitatively explore the diffusion of small molecules in nanoporous materials.

Equilibrium molecular dynamics can be used to directly compute anisotropic transport diffusivities for atomistic models of molecules diffusing in zeolites. Deviations from the so-called Darken approximation over a wide range of loadings and temperatures are documented.

A study was conducted to demonstrate the application of an efficient computational models to evaluate large numbers of metal-organic frameworks (MOFs) for kinetic separations of light gases based on finding materials with large differences between the diffusion coefficients of adsorbed gas species. The study identified a significant number of materials that are predicted to have extraordinary properties for separation of gases such as C[O.sub.2], C[H.sub.4], and [H.sub.2].

Molecular simulations are used for describing the diffusion of C[O.sub.2] and C[H.sub.4] inside the silica zeolite DDR pores. The studies have shown that DDR membranes are favorable for C[O.sub.2]/C[H.sub.4] separations and also similar properties are present for other 8MR zeolites.

Applications of molecular dynamics (MD) were described to diffusion in nanoporous materials with a particular focus on macroscopic diffusion. It was found that these methods made useful contributions to developing mixing theories for predicting multicomponent diffusion from single-component data and to screening new classes of material for practical applications.

A study was carried out to determine the diffusive transport of molecules through nanoporous membranes by both intracrystalline diffusion and mass transport resistances associated with entering and leaving the membrane material. This study introduces an approximate method that uses information only from equilibrium MD simulations, which avoids the significant computational expense associated with dual control volume grand canonical molecular dynamics (DCV-GCMD).

A study to understand the enantiospecific adsorption of R-3-MCHO on the Cu(643)R and Cu(643)S surfaces is presented. The study reports the first evidence for the enantioselective separation of racemic mixture (3-MCHO) into enantiometrically purified components on a naturally chiral metal surface.

The fundamental mechanisms of adsorption and diffusion for Ni-H and Ni-S species on the MoS2 basal plane without including the full range of surface species and catalytically active edge sites that exist under the conditions necessary for practical HDS catalyst are examined. Ni atoms present on the surface present centers of enhanced chemical activity where H, H2, S, S2, HS, and H2S species can be adsorbed with significant bonding energies.

The study deals with the introduction of the density functional theory studies, the second part includes the computational methods used, the third part explains the results of the experiment and the fourth part summarizes the conclusions. Several possible adsorption configurations of Ni atoms on the surface are identified.

A study was conducted, using atomistic simulations, to investigate the adsorption of CO2 and N2 in three zeolites with identical chemical composition but differing pore structures. The result indicates that the different electric fields present inside zeolites with different crystal structures but identical chemical composition play an important role in the observed adsorption capacities and selectiveness.

The single-component self, corrected, and transport diffusivities for atomistic models of seven small molecules, CH4, CH4, He, Ne, Ar, Xe, and SF6 adsorbed in silicalite are described. The result indicates the understanding self and transport diffusivities in mesoporous materials and for multi-component mixtures in microporous materials.

The atomistic computational modeling of chiral disubstituted cycloalkanes adsorbed in chiral single-walled carbon nanotubes (SWNTS) is described. Results suggest that chiral single-walled carbon nanotubes (SWNTS) would not be effective as general-purpose enantiospecific adsorbents.

The experiments were done on the chiral metal surfaces where a series of atomistic simulations were used to assess the enantiospecific adsorption properties of chiral hydrocarbons on chiral Pt surfaces. The results indicate that naturally chiral metal surfaces retain their chirality even after thermal step roughening disrupts their local structure.

Reactivity of Au nanoparticles in place-exchange with disulfides is reduced by aging. This can lead to a slow reorganization of the nanoparticle surface.

Self-diffusion and macroscopic diffusion of equimolar CH4/H2 mixtures in (10,10) single-walled carbon nanotubes (SWNTs) at 298K was examined using equilibrium molecular dynamics (EMD). This experiment can have possible applications of SWNTs in adsorption-based or membrane based gas separation.

THE ASTONISHING RESULTS OF P.M. AJAYAN et al. ('Nanotubes in a flash--ignition and reconstruction,' Brevia, 26 April, p. 705) demonstrating ignition of carbon nanotubes after exposure to a photographic flash [...]