The Experts below are selected from a list of 249 Experts worldwide ranked by ideXlab platform

Helmer Fjellvag - One of the best experts on this subject based on the ideXlab platform.

Jun Liu - One of the best experts on this subject based on the ideXlab platform.

  • Supercritical processing of functionalized size selective Microporous Materials
    Microporous and Mesoporous Materials, 2000
    Co-Authors: Yongsoon Shin, Thomas S. Zemanian, Glen E. Fryxell, Li-qiong Wang, Jun Liu
    Abstract:

    Abstract A supercritical fluid silanation process is applied to effectively functionalize commercial Microporous Materials without blocking the pore channels. In this approach, supercritical carbon dioxide (SCCO 2 ) is used to deposit mercaptopropyl silane into the microporosity of zeolite beta. The thiol group was subsequently oxidized into sulfonic acid. The size selective catalytic properties of the SCCO 2 modified zeolite compare well with similar Materials prepared by an in situ silanation process reported by Jones et al. The active functional groups were delivered to the internal pore surface of the Microporous Material and remain accessible to molecules that can enter the pore channels. The supercritical process provides an alternative approach to functionalize Microporous Materials because of the enhanced diffusivity of the functional molecules in the micropore channels and accelerated reaction kinetics. Furthermore, the supercritical process simplifies the Materials preparation and may open up new opportunities for commercial zeolites.

Larry Kevan - One of the best experts on this subject based on the ideXlab platform.

  • Photoinduced Charge Separation of Pyrene in Chromium Containing Silicoaluminophosphate (SAPO-5) Microporous Materials at Room Temperature
    The Journal of Physical Chemistry B, 2003
    Co-Authors: Koodali T. Ranjit And, Larry Kevan
    Abstract:

    The photoinduced charge separation of pyrene in chromium containing Microporous SAPO-5 Materials with ultraviolet irradiation at room temperature was examined. Photoionization of pyrene in Cr containing SAPO-5 results in the formation of pyrene cation radicals that are characterized by electron spin resonance (ESR) and diffuse reflectance spectroscopy (DRS). ESR studies indicate that Cr(V) acts as an electron acceptor. The photoyield and stability of the photoproduced pyrene cation radical were found to depend on the pore size of the Microporous Material, the concentration, and the oxidation state of chromium ions. The photoyield and stability of the photoproduced pyrene cation are found to be higher than in mesoporous Materials investigated in our laboratory earlier. The study thus demonstrates the importance of Cr containing Microporous SAPO-5 Materials as potential candidates for photochemical conversion and storage devices.

Romain Vermorel - One of the best experts on this subject based on the ideXlab platform.

  • Molecular Simulations of Supercritical Fluid Permeation through Disordered Microporous Carbons
    Langmuir, 2013
    Co-Authors: Alexandru Botan, Romain Vermorel, Franz-josef Ulm, Roland J.-m. Pellenq
    Abstract:

    Fluid transport through Microporous carbon-based Materials is inherent in numerous applications, ranging from gas separation by carbon molecular sieves to natural gas production from coal seams and gas shales. The present study investigates the steady-state permeation of supercritical methane in response to a constant cross-membrane pressure drop. We performed dual control volume grand canonical molecular dynamics (DCV-GCMD) simulations to mimic the conditions of actual permeation experiments. To overcome arbitrary assumptions regarding the investigated porous structures, the membranes were modeled after the CS1000a and CS1000 molecular models, which are representative of real Microporous carbon Materials. When adsorption-induced molecular trapping (AIMT) mechanisms are negligible, we show that the permeability of the Microporous Material, although not significantly sensitive to the pressure gradient, monotonically decreases with temperature and reservoir pressures, consistent with diffusion theory. However, when AIMT occurs, the permeability increases with temperature in agreement with experimental data found in the literature.

  • Revisiting poromechanics in the context of Microporous Materials
    Comptes Rendus Mécanique, 2011
    Co-Authors: Gilles Pijaudier-cabot, Romain Vermorel, Christelle Miqueu, Bruno Mendiboure
    Abstract:

    Poromechanics offers a consistent theoretical framework for describing the mechanical response of porous solids, fully or partially saturated with a fluid phase. When dealing with fully saturated Microporous Materials, which exhibit pores of the nanometre size, aside from the fluid pressure acting on the pore walls additional effects due to adsorption and confinement of the fluid molecules in the smallest pores must be accounted for. From the mechanical point of view, these phenomena result into volumetric deformations of the porous solid: the so-called "swelling" phenomenon. The present work investigates how the poromechanical theory should be refined in order to describe adsorption and confinement induced swelling in Microporous solids. Firstly, we report molecular simulation results that show that the pressure and density of the fluid in the smallest pores are responsible for the volumetric deformation of the Material. Secondly, poromechanics is revisited in the context of a Microporous Material with a continuous pore size distribution. Accounting for the thermodynamic equilibrium of the fluid phase in the overall pore space, the new formulation introduces an apparent porosity and an interaction free energy. We use a prototype constitutive relation relating these two quantities to the Gibbs adsorption isotherm, and then calculate the induced deformation of the solid matrix. Agreement with experimental data found in the literature is observed. As an illustrating example, we show the predicted strains in the case of adsorption of methane on activated carbon.

  • Revisiting poromechanics in the context of Microporous Materials
    Comptes Rendus Mécanique, 2011
    Co-Authors: Gilles Pijaudier-cabot, Romain Vermorel, Christelle Miqueu, Bruno Mendiboure
    Abstract:

    International audiencePoromechanics offers a consistent theoretical framework for describing the mechanical response of porous solids, fully or partially saturated with a fluid phase. When dealing with fully saturated Microporous Materials, which exhibit pores of the nanometre size, aside from the fluid pressure acting on the pore walls additional effects due to adsorption and confinement of the fluid molecules in the smallest pores must be accounted for. From the mechanical point of view, these phenomena result into volumetric deformations of the porous solid: the so-called "swelling" phenomenon. The present work investigates how the poromechanical theory should be refined in order to describe adsorption and confinement induced swelling in Microporous solids. Firstly, we report molecular simulation results that show that the pressure and density of the fluid in the smallest pores are responsible for the volumetric deformation of the Material. Secondly, poromechanics is revisited in the context of a Microporous Material with a continuous pore size distribution. Accounting for the thermodynamic equilibrium of the fluid phase in the overall pore space, the new formulation introduces an apparent porosity and an interaction free energy. We use a prototype constitutive relation relating these two quantities to the Gibbs adsorption isotherm, and then calculate the induced deformation of the solid matrix. Agreement with experimental data found in the literature is observed. As an illustrating example, we show the predicted strains in the case of adsorption of methane on activated carbon

Georgios N Kalantzopoulos - One of the best experts on this subject based on the ideXlab platform.