The Experts below are selected from a list of 15219 Experts worldwide ranked by ideXlab platform
C N R Rao - One of the best experts on this subject based on the ideXlab platform.
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a study of micropores in single walled carbon nanotubes by the Adsorption of Gases and vapors
Chemical Physics Letters, 1999Co-Authors: M Eswaramoorthy, Rahul Sen, C N R RaoAbstract:Adsorption of N2, benzene and methanol have been studied on as-prepared single-walled carbon nanotubes (SWNT) as well as SWNTs treated with HCl and HNO3. These nanotubes are good microporous materials with total surface areas well above 400 m2/g and internal surface areas of 300 m2/g or higher. Benzene molecules are shown to be adsorbed within the pores of the SWNTs.
Karl J Johnson - One of the best experts on this subject based on the ideXlab platform.
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Adsorption of Gases in carbon nanotubes are defect interstitial sites important
Langmuir, 2008Co-Authors: Matthew R Labrosse, Wei Shi, Karl J JohnsonAbstract:Molecular simulations are used to shed light on an ongoing controversy over where Gases adsorb on single walled carbon nanotube bundles. We have performed simulations using models of carbon nanotube bundles composed of tubes of all the same diameter (homogeneous) and tubes of different diameters (heterogeneous). Simulation data are compared with experimental data in an effort to identify the best model for describing experimental data. Adsorption isotherms, isosteric heats of Adsorption, and specific surface areas have been computed for Ar, CH4, and Xe on closed, open, and partially opened homogeneous and heterogeneous nanotube bundles. Experimental data from nanotubes prepared from two different methods, electric arc and HiPco, were examined. Experimental Adsorption isotherms and isosteric heats for nanotubes prepared by the electric arc method are in best agreement with simulations for heterogeneous bundles of closed nanotubes. Models including Adsorption in defect interstitial channels are required to ...
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Adsorption of Gases in metal organic materials comparison of simulations and experiments
Journal of Physical Chemistry B, 2005Co-Authors: Giovanni Garberoglio, Anastasios I Skoulidas, Karl J JohnsonAbstract:Molecular simulations using standard force fields have been carried out to model the Adsorption of various light Gases on a number of different metal organic framework-type materials. The results have been compared with the available experimental data to test the validity of the model potentials. We observe good agreement between simulations and experiments for a number of different cases and very poor agreement in other cases. Possible reasons for the discrepancy in simulated and measured isotherms are discussed. We predict hydrogen Adsorption isotherms at 77 and 298 K in a number of different metal organic framework materials. The importance of quantum diffraction effects and framework charges on the Adsorption of hydrogen at 77 K is discussed. Our calculations indicate that at room temperature none of the materials that we have tested is able to meet the requirements for on-board hydrogen storage for fuel cell vehicles. We have calculated the volume available in a given sorbent at a specified Adsorption energy (density of states). We discuss how this density of states can be used to assess the effectiveness of a sorbent material for hydrogen storage.
Hans-joachim Freund - One of the best experts on this subject based on the ideXlab platform.
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Adsorption of Gases on Complex Solid Surfaces
Angewandte Chemie International Edition in English, 1997Co-Authors: Hans-joachim FreundAbstract:During the last thirty years the research field of surface science with its various disciplines has progressively played a more and more important role in the field of catalysis. The main focus of attention for a long time was research on metal surfaces, on which, in time, the whole spectrum of developed surface analytical methods was applied. This led to a better understanding of the mechanisms of catalytic reaction, such as the synthesis of ammonia and the oxidation of CO, especially through the work of Gerhard Ertl.[1, 2] In contrast to clean metal surfaces, surfaces of real catalysts are complex entities, the structures of which can have a strong influence on the processes occurring on the surface. Thus, it seems logical to employ the typical structural characteristics and the morphology of the catalytic surface as guidelines in the investigation of complex model systems. In this review the preparation, and structural and electronic characterization of such model systems will be dicussed. Clean surfaces of catalytically active oxides, as well as model systems for dispered transition metal/support catalysts will be characterized in terms of their morphology and electronic structure as well as their Adsorption and reaction capabilities.
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Adsorption of Gases on Solid Surfaces
Berichte der Bunsengesellschaft für physikalische Chemie, 1995Co-Authors: Hans-joachim FreundAbstract:Metal surfaces have for a long time been and still are in the focus of experimental and theoretical activities in surface science. One has started to understand in some detail the interaction of Gases with respect to structural and dynamical aspects. Non-metallic substrates on the other hand have only recently received more attention and corresponding studies have been started. In view of the importance of compound surfaces in many fields, including catalysis, this development is not unexpected. We review our efforts in the field of surface science studies of oxide surfaces and emphasize in addition to clean oxide surfaces also metal modified surfaces as a model towards the study of complex systems which are typical for catalysts. In addition to studies of the geometric and electronic structure of compound surfaces we also cover investigations of adsorbate dynamics reporting on newly designed experiments on the basis of magnetic resonance as well as on laser-induced desorption studies. In the latter investigations we have probed spatially resolved the time-of-flight distributions of molecules in individual quantum states as they leave the oxide surface.
Alan L. Myers - One of the best experts on this subject based on the ideXlab platform.
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Physical Adsorption of Gases: the case for absolute Adsorption as the basis for thermodynamic analysis
Adsorption, 2014Co-Authors: Alan L. Myers, Peter A. MonsonAbstract:We discuss the thermodynamics of physical Adsorption of Gases in porous solids. The measurement of the amount of gas adsorbed in a solid requires specialized volumetric and gravimetric techniques based upon the concept of the surface excess. Excess Adsorption isotherms provide thermodynamic information about the gas-solid system but are difficult to interpret at high pressure because of peculiarities such as intersecting isotherms. Quantities such as pore density and heats of Adsorption are undefined for excess isotherms at high pressure. These difficulties vanish when excess isotherms are converted to absolute Adsorption. Using the proper definitions, the special features of Adsorption can be incorporated into a rigorous framework of solution thermodynamics. Practical applications including mixed-gas equilibria, equations for Adsorption isotherms, and methods for calculating thermodynamic properties are covered. The primary limitations of the absolute Adsorption formalism arise from the need to estimate pore volumes and in the application to systems with larger mesopores or macropores at high bulk pressures and temperatures where the thermodynamic properties may be dominated by contributions from the bulk fluid. Under these circumstances a rigorous treatment of the thermodynamics requires consideration of the Adsorption cell and its contents (bulk gas, porous solid and confined fluid).
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Equation of State for Adsorption of Gases and Their Mixtures in Porous Materials
Adsorption, 2003Co-Authors: Alan L. MyersAbstract:Desorption functions ( G, H, S ) are useful for adsorbent characterization, phase equilibria, and enthalpy and entropy balances. Adsorption isotherms, enthalpy, and entropy are temperature and pressure derivatives of the free energy, so that G ( T, P ) is an Adsorption equation-of-state which contains complete thermodynamic information about the system. The free energy of desorption is the minimum isothermal work necessary to regenerate the adsorbent. The free energy of desorption also determines the selectivity of an adsorbent for different Gases. The ideal enthalpy of desorption for a mixture ( H = ∑_ i n _ i h°_ i ) is a simple function of the enthalpies of desorption for the individual components. Sample calculations of the free energy, enthalpy, and entropy desorption functions are provided for pure components and mixtures.
A. M. Tolmachev - One of the best experts on this subject based on the ideXlab platform.
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Analysis of the Adsorption of Gases and Vapors on Carbon Surfaces Using the Molecular Dynamics Method
Protection of Metals and Physical Chemistry of Surfaces, 2019Co-Authors: A. M. Tolmachev, T. A. Kuznetsova, P. E. Fomenkov, A. C. PavlyuchenkovAbstract:A molecular dynamic experiment is carried out for analyzing the isotherms of Adsorption on a graphene surface at temperatures below and above the critical values for adsorptives. It is shown that the monomolecular isotherms of gas Adsorption on the flat carbon surfaces can be described using the set of equations of the lattice model and the equations of the theory of the volume filling of micropores (TVFM). The obtained results are compared with the experimental data on Adsorption in micropores of active carbons. When describing the isotherms of polymolecular Adsorption with the use of the BET and the Aranovich equations, the filling of each layer is analyzed.
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Adsorption of Gases vapors and solutions ii description and a priori calculations of Adsorption equilibria
Protection of Metals and Physical Chemistry of Surfaces, 2010Co-Authors: A. M. TolmachevAbstract:Systems of equations that enable one to quantitatively describe the Adsorption isotherms of Gases, vapors, and liquid solution components in macro- and microporous adsorbents and to theoretically (including a priori) find highly selective Adsorption systems for practically important technological processes are determined and analyzed.
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Adsorption of Gases, vapors, and solutions: I. Thermodynamics of Adsorption
Protection of Metals and Physical Chemistry of Surfaces, 2010Co-Authors: A. M. TolmachevAbstract:The review considers methods of describing and preliminarily calculating the equilibrium characteristics of the Adsorption of Gases, vapors, and vapor-liquid mixtures of substances on adsorbents of different structures based on semiempirical, thermodynamic, and molecular models of Adsorption systems. Based on the performed analysis, the systems of equations are obtained that allow one to fully describe the corresponding equilibriums and perform a theoretical study of highly selective Adsorption systems for practically important engineering processes.
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On the possibility of extending the theory of the volume filling of micropores to the Adsorption of Gases
Russian Journal of Physical Chemistry A, 2005Co-Authors: A. M. Tolmachev, Ivan A. Godovikov, T. A. KuznetsovaAbstract:The numerical solution of Dubinin-Radushkevich or Dubinin-Astakhov equations for the Adsorption of vapors gives three parameter values that virtually coincide with those found by the traditional method, by linearizing theequations and using the known p s values. These are E 0 (the characteristic energy of Adsorption), p s (the adsorbate saturated vapor pressure), and a 0 (the Adsorption at this pressure). This and an analysis of the literature data, according to which adsorbates experience no phase transition in the passage through the critical temperature, were used to show that the equations and the whole apparatus of the theory of the volume filling of micropores were applicable to the Adsorption of Gases and could be used in numerically solving these equations to determine equation parameters. The obtained p' s parameter values are interpreted as pressures at which the a 0 Adsorption values are reached.
