Ralph T. Yang

Adsorbents : fundamentals and applications

Preface. 1. Introductory Remarks. 2. Fundamental Factors for Designing Adsorbent. 3. Sorbent Selection: Equilibrium Isotherms, Diffusion, Cyclic Processes, and Sorbent Selection Criteria. 4. Pore Size Distribution. 5. Activated Carbon. 6. Silica Gel, MCM, and Activated Alumina. 7. Zeolites and Molecular Sieves. 8. &pi -Complexation Sorbents and Applications. 9. Carbon Nanotubes, Pillared Clays, and Polymeric Resins. 10. Sorbents for Applications. Author Index. Subject Index.

Rational approximations of the integral of the Arrhenius function

AbstractRational approximations have been derived for the integral of the Arrhenius function

New sorbents for hydrogen storage by hydrogen spillover – a review

\int\limits_0^T {\exp ( - E/RT)}

Theoretical basis for the Dubinin-Radushkevitch (D-R) adsorption isotherm equation

dT which is important in the kinetic analysis of thermogravimetric data. The first degree rational approximation is found to be equivalent to the Gorbachev approximation, i.e., RT2exp (−E/RT)/(E+2RT). The second degree rational approximation is more accurate than the Zsakó empirical approximation when E/RT < 1 and E/RT > 5. The third and higher degree rational approximations are found to be more accurate than any other previous approximation.

Kinetic separation of methane—carbon dioxide mixture by adsorption on molecular sieve carbon

Abstract Carbon filaments formed on Ni, Co, and α-Fe particles by reaction with methane were studied. The filaments contained faceted single-crystal metal particles located at the growing tips. The crystallographic orientations of the gas/metal and graphite/metal interfaces were identified by TEM/selected area diffraction. Furthermore, extended Huickel molecular orbital calculations indicated that the (111) and (311) faces of Ni provide stronger epitaxial fits with graphite than the (100) and (110) faces and that the order is reversed for their activities for CO decomposition. The results are in agreement with the limited amount of literature data on phase segregation and surface reconstruction for carbon/metal solid solutions. On the basis of these and literature results, a better understanding of the carbon dissolution/diffusion/precipitation mechanism for filament growth is obtained. Also, a temperature-driven carbon diffusion mechanism without resorting to the exothermality of the surface reaction is proposed.

Desulfurization of Transportation Fuels by Adsorption

The utilization of hydrogen as an energy source or carrier for fuel-cell powered vehicles is limited by the lack of a safe and effective hydrogen storage system. Recent advances in the application of hydrogen spillover for hydrogen storage have provided a promising route for hydrogen storage. An overview of the progress made on hydrogen storage by spillover at ambient temperature on various adsorbents, including carbons, metal organic frameworks (MOFs) and other nanostructured materials, is given in this review. New techniques for facilitating hydrogen spillover that were developed in our laboratory are discussed, along with future directions.

Ab initio molecular orbital study of adsorption of atomic hydrogen on graphite: Insight into hydrogen storage in carbon nanotubes

Alkali metals are among the strongest poisons to the V2O5/TiO2 catalyst for selective catalytic reduction of NO by NH3. The strength of the poison is directly related to its basicity. SO2, in contrast, promotes the activity. The chemisorbed NH3 on the catalyst is predominantly NH4+, bonded to the Bronsted acid site of VOH. A direct correlation exists between the amount of chemisorbed ammonia and the activity of the poison-doped catalyst. Furthermore, dehydroxylation of the catalyst by heat treatment eliminates its activity, which is restored rapidly by exposure to water vapor. Extended Huckel molecular orbital (EHMO) calculation was performed on a model V2O5/TiO2 surface. The extraction energy for proton from the VOH group and the net charge of H in the VOH group are used as indices for Bronsted acidity. The EHMO results show decreases in the Bronsted acidity by the addition of alkali metals, and the order of the decrease follows the order of the basicity of the alkali metal. SO2, in contrast, increases the Bronsted acidity. These results indicate that the Bronsted acid sites are the active sites for the reaction. Alkali metals poison the catalyst by decreasing its Bronsted acidity. SO2 promotes the activity by increasing the Bronsted acidity.

Kinetics and mechanism of oxidation of basal plane on graphite

The Dubinin-Radushkevitch (D-R) equation, which was originally proposed as an empirical adaptation The Polanyi adsorption potential theory, has been the fundamental equation to quantitatively describe the adsorption gases and vapors by microporous sorbents. The equation, based on the postulate that the mechanism for adsorption in micropores is that of pore-filling rather than layer-by-layer surface coverage, generally applies well to adsorption systems involving only van der Waals forces and is especially useful to describe adsorption on activated ???. The ability of the D-R equation to describe gas adsorption on porous materials has inspired many to undertake studies, both experimental and theoretical, to explain the source of the success of the D-R equation in ??? of molecular properties at the gas-solid interface. In many cases, these studies have led to extensions or modifications of the original D-R equation. Many of these attempts and the resulting extensions are reviewed and discussed here. Recently, an isotherm equation was derived for adsorption of gases and vapors on microporous ??? from statistical mechanical principles. It was shown that the D-R equation is an approximated form of this potential theory isotherm. This development is also reviewed and discussed.