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91.
Dispersion-corrected density functional theory method was performed to report on a high-performance adsorbent for removal of CO2 from the precombustion and natural gases. At first, the effect of Al atom impurity on the structural and electronic properties of B80 fullerene is studied. Then, the adsorption geometries and energies of gases (H2, CH4, or CO2) on the B80 and AlB79 (amphoteric adsorbents) are explored. The Al atom enhances reactivity of the cage toward the gases and the adsorption processes are more exothermic with low and high energy barriers for chemisorption of H2 and CO2, respectively. Stable chemisorption of CO2 on the AlB79 is validated by the high adsorption energy and large charge transfer, while the CH4 is just physically adsorbed on the AlB79. Further, the physisorbed gases can enhance field emission current of the AlB79 and in the continuous capturing of the gases, the magnetic moment of the cage is quenched. Furthermore, dependency of the electronic structure of the adsorbent on the gas adsorption is intensively studied. We suggest that the AlB79 could be a promising material for capture, storage, and separation of the gases and as a novel material for sustainable energy and sweetening process in the petroleum industry. 相似文献
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93.
Affine semigroups are convex sets on which there exists an associative binary operation which is affine separately in either variable. They were introduced by Cohen and Collins in 1959. We look at examples of affine semigroups which are of interest to matrix and operator theory and we prove some new results on the extreme points and the absorbing elements of certain types of affine semigroups. Most notably we improve a result of Wendel that every invertible element in a compact affine semigroup is extreme by extending this result to linearly bounded affine semigroups. 相似文献
94.
Abstract An N.M.R. method combining the techniques of separated local field spectroscopy (SLF) and variable angle spinning (VAS) is valuable in the investigtion of nematic liquid crystals. Rapid sample spinning causes the nematic director to align along the spinning axis, resulting in narrow peaks in the C-13 N.M.R. spectrum. SLF is a two-dimensional N.M.R. method which produces a first order splitting pattern for each carbon signal from which C–H dipolar coupling constants can be determined. The order parameters for all segments of the liquid crystal molecule can then be calculated. Results for three 4′-cyanophenylcyclohexanes are considered here. These compounds are trans-substituted at the 4 position of cyclohexane ring with n-pentane (PCH5), 1-pentene (3d 1CP) and 3-pentene (1d 3CP), respectively. 相似文献
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96.
A convenient method has been developed for directly converting esters to amides using reagents derived from the reaction of trimethylaluminum with ammonium chloride, methylamine hydrochloride or dimethylamine hydrochloride. 相似文献
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99.
We investigate low-energy deformations of a thin elastic sheet subject to a displacement boundary condition consistent with a conical deformation. Under the assumption that the displacement near the sheet’s center is of order h|logh|, where h?1 is the thickness of the sheet, we establish matching upper and lower bounds of order h 2|logh| for the minimum elastic energy per unit thickness, with a prefactor determined by the geometry of the associated conical deformation. These results are established first for a 2D model problem and then extended to 3D elasticity. 相似文献
100.
Zbyněk Brůža Dr. Jiří Kratochvíl Prof. Jeremy N. Harvey Dr. Lubomír Rulíšek Dr. Lucie Nováková Jana Maříková Dr. Jiří Kuneš Prof. Pavel Kočovský Prof. Milan Pour 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(34):8053-8060
Pyran-2-ones 3 undergo a novel Pd0-catalyzed 1,3-rearrangement to afford isomers 6 . The reaction proceeds via an η2-Pd complex, the pyramidalization of which (confirmed by quantum chemistry calculations) offers a favorable antiperiplanar alignment of the Pd−C and allylic C−O bonds ( C ), thus allowing the formation of an η3-Pd intermediate. Subsequent rotation and rate-limiting recombination with the carboxylate arm then gives isomeric pyran-2-ones 6 . The calculated free energies reproduce the observed kinetics semi-quantitatively. 相似文献