GENERALIZED GRADIENT APPROXIMATION;
TEMPERATURE INFRARED-SPECTROSCOPY;
CARBON-MONOXIDE ADSORPTION;
INITIO MOLECULAR-DYNAMICS;
METAL-EXCHANGED ZEOLITES;
AUGMENTED-WAVE METHOD;
THERMODYNAMICS;
SEPARATION;
GAS;
TRANSITION;
D O I:
10.1016/j.cplett.2009.06.058
中图分类号:
O64 [物理化学(理论化学)、化学物理学];
学科分类号:
070304 ;
081704 ;
摘要:
Adsorption of H-2 on the zeolite Ca-A was investigated by a combination of variable temperature IR spectroscopy and calculations at the periodic DFT level. Calculations showed that adsorption complexes can be formed on two types of adsorption sites: Ca2+ in the center of six-member rings and Ca2+ in eight-member rings. Only the former adsorption complexes were experimentally observed in IR spectra; they are characterized by H-H stretching frequency of 4083 cm (1) and Delta H-0 = -12 kJ/mol in agreement with calculated results. The most likely explanation for not observing the adsorption complex on Ca2+ in 8-member rings is that the geometry of the complex does not render the H-H stretching mode IR active. (C) 2009 Published by Elsevier B. V.