Kinetic Isotope Effect for H2 and D2 Quantum Molecular Sieving in Adsorption/ Desorption on Nanoporous Carbons
writer：Xuebo Zhao, S. Villar-Rodil, A. J. Fletcher, K. M. Thomas*
keywords：Quantum Molecular Sieving
source：期刊
specific source：J. Phys. Chem. B, 2006, 110, 9947-9955.
Issue time：2006年
Adsorption and desorption of H2 and D2 from porous carbon materials, such as activated carbon at 77 K, are usually fully reversible with very rapid adsorption/desorption kinetics. The adsorption and desorption of H2 and D2 at 77 K on a carbon molecular sieve (Takeda 3A), where the kinetic selectivity was incorporated by carbon deposition, and a carbon, where the pore structure was modified by thermal annealing to give similar pore structure characteristics to the carbon molecular sieve substrate, were studied. The D2 adsorption and desorption kinetics were significantly faster (up to ×1.9) than the corresponding H2 kinetics for specific pressure increments/decrements. This represents the first experimental observation of kinetic isotope quantum molecular sieving in porous materials due to the larger zero-point energy for the lighter H2, resulting in slower adsorption/desorption kinetics compared with the heavier D2. The results are discussed in terms of the adsorption mechanism.