TY - JOUR
T1 - Efficient approach for the computational study of alcohol and nitrile adsorption in H-ZSM-5
AU - Van Der Mynsbrugge, Jeroen
AU - Hemelsoet, Karen
AU - Vandichel, Matthias
AU - Waroquier, Michel
AU - Van Speybroeck, Veronique
PY - 2012/3/8
Y1 - 2012/3/8
N2 - Since many industrially important processes start with the adsorption of guest molecules inside the pores of an acidic zeolite catalyst, a proper estimate of the adsorption enthalpy is of paramount importance. In this contribution, we report ab initio calculations on the adsorption of water, alcohols, and nitriles at the bridging Brønsted sites of H-ZSM-5, using both cluster and periodic models to account for the zeolite environment. Stabilization of the adsorption complexes results from hydrogen bonding between the guest molecule and the framework, as well as from embedding, i.e., van der Waals interactions with the pore walls. Large-cluster calculations with different DFT methods, in particular B3LYP(-D), PBE(-D), M062X(-D), and B97X-D, are tested for their ability to reproduce the experimental heats of adsorption available in the literature (J. Phys. Chem. B1997, 101, 3811-3817). A proper account of dispersion interactions is found to be crucial to describe the experimental trend across a series of adsorbates of increasing size, i.e., an increase in adsorption enthalpy by 10-15 kJ/mol for each additional carbon atom. The extended-cluster model is shown to offer an attractive alternative to periodic simulations on the entire H-ZSM-5 unit cell, resulting in virtually identical final adsorption enthalpies. Comparing calculated stretch frequencies of the zeolite acid sites and the adsorbate functional groups with experimental IR data additionally confirms that the cluster approach provides an appropriate representation of the adsorption complexes.
AB - Since many industrially important processes start with the adsorption of guest molecules inside the pores of an acidic zeolite catalyst, a proper estimate of the adsorption enthalpy is of paramount importance. In this contribution, we report ab initio calculations on the adsorption of water, alcohols, and nitriles at the bridging Brønsted sites of H-ZSM-5, using both cluster and periodic models to account for the zeolite environment. Stabilization of the adsorption complexes results from hydrogen bonding between the guest molecule and the framework, as well as from embedding, i.e., van der Waals interactions with the pore walls. Large-cluster calculations with different DFT methods, in particular B3LYP(-D), PBE(-D), M062X(-D), and B97X-D, are tested for their ability to reproduce the experimental heats of adsorption available in the literature (J. Phys. Chem. B1997, 101, 3811-3817). A proper account of dispersion interactions is found to be crucial to describe the experimental trend across a series of adsorbates of increasing size, i.e., an increase in adsorption enthalpy by 10-15 kJ/mol for each additional carbon atom. The extended-cluster model is shown to offer an attractive alternative to periodic simulations on the entire H-ZSM-5 unit cell, resulting in virtually identical final adsorption enthalpies. Comparing calculated stretch frequencies of the zeolite acid sites and the adsorbate functional groups with experimental IR data additionally confirms that the cluster approach provides an appropriate representation of the adsorption complexes.
UR - http://www.scopus.com/inward/record.url?scp=84858124804&partnerID=8YFLogxK
U2 - 10.1021/jp2123828
DO - 10.1021/jp2123828
M3 - Article
AN - SCOPUS:84858124804
SN - 1932-7447
VL - 116
SP - 5499
EP - 5508
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 9
ER -