Influence
of Framework Protons on the Adsorption Sites
of the Benzene/HY System
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Abstract
Monte
Carlo (MC) simulations were performed to study the influence
of framework protons on the adsorption sites of the benzene molecule
in HY zeolite with different Si:Al ratios. Eleven types of adsorption
sites were observed including five reported sites (H1, H2, U4, U4(H1),
and W) and six newfound sites (W(2H1), U4(2H1), H1(H2), U4(H1,H1),
H1(H2,H1), and U4(H1,H1,H1)), which were “supersites”
with more than one proton. The stability order of the sites found
in the 28Al model can be expressed as U4(H1,H1,H1) > U4(H1) >
H1(H2,H1)
> W(2H1) > U4(H1,H1) > H1(H2) > H1 > H2 > U4 >
U4(2H1) > W. Increasing
number of zeolite protons resulted in an increasing proportion of
supersites, which enhanced adsorption energies of sites. For HY zeolite
models containing different numbers of protons with the same ratio
of H1:H2, the amount of the most stable adsorption sites containing
H1 proton increased, while the amount of the most stable adsorption
sites containing H2 decreased, with increasing number of protons
