Adsorption sensitivity of nanocrystalline B-substituted H-ZSM-5 and alkali metal-exchanged M-ZSM-5 zeolites towards parent nitrosamine: A B97D study

摘要

In this work, the adsorption of parent nitrosamine (NA) on the Bronsted acid sites of B-substituted H-ZSM-5 and alkali metal-exchanged zeolites was investigated using the quantum 10T cluster at B97D/6-311++G(d,p) level and 46T model at the ONIOM(B97D/6-311++G(d,p):HF/STO-3G) level of theory. The influence of cluster size on the interaction between NA and zeolites was explored. The extended zeolite framework significantly increased the adsorption energy of NA on the zeolites. From the comparison of adsorption energies, the trend for acid strength of acidic sites was predicted to be B/ZSM-5 < Al/ZSM-5. The adsorption energies of NA on alkali metal-exchanged zeolites were decreased when the cations were changed from Li+ to Na+, in agreement with the lower acidity of the Na+ ion compared to the Li+. In addition to the main H(M)(z)center dot center dot center dot O interaction, stability of all complexes was affected by the NH center dot center dot center dot O-z interactions. Besides, interaction between NA and the ZSM-5 zeolites was examined using the atoms in molecules (AIM) and natural bond orbital (NBO) analyses. The comparison of rho(r) at O center dot center dot center dot H-5(M) BCP of Al/10T and B/10T complexes showed that the interactions in Al complexes are stronger than B ones. We have found a correlation between calculated adsorption energies and CT values. (C) 2015 Elsevier B.V. All rights reserved.