Adsorption of parent nitrosamine on the nanocrystaline M-ZSM-5 zeolite: A density functional study

摘要

The adsorption of parent nitrosamine (NA) on the Br??nsted acid sites of M-ZSM-5 (M = H, Li and Na) zeolites have been investigated via the utilization of 10T cluster model by density functional calculations, at the B3LYP/6-311++G(d,p) level. Two A and B complexes with two types O(N)a€|M and NHa€|OZ interactions were predicted from adsorption of nitrosamine on the M-zeolite clusters. The comparison of interaction energies shows that the order of energies for adsorption of NA on the Br??nsted acid site of M-ZSM-5 is Na Li H for the A complexes and Li H for the B complexes. The calculated adsorption enthalpy of NA on the Br??nsted acid site of 10T cluster of M-ZSM-5 catalyst ranges from a?’14.41 to a?’52.95 kJ/mol. The acid strength of H-ZSM-5 was found to exceed those of the corresponding to the alkali metal ion-exchanged zeolites. The results reveal that the interaction between hydrogen of NA and OZ of framework is weaker than O(N)a€|M one. The NHa€|OZ and O(N)a€|HZ hydrogen bonds in these complexes are electrostatic and partially covalent in nature, respectively. The results of natural bond orbital (NBO) analysis showed that charge transfer occurs from NA to M-zeolite cluster.