Adsorption of parent nitrosamine on the nanocrystaline H–zeolite: A theoretical study

Adsorption of parent nitrosamine (NA) on 5T and 10T cluster models of H–ZSM-5 catalyst has been theoretically investigated using quantum chemical B3LYP and MP2 methods. Three stable complexes (A–C) were found on the potential energy surface of interaction between NA and cluster models of H–ZSM-5. NA can interact not only with acidic site of zeolite via the lone electron pair on nitrogen and oxygen atoms (O(N)⋯HZO) but also with the oxygen atoms of the framework via the hydrogen atoms of NH2 group (NH⋯O) as well. However, the Lewis acidity of zeolite framework is the dominating factor in the interaction between NA and zeolite. The calculated adsorption enthalpy of NA on 5T and 10T clusters of H–ZSM-5 catalyst at ONIOM(MP2/6-311++G(d,p):HF/6-31+G(d)) level ranges from −19.73 to −40.33 and −63.81 to −73.73 kJ/mol, respectively. Adsorption energy for A–C complexes increases in going from B3LYP method to MP2 one. The results of atoms in molecules (AIM) calculations showed that NH5⋯O interactions have electrostatic character, whereas O(N)⋯HZ interactions have partially covalent nature. The results of natural bond orbital (NBO) analysis showed that charge transfer occurs from NA to H–zeolite cluster.