1. Otto-von-Guericke University Magdeburg, Universitätsplatz 2, D-39106 Magdeburg, Germany;2. Max Planck Institute for Dynamics of Complex Technical Systems, Sandtorstrasse 1, D-39106 Magdeburg, Germany;1. State Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing University of Technology, Nanjing 210009, PR China;2. College of Mechanic and Power Engineering, Nanjing University of Technology, Nanjing 210009, PR China
Abstract:
We have performed embedded-cluster calculations using density functional theory to investigate mechanisms of nitrogen substitution (nitridation) in HY and silicalite zeolites. We consider nitridation as replacing Si–O–Si and Si–OH–Al linkages with Si–NH–Si and Si–NH2–Al, respectively. We predict that nitridation is much less endothermic in HY (29 kJ/mol) than in silicalite (132 kJ/mol), indicating the possibility of higher nitridation yields in HY. To reveal mechanistic details, we have combined for the first time the nudged elastic band method of finding elusive transition states, with the ONIOM method of treating embedded quantum clusters. We predict that nitridation of silicalite proceeds via a planar intermediate involving a Graphical abstractThe mechanism of nitridation in HY and silicalite is revealed using denstiy functional theory. The barriers for forward and backward processes are large, indicating that nitrided zeolites are stable once formed.
Graphical abstractThe mechanism of nitridation in HY and silicalite is revealed using denstiy functional theory. The barriers for forward and backward processes are large, indicating that nitrided zeolites are stable once formed.