Direct decomposition of NO over 8MR in high silica Cu-LTA zeolite: A DFT study on reaction mechanisms, thermodynamics and kinetics

Abstract

NO is a principal air pollutant that has received increasing attention due to its harmful impact on the environment and human health. Direct catalytic decomposition of NO to N2 is a process that carries promising potential with further development of metal-exchanged zeolitic catalysts, while the challenge lies with the thermal durability of the catalysts. Several reports have cited Cu-loaded high silica to aluminium ratio (SAR) Linde Type A (LTA) zeolites to be effective deNOx catalysts with their high catalytic activity and hydrothermal stability, but the detailed mechanisms by which it acts are still poorly understood. In this study, both the Eley-Rideal (E-R) and Langmuir-Hinshelwood (L-H) processes were discussed to elucidate a feasible reaction pathway that allows NO to be directly converted to N2O over the loaded-Cu in the eight-member ring (8MR) of the high silica LTA. The results have indicated that the L-H process is the most favourable pathway for the given temperature window (298.15–900 K). In addition, as the oxidation intermediate Cu-O hindered the desired NO conversion, multiple gaseous components (NO, CO, N2) that frequently existed in the catalytic process were considered for residual O (Ores) removal. NO and CO were both determined to be more favourable than N2 as reductants for the Ores removal, in consideration of their kinetic and thermodynamic characters. As a result, the high silica Cu-LTA showed catalytic feasibility in direct NO conversion from mechanistic insights.