Determining hydrothermal deactivation mechanisms on Cu/SAPO-34 NH3-SCR catalysts at low- and high-reaction regions: establishing roles of different reaction sites

Hydrothermal deactivation is a constant challenge in commercial catalytic process aimed at NOx emission control, which may be observed in the low (150–400 °C) or high (400–550 °C)-reaction regions. To the best of our knowledge, there is a lack of systematic research regarding the correlation between the reaction sites and the mechanism of hydrothermal degradation at various reaction regions. For a targeted investigation of this, Cu/zeolite catalysts have been prepared using different amounts of polyvinyl alcohol for adjusting their redox and acid properties. These catalysts exhibit hydrothermal deactivation in different reaction regions. No change is observed in the reaction mechanism even with hydrothermal deactivation, but various reaction sites determine the performance deterioration in the low- and high-reaction regions. The redox properties and weak acid sites affect the hydrothermal deactivation in the low-reaction region, whereas the moderate/strong acid sites related to the structure mainly influence the hydrothermal deactivation in the high-reaction region. This work provides several theoretical insights for optimizing the hydrothermal stabilities of Cu/zeolite catalysts.