Facile H₂O-Contributed O₂ Activation Strategy over Mn-Based SCR Catalysts to Counteract SO₂ Poisoning.

Area of Science:

• Catalysis
• Environmental Chemistry
• Materials Science

Background:

• Manganese-based catalysts are crucial for low-temperature selective catalytic reduction (SCR) but are vulnerable to sulfur dioxide (SO2) poisoning.
• SO2 poisoning leads to sulfate formation, hindering oxygen activation and reducing reactive oxygen species (ROS) essential for SCR reactions.
• Water (H2O) has traditionally been viewed as detrimental, exacerbating catalyst deactivation in the presence of SO2.

Purpose of the Study:

• To investigate the counterintuitive role of water in mitigating SO2 poisoning in Mn-based SCR catalysts.
• To elucidate the mechanism by which water enhances oxygen activation and ROS generation.
• To demonstrate the potential for catalyst regeneration using water under SO2 exposure.

Main Methods:

• Experimental investigation of Mn-based catalysts (specifically γ-MnO2) under conditions simulating SO2 and H2O exposure.
• Analysis of oxygen activation pathways and reactive oxygen species (ROS) generation.
• Evaluation of catalyst performance and regeneration efficiency through mild thermal treatment.

Main Results:

• Water synergistically activates oxygen, generating ROS that counteract SO2-induced deactivation.
• Water-induced reduction in activation energy (Ea) facilitates ROS formation and activity.
• The γ-MnO2 catalyst demonstrated complete regeneration of its NO removal capability after SO2 + H2O exposure and mild thermal treatment.
• The observed mechanism is applicable to various Mn-based SCR catalysts.

Conclusions:

• Water plays a beneficial role in Mn-based SCR catalysts, actively counteracting SO2 poisoning.
• The synergistic activation of O2 and H2O generates ROS, which are key to catalyst regeneration.
• This water-assisted strategy offers a promising approach for enhancing the durability and performance of Mn-based SCR catalysts in polluted environments.