Gas-Phase Regeneration of Metal-Poisoned V 2 O 5 -WO 3 /TiO 2 NH 3 -SCR Catalysts via a Masking and Reconstruction Strategy.

Renewing metal-poisoned NH 3 -SCR catalysts holds great potential for mitigating environmental pollution and utilizing hazardous wastes simultaneously. Ionic compounds containing heavy metals often exhibit limited solubility due to their high polarizability, making traditional washing techniques ineffective in removing heavy metal poisons. This study presents a gas-based method for regenerating heavy-metal-poisoned V 2 O 5 -WO 3 /TiO 2 catalysts employed in NH 3 -SCR techniques. The regeneration is achieved by employing a masking and reconstruction strategy, which involves the in situ formation of NO 2 to mediate the production of SO 3 . This enables the effective bonding of Pb and triggers the reconstruction of active VO x sites. In situ spectroscopy confirms that the sulfation of PbO restores acidity, while the occupied effect resulting from the sulfation of TiO 2 promotes the formation of more polymeric VO x species. Consequently, the regenerated catalyst exhibits enhanced activity and superior resistance to metal poisons compared with the fresh catalyst. The innovative method offers a promising solution for extending the lifespan of poisoned catalysts, reducing waste generation, and enhancing the efficiency of NH 3 -SCR systems.