Coal gasification fine slag-assisted regeneration of sulfur-poisoned V2O5-WO3/TiO2 catalysts and its mechanism for enhancing NH3-SCR performance

In ammonia selective catalytic reduction of NO x (NH 3 -SCR) technology, V 2 O 5 -WO 3 /TiO 2 catalysts are frequently poisoned by sulfur dioxide contained in the flue gas, resulting in decreased catalytic activity and eventual deactivation, which exacerbates the environmental burden. This study developed a simple mechanical grinding strategy for regenerating the sulfur-poisoned catalysts in powder form by adding coal gasification fine slag (CGFS), and thereby significantly enhancing the deNO x efficiency. Activity data indicate that after being mixed with CGFS, the deNO x efficiency of the poisoned catalyst increases from 10.3 % to 71.6 % at 250 °C. Characterizations were systematically conducted to reveal the mechanism of activity enhancement. It was found that the silicoaluminates of CGFS can migrate the deposited sulfur species away from the surface of poisoned catalysts, thereby releasing the blocked vanadium active sites. On the other hand, the porous carbon fraction in CGFS also plays a crucial role: it promotes the adsorption of more reactive nitrate species (i.e., nitrite and bridged bidentate nitrate), facilitates the formation of adsorbed oxygen, and enhances the generation of NH 4 + , thereby synergistically improving deNO x efficiency. Under the synergistic effect of the ash and carbon fraction in CGFS, the activity of the regenerated catalyst even exceeds that of a fresh catalyst at some temperatures. This work offers a novel and cost-effective pathway for the efficient regeneration of sulfur-poisoned NH 3 -SCR catalysts, while realizing the high-value utilization of CGFS.