Effective regeneration of thermally deactivated commercial V-W-Ti catalysts

An effective method for the regeneration of thermally deactivated commercial monolith SCR catalysts was investigated. Two types of regenerated solutions, namely NH ₄Cl (1 mol/L) and dilute H ₂SO ₄ (0. 5 mol/L), were employed to treat the used catalyst. The effects of temperature and the regeneration process on the structural and textural properties of the catalysts were determined by X-ray diffraction, scanning electron microscopy, N ₂ adsorption/desorption, elemental analysis and Fourier transform infrared spectroscopy. The results suggest that the anatase phase of the used catalyst is maintained after exposure to high temperatures. Some of the catalytic activity was restored after regeneration. The catalyst regenerated by aqueous NH ₄Cl had a higher activity than that of the catalyst treated by dilute H ₂SO ₄. The main reason is that the NH3 generated from the decomposition of NH ₄Cl at high temperatures can be adsorbed onto the catalyst which promotes the reaction. The aggregated V ₂O ₅ were partially re-dispersed during the regeneration process, and the intrinsic oxidation of ammonia with high concentrations of O ₂ is a factor that suppresses the catalytic activity.