Flowerlike structured Cu promoted MnOx catalysts for VOC oxidation: Enhanced water vapor resistance in simulated coal-fired flue gas

Water poisoning remains a significant challenge for Mn-based catalysts in the purification of low-temperature industrial flue gas. In this study, a water-resistant catalyst, Cu-doped MnO x dispersed on a flower-like hollow sphere carrier (Cu 0.1 Mn 1 -Al 2 O 3 (NF)), was developed. The introduction of 5 % water vapor into simulated flue gas reduced the o-xylene oxidation efficiency of the unmodified MnO x /γ-Al 2 O 3 catalyst by 20 %, whereas Cu 0.1 Mn 1 -Al 2 O 3 (NF) exhibited only a 5 % reduction, and it shows a water resistance surpasses those of most of the reported MnO x catalysts. Upon water vapor withdrawal, Cu 0.1 Mn 1 -Al 2 O 3 (NF) showed a 2 % irreversible efficiency loss, compared to 9 % for MnO x /γ-Al 2 O 3 . Mechanistic studies highlight the role of the flower-like morphology in reducing hydrogen-bonded H 2 O and the primary contribution of Cu + doping in suppressing –OH generation on metal sites, likely due to weakened H 2 O dissociation at Mn-Ov-Cu oxygen vacancies. Additionally, Cu 0.1 Mn 1 -Al 2 O 3 (NF) has improved water desorption capability evidenced by 8 °C lower endothermic temperature for H 2 O volatilization than that of MnO x /γ-Al 2 O 3 . Furthermore, a H 2 O-involved Mars-van Krevelen (MvK) mechanism was proposed to explain the ∼ 2 % irreversible efficiency reduction for Cu 0.1 Mn 1 -Al 2 O 3 (NF) in wet gas − attributed to H 2 O dissociation at oxygen vacancies hindered lattice oxygen replenishment. Based on this mechanism, an air-purging regeneration protocol was developed to enhance the catalyst’s operational stability under wet flue gas conditions.