Development of structured Co3O4-based catalyst for N2O removal from hospital ventilation systems

摘要

In this study, we developed a catalyst for the N2O removal from hospital ventilation system (0-2% N2O, 40-60% humidity, airflow, temperature window 400-600 degrees C). The catalyst is based on doubly promoted cobalt spinel supported on the cordierite monolith washcoated with alpha-Al2O3. A series of powder singly (K or Pb) and doubly (K and Pb) promoted and structured catalysts (K-Pb-Co3O4 vertical bar alpha-Al2O3 vertical bar cordierite) were obtained and thoroughly characterized by XRF, XRD, H-2 - TPR, TEM/EDX/SAED, work function techniques. The results indicate the catalytic activity of cobalt spinel can be dramatically enhanced by the addition of even minor amount of Pb. The catalytic performance was further expanded upon the addition of the potassium promoter. The presence of both dopants (K, Pb) in the Co3O4 active phase results in the synergistic promotional effects, which are discussed in terms of facilitating two main steps of N2O decomposition. Whereas K promoter favours electron transfer activation of N2O (initial step) the Pb dopant helps the recombination of the surface oxygen intermediates (closing the catalytic cycle). A long term time-on-stream (26 h) test in hospital ventilation gases proved excellent stability of the developed 0.25% K-1.8% Pb-10% Co3O4 vertical bar alpha-Al2O3 vertical bar cordierite catalyst with N2O conversion >80% at 400 degrees C (2000 h(-1)) and the thermal resistance to overheating (20 h at 600 degrees C).