TY - JOUR
T1 - Porous materials for steady-state NO conversion
T2 - Comparisons of activated carbon fiber cloths, zeolites and metal-organic frameworks
AU - Hu, Ming Ming
AU - Zhang, Zhanquan
AU - Atkinson, John D.
AU - Rood, Mark J.
AU - Song, Linhua
AU - Zhang, Zailong
N1 - Publisher Copyright:
© 2018 Elsevier B.V.
PY - 2019/3/15
Y1 - 2019/3/15
N2 - It is important to develop new materials/methods to remove NO from gas streams to protect the environment. Use of porous materials to catalytically convert NO to NO2 may improve existing NOx control technologies. In this work, three porous materials (i.e., activated carbon fiber cloths (ACFCs), zeolites, and metal-organic frameworks (MOFs)) were evaluated as NO oxidation catalysts at 25 °C. Maximum included sphere diameter (Di) between 5.5 and 11.0 Å is shown to result in higher steady-state NO conversion (23%−71.5 ± 2.5%) by providing appropriate channels/cages that accommodate and stabilize the first transition state (TS1) through van der Waals interactions. For all considered catalysts but MIL-53 (Al), steady-state NO conversion initially increases, then decreases, with increasing pore volume contributed by Di (5.5–11.0 Å). Maximum free sphere diameter (Dmax) for the selected catalysts with steady-state NO conversion between 23% and 71 ± 2.5% is between 3.7 and 9.0 Å allowing transport of reactants and products. Extra-framework cations (H+, NH4+, and Na+) and coordinatively unsaturated sites (Cu2+, Fe3+, and Cr3+) increase steady-state NO conversion by providing TS1 stabilization through electrostatic and coordinative interactions, respectively. However, appropriate Di and Dmax values are identified as the most influential variables for steady-state NO conversion using these catalysts. For NO conversion in the presence of SO2, no impact is observed for steady-state NO conversion of a MOF sample, but decreases of 100% and 36% for ACFC and zeolite samples, respectively. These results provide direction for designing NO oxidation catalysts to improve steady-state NO conversion.
AB - It is important to develop new materials/methods to remove NO from gas streams to protect the environment. Use of porous materials to catalytically convert NO to NO2 may improve existing NOx control technologies. In this work, three porous materials (i.e., activated carbon fiber cloths (ACFCs), zeolites, and metal-organic frameworks (MOFs)) were evaluated as NO oxidation catalysts at 25 °C. Maximum included sphere diameter (Di) between 5.5 and 11.0 Å is shown to result in higher steady-state NO conversion (23%−71.5 ± 2.5%) by providing appropriate channels/cages that accommodate and stabilize the first transition state (TS1) through van der Waals interactions. For all considered catalysts but MIL-53 (Al), steady-state NO conversion initially increases, then decreases, with increasing pore volume contributed by Di (5.5–11.0 Å). Maximum free sphere diameter (Dmax) for the selected catalysts with steady-state NO conversion between 23% and 71 ± 2.5% is between 3.7 and 9.0 Å allowing transport of reactants and products. Extra-framework cations (H+, NH4+, and Na+) and coordinatively unsaturated sites (Cu2+, Fe3+, and Cr3+) increase steady-state NO conversion by providing TS1 stabilization through electrostatic and coordinative interactions, respectively. However, appropriate Di and Dmax values are identified as the most influential variables for steady-state NO conversion using these catalysts. For NO conversion in the presence of SO2, no impact is observed for steady-state NO conversion of a MOF sample, but decreases of 100% and 36% for ACFC and zeolite samples, respectively. These results provide direction for designing NO oxidation catalysts to improve steady-state NO conversion.
KW - Activated carbon fiber cloths
KW - Metal-organic frameworks
KW - NO oxidation
KW - Zeolites
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U2 - 10.1016/j.cej.2018.11.102
DO - 10.1016/j.cej.2018.11.102
M3 - Article
AN - SCOPUS:85057320294
SN - 1385-8947
VL - 360
SP - 89
EP - 96
JO - Chemical Engineering Journal
JF - Chemical Engineering Journal
ER -