Abstract
A novel strategy for toluene abatement was investigated using a sequential adsorption-regeneration process. Commercial Hopcalite (CuMn2Ox, Purelyst101MD), Ceria nanorods, and UiO-66-SO3H, a metal–organic framework (MOF), were selected for this study. Toluene was first adsorbed on the material and a mild thermal activation was performed afterwards in order to oxidize toluene into CO2 and H2O. The materials were characterized by XRD, N2 adsorption-desorption analysis, H2-TPR and TGA/DSC. The best dynamic toluene adsorption capacity was observed for UiO-66-SO3H due to its hierarchical porosity and high specific surface area. However, in terms of balance between storage and catalytic properties, Hopcalite stands out from others owing to its superior textural/chemical properties promoting irreversible toluene adsorption and outstanding redox properties, allowing a high activity and CO2 selectivity in toluene oxidation. The high conversion of toluene into CO2 which easily desorbs from the surface during heating treatment shows that the sequential adsorption-catalytic thermal oxidation can encompass a classical oxidation process in terms of efficiency, CO2 yield, and energy-cost saving, providing that the bifunctional material displays a good stability in repetitive working conditions.
Highlights
Volatile organic compounds (VOCs) usually refer to organic compounds with boiling points less than or equal to 250 ◦ C at atmospheric pressure and high vapor pressures at room temperature [1,2]
The X-ray diffraction (XRD) pattern of the as-synthesized CeO2 -NR shows well defined diffraction peaks located at 28.5◦, 33.1◦, 47.5◦, 56.3◦, 59.1◦, 69.4◦, 76.7◦, and 79.1◦ ascribed to the (111), (200), (220), (311), (222), (400), (331), and (420) planes of the face-centered cubic CeO2 fluorite structure (JCPDS 34−0394, space group Fm3m) [24]
Only a single adsorption-catalytic combustion sequence was performed in each case, this study shows that the Hopcalite stands as a good candidate due to its adsorption and redox properties
Summary
Volatile organic compounds (VOCs) usually refer to organic compounds with boiling points less than or equal to 250 ◦ C at atmospheric pressure and high vapor pressures (above 0.1 mm Hg) at room temperature [1,2]. Storage regeneration processes have been proposed and investigated to eliminate low-concentration indoor VOCs such as formaldehyde and benzene [9]. This sequential method implies two steps: (i) first, the VOC is adsorbed on a material and (ii) a regeneration of the material through VOC oxidation into CO2 and H2 O is performed. A key issue in this approach is the design of adsorbent/catalytic materials which should possess balanced properties between storage and regeneration. The bifunctional materials used for the storage of VOCs should possess high and selective VOC storage capacity, and be regenerated without any release of the VOCs or generation of secondary pollutants. Thermal regeneration [9], non-thermal plasma oxidation [10,11], or ozone enabled regeneration [12] have been assessed as regeneration methods
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