The potential utility of HKUST-1 for adsorptive removal of benzene vapor from gaseous streams using a denuder versus a packed-bed adsorption system

Abstract

The feasibility of various sorption methods has been explored to remove volatile organic compounds from indoor air (e.g., a packed bed-based air filtration system). However, the large space velocity/pressure drop is a common operational challenge associated with the use of a packed-bed adsorber, especially when using fine powdery adsorbent. Accordingly, this research was carried out to evaluate the effectiveness of two contrasting adsorptive removal systems (i.e., denuder vs. packed-bed) using a metal-organic framework (MOF: Hong Kong University of Science and Technology (HKUST-1) as a model adsorbent) as the test media. In the denuder design, HKUST-1 was coated as a thin layer (thickness 90 mm) on the inner wall of a 90 mm length quartz tube (internal diameter approximate to 4 mm) with the help of a polyvinyl alcohol binder. Additionally, an identical quartz tube was prepared with a HKUST-1 packed bed. The potential applicability of the denuder versus packed-bed was evaluated using gaseous benzene (0.1-10 partial pressure) in a N-2 inlet stream at near-ambient conditions (298 K and 1 atm). A comparison of the breakthrough volume and adsorption performance data (capacity and partition coefficient) revealed that the packed bed outperformed the denuder design by four to five-fold at all inlet benzene partial pressures (0.1-10 Pa). Better performance was seen in the denuder system when benzene uptake was conducted at high benzene partial pressures (5-10 Pa) rather than at low partial pressure (˂5 Pa) in the inlet stream. The evaluation of pressure drop data indicated the efficacy of the denuder over a packed bed in terms of pressure/space velocity drop, especially at a high flow rate (e.g., 330 mL min(-1)). However, in terms of uptake rate and space time yield, the denuder was 25 times less efficient than the packed bed.