Boosting catalytic activity of Ag-modified CeO2-Al2O3 mixed metal oxide support via coupling with a VUV photoreactor: A catalytic ozonation system applied towards VOC oxidation

Abstract

This study introduces a new air purification strategy that combines a vacuum ultraviolet (VUV) photoreactor as an in-situ source of O₃ generation coupled with a fixed-bed ozonation reactor equipped with Ag-based catalysts. The results showed that the integration of the VUV photoreactor to the fixed-bed reactor significantly enhanced not only the conversion of acetone but also improved the O₃ decomposition compared to the catalytic ozonation system alone in that the acetone and O₃ conversion were boosted from 82 % and 86 %, respectively, to 100 % each. While the inhibitory impact of relative humidity (RH) on Ag/CeO₂−Al₂O₃ activity using a fixed bed reactor was detected, coupling with the VUV photoreactor led to maintaining 100 % conversion of acetone and ozone even in the humid condition. Indeed, although RH poisoned the interface of the gas-catalyst, leading to an inhibition role in the catalytic reactions, it improved the VUV photolysis performance in the gaseous state, resulting in the enhancement of the coupled reactor’s performance compared to the only catalytic ozonation fixed bed reactor. Additionally, the in-situ regeneration capability, which was introduced to the air treatment system by combining the VUV photoreactor with the traditional catalytic ozonation, granted prolonged reusability of the catalyst with minimal activity reduction (less than 2 %). The attained data showed that the presence of binary metal oxide supports with an optimized 1:1 ratio had a key role in maintaining not only a complete conversion of acetone and ozone but also achieving above 99 % reaction selectivity towards complete oxidation. Finally, a mechanistic study was conducted where the in-situ diffuse reflectance infrared Fourier transform (DRIFT) analysis proved the role of surface carboxylate and electron paramagnetic resonance (EPR) data demonstrated the co-participation of ^.OH/^.O₂⁻ radicals in acetone removal.