Catalyst in-situ regeneration for polychlorinated biphenyl tail gas degradation and catalytic activity recovery mechanisms

To address the problems with catalytic degradation, such as poisoning and inactivation, a simple and efficient gas purging regeneration technique was developed for iron-based catalyst in-situ regeneration. Specifically, the effects of carrier gas types, regeneration temperatures, and granular activated carbon (GAC) addition on iron-based catalyst regeneration were investigated. The Fe₃O₄/γ-Al₂O₃ regenerated at 550 °C with additional GAC and 15 % water vapor exhibited the optimal degradation efficiency towards polychlorinated biphenyls (PCBs), with an increase from 41.2 % to 93.5 %, compared with non-regenerated Fe₃O₄/γ-Al₂O₃. In addition, the 60-hour stability test revealed a well-recovered catalytic activity. During the Fe₃O₄/γ-Al₂O₃ regeneration, the coke on the catalyst surface was oxidized and removed in the form of CO₂, and meanwhile the oxidized Fe(III) was reduced into Fe(II) in the catalyst. This study provides a safe and efficient iron-based catalyst regeneration technology for PCB off-gas degradation and reveals the catalytic activity recovery mechanism during catalyst regeneration.