Implication Mechanism of Operation Time on Low-temperature Catalysis of Chloroaromatic Organics over VO_x/TiO₂ Catalysts

Abstract

Three commercial granular catalysts were collected according to their operation time (fresh, two years, and three years, denoted as Cata-1, Cata-2, and Cata-3, respectively). The catalytic efficiency and CO₂/CO/HCl selectivity of 1,2-dichlorobenzene were investigated at low temperature (150-200 ℃). The Cata-1 showed excellent catalytic activities with high conversion efficiency (CE, 76.12-85.94%), CO₂/CO selectivity (77.56-82.47%), and HCl selectivity (63.74-72.54%). The catalytic activities of Cata-2 and Cata-3 were distinctly reduced due to the irreversible deactivation and poisoning. Based on the abundant characteristic results, the deactivation and poisoning effects are mainly caused by decreasing the surface acidity and porous parameters, disturbing the redox cycle of VO_x and reactive oxygen species, competing for active oxygen species, and blocking active sites. Based on this study, two improvement suggestions were proposed: (1) develop new reactivated technologies, aim to reduce deposition of foreign substances; (2) develop new catalysts by introducing second active component (eg., WO_x, MoO_x, CeO_x, etc.) and reducing VO_x content to improve the anti-poisoning abilityand the redox ability. This study can guide the design and improvement of the granular catalyst and facilitate the synergistically emission control of chloroaromatic organics and NO_x from MSWI.