Implication of Operation Time on Low-Temperature Catalytic Oxidation of Chloroaromatic Organics Over Vox/Tio2 Catalysts : Kinetic and Characteristic Analysis

Three commercial granular catalysts were collected according to their operation time (fresh, two years, and three years, defined as Cata-1, Cata-2, and Cata-3, respectively). The catalytic efficiency (CE) and CO 2 /CO/HCl selectivity of 1,2-dichlorobenzene (1,2-DCB) were investigated at low temperature (150-200 °C), which was obviously decreased as the operation time extended and positively related to the reaction temperature. The CO 2 /CO and HCl selectivity shared similar trend of CE. The catalytic reaction rate ( k ) and apparent activation energy (E a ) further supported the above results, which were decreased as Cata-1 (1.59-2.18 s -1 , 11.01 kJ/mol)>Cata-2 (0.12-0.38 s -1 , 34.44 kJ/mol)>Cata-3 (0.007-0.125 s -1 , 92.70 kJ/mol), respectively. According to the characteristic results and their correlation coefficient (R 2 ) with 1/E a , the implication of operation time was mainly attributed to the S-poisoning and the accumulation of foreign substances, which was specifically reflected in decreasing proportion of (1) active components (V 2 O 5 and TiO 2 ), (2) proportion of V 5+ and O surf , (3) surface area, (4) pore volume, (5) redox ability, (6) weak acid sites, and increasing the proportion of SO 3 and SiO 2