Catalytic oxidation of 1,2-dichlorobenzene over CoxCry oxides

Abstract

Co_xCr_y mixed oxides were synthesized to investigate the catalytic combustion of chlorinated aromatics with 1,2-dichlorobenzene (1,2-DCB) as model compound. Characterizations show Cr can exist as Cr⁶⁺O_x on Co₃O₄ surface or be incorporated as Cr-O-Co into Co₃O₄, which increases the dispersion of Co₃O₄. However, CrO₂ appears and Co is conversely dispersed into CrO₂ when Cr/Cr+Co = 0.4 or higher. Co₇Cr₃ shows best catalytic activity for 1,2-DCB oxidation with T₉₀ of 288 ℃, and its 1,2,4-trichlorobenzene selectivity is below 0.06 % during whole process, much lower than Co₃O₄ (45 %) and Co₅Cr₅ (50 %). The synergism of Cr⁶⁺ and Cr-O-Co in spinel matrix contributes to the strong acidity and superior reducibility, ensuring the quick Cl removal and inhibiting the chlorination of 1,2-DCB through accelerating Deacon process, while CrO₂ suffers severe Cl deposition and Cr loss. Accordingly, Co_xCr_y catalysts with spinel structure present excellent performance and stable activity at 300 ℃ for at least 50 h.