Insight into the design and construction of Cr substituted Co-based columnar activated coke catalysts for effective and reliable removal of methylbenzene and Hg0 concurrently

An array of CoCr oxides co-modified activated cokes pretreated with HNO3 (XCoyCr1-y/ACs) were synthesized and evaluated for simultaneously effective and credible elimination of methylbenzene (MB) and Hg0. BET, SEM, TEM, EDX, XRD, H2-TPR, in situ DRIFTS and XPS were adopted for exploring the physicochemical characteristics and reaction mechanisms of aforesaid samples. H2-TPR result showed the Cr-doped Co-Cr catalysts excellent reducibility in view of the synergistic effect between CoOx and CrOx. Especially, 6 %Co0.5Cr0.5/AC obtained outstanding performance and prominent stability for MB and Hg0 removal, and it behaved the optimal performance of MB (96.1 %) and Hg0 (88.3 %) at 240 ℃. It could be explained by that the formation of CoCr2O4 spinel entailed more uniform distribution of active components, abundant lattice defects and even the redox cycle of Cr6++Co2+↔Cr3++Co3+, which spawned adequate Co3+ species and active oxygen species. The interaction between MB removal and Hg0 removal was estimated and the presence of Hg0 barely affected MB removal, whereas the existence of MB manifested a distinctly suppressive influence on Hg0 removal, suggesting that MB removal might prevail over Hg0 removal. Meanwhile, the rivalry between MB and Hg0 progressively shifted from adsorption sites to active oxygen species with time. Moreover, the influences of O2, NO, SO2 and H2O on MB and Hg0 simultaneous removal were systematically appraised. Notably, 6 %Co0.5Cr0.5/AC exerted remarkable resistance to SO2 and H2O. Combined with characterizations and experiments, the pathway for the simultaneous removal of MB and Hg0 via adsorption and catalytic oxidation on 6 %Co0.5Cr0.5/AC was summarized. This work could deliver references to the design of advanced catalysts for simultaneous removal of MB and Hg0.