Synergistic roles of Ru, CeO2, and HZSM-5 in a ternary-active center catalyst for catalytic destruction of dichloromethane

Abstract

Developing well-qualified industrial catalysts with excellent oxidation ability, selectivity, and resistance is still a challenge for chloroalkane destruction. Herein, we optimized the composition of multi-component catalysts with diverse active sites to adjust their acidic and redox properties for reasonable catalytic performance. The synergy of redox center Ru, activation center CeO2, and acid center HZSM-5 endowed the ternary catalyst Ru/CeO2/HZSM-5 with superior low-temperature activity (30 ∼ 60 °C lower for 50 % conversion), promoted stability and chlorine tolerance (100 % conversion for at least 30 h), and less toxic by-products for dichloromethane (DCM) destruction compared with the binary ones, promising for industrial application under tough conditions (e.g., thermal shock, HCl, H2O). The strong interaction of Ru and CeO2 enhanced the redox property of Ru/CeO2/HZSM-5 and thus promoted the deep oxidation of DCM and intermediates, thereby generating more CO2 and less dechlorinated by-products (e.g., CH3Cl). The synergistic effects of Ru, CeO2, and HZSM-5 facilitated chlorine removal and suppressed the generation of polychlorinated by-products (e.g., CHCl3) over the Ru/CeO2/HZSM-5 catalyst by improving redox capacity and inhibiting reactivity of chlorine. Notably, the introduction of CeO2 weakened the hydrophilicity of Ru and HZSM-5, improving the water resistance of the catalyst. The corresponding monolithic catalyst could achieve complete oxidation of DCM at 400 °C with the total concentration of dioxins measured at 0.026 ng I-TEQ kg−1 after continuous operation at 250 °C for 30 h.