Significant inhibition of secondary pollution in the catalytic oxidation of chloroaromatics over a bifunctional Ru1/CeO2 single-atom catalyst

Abstract

Although catalytic oxidation is a promising technique for chlorine-containing volatile organic compound removal, it is still challenging to improve its selectivity to avoid secondary pollution. Herein, we reported an atomically dispersed ruthenium catalyst coordinated with oxygen atoms in ceria (Ru₁/CeO₂, the theoretical loading of Ru is 1 wt%) to enhance the catalytic selectivity toward chlorobenzene (CB) oxidation. In 1000 ppm CB/5 vol% H₂O/air streams (GHSV = 30 000 mL g⁻¹ h⁻¹), Ru₁/CeO₂ shows a high reaction rate and turnover of frequency of 0.83 mmol g⁻¹ h⁻¹ and 8.07 h⁻¹ at 200 °C, without Cl₂ formation. Both experimental results and theoretical calculations prove that the Ru binds to the hollow site formed by three oxygen atoms of CeO₂(111) with moderate oxygen vacancy concentration and higher dissociation energies of Cl at Ru₁/CeO₂, enabling the inhibition of intermediate (HCl) conversion to Cl₂ and stepwise formation of polychlorinated by-products (Cl > 2), making it an order of magnitude less by-products than the RuO₂ nanoparticles.