Comparative study of ruthenium oxide loaded on amorphous UiO-66-NH2 and the derived ZrO2 in HCl oxidation to chlorine

The catalytic oxidation of HCl to Cl2 over RuO2-based catalysts is a significant process for chlorine recycling in chemical industry. In this study, an amorphous zirconium-based metal-organic framework (denoted by aUiO-66-NH2) and its derived metal oxide (denoted by ZrO2-aU) were utilized as carriers to construct RuO2-based catalysts. The XRD, XPS, SEM, STEM, H2-TPR, CO pulse, N2 adsorption-desorption and XAFS characterizations of RuO2/ZrO2-aU and RuO2/aUiO-66-NH2 catalysts indicated that, under the inducement of reaction atmosphere, the carrier aUiO-66-NH2 transforms to partially chlorinated t-ZrO2. Meantime, the RuO2 loaded on aUiO-66-NH2 diffuses into the crystal lattice of t-ZrO2, and finally form highly dispersed RuClxOy species stabilized in t-ZrO2, which leads to the higher activity than RuO2/ZrO2-aU. Comparatively, no structural transformation occurs for RuO2/ZrO2-aU catalyst, suggesting the advantage of the amorphous structure of aUiO-66-NH2 in constructing highly efficient catalysts.