Recently, Ph.D. WenXiu Cao has made new progress in MOF derived single atom catalyst field: Using a new stabilization strategy based on the UiO-66 (Zr-MOF) material to prepare Ru/ZrO₂@C catalyst, and this Ru/ZrO₂@C showed an excellent catalytic activity and stability in the hydrogenation of levulinic acid (LA) to γ-valerolactone, with no apparent drop in catalytic performance observed in six consecutive runs in water and three consecutive runs in acidic reaction media (pH = 1). The study have published in Green Chemistry.

Article link:http://pubs.rsc.org/en/content/articlelanding/2017/gc/c7gc00512a#!divAbstract.

The hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) is a crucial reaction included in many biorefinery schemes for the production of renewable chemicals and fuels. The development of highly stable supported Ru-based catalysts in the polar protic liquid phase under hydrothermal conditions is still a major challenge. Here, we prepared a 0.85 wt% Ru/ZrO₂@C catalyst using a new stabilization strategy based on the UiO-66 (Zr-MOF) material. The catalytic performance of this Ru/ZrO₂@C in LA-to-GVL was tested and compared with commercial 5 wt% Ru/C at 10 bar H₂, 413 K in water and also in high protic aqueous solution (pH = 1). The full conversion of LA and quantitative yield of GVL were achieved with both catalysts. However, the 5 wt% Ru/C showed poor resistance to deactivation already after the first run. ICP, XPS, HRTEM, AC-STEM, TPR and physisorption data showed that quick deactivation of Ru/C was mainly caused by the leaching of ruthenium in addition to the loss of surface area via carbonaceous deposition in micro-pores. In contrast, the self-prepared Ru/ZrO₂@C catalyst showed no apparent drop in catalytic performance either in water or in high protic aqueous solution upon multiple recycling, and no leaching of ruthenium was found even under harsh conditions (pH = 1). Remarkably, in the Ru/ZrO₂@C catalyst, Ru (probable single-atom) was highly dispersed on nanotetragonal ZrO₂ (3.3 nm), embedded in the amorphous carbon, and no apparent Ru nanoclusters were observed even after reactions. TPR results indicated that this excellent stability might be attributed to strong metal–support interaction between Ru and nanotetragonal ZrO₂.

This work was supported by the National Natural Science Foundation of China the Strategic Priority Research Program of the Chinese Academy of Sciences and the National Key Projects for Fundamental Research and Development of China. Dr W. Cao is also grateful to financial support from the Scientific Research Program of the Shaanxi Provincial Education Department and the Doctoral Program of Shaanxi University of Technology.