Hydrogen storage into monobenzyltoluene over Ru catalyst supported on SiO2-ZrO2 mixed oxides with different Si/Zr ratios

Abstract

Supported Ru catalysts have been often employed for hydrogen charge into liquid organic hydrogen carrier molecules (monobenzyltoluene in this work), and their catalytic performance largely depends upon physicochemical properties of the support materials. We prepared supported Ru catalysts on SiO2-ZrO2 with different Si/(Si+Zr) ratios ranging from 0 to 30mol% by loading Ru3(CO)12 onto Si,Zr-mixed metal hydroxide and subsequent thermolysis. The textural properties, Ru particle size, and hydrogenation activity of Ru/SiO2-ZrO2 catalysts show a volcano-shaped dependence on the content of Si added, where the maximum is achieved at the Si/(Si+Zr) ratio of 5 mol%. Up to this Si content the incorporation of Si into ZrO2 improves thermal stability and decreases the particle size of tetragonal ZrO2, resulting in a positive contribution to hydrogen storage efficiency. However, the further addition of Si increases surface heterogeneity and charge imbalance, and hence induces a decrease in the density of surface OH group reacting with Ru3(CO)12, which explains the lowered activity. Therefore, the addition of up to 5 mol% Si into ZrO2 is effective in enhancing the hydrogenation performance of Ru/ZrO2 owing to the improved textural properties and smaller Ru particles.