Effects of SiO$_{2}$-doping on high-surface-area Ru/TiO$_{2}$ catalysts for the selective CO methanation

Aiming at a better understanding of the role of electronic / chemical modifications of the support on the performance of high specific surface area Ru/TiO$_{2}$ catalysts in the selective CO methanation, we prepared and examined four different Ru/TiO$_{2}$ catalysts with similar Ru loading and similar high specific surface area, but with the support doped with different amounts of Si (0–12 wt.% SiO$_{2}$). Their activity for methane formation exhibits a volcano-shaped dependence on the SiO$_{2}$ content, with a maximum between 4 and 8 wt.%. The CO adsorption properties showed distinct differences, with the weakest CO adsorption strength for the most active catalysts. Based on the results of a variety of different characterization techniques and pyrrole/pyridine adsorption measurements, the higher activity / lower CO adsorption strength cannot be explained by a single property, such as particle size, but must rather be caused by a complex combination of different effects