Cobalt-containing mesoporous silicas—Preparation, characterization and catalytic activity in toluene hydrogenation

The effect of post synthesis modification was studied on cobalt impregnated mesoporous materials having different textural properties. The supports were SBA-15 and MCM-41 with conventional and spherical morphology. The modified materials were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed reduction (TPR), FT-IR spectroscopy of adsorbed probe molecules (pyridine and CO) and toluene hydrogenation as a catalytic test reaction. It was found that the amount of surface silanol groups of the mesoporous supports and the variation of the pretreatment procedure have a notable influence on the nature of the cobalt oxide species formed upon the precursor decomposition. Formation of Co3O4, CoO and Co2+ species in different ratio, depending on the mesoporous support, was established. The strength of interaction with the support determines the dispersion, reducibility and the catalytic activity in toluene hydrogenation.

Cobalt impregnated mesoporous silica materials, MCM-41 with conventional and spherical morphology and SBA-15, were synthesized with hydrothermal and sol–gel methods. It was found that the cobalt–support interaction depends mainly on the presence of accessible terminal SiOH groups in the pore wall of the support. Mild oxidative salt decomposition had favorable effect on the reducibility of the cobalt oxide species. In case of spherical MCM-41 and SBA-15 materials the strong metal–support interaction resulted in low reducibility, hindering the formation of metallic cobalt active in toluene hydrogenation.Figure optionsDownload as PowerPoint slide