Surface Modification of SiO₂ for Highly Dispersed Pd/SiO₂ Catalyst.

Surface modification of SiO₂ supports was shown to significantly affect the properties of Pd/SiO₂ catalysts. The surface of SiO₂ can be modified by various pretreatment methods. In this study, the effect of different calcination temperatures on support surface was investigated. Pd supported on pretreated SiO₂ was characterized by H2 temperature-programmed reduction (TPR), XRD, CO chemisorption measurements, and field-emission transmission electron microscopy (FE-TEM). The silanol group (-OH), which is one of the functional groups of SiO₂, interferes with the reduction of palladium because it strongly bonds with palladium ions (-PdO) during the preparation of the catalyst. Due to the complete removal of silanol (Si-OH) groups following calcination at 700 °C, the metal reducibility was enhanced, and the catalyst pretreated at this calcination temperature exhibited the highest metal dispersion of 13.02%. Further, to confirm the catalytic activity of the prepared catalysts, hydrogenation of D-glucose was conducted. The HPLC results demonstrated that Pd/SiO₂_700 has the highest catalytic activity toward hydrogenation of D-glucose. Therefore, it was confirmed that the removal of silanol groups increase the metal dispersion and catalytic activity of Pd/SiO₂ catalyst.