Effect of pH value of silica on reducibility of CO/SiO2 catalyst

A new method was proposed to modify commercial silica for preparation of a series of supported Co/SiO2 catalyst to get more reducibility. The temperature-programmed reduction and the extended X-ray absorption fine structure were used to investigate the structure and reducibility of the catalyst samples. The results indicated that the cobalt species of calcined samples exist in Co3O4 state, and its reduction is a two-step process Co3O4-->CoO-->Co. CoO tends to react with the surface silicon to form some cobalt species which are difficult to be reduced, leading to the decrease of the reducibility of Co3O4. The FT-IR result of the silica at 673 K and 1.3 mPa indicated that the higher pH value of the support leads to more surface silicon at higher temperature, and the more surface silicon may result in further reaction between CoO and silica. The reduction mechanism of Co/SiO2 catalyst was speculated, and it was used to interpret the effect of other conditions on the formation of Co2SiO4.