Evolution of the structure of Co stevensite during its treatment in the air, inert gas flow and flowing hydrogen

Synthetic TOT (2 tetrahedron layers, 1 octahedron layer) trioctahedral hydr osilicates (stevensites) of Zn, Mg, Co and Co-Zn were prepared by the depos ition-precipitation technique. The evolution of both the structure and spec tral properties of the silicates were studied during their treatment in var ious media. The position of the nu (OH) absorption band and the temperature of crystallization of the anhydrous silicate were found to be useful indic ators of the cationic composition of stevensites. The data obtained are use d to analyze and to review the earlier data on Co/SiO2 catalysts. It is con cluded that the formation of Co stevensite occurs in the majority of cases when the pH of the maternal solution during the preparation of a catalyst i s above four.