Reducibility of cobalt species impregnated on NaY and HY zeolites

Reducibility of 6 wt.% cobalt impregnated on zeolite Y in sodium and proton form (6Co/NaY and 6Co/HY, respectively) was studied mainly by X-ray absorption spectroscopy including X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure (EXAFS) along with other techniques such as X-ray diffraction. The results indicated that the physicochemical properties of Co strongly depended on the form of support. After calcination in air, Co2+ species were observed on both NaY and HY. After reduction in H2 at 420 °C for 5 h, the Co species in 6Co/NaY were partially reduced to metallic form and each Co was surrounded by other six Co atoms. On the other hand, Co species in 6Co/HY was not reducible under a similar condition and each Co was surrounded by four oxygen atoms. Because the metallic cobalt is the active form for butane hydrogenolysis, 6Co/NaY was more active than 6Co/HY at 400 °C giving average conversion of 32% and 2%, respectively.