Effect of isomorphic substitution of zirconium on mesoporous silica as support for cobalt Fischer–Tropsch synthesis catalysts

Isomorphically Zr-substituted mesoporous SBA-15 with Zr/Si atomic ratios of 1/100, 1/50, 1/20, 1/8 and 1/3 have been successfully synthesized. It was demonstrated that the Zr4+ ions were introduced into the framework of SBA-15 with the hexagonal array of uniform tubular channel configuration intact up to a Zr/Si ratio of 1/20. Another sample of zirconium, impregnated SBA-15 to incipient wetness with a Zr/Si ratio of 1/20 was prepared for comparison. These mesoporous materials were loaded with 10 wt.% cobalt by incipient wetness impregnation and characterized by XRD, TEM, N2 absorption–desorption, UV–visible, H2-TPR, H2-TPD, O2 titration, and NH3-TPD as well as XPS. It was shown that the introduction of zirconium produced weak acidic sites, changed the interaction between the cobalt species and the support, and improved the cobalt reducibility. The performance of catalysts for Fischer–Tropsch synthesis was tested in a fixed bed reactor, the cobalt catalyst supported on the isomorphically Zr-substituted mesoporous SBA-15 with a Zr/Si ratio of 1/20 showed the best performance.

For catalysts with Zr/Si atomic ratio lower than 1/20, the cobalt species were primarily in the form of spinel Co3O4 (peak #) on the catalysts. When the Zr/Si atomic ratio is higher than 1/20, the characteristic peaks (peak α) belonging to the tetragonal ZrO2 phase are observed.Figure optionsDownload high-quality image (45 K)Download as PowerPoint slide