Zirconium oxides dispersed on silica derived from Cp(2)ZrCl(2), [(i-PrCp)(2)ZrH(mu-H)](2), and Zr(OEt)(4) characterized by X-ray absorption fine structure and catalytic ketonization of acetic acid

Newly dispersed Zr oxides on SiO2 were prepared from Cp(2)ZrCl(2), [(i-PrCp)(2)ZrH(mu-H)](2), and Zr(OEt)(4) precursors and were characterized by X-ray absorption fine structure (XAFS) and catalytic ketonization of acetic acid. ZrCp(2)Cl(2) and [(i-PrCp)(2)Zr(mu-H)](2) precursors yielded monomeric Zr oxides with unsaturated coordination in low loadings, whereas Zr(OEt)(4) yielded Zr-oxide assemblies in octahedral symmetry independent of Zr loading up to 15 wt% Zr. The former catalysts were more active than the latter catalyst for ketonization of acetic acid. The catalytic ketonization was suggested to proceed via bidentate acetates adsorbed on neighboring Zr sites. (C) 1996 Academic Press, Inc.