Ga Ion-doped ZrO₂ Catalyst Characterized by XRD, XAFS, and 2-Butanol Decomposition

Abstract

Group 2, 3, and 13 element-doped zirconium oxide catalysts M-ZrO₂ (M = Mg, Sr, Y, La, Ce, Sm, Er, Yb, B, Al, Ga, In, and Tl; 5 mol%) were prepared by impregnation of each metal salt aqueous solution on amorphous zirconium hydroxide, followed by calcination at 773 K. The M-ZrO₂ samples were characterized by the catalytic performance of 2-butanol decomposition at 573 K, XRD, XANES and EXAFS spectroscopic techniques. Detailed analyses were performed herein for a series of Ga–ZrO₂ with various doping amounts in the range of 1 – 60 mol%. The addition of Group 2 and 3 elements little influenced the catalytic performance of ZrO₂ itself to promote dehydration to produce 1-butene with 90% selectivity. Ga–ZrO₂ and In–ZrO₂ gave methyl ethyl ketone as the main product via dehydrogenation. The doped Ga ion mainly existed inside the bulk of zirconia by forming the Ga_xZr_1–xO₂ solid solution up to 5 mol%. Highly doped species more than 10 mol% aggregated to form ε-Ga₂O₃. Each fraction forming the solid solution and Ga₂O₃-like species was evaluated by XANES analysis.