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

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 GaxZr1–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.