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 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.