Preparation of Porous ZrO sub(2)-Based Composite Oxides Containing W, Cr, Mo, or V Through a Wall Ion-Exchange Method

MO sub(x)-ZrO sub(2) (M = W, Cr, Mo, or V) composite oxides with high surface areas and hexagonal pore structures were prepared through a wall ion-exchange (WIE)-calcination method. A composite (ZS) of Zr(SO sub(4)) sub(2).4H sub(2)O and cetyltrimethylammonium bromide with ordered hexagonal structure was cast into solutions of M oxyanions. The efficiency of the WIE treatment was first studied on the solutions of tungsten oxyanion in detail. The surface areas of tungsten-oxyanion-introduced ZSs (W-ZSs) after calcination at 673 K in air for 2 h were 3-248 m super(2)g super(-1) depending on the pH values of the exchange solutions. The treatments at pH = 5.6-10.1 resulted in the formation of porous materials with surface areas of 38-248 m super(2)g super(-1) and pore sizes of approximately 1.2 nm, whereas treatments at pH = 2.5-4.8 gave surface areas of 3-18 m super(2)g super(-1). The predominant oxyanion in the former region was a monomeric ion, WO sub(4) super(2-). The WIE-calcination method was thus applied to the preparation of Cr-, Mo-, or V-containing ZrO sub(2) composite oxides in which the respective monomeric oxyanions were employed as the exchange ions by adjusting the pH values of the solutions. The surface areas of calcined Cr-, Mo-, and V-ZS were 348, 251, and 229 m super(2)g super(-1), respectively, and pore sizes were 1.00-1.12 nm. The WIE-calcination method was proved to be a general method for the preparation of porous ZrO sub(2)-based oxides. HSO sub(4) super(-) anions in a parent mesostructured material were ion-exchanged with monomeric oxyanions of W, Cr, Mo, and V in aqueous solutions. The resulting materials gave porous composite oxides with surface areas of 229-348 m super(2)g super(-1) and pore diameters of 1.0-1.3 nm upon calcination.