Keywords: Ion exchange / Composite oxides / Microporous materials / Zirconium / Tungsten MO x -ZrO 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 4 ) 2 ·4H 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 2 g -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 2 g -1 IntroductionZirconium oxide [1,2] and its composite oxides [3][4][5] have been employed as catalysts and supports because of their redox, acid/base, and thermal stabilities. For example, WO x -ZrO 2 and MoO x -ZrO 2 are typical solid acid catalysts with activity in the isomerization of n-alkanes, [3] alkylation of phenols, [4] and esterification.[5] The preparation of ZrO 2 -based oxides with high surface areas has thus been widely studied. Porous ZrO 2 , [6][7][8] Zr-Cr oxide (374 m 2 g -1 ), [9] ZrO 2 -MoO 3 (275 m 2 g -1 ), [10] ZrO 2 -WO 3 (228 m 2 g -1 ), [10] ZrO 2 -WO 3 (305 m 2 g -1 ), [11] VO x -ZrO 2 (340 m 2 g -1 ), [12] and MnO 2 -ZrO 2 (256 m 2 g -1 ) [13] have been reported. However, their preparation methods were specialized for the respective materials, and no versatile method has been suggested. Therefore, ZrO 2 -based oxides of 100 m 2 g -1 or lower have been used repeatedly as catalysts by others. [14][15][16] The present group has reported the wall ion-exchange (WIE) method [17][18][19][20] as a novel preparation method of hexagonally mesostructured materials, some of which gave porous oxides with hexagonal arrays of micropores and high surface areas after calcination.[ 4970and pore sizes of approximately 1.2 nm, whereas treatments at pH = 2.5-4.8 gave surface areas of 3-18 m 2 g -1 . The predominant oxyanion in the former region was a monomeric ion, WO 4 2-. The WIE-calcination method was thus applied to the preparation of Cr-, Mo-, or V-containing ZrO 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 2 g -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 2 -based oxides.(CTAB), [21] abbreviated as ZS in this study, is a starting material of the WIE treatment, and has the composition Zr(HSO 4 )(C 19 H 42 N) 0.61 (OH) 3.57 ·2H 2 O with ordered hexagonal arrays of surfactant micelles as shown in Figure 1. The hydrogen sulfate anions (HSO 4 -) in the ZS wall can be exchanged readily for oxyanions of phosphorus, [17,20] arsenic, [18] and seleniu...
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