Synthesis of Mesoporous Zr-P-Al Materials with High BET Specific Surface Area without Calcination

Abstract

A mesostructured zirconium oxide was synthesized hydrothermally using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent and ZrSO4. 4H2O as the reactant. Subsequent post-synthetic treatment with H3PO4 followed by the treatment with AlCl3 solutions resulted in mesoporous Zr-P-Al materials, which exhibited high BET specific surface area before calcination. The phosphoric acid concentrationaffected the textual data of the resulting Zr-P and Zr-P-Al materials greatly. 0.1-0.5 M H3PO4 increased obviously the long-range order of the as-synthesized Zr-P materials while 0.76 M H3PO4 decreased it. After calcination at 773 K, the Zr-P materials turned to nonporous materials except the one synthesized by 0.5 M H3PO4, which showed micropores with a BET specific surface area of 147 m2/g. Further treating the Zr-P materials (synthesized from different concentration of phosphoric acid) with the same amount of AlCl3 solution resulted in mesoporous Zr-P-Al materials, but the long-range order of which decreased when the H3PO4 concentration increased. Similarly, the BET specific surface area of the above-mentioned Zr-P-Al materials decreased from 462 m2/g for 0.25 M H3PO4 to 394 m2/g for 0.5 M H3PO4 and finally to 332 m2/g for 0.76 M H3PO4 after calcination at 773 K, while the pore size increased gradually from 3.0 to 3.5 nm. It was found that about 90% of the CTAB had been removed during the AlCl3 treatment and that the as-synthesized Zr-P-Al materials exhibited high BET specific surface area as well as mesopores. The AlCl3 amount is another factor affecting the textual data of the uncalcined Zr-P-Al materials besides the H3PO4 concentration. With the phosphoric acid concentration of 0.25 M, the BET specific surface area of the as-synthesized Zr-P-Al materials increased from 477 m2/g to as high as 734 m2/g with the increasing AlCl3 amount before it decreased from then on.