Synthesis of Ordered Mesoporous Zr-Al Composite Oxides with Excellent Structural and Textural Properties and Extremely High Stability

Abstract

Ordered mesoporous Zr-Al composite oxide materials (denoted as OMZA-x) with different Zr contents have been synthesized by a solvent evaporation-inducing self-assembly procedure associated with a thermal treatment at 100 °C. A cooperative co-assembly process of amphiphilic triblock copolymer F127 molecules and inorganic hydroxyl species originated from the hydrolysis of Zr and Al precursors was proposed to explain the synthesis of OMZA-x. Compared to ordered mesoporous alumina prepared without introducing Zr species, the resultant OMZA-x exhibited a much more ordered mesostructure combined with a distinct increase in the pore volume and specific surface area. The highly homogenous doping of Zr into the mesopore walls together with the formation of Zr-O-Al bonds can effectively enhance the thermal and hydrothermal stability of OMZA-x. For instance, the ordered mesostructure and excellent textural properties of OMZA-6 prepared with the optimum atomic ratio of Al to Zr of 6 could be well maintained even after a high-temperature treatment at 1000 °C for 1 h or a hydrothermal treatment at 100 °C for 6 h.

Keywords: Zr-Al composite oxide; cooperative co-assembly; hydrothermal stability; mesoporous materials; thermal stability.

Figure 1

Schematic illustration for the synthesis of ordered mesoporous Zr-Al composite oxide materials (OMZA-x).

Figure 2

Small-angle X-ray diffraction (XRD) patterns of samples OMZA-x and OMA.

Figure 3

Transmission electron microscopy (TEM) images of sample OMZA-6 viewed along the (110) (a) and (100) (b) directions, TEM image (c) of OMZA-6 thermally treated at 1000 °C for 1 h, and TEM image (d) of OMZA-6 hydrothermally treated at 100 °C for 6 h, respectively.

Figure 4

Elemental analysis mapping showing the distribution of Al (a,d), O (b,e), and Zr (c,f) for two different regions of the sample OMZA-6.

Figure 5

N₂ sorption isotherms (a) and pore size distribution curves (b) of samples OMZA-x and OMA. For clarity, in (a), the isotherms of OMZA-4, OMZA-6, OMZA-8, OMZA-10 and OMA are offset along the Y axis by 150, 300, 560, 750, and 950 cm³/g, respectively. In (b), the Y axis values are increased by 3.0, 6.0, 10.2, 13.8, and 17.8 cm³/g, respectively.

Figure 6

FT-IR spectra of samples OMZA-6 and OMA.

Figure 7

²⁷Al MAS NMR spectra of samples OMZA-6 and OMA.

Figure 8

Small- (a) and wide- (b) angle XRD patterns of samples OMZA-x and OMA after thermal treatment at 1000 °C for 1 h.

Figure 9

N₂ sorption isotherms (a) and pore size distribution curves (b) of samples OMZA-x and OMA after thermal treatment at 1000 °C for 1 h. For clarity, in (a), the isotherms of OMZA-4, OMZA-6, OMZA-8, OMZA-10 and OMA are offset along the Y axis by 160, 370, 560, 710 and 950 cm³/g, respectively. In (b), the Y axis values are increased by 2, 4.2, 7.5, 10.8 and 13.8 cm³/g, respectively.

Figure 10

Small-angle XRD patterns of OMZA-6 (a) and OMA (b) before and after hydrothermal treatment at 100 °C for different time.

Figure 11

N₂ sorption isotherms (a) and pore size distribution curves (b) of sample OMZA-6 before and after hydrothermal treatment at 100 °C for different time. For clarity, in (a), the isotherms of untreated OMZA-6 and OMZA-6 hydrothermally treated for 2 h are offset along the Y axis by 200 and 100 cm³/g, respectively. In (b), the Y axis values are increased by 3.1 and 1.5 cm³/g, respectively.