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Synthesis of ordered mesoporous alumina with high thermal stability using aluminum nitrate as precursor
Materials Letters 135 (2014) 35–38
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis of ordered mesoporous alumina with high thermal stability using aluminum nitrate as precursor Xu Wang, Dahai Pan n, Qian Xu, Min He, Shuwei Chen, Feng Yu, Ruifeng Li n College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, P R China
art ic l e i nf o
a b s t r a c t
Article history: Received 14 April 2014 Accepted 19 July 2014 Available online 31 July 2014
By using the inexpensive aluminum nitrate as precursor, a highly ordered mesoporous alumina with high thermal stability has been synthesized successfully via an evaporation-induced self-assembly pathway associated with solvothermal pre-hydrolysis process. The resultant mesoporous alumina maintains the ordered hexagonal mesostructure, narrow pore-size distribution, high BET surface area and large pore volume even after thermal treatment at 900 1C. & 2014 Elsevier B.V. All rights reserved.
Keywords: Porous materials Thermal properties Mesoporous structure Evaporation-induced self-assembly
1. Introduction Ordered mesoporous alumina (MA) materials with tunable structures, high surface areas and large pore volumes have potential applications as catalysts or catalyst supports [1]. A series of ordered MAs have been successfully synthesized through the sol–gel process [2] or by utilizing the nano-casting method [3]. Among these processes, the evaporation-induced self-assembly (EISA) pathway [2] has been demonstrated to be a simple and fast way to get ordered and thermally stable MA, however, the producing cost is an important concern because of the use of expensive and toxic aluminum alkoxides. Although considerable efforts have been devoted to reduce the cost of MA synthesis recently by using the inexpensive inorganic aluminum salts to replace aluminum alkoxides [1,4], unfortunately disordered mesostructures with poor thermal stability were fabricated in most cases. Therefore, there are still great interests in developing a novel, economic and environmentally benign approach to prepare highly ordered and thermally stable MA. Herein, we present a feasible approach to synthesize ordered MA with high thermal stability by using the inexpensive aluminum nitrate as precursor. To favor the formation of ordered mesostructure, the key is to maximize the concentration of Al–OH species from the hydrolysis of aluminum nitrate to enhance their hydrogen bonding interaction with the surfactant molecules [5], which can be achieved by the solvothermal pre-hydrolysis (STPH) process. With this strategy, the ordered MA with 2D hexagonal mesostructure can be readily obtained. More importantly, the n
Corresponding authors. Fax: þ 86 0351 6010121. E-mail addresses: [email protected] (D. Pan), rfl[email protected] (R. Li).
http://dx.doi.org/10.1016/j.matlet.2014.07.133 0167-577X/& 2014 Elsevier B.V. All rights reserved.
synthesized MA exhibits a high thermal stability up to 900 1C, and possesses narrow pore-size distribution, high surface area and large pore volume.
2. Experimental section Synthesis procedure: In a typical synthesis, 5.63 g of Al (NO3)3 9H2O was dissolved in 15 mL of mixed solution of anhydrous ethanol and deionized water (VEtOH/Vwater ¼4/1). Then, the mixture was transferred to a beaker without cover for the STPH treatment at 80 1C for 5 h to promote the hydrolysis of Al3 þ into Al–OH species. After that, the obtained light-orange alumina xerogel with a large number of Al–OH species was taken out and slowly added to 30 mL of anhydrous ethanol solution dissolved 1.8 g of P123 (EO20PO70EO20, EO ¼ethylene oxide, PO ¼propylene oxide) and 0.6 g of citric acid (CA). After being vigorously stirred for 24 h at 30 1C, the resultant mixture was transferred to a dish and underwent solvent evaporation at 45 1C for 48 h and thermal treatment at 100 1C for 24 h, respectively. The final product was calcined at 400 1C for 5 h to remove the template and almost all of CA. The other MAs were prepared analogously by using AlCl3 6H2O and Al2(SO4)3 18H2O as precursors, respectively. The obtained samples were named as SE–Al(n), SE–Al(c), and SE–Al(s) (n, c, and s refer to Al(NO3)3 9H2O, AlCl3 6H2O, and Al2(SO4)3 18H2O, respectively). For comparison, the MA prepared by the similar EISA method without the STPH process using Al (NO3)3 9H2O as precursor was named E–Al(n). Notably, the amount of aluminum precursor used in each case was 15 mmol, and the solvent could be recycled and reused during the synthetic process by using the home-made drying oven.
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X. Wang et al. / Materials Letters 135 (2014) 35–38
Thermal stability evaluation: The thermal stability was investigated by treating calcined samples in air at 750 and 900 1C for 1 h. Both temperature thermal treatment processes were correspondingly abbreviated as LT and HT. Characterization: Powder X-ray diffraction patterns were recorded on a Shimadzu XRD-6000 diffractometer using Ni-filtered Cu Kα (0.154 nm) radiation. Transmission electron microscopy (TEM) experiments were performed on a JEOL 2011 microscope operated at 200 kV. N2 adsorption was conducted on a Quantachrome analyzer at 196 1C. Before measurements, the samples were degassed at 180 1C in vacuum for 10 h. The BET method was used to calculate the specific surface areas. The poresize distributions were derived from the adsorption branches of the isotherms using the BJH method. The total pore volumes were calculated from the amount of nitrogen adsorbed at a relative pressure of 0.99.
3. Results and discussion Fig. 1 depicts the XRD patterns of MAs prepared with different inorganic aluminum salts as precursors before and after the hightemperature treatment. It shows that SE–Al(n) exhibits two wellresolved Bragg peaks (Fig. 1A), according to the TEM observation of the well-ordered hexagonal arrays along [110] and [100]
orientations with uniform pore size and wall thickness (Fig. 2A), which can be attributed to p6mm hexagonal symmetry. From the intense (100) peak, a d100 spacing of 9.81 nm is calculated (Table 1), corresponding to a unit cell parameter of 11.3 nm. However, for E–Al(n) prepared without the STPH process, only a broad (100) peak is observed (Fig. 1A), indicating that the STPH plays a key role to synthesize highly ordered mesostructure when Al(NO3)3 9H2O is used as precursor. We assume that the STPH is advantageous for the endothermic hydrolysis reaction of inorganic aluminum salts and thus facilitates the transformation of Al3 þ into Al–OH species. With increasing the concentration of Al–OH species, the hydrogen bonding interaction between P123 and aluminum species will be significantly enhanced, which will promote the cooperative assembly process and further construct an ordered mesostructure of final SE–Al(n). In addition, CA can behave as a ligand and bond with Al–OH species in a bidentate or bridging fashion, which can effectively slow down the condensation reaction of Al–OH species and maintain more Al–OH species to enhance their hydrogen bonding interaction with P123. On the other hand, compared with the XRD pattern of SE–Al(n), SE–Al(c) and SE–Al(s) exhibit relatively lower signal-to-noise ratio in their XRD patterns and broader full width at half-maximum (FWHM) as judged from the (100) peak, suggesting a less mesostructural ordering (Fig. 1A), which confirms the radius and charge of the counteranions will impose a great effect on the assembly
Fig. 1. XRD patterns of calcined (A) and high temperature treated (B) samples.
Fig. 2. TEM images of SE–Al(n) (A), SE–Al(n)–LT (B), and SE–Al–HT (C) (the inset in B is corresponding SAED pattern).
X. Wang et al. / Materials Letters 135 (2014) 35–38
process of the alumina-surfactant mesophase [2]. For NO3 , Cl , and SO24 , the Pauling radiuses are 1.79, 1.81, and 2.30 Å, respectively. NO3 scarcely influences the assembly process due to its small ionic radius and weak complexation ability. However, Cl can strongly coordinate with aluminum ions and thus destroy the organic–inorganic interfacial balance, which would disturb the assembly process. Moreover, for SO24 , the larger ionic radius and stronger hydration ability than those of Cl and NO3 will further disturb the hydrogen bonding interaction between P123 and Al–OH species, leading to a more disordered mesostructure. The N2 adsorption–desorption results show that despite SE–Al (n) and E–Al(n) both exhibit the typical type IV isotherm; compared with E–Al(n), SE–Al(n) shows a steeper capillary condensation step occurring at a relative pressure (P/P0) ranging from 0.40 to 0.60 (Fig. 3A), corresponding to a narrower pore size distribution (Fig. 3B), which further indicates that the STPH can remarkably increase the mesoporous uniformity of MA (Figs. 1 and 2A). For SE–Al(n), the surface area and pore volume are 401 m2/g and 0.47 cm3/g, respectively (Table 1), which are higher than those of samples prepared by the traditional EISA method with the aluminum nitrate as precursor [1,2]. From the small-angle XRD patterns of samples treated at high temperature (Fig. 1B), it can be seen that for E–Al(n)–LT thermally treated at 750 1C, only a very weak diffraction peak is observed, indicating that its mesostructure has been seriously destroyed. And concomitantly in its wide-angle XRD pattern (the inset in Fig. 1B), seven weak diffraction peaks are observed at 2θ ¼19.8, 32.6, 36.9, 39.6, 45.6, 61.5, and 67.21, which can be indexed as the (111), (220), (311), (222), (400), (511), and (440) reflections of γ-alumina (JCPDS card 10-0425), indicating that the amorphous Table 1 The structure parameters of samples before and after high-temperature thermal treatment. Samples
d100 (nm)
P (nm)
S (m2/g)
V (cm3/g)
E–Al(n) SE–Al(n) SE–Al(n)–LT SE–Al(n)–HT
7.24 9.81 6.31 5.97
4.5 4.5 3.7 3.4
175 401 255 247
0.29 0.47 0.29 0.24
Note: d100 is the d-spacing calculated from the first peak, p is the pore size calculated from the adsorption branch using the BJH method, S is BET surface area and V is the total pore volume.
37
Al species in E–Al(n)–LT mesoporous walls are converted to
γ-alumina. In contrast, SE–Al(n)–LT still displays a very strong
(100) peak after the same thermal treatment, indicating that the ordered mesosturcutre is well maintained. TEM image also confirms that SE–Al(n)–LT possesses ordered hexagonal mesostructure (Fig. 2B). Moreover, the selective area electron diffraction (SAED) pattern (the inset in Fig. 2B) of the ordered mesostructure domains of SE–Al(n)–LT indicates the mesoporous walls are still amorphous phase, which confirms that the remarkably increased mesostructural ordering can prevent Al atomic diffusion and sinter at high temperature, and further suppress the formation of crystalline alumina. However, with further increasing thermal treatment temperature to 900 1C, for SE–Al(n)–HT, the relative intensity of (100) peak decreases obviously, demonstrating that the mesostructural ordering has been decreased seriously due to the formation of γ-alumina during the higher temperature thermal treatment process (Fig. 1B). Noteworthy, from the TEM image of SE–Al(n)–HT (Fig. 2C), the ordered hexagonal arrays along [100] orientation with uniform pore size could still be observed, indicating that the ordered mesostructure of SE–Al(n) has not been completely destroyed even after thermal treatment at 900 1C. The extremely high thermal stability of SE–Al(n) is also validated by the N2 adsorption–desorption measurements. For SE–Al(n)–LT and SE–Al(n)–HT, their N2 adsorption–desorption curves still maintain the typical IV isotherm with a H1-type hysteresis loop (Fig. 3A), and the pore size distribution curves (Fig. 3B) are still quite narrow, indicating that the hexagonal mesostructures are well-preserved (Figs. 1A, 2B and C). From Table 1, it can be seen that even after thermal treatment at 900 1C, SE–Al(n)– HT retained 61.6% of the specific surface area and 51.1% of the pore volume compared with the untreated SE–Al(n).
4. Conclusion By using the inexpensive aluminum nitrate as precursor, highly ordered MA with high surface area has been successfully synthesized via an EISA pathway associated with STPH process. The obtained SE–Al(n) displays extremely high thermal stability. The ordered mesostructure can be well preserved even after thermal treatment at 900 1C. Our achievements provide a facile route for low-cost mass production of MA with promising properties for designed catalytic applications in the petroleum industry.
Fig. 3. N2 sorption isotherms (A) and the corresponding pore size distribution curves (B) of samples. For clarity, the isotherms (A) of SE–Al(n), SE–Al(n)–LT, and SE–Al(n)–HT are offset along the Y axis by 20, 200, and 300 cm3/g, respectively, and the corresponding pore size distributions curves (B) are offset by 1, 4.5, and 6.4 cm3/g, respectively.
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X. Wang et al. / Materials Letters 135 (2014) 35–38
Acknowledgment
References
This work was financially supported by the National Natural Science Foundation of China (51172154), the China Postdoctoral Science Foundation (2012M510783), the Shanxi Province Science Foundation for Youths (2012021006-2 and 2013021008-3), and the Science and Technology Project of Shanxi Province (20130313001-3).
[1] Cai WQ, Yu JG, Anand C, Vinu A, Jaroniec M. Chem Mater 2011;23:1147–57. [2] Yuan Q, Yin AX, Luo C, Sun LD, Zhang YW, Duan WT, et al. J Am Chem Soc 2008;130:3465–72. [3] Wu ZX, Li QA, Peng D, Webley PA, Zhao DYJ. Am Chem Soc 2010;132:12042–50. [4] Shang XF, Wang XG, Nie WX, Guo XF, Zou XJ, Ding WZ, et al. J Mater Chem 2012;22:23806–14. [5] Wang XY, Pan DH, Guo M, He M, Niu PY, Li RF. Mater Lett 2013;97:27–30.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.07.133.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Synthesis of ordered mesoporous alumina with high thermal stability using aluminum nitrate as precursor Xu Wang, Dahai Pan n, Qian Xu, Min He, Shuwei Chen, Feng Yu, Ruifeng Li n College of Chemistry and Chemical Engineering, Taiyuan University of Technology, Taiyuan 030024, P R China
art ic l e i nf o
a b s t r a c t
Article history: Received 14 April 2014 Accepted 19 July 2014 Available online 31 July 2014
By using the inexpensive aluminum nitrate as precursor, a highly ordered mesoporous alumina with high thermal stability has been synthesized successfully via an evaporation-induced self-assembly pathway associated with solvothermal pre-hydrolysis process. The resultant mesoporous alumina maintains the ordered hexagonal mesostructure, narrow pore-size distribution, high BET surface area and large pore volume even after thermal treatment at 900 1C. & 2014 Elsevier B.V. All rights reserved.
Keywords: Porous materials Thermal properties Mesoporous structure Evaporation-induced self-assembly
1. Introduction Ordered mesoporous alumina (MA) materials with tunable structures, high surface areas and large pore volumes have potential applications as catalysts or catalyst supports [1]. A series of ordered MAs have been successfully synthesized through the sol–gel process [2] or by utilizing the nano-casting method [3]. Among these processes, the evaporation-induced self-assembly (EISA) pathway [2] has been demonstrated to be a simple and fast way to get ordered and thermally stable MA, however, the producing cost is an important concern because of the use of expensive and toxic aluminum alkoxides. Although considerable efforts have been devoted to reduce the cost of MA synthesis recently by using the inexpensive inorganic aluminum salts to replace aluminum alkoxides [1,4], unfortunately disordered mesostructures with poor thermal stability were fabricated in most cases. Therefore, there are still great interests in developing a novel, economic and environmentally benign approach to prepare highly ordered and thermally stable MA. Herein, we present a feasible approach to synthesize ordered MA with high thermal stability by using the inexpensive aluminum nitrate as precursor. To favor the formation of ordered mesostructure, the key is to maximize the concentration of Al–OH species from the hydrolysis of aluminum nitrate to enhance their hydrogen bonding interaction with the surfactant molecules [5], which can be achieved by the solvothermal pre-hydrolysis (STPH) process. With this strategy, the ordered MA with 2D hexagonal mesostructure can be readily obtained. More importantly, the n
Corresponding authors. Fax: þ 86 0351 6010121. E-mail addresses: [email protected] (D. Pan), rfl[email protected] (R. Li).
http://dx.doi.org/10.1016/j.matlet.2014.07.133 0167-577X/& 2014 Elsevier B.V. All rights reserved.
synthesized MA exhibits a high thermal stability up to 900 1C, and possesses narrow pore-size distribution, high surface area and large pore volume.
2. Experimental section Synthesis procedure: In a typical synthesis, 5.63 g of Al (NO3)3 9H2O was dissolved in 15 mL of mixed solution of anhydrous ethanol and deionized water (VEtOH/Vwater ¼4/1). Then, the mixture was transferred to a beaker without cover for the STPH treatment at 80 1C for 5 h to promote the hydrolysis of Al3 þ into Al–OH species. After that, the obtained light-orange alumina xerogel with a large number of Al–OH species was taken out and slowly added to 30 mL of anhydrous ethanol solution dissolved 1.8 g of P123 (EO20PO70EO20, EO ¼ethylene oxide, PO ¼propylene oxide) and 0.6 g of citric acid (CA). After being vigorously stirred for 24 h at 30 1C, the resultant mixture was transferred to a dish and underwent solvent evaporation at 45 1C for 48 h and thermal treatment at 100 1C for 24 h, respectively. The final product was calcined at 400 1C for 5 h to remove the template and almost all of CA. The other MAs were prepared analogously by using AlCl3 6H2O and Al2(SO4)3 18H2O as precursors, respectively. The obtained samples were named as SE–Al(n), SE–Al(c), and SE–Al(s) (n, c, and s refer to Al(NO3)3 9H2O, AlCl3 6H2O, and Al2(SO4)3 18H2O, respectively). For comparison, the MA prepared by the similar EISA method without the STPH process using Al (NO3)3 9H2O as precursor was named E–Al(n). Notably, the amount of aluminum precursor used in each case was 15 mmol, and the solvent could be recycled and reused during the synthetic process by using the home-made drying oven.
36
X. Wang et al. / Materials Letters 135 (2014) 35–38
Thermal stability evaluation: The thermal stability was investigated by treating calcined samples in air at 750 and 900 1C for 1 h. Both temperature thermal treatment processes were correspondingly abbreviated as LT and HT. Characterization: Powder X-ray diffraction patterns were recorded on a Shimadzu XRD-6000 diffractometer using Ni-filtered Cu Kα (0.154 nm) radiation. Transmission electron microscopy (TEM) experiments were performed on a JEOL 2011 microscope operated at 200 kV. N2 adsorption was conducted on a Quantachrome analyzer at 196 1C. Before measurements, the samples were degassed at 180 1C in vacuum for 10 h. The BET method was used to calculate the specific surface areas. The poresize distributions were derived from the adsorption branches of the isotherms using the BJH method. The total pore volumes were calculated from the amount of nitrogen adsorbed at a relative pressure of 0.99.
3. Results and discussion Fig. 1 depicts the XRD patterns of MAs prepared with different inorganic aluminum salts as precursors before and after the hightemperature treatment. It shows that SE–Al(n) exhibits two wellresolved Bragg peaks (Fig. 1A), according to the TEM observation of the well-ordered hexagonal arrays along [110] and [100]
orientations with uniform pore size and wall thickness (Fig. 2A), which can be attributed to p6mm hexagonal symmetry. From the intense (100) peak, a d100 spacing of 9.81 nm is calculated (Table 1), corresponding to a unit cell parameter of 11.3 nm. However, for E–Al(n) prepared without the STPH process, only a broad (100) peak is observed (Fig. 1A), indicating that the STPH plays a key role to synthesize highly ordered mesostructure when Al(NO3)3 9H2O is used as precursor. We assume that the STPH is advantageous for the endothermic hydrolysis reaction of inorganic aluminum salts and thus facilitates the transformation of Al3 þ into Al–OH species. With increasing the concentration of Al–OH species, the hydrogen bonding interaction between P123 and aluminum species will be significantly enhanced, which will promote the cooperative assembly process and further construct an ordered mesostructure of final SE–Al(n). In addition, CA can behave as a ligand and bond with Al–OH species in a bidentate or bridging fashion, which can effectively slow down the condensation reaction of Al–OH species and maintain more Al–OH species to enhance their hydrogen bonding interaction with P123. On the other hand, compared with the XRD pattern of SE–Al(n), SE–Al(c) and SE–Al(s) exhibit relatively lower signal-to-noise ratio in their XRD patterns and broader full width at half-maximum (FWHM) as judged from the (100) peak, suggesting a less mesostructural ordering (Fig. 1A), which confirms the radius and charge of the counteranions will impose a great effect on the assembly
Fig. 1. XRD patterns of calcined (A) and high temperature treated (B) samples.
Fig. 2. TEM images of SE–Al(n) (A), SE–Al(n)–LT (B), and SE–Al–HT (C) (the inset in B is corresponding SAED pattern).
X. Wang et al. / Materials Letters 135 (2014) 35–38
process of the alumina-surfactant mesophase [2]. For NO3 , Cl , and SO24 , the Pauling radiuses are 1.79, 1.81, and 2.30 Å, respectively. NO3 scarcely influences the assembly process due to its small ionic radius and weak complexation ability. However, Cl can strongly coordinate with aluminum ions and thus destroy the organic–inorganic interfacial balance, which would disturb the assembly process. Moreover, for SO24 , the larger ionic radius and stronger hydration ability than those of Cl and NO3 will further disturb the hydrogen bonding interaction between P123 and Al–OH species, leading to a more disordered mesostructure. The N2 adsorption–desorption results show that despite SE–Al (n) and E–Al(n) both exhibit the typical type IV isotherm; compared with E–Al(n), SE–Al(n) shows a steeper capillary condensation step occurring at a relative pressure (P/P0) ranging from 0.40 to 0.60 (Fig. 3A), corresponding to a narrower pore size distribution (Fig. 3B), which further indicates that the STPH can remarkably increase the mesoporous uniformity of MA (Figs. 1 and 2A). For SE–Al(n), the surface area and pore volume are 401 m2/g and 0.47 cm3/g, respectively (Table 1), which are higher than those of samples prepared by the traditional EISA method with the aluminum nitrate as precursor [1,2]. From the small-angle XRD patterns of samples treated at high temperature (Fig. 1B), it can be seen that for E–Al(n)–LT thermally treated at 750 1C, only a very weak diffraction peak is observed, indicating that its mesostructure has been seriously destroyed. And concomitantly in its wide-angle XRD pattern (the inset in Fig. 1B), seven weak diffraction peaks are observed at 2θ ¼19.8, 32.6, 36.9, 39.6, 45.6, 61.5, and 67.21, which can be indexed as the (111), (220), (311), (222), (400), (511), and (440) reflections of γ-alumina (JCPDS card 10-0425), indicating that the amorphous Table 1 The structure parameters of samples before and after high-temperature thermal treatment. Samples
d100 (nm)
P (nm)
S (m2/g)
V (cm3/g)
E–Al(n) SE–Al(n) SE–Al(n)–LT SE–Al(n)–HT
7.24 9.81 6.31 5.97
4.5 4.5 3.7 3.4
175 401 255 247
0.29 0.47 0.29 0.24
Note: d100 is the d-spacing calculated from the first peak, p is the pore size calculated from the adsorption branch using the BJH method, S is BET surface area and V is the total pore volume.
37
Al species in E–Al(n)–LT mesoporous walls are converted to
γ-alumina. In contrast, SE–Al(n)–LT still displays a very strong
(100) peak after the same thermal treatment, indicating that the ordered mesosturcutre is well maintained. TEM image also confirms that SE–Al(n)–LT possesses ordered hexagonal mesostructure (Fig. 2B). Moreover, the selective area electron diffraction (SAED) pattern (the inset in Fig. 2B) of the ordered mesostructure domains of SE–Al(n)–LT indicates the mesoporous walls are still amorphous phase, which confirms that the remarkably increased mesostructural ordering can prevent Al atomic diffusion and sinter at high temperature, and further suppress the formation of crystalline alumina. However, with further increasing thermal treatment temperature to 900 1C, for SE–Al(n)–HT, the relative intensity of (100) peak decreases obviously, demonstrating that the mesostructural ordering has been decreased seriously due to the formation of γ-alumina during the higher temperature thermal treatment process (Fig. 1B). Noteworthy, from the TEM image of SE–Al(n)–HT (Fig. 2C), the ordered hexagonal arrays along [100] orientation with uniform pore size could still be observed, indicating that the ordered mesostructure of SE–Al(n) has not been completely destroyed even after thermal treatment at 900 1C. The extremely high thermal stability of SE–Al(n) is also validated by the N2 adsorption–desorption measurements. For SE–Al(n)–LT and SE–Al(n)–HT, their N2 adsorption–desorption curves still maintain the typical IV isotherm with a H1-type hysteresis loop (Fig. 3A), and the pore size distribution curves (Fig. 3B) are still quite narrow, indicating that the hexagonal mesostructures are well-preserved (Figs. 1A, 2B and C). From Table 1, it can be seen that even after thermal treatment at 900 1C, SE–Al(n)– HT retained 61.6% of the specific surface area and 51.1% of the pore volume compared with the untreated SE–Al(n).
4. Conclusion By using the inexpensive aluminum nitrate as precursor, highly ordered MA with high surface area has been successfully synthesized via an EISA pathway associated with STPH process. The obtained SE–Al(n) displays extremely high thermal stability. The ordered mesostructure can be well preserved even after thermal treatment at 900 1C. Our achievements provide a facile route for low-cost mass production of MA with promising properties for designed catalytic applications in the petroleum industry.
Fig. 3. N2 sorption isotherms (A) and the corresponding pore size distribution curves (B) of samples. For clarity, the isotherms (A) of SE–Al(n), SE–Al(n)–LT, and SE–Al(n)–HT are offset along the Y axis by 20, 200, and 300 cm3/g, respectively, and the corresponding pore size distributions curves (B) are offset by 1, 4.5, and 6.4 cm3/g, respectively.
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X. Wang et al. / Materials Letters 135 (2014) 35–38
Acknowledgment
References
This work was financially supported by the National Natural Science Foundation of China (51172154), the China Postdoctoral Science Foundation (2012M510783), the Shanxi Province Science Foundation for Youths (2012021006-2 and 2013021008-3), and the Science and Technology Project of Shanxi Province (20130313001-3).
[1] Cai WQ, Yu JG, Anand C, Vinu A, Jaroniec M. Chem Mater 2011;23:1147–57. [2] Yuan Q, Yin AX, Luo C, Sun LD, Zhang YW, Duan WT, et al. J Am Chem Soc 2008;130:3465–72. [3] Wu ZX, Li QA, Peng D, Webley PA, Zhao DYJ. Am Chem Soc 2010;132:12042–50. [4] Shang XF, Wang XG, Nie WX, Guo XF, Zou XJ, Ding WZ, et al. J Mater Chem 2012;22:23806–14. [5] Wang XY, Pan DH, Guo M, He M, Niu PY, Li RF. Mater Lett 2013;97:27–30.
Appendix A. Supporting information Supplementary data associated with this article can be found in the online version at http://dx.doi.org/10.1016/j.matlet.2014.07.133.