Direct synthesis and the morphological control of highly ordered mesoporous AlSBA-15 using urea-tetrachloroaluminate as a novel aluminum source

• Published in: Journal of materials chemistry 2012-01, Vol.22 (34), p.17551-17559
• Main Authors: Betiha, Mohamed A, Hassan, Hassan M. A, Al-Sabagh, Ahmed M, Khder, Abd El Rahman S, Ahmed, Emad A
• Format: Article
• Language: English
• Subjects: Acetic acid; Aluminum; Arrays; Channels; Cumene; Lewis acid; Synthesis
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/c2jm32941g

The synthesis of AlSBA-15 under mild acidic conditions was performed through adjusting the molar H 2 O/HCl ratio, which indicates the formation of Si-O-Al linkages that lead to isomorphous substitution of Si 4+ by some Al 3+ ions. In this paper, the direct incorporation of Al 3+ onto a SBA-15 framework in acid mediated synthesis with a n Si/ n Al molar ratio of 7 was optimized using urea tetrachloroaluminate ionic liquid as a new aluminum source. The hydrothermal temperature was varied from 80 to 140 °C and the samples were denoted as AlSBA-15(U x ). The conventional AlSBA-15 also was prepared using direct synthesis [AlSBA-15(D)] and post synthesis [AlSBA-15(P)] aiming to study the influence of aluminum sources and preparation conditions on their structural, textural, and physicochemical properties. The synthesized materials were characterized by N 2 physisorption, XRD, FT-IR, Py-FT-IR, NH 3 -TPD, XRF, HRTEM and SEM. All preparation methods led to the formation of aluminum containing SBA-15 samples with different Si/Al contents. Nevertheless, depending on the preparation methods, the AlSBA-15 samples exhibited different structural, morphology, and surface characteristics, especially in terms of Brønsted and Lewis acid site content. AlSBA-15(U 100 ) had high surface area (813 m 2 g 1 ) and high acidity. TEM images of synthesized AlSBA-15(U 100 ) showed well-ordered hexagonal arrays of uniform cylindrical channels. The effectiveness of AlSBA-15, as an acid catalyst, was studied for the esterification of acetic acid with butanol and cumene cracking. The high activity of AlSBA-15(U 100 ) is attributed to its good ordered structure and high acidity. The synthesis of AlSBA-15 under mild acidic conditions was performed through adjusting the molar H 2 O/HCl ratio, which indicates the formation of Si-O-Al linkages that lead to isomorphous substitution of Si 4+ by some Al 3+ ions.