Study on the HPA immobilisation on Al-SBA-15 support over Brønsted groups

• Published in: Molecular catalysis Vol. 478; p. 110571
• Main Authors: Truong, Thi Hanh, Cuong Do, Van, Mai Do, Ngoc, Hung, Tran Quang, Doan, Huan Van, Nguyen, Thi Nhiem, Doan, Thi Hai, Le, Thi Hoai Nam, Nguyen, Tuyen Van, Bach, Long Giang, Tran, Quang Vinh
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2019
• Subjects: Al-SBA-15; Brønsted; Fructone synthesis; Heterogenization; Heteropoly acid catalyst; proc; Heteropoly acid catalyst; HPA; Heterogenization; Al-SBA-15; Fructone synthesis; Brønsted
• ISSN: 2468-8231; 2468-8231
• DOI: 10.1016/j.mcat.2019.110571

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•Systematically investigating the crucial factors of HPA/Al-SBA-15 preparation including Al-SBA-15 support characteristic (type of functional group and Si/Al molar ratio) and HPA type (commercial and in-situ synthetic HPA).•The important role of NH4+ ion-exchanged Brønsted groups of Al-SBA-15 support on the immobilisation of HPA commercial catalyst on Al-SBA-15 support.•The acidity decrease of HPA immobilised on Al-SBA-15 over NH2 functional groups.•The high catalytic activity and reusability of HPA/Al-SBA-15 in Fructone synthesis.
In this article, a significant aspect of Brønsted groups in the preparation of HPA/Al-SBA-15 catalyst by immobilising heteropoly acid H3PW12O40 (HPA) to mesoporous Al-SBA-15 support was studied. The crucial factors affected the preparation such as functional groups formed on the support, the use of HPA type for the immobilisation (commercial catalyst or in-situ synthetic HPA), and Si/Al molar ratio of Al-SBA-15 were systematically investigated. The prepared catalysts were tested their performance in polar reagent reactions (fructone synthesis was chosen as an example) to show the effect of HPA after the immobilisaton. Here we tested the HPA content (by Energy-dispersive X-ray method), acidity (by temperature-programmed desorption of ammonia method) and the ethyl acetoacetate conversion in fructone synthesis to prove this concept. The other characterisation methods such as small angle x-ray scattering, Fourier-transform infrared spectroscopy, specific surface area and pore volume also showed the properties change of materials before and after HPA immobilisation. It was shown that the HPA/Al-SBA-15 sample prepared by using HPA commercial catalyst and NH4+ ion-exchanged Brønsted groups of mesoporous Al-SBA-15 support (Si/Al molar ratio of 15) showed the highest acidity and catalytic activity (ethyl acetoacetate conversion of 93.49 wt%) in comparison to HPA commercial catalyst as well as to the other catalysts. In addition, this catalyst also showed good catalytic stability after five reaction cycles with slightly reduction of activity, suggesting the prospect of employing HPA/Al-SBA-15 catalyst for organic synthesis of polar compounds.