Synthesis of 7-hydroxy-4-methyl coumarin over Lewis acid metal ion-exchanged ZAPO-5 molecular sieves

• Published in: Microporous and mesoporous materials Vol. 118; no. 1; pp. 523 - 530
• Main Authors: Gopalakrishnan, S., Viswanathan, K.R., Vishnu Priya, S., Herbert Mabel, J., Palanichamy, M., Murugesan, V.
• Format: Journal Article
• Language: English
• Published: AMSTERDAM Elsevier Inc 01.02.2009; Elsevier
• Subjects: Chemistry; Chemistry, Applied; Chemistry, Physical; Coumarin; Ion-exchange; Lewis acid; Materials Science; Materials Science, Multidisciplinary; Nanoscience & Nanotechnology; Physical Sciences; Science & Technology; Science & Technology - Other Topics; Technology; TPD (ammonia); Zinc aluminophosphate; Lewis acid; Ion-exchange; Zinc aluminophosphate; TPD (ammonia); Coumarin; ALUMINOPHOSPHATES; METHYLATION; PHENOL; HETEROGENEOUS CATALYSIS; CATALYTIC-PROPERTIES; CONDENSATION; DERIVATIVES; ZEOLITE
• ISSN: 1387-1811; 1873-3093
• DOI: 10.1016/j.micromeso.2008.09.030

Zinc aluminophosphate (ZAPO-5) molecular sieve was synthesized hydrothermally and ion-exchanged with Lewis acid metal ions such as Ga 3+, In 3+, La 3+ and Ce 3+ by wet method. The materials were characterized by XRD, FT-IR, BET, ICP-AES, 27Al and 31P MAS NMR, SEM, TPD (ammonia) and TGA. XRD patterns of ion-exchanged molecular sieves appeared almost the same as that of parent ZAPO-5 thus illustrating absence of structural degradation during ion-exchange. However, BET surface area and ICP-AES analysis indicate a small amount of non-framework oxide present in the ion-exchanged catalysts. 27Al and 31P NMR account for the incorporation of zinc in the framework of AlPO-5. The thermograms of metal ion-exchanged ZAPO-5 showed a weight loss between 550 °C and 600 °C for all ion-exchanged materials. This is assigned to the decomposition of M ( OH ) 2 + into MO + species. The total acidity of the materials decreased after ion-exchange as revealed from TPD (ammonia) study. It also showed selective ion-exchange of strong acid sites by Ga 3+, In 3+, La 3+ and Ce 3+ ions. Their catalytic activity was tested in the solvent free synthesis of coumarin using resorcinol and ethyl acetoacetate in the liquid phase. Lewis acid ion-exchanged catalysts showed higher activity than the parent ZAPO-5. The Lewis acid metal ion could act as a template which brings the reactants to its co-ordination sphere and subsequently reacts to form coumarin.