Iron-porphyrin encapsulated in poly(methacrylic acid) and mesoporous Al-MCM-41 as catalysts in the oxidation of benzene to phenol

摘要

Poly(methacrylic acid) (PMAA) and mesoporous molecular sieve Al-MCM-41 with Si/Al = 20 were used as supports for the encapsulationudof bulky iron(III)-5,10,15,20-tetra-(4-pyridyl)porphyrin (Fe-TPyP). Metalloporphyrin of Fe(III) was encapsulated inside the mesopores of Al-udMCM-41 by a process of sequential synthesis of Fe-TPyP by treatment of FeCl3 with 5,10,15,20-tetra-(4-pyridyl) porphyrin (TPyP), followedudby encapsulation of Fe-TPyP. Fe-TPyP complexes were also successfully encapsulated in PMAA by polymerizing a monomer (MAA)udwith a cross-linker around the Fe-TPyP complexes. The materials obtained were identified using XRD, UV–vis DR, FTIR and luminescenceudspectroscopies. The oxidation of benzene to phenol using aqueous hydrogen peroxide has been studied using both iron-porphyrin encapsulatedudin poly(methacrylic acid) and mesoporous Al-MCM-41 as catalysts. The encapsulated iron-porphyrin in PMAA (Fe-TPyP–PMAA) give audhigher catalytic activity compared to Fe-TPyP encapsulated in Al-MCM-41 (Fe-TPyP–MCM-41). However, the product selectivity and theudregenerability of Fe-TPyP–PMAA are not as good as than those of Fe-TPyP–MCM-41. One considers that the hydrophobic nature of Fe-udTPyP–PMAA may account for the high catalytic activity, and the ordered structure of Fe-TPyP–MCM-41 may contribute to a high selectivity.ud© 2005 Elsevier B.V. All rights reserved.