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Keywords:

  • Clays;
  • Lignin models;
  • Oxidation;
  • Porphyrins;
  • Supported catalysts

Abstract

A biomimetic system for lignin peroxidase (LiP) was designed by using a cationic porphyrin, [Mn(TMePyP)OAc5], supported on the smectitic clay montmorillonite [Mn(TMePyP)/clay]. The natural role of the polypeptidic pocket of LiP was mimicked by the clay. The possibility to use low-molecular-weight redox mediators as active readily diffusible oxidizing species has been investigated. This assembly — a sort of “synthetic enzyme” — can be defined as an immobilized porphyrin-mediator system (clay-PMS). The clay-PMS was found to be a stable, recyclable, and efficient catalyst for the environmentally friendly H2O2-catalyzed oxidation of different lignins and representative lignin model compounds. The clay-PMS showed a higher reactivity than Mn(TMePyP)/clay alone due to an effective role of the redox mediator on the oxidation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)