Applied Catalysis A: General 269 (2004) 117–121 Novel solvent free liquid-phase oxidation of -pinene over heterogeneous catalysts based on Fe 3-x M x O 4 (M = Co and Mn) Luciano Menini, Márcio J. da Silva, Maria F.F. Lelis 1 , José D. Fabris, Rochel M. Lago, Elena V. Gusevskaya ∗ Departamento de Qu´ ımica, Universidade Federal de Minas Gerais, 31270-901 Belo Horizonte, MG, Brazil Received in revised form 1 April 2004; accepted 3 April 2004 Available online 14 May 2004 Abstract The present work describes a novel oxidation of -pinene, with either dioxygen or hydrogen peroxide, over heterogeneous catalysts based on magnetite doped with Co or Mn, of general formula Fe 3-x M x O 4 (M = Mn, Co; x = 0–0.75) under solvent free conditions. In this process, -pinene is converted to the products valuable for perfume and flavor industries, i.e. pinocarveol, pinocarvone, myrtenol and myrtenal, in excellent selectivity of up to 95%. The total concentration of these derivatives in the final mixture reaches 25–30 wt.%. The catalysts undergo no metal leaching and can be easily recovered either magnetically or by filtration and reused several times. © 2004 Elsevier B.V. All rights reserved. Keywords: -Pinene; Heterogeneous catalysts; Mixed iron oxides; Oxidation 1. Introduction The application of solid materials in liquid-phase catalytic reactions has recently been extensively investigated in at- tempts to replace conventional homogeneous systems. Het- erogeneous catalysts represent important technological and environmental advantages due to facile recovering and recy- cling. In addition, the incorporation of active metal species in solid matrices results in a site-isolation preventing their aggregation to less reactive complexes [1,2]. In some cases, solid catalysts can show even better catalytic performance than their homogeneous counterparts. The heterogenization of active homogeneous redox systems employed as catalysts in oxidative reactions in the liquid phase has increasingly become an important goal in catalysis research. Various ap- proaches have been investigated for the immobilization of redox metal ions in a solid material, such as isomorphous substitution in the crystallographic positions of the inorganic ∗ Corresponding author. Tel.: +55-31-34995755; fax: +55-31-34995700. E-mail address: elena@dedalus.lcc.ufmg.br (E.V. Gusevskaya). 1 Present address: Departamento de Qu´ ımica, Universidade Federal do Esp´ ırito Santo, Campus—Goiabeiras, 29060-900 Vit´ oria, ES, Brazil. framework, impregnation of metal compounds onto a sur- face, tethering metal complexes to the surface via a spacer ligand, encapsulation into a solid matrix, etc. [1]. Spinel ferrites such as magnetite doped with transition metals also form an important class of materials for ox- idative catalysis. Iron can be easily replaced in the mag- netite structure by various other cations maintaining the spinel framework [3–6], and this can strongly affects the physico-chemical behavior of the resulting solid. Incorpora- tion of transition metals such as Ni, Cu [7], Mn [4] or Co [3] in the spinel lattice can significantly modify the redox properties of ferrites and influences their stability. We have recently studied the catalytic behavior of Mn- and Co-doped magnetites in the liquid-phase oxidation of organic contam- inants with hydrogen peroxide [8] and in the gas-phase aer- obic oxidation of carbon monoxide [9]. It was observed a remarkable effect of the partial replacement of Fe for Mn or Co in the spinel framework on the catalytic activity. The aim of the present work was to apply various spinel ferrites to the liquid-phase selective oxidation of a renewable monoterpene, i.e. -pinene, with clean, inexpensive oxidants such as dioxygen and hydrogen peroxide. Terpenic aldehy- des, alcohols and esters often show valuable organoleptic properties and form the largest group of modern fragrance 0926-860X/$ – see front matter © 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2004.04.005