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- Eco-friendly cyclohexane oxidation by a V-scorpionate complex immobilized at hierarchical MOR zeolitePublication . Ottaviani, Davide; Van-Dúnem, Vanmira; Carvalho, Ana; Martins, Angela; Martins, LuisaThe hydrotris(3,5-dimethylpyrazol-1-yl)borate dioxido-vanadium(V) complex [VO2{HB(3,5-Me(2)pz)(3)}] (V, pz= pyrazol-1-yl) immobilized at hierarchical MOR zeolite modified through surfactant mediated technology using NaOH as alkaline agent, V@MOR_NaOH, provides an efficient (TON up to 5.2x10(2)) catalyst for the peroxidative oxidation of cyclohexane with tert-butyl hydroperoxide to KA oil (52% yield), at room temperature, and is easily recovered and reused up to four consecutive catalytic cycles with no significant leaching of vanadium. The textural modifications performed on the zeolitic matrix produced an effective support for the anchorage of the vanadium complex allowing an improved catalytic performance and reusability. This work constitutes an unprecedented use of supported vanadium B-scorpionate complexes as catalysts for the oxidation of alkanes.
- Improved cyclohexane oxidation catalyzed by a heterogenized Iron (II) complex on hierarchical Y zeolite through surfactant mediated technologyPublication . Van-Dúnem, Vanmira; Carvalho, Ana; Martins, Luisa; Martins, AngelaThe hydrotris (pyrazol-1-yl) methane iron (II) complex [FeCl2 (Tpm)] [Tpm=HC(C3N2H3)3] was successfully immobilized, by the incipient wetness impregnation method, in parent and hierarchical Y zeolite modified through surfactant mediated methodology using different bases (NH4OH, NaOH or TPAOH). The catalytic performance and recyclability of supported Fe complex was evaluated in the oxidation of cyclohexane with hydrogen peroxide to cyclohexanol and cyclohexanone under mild conditions and two distinct behaviors were observed: using commercial Y and modified Y with NaOH the complex is anchored mainly at the outer surface of the zeolite supports, resulting in high lixiviation after the first catalytic cycle. When NH4OH and TPAOH are used during the zeolite treatments the particular textural parameters exhibited by these two supports are able to effectively retain the complex molecules, resulting in a high recyclability observed after three consecutive cycles, especially when NH4OH treated zeolite was used as support.