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- Friedel-crafts acylation reaction over hierarchical Y zeolite modified through surfactant mediated technologyPublication . Martins, Angela; Neves, Vera; Moutinho, João; Nunes, Nelson; Carvalho, AnaFriedel-Crafts acylation reaction was studied under mild conditions using hierarchical HY zeolite samples prepared through surfactant mediated technology, in the presence of NH4OH, using CTAB or DTAB as surfactants and changing the duration of treatment from 6 to 48 h. The materials were characterized by powder X-ray diffraction, low temperature N2 adsorption isotherms, SEM microscopy and pyridine adsorption followed by FTIR. The catalytic behaviour was studied in the acylation of furan by acetic anhydride. The catalytic results reflect the role of the duration of the treatment as well as the surfactant molecule used. As the time of treatment increases, the enlargement of the pores leads to an increase of the rate constant and turnover frequency (TOF), except for sample modified during longer time, 48 h, due to the occurrence of secondary reactions that produce larger products or reaction intermediates that become trapped inside the pores. The role of the surfactant molecule is also relevant since the sample modified in the presence of the larger surfactant molecule, CTAB, a significant increase in product yield and rate constant is obtained when compared with the sample prepared in the same conditions using DTAB. However, in that case, by prolonging the treatment a substantial decrease in the same parameters occurs due to the occurrence of deactivation phenomena, pointing out that the optimized modification of porosity needs to be customized according to the needs of each catalytic system.
- 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.