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- The influence of multiwalled carbon nanotubes and graphene oxide additives on the catalytic activity of 3d metal catalysts towards 1-phenylethanol oxidationPublication . Da Costa Ribeiro, Ana Paula; Fontolana, Emmanuele; Alegria, Elisabete; Kopylovich, Maximilian; Bertani, Roberta; Pombeiro, Armando3d metal (Cu, Fe, Co, V) containing composite catalysts for the solvent-free microwave-assisted trans-formation of 1-phenylethanol to acetophenone with tert-butyl hydroperoxide (TBHP) as oxidant wereprepared by ball milling. The influence of multiwalled carbon nanotubes (CNTs) and graphene oxide (GO)additives on the catalytic activity of the catalysts was studied. CNTs or GO were mixed by ball millingwith the metal salts (CoCl2), oxides (CuO, Fe2O3, V2O5) or binary systems (Fe2O3-CoCl2, CoCl2-V2O5, CuO-Fe2O3). For CoCl2-based catalytic systems, addition of small amounts (0.1–5%) of CNTs or GO leads tosignificant improvement in catalytic activity, e.g. 1% of the CNTs additive allows to rise yields from 28to 77%, under the same catalytic conditions. The CoCl2-5%CNTs composite is the most active among thestudied ones with 85% yield and TON of 43 after 1 h
- Ultrasound and radiation-induced catalytic oxidation of 1-phenylethanol to acetophenone with iron-containing particulate catalystsPublication . Soliman, Mohamed Mostafa Aboelhassan; Kopylovich, Maximilian N.; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Ferraria, Ana Maria; Rego, Ana; Correia, Luís M. M.; Saraiva, Marta S.; Pombeiro, ArmandoIron-containingparticulatecatalystsof0.1–1 µmsizewerepreparedbywetandball-milling procedures from common salts and characterized by FTIR, TGA, UV-Vis, PXRD, FEG-SEM, and XPS analyses. It was found that when the wet method was used, semi-spherical magnetic nanoparticles were formed, whereas the mechanochemical method resulted in the formation of nonmagnetic microscale needles and rectangles. Catalytic activity of the prepared materials in the oxidation of 1-phenylethanol to acetophenone was assessed under conventional heating, microwave (MW) irradiation, ultrasound (US), and oscillating magnetic field of high frequency (induction heating). In general, the catalysts obtained by wet methods exhibit lower activities, whereas the materials prepared by ball milling afford better acetophenone yields (up to 83%). A significant increase in yield (up to 4 times) was observed under the induction heating if compared to conventional heating. The study demonstrated that MW, US irradiations, and induction heating may have great potential as alternative ways to activate the catalytic system for alcohol oxidation. The possibility of the synthesized material to be magnetically recoverable has been also verified.
- N2O-Free single-pot conversion of cyclohexane to adipic acid catalysed by an iron(II) scorpionate complexPublication . Da Costa Ribeiro, Ana Paula; Martins, Luisa; Pombeiro, ArmandoThe highly efficient eco-friendly synthesis of adipic acid (96% yield, 98% selectivity, TONs up to 1.8 × 103) directly from cyclohexane is achieved by using ozone and [FeCl2{κ3-HC(pz)3}] (pz = pyrazol-1-yl) in a solvent-, heating-, radiation- and N2O-free new protocol.
- Supported C-Scorpionate Vanadium(IV) Complexes as Reusable Catalysts for Xylene OxidationPublication . Wang, Jiawei; Martins, Luisa; Da Costa Ribeiro, Ana Paula; Carabineiro, Sonia Alexandra Correia; Figueiredo, José L.; Pombeiro, ArmandoC-Scorpionate vanadium(IV) [VOxCl3-x{k(3)-RC(pz)(3)}] [pz = pyrazol-1-yl; x=0, R = SO3 (1); x = 1, R= CH2OH (2) or CH2OSO2Me (3)] complexes supported on functionalized carbon nanotubes (CNTs) are the first V-scorpionate catalysts used so far for the neat oxidation of o-, m- or p-xylene, with TBHP (70% aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p-toluic acid yield of 43% (73% selectivity, TON = 1.34 V 10(3)) was obtained with 2@CNT in a simple microwave-assisted mild oxidation procedure, using a very low catalyst charge (3.2 x 10(-2) mol% vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for oxidation of xylenes. Moreover, reuse of catalysts with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed.
- Ball milling as an effective method to prepare magnetically recoverable heterometallic catalysts for alcohol oxidationPublication . Fontolan, Emmanuele; Alegria, Elisabete; Da Costa Ribeiro, Ana Paula; Kopylovich, Maximilian; Bertani, Roberta; Pombeiro, ArmandoHeterometallic double Fe2O3–CoCl2, CoCl2–V2O5, MoO3–V2O5, and triple CuO–Fe2O3–CoCl2 3d metal dispersed systems were easily prepared by ball milling at room temperature and characterized by scanning electron microscopy (SEM), field emission gun scanning electron microscopy (FEGSEM), energydispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM). They catalyze the microwave-assisted solvent-free heterogeneous oxidation of 1-phenylethanol to acetophenone with tert-butyl hydroperoxide (t-BuOOH) as oxidant, used as a model reaction. In most of the heterometallic systems a significant improvement in the catalytic activity was observed in comparison to homometallic ones. For the tested catalytic systems and experimental conditions, the CuO–Fe2O3–CoCl2 and Fe2O3–CoCl2 systems exhibit the highest activity with maximum 78% yield and TON 39 after 1 h. The possibility of magnetic recovery of the catalysts was demonstrated for the Fe2O3–CoCl2 (3:1) system.
- Synergistic catalytic action of vanadia-titania composites towards the microwave-assisted benzoin oxidationPublication . Ferretti, Francesco; Da Costa Ribeiro, Ana Paula; Alegria, Elisabete; Ferraria, Ana Maria; Kopylovich, Maximilian; Guedes Da Silva, M. Fátima C.; Marchetti, Fabio; Pombeiro, ArmandoIntensification of chemical processes according to the motto "faster, simpler, greener" is among the main concerns nowadays. One of the ways of intensification is the application of synergistic catalytic effects when the overall efficiency of a composite catalyst is much higher than the sum of the component activities. Here, we report on the preparation of synergistic catalytic materials by a simple and straightforward ball milling procedure. Oxidation of benzoin was selected as a model reaction to demonstrate the viability of the concept. For the V2O5-TiO2 (95 : 5) composite material, the synergistic effect is triggered by low power microwave irradiation with more than a tenfold jump in the catalytic activity in comparison to the activities of the individual components.
- Copper(II) complexes with an arylhydrazone of methyl 2-cyanoacetate as effective catalysts in the microwave-assisted oxidation of cyclohexanePublication . Jlassi, Raja; Da Costa Ribeiro, Ana Paula; Alegria, Elisabete; Naili, Houcine; Tiago, Gonçalo; Rueffer, Tobias; Lang, Heinrich; Zubkov, Fedor; Pombeiro, Armando; Rekik, WalidReaction of sodium (E/Z)-2-(2-(1-cyano-2-methoxy-2-oxoethylidene) hydrazinyl) benzene-sulfonate (NaHL) with copper(II) nitrate hydrate in the presence of imidazole (im) in methanol affords [CuL(im)(H2O)] (1). Complex 1 is characterized by IR spectroscopy and ESI-MS spectrometry, elemental and single crystal X-ray crystal structural analyses. The coordination environment of the central copper(II) is nearly intermediate between ideal square-based pyramidal and trigonal bipyramidal geometry, three sites being occupied by the L2- ligand, which chelates in the O, N, O fashion, while two other sites are filled with the water and imidazole molecules. Extensive intermolecular hydrogen bonds between the L2-, water and imidazole ligands lead to a 3D supramolecular network. 1 and known Cu(II) complexes [Cu(H2O)(2)L]center dot H2O (2), [Cu(H2O)(py)L]center dot H2O (3) and [Cu-3(mu(3)-OH)(NO3)(CH3OH)(mu(2)-X)(3)(mu(2)-HL)] (4) act as effective catalysts in the oxidation of cyclohexane to cyclohexanol and cyclohexanone, using low power microwave (MW) irradiation, under mild conditions. Without a promoter, the activity of the catalyst reached a turnover number of 1.44 x 10(3) and a turnover frequency of 1.98 x 10(3) h(-1), after 2 h, at 50 degrees C. (C) 2017 Elsevier B.V. All rights reserved.
- Nickel (ii)-2-amino-4-alkoxy-1,3,5-triazapentadienate complexes as catalysts for heck and henry reactionsPublication . Da Costa Ribeiro, Ana Paula; Karabach, Yauhen; Martins, Luisa; Mahmoud, Abdallah G.; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoNickel (II)-triazapentadienate complexes, [Ni(tap)(2)], are synthesized and found to act as catalysts in the Heck reaction of deactivated aryl halides. The use of room-temperature ionic liquids instead of organic solvents allows easy separation of the catalyst from the products and substrates. The synthesized complexes also catalyse the Henry reaction of benzaldehydes with nitroethane, at 25 degrees C, leading to the corresponding nitroalkanols with diastereoselectivity in favour of the anti isomer.
- Catalytic performance of Fe(II)-scorpionate complexes towards cyclohexane oxidation in organic, ionic liquid and/or supercritical CO2 media: a comparative studyPublication . Da Costa Ribeiro, Ana Paula; Martins, Luisa; Alegria, Elisabete; Matias, Inês A. S.; Duarte, Tiago A. G.; Pombeiro, ArmandoThe catalytic activity of the iron(II) C-scorpionate complexes [FeCl2{HC(pz)3}] 1 (pz = pyrazol-1-yl) and [FeCl2{HOCH2C(pz)3}] 2, and of their precursor FeCl2·2H2O 3, towards cyclohexane oxidation with tert-butyl hydroperoxide was evaluated and compared in different media: acetonitrile, ionic liquids (1-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], and 1-butyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, [bmim][FAP]), supercritical carbon dioxide (scCO2), and scCO2/[bmim][X] (X = PF6 or FAP) mixtures. The use of such alternative solvents led to efficient and selective protocols for the oxidation of cyclohexane. Moreover, tuning the alcohol/ketone selectivity was possible by choosing the suitable solvent.
- Nickel (ii)-2-amino-4-alkoxy-1,3,5-triazapentadienate complexes as catalysts for heck and henry reactionsPublication . Da Costa Ribeiro, Ana Paula; Karabach, Yauhen Yu; Martins, Luisa; Mahmoud, Abdallah G.; Guedes Da Silva, M. Fátima C.; Pombeiro, ArmandoNickel (II)-triazapentadienate complexes, [Ni(tap)(2)], are synthesized and found to act as catalysts in the Heck reaction of deactivated aryl halides. The use of room-temperature ionic liquids instead of organic solvents allows easy separation of the catalyst from the products and substrates. The synthesized complexes also catalyse the Henry reaction of benzaldehydes with nitroethane, at 25 degrees C, leading to the corresponding nitroalkanols with diastereoselectivity in favour of the anti isomer.
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