Open Access
Zirconia-supported 11-molybdovanadophosphoric acid catalysts: effect of the preparation method on their catalytic activity and selectivity
(Wiley, 2018) El Bakkali, Bouchra; Trautwein, Guido; Alcañiz Monge, Juan; Reinoso, Santiago; Institute for Advanced Materials and Mathematics - INAMAT2; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa; Gobierno de Navarra / Nafarroako Gobernua
The oxidation of adamantane with hydrogen peroxide catalyzed by zirconia-supported 11-molybdovanadophosphoric acid is shown to be a suitable green route for the synthesis of adamantanol and adamantanone. This work evaluates how the catalyst activity and selectivity are affected by some of its preparative parameters, such as the method for supporting the catalytically active heteropoly acid over the zirconia matrix or the pretreatments applied to the resulting materials before being used as heterogeneous catalysts. Our results indicate that the most effective catalysts able to maintain their activity after several reaction runs are those prepared by following the sol-gel route, whereas the most selective catalysts are those obtained by impregnation methods. Moreover, the calcination temperature has also been identified as a relevant parameter influencing the performance of catalysts based on supported heteropoly acids. The increasing catalytic activity observed over several consecutive reaction runs has been attributed to the formation of peroxo derivatives of polyoxometalate clusters at the surface of the catalyst and their accumulation after each reaction cycle.
Open Access
The effects of halogen substituents on the catalytic oxidation of benzylalcohols in the presence of dinuclear oxidovanadium(IV) complex
(Elsevier, 2017) Bikas, Rahman; Shahmoradi, Elaheh; Noshiranzadeh, Nader; Emami, Marzieh; Reinoso, Santiago; Ciencias; Zientziak; Institute for Advanced Materials and Mathematics - INAMAT2
A new dinuclear complex of oxidovanadium(IV), namely [(VO)2(HL)(l-O)] (1), has been synthesized by the reaction of VO(acac)2 with the heptadentate N4O3-donor Schiff base ligand, 2-(5-Bromo-2-hydroxyphenyl)-1,3-bis(2-(5-bromo-2-hydroxybenzylideneamino)ethyl)imidazolidine (H3L). The complex has been characterized by elemental analysis, spectroscopic methods and single-crystal X-ray diffraction. The latter technique revealed that the vanadium ions have distorted octahedral geometry and are connected together by oxido and phenolic oxygen atoms. The bridging oxido ligand shares the equatorial positions of the two metal centers while the oxygen atom of the bridging phenol group connects the axial positions. The catalytic activity of this complex has been tested for the oxidation of some benzyl alcohol derivatives by using H2O2 as a green oxidant. In order to maximize the yields, the effects of various influential parameters in catalytic reactions such as the oxidant-to-substrate molar ratio, the temperature and the solvent, were studied. Moreover, the electronic and steric effects of halogen substituents on the phenyl group of the substrate were also explored by analyzing the oxidation of benzyl alcohol derivatives with F, Cl and Br atoms in the relative para-position (electronic effect), and of another set of substrates with a Cl substituent in relative ortho-, meta, and para-positions (steric effect). The results of these catalytic studies show that complex 1 catalyzes the oxidation of benzyl alcohol derivatives to the corresponding benzaldehydes with little amounts of the benzoic acid being detectable in the reaction mixture. Both the reaction conditions and the substituents on the phenyl group of the benzyl alcohols affect the selectivity and the activity of this catalytic system.

Reinoso, Santiago

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