Dichloro and dimethyl dioxomolybdenum(VI)-bipyridine complexes as catalysts for oxidative desulfurization of dibenzothiophene derivatives under extractive conditions


The complexes [MoO2Me2(2,2'-bipyridine)] (5), [MoO2X2(4,4'-dimethyl-2,2'-bipyridine)] (X = Cl (2), Me (6)), [MoO2Me2(4,4'-di-tert-butyl-2,2'-bipyridine)] (7) and [MoO2X2(4,4'-dinonyl-2,2'-bipyridine)] (X = Cl (4), Me (8)) have been prepared and examined as catalysts in extractive and catalytic oxidative desulfurization (ECODS) of a simulated diesel fuel (3000 ppm S) containing dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. The molecular structures of 6 and 8 were characterized by H-1 NMR, FT-IR and FT-Raman, and X-ray crystallography. The ECODS reaction conditions were optimized for complex 5 by comparing different extraction solvents (MeCN, the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6), polyethylene glycol (PEG) and two PEG-based deep eutectic solvents), and by varying the catalyst and oxidant (H2O2) amounts, and diesel/solvent volume ratio. Under the optimal conditions with [BMIM]PF6 as the extraction solvent, the quantitative elimination of all sulfur compounds from the model diesel was achieved within 3 h at 70 degrees C. A comparison of initial ECODS rates for complexes 2, 4, 6 and 8 indicated that the equatorial N,N-chelate ligand was more important than the axial ligand (X) for the desulfurization catalytic performance, with the best results being obtained for the IL-soluble complexes 4 and 8 . The IL-entrapped catalyst from 4 showed a good capacity to be reused in consecutive desulfurization cycles. (C) 2022 Elsevier B.V. All rights reserved.






Juliao, D; Gomes, AC; Cunha-Silva, L; Pillinger, M; Goncalves, IS; Balula, SS

nossos autores


We acknowledge funding provided within the R&D project Gly-Gold (PTDC/CTM-CTM/31983/2017), and the Associated Labs LAQV-REQUIMTE (UIDB/50006/2020) and CICECO-Aveiro Institute of Materials (UIDB/50011/2020, UIDP/50011/2020 & LA/P/0006/2020), financed by national funds through the FCT (Fundacao para a Ciencia e a Tecnologia)/MEC (Ministerio da Educacao e Ciencia) and when appropriate co-financed by the European Union through the European Regional Development Fund under the Portugal 2020 Partnership Agreement. A.C.G. (CEECIND/02128/2017), L.C.S. (CEECIND/00793/2018) and S.S.B. (CEECIND/03877/2018) thank the FCT/MCTES (Ministerio da Ciencia, Tecnologia e Ensino Superior) for funding through the Individual Call to Scientific Employment Stimulus.

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