Comparing the Catalytic Activity of Silica-Supported Vanadium Oxides and the Polymer Nanofiber-Supported Oxidovanadium(IV) Complex toward Oxidation of Refractory Organosulfur Compounds in Hydrotreated Diesel

Abstract

Silica-supported vanadium oxides (V x O y -silica 600 °C) and polymer nanofiber [2-(2′-hydroxy-5′-ethenylphenyl)­imidazole (PIMv) and styrene (ST) copolymer]-supported oxidovanadium­(IV) ([VIVO-p­(PIMv-co-ST)]) were synthesized and used as catalysts for the oxidation of refractory organosulfur compounds in fuels in a continuous flow system. Conversion of dibenzothiophene (DBT) to dibenzothiophene sulfone (DBTO2) increased as the flow rate decreased, reaching 100% at flow rates of 0.1 and 0.2 mL/h for (V x O y -silica 600 °C) and [VIVO-p­(PIMv-co-ST)], respectively. This was attributed to improved contact time between the catalyst and substrate, which allowed further oxidation to take place. However, the catalytic activity of V x O y -silica 600 °C dropped by 33% after the first oxidation cycle at a flow rate of 0.1 mL/h at 60 °C, unlike [VIVO-p­(PIMv-co-ST)], which maintained its activity at 100% after three cycles. Optimized conditions were employed in the oxidation of a hydrotreated fuel sample (Sasol diesel 500) followed by extraction of the resulting sulfones using acetonitrile. Analyses of the fuel samples using two dimensional gas chomatography coupled to sulfur cheminiluscence and time-of-flight mass spectrometer detectors (GC × GC-SCD and GC × GC-HRT) confirmed the oxidation of organosulfur compounds and removal of the resulting sulfones. This study revealed that [VIVO-p­(PIMv-co-ST)] was a more robust and more efficient catalyst for the oxidation of organosulfur compounds compared to (V x O y -silica 600 °C). Monitoring the 51V electron paramagnetic resonance signal from the catalysts upon adding oxidant and then substrate showed that the catalysis is of redox nature, involving the V4+ sites.

Vanadium: Biological, Environmental, and Engineering Aspects

“…Silica-supported vanadium oxides, V x O 7 -silica, have been employed as catalysts in the oxidative detoxification of the remains of organic sulfur compounds, such as dibenzothiophene, present in the crude oil and diesel fuels, through conversion into sulfones, which may be removed with acetonitrile. The oxidant employed in this reaction is t-BuOOH [60].…”

The photoelectron-imaging spectroscopic study and chemical bonding analysis of VO2−, NbO2− and TaO2−

“…In addition, these investigations and valuable reactions inspired us to design supported metal oxide catalysts at the molecular level. [4][5][6] As the reactivity of supported catalysts is known to depend on the particle size of catalysts, there has been a focus on the chemistry of gas-phase size-selected oxide clusters as model catalytic systems. [7][8][9][10][11][12][13] Moreover, vanadium, niobium and tantalum oxides have been extensively studied in the gas phase and solid matrices via spectroscopy.…”