Oxidation of Aromatic Sulfur Compounds Catalyzed by Organic Hexacyanoferrates in Ionic Liquids with a Low Concentration of H2O2 as an Oxidant

摘要

A series of organic hexacyanoferrates were synthesized and employed as catalysts in ionic liquids (ILs) for catalytic oxidation of dibenzothiophene (DBT), benzothiophene (BT), and 4,6-dimetnylcdibenzotMophene (4,6-DMDBT), High activity was achieved using 1-butyl-3-metnylimidazolium hexacyanoferrate ([C4mirn]3Fe(CN)6) as a catalyst and 1-butyl-3-methylimidazolium tetrafluoroborate ([C4mirn]BF4) as an extractant in the presence of H2O2 under mild conditions. It was interesting to find that the concentration of H2O2 had a significant influence on desulfurization efficiency. The sulfur removal was 76.3% witn 30 wt % H2O2 as an oxidant, while it could reach 97.9% with 7.5 wt % H2O2. Electron spin resonance (ESR) spectroscopy measurements gave the evidence that the active oxygen species O_2~(·-) was generated in the catalytic oxidative desulfurization process, and gas chrornatography—mass spectrometry (GC—MS) analysis indicated that the sulfur compounds were oxidized to the corresponding sulfones. The influence factors, such as reaction temperature, time, concentration, and dosage of H2O2, amount of catalyst, catalytic system recycling, and different sulfur-containing compounds, were investigated. The kinetic investigations showed, that oxidation of sulfur compounds presented a pseudo-first-order kinetic. Under the optimal conditions, the catalytic system, could be recycled at least 4 times without a remarkable decrease in activity.