Mild Process for Reductive Desulfurization of Diesel Fuel Using Sodium Borohydride in Situ Generated via Sodium Metaborate Electroreduction

A novel integrated process was proposed for reductive desulfurization of diesel fuel, in which the reductant sodium borohydride (NaBH4) was in situ generated via sodium metaborate (NaBO2) electroreduction. In order to improve the conversion rate of BO2– into BH4–, NaBO2 electroreduction was fulfilled by applying pulse voltage and using a boron-doped diamond (BDD) thin film electrode. The NaBO2 electroreduction process was analyzed by cyclic voltammetry and 11boron nuclear magnetic resonance (11B NMR) and the factors that influenced desulfurization efficiency were investigated. Under the optimal conditions desulfurization efficiency reached more than 93% for model diesel fuel. The components of model diesel fuel after desulfurization were analyzed by gas chromatography/mass spectrometry (GC/MS) and the electrolyte and digestion solution of precipitate were analyzed by inductively coupled plasma (ICP). Results indicated that B recycle was realized at the same time as desulfurization. Finally, the desulfurization of real diesel fuel was investigated. This work showed that the integrated process may be a new option for desulfurization of diesel fuel due to its mild conditions.