49 research outputs found
Mechanistic Features of Oxidative Desulfurization Using Sono-Fenton–Peracetic Acid (Ultrasound/Fe<sup>2+</sup>–CH<sub>3</sub>COOH–H<sub>2</sub>O<sub>2</sub>) System
This article attempts to identify
the links between the chemistry
of oxidative desulfurization and cavitation physics for an ultrasound-assisted
oxidative desulfurization (UAOD) process using Fenton–peracetic
acid as the oxidant. The model system employed was dibenzothiophene
(as a model sulfur compound) and toluene (as a model gasoline/diesel).
Experiments were performed to assess the role of each component of
the oxidant in the chemistry of the process. H<sub>2</sub>O<sub>2</sub> was found to be the key component of the oxidant that balances between
several competing pathways and reactions in overall oxidative desulfurization
process. Addition of Fe<sup>2+</sup> to peracetic acid has a beneficial
effect, whereas excess H<sub>2</sub>O<sub>2</sub> has an adverse effect
on the process. This article also highlights the physical and mechanistic
features of the UAOD process. Transient cavitation is revealed to
play a negative role in the desulfurization process, whereas ultrasound
has a positive effect. The former effect is a consequence of the scavenging
of HO<sub>2</sub><sup>•</sup> radicals in the aqueous phase
by radicals generated by cavitation bubbles, whereas the latter effect
is attributed to the generation of a fine emulsion between the oxidant
and toluene phases as a result of strong micromixing generated by
ultrasound. The results of this study clearly point out that less
scavenging and effective interphase transfer of HO<sub>2</sub><sup>•</sup> radicals are more crucial to the utilization of HO<sub>2</sub><sup>•</sup> radicals for desulfurization than mere
generation