No abstract

Oxidative desulfurization (ODS) is an attractive complementary or alternative process for the hydrodesulfurization (HDS) process due to advantages such as mild operating conditions. In the ODS process, the sulfur-containing compounds are oxidized first to polar sulfoxide and sulfone products and then these polar compounds are separated using solvent extraction or an adsorption process. In the present study, the separation of oxidized sulfur-containing compounds of diesel as a real fuel has been investigated using extraction in a single drop column. The oxidation system was hydrogen peroxide/formic acid. The selected solvent for the extraction of oxidized sulfur-containing compounds was dimethylformamide (DMF). In single drop tests, the effect of various parameters including the drop size (1.70-4.60 mm) and column height (228-550 mm) on the different parameters such as drop velocity and sulfur concentration in the dispersed and continuous phases has been investigated. The outcome of this study provides valuable insights for designing the extraction column for separation of oxidized sulfur-containing compounds from middle distillate fuels in an ODS process.

In this study, a continuous sulfur extraction process in a pilot plant Oldshue–Rushton column has been studied, and its operating cost has been optimized, where the feed of the column was earlier produced in an oxidative desulfurization reactor. Dimethylformamide was used as a polar solvent to remove the sulfur-containing compounds of the oxidized diesel in the extraction column. The effects of agitation speed (100–200 rpm) and inlet flow rate of the solvent to the column (33–165 mL/min) on the holdup, sulfur removal, diesel recovery, and solvent recovery were investigated, utilizing the response surface methodology. The operating cost during the continuous-flow extraction process, consisting of the chemical cost, electricity cost, and the health cost related to the SO2 emission, was also applied as a criterion to optimize the process. The best performance of the extraction process was achieved at ambient temperature, where the inlet flow rate of the oxidized diesel was 99 mL/min, agitation speed was 107 rpm, and inlet flow rate of the solvent was 35 mL/min. In these conditions, dispersed phase holdup, sulfur removal, diesel recovery, and solvent recovery were 0.0101, 92.75, 91.80, and 96.90%, respectively. In addition, a considerable improvement in the sulfur removal as well as chemical consumption cost was achieved.