Oxidative desulfurization of dibenzothiophene by magnetically recoverable polyoxometalate-based nanocatalyst: Optimization by response surface methodology

Abstract

Abstract This research investigates the catalytic activity of a new core-shell structured nanocatalyst, which was prepared by surface modification of magnetic silica nanoparticles with Keplerate nano-porous molybdenum oxide-based polyoxometalate ({Mo132}), in oxidative desulfurization (ODS) of dibenzothiophene (DBT) in n-octane as simulated fuel (SF). The characterization of the as-prepared catalyst was performed by several methods including XRD, FTIR, VSM, TEM, HRTEM, SEM/EDS, HAADF-STEM EDX line scan, ICP-OES, and CHNS analysis. The optimization process and design of experiments were performed by response surface method with the principles of central composite design (CCD). The effects of reaction conditions including temperature (X1), O/S molar ratio (X2), and concentration of the catalyst (X3) were assessed on DBT removal efficiency. The statistical results showed that temperature was the most effective parameter in the process. Meanwhile, optimal conditions for DBT removal were attained when the dosage of the catalyst, O/S molar ratio, and temperature were 0.0074 g cat. g-1 SF, 20.7, and 58 oC, respectively. Moreover, a sulfur removal of 99.94% was obtained for SF using the prepared catalyst within 30 min under the optimal reaction conditions. The recovery of catalysts from the reaction medium was done with a magnet and the performance of the recovered catalyst showed no loss in activity after four test runs.