Magnetically recoverable SiW11Cd@CoFe2O4@PANI nanocomposite as an efficient heterogeneous catalyst for oxidative desulfurization of real and model fuels

Abstract A new inorganic–organic hybrid nanocomposite, SiW 11 Cd@CoFe 2 O 4 @PANI, was synthesized from the potassium salt of Cd (II)-substituted silicotungstate (K 6 SiW 11 CdO 39 ), cobalt ferrite (CoFe 2 O 4 ), and polyaniline (PANI) and evaluated as a heterogeneous catalyst for oxidative desulfurization (ODS) process. The synthesized materials were characterized by Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX). The characterization results supported the formation of the hybrid nanocomposite and the incorporation of K 6 SiW 11 CdO 39 (abbreviated to SiW 11 Cd) within the CoFe 2 O 4 /PANI matrix. The average particle size determined by SEM was approximately 26 nm, while the crystallite size estimated using the Scherrer equation was 21 nm. The catalytic performance of SiW 11 Cd@CoFe 2 O 4 @PANI was evaluated using both real gasoline and model fuel containing dibenzothiophene (DBT), benzothiophene (BT) and thiophene (Th). Under optimized conditions, using H 2 O 2 /CH 3 COOH as the oxidizing system, the total sulfur content of real gasoline decreased from 4988 to 208 ppm, corresponding to approximately 96% sulfur removal after 60 min at 35°C. The enhanced ODS performance is attributed to the combined contribution of the polyoxometalate active sites, magnetic CoFe 2 O 4 support, and PANI matrix. The nanocomposite could be magnetically recovered and reused for five consecutive reaction cycles while retaining most of its catalytic activity. These results demonstrate the potential of SiW 11 Cd@CoFe 2 O 4 @PANI as a recyclable heterogeneous catalyst for the ODS of real and model fuels under relatively mild conditions