Oxidative Desulfurization and Denitrogenation of Simulated Fuels Catalyzed by TBAPMo_(11)Cu@CuO as a High-Performance and Recoverable Heterogeneous Phase-Transfer Catalyst

摘要

Aimed at catalytic oxidative desulfurization (cat-ODS) of sulfur-containing aromatic compounds (SAs) and catalytic oxidative denitrogenation (cat-ODN) of nitrogen-containing aromatic components (NAs) to control air pollution, we successfully designed and synthesized a new green catalyst (named as TBAPMo(11)Cu@CuO) based on quaternary ammonium salt of copper(II)-monosubstituted phosphomolybdate [(n-C4H9)(4)N][PMo11CuO39] (TBAPMo(11)Cu) and copper oxide (CuO) via a sol-gel method. Cat-ODS and cat-ODN processes of SAs (thiophene (Th) and dibenzothiophene (DBT)), NAs (pyridine (Py) and carbazole (CBZ)) were carried out using hydrogen peroxide green oxidant and poly(ethylene glycol) (PEG-200), which is considered as a green extractant over a TBAPMo(11)Cu@CuO catalyst. This new catalyst demonstrated a superb catalytic activity in the oxidation of SAs and NAs and long-term stability for producing ultraclean fuels: 97, 98, 99, and 98% values of conversion were obtained for Th, DBT, Py, and CBZ, respectively, at 35 degrees C. The results proved that Th and DBT were converted to the corresponding sulfoxides and sulfones, while Py and CBZ were oxidized to the corresponding N-oxides. Accordingly, the oxidized product of CBZ was identified as carbazole-9-carbaldehyde. Also, the removal of a considerable amount of Th, DBT, Py, and CBZ is possible via catalytic oxidation-extraction; however, simple solvent extraction (using methanol, ethanol, and acetonitrile) was inadequate for deep denitrogenation and desulfurization. TBAPMo(11)Cu@CuO as a catalyst indicated excellent reusability for five oxidation cycles. The high performance of TBAPMo(11)Cu@CuO/H2O2/PEG-200 can prove it as a promising green method for fuel purification.