Constructing Dual-Function TiO2/MWCNTs-NH2-HPW Composites as Both Catalysts and Adsorbents for Highly Efficient Oxidative Adsorption Desulfurization in Fuel Oil

The rational design of efficient polar heterogeneous catalysts for catalytic oxidative-adsorptive desulfurization (OADS) in fuel oil is of paramount significance in the field of environmental remediation. Herein, we fabricate a polar heterogeneous catalyst (titanium dioxide-assisted phosphotungstic acid supported aminated multiwalled carbon nanotubes (TiO2/MWCNTs-NH2-HPW)) with highly effective oxidative-adsorptive desulfurization (OADS) performance, which was prepared by depositing titanium dioxide and immobilizing phosphotungstic acid (HPW) on aminated multiwalled carbon nanotubes (NH2-MWCNTs). HPW, as a catalytic center, is immobilized on MWCNTs-NH2 via the positive charge of -NH3+ by electrostatic attraction. More importantly, amorphous titanium dioxides that contain Ti-OH, as adsorption centers, are well coated on MWCNTs-NH2-HPW, and the polarity of the catalysts can be easily tuned by loading different amounts of polar TiO2 (with abundant -OH), which can affect their catalytic performance and improve their adsorption capacity. The 15% TiO2/MWCNTs-NH2-HPW catalyst exhibits the highest desulfurization performance, and its dibenzothiophene (DBT) removal efficiency can reach 99% in 30 min at 60 degrees C without using an extractant. Its equilibrium adsorption capacity of the S element is approximately 63.36 mg/g because polar groups, such as -OH from TiO2 and -NH2, can effectively adsorb oxidation products (sulfoxide or sulfones) by hydrogen bonding. Furthermore, a possible OADS mechanism of TiO2/MWCNTs-NH2-HPW is proposed by monitoring the desulfurization process via gas chromatography (GC) and Fourier transform infrared (FTIR). This work provides a rational design strategy for constructing dual-function composites as both catalysts and adsorbents for oxidative-adsorptive desulfurization in fuel oil.

Automated summary

This study presents the fabrication of a polar heterogeneous catalyst for catalytic oxidative-adsorptive desulfurization in fuel oil. The catalyst showed high desulfurization efficiency, with 99% DBT removal efficiency in 30 minutes, and can serve as a dual-function composite with both catalytic and adsorption properties.