A new simple protocol for the synthesis of nanohybrid catalyst for oxidative desulfurization of dibenzothiophene

The Utilization of Rice Husk as Both the Silicon Source and Mesoporous Template for the Green Preparation of Mesoporous TiO2/SiO2 and Its Excellent Catalytic Performance in Oxidative Desulfurization

In recent years, TiO2-based catalysts have received extensive attention from researchers for their excellent oxidative desulfurization (ODS) performances. In this paper, a series of mesoporous TiO2/SiO2 catalysts with different TiO2 loadings are prepared, using an incipient wetness impregnation method with agricultural waste rice husk as both the silicon source and mesoporous template and tetrabutyl titanate as the titanium source. The effect of different TiO2 loadings on the ODS performance of the samples is investigated, and the appropriate TiO2 loading is 2.5%. Compared with pure TiO2, the 2.5%TiO2/SiO2 sample exhibits high catalytic activity for oxidative desulfurization. This is, on the one hand, due to the high specific surface area and mesopore volume of the 2.5%TiO2/SiO2 sample. On the other hand, it is due to the uniform dispersion of TiO2 grains with an average diameter of 6.1 nm on the surface of the mesoporous SiO2 carrier, which greatly increases the active sites of the 2.5%TiO2/SiO2 sample, thus improving the catalytic activity of the sample. The recycling performances of the 2.5%TiO2/SiO2 sample are further investigated. The results show that, after fifteen cycles, the 2.5%TiO2/SiO2 sample still maintains high conversions of dibenzothiophene (99.8%) and 4,6-dimethyldibenzothiophene (99.7%) without deactivation. In addition, the 2.5%TiO2/SiO2 sample treated with TBHP aqueous solution is characterized by the technique of UV-Vis, and the Ti-peroxo (Ti-OOtBu) species, the active intermediate for the ODS of bulky organic sulfides, is successfully captured. Finally, a possible reaction mechanism for the ODS process over the 2.5%TiO2/SiO2 sample is proposed.

Fast and reversible adsorption for dibenzothiophene in fuel oils with metallic nano-copper supported on mesoporous silica

Dibenzothiophene (DBT) in fuel oils causes the release of toxic sulfur oxide gases, and it is necessary to remove DBT in fuels. Herein, metallic copper was loaded on SBA-15 mesoporous silica through simple reduction reactions for the preparation of DBT adsorbents. On an adsorbent with a copper loading of 0.3 wt%, adsorption equilibrium was achieved within 5 min, and a DBT removal rate of 90.4% was achieved. The adsorption isotherm agreed with a linear Freundlich model and adsorption capacity was 12.1 mg sulfur/g. Nano-sized copper particles were observed by TEM, indicating the size effect of copper particles in DBT adsorption. A broad band, corresponding to copper-sulfur coordination bonds, was observed at 300-600 cm^-1 in the Raman spectrum of DBT-doped adsorbent. Meanwhile, the band at 1233 cm^-1 corresponding to C = C (-S) bonds in DBT was shifted to 1229 cm^-1 in DBT adsorbed. XPS and Cu LMM XPS spectra proved that Cu(0) was oxidized by DBT sulfur during adsorption. Furthermore, Auger spectra verified that the adsorption of DBT on Cu(0) involved the formation of Cu(I) and Cu(II) species through coordination bonds. The adsorption capacity could be completely recovered via elution. This work sheds light on the removal of DBT in fuel oils with cost-effective efficient adsorbents.

Insights to the oxidative desulfurization process of fossil fuels over organic and inorganic heterogeneous catalysts: advantages and issues

Strict environmental laws have been put in place around the world to reduce the amount of sulfur in the fuel to reduce the emissions of harmful gases from fuel combustion and improve air quality. Therefore, extensive researches have been undertaken to devise effective processes or to improve the desulfurization processes. Among the desulfurization processes, the oxidative desulfurization (ODS) process is a promising method to achieve very low and near-zero sulfur content of the fuel. In this process, sulfur compounds are converted to the corresponding sulfone by a catalyst and in the presence of an oxidant. The obtained compounds by polar solvents or adsorbents are removed from the fuel. In recent decades, extensive studies have been carried out on the catalysts used in the oxidative desulfurization process. In this review, a comprehensive survey has been performed on heterogeneous catalysts used in the oxidative desulfurization process. According to the reported researches, the heterogeneous catalysts used can be divided into five groups: ionic liquids, carbon materials, polyoxometalates, transition metal oxides stabilized on porous solid substrates, and metal-organic frameworks. The proposed mechanisms with different catalysts have also been studied in this work.