Search

• Hollow spherical PDA-Mo precursors assembled by polymerization of dopamine hydrochloride with Mo 7 O 24 6-. • In-situ pyrolysis method makes the MoO X active sites highly dispersed. • Oxidation of catalyst enlarge meso-/micro-pores, specific surface area and oxygen vacancies. • MoO X /C catalyst exhibits high ODS performance under mild condition. To obtain low-sulfur fuel and reduce SO X emissions, we are developing a MoO X /C hollow sphere catalyst with adjustable oxygen vacancies for oxidative desulfurization (ODS) of fuel. Herein, porous MoO X /C hollow spheres with nanosheet structure were synthesized by pyrolysis of polydopamine-molybdic (PDA-Mo) precursors. The limiting effect of the carbon layer caused MoO X to be uniformly embedded in the carbon support. Then partial oxidization led to forming more meso-/micro-pores and a larger specific surface area (406.4 m2 g−1), and to obtain crystal and abundant oxygen vacancies, thus increasing the content of effective active sites and enhanced the activity of the composite catalyst. Accordingly, the MoO X /C catalysts were employed in oxidative desulfurization (ODS) with H 2 O 2 as an oxidant and displayed excellent performance. The dibenzothiophene (DBT) was eliminated 100% on the optimal catalyst MoO X /C-750–4 within 15 min at 60 ℃ and had a high turnover frequency (22.6 h−1). Furthermore, in-situ formation of C encompassing MoO X could reduce active site leaching and maintain good reaction stability. After eight recycles, the removal rate of DBT was still 98.6%. This study provides a universal in-situ pyrolysis strategy for constructing supported metal oxides and designing high-capacity ODS catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amphiphilic nanoreactor based on natural halloysite nanotube with enclosing MoO x. • Amphiphilic reacting nano-system and highly dispersed active center exhibiting prominent performance. • Confinement effect showing excellent stability. • Oxidation products removing simultaneously by hydrophilic lumen adsorbing. • Simply synthesis, simplified and green process. Hollow nanomaterials are regarded as the outstanding supports due to their confinement effect and stable carries, which can enhance the performance of the supported catalysts and even simplify the process. In this work, halloysite nanotubes (HNT) are chosen as the support due to their monoclinic tubular structures with two different surface compositions and charges. By a simple impregnation-calcination approach, MoO x is immobilized in the internal surface of HNT, then modify with organosilanes on the external surface of HNT to yield the amphiphilic Mo/HNT/S nanoreactor. The catalyst exhibits prominent activity for oxidative desulfurization in solvent-free system, the desulfurization rate of dibenzothiophene (DBT) reaches 100 % and the turnover frequency (TOF) value reaches 67.5 h−1 at 60 °C with 15 min, which is higher than most reported Mo-based catalysts. The hydrophobic surface enables the nanoreactor to be well dispersed in oil phase, and H 2 O 2 solution in the hydrophilic cavity can extract DBT to form a concentrated microenvironment of the reactants and reactive oxygen species. The confinement function of the HNT nanoreactor can enhance the activity and stability of active ingredients (MoO x) over at least 5 cycles. Additionally, oxidation products can be retained in the hydrophilic lumen and completely separated from the model fuel. This amphiphilic catalytic system eliminates the following solvent extraction step in the ODS procedure. Thus, the catalyst is a promising candidate for large-scale industrial application. [ABSTRACT FROM AUTHOR]