Amphiphilic halloysite nanotube enclosing molybdenum oxide as nanoreactor for efficient desulfurization of model fuels

Abstract

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, MoOx 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 H2O2 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 (MoOx) 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.