Unveiling the structure-performance of MoO3/La2O2CO3 for ultra-deep aerobic oxidative desulfurization of diesel

Abstract

The production of clean fuel via the aerobic oxidative desulfurization (ODS) technique is a potential substitute due to its moderate reaction conditions and outstanding catalytic efficiency. However, the relationship between the catalyst structure and the catalytic performance for sulfur-containing compounds with high steric hindrance effect in this process remains unclear hitherto. Herein, a series of MoO3/La2O2CO3 catalysts with various MoO3 particle sizes were carefully designed and prepared through a facile citric acid-assisted hydrothermal strategy. The structures of the loaded Mo-based catalysts were analyzed by series characterization methods, and their structure-performance relationships were investigated for catalytic ODS of 4,6-dimethyldibenzothiophene (4,6-DMDBT). The results revealed that the particle size of MoO3 significantly influenced the redox properties, reactive oxygen species, and ODS performances of MoO3/La2O2CO3 catalysts. With the decrease of MoO3 crystal size from 15.8 nm to 5.3 nm, the ODS performances of MoO3/La2O2CO3 catalysts considerably increased. Among them, MoO3/La2O2CO3-3 exhibited the best ODS activity with complete 4,6-DMDBT conversion within 2.5 h at 130 °C because of its appropriate MoO3 size and the lowest apparent activation energy (Ea). Nevertheless, further downsizing the crystal size of MoO3 to 2.8 nm resulted in a significant increase in the Ea, which dramatically suppressed the catalytic ODS performance of the corresponding MoO3/La2O2CO3-4 catalyst instead. It therefore reveals for the first time that there is a balance between the geometry and the catalytic efficiency of MoO3/La2O2CO3 catalysts for catalytic ODS of 4,6-DMDBT with high steric hindrance effect, which could provide insight for developing advanced ODS catalysts in the future.