Atomically dispersed Ru catalysts for polychlorinated aromatic hydrocarbon oxidation

The development of cost-efficient catalysts with good catalytic activity is an urgent task for polychlorinated aromatic hydrocarbon (PCAH) oxidation. Herein, atomically dispersed Ru catalysts (denoted as Ru ADCs) proved by aberration corrected high-angle annular dark-field scanning transmission electron microscopy and X-ray absorption spectroscopy were synthesized for PCAH oxidation. The oxidation results showed that 0.2 Ru ADCs exhibited enhanced catalytic activity (T_50% < 250 °C, T_90% < 300 °C) compared with the T_90% > 300 °C on 0.2 Ru nanoparticles (NPs). Besides, 0.2 Ru ADCs demonstrated high CO₂ yield with >60% CO₂ ratio, along with good stability (>80% conversion for 800 mins). The better performance of 0.2 Ru ADCs was verified by kinetic experiments, in which, the apparent activation energy associated with 0.2 Ru ADCs (50.8 kJ mol^-1) was significantly lower compared with that with 0.2 Ru NPs (80.0 kJ mol^-1). The superior oxidation activity of 0.2 Ru ADCs was also applied to toluene oxidation. H₂ temperature-programmed reduction ensured the stronger interaction of Ru species with the supports in Ru ADCs than that in Ru NPs, thus inhibiting Ru species aggregation and favoring their higher dispersion ensured by CO temperature-programmed desorption. The present work provides a potential strategy to maximize the usage of noble metal catalysts for PCAH oxidation.

Trimetallic RuxMoNi Catalysts Supported on SBA-15 for the Hydrodesulfurization of Dibenzothiophene

In this work, novel trimetallic catalysts based on transition metal sulphides (Ru, Mo and Ni) supported on SBA-15 were synthesized. Citric acid (CA) was used as chelating agent in order to enhance the dispersion of the active phase and minimize the metal-support interaction. Sulfided catalysts were evaluated in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) at 320 °C and 54.5 atm of total H2 pressure. The effects of different Ru/(Ni + Mo) atomic ratios on the active phase were studied. The catalysts were characterized using Micro-Raman spectroscopy, DRIFTS, XRD, XPS, HR-TEM and SEM techniques. Results have shown that there was a better dispersion of the metallic phases, which improves the physicochemical properties of the catalysts, increasing the catalytic activity. The trimetallic RuxMoNi catalyst with the lowest atomic ratio, have shown superior catalytic activity compared to their higher atomic ratio counterparts. The interaction of the chelating agent improved the catalytic activity, which was superior to that observed for NiMo based catalysts, considered one of the most active hydrotreating catalysts.