Support-Dependent Activity and Thermal Stability of Ru-Based Catalysts for Catalytic Combustion of Light Hydrocarbons

Abstract

Ru-based catalysts are the most promising and concerned candidates for catalytic combustion of propane as one of light hydrocarbons (LHs). In this work, different supports such as SiO2, Al2O3, CeO2, and Co3O4 were investigated to unravel the nature of high activity for catalytic combustion of LHs, and effects of Ru content, high-temperature aging, high weight hourly space velocity, and H2O were focused on. The pristine CeO2 was lowly active for catalytic combustion of methane, ethane, and propane (T90C3 > 400 °C), while the pristine Co3O4 and doped Co3O4 presented high activity (T90C3 < 200 °C), the loading of Ru sharply improved the activity of CeO2 especially for ethane and propane (T90C3 < 150 °C) and observably depended on the Ru content, and the promotion of RuOx to Co3O4-based supports was inconspicuous. However, Ru/CeO2 catalysts were inferior to catalytic combustion of methane and lowly resistant to the high-temperature aging compared with Ru/Co3O4 catalysts. Based on characterization results and comparison with SiO2 supports with different surface areas, the Ru–O–M interface or highly dispersed RuOx species were determined as the main active sites for catalytic combustion of LHs and as follows: Ru–O–Ce interface > Ru–O–Co interface ≈ Co3O4 > highly dispersed RuOx ≫ CeO2. Ru-supported Co3O4 and doped Co3O4 especially Ce-doped Co3O4 demonstrated superior versatile activity, stability, and resistance to high temperature and H2O under harsh conditions close to the real full-scale applications, which showed the potential to eliminate the industrial VOC emissions. By contrast, Ru/CeO2 was considered to be promisingly practiced in the portable NMHC detection/monitoring system due to the huge difference in catalytic combustion of ethane/propane and methane. This work was considered to be attributed to the further understanding of the activation of C–H bonds, the optimization of Ru-based catalysts for catalytic combustion of LHs, and the rational screening of potential catalysts for different practical application scenarios.