Effective CO2 methanation over site-specified ruthenium nanoparticles loaded on TiO2/palygorskite nanocomposite

Abstract

Here a site-specifically assembled Ru nanoparticles (2–8 nm) on palygorskite (Pal) loaded TiO2 catalyst (TiO2/Pal) is reported to trigger the CO-radical mediated CO2 methanation reactions. The catalyst was prepared by the strong electrostatic adsorption (SEA) method based on the interactions between the metal source and the TiO2 support, which have successfully prevented the Ru nanoparticles (NPs) from aggregation. The optimized Ru(4%)-TiO2/Pal sample showed fairly good catalytic activities (μmax = 88.7%) to CO2 and selectivity of CH4 (Cmax ∼ 100%). The catalyst also demonstrated excellent stability: no obvious decedent in CO2 conversion and no carbon deposition were detected after 60 h methanation test. In situ FTIR measurement showed the CO species were an intermediate state, which reacted with the adsorbed hydrogen to produce hydro carbonate, bidentate or monodentate formate species, and finally reached the methane molecular. The SEA method has proven to be an effective way to produce site-specified nano-composites under delicately controlled conditions. Nanofibrous Pal acted as TiO2 carrier and separator, surface hydroxyls supplier, and origin of repulsive force to the Ru species, which finally resulted in outstanding catalytic performance.