Guidelines to prepare active, selective, and stable supported metal catalysts for CO2 methanation with hydrogen

Abstract

Catalytic thermal hydrogenation of CO2 to CH4 with renewably produced H2 is one of the routes to reduce the CO2 concentration in the atmosphere. In this respect, various catalysts have been developed. Among them, 5% Ru-loaded Al2O3 [Ru(5%)-Al2O3] has shown the highest performance, at 300 °C, in terms of the intrinsic reaction rate and the turnover frequency (TOF), which were 38 mmolCH4 g−1h−1 and 1188 h−1, respectively. The CH4 selectivity of the catalyst was 95%. Despite of the above and other achievements, the developments of the catalysts that exhibit higher performances should be continued. This work now reports that 1% Ru-loaded ETS-10 [Ru(1%)-ETS-10] and 1% Ru-loaded TiO2 [Ru(1%)-TiO2] give the intrinsic reaction rates of 329 and 266 mmolCH4 g−1h−1, TOFs of 3321 and 2684 h−1 with the CH4 selectivities of 85.8 and 97.9%, respectively. In particular, Ru(1%)-ETS-10 is superior to Ru(1%)-TiO2 in terms of the stability (stable for more than 130 h). The analyses of the above three catalysts suggested the guidelines to prepare high performance catalysts, which are the support should be microporous materials and should possess the capability to introduce metal ions into the support by cation exchange so that they can be activated to metal nanoparticles by reduction, the support should be able to stabilize the metal nanoparticles, the active metal catalysts should be 2–5 nm sized three-dimensional (3D) Rux nanoparticles, the loading level of Rux nanoparticles should be 1%, the support should have the affinity to capture CO2 so that the catalyst can have the dual functionality of CO2 capture and CO2 reduction, the Rux nanoparticles should be highly basic, and the prepared Rux nanoparticles should not be poisoned by CO.