Pushing the Product of CO2 Hydrogenation over Ruthenium Catalyst from Methane to C2+ Hydrocarbons by Relay Catalysis

The product of CO2 hydrogenation over Ru-based catalysts is still limited to those of CO and CH4. In this work, we attempt to realize the direct synthesis of C2+ hydrocarbons from CO2 hydrogenation by the relay of the reverse water–gas shift (RWGS) reaction and Fischer–Tropsch reaction over Ru catalysts. We employ a series of preparation methods to adjust the surface ratios of metallic Ru and Ru oxides (Ru0/Ruδ+), including alkali metal promotion, carbon coating, and the construction of bimetallic sites. It was found that an appropriate Ru0/Ruδ+ ratio at around 1.2 is beneficial to the formation of C2+ hydrocarbons, while a high Ru0 content catalyzes the formation of CH4, and a high Ruδ+ content promotes the RWGS reaction. Under 300 °C and 3 MPa, the optimized K-GaRu@C catalyst achieves a C2+ selectivity of 38% at a CO2 conversion of 31%. Our work highlights the universality of relay catalysis, which separates complicated reaction networks into a few controllable steps, thus allowing the selective synthesis of high-value products from CO2 hydrogenation.