Synergistic CO2 hydrogenation over bimetallic Ru/Ni nanoparticles in ionic liquids

Abstract

Abstract The direct conversion of carbon dioxide to hydrocarbons is one of the key solutions to both the reduction of the greenhouse effect and the sustainable production of fuels and lubricants. Here, it is demonstrated that simple bimetallic Ru/Ni nanoparticles (NPs) (2–3\u2009nm, Ru-rich shell, and Ni-rich core) in a hydrophobic ionic liquid (IL) promote the direct hydrogenation of CO2 to light hydrocarbons (HCs) under very mild reaction conditions in a simple batch reactor. The reaction of CO2 with hydrogen (1:4, 8.5\u2009bar) at 150\u2009°C with the Ru/Ni NPs (3:2) in bis((trifluoromethyl)sulfonyl)amide (BMI.NTf2) hydrophobic IL affords C2+ hydrocarbons (79% alkanes and 16% olefins) with 5% CH4 at 30% conversion. However, the reaction performed in the hydrophilic IL 1-n-butyl-3-methyl-1H-imidazol-3-ium tetrafluoroborate affords mainly CO. The catalytic hydrogenation of CO2 towards HCs proceeds by a two-step process with the initial conversion of CO2 into CO by reverse gas shift reaction (RWGS), followed by Fischer-Tropsch Synthesis (FTS). The bimetallic NPs have higher catalytic efficiencies than their monometallic counter- parts, owing to strong synergy between the metals. The presence of Ni in the bimetallic NPs yields a more active RWGS catalyst, and the Ru increases the FTS towards heavier HCs.