Solvent-free Preparation of Ru/Al2O3 Catalysts for CO2 Methanation: An Example of Frugal Innovation

To reduce the environmental impact of supported catalyst production in compliance with the recommendations of the UN's 12th objective, which encourages more sustainable consumption and production patterns, we propose to revisit sol–gel chemistry in a more frugal mode. The principle of frugal innovation is to simplify products and processes, eliminate complexities to make solutions easier to understand and use, and reduce production costs. By this way, the synthesis of ruthenium-based catalysts supported on γ-AlOOH and γ-Al2O3 is revised via solvent-free sol–gel chemistry. Such catalysts are successfully prepared in one-pot preparation of the active phase and the support using Ru(acac)3/Al alkoxide that requires no sacrificial organic pore-generating agent, no washing, and no filtration and produces no liquid waste. The mixed Ru/Al precursor is hydrolyzed with a stoichiometric amount of water without any solvent. The obtained materials containing 1 and 3% Ru/Al molar ratios have high specific surface areas, from 300 to 690 m2·g–1 and exhibit well dispersed NPs of 1–4 nm on γ-AlOOH with interesting CO2 methanation activity and 100% CH4 selectivity. This proves that a frugal synthesis approach can do as well as traditional synthesis methods while having a much lower environmental impact (cE-factor, water consumption, and energy consumption are 24, 69, and 24 to 42 times lower, respectively) than the standard multistep protocol..