Monoclinic zro2

Various potassium and rubidium loadings on 2% Pt/ZrO₂ were prepared via incipient wetness impregnation (IWI). Firstly, monoclinic ZrO₂ (Alfa Aesar, Haverhill, MA, USA) was impregnated by 2% Pt with an aqueous solution of tetraamine platinum (II) nitrate (Alfa Aesar, Haverhill, MA, USA) followed by drying and calcination at 350 °C (four hours, muffle furnace). Then, the appropriate amount of KNO₃ (Alfa Aesar, Haverhill, MA, USA) or RbNO₃ (Alfa Aesar, Haverhill, MA, USA) was added via IWI. Promoted catalysts were dried and recalcined using the same conditions.

In-house supported Ru catalysts were prepared on activated carbon (Jacobi Carbons), α-Al₂O₃ (Alfa Aesar), rutile-TiO₂ (Norpro Saint-Gobain) and monoclinic-ZrO₂ (Norpro Saint-Gobain). The catalysts were synthesised by wet impregnation (4 h, 40 °C, continuous agitation) of the sieved supports (0.5–0.8 mm) with an aqueous 1.5% (wt/vol) RuNO(NO₃)₃ solution (Alfa Aesar). The suspension was then evaporated at 60 °C by progressively decreasing the pressure on a rotary evaporator. The catalysts were left at RT and 150 mbar overnight to fully evaporate the solvent. The impregnated supports were then dried overnight in an oven at 110 °C in air. The metal oxide-supported catalysts were calcined in a quartz tube at 450 °C (10 °C min⁻¹, 4 h) in N₂/O₂ (80 : 20, 250 mL min⁻¹). Eventually, all catalysts were reduced at 400 °C (5 °C min⁻¹, 6 h) in a flow of N₂/H₂ (80 : 20, 500 mL min⁻¹). After reduction, they were passivated by letting air diffuse through the open reactor. The catalysts obtained were used without further treatment. Three commercial catalysts – 5 wt% Ru supported on activated carbon, Ru/AC-BM (BASF), Ru/AC-A, and Ru/AC-B (both proprietary) – were also evaluated in this study. Ru/AC-BM is the benchmark catalyst used for gasification campaigns on PSI's cHTG demonstration unit.^6,53