Bimetallic Rh/Ir–Cu Metastable Nanoalloys as Promising Catalysts for Propane Prereforming

In the present work, we synthesized and characterized new complex compounds, [Rh(NH 3 ) 5 Cl][Cu(H 2 O)(C 2 O 4 ) 2 ], [Ir(NH 3 ) 5 Cl][Cu(H 2 O)(C 2 O 4 ) 2 ], and [Rh x Ir 1– x (NH 3 ) 6 ] 2 [Cu(H 2 O)(C 2 O 4 ) 2 ] 2 [Cu(H 2 O) 2 (C 2 O 4 ) 2 ]·2H 2 O ( x = 0, 0.25, 0.50, 0.75, 1). A detailed study of their thermal decomposition using ex situ and in situ PXRD allowed us to select the optimal conditions and synthesize a series of M x Cu 1– x (M = Rh, Ir) metastable nanoalloys. For the first time, single-phase metastable Ir 0.50 Cu 0.50 and Ir 0.40 Cu 0.60 nanoalloys were obtained. Nanoalloys were studied in the propane steam reforming reaction (prereforming) at WHSV = 4 000 mL·g cat –1 ·h –1, T = 300–500 °C, and p = 1 atm. The bimetallic Rh–Cu/Ce 0.75 Zr 0.25 O 2 supported catalysts demonstrated high activity as well as greater hydrogen selectivity compared to the monometallic Rh sample, resulting in higher hydrogen productivity. Higher hydrogen productivity is achieved due to higher dispersion of the active component in bimetallic catalysts and due to inhibition of carbon monoxide methanation reactions in the overall rate of the steam reforming process.