Double oxalates of Rh(III) with Cu(II) and Zn(II) – Effective precursors of nanoalloys for hydrogen production by steam reforming of propane.

Heteronuclear coordination compounds of d-metals are effective precursors for the production of bimetallic nanoalloys (Plyusnin et al., 2022) [1], which, in turn, are widely used in catalysis. Catalysts based on Rh and Cu, as well as Rh and Zn, are highly active in the process of steam reforming of hydrocarbons. Double oxalates of Rh with Cu and Rh with Zn with the general formula [(C 2 O 4)(H 2 O) 2 Rh−(μ-C 2 O 4)−M(H 2 O) 2 −(μ-C 2 O 4)–Rh(H 2 O) 2 (C 2 O 4)]·6H 2 O (M = Cu, Zn) are synthesized and structurally characterized. According to thermogravimetric analysis, the complexes completely decompose in He and H 2 atmospheres already at 300 °C with the formation of the corresponding nanoalloys in the Cu–Rh and Zn–Rh systems. Calcination in an O 2 atmosphere leads to the formation of a mixed oxide with a spinel structure. The Cu–Rh/Ce 0.75 Zr 0.25 O 2 and Zn–Rh/Ce 0.75 Zr 0.25 O 2 catalysts were prepared by impregnation by moisture capacity on a porous support followed by calcination in a hydrogen atmosphere. The obtained catalysts were tested in propane steam reforming for hydrogen production at 300–480 °C and WHSV = 10 000–40 000 cm3 h−1∙g cat −1. At these conditions the Cu–Rh/Ce 0.75 Zr 0.25 O 2 and Zn–Rh/Ce 0.75 Zr 0.25 O 2 catalysts demonstrated high selectivity for hydrogen (more than 70 %) compared to the monometallic catalyst Rh/Ce 0.75 Zr 0.25 O 2 (less than 60%). Bimetallic catalysts make it possible to increase hydrogen productivity by reducing the reaction rate of methanation of carbon oxides, which is achieved due to the presence of Cu and Zn in the catalyst structure. • New coordination compounds of rhodium with copper and zinc have been synthesized. • Bimetallic systems were obtained in a reducing and inert atmosphere. • Bimetallic Cu–Rh/CZ catalysts exhibit high hydrogen selectivity in the propane steam reforming reaction. • Bimetallic Cu–Rh/CZ and Zn–Rh/CZ catalysts reduce the rate of methanation reaction during propane steam reforming. [ABSTRACT FROM AUTHOR]