The convenient green-route for the synthesis of Cr-free catalyst for low-carbon hydrogen production.

The synthesis of K-promoted ZnO/ZnAl 2 O 4 nanocomposite catalyst for high temperature water gas shift (HT-WGS) via novel eco-friendly route using CO 2 as key reagent has been studied. The sodium and nitrate-free precursors of the Zn–Al spinels (ZnO/ZnAl 2 O 4) were successfully prepared by saturation of ZnO–AlOOH aqueous suspension with CO 2 , followed by thermal treatment and potassium deposition. The effect of the calcination temperature of precursor on the acid-base and textural properties, surface morphology and activity of catalysts was investigated. Nanocomposites calcined at 500–600 °C displayed higher basicity and specific surface area than samples calcined at temperature above 600 °C. At the same time, the high and stable activity of K–ZnO/ZnAl 2 O 4 catalysts toward HT-WGS was revealed for the nanocomposite. The catalysts exhibit high and stable activity and their selectivity is significantly higher than that of conventional systems for HT-WGS. Both at higher steam-to-carbon and also at lower H 2 O/C molar ratios, no methane formation was observed under HT-WGS conditions in the presence of ZnAl_X_K catalysts. [Display omitted] • Simple and eco-friendly route of catalyst synthesis using CO 2 as key reagent. • Great effect of the calcination temperature of ZnO–ZnAl 2 O 4 on textural properties and surface morphology. • Catalyst activity depends on the calcination temperature of ZnO–ZnAl 2 O 4 nanocomposite. • Higher selectivity of novel HT-WGS catalyst at lower steam-to-carbon ratio. [ABSTRACT FROM AUTHOR]