Ruthenium catalyst supported on perovskite-type alkaline earth metal-titanates with strong metal-support interaction for ammonia decomposition

Abstract

Alkaline earth-metal titanates ATiO3 (A = Ca, Sr, and Ba) with a perovskite-type structure were used as supports for Ru-based catalysts to produce COx-free H2 via NH3 decomposition. The effects of alkaline-earth metals on the physicochemical characteristics and catalytic activities of Ru/ATiO3 for NH3 decomposition were investigated using various techniques. The order of Ru/ATiO3 for NH3 conversion is Ru/BaTiO3 > Ru/SrTiO3 > Ru/CaTiO3 > Ru/TiO2 at the identical conditions, with the Ru/BaTiO3 catalyst demonstrating the highest NH3 conversion of 77.8% at 450 °C and a gas hourly space velocity of 30,000 mL/gcat/h, which is 8.7, 2.1, and 1.3 times of that over Ru/TiO2, Ru/CaTiO3, and Ru/SrTiO3, respectively. The formation of the ATiO3 phase can enrich the concentration of basic sites and oxygen vacancies compared with TiO2, which can induce the presence of strong metal-support interaction (SMSI) through the formation of Ru–O–Ti bonds. This SMSI effect increased the dispersion and electron density of Ru nano-particles on ATiO3 supports, and the electron-rich Ru nano-particles could weaken the chemisorptive strength of N2 and H2 on the Ru/ATiO3 catalysts, thereby promoting the reaction rate for NH3 decomposition.