A-site effects of titanate-perovskite (ATiO3)-based catalysts on dehydrogenation of N-heterocyclic molecules

Abstract

Dehydrogenation reactions in liquid organic hydrogen carrier (LOHC) systems present significant challenges, particularly when aiming for low-temperature operations while ensuring that no hydrogen remains in the substrate molecules. Enhancing catalytic performance requires modifying the adsorption behavior of the reactants and products during dehydrogenation. Perovskites have emerged as promising catalyst supports because of their ability to modify the surface chemical properties by manipulating the cations present at the A- and B- sites. This study investigated the effects of A-site cations (Ca, Sr, and Ba) in titanate-type perovskite (ATiO3)—a prototypical perovskite—on the dehydrogenation activity in LOHC systems. Remarkably, Pd/SrTiO3 exhibited outstanding performance by completely converting octahydro-N-methylindole to N-methylindole and releasing 5.76 wt% hydrogen over 8 h. Additionally, it dehydrogenated dodecahydro-N-ethylcarbazole to N-ethylcarbazole with a hydrogen release of 5.70 wt%. Furthermore, the catalyst demonstrated a stable performance after recycling tests for three times without degradation or loss of activity. The chemical state of the catalyst surface was characterized through X-ray photoelectron spectroscopy, H2-temperature programmed reduction, and chemisorption using NH3, CO2, and H2. The results revealed that the exceptional dehydrogenation activity of Pd/SrTiO3 is due to the presence of suitable surface oxygen vacancies and abundant acid–base sites.