Highly efficient hydrogenation of NO to NH3 via a Fe2O3/TiO2 catalyst

Abstract

Nitrogen oxides (NO_x) present in flue gas are economically renewable N1 resources. Unlike traditional selective catalytic reduction processes that convert NO into N₂, redirecting NO towards the synthesis of value-added NH₃ offers significant practical benefits. In this study, a Ti-based metal-organic framework (Ti-MOF), specifically MIL-125, was utilized as a support for Fe, which was subsequently calcined at 400 °C to produce a Fe₂O₃/TiO₂-MOF catalyst. The resulting catalyst demonstrated exceptional performance, achieving 99% NO conversion and 95% NH₃ selectivity under optimal conditions of 450 °C, 0.1 MPa, and a gas hourly space velocity of 38000 mL g^–1 h⁻¹. Additionally, the catalyst exhibited excellent stability and resistance to water and sulfur. The high efficiency of Fe₂O₃/TiO₂-MOF is attributed to the abundance of Fe²⁺ sites at the reaction temperature, which enhances NO adsorption and activation. Furthermore, density functional theory calculations suggest that NO undergoes hydrogenation at the N-terminus on the Fe₂O₃/TiO₂-MOF surface, leading directly to NH₃ synthesis rather than dissociation followed by hydrogenation. This catalyst presents a novel approach for converting NO_x into high-value chemical products.