A cyclic catalytic process for co-production of ammonia and hydrogen from nitrogen and methane

The traditional ammonia synthesis via the Haber–Bosch process requires large consumption of high-purity H2 and causes significant carbon emissions owing to the energy-intensive and complex hydrogen production steps conducted under harsh reaction conditions. Herein, we report a cyclic catalytic process for the production of NH3 by directly utilizing earth-abundant CH4 as a hydrogen source for N2 hydrogenation while simultaneously co-producing H2 over an alumina-supported iron catalyst (Fe/Al2O3). It achieves exceptional productivities of 2300 μmol g−1 h−1 for NH3 and 400 mmol g−1 h−1 for H2 at 700 °C. By eliminating the coke that results from CH4 pyrolysis through a reaction with the greenhouse gas CO2 to produce valuable CO, we establish an atom-economic cyclic catalytic process while producing a CO stream intrinsically separated in the regeneration step. Mechanistic investigations indicate that the iron species in Fe/Al2O3 serve as tri-functional active sites for CH4 pyrolysis, N2 hydrogenation, and coke elimination to produce CO, thus enabling an efficient and environmentally friendly cyclic catalytic process.