Theoretical Approach toward a Mild Condition Haber–Bosch Process on the Zeolite Catalyst with Confined Dual Active Sites
Chunli Liu, Gaomou Xu, Tao Wang
Abstract
High Resolution Image Download MS PowerPoint Slide The Haber–Bosch (H–B) process is today’s dominant technology for ammonia production, but achieving a mild reaction condition is still challenging. Herein, we combined density functional theory (DFT) calculations and microkinetic modeling (MKM) to demonstrate the feasibility of conducting the H–B process under ambient conditions on a zeolite catalyst with confined dual active sites. Our designed dual Mo(II) cation-anchored ferrierite [2Mo (II) -FER] catalyst shows an energy barrier of only 0.58 eV for N≡N bond breaking due to the enhanced π-back-donation. Meanwhile, the three hydrogen sources (BH, FMH, and NMH) within 2Mo (II) -FER greatly enrich the hydrogenation mechanisms of NH x species, resulting in barriers of <1.1 eV for NH x ( x = 0–2) hydrogenations. This dual-site catalyst properly decouples the N 2 dissociation and NH x hydrogenation steps, which elegantly circumvents the linear scaling relation between the N 2 dissociation barrier and the nitrogen binding energy. It is worth noting that our MKM results show 4 orders of magnitude higher reaction rates on 2Mo (II) -FER than the stepped sites of the FCC Ru catalyst at low temperatures, paving a solid basis to conduct the H–B process at low temperatures. We believe that our strategy will provide crucial guidance for synthesizing state-of-the-art zeolite catalysts to achieve the near-ambient condition H–B process and other chemical reactions in heterogeneous catalysis.