Catalysis Science & Technology最新文献

Catalytic ammonia decomposition is a sustainable chemical route for hydrogen production. Transition metal nitrides have emerged as promising and effective catalysts for this reaction. In this study, we revisit the synthesis, crystal structure, optoelectronic properties, and catalytic performance of antifluorite-derived Li₇MnN₄. Phase-pure Li₇MnN₄ powder is synthesized from Li₃N and metallic Mn at 800 °C in a tantalum ampoule, resulting in a highly crystalline cubic phase with space group P4̄₃ n (no. 218), a lattice parameter of a = 9.5598(8) Å, and a unit cell volume of 873.66(14) ų. Rietveld refinement results show excellent residual factors (R _wp = 1.71, S = 1.38), confirming the ordered arrangement of [MnN₄]^7- tetrahedra and five symmetrically distinct Li sites. The experimental data are complemented by density functional theory calculations, revealing weak spin coupling consistent with a paramagnetic ground state. Strong absorption in the UV-visible region corresponds to an experimental optical band gap of ∼2.76 eV, while Raman and infrared spectra are dominated by MnN₄ tetrahedral vibrations. X-ray absorption spectroscopy indicates a high Mn oxidation state and a well-defined Mn-N/Li coordination. Catalytic tests show that Li₇MnN₄ and Li₇MnN₄ : LiNH₂ (1 : 1 molar ratio) exhibit activities comparable to a Ni-based reference catalyst, with apparent activation energies of 364.4 kJ mol^-1 and 256.0 kJ mol^-1, respectively, highlighting the beneficial effect of LiNH₂ incorporation. Thermogravimetry coupled with mass spectrometry identifies decomposition pathways involving LiNH₂/Li₂NH intermediates and forming Li₃N and manganese nitrides. These results demonstrate that Li₇MnN₄ is a catalytically promising nitride for ammonia decomposition, with potential for further optimization through compositional tuning and mechanistic insights.

Heterogeneous catalysts play a central role in numerous industrially and societally relevant processes. Despite the widespread use, a detailed understanding of the support mesoporosity and its transformation during catalyst preparation remains incomplete. In this study, cryogenic electron tomography (cryo-ET) was utilized to resolve the 3D mesopore structure of γ-Al₂O₃ and to assess structural changes induced by oxidic Mo and MoNiP deposition and sulfidation during the preparation of hydrodesulfurization (HDS) catalysts. The intrinsic γ-Al₂O₃ surface and mesopore structure remained largely stable throughout calcination and sulfidation, although cryo-ET revealed subtle variations inaccessible to bulk characterization techniques. Oxidic Mo deposition introduced slight increases in tortuosity and surface corrugation, whereas oxidic MoNiP deposition induced minimal changes. Compared to the bare support, sulfidation of both Mo and MoNiP supported on γ-Al₂O₃ resulted in more tortuous mesopores and a more corrugated surface. Careful segmentation enabled separate analysis of γ-Al₂O₃ and MoS₂ slabs, revealing that, for both catalysts, the γ-Al₂O₃ exhibited similar surface and mesopore modifications, and there were no significant differences in MoS₂ slab morphology. Corrected Mo loadings derived from cryo-ET aligned with bulk measurements, validating the approach. These findings provide a comprehensive 3D perspective on mesopore stability during catalyst preparation and highlight the need for higher-resolution imaging and advanced 3D analysis to establish robust structure-function correlations.

Correction for ‘Flow bioprocessing of citrus glycosides for high-value aglycone preparation’ by Agostina Colacicco et al., Catal. Sci. Technol., 2023, 13, 4348–4352, https://doi.org/10.1039/d3cy00603d.