NiMn2O4 sphere catalyst for the selective catalytic reduction of NO by NH3: Insight into the enhanced activity via solvothermal method

Herein, NiMn2O4 sphere (NiMn2O4-S) and NiMn2O4 particle (NiMn2O4-P) were fabricated via solvothermal method and ammonia precipitation method followed by calcination, then the two samples were evaluated as potential candidate catalysts for low temperature NH3-SCR. Meanwhile, systematical characterizations were employed to establish the relationship between denitrification performance and physiochemical properties. Besides, in-situ DRIFTs and kinetics calculation were performed to reveal the reaction mechanism and the intrinsic catalytic activity. The results verified the preferable catalytic performance of NiMn2O4-S with higher than 90% NO conversion at the range of 85-285 degrees C, and nearly 100% N-2 selectivity at 120 degrees C. The fine catalytic activity might be related to the larger specific surface area, which could contribute to higher Mn4+/Mnn+ ratio, ampler O alpha, more suitable acid amounts and redox capacity. In-situ DRIFTs revealed that the NH3-SCR over NiMn2O4-S and NiMn2O4-P catalysts mainly preceded via Eley-Rideal (E-R) mechanism at 90 degrees C. The higher TOF values and lower Ea value for NiMn2O4-S catalyst further confirmed its excellent de-NOx performance. As compared to NiMn2O4-P catalysts, the hierarchical spherical morphology of NiMn2O4-S catalyst could generate even more abundant NH3/NOx adsorption sites, higher reactivity of NH4+ bounded to Bronsted acid sites (NH4+-BASs) and NH2 species which were conducive to the enhancement of low temperature activity.

Automated summary

The study evaluates NiMn2O4 sphere (NiMn2O4-S) and NiMn2O4 particle (NiMn2O4-P) as catalysts for low temperature NH3-SCR, demonstrating that NiMn2O4-S shows superior catalytic activity mainly through the Eley-Rideal mechanism, attributed to its larger specific surface area contributing to enhanced activity.