NH3 not only the key chemical raw material for industry but also a carbon-free fuel and mobile carrier of renewable energy in the future. Currently, the industrial NH3 The synthesis is still dominated by the traditional Haber-Bosch reaction, which requires a high temperature of 300-500 ºC and a pressure of 200-300 atm.
To overcome these shortcomings, Nanba et al. designed NO-CO-H2Or reaction system. In this reaction, NO is used as raw material and reduced to NH3 by H2O and poisonous gases CO. The reaction equation is as follows: NO + 2.5CO + 1.5H2OR → SMALL3 + 2.5CO2 (ΔH298.15K= -414.86 kJ·mol-1)
Recently, their research found that NO-CO-H2The O reaction can be roughly decomposed into a series of WGSR reactions with CO-H2O and reduced NO-H2. The results were published in Chinese Journal of Catalysis.
When the incident photon frequency of the incident light matches the vibration frequency of the noble metal nanoparticle, the nanoparticle has a strong absorption of photon energy and local surface plasmon resonance (LSPR) occurs. The metal with the LSPR effect can excite high-energy hot electrons and holes, which help to activate the reactants, thereby reducing the reaction energy and increasing the reaction rate. As a unique non-noble metal with LSPR effect, Cu is widely used in CO hydrogenation reactions.
Cu/CeO2 prepared by a simple wet impregnation method and the reactivity of NO reduction with NH3 by CO in a photothermal synergistic system was studied. As expected, high activity was obtained with Cu/CeO2 under visible light irradiation. The LSPR effect of Cu nanoparticles can increase NH3 yields under mild conditions.
Recently, a research team led by Prof. Wenxin Dai from Fuzhou University, China, reports a photothermal catalytic system consisting of Cu/CeO2 which is used in the reaction between NO, CO and H2Or for NH production3 under visible-light irradiation. High NO conversion (94.4%) and NH3 Selectivity (66.5%) was achieved with Cu/CeO2 in the presence of H2Or at 210°C. Visible light further improved the conversion of NO (97.7%) and selectivity for NH3 (69.1%).
Quasi-situ EPR and in-situ DRIFTS results show that CO initially reacts with H2Or to form an HCO3* intermediate, which then decomposes to CO2 and activated H*. Finally, NO reacts with activated H* to make NH3. The localized surface plasmon resonance effect of Cu nanoparticles induced by visible light promotes the decomposition of HCO3* is WHAT2 and H*while changing oxygen vacancies (OVs, H2Or activation sites) of CeO2 sites, resulting in enhanced NH3 production.
Xinjie Song et al, NH3 synthesis by visible-light-assisted thermocatalytic NO reduction of CO in the presence of H2O in Cu/CeO2, Chinese Journal of Catalysis (2023). DOI: 10.1016/S1872-2067(23)64439-0
Awarded by the Chinese Academy of Sciences
Citation: Scientists overcome shortcomings of NH3 synthesis (2023, July 19) retrieved on 19 July 2023 from https://phys.org/news/2023-07-scientists-nh3-synthesis-shortcomings.html
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