Graphical Schematic diagram of the dominant mechanism of NH 3 -SCR reaction on CeCu/MCM-49 catalyst before and after poisoning. The L−H mechanism was dominant before poisoning. However, after alkali metal poisoning, NO x adsorption on the catalyst is inhibited, so the E−R mechanism dominates. NO x is a common atmospheric pollutant, and NH 3 -SCR technology efficiently purifies it. CeCuO x binary-oxide nanoparticles were synthesized and loaded onto acid MCM-49 molecular sieve with a large specific surface area to increase acid sites and disperse active sites of the catalyst. The optimized 35 % CeCu/MCM-49 catalyst effectively purified over 80 % of NO x in the temperature range of 200–500 °C and demonstrated excellent resistance to alkali metals, such as K, Na, and Ca. Even after K poisoning, it still removed over 80 % of NO x in the range of 200–450 °C. Various characterization methods, including XRD, FT-IR, TEM, and N 2 isotherm adsorption-desorption tests, confirmed the structure of the catalyst remained intact after poisoning with no substance change, nor agglomeration of nanoparticles. NH 3 -TPD and H 2 -TPR confirmed that the catalyst had effective acidity and redox capacity that were not affected by alkali metals. In-situ DRIFTs showed that the catalytic reaction predominant mechanism shifted from L−H to E−R mechanism after poisoning. This study provides valuable insights into the development of high-performance Ce-based NH 3 -SCR catalysts with alkali metal resistance.
Wen-Xuan Jia,Ming-Ming Tao,Xin-Yu Wang,Yan-Feng Huang,Ying Li
To address the limitations of natural enzymes, more and more artificial enzymes have been developed. As the most appropriate candidate, metal organic frameworks (MOFs) and MOFs-based derivatives have generated extensive interest due to their remarkable properties and potential applications in enzymes mimicry. In this work, Ce/Cu mixed metal oxides-carbon composite (CeCuO x /C) was synthesized through a simple oxidation method with bimetallic MOFs CeCu-BTC as precursors. It was found that the prepared CeCuO x /C possess four different enzyme-like activities, including peroxidase, oxidase, laccase and phosphatase mimetic activities. The kinetics parameters and potential influence factors of enzyme-like activities were studied and CeCuO x /C exhibited high catalytic activity, excellent stability, and reusability. Additionally, a cysteine detecting method was established via oxidase-like activity of CeCuO x /C. The linear response to the cysteine was in the range of 50 to 900 μM, and the limit of detection was 3.24 μM. The spiking recoveries were in the range 93.5–100.2 % for cysteine in artificial human urine samples and the relative standard deviations were found within the ranges of 1.2–2.9 %. This work presents a new approach for the design of multi-enzyme mimics and develops the potential of CeCuO x /C for biological sensing.
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