Brenig Andreas, Fischer Jörg W A, Klose Daniel, Jeschke Gunnar, van Bokhoven Jeroen A, Sushkevich Vitaly L
Institute for Chemical and Bioengineering, ETH Zurich, Vladimir-Prelog-Weg 1-5/10, 8093, Zurich, Switzerland.
Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, Forschungsstrasse 111, 5232, Villigen, Switzerland.
Angew Chem Int Ed Engl. 2024 Nov 4;63(45):e202411662. doi: 10.1002/anie.202411662. Epub 2024 Sep 12.
The CH oxidation performance of Cu-chabazite zeolites characterized by distinct Si/Al ratios and Cu loadings has been studied and the observed variations in reactivity have been correlated to the differences in the nature of the formed active centers. Plug flow reactor tests, in situ Fourier-transform infrared, and X-ray absorption spectroscopy demonstrate that a decrease in Cu loading shifts the reactivity/redox profile to higher temperatures and increases the CHOH selectivity and Cu-efficiency. In situ electron paramagnetic resonance, Raman, ultraviolet-visible, Fourier-transform infrared, and photoluminescence spectroscopies reveal that this behavior is associated with the presence of monomeric Cu active sites, including bare Cu and [CuOH] present at low Si/Al ratio and Cu loading. Formation of two distinct [Cu(μ-O)] moieties at higher Si/Al ratio or Cu loading forces these trends into the opposite direction. Operando electron paramagnetic resonance and ultraviolet-visible spectroscopy show that the apparent activation energy of monomeric Cu active species decreases with increasing Si/Al ratio, whereas the one of dimeric centers is unaffected.
研究了具有不同硅铝比和铜负载量的铜菱沸石的CH氧化性能，并将观察到的反应活性变化与所形成活性中心性质的差异相关联。活塞流反应器测试、原位傅里叶变换红外光谱和X射线吸收光谱表明，铜负载量的降低将反应活性/氧化还原曲线移向更高温度，并提高了CHOH选择性和铜效率。原位电子顺磁共振、拉曼光谱、紫外可见光谱、傅里叶变换红外光谱和光致发光光谱表明，这种行为与单体铜活性位点的存在有关，包括在低硅铝比和铜负载量下存在的裸铜和[CuOH]。在较高硅铝比或铜负载量下形成两种不同的[Cu(μ-O)]部分会使这些趋势走向相反方向。操作电子顺磁共振和紫外可见光谱表明，单体铜活性物种的表观活化能随硅铝比的增加而降低，而二聚体中心的表观活化能则不受影响。
