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Item-typ:Veröffentlichung, Electron-induced hydroamination of ethane as compared to ethene: implications for the reaction mechanism(Royal Society of Chemistry, 2023-12-15); ; ; The properties of carbonaceous materials with respect to various applications are enhanced by incorporation of nitrogen-containing moieties like, for instance, amino groups. Therefore, processes that allow the introduction of such functional groups into hydrocarbon compounds are of utmost interest. Previous studies have demonstrated that hydroamination reactions which couple amines to unsaturated sites within hydrocarbon molecules do not only proceed in the presence of suitably tailored catalysts but can also be induced and controlled by electron irradiation. However, studies on electron-induced hydroaminations so far were guided by the hypothesis that unsaturated hydrocarbons are required for the reaction while the reaction would be much less efficient in the case of saturated hydrocarbons. The present work evaluates the validity of this hypothesis by post-irradiation thermal desorption experiments that monitor the electron energy-dependent yield of ethylamine after electron irradiation of mixed C2H4:NH3 and C2H6:NH3 ices with the same composition and thickness. The results reveal that, in contrast to the initial assumption, ethylamine is formed with similar efficiency in both mixed ices. From the dependence of the product yields on the electron energy, we conclude that the reaction in both cases is predominantly driven by electron ionization of NH3. Ethylamine is formed via alternative reaction mechanisms by which the resulting NH2˙ radicals add to C2H4 and C2H6, respectively. The similar efficiency of amine formation in unsaturated and saturated hydrocarbons demonstrates that electron irradiation in the presence of NH3 is a more versatile tool for introducing nitrogen into carbonaceous materials than previously anticipated.Wissenschaftlicher ArtikelBand:26Heft:365 60 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Water adsorption in SAPO-34: elucidating the role of local heterogeneities and defects using dispersion-corrected DFT calculationsThe chabazite-type silicoaluminophosphate SAPO-34 is a promising adsorbent for applications in thermal energy storage using water adsorption–desorption cycles. In order to develop a microscopic understanding of the impact of local heterogeneities and defects on the water adsorption properties{,} the interaction of different models of SAPO-34 with water was studied using dispersion-corrected density-functional theory (DFT-D) calculations. In addition to SAPO-34 with isolated silicon atoms{,} the calculations considered models incorporating two types of heterogeneities (silicon islands{,} aluminosilicate domains){,} and two defect-containing (partially and fully desilicated) systems. DFT-D optimisations were performed for systems with small amounts of adsorbed water{,} in which all H2O molecules can interact with framework protons{,} and systems with large amounts of adsorbed water (30 H2O molecules per unit cell). At low loadings{,} the host–guest interaction energy calculated for SAPO-34 with isolated Si atoms amounts to approximately −90 kJ mol−1. While the presence of local heterogeneities leads to the creation of some adsorption sites that are energetically slightly more favourable{,} the interaction strength is drastically reduced in systems with defects. At high water loadings{,} energies in the range of −70 kJ mol−1 are obtained for all models. The DFT-D interaction energies are in good agreement with experimentally measured heats of water adsorption. A detailed analysis of the equilibrium structures was used to gain insights into the binding modes at low coverages{,} and to assess the extent of framework deprotonation and changes in the coordination environment of aluminium atoms at high water loadings.Wissenschaftlicher ArtikelBand:17Heft:38108 152