For highly exothermic catalytic reactions particular measures have to be taken for obtaining reliable kinetic and mechanistic information, which has been preferably determined under the prevalence of isothermicity, and which is not disguised by transport processes. If this is true such kinetics can be reliably extrapolated to conditions outside the frame of experimental conditions. To this end various reactor set-ups are presented and their operation is illustrated by some case studies. The temperature-scanning reactor, which is not inherently isothermal, is included since non-isothermicity is not an obstacle to easy kinetic data assessment. Its performance is clarified by estimating kinetic parameters for the ammonia synthesis at elevated pressure using a commercial catalyst. Two types of novel micro-structured reactors are presented which have been applied for two highly exothermic catalytic reactions, i.e., the oxidative dehydrogenation of propane (ODP) and the ammonia oxidation to N2, N2O and NO. These studies served the purpose of getting mechanistic insights into the reaction mechanisms of both reactions, to validate a kinetic scheme for the ODP reaction and to derive the estimates of the respective kinetic parameters. Finally, a reactor for transient experiments in the peak pressure range of 1 to 10 Pa has been used for studying reaction steps related to the catalytic ammonia oxidation under isothermal conditions. Isothermal studies are possible due to the low concentrations of reactants by which any undesired hot spots on the catalyst surface were suppressed. The instrumental arsenal described is an asset for both fundamental as well as applied work in studying exothermic catalytic reactions.
Sulfonamides Q 0560Green and Efficient Synthesis of Sulfonamides Catalyzed by Nano-Ru/Fe3O4. -A novel, environmentally benign method for the direct coupling of sulfonamides and alcohols is based on a domino dehydrogenation-condensation-hydrogenation sequence and is realized in the presence of a nanostructured catalyst. The magnetic property allows convenient isolation of the product and efficient recycling of the catalyst. An advantage is that only one equivalent of the primary alcohol is consumed in the process. -(SHI, F.; TSE, M. K.; ZHOU, S.; POHL, M.-M.; RADNIK, J.; HUEBNER, S.; JAEHNISCH, K.; BRUECKNER, A.; BELLER*, M.; J.
ChemInform Abstract The reactions between the 3,4,5-trichlorofuranone (I) and NaN3 (II) afford the 4-azido derivative (III) or the 4,5-bisazido derivative (IV) depending on the molar ratios of the reactants. On heating or on irradiation compound (IV) generates chlorocyanoketene. This is trapped by benzanilide (V) to afford the β-lactam (VI) or the pyrimidinone (VII), depending on the mode of generation of the ketene. Treatment of the 3-aroxyfuranones (VIII) with NaN3 (II) yields the 5-azido derivatives (IX) or the 4,5-bisazido derivatives (X) epending on the molar ratios of the reactants. Attempts to convert the unstable bisazido derivatives (X) into aryloxycyanoketenes by heating or irradiation remain unsuccessful.
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