Perovskites as Precursors for Ni/La2O3 Catalysts in the Dry Reforming of Methane: Synthesis by Constant pH Co‐Precipitation,Reduction Mechanism and Effect of Ru‐Doping

LaNiO₃ perovskite is an interesting precursor for Ni/La₂O₃ catalysts for the dry reforming of methane at high temperatures. Precursors have been synthesized by co‐precipitation without, with 2.5 at %, and with 5 at % Ru doping. The presence of Ru leads to a stabilization of the perovskite structure and hinders the decomposition into NiO and Ruddlesden‐Popper mixed oxides La_n+1Ni_nO_3n+1, which was observed for the Ru‐free sample upon calcination at 1000 °C (n = 3). Upon reduction in hydrogen, a mechanism involving at least two steps was observed and the first major step was identified as the partial reduction of the precursor leading to a LaNiO_2.5‐like intermediate. The second major step is the reduction to Ni metal supported on La₂O₃ independent of the Ru content of the catalyst. In the presence of Ru, indications for Ni‐Ru alloy formation and for a higher dispersion of the metallic phase were found. The catalytic activity in DRM of the catalyst containing 2.5 % Ru was superior to the catalysts with more or without Ru. Furthermore, the propensity of coke formation was reduced by the presence of Ru.     

Flow synthesis of tricyclic spiropiperidines as building blocks for the histrionicotoxin family of alkaloids

A domino cyclization reaction of the bis-unsaturated ketone 3 with hydroxylamine proceeds with good yield and high stereoselectivity, in a flow reactor system. The tricyclic spiropiperidine products 5 and 2 obtained are valuable building blocks for the synthesis of analogues of the histrionicotoxin alkaloids.     

Disarming Clostridium difficile

In this issue, Puriet al. (2010) present inhibitors that prevent the autocatalytic activation of the clostridial toxin TcdB in vivo. Their approach is likely to provide guidance for the development of novel drugs targeting virulence factors and thereby rendering bacterial pathogens innocuous.     

A Visible Light Photocatalytic Cross‐Dehydrogenative Coupling/Dehydrogenation/6π‐Cyclization/Oxidation Cascade: Synthesis of 12‐Nitroindoloisoquinolines from 2‐Aryltetrahydroisoquinolines

A visible light‐induced photocatalytic dehydrogenation/6π‐cyclization/oxidation cascade converts 1‐(nitromethyl)‐2‐aryl‐1,2,3,4‐tetrahydroisoquinolines into novel 12‐nitro‐substituted tetracyclic indolo[2,1‐a]isoquinoline derivatives. Various photocatalysts promote the reaction in the presence of air and a base, the most efficient being 1‐aminoanthraquinone in combination with K₃PO₄. Further, the 12‐nitroindoloisoquinoline products can be accessed directly from C1‐unfunctionalized 2‐aryl‐1,2,3,4‐tetrahydroisoquinolines by extending the one‐pot protocol with a foregoing photocatalytic cross‐dehydrogenative coupling reaction, resulting in a quadruple cascade transformation.     

Continuum modeling of the swelling behavior of concrete when modified through superabsorbent polymers

The main purpose of our investigation is to model the physical solidification process of a concrete mixture, involving water absorbing constituents, i. e. Superabsorbent Polymers (SAP). In order to model the chemo-mechanical swelling process, the system is described within the framework of the Theory of Porous Media (TPM). The swelling process is accounted for by including mass exchange terms between free and absorbed water. The chemo-mechanical driving forces are deduced from non-equilibrium thermodynamics while constitutive relations are motivated by appropriate micro-models of the swelling process. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)