Symmetry and Topology: The 11 Uninodal Planar Nets Revisited

A description of the 11 well-known uninodal planar nets is given by Cayley color graphs or alternative Cayley color graphs of plane groups. By applying methods from topological graph theory, the nets are derived from the bouquet B n with rotations mostly as voltages. It thus appears that translation, as a symmetry operation in these nets, is no more fundamental than rotations

Charge distribution as a tool to investigate structural details. III. Extension to description in terms of anion-centred polyhedra

International audienceThe charge distribution (CHARDI) method is a self-consistent generalization of Pauling's concept of bond strength which does not make use of empirical parameters but exploits the experimental geometry of the coordination polyhedra building a crystal structure. In the two previous articles of this series [Nespolo et al. (1999). Acta Cryst. B55, 902-916; Nespolo et al. (2001). Acta Cryst. B57, 652-664], we have presented the features and advantages of this approach and its extension to distorted and heterovalent polyhedra and to hydrogen bonds. In this third article we generalize CHARDI to structures based on anion-centred polyhedra, which have drawn attention in recent years, and we show that computations based on both descriptions can be useful to obtain a deeper insight into the structural details, in particular for mixed-valence compounds where CHARDI is able to give precise indications on the statistical distribution of atoms with different oxidation number. A graph-theoretical description of the structures rationalizes and gives further support to the conclusions obtained via the CHARDI approach

Oxidative dehydrogenation of propane under steady-state and transient regimes over alumina-supported isopolyanionic catalysts

International audienc

Mixed NiMo, NiW and NiMoW sulfides obtained from layered double hydroxides as catalysts in simultaneous HDA and HDS reactions

NiMoAl, NiWAl and NiMoWAl hydrotreating catalysts were prepared from NiAl- terephthalate layered double hydroxides (LDHs), by ion exchange of the therephthalate anion by heptamolybdate (Mo7O246-) and/or metatungstate (H2W12O406-). The Mo- and/or W-containing LDHs were sulfided, either by direct sulfidation (DS route) or after previous calcination (PC route).296187196CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQ460424/2014-925. Iberoamerican Congress on Catalysis2016-09-18Montevideo, Urugua