Efficient heterogeneous dual catalyst systems for alkane metathesis
A fully heterogeneous and highly efficient dual catalyst system for alkane metathesis (AM) has been developed. The system is comprised of an alumina-supported iridium pincer catalyst for alkane dehydrogenation/olefin hydrogenation and a second heterogeneous olefin metathesis catalyst. The iridium catalysts bear basic functional groups on the aromatic backbone of the pincer ligand and are strongly adsorbed on Lewis acid sites on alumina. The heterogeneous systems exhibit higher lifetimes and productivities relative to the corresponding homogeneous systems as catalyst/catalyst interactions and bimolecular decomposition reactions are inhibited. Additionally, using a two-pot device, the supported Ir catalysts and metathesis catalysts can be physically separated and run at different temperatures. This system with isolated catalysts shows very high turnover numbers and is selective for the formation of high molecular weight alkanes.
Huang, Zheng,Rolfe, Eleanor,Carson, Emily C.,Brookhart, Maurice,Goldman, Alan S,El-Khalafy, Sahar H.,Roy MacArthur, Amy H.
experimental part
p. 125 - 135
(2010/06/20)
Temperatures and enthalpies of solid-solid and melting transitions of the odd-numbered n-alkanes C21, C23, C25, C27, and C29
Very high purity samples of normal pentacosane and heptacosane are made by synthesis: the procedures for the C25 and C27 synthesis and the original conditions of their purification, particularly using the extraction by supercritical carbon dioxide, are described. Measurements of temperatures and enthalpies of the solid-solid transitions and of the melting transition were carried out by differential scanning calorimetry on the C25 and C27 synthetic samples and the odd-numbered homologous n-alkanes (from C21 to C29). The results show the importance of the effect of the impurities, particularly for the δ and γ crystal-crystal transition temperatures of C25 and C27. Several current data of the literature are also shown concerning the temperatures and the enthalpies of solid-solid and melting transitions of these five n-alkanes.
Chevallier, Virginie,Bouroukba, Mohammed,Petitjean, Dominique,Barth, Danielle,Dupuis, Paul,Dirand, Michel