Tungsten isomerization

ISOMERIZATION OF FISCHER-TROPSCH PRODUCT The conditions for operating the tungsten isomerization catalyst are compatible with the composition of the exit stream from a Fischer-Tropsch reactor. The presence of unreacted hydrogen and water vapour together with CO and C02 provides an effective oxygen partial pressure equivalent to that required by the isomerization catalyst. 

Schmidt reaction of ketones, 7, 530 from thienylnitrenes, 4, 820 tautomers, 7, 492 thermal reactions, 7, 503 transition metal complexes reactivity, 7, 28 tungsten complexes, 7, 523 UV spectra, 7, 501 X-ray analysis, 7, 494 1 H-Azepines conformation, 7, 492 cycloaddition reactions, 7, 520, 522 dimerization, 7, 508 H NMR, 7, 495 isomerization, 7, 519 metal complexes, 7, 512 photoaddition reactions with oxygen, 7, 523 protonation, 7, 509 ring contractions, 7, 506 sigmatropic rearrangements, 7, 506 stability, 7, 492 N-substituted mass spectra, 7, 501 rearrangements, 7, 504 synthesis, 7, 536-537... 

Selective Isomerization of Alkanes on Supported Tungsten Oxide Acids... 

In another study the kinetics and mechanism of an unprecedented T/2-vinyl isomerization of a highly fluorinated tungsten(II) metalla-cyclopropene complex was studied (92). Photolysis of a tungsten(II) tetrafluoroaryl metallacycle 1 and perfluoro-2-butyne results in the formation of the kinetic rf -vinyl complex 2 in which the fluoride is trans to the inserted acetylene and cis to both carbonyl ligands. Upon heating 2 is converted to the thermodynamic rf -vinyl complex 3 in which the fluoride ligand is now cis to the inserted alkyne and trans to one CO and cis to the second CO ligand as shown in Scheme 1. 

With a tungsten pentacarbonyl catalyst, the calculated mechanisms are summarized in Scheme 4.15 [26]. Coordination of the 4-pentyn-l-ol substrate to the pentacarbonyl tungsten leads to the formation of the 7i-alkyne-W(CO)5 adduct Wl. This coordination process was calculated to be exothermic by 24.3 kcal mol. The cydoisomerization leading to a five-membered-ring exo product starts with the 7i-complex Wl via a one-step process with a barrier of 46.5 kcal mol (path a of Scheme 4.15). The barrier calculated here is comparable with that calculated for the catalyst-free process. From Wl to W3, the tungsten metal center does not play a significant role in the isomerization process. 

Synthesis and catalytic properties of tungsten carbide for isomerization, reforming and hydrogenation... 

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