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  • TPRS  (1)
  • active carbon support  (1)
  • 1
    ISSN: 1572-879X
    Keywords: Iridium catalyst ; supported catalyst ; vapor-phase carbonylation ; methanol carbonylation ; active carbon support
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Iridium on active carbon (Ir/A.C.) is an effective catalyst for the vapor-phase carbonylation of methanol. In contrast to rhodium-catalysts the reaction rate is nearly independent of the partial pressure of the methyl iodide promoter and the methanolysis of an iridium-acetyl species has been found to determine the rate. Undesired methane formation accompanying the carbonylation is suggested to proceed via proteolysis of iridium-methyl species by methanol or water. Methyl chloride has been found to be a less effective promoter than methyl iodide.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-9028
    Keywords: ammoxidation ; vanadium phosphate catalysts ; catalyst/feed interaction ; reaction mechanism ; FTIR spectroscopy ; TAP technique ; isotope experiments ; TPD ; TPRS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction pathway of the ammoxidation of toluene on (VO)2P2O7 used as catalyst and the interaction of potential intermediates with the pyrophosphate were studied by spectroscopic techniques (FTIR, EPR), temperature-programmed chemisorptions/ reactions (TPD, TPRS) and transient studies such as the temporal analysis of products (TAP) technique. NH3 is chemisorbed on the catalyst surface, forming three different species, i.e., NH 4 + ions located on BrØnsted sites, coordinatively bound NH3 on Lewis sites and NH 2 − groups, presumably P-NH2. Toluene that is probably adsorbed on Lewis sites reacts in a first step to a benzyl radical. A subsequent partial oxidation by interaction of VIV=O groups generates a V...O=CH-C6H5 surface structure. This benzaldehyde-like surface species reacts with adsorbed NH3 according to a Langmuir-Hinshelwood mechanism. TAP experiments on ammonium-containing vanadium phosphates revealed that NH 4 + ions could act as potential N-insertion species. No formation of benzylamine as well as the generation of V=NH surface groups as possible intermediates or N-insertion sites were observed.
    Type of Medium: Electronic Resource
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