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  • 1
    ISSN: 1572-879X
    Keywords: Alkali zeolites ; acid zeolites ; proton exchange ; phase selectivity ; methylated amines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract T-zeolites with different H+-exchange degrees (0, 44, 68 and 89%) were used for the amination of dimethyl ether in the temperature range of 603 to 703 K. On a Na, K-T-zeolite sample (synthesis form) at low dimethyl ether conversion high selectivities of lower methylated amines were observed and methanol was formed as by-product. By proton exchange the conversion could be enlarged, but the selectivity distribution was shifted to trimethylamine.
    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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