Reaction pathway of benzonitrile formation during toluene ammoxidation on vanadium phosphate catalysts

Ammoxidation of toluene on vanadyl polyphosphates-VO(PO3)2, 2. Catalytic properties

“…Recently, we found by FTIR spectroscopy that benzaldehyde acts as an intermediate during benzonitrile formation from toluene on VPO catalysts [22]. Furthermore, temporal-analysisof-products (TAP) investigations of the interaction of an ammoxidation feed pulse with (VO)2PzO7 revealed the liberation of benzaldehyde as first reaction product [23]. Benzonitrile was only formed in the presence of activated ammonia by a consecutive reaction.…”

“…In contrast, the more active (VO)2P207 or (NH4)2(VO)3(P207)2 + r ' (AVPgen) contain close-neighbor octahedral sites (e.g. edge-shared vanadyl octahedra forming double chains) that will be needed to enable on the same site the adsorption of methylaromatics by n-bonding, the subsequent following partial oxidation that runs via aldehyde structures, the N-insertion step to form the nitrile and its desorption [22,23]. Furthermore, the structural integration of the activity-beating vanadyl sites in the polyphosphate framework does not seem to support an easy change of the valence state of surface vanadium sites [V(III) ~ V(IV) ~ V(V)], which should be necessary for the partial oxidation steps, running via a Mars-van Krevelen mechanism like in the ammoxidation case.…”

Catalytic Performance of Lanthanum Vanadate Catalysts in Ammoxidation of 2-Methylpyrazine

“…Besides CP, pyrazine (Py), pyrazinamide (PyA), CO and CO 2 were observed as by-products. Pyrazine formation is supposed to occur from the demethylation of MP that might happen as a consecutive step after methyl group activation; the hetero aromatic molecule is activated by hydride abstraction, leading to a methylene-like species as we found out recently by in situ-FTIR spectroscopy of the ammoxidation of toluene to benzonitrile [7,23]. Here, a benzaldehyde-like intermediate was formed which might react toward an imine in the presence of ammonia; the nitrile is formed afterwards by oxidative dehydration.…”

Kinetic studies and Mechanism Evolution of the Ammoxidation of 3-picoline Over V2O5/ZrO2 Catalyst

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1977) and V 2 O 5 /TiO 2 (Chary et al, 2000). There are reports on FTIR investigation of surface intermediates formed during the ammoxidation of toluene over vanadyl pyrophosphate (Zhang et al, 1997), ammoxidation of toluene on vanadium phosphate catalyst (Martin et al, 1996), and ammoxidation of 4-picoline over VAPO and SAPO catalysts (Kulkarni et al, 1996). Murkami et al (1981), Niwa and Murkami, (1982) studied ammoxidation of toluene over V 2 O 5 / Al 2 O 3 catalyst, and detected benzoate ions as surface species by infrared spectroscopy.ZrO 2 is employed in many industrially important reactions such as hydroprocessing, (Vrinat et al, 1994), oxidation of alcohols (Ross et al, 1994;Mattos et al, 2002), synthesis of methanol and higher alcohols (Slaa et al, 1991) and methanation reactions (Yamasaki et al, 1997).

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“…1977) and V 2 O 5 /TiO 2 (Chary et al, 2000). There are reports on FTIR investigation of surface intermediates formed during the ammoxidation of toluene over vanadyl pyrophosphate (Zhang et al, 1997), ammoxidation of toluene on vanadium phosphate catalyst (Martin et al, 1996), and ammoxidation of 4-picoline over VAPO and SAPO catalysts (Kulkarni et al, 1996). Murkami et al (1981), Niwa and Murkami, (1982) studied ammoxidation of toluene over V 2 O 5 / Al 2 O 3 catalyst, and detected benzoate ions as surface species by infrared spectroscopy.…”