Spectroscopic investigation of vanadium-phosphorus catalysts

Catalytic conversion of C4 hydrocarbons on vanadium-phosphorus oxides: factors influencing the selectivity in 1-butene oxidation

“…The diffuse reflectance spectra of the P:V 1.01 catalyst in the mentioned different conditions are reported in Figure 3. The bands at about 13000 and 16 000 cm'1 correspond to the d-d transitions of the V4+ ions in octahedral coordination as in V0S04*5H20 (Ballhausen, 1962), whereas the high-intensity charge-transfer band in the region 24 000-30 000 cm'1 is characteristic of the V5+ ions in octahedral coordination as in V205 (Hanke et al, 1975;Martini et al, 1978Martini et al, ,1982. The band at 20000 cm'1 can be attributed, according to King and Good (1973), to Vm ions.…”

“…fThis is a part of the paper presented at the Murphree Award Symposium (Industrial and Engineering Chemistry) Honoring Dr. Robert K. Grasselli, 187th National Meeting of the American Chemical Society, St Louis, MO, April 1984. The mechanism proposed for oxidation of 1-butene to maleic anhydride (Figure 1) requires several kinds of be-0196-4321/85/1224-0221 $01.50/0 © 1985 American Chemical Society havior to explain the product distribution (Morselli et al, 1979;Cavani et al, 1983a;Hofmann et al, 1984).…”

“…In the catalyst prepared in an aqueous medium, after the calcination stage, two crystalline phases are present, one of vanadium(V) (V0P04) and one of vanadium(IV) (vanadyl pyrophosphate) (Hodnett, 1983(Hodnett, ,1984Bordes and Courtine, 1979; Morselli et al, 1979). In previous papers (Poli et al, 1980(Poli et al, , 1981; Centi et al, 1983 and we have indicated that these two phases are in dynamic equilibrium in the reaction mixture (their relative ratio depending upon the reaction conditions) and are characterized by different catalytic behavior.…”

Mechanistic aspects of maleic anhydride synthesis from C4 hydrocarbons over phosphorus vanadium oxide

“…The data of Centi and Trifiro139,175 suggest that the same kind of oxygen species is involved in the two reactions and thus lattice oxygen also is used in the transformation of furan to maleic anhydride. Pulse reactor tests39, 40,116,120,124,127,129 clearly indicate that lattice oxygen may be sufficient for the synthesis of maleic anhydride from both butenes and butane. Results of Morselli et al,132 furthermore, suggest that on a pure vanadyl pyrophosphate phase only oxidative dehydrogenation occurs, whereas in the presence of Vv the transformation to maleic anhydride even in the absence of 02 may occur.…”

Selective oxidation of C4 hydrocarbons over (VO)2P2O7 catalyst: Nature of the redox mechanism

“…Many studies have correlated the catalytic performance of these catalysts with the preparation and activation techniques. These studies demonstrated the importance of P-to-V ratio [4][5][6][7][12][13][14][15][16][17][18][19][20], oxidation state [21][22][23][24][25][26][27], and structural characteristics [28][29][30][31][32][33][34]. More recently, investigations have focused on the detection of the possible intermediates in the reaction pathways, the role of different oxygen species, and the nature of the active sites involved in the redox mechanism.…”