10.1016/j.cej.2010.05.016
Selective oxidation of p-cymene catalyzed by VPO catalyst: Process performance and kinetics studies
Three distinctive standard methods were used to prepare the VPO catalyst precursors phase, VOHPO4*0.5H2O [14]. In the first method, the precursor was prepared in an aqueous medium by dissolving V2O5 (6.0 g; 33 mmol) in aqueous HCl (35%, 79 mL) and refluxing for 2 h. The H3PO4 (85%; 8.9 g; 78 mmol) was added and the solution refluxed for further 2 h. The solution was subsequently evaporated to dryness and the resulting solid was refluxed in water (20 mL H2O g-1 solid) for 1 h. It was then filtered hot, washed with warm water, and dried in air (110 degC, 16 h). The precursor prepared by this method is denoted P1.In the second method, the precursor was prepared in an organic medium, by adding V2O5 (11.8 g; 66 mmol) to isobutanol (250 mL). H3PO4 (85%; 16.4 g; 39 mmol) was then introduced and the whole mixture was refluxed for 16 h. The light blue suspension was then separated from the organic solution by filtration and washed with isobutanol (200 mL) and ethanol (150 mL, 100%). The resulting solid was refluxed in water (9 mL g-1 solid), filtered hot, and dried in air (110 degC, 16 h). The precursor prepared by this method is denoted P2. The third method precursor was prepared via the dihydrate compound VOPO4*2H2O. A mixture V2O5 (11.8 g; 66 mmol) and H3PO4 (85%; 115.5 g; 106 mmol) were refluxed in water (24 mL g-1 solid) for 8 h. The resulting VOPO4*2H2O was recovered by filtration and washed with a little water. Some of the VOPO4*2H2O (4.0 g; 20 mmol) was subsequently refluxed with isobutanol (80 mL) for 21 h, and the resulting solid was recovered by filtration and dried in air (110 degC, 16 h). The precursor prepared by this method is denoted P3. The precursors (P1, P2 and P3) were activated under N2 flow in the tube furnace at 550 degC for 4 h. They are denoted C1, C2 and C3, respectively.
V2O5
dissolving
6.0 g
g
V2O5
dissolving
33 mmol
mmol
aqueous
HCl
35%
%
aqueous HCl
79 mL
mL
precursor
refluxing
2 h
h
H3PO4
85%
%
H3PO4
added
8.9 g
g
H3PO4
78 mmol
mmol
solution
refluxed
2 h
h
H2O g-1 solid
20 mL
mL
resulting solid
refluxed
1 h
h
It
dried
110 degC
degC
It
dried
16 h
h
V2O5
adding
11.8 g
g
V2O5
adding
66 mmol
mmol
isobutanol
250 mL
mL
H3PO4
introduced
85%
%
H3PO4
introduced
16.4 g
g
H3PO4
introduced
39 mmol
mmol
mixture
refluxed
16 h
h
isobutanol
200 mL
mL
ethanol
150 mL
mL
ethanol
100%
%
solid was refluxed in water
9 mL g-1
mL g-1
resulting solid
dried
110 degC
degC
resulting solid
dried
16 h
h
V2O5
refluxed
11.8 g
g
V2O5
refluxed
66 mmol
mmol
H3PO4
refluxed
85%
%
H3PO4
refluxed
115.5 g
g
H3PO4
refluxed
106 mmol
mmol
water
24 mL g-1
mL g-1
mixture
refluxed
8 h
h
isobutanol
80 mL
mL
resulting solid
dried
110 degC
degC
resulting solid
dried
16 h
h
VOPO4*2H2O
refluxed
21 h
h
VOPO4*2H2O
subsequently refluxed
4.0 g
g
VOPO4*2H2O
subsequently refluxed
20 mmol
mmol
precursors (P1, P2 and P3)
activated
550 degC
degC
precursors (P1, P2 and P3)
activated
4 h
h