Old and New Ideas for VPO?
Application to DuPont Catalysts
Elisabeth BORDES-RICHARD
Laboratoire de Catalyse de Lille
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
DuPont VPO Catalysts
 VPO cats for n-butane to maleic anhydride:
Especially designed by DuPont to be operated in
the CFBR (Circulating Fluid Bed Reactor)
 CFBR:
Different from usual fixed or fluidized bed
reactors:
 Riser: transported bed of powder cat (lean phase)
 Regenerator: fluidized bed of powder cat
 In between: pipes and slide valves, cyclone(s), heat
exchangers, etc.
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
CFBR
 Characteristics
[1,2]
Riser:
 nearly plug flow
 high heat & mass transfers
Transient cyclic state
==> improve performance
Controlled and separated
delivery:
 of O2- from solid to
molecule: oxocapacity
 of gaseous O2 to solid
Solid flux > 50 kg.m-2s-1
Superficial gas velocity > 2 ms-1
Residence time: few seconds
[1] R.M. Contractor et al. Catal.Today, 1 (1987) 49 etc
[2] G. Patience et al. Trans.I.ChemE, 68 (1990) 301 etc
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
DuPont VPO Catalyst
 Composition: V,P,O,Si
 Silica matrix embedding catalyst particles: attrition and
erosion resistant [3]
[3] R.M. Contractor et al.,
Fluidization VI,
Engineering Foundation
New-York,
1989; pp. 589-596
SEM on used cat; EDX: V, P, Si, Fe (LCL)
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
DuPont VPO Catalyst
DuPont recipe
(R.M. Contractor et al.)
V2O5/isobutyl/benzyl alcohols
+ H3PO4 (85%) + TEOS
P/V = 1.0x/1.0
Spray-drying of VPO(Si) precursor
with silicic acid (ca. 1Owt%)
 microspheres ø = 60-100 mm
Calcination 400°C
 Catalyst
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
DuPont VPO Catalyst
 Precursor:
VOHPO4•0.5H2O
Johnson et al., Torardi et al., 1984
Face-sharing octahedra
Layered structure,
 Catalyst: (VO)2P2O7
(mean oxidation state: V4.0x+)
Gorbunova 1978, Sleight et al. 1990
Edge-sharing octahedra
Layered structure,
Topotactic
dehydration,
[5] primary particles,
 Platy primary particles, pseudomorphism
 Platy
rosets as secondary particles
rosets as secondary particles
Control of VOHPO4•0.5H2O
==> Control of (VO)2P2O7
 Oxidation of prec. (air, 400°C)
 d-VOPO4 [4]
 Oxidation of cat. (air, 400°C)
 d-VOPO4 [4]
[4] E. Bordes, unpublished results
[5] E. Bordes et al., J.Solid State Chem. (1984); Torardi et al., Inorg. Chem. (1984)
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
CFBR
 Redox decoupling: optimize the working conditions <==> Same
particle alternatively reduced (riser) and oxidized (regenerator)
Co-feed
O2
C4
MA
O2-
C4
O2-
MA
CFBR
n-C4
MA
2O2- O2- O
O2-
O2
2O2- O2- O O2-
Oxocapacity: O2- delivery vs. MA prod.
E. Bordes and R.M. Contractor, Topics Catal., 3 (1996) 365.
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
CFBR (foll.)
(slightly) different properties of VPO catalyst
P/V ratio
Fixed B.
Fluidized B.
CFBR
1.1
1.1
1.0
Texture
Other phases
Attrition-resistant
a,b-VOPO4
d-VOPO4
"bulky" (VO)2P207
layered (VO)2P207
(100)
O2
E. Bordes et al., Catal. Lett. 1999
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
Experiments
Keypoints: Oxocapacity, reactivity
 Benchmarking
 Precursor/Catalyst: Oxocapacity
 Precursor dehydration and activation: genesis and control of
morphology (topotaxy), V oxidation state, P/V,....
 Influence of pO2 during dehydration on the resulting
phase(s), P/V, oxidation states, morphology, acidity…
 Catalytic experiments with in situ or ex situ activation
 Ageing of fresh cat and comparison with used cat
 Catalytic experiments using different reactors
 Comparison of properties with home VPO cats
 Etc.!
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
 Acknowledgements
 DuPont, G. Patience
 L. Gengembre, M. Lefrère, L. Burylo, N.
Bouremma: XPS, XRD, SEM-EDX
 G. Franceschini, A. Thomazic (undergraduate
students)
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
XRD
 Identification
 Precursor: usual pattern of layered VOHPO4.0.5H2O
 Catalyst
024
200
b-VOPO4
032
Fresh cat: (VO)2P2O7
Used cat: (VO)2P2O7 + b-VOPO4,
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
Laser Raman Spectroscopy
 Fresh and used cats
 Fresh:
• (VO)2P2O7 (9/10 particles): 929 (+ 1129, 1180) cm-1
• d-VOPO4 (1/10): 931, 1013, 1074 cm-1
 Used: heterogeneous mixture
• (VO)2P2O7 (6/10 particles): 931 (+ 1128, 1180) cm-1
• b-VOPO4 (3/10): 884, 987, 1060 cm-1
• and aII-VOPO4 (1/10): 938, 990, 1087 cm-1
J.C. Volta et al., G.L. Schrader et al.
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
In situ Redox XRD
 In situ reactivity of fresh and used cats
 Reduction by H2/He (1 h at 300, 400, 500°C) followed by
reoxidation in air (1 h 500°C)
b-VOPO4
Fresh cat: (VO)2P2O7
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
Used cat: (VO)2P2O7 + b-VOPO4
XPS (fresh and used cats)
 As is and after grinding
 Systematic higher V/Si when ground
 P/V = 1.8-1.9
 After redox pre-treatment with ethane (20 mn at 200,
300, 400°C and air at 400°C)
 Reduction steps
• Very little modification of V2p3/2 photopeak
• P/V = 1.80 up to 300°C;  1.92 at 400°C
• V/Si = 1.19  1.07 for fresh; 0.87  0.81 for used cat.
 Reoxidation
• V5+ + V4+ for fresh cat.; V5+ for used cat
• P/V = 1.8-1.9
• V/Si = 1.14 for fresh; 0.92 for used cat.
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
XPS (fresh and used cats)
 XPS
 As received and ground samples:  no difference
 P/V  1.80 up to 400°C; 1.91 at 500°C
Fresh
Used
Fresh
Used
Fresh
Used
Fresh
Used
Fresh
Used
R.T.
C2-300
C2-400
C2-500
O2-500
P/V
1,81
1,80
1,79
1,81
1,80
1,80
1,91
1,92
1,80
1,80
O/V corr
6,51
6,44
6,26
6,13
6,33
5,92
6,53
5,98
6,19
6,16
E. Bordes-Richard - 2006 CONCORDE-Thessaloniki
V/Si
1.19
0.87
1.16
0.81
1.12
0.81
1.07
0.82
1.14
0.92