E. Bordes-Richard CONCORDE-Thessaloniki Old and New Ideas for VPO? Application to DuPont Catalysts Elisabeth BORDES-RICHARD Laboratoire de Catalyse de Lille

E. Bordes-Richard 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 CONCORDE-Thessaloniki CFBR  Characteristics [1,2] [1] R.M. Contractor et al. Catal.Today, 1 (1987) 49 etc [2] G. Patience et al. Trans.I.ChemE, 68 (1990) 301 etc Solid flux > 50 kg.m -2 s -1 Superficial gas velocity > 2 ms -1 Residence time: few seconds Transient cyclic state ==> improve performance Riser:  nearly plug flow  high heat & mass transfers Controlled and separated delivery:  of O 2- from solid to molecule: oxocapacity  of gaseous O 2 to solid

E. Bordes-Richard CONCORDE-Thessaloniki DuPont VPO Catalyst  Composition: V,P,O,Si  Silica matrix embedding catalyst particles: attrition and erosion resistant [3] SEM on used cat; EDX: V, P, Si, Fe (LCL) [3] R.M. Contractor et al., Fluidization VI, Engineering Foundation New-York, 1989; pp

E. Bordes-Richard CONCORDE-Thessaloniki DuPont VPO Catalyst DuPont recipe (R.M. Contractor et al.) V 2 O 5 /isobutyl/benzyl alcohols + H 3 PO 4 (85%) + TEOS P/V = 1.0x/1.0 Calcination 400°C  Catalyst Spray-drying of VPO(Si) precursor with silicic acid (ca. 1Owt%)  microspheres ø =  m

E. Bordes-Richard CONCORDE-Thessaloniki DuPont VPO Catalyst  Precursor: VOHPO 4 0.5H 2 O Johnson et al., Torardi et al., 1984 Face-sharing octahedra Layered structure,  Platy primary particles, rosets as secondary particles  Oxidation of prec. (air, 400°C)   -VOPO 4 [4] [4] E. Bordes, unpublished results  Catalyst: (VO) 2 P 2 O 7 (mean oxidation state: V 4.0x+ ) Gorbunova 1978, Sleight et al Edge-sharing octahedra Layered structure,  Platy primary particles, rosets as secondary particles  Oxidation of cat. (air, 400°C)   -VOPO 4 [4] Control of VOHPO 4 0.5H 2 O ==> Control of (VO) 2 P 2 O 7 Topotactic dehydration, pseudomorphism [5] [5] E. Bordes et al., J.Solid State Chem. (1984); Torardi et al., Inorg. Chem. (1984)

E. Bordes-Richard CONCORDE-Thessaloniki CFBR  Redox decoupling: optimize the working conditions Same particle alternatively reduced (riser) and oxidized (regenerator) Co-feedCFBR O 2- O2O2 E. Bordes and R.M. Contractor, Topics Catal., 3 (1996) 365. n-C 4 MA O2O2 C 4 MA C 4 MA Oxocapacity: O 2- delivery vs. MA prod. O 2-

E. Bordes-Richard CONCORDE-Thessaloniki CFBR (foll.)  (slightly) different properties of VPO catalyst Fixed B. Fluidized B.CFBR P/V ratio Texture Attrition-resistant Other phases  -VOPO 4  -VOPO 4 "bulky" (VO) 2 P layered (VO) 2 P (100) O2O2 E. Bordes et al., Catal. Lett. 1999

E. Bordes-Richard CONCORDE-Thessaloniki Experiments  Benchmarking  Precursor/Catalyst: Oxocapacity  Precursor dehydration and activation: genesis and control of morphology (topotaxy), V oxidation state, P/V,....  Influence of pO 2 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.! Keypoints: Oxocapacity, reactivity

E. Bordes-Richard 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 CONCORDE-Thessaloniki XRD Fresh cat: (VO) 2 P 2 O 7 Used cat: (VO) 2 P 2 O 7 +  -VOPO 4,  Identification  Precursor: usual pattern of layered VOHPO 4.0.5H 2 O  Catalyst  -VOPO

E. Bordes-Richard CONCORDE-Thessaloniki Laser Raman Spectroscopy  Fresh and used cats  Fresh: (VO) 2 P 2 O 7 (9/10 particles): 929 (+ 1129, 1180) cm -1  -VOPO 4 (1/10): 931, 1013, 1074 cm -1  Used: heterogeneous mixture (VO) 2 P 2 O 7 (6/10 particles): 931 (+ 1128, 1180) cm -1  -VOPO 4 (3/10): 884, 987, 1060 cm -1 and   -VOPO 4 (1/10): 938, 990, 1087 cm -1 J.C. Volta et al., G.L. Schrader et al.

E. Bordes-Richard CONCORDE-Thessaloniki In situ Redox XRD  In situ reactivity of fresh and used cats  Reduction by H 2 /He (1 h at 300, 400, 500°C) followed by reoxidation in air (1 h 500°C)  -VOPO 4 Fresh cat: (VO) 2 P 2 O 7 Used cat: (VO) 2 P 2 O 7 +  -VOPO 4

E. Bordes-Richard CONCORDE-Thessaloniki XPS (fresh and used cats)  As is and after grinding  Systematic higher V/Si when ground  P/V =  After redox pre-treatment with ethane (20 mn at 200, 300, 400°C and air at 400°C)  Reduction steps Very little modification of V 2p3/2 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 V 5+ + V 4+ for fresh cat.; V 5+ for used cat P/V = V/Si = 1.14 for fresh; 0.92 for used cat.

E. Bordes-Richard CONCORDE-Thessaloniki  XPS  As received and ground samples:  no difference  P/V  1.80 up to 400°C; 1.91 at 500°C XPS (fresh and used cats)