Presentation on theme: "E. Bordes-Richard - 2006 CONCORDE-Thessaloniki Old and New Ideas for VPO? Application to DuPont Catalysts Elisabeth BORDES-RICHARD Laboratoire de Catalyse."— Presentation transcript:
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]  R.M. Contractor et al. Catal.Today, 1 (1987) 49 etc  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  SEM on used cat; EDX: V, P, Si, Fe (LCL)  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 (air, 400°C) -VOPO 4   E. Bordes, unpublished results Catalyst: (VO) 2 P 2 O 7 (mean oxidation state: V 4.0x+ ) Gorbunova 1978, Sleight et al Edge-sharing octahedra Layered structure, Platy primary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  Control of VOHPO 4 0.5H 2 O ==> Control of (VO) 2 P 2 O 7 Topotactic dehydration, pseudomorphism   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)