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Deactivation of oxychlorination catalysts - Topsoe · PDF fileOutline • Introduction...

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  • Deactivation of oxychlorination catalystsK. R. Rout, Jun Zhu, Martina F. Baidoo, Endre Fenes,

    Gerard Ayuso Virgili, De Chen*

    1Department of Chemical Engineering, Norwegian University of Science and Technology, Trondheim, NO-

    7491, Norway.

  • Outline

    Introduction Deactivationofindustrialcatalysts Transientandsteadysatekineticstudy Predictivekineticmodelforthecatalystoxidationstateinthecatalyticcycle

    Kineticsguidedcatalystdesign Pelletandreactormodeling

  • VCM process on CuCl2 catalysts

    Challenges:

    The catalyst lifetime: deactivation mechanism of catalyst deactivation Better understanding of reaction mechanism and kinetics of elementary steps

  • ETHYLENE OXYCHLORINATION

    I.Reductionofcupricchloride(ethylenechlorination)

    II.Reoxidationofthecuprouschloride

    III.Chlorinationofcupperoxide

    2 4 2 2 4 2 22 1 / 2C H HCl O C H Cl H O

    CuCl2+CuO

  • Outline

    Introduction Deactivationofindustrialcatalysts Transientandsteadysatekineticstudy Predictivekineticmodelforthecatalystoxidationstateinthecatalyticcycle

    Kineticsguidedcatalystdesign Pelletandreactormodeling

  • Deactivation:Curedistributionandlost

    (a) (b)

    CuCl2and CuCl

    SARI_Xradia Versa 5 tomography, Carl Zeiss

  • Pore surfaceVolume Pore throat

    Deactivation: Sintering

    Porosity (%)

    Connectivity rate of pores

    (%)

    Total no. of pores

    Total no. of throats

    Mean area of throats(m2)

    Average length of

    throats(m)

    Average coordination

    number

    Tortuosity of throats channel

    Used catal. 7.36 0.3 9234

    11174 15.895 10.834 2.419 4.397

    Micro CT scanning: low coordination number and low pore connectivity,

  • Deactivation:cokeformation

    Coke ring formed inside the catalyst pellets

  • Oxychlorination reaction in alaborator fixed-reactor

    Partial pressure (kPa)Ethylene Oxygen HCl Ar

    1.89 1.90 1.89 Other6.11 %wt Cu/-Al2O3, T = 483K

    Deactivation??

  • ETHYLENE OXYCHLORINATION

    I.Reductionofcupricchloride(ethylenechlorination)

    II.Reoxidationofthecuprouschloride

    III.Chlorinationofcupperoxide

    2 4 2 2 4 2 22 1 / 2C H HCl O C H Cl H O

    CuCl2+CuO Low melting pointHigh volatilization

  • VCMprojectsupportedbyinGapObjectives

    Development of in-situ method to monitor the gas phase and surface composition in transient and steady-state experiments

    Reaction mechanism and kineticsof each step Kinetics of the catalytic cycle of ethylene

    oxychlorination including catalyst composition Pellet and reactor modeling

  • Outline

    Introduction Deactivationofindustrialcatalysts Transientandsteadysatekineticstudy Predictivekineticmodelforthecatalystoxidationstateinthecatalyticcycle

    Kineticsguidedcatalystdesign Pelletandreactormodeling

  • 13

    UV-Vis Spectroscopy

    MS

    pH meter

    Ar

    HCl

    O2

    C2H4

    Fixed bed reactor with in-situ space-time resolved MS/UV-Vis spectroscopy

  • 14

    Stratagy of kinetic study

  • 15

    Ethylene conversion and removable Cl uptake

    2CuCl2 +C2H4 = 2CuCl + C2H4Cl2CuCl2 CuCl + Cl

    Maximum Cl uptake (removable): 1 mol/molCu

  • 16

    min

    max min

    tF FNKMFF F

    Synchronization of MS and UV-Vis data

  • 17

    min

    max min

    tF FNKMFF F

    Synchronization of MS and UV-Vis data

  • 18

    Calibration concistency

    Calibration concistent and reproducible

  • 19 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 20 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2CuClx

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 21 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2CuCl CuClx

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 22 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2CuCl CuClx

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 23 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2CuCl CuClx

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 24 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    CuCl2CuCl CuClx

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 25 Dynamic active sites 1

    2 2 4 2 4 22 2kCuCl C H C H Cl CuCl

    a b c

    Matthew NeurockJ. Phys. Chem. B, Vol. 105, No. 8, 2001

  • 26 New kinetic model including the dynamic active sites

    Jun Zhu

    Partial pressure (kPa) Steady state EDC formation rate (mol/g h)

    Predicted rate(mol/g h)Ethylene Oxygen HCl Ar Kinetic UV-vis3.78 3.81 1.89 Other 0.00121.89 1.9 1.89 Other 0.00080.9 1.9 1.89 Other 0.0005

    T=503K, 5.9 %wt Cu/-Al2O3

    Kinetic model based on individual kinetics (step I and II)

    Note I:

    So, is neglected to simplified the model

    During steady-state:

    Note II: Oxygen site coverage is also considered in r1

  • 27 II. Time and Space resolved UV-Vis spectroscopy study

    a) Ethylene conversion and selectivity vs reaction time, b) CuII during reaction time c) KMF vs wave length at different reactor axis for reaction condition I d) CuII vs reactor axis. Steady-state reaction condition I: pC2H4=0.009 atm, pO2=0.0189 atm, pHCl=0.0189 atm Temperature=230 C, total pressure= 1 atm. Steady-state reaction condition II: pC2H4=0.009 atm, pO2=0.0045 atm, pHCl=0.0189 atm Temperature=230 C, total pressure= 1 atm.

    2:1:4

    2:4:4 (1:2:2)

    2:1:4

    2:4:4 (1:2:2)

  • 28

    Steady-State kinetics

    Partial pressure (kPa) Steady state EDC formation rate (mol/g h)

    Predicted rate(mol/g h)Ethylene Oxygen HCl Ar Kinetic UV-vis3.78 3.81 1.89 Other 0.0012 0.00131.89 1.9 1.89 Other 0.0008 0.00070.9 1.9 1.89 Other 0.0005 0.0003

    T=503K, 5.9 %wt Cu/-Al2O3

    Reducible Cu2+

  • 29 II. Time and Space resolved UV-Vis spectroscopy study

    Conclusion: The initial decrease in conversion is a transient process achieving steady state Most of Cu 2+ are reduced at the steady state and oxidation step needs to be

    enhanced

    2:1:4

    2:4:4 (1:2:2)

    2:1:4

    2:4:4 (1:2:2)

  • 30

    Outline

    Introduction Deactivation of industrial catalysts Transient and steady-sate kinetic study Predictive kinetic model for the catalyst

    oxidation state in the catalytic cycle Kinetics guided catalyst design Pellet and reactor modeling

  • 31

    V. Pellet ModelMass balance of species

    Diffusion flux

    Boundary condition

    At rp=0

    rp=r1rp=rs

  • 32 Profile of oxygen across the pellet at different reactor positions

  • 33

    VI. Fixed bed reactor model

    Pseudo-homogeneous Heterogeneous

    Does not account explicitly for the presence of catalyst.It contains effectivenessfactor to account the masstransport phenomena.

    Separate equations for the fluid phaseand the fluid inside the catalyst pores.

    Conventional SimplifiedThis model accounts masstransfer phenomena byconsidering pellet equation.

    Contain effectivenessfactor to account mass transport phenomena.

    Account explicitly for theexternal heat- and massexchange to the solidphase.

  • 34

    Results:Cross-sectional averaged

    0 0.5 1 1.5 2 2.5 3 3.5 4440

    460

    480

    500

    520

    540

    560

    580

    Z [m]

    Tem

    pera

    ture

    [K]

    SimulatedPlant Data

    0 1 2 30.1

    0.2

    0.3

    Z [m]

    y C2H

    4

    0 1 2 3

    0.350.4

    0.45

    Z [m]

    y HC

    l0 1 2 3

    0

    0.05

    Z [m]

    y O2

    0 1 2 30

    0.1

    0.2

    Z [m]y C

    2H4C

    l 2

    0 1 2 30

    0.1

    0.2

    Z [m]

    y H2O

  • 35

    Conclusions The active sites are highly dynamic. Kinetics of Redox reactions including changes in

    gas phase compositions and catalyst compositions can be obtained from kinetics of individual steps.

    Space and time resolved UV-Vis spectroscopy is a powerful tool for kinetic studies of redox reactions.

    Multiscale approach is powerful not only for the simulation and optimization of industrial reactors, but also the rational catalyst design.

  • 36

    Conference chairs: Prof. Hilde Venvik & Prof. Anders Holmen, NTNU Deadline for abstract submission: Oct. 15, 2015

  • 37

    Thanks for your attention!

    The supports from Norwegian Research Council and Statoil are highly acknowledged.

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