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• 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
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. Reduction of cupric chloride (ethylene chlorination)
II. Reoxidation of the cuprous chloride
III. Chlorination of cupper oxide
2 4 2 2 4 2 22 1 / 2C H HCl O C H Cl H O
CuCl2+CuO
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
Deactivation: Cu redistribution and lost
(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(μm2)
Average length of
throats(μm)
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: coke formation
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/γ-Al2O3, T = 483K
Deactivation??
ETHYLENE OXYCHLORINATION
I. Reduction of cupric chloride (ethylene chlorination)
II. Reoxidation of the cuprous chloride
III. Chlorination of cupper oxide
2 4 2 2 4 2 22 1 / 2C H HCl O C H Cl H O
CuCl2+CuO Low melting pointHigh volatilization
VCM project supported by inGap Objectives
• 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• 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
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/γ-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)
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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/γ-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=r1
rp=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.
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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.
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Conference chairs: Prof. Hilde Venvik & Prof. Anders Holmen, NTNU Deadline for abstract submission: Oct. 15, 2015
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Thanks for your attention!
The supports from Norwegian Research Council and Statoil are highly acknowledged.
