wrocław, september 20th, 2010 mechanism of hcl oxidation (deacon process) over ruo 2 gerard...
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Wrocław, September 20th, 2010
Mechanism of HCl oxidation (Deacon process) over RuO2
Gerard Novell-Leruth
The Institute of Chemical Research of Catalonia
Scheme
• Deacon process
• Ruthenium Oxide
• Reactivity on RuO2(110)
• Microkinetic analysis
• Conclusions
The Chlorine Tree
The Chlorine Tree
The Production consumption per weight produced is near to iron and steel production.
• Chloroalkali process2 NaCl + 2 H2O → Cl2 + H2 + 2 NaOH3600 -3300 kWh / ton of Chlorine• Deacon Process4 HCl + O2 → 2 Cl2 + 2 H2O
Deacon process is:4 HCl + O2 → 2 Cl2 + 2 H2O
∆H = -114 kJ/mol
Henry Deacon in 1874 (CuO2)
CuO2 at 400-450 ºC
• Kel-Chlor (NO,NO2, NOCl) • Shell-Chlor (CuCl2-KCl/SiO2)
• MT-Chlor (Cr2O3/SiO2)
Chlorine production
Deacon process is:4 HCl + O2 → 2 Cl2 + 2 H2O
∆H = -114 kJ/mol
Henry Deacon in 1874 (CuO2)
CuO2 at 400-450 ºC
• Kel-Chlor (NO,NO2, NOCl) • Shell-Chlor (CuCl2-KCl/SiO2)
• MT-Chlor (Cr2O3/SiO2)
Sumitomo Chemicals
RuO2/TiO2 (rutile)High activityLow Temperature (300 ºC)Stability Production of 400 kton per year in a single reactor
Chlorine production
Scheme
• Deacon process
• Ruthenium Oxide
• Reactivity on RuO2(110)
• Microkinetic analysis
• Conclusions
RuO2 powder structure
(100), (110), (001) and (101) are the common surfacesShow Rucus atoms: Coordination 5
RuO2(110) is the most common surface
(110)(101)(100)(001)
Different RuO2 activities
Different nature of the exposed sites i.e. nanoparticle structure
20 30 40 50 60 70
111
00222
0
210
211
200
101
used
Inte
nsity
/ a.
u.
2 / degree
fresh
110
310 11
230
1
110
101
100
20 30 40 50 60 70
111
00222
0
210
211
200
101
used
Inte
nsity
/ a.
u.
2 / degree
fresh
110
310 11
230
1
110
101
100
N. López, J. Gómez-Segura, R. P. Marín, J. Pérez-Ramírez, J.Catal., 255, 2008, 29-39
Faces γ / eV·Ǻ-2 Area / %
110 0.041 43
101 0.051 42
100 0.047 14
001 0.075 > 1
RuO2 (110)
Deacon process is:HCl + ¼ O2 → ½ Cl2 + ½ H2O
RuO2(110) is the most
common surface
RuO2 (110)
Deacon process is:HCl + ¼ O2 → ½ Cl2 + ½ H2O
RuO2(110) is the most
common surface
5 Layers
RuO2 (110)
Deacon process is:HCl + ¼ O2 → ½ Cl2 + ½ H2O
RuO2(110) is the most
common surface
5 Layers
Unit Cell
Computational details
•DFT (VASP)
•RPBE functional
•PAW pseudopotentials
•Cut-off of 400 eV
Scheme
• Deacon process
• Ruthenium Oxide
• Reactivity on RuO2(110)
• Microkinetic analysis
• Conclusions
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
Common proposed mechanism
Oxygen adsorption
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
O2 + 2* ↔ O2c*
Eads=-0.66 eV
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
Oxigen dissociation
O2** ↔ 2 Oc*
Ea=0.40 eVDE=-0.41 eV
HCl+*+Ob* ↔ Clc*+ObH*
HCl+*+Oc* ↔ Clc*+OcH*
HCl reaction
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
1 reaction 2 configurations
HCl+*+Ob* ↔ Clc*+ObH*
HCl+*+Oc* ↔ Clc*+OcH*
HCl reaction
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
1 reaction 2 configurations
HCl* + Ob* ↔ Cl* + ObH* HCl* + Oc* ↔ Cl* + OcH* Ea < 0.01 eV Ea < 0.01 eV
DE=-1.46 eV DE=-1.23 eV
OcH* + OcH* ↔ Oc* + H2Oc*
ObH* + OcH* ↔ Ob* + H2Oc*
HCl + *+OcH*↔ Cl*+H2Oc*
ObH*+OcH*↔ H2Ob*+H2Oc*
ObH*+Oc*↔ Ob*+OcH*
Water formation
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
1 reaction 2 configurations
OcH* + OcH* ↔ Oc* + H2Oc*
ObH* + OcH* ↔ Ob* + H2Oc*
HCl + *+OcH*↔ Cl*+H2Oc*
ObH*+OcH*↔ H2Ob*+H2Oc*
ObH*+Oc*↔ Ob*+OcH*
Water formation
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
1 reaction 2 configurations
OcH* + OcH* ↔ Oc* + H2Oc* ObH* + OcH* ↔ Ob* + H2Oc*Ea = 0.38 eV Ea = 0.24 eVDE= 0.24 eV DE=-0.11 eV
Water desorption
H2Oc* ↔ H2O + *
Eads= -0.90 eV
O2+2*↔ O2**
O2**↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
Chlorine formation
Clc* + Clc* ↔ Cl2 + 2 *
Eads= -1.56 eV
O2+2*↔ O2**
O2+2*↔2O*
HCl+*+O*↔Cl*+OH*OH*+OH*↔H2O*+O*
H2O*↔H2O +*
Cl*+Cl*↔Cl2+2*
Scheme
• Deacon process
• Ruthenium Oxide
• Reactivity on RuO2(110)
• Microkinetic analysis
• Conclusions
O2 + 2 * ↔ O2**
O2**
↔ 2 Oc*
HCl + * + Ob* ↔ Clc* + ObH*
HCl + * + Oc* ↔ Clc* + OcH*
OcH* + ObH* ↔ H2Oc* + Ob*
OcH* + OcH* ↔ H2Oc* + Oc*
Oc* + ObH* ↔ OcH* + Ob*
H2Oc* ↔ H2O + *
Clc* + Clc* ↔ Cl2 + 2 *
Mechanism and reaction parameters
Ea / eV ΔE / eV
< 0.01 -0.66
0.38 -0.76
< 0.01 -1.46
< 0.01 -1.23
0.38 0.27
0.24 -0.11
0.55 -0.01
0.90 0.90
1.56 1.56
HCl + ¼ O2 → ½ Cl2 + ½ H2O
RuO2(110)
Microkinetic modeling
Differential-Algebraic Equation (DAE) system
Temporal evolution of each species
+Initial Conditions (P(HCl), P(O2)..)
O2 + 2 * ↔ O2**
O2**
↔ 2 Oc*
HCl + * + Ob* ↔ Clc* + ObH*
HCl + * + Oc* ↔ Clc* + OcH*
OcH* + ObH* ↔ H2Oc* + Ob*
OcH* + OcH* ↔ H2Oc* + Oc*
Oc* + ObH* ↔ OcH* + Ob*
H2Oc* ↔ H2O + *
Clc* + Clc* ↔ Cl2 + 2 *
•Transition State Theory (r=k·CR)
•Static results as “batch reactor”
•Energy independent of the coverage
•Initial conditions P(HCl) = 2·105 Pa P(O2) = 4·105 Pa
T = 570 K
Microkinetic modeling
Results: Cl2 production vs T and t
Initial Conditions:
P(O2) = 4·105 Pa
P(HCl) = 2·105 Pa
Results: Presure vs Temperature
Initial Conditions:
P(O2) = 4·105 Pa
P(HCl) = 2·105 Pa
Time = 1 s
Experimental T regim
P(O2)
P(HCl)
P(Cl2)
P(H2O)
Results: P and Coverage vs time
time / s
Initial Conditions:
P(O2) = 4E5 Pa
P(HCl) = 2E5 Pa
T = 570 K
P(O2)
P(HCl)P(Cl2) P(H2O)
θ(ObH)
θ(Ob)
θ(Clc)
θ(Oc)
Mechanism
Our proposed mechanism contains the following elementary steps:
O2+2*↔2O*
HCl+O*+*↔OH*+Cl*
OH*+OH*↔H2O+O*
Cl*+Cl*↔Cl2+2*
O2 + 2 * ↔ O2**
O2**
↔ 2 Oc*
HCl + * + Ob* ↔ Clc* + ObH*
HCl + * + Oc* ↔ Clc* + OcH*
OcH* + ObH* ↔ H2Oc* + Ob*
OcH* + OcH* ↔ H2Oc* + Oc*
Oc* + ObH* ↔ OcH* + Ob*
H2Oc* ↔ H2O + *
Clc* + Clc* ↔ Cl2 + 2 *
P(O2)
P(HCl)P(Cl2) P(H2O)
Variations at microkinetic models
time / s
P(O2)
P(HCl)P(Cl2) P(H2O)
Initial Conditions:
P(O2) = 4E5 Pa
P(HCl) = 2E5 Pa
T = 570 K
Full Model
Reduced Model
Mechanism
Our proposed mechanism contains the following elementary steps:
O2+2*↔2O*
HCl+O*+*↔OH*+Cl*
OH*+OH*↔H2O+O*
Cl*+Cl*↔Cl2+2*
O2 + 2 * ↔ O2**
O2**
↔ 2 Oc*
HCl + * + Ob* ↔ Clc* + ObH*
HCl + * + Oc* ↔ Clc* + OcH*
OcH* + ObH* ↔ H2Oc* + Ob*
OcH* + OcH* ↔ H2Oc* + Oc*
Oc* + ObH* ↔ OcH* + Ob*
H2Oc* ↔ H2O + *
Clc* + Clc* ↔ Cl2 + 2 *
Scheme
• Deacon process
• Ruthenium Oxide
• Reactivity on RuO2(110)
• Microkinetic analysis
• Conclusions
Conclusion
• Mechanism of the global process
• The bridge Oxygen acts as a reservoir of H
• Microkinetic model with DFT results
• Discussion of species in the process as function of the reaction conditions
Acknowledgements
THANKS FOR
YOUR ATTENTION !!!