metal catalysts in catalytic wet air oxidation -...
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1November 2010, 16thMetal Kokkola 2010http://lacco.labo.univ-poitiers.fr
Sylvain KEAV, Jacques BARBIER Jr.
Catalysis by metals
Metal catalysts in Catalytic Wet Air Oxidation
energy energy –– environment environment –– fine chemistryfine chemistry
November 2010, 16th
Pollutant
O
O2
MSupport
CO2H2O
2November 2010, 16thMetal Kokkola 2010 22
CONTENTSA. Context
B. Water treatment
C. Water treatment processes
D. Wet Oxidation processes
E. Catalytic Wet Air Oxidation
F. Future of the process
3November 2010, 16thMetal Kokkola 2010
A. Context
4November 2010, 16thMetal Kokkola 2010 44
• Problem: – Human activities (domestic or industrial) → contaminated waters,
– Environmental impact, – Decrease in the amount of drinking
water.
A. Context
• Water: A few data– 65 % of human body, – 70 % of the surface of the Earth, – 3 % under the form of fresh water, – Mean daily needs: 20-50 L/person/day.
→ Rare and precious resource to be protected
5November 2010, 16thMetal Kokkola 2010 5
• Water availability forecast:– An unattractive future…– A world of thirst…
• Water pollution control laws
A. Context
6November 2010, 16thMetal Kokkola 2010
B. Water treatment
7November 2010, 16thMetal Kokkola 2010 7
• Water treatment: from polluted to fresh water– 4 steps:
Large objects (screening)(40 mm – 0.5 mm)
Sand and Grit (settling)(0.2-0.5 mm) Fats (skimmers)
B. Water treatment
• 1. Pretreatment: – Removal of all materials easily collectable from the raw wastewater and
which could damage the apparatus (pump, skimmer, etc.).
8November 2010, 16thMetal Kokkola 2010 8
• Water treatment: from polluted to fresh water– 4 steps:
Raw water
Treated water
Sludge
Removal of:
- 60-65 % of suspended solids,
- 30-35 % of Chemical OxygenDemand (COD).
B. Water treatment
• 2. Primary treatment: – Physical separation: Flocculation/Sedimentation stage
9November 2010, 16thMetal Kokkola 2010 9
• Water treatment: from polluted to fresh water– 4 steps:
• 3. Secondary treatment: Degradation of organic pollutants– Biological treatments, – Physico-chemical treatments.
• 4. Tertiary treatment (optional): Final raise of the effluent quality– Filtration, – Disinfection (ozonation, chlorination or UV treatment).
C. Water treatment processes
Discharge or reuse
B. Water treatment
10November 2010, 16thMetal Kokkola 2010
C. Water treatment processes
11November 2010, 16thMetal Kokkola 2010 11
• Biological treatment:– Digestion by microorganisms (bacteria,
fungi, protozoa), – Aerobic or anaerobic treatment.
• Incineration:– Combustion in specific oven at elevated
temperature (> 1000 °C).
• Physical processes:– Stripping, Adsorption, Membrane processes, etc. – Reduction of pollution to acceptable levels.
C. Water treatment processes
12November 2010, 16thMetal Kokkola 2010 12
• Oxidation processes:
[O]Presence or absence
of a catalystCxHyOz
CO2, H2O
C. Water treatment processes
– Classic chemical processes: Cl2, ClO2, KMnO4, FeO42-,
– Advanced Oxidation Processes (Active species: HO•, HO2•, O2
•-): • Ozonation (O3), • Wet Peroxide Oxidation (H2O2), • Fenton (H2O2/Fe2+), • Photocatalysis (O2 activated by UV/TiO2),
– Wet Air Oxidation processes (pressurized O2). D. Wet Oxidation
processes
13November 2010, 16thMetal Kokkola 2010 13
Process Advantages Drawbacks Limits Duration Cost (€/m3)
Biological treatment
Low cost, Easy to perform
Duration, Surface of the installation, Production of
sludge
Diluted, biodegradable and non toxic compounds
25-60 h < 1 to 25
Incineration Very fast, All kind of pollutants
Expensive, Production of ashes,
solid wastes and toxic fumes (HCl, NOx, SOx, dioxins)
Very concentrated effluents
A few seconds 50 to 200
Physical processes
Cheaper than incineration, All
kinds of pollutants
Limited yields, Pollution not destroyed but
displaced
Low concentrated effluents 1-30 min < 1 to 60
Oxidation processes
Cheaper than incineration, All
kinds of pollutantsOperating costs Refractory
compounds 10-120 min 5 to 35
C. Water treatment processes
• Comparison of water treatment processes:
14November 2010, 16thMetal Kokkola 2010 14
• Fields of application1:
C. Water treatment processes
1G. Centi, Expert Group Meeting on "Cleaner Technologies for Sustainable Chemistry", International Center for Science and High Technology, 2002.
15November 2010, 16thMetal Kokkola 2010
D. Wet Oxidation processes
16November 2010, 16thMetal Kokkola 2010 1616
• Thermal Wet Air Oxidation (TWAO):
– Early 20th century,
– Principle: • Total oxidation: • Limited solubility of O2, • T = 125-450 °C, P = 5-200 bar,
– Field of application: • Intermediate pollution, • Toxic or non biodegradable compounds,
– Typical performances : • 80-99 % conversion after 10-120 min, • Incomplete mineralization ↔ formation of refractory intermediates.
D. Wet Oxidation processes
( ) ( ) ( ) ( )l2g2aq2aqzyx OH2yCOxO
2z
4yxOHC +⎯→⎯⎟
⎠⎞
⎜⎝⎛ −++
17November 2010, 16thMetal Kokkola 2010
• Oxidability scale1:
0.6
0.0
0.2
0.4
1.0
0.8
Oxidability
Acetic acidPropionic acid
n-butanoic acid
Paper industry effluent
Sewage slugeDye industry effluent
Oxalic acid
Isobutanol
1H. Debellefontaine et al., Environ. Pollut., 92, 154-164, 1996
Carboxylic acids :– Refractory to oxidation,– Easily biodegradable
→ Biological treatment.
D. Wet Oxidation processes
18November 2010, 16thMetal Kokkola 2010
• Wet Oxidation process objective?
D. Wet Oxidation processes
Total degradation:
One-step treatment
Partial degradation:
Two-step treatment
High temperature and pressure
Moderate temperature and pressure
Main reaction products: CO2, H2O
Main reaction products: Carboxylic acids, CO2, H2O
Reuse or discharge
Biological treatment
19November 2010, 16thMetal Kokkola 2010
Elevated costs
Pollutant
O
O2
MSupport
CO2H2O
D. Wet Oxidation processes
• TWAO drawbacks: – Severe operating conditions, – Acidic/Corrosive medium → Resistant reactors,– Refractory intermediates.
• Improvement of efficiency, • Milder operating conditions:
– T ≤ 200 °C, P ≤ 30 bar,
• Better elimination of refractory organic compounds better mineralization,
• Decrease in operating costs.
→ Catalytic system
20November 2010, 16thMetal Kokkola 2010
• Commercial applications: – Complete oxidation or conditioning of sewage sludge, – Treatment of industrial wastewaters:
• Paper, dye, detergent, food, sugar (etc.) industries, • Alcohol distillery waste, • Chemical, petrochemical, pharmaceutical industries,
– Treatment of polluted waters: • Pesticides,
– Spent activated carbon regeneration.
• Fundamental research: – Model molecules:
• phenol and derivatives, carboxylic acids, nitrogen containing organic compounds, ammonia,
– Real industrial wastewaters.
D. Wet Oxidation processes
21November 2010, 16thMetal Kokkola 2010
E. Catalytic Wet Air Oxidation
I. Wet Air Oxidation catalystsII. Deactivation of WAO catalystsIII. CWAO reactors and processes
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I. Wet Air Oxidation catalystsE. Catalytic Wet Air Oxidation
• Homogeneous catalysts: – Metallic salts:
• Copper and Iron salts,
– Advantages: • Very active,
– Drawbacks: • Precipitation/Separation step: Cu2+
(aq) → Cu(OH)2(s) or CuS(s), • Loss of catalyst, • Increase in operating time and costs.
23November 2010, 16thMetal Kokkola 2010 2323
I. Wet Air Oxidation catalystsE. Catalytic Wet Air Oxidation
1R.P. Kochetkova et al., Khim. Tekhnol. Topl. Masel, 4, 31, 1992.
• Heterogeneous catalysts: – Transition metals and oxides of transition metals:
• Examples: – Al, Bi, Ce, Cd, Co, Cr, Cu, Fe, Mn, Ni, Ti, V, Y, Zn, Zr, etc., – Simple oxides1: CuO > CoO > Cr2O3 > NiO, – Mixed oxides: Combinations of simple oxides (MnO2-CeO2, ZrxCe1-xO2,etc.)
• Advantages: – Cheap,
• Drawbacks: – Less active than metal salts (75-90 % mineralization), – Limited stability.
24November 2010, 16thMetal Kokkola 2010 2424
I. Wet Air Oxidation catalystsE. Catalytic Wet Air Oxidation
• Heterogeneous catalysts: – Carbon based catalysts:
• Examples: – Activated carbon, – Carbon Black Composite (CBC), – Carbon nanotubes,
• Advantages: – High adsorptive properties, – Resistant to acidic conditions, – Cheap,
• Drawbacks: – Combustion of the catalyst.
25November 2010, 16thMetal Kokkola 2010 2525
I. Wet Air Oxidation catalystsE. Catalytic Wet Air Oxidation
• Heterogeneous catalysts: – Supported noble metal catalysts:
• Examples: – Active phase: 0.1-5.0 wt-% Ir, Pd, Pt, Rh, Ru, – Typical supports: γ-Al2O3, CeO2, TiO2, ZrO2, SiO2, Activated carbon, – Ranking depends on support phase and on oxidized compounds1,2,3,
• Advantages: – Very active (85-98 % mineralization), – Very stable,
• Drawbacks: – Very expensive.
1S. Imamura et al. Ind. Eng. Chem. Res., 27, 718-721, 1988. 2J. Trawczynski et al., Carbon, 41, 1515-1523, 2003. 3J. Barbier Jr., Top. Catal., 33, 77-86, 2005.
26November 2010, 16thMetal Kokkola 2010 2626
I. Wet Air Oxidation catalystsE. Catalytic Wet Air Oxidation
0 60 120 1800
20
40
60
80
100
ΔTO
C (%
)
t (min)
Blank Ce PtCe RuCe ZrCePr PtZrCePr RuZrCePr
1S. Keav et al., Catal. Today, 151, 143-147, 2010.
• Example: – Activity of Pt and Ru catalysts supported on CeO2, Zr0.1Ce0.9O2 and
Zr0.1(Ce0.75Pr0.25)0.9O2 oxides1:
– CWAO of phenol in a batch reactor:
• Significant increase in activity, • Pt > Ru.
27November 2010, 16thMetal Kokkola 2010 2727
II. Deactivation of WAO catalysts
SupportM0 M0M0M0
SupportM0 M0M0M0
Mx+(aq)
Mx+(aq)
Mx+(aq)
Mx+(aq)
– Loss of active species, – Secondary pollution.
– Irreversible, – Optimization of
synthesis protocols, – Operating conditions.
Lixiviation
E. Catalytic Wet Air Oxidation
• Homogeneous catalysts:– Precipitation or complexation of metal ions,
• Heterogeneous catalysts: – Several deactivation phenomena:
28November 2010, 16thMetal Kokkola 2010 2828
II. Deactivation of WAO catalysts
SupportM0 M0M0M0
Support
M0 M0
– Irreversible, – Optimization of
synthesis protocols, – Operating conditions.
– Decrease in active surface, – Rare in CWAO.
Sintering
E. Catalytic Wet Air Oxidation
• Example: – CWAO of succinic acid on 2.2 wt-% Au/TiO2
1:
9.71.7Initial2.34.2After sintering
TOF (molSucc.molAu-1.h-1)dp (nm)
1M. Besson et al., Catal. Commun., 4, 471-476, 2003.
29November 2010, 16thMetal Kokkola 2010
II. Deactivation of WAO catalysts
SupportM0 M0M0M0
– Reversible, – Operating conditions.
– Blocking of active sites, – Favoured if unsaturated
molecule.
Deposition of strongly adsorbed organic
species (poisoning or fouling)
SupportM0 M0M0M0
E. Catalytic Wet Air Oxidation
– Reactivation by combustion, cracking or extraction.
30November 2010, 16thMetal Kokkola 2010 30
II. Deactivation of WAO catalysts
Deposit
Before CWAO After CWAO
E. Catalytic Wet Air Oxidation
1S. Keav et al., C. R. Chimie, 13, 508-514, 2010
• Transmission Electron Microscopy images: – 2.5 wt-% Pt/CeO2 tested in CWAO of phenol1
31November 2010, 16thMetal Kokkola 2010 3131
II. Deactivation of WAO catalystsE. Catalytic Wet Air Oxidation
• Catalyst reactivation:
0 60 120 1800
20
40
60
80
100Δ
TOC
(%)
t (min)
Fresh Deactivated Reactivated
32November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes• More than 200 WAO plants in operation in the world1, • Several industrial technologies with different catalysts, • Difference between research and commercial reactors:
– Batch reactor:
1V.S. Mishra et al., Ind. Eng. Chem. Res., 34, 2-48, 1995.
E. Catalytic Wet Air Oxidation
O2(g) P
T
..
. .. ..
. ..
.. • Most of fundamental studies, • Easy to perform, • Continuous reactors favoured
for commercial applications.
33November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes– Continuous stirred-tank reactor:
• Laboratory-scale pilot reactor
Gasoutlet
Outlet tank
T
O2
Inlet tank
P
F Gasoutlet
Outlet tank
TT
O2
Inlet tankInlet tank
PP
FF
E. Catalytic Wet Air Oxidation
34November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes• BAYER LOPROX® (Low-pressure Wet Oxidation):
– Bubble column reactor,– Mild conditions → Pretreatment prior to biological
treatment.
Fe2+
+ co-catalyst
Catalyst
7-30120-2003-20
Capacity (m3.h-1)T (°C)P (bar)
1O. Horek et al. Bayer AG, Swedish patent SE 7 613 832 A, 1977.
E. Catalytic Wet Air Oxidation
35November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes
• CIBA-GEIGY® process1: – Reactor divided into individual tube sections, – Mobile installation.
1F. Yoahimu et al., Ciba Geigy AG, Japanese patent JP 4 227 100 A, 1992.
E. Catalytic Wet Air Oxidation
Cu2+≈ 300≈ 150CatalystT (°C)P (bar)
36November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes• ATHOS® process1:
– Sludge treatment, – 12 m X 6 m X 10 m installation.
1F. Luck, Catal. Today, 53, 81-91, 1999.
E. Catalytic Wet Air Oxidation
Cu2+ or CuO220-23540CatalystT (°C)P (bar)
37November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes
• NIPPON SHOKUBAI KAGAKU® process1: – Trickle-bed reactor.
1T. Ishii et al., Nippon Shokubai Kagaku Kogyo Co. Ltd., European patent EP 0 431 932 A1, 1990.
E. Catalytic Wet Air Oxidation
Metal/TiO2 + Oxide of a lanthanide element
(Monoliths)< 3709-80
CatalystT (°C)P (bar)
38November 2010, 16thMetal Kokkola 2010
III. CWAO reactors and processes
• OSAKA GAS® process1: – Bubble column reactor,
1N. Okada, Osaka Gas Co. Ltd., Japanese Patent, JP 53 020 663 A, 1976.
E. Catalytic Wet Air Oxidation
Metal/ZrO2 or Metal/ZrO2-TiO2
250-32070
CatalystT (°C)P (bar)
39November 2010, 16thMetal Kokkola 2010
F. Future of the process
40November 2010, 16thMetal Kokkola 2010
• One of the most efficient processes for intermediate pollution, • Applicable to continuous technologies, • Powder catalysts for bubble column reactors,• For other continuous reactors → shaped catalysts:
– Pellets, – Beads, – Rings, – Foams, Monoliths.
F. Future of the process
41November 2010, 16thMetal Kokkola 2010
• Foam and monolithic catalysts:– Catalyst deposited on a ceramic foam or honeycomb structure,– Advantages:
• Large variety of channel shape and size, • No risk of reactor clogging due to solid particles, • High mass transfer rates,
– Widely used in various gas phase applications (VOC oxidation, catalytic converter, etc.),
– Challenge: • Active phase resistant to aqueous medium.
F. Future of the process
Ceramic support
Deposited active phase
42November 2010, 16thMetal Kokkola 2010
Thank you for your attention…
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