CATALYTIC OXIDATION OF VOLATILE

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CATALYTIC OXIDATION OF VOLATILE
ORGANIC COMPOUNDS
S.NAVALADIAN CY02D006 10-09-04
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Contents
Introduction What is VOC? Why
do we need to oxidize? Methods
available. Catalytic Oxidation
Important features of catalyst. A.
Hydrophilic catalysts i) Metal
oxides ii) Zeolites iii)
MCM-41 iv) Perovskites B.
Hydrophobic catalysts i) BN
catalyst ii) Activated carbon Summary
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What is volatile Organic Compound?
Any compound based on carbon and hydrogen with
the vapour pressure greater than 2mmHg at
25ºC is called VOC. It may contain oxygen,
nitrogen and other elements Exceptions CO, CO2
, H2CO3, CH4, metal carbides and metal
carbonates Examples Hexane, Benzene,
Toluene, Dichloro ethane, Methanol, Ethyl
acetate etc.
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Industrial
exhausts
Storage and usage of organic solvents
Combustion of fuels
Petrochemical
complexes
Main Sources

Need of oxidizing VOC VOC
causes - smog formation (Atmospheric
Ozone)
- ozone destruction (Stratosphere)
Smog formation
NO2 h? ? NO O
O olefin ? R RO
R O2 ?
RO2 RO2
NO ? NO2 RO
O O2 ? O3
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In stratosphere
O2 h? ?O O
O2 O ?O3
O3 O ?2O2
O3 h? ? O2 O
O
olefin ? R RO Health effects
Skin cancer and eye
irritation
Affecting central nervous system
Memory loss
Immunological disorders
Respiratory
problems
Damage of lung tissues

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Govt. has introduced some legislations on
industries to control the emission of VOCs
Various methods for VOC elimination 1)Thermal
oxidation a) With flame- natural gas
or propane b) flameless- heat
exchanging bed 2) Membrane Separation liquefying
VOC 3) Regenerative Thermal Oxidation (RTO) 4)
Using adsorbent materials 5) Catalytic oxidation
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Catalytic oxidation of VOCs
Complete oxidation to CO2 and H2O at low
temperatures Important features of catalysts
Hydrophobic nature
Thermal stability
Oxygen storage capacity.
High surface area
Resistance to poisoning
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Experimental setup
Temperature controller
Mass flow controller
GC- MASS unit
Filter
VOC Constant Temp.bath
Furnace
Reactor
Bubbling trap
Cylinders
Schematic diagram
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Noble metal catalysts
Pt and Pd on various supports
Superior activity

• Disadvantages Easily poisoned by
  halogens
• Expensive

Methods of preparations of catalysts
Wet impregnation method Coprecipitation
method Deposition precipitation Citric acid sol
gel method
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Metal Oxide catalysts
Various metal oxides / ?- Al2O3
Toluene oxidation
Wet impregnation method
Cu
Mn
V
Fe
Mo
Co
Ni
Zn
Catalytic Activity (15wt) Cu gt Mn gt Fe gt V gt
Mo gt Co gt Ni gt Zn
Kim. S. C. J. of Hazard. Mater. B 91 (2002)
285299
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Calcination temperature Vs Activity
Catalyst 15 CuO/ ?- Al2O3
Toluene oxidation
500
400
600
700
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Loading of metal Vs Activity
Toluene Oxidation
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5
15
1
100
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Effect of Supports
Toluene oxidation
CuO/?-Al2O3
Cu/TiO2(a)
CuO/TiO2 (r)
CuO/SiO2(1)
CuO/SiO2(2)
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Effect of VOCs
Catalyst 5 CuO /?-Al2O3
Toluene
o-Xylene
Benzene
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Effect of reactant concentration
Toluene oxidation
Reactant concentration should be optimum
for effective oxidation.
160 ppm
1000 ppm
1400 ppm
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Comparison of I-B metals Catalyst Au, Ag
and Cu/Fe2O3
Methanol oxidation
Co-precipitation method
Au
Ag
Cu
Fe2O3
Cu
Temperature programmed reduction
Au/Fe2O3
Ag/Fe2O3
Cu/Fe2O3
Fe2O3 ? Fe3O4 ? FeO
Fe2O3
Au 1.69 V, Ag 0.8V, Cu 0.52V
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XRD powder pattern
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• Au/CeO2
• Coprecipitation method (CP)
• Precipitation deposition (PD)

Au/CeO2(PD)
Au
Au
Au/CeO2 (CP)
CeO2(CP)
Particle size
(using sherrers equation) Au/CeO2(PD)
6nm
XPS
Au/CeO2(CP) 8nm
Au/CeO2(PD)
Two peaks in XPS is due to splitting of Au 4f
to 4f 7/2 and 4f 5/2. Au content lt 1 Peak
area ratio of Au/CeO2(PD) Au/CeO2(CP)
Au/CeO2 (CP)
_________
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Scirè .S, S. Minicò, C. Crisafulli, C. Satriano,
A. Pistone. Appl. Catal. B Environ. 40 (2003)
4349
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TPR
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Au/CeO2(PD)
Au/CeO2 (CP)
Au/CeO2(PD)
Au/CeO2 (CP)
CeO2(CP)
CeO2(CP)
HSACeO2(CP)
High surface area CeO2
Methanol oxidation
Toluene oxidation
Au/CeO2(PD)
Au/CeO2(PD)
Au/CeO2 (CP)
CeO2(CP)
Au/CeO2 (CP)
CeO2(CP)
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• Advantages
• Good redox properties
• Oxygen storage capacity plays the main role
  for good activity
• Gold supported catalyst are showing good
  activity
• Considerable thermal stability

Disadvantages Slightly hydrophilic which
needs high temperature for oxidation
Low surface area
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Zeolite materials
Bronsted acidity
H
Lewis acidity
Lewis acidity
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Zeolite as catalyst supports
Preparation of Pt/H? catalysts
H?
Stirring, 4 h, pH 7
Pt(NH3)4Cl2
1. Si /Al 15 2. Si /Al 50
Filtered, Washed,
Dried 100 C
Calcined, 300 C, 6 h
PtOx/H?
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Characteristics of catalyst
AB-No of Bronsted acid sites,
AL-No of Lewis acid sites
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0.30Pt/ H?(50)
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O-Xylene oxidation
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O-Xylene oxidation
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0.3Pt/ H?(50)
More the Si /Al ratio more will be the
activity. Pt(0) is more active than
PtOx The loading of Pt(0) has
effect in the activity whereas that of Pt
in higher oxidation state has not.
Reduced at 300 ºC
Calcined in air
Light off curve
200 ºC
Reduced at 300 ºC
Calcined in air
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On various materials
Temperature programmed desorption
H-Y
H-?
HZSM-5
Concentration a.u.
VOC Toluene
AC
HMOR
Temperature (?C)
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Alkali Zeolites
Alkali metals-exchanged zeolites are
bi-functional
For a compound
PpQqRr
Sint (SpP SqQSrR) 1/pqr S intIntermediate
Electro negativity
Tsou .J, L. Pinard, P. Magnouxb, J.L. Figueiredo,
M. Guisnet. Appl. Catal. B
Environ. 46 (2003) 371379
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Oxidation of Methyl iso butyl ketone
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Advantages
high surface area Metal-support interaction
is high Exchangeable with cations Disadvantages
coke formation formation of by-products
less affinity towards VOCs.
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MCM-41 (Mobil Crystalline Material)
Preparation of fluorinated MCM-41
SiO2 NaOH CTMABr Acid H2O (1 0.54
0.50 0.34 100)
NaOH SiO2 H2O
Stirring, 80 C
Gel
Si-OH Hydrophilic Si-F
Hydrophobic
Vigorous stirring, 2h. 40 HF (pH 10.5)
CTAB
Crystallization,36h. Autogenous pressure Wash
with H2O
Calcined, air,550C,10h
Fluorinated MCM-41
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FTIR spectrum
2 Pt/F-MCM-41 ( M1) 0.6 Pt/F-MCM-41 (M2) 2
Pt/MCM-41(Si/Al15) (M3) 2 Pt/ZSM-5
(Si/Al25) (M4)
M4
M3
M2
M1
The order of activity for toluene
oxidation Above 200C M1 gt M2 M3 gt M4 Below
200C M1gt M2 M3 M4
Toluene oxidation
M2
M1
M3
M4
Xia. Q.H, K. Hidajat, S. Kawi. Catal. Today 68
(2001) 255262
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Perovskites
Citric acid sol-gel method La(NO3)3.6H2O
Sr(NO3)2 Mn(NO3)3.4H2OCitric acid
Ethylene Glycol
Heated ,90?C
Gel
Dried and Calcined in 600?C Air
La0.8Sr0.2MnO3x
Aubé. V. B, J. Belkouch, L. Monceaux . Appl.
Catal. B Environ. 43 (2003) 175186.
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La0.8Sr0.2MnO3x
Total conversion()
Surface area of catalyst 20 22 m2/g
Oxidation of hydrocarbons
Temperature(?C)
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La0.8Sr0.2MnO3x
Total conversion()
Oxidation of oxygenates
Temperature(?C)
Advantage This catalyst is more active than
Au/Fe2O3 and MnO2 exceptfor ethanol and ethyl
acetate Disadvantages Poor surface area
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Hydrophobic supports
Pt/h-BN
Pt/?-Al2O3
Preparation
Hexagonal-Boron Nitride
Wetness impregnation method

TEM
SEM
h-BN
Pt was estimated by wet chemical method.
Surface area 0.3 Pt/h-BN 70 m2/g,
0.3 Pt/?-Al2O3 99 m2/g
Wu. J. C. S, Z. A. Lin, J.W. Pan, M. H. Rei.
Appl. Catal. B Environ. 219 (2001) 117124.
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XPS spectra
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h-BN
Shift in peak position of B 1s means the
presence of B-O interaction in h-BN. The Pt can
be anchored well on oxygen
190.8
Crystalline h-BN
190.1
Binding energy (eV)
Pt/h-BN
Presence of Pt(0) in h-BN supported catalyst is
more active than PtO2 . Peak around 500 C in
Al2O3 supported system is due to Pt aluminate.
Pt/Al2O3
TPR profile
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Pt/h-BN Ist run 2nd run
Oxidation of gasoline vapour
1st run 2nd run
As no. of run increases activity also increases
in Pt/h-BN catalyst. But decreases in the case
of Pt/?-Al2O3 catalyst Formation of PtOx on
surface on increase of the run is taking place
in case of Pt/h-BN Pt aluminates is formed in
the case of Pt/?-Al2O3
Pt/?-Al2O3
Ist run 2nd run 3rd run
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Pt/h-BN pre-treated with N2 is less active than
one treated with Air Pt oxides are active than
Pt metal
Air, 300 ?C N2, 300 ?C
Stability of catalyst
Stability of Pt/h-BN is more than that of Pt/?-
Al2O3.
Pt/h-BN
Advantage No phase transition in h-BN even at
800 ºC
Pt/?-Al2O3
Disadvantage Poor surface area
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Pt/Active
Carbon 0.3Pt/AC800 0.3Pt/AC400 and
0.3Pt/AC800HF 0.3Pt/Al2O3 Preparation Wet
impregnation method



Oxidation of benzene
Pt/AC800
Pt/AC800HF
Total conversion()
Pt/AC400
Pt/Al2O3
Adsorption of BTX
Temperature(?C)
Benzene
Total conversion()
Xylene
Toluene
Temperature(?C)
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Surface area
CH-/C2H- .73
CH-/C2H- .25
CH-/C2H- .38
AC400
AC800
AC
Secondary Ion Mass Spectrum
CH-/C2H- ? 1/Graphiticity
Graphiticity ? Hydro phobicity
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Stability of catalyst
Pt/AC800
,165?C
Even after 100 h, activity of the catalyst is
constant.
Total conversion()
O2
VOC
O2
CO2 H2O
Time on stream (min)
CO2 H2O
O
O
O
CH3-CH2-CH3
O
Mechanism
O
O
CH-CH-CH
Pt
CHCH-CH-CH
Spill-over mechanism
Disadvantage Poor thermal stability
Active carbon support
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• Summary
• Among other methods available the catalytic
• oxidation is efficient and inexpensive
• Metal oxide catalysts are important due to
• the low cost and thermal Stability
• Zeolites with high Si/Al ratio or exchanged with
• alkali cations can be effectively utilized
• High surface area perovskite materials can be
• prepared and utilized
• Fluorinated MCM-41 catalyst showing good
• features for VOC oxidation

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• h-BN supported catalyst can be a potential
  candidate
• for VOC oxidation
• Even though active carbon supported catalysts
  possess good activity, they can not be used at
  temperatures greater than
• 200 C.

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Thank you