Deposition of a soot catalyst on a metallic DPF filter, using an aqueous sol gel dipcoating...
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Transcript of Deposition of a soot catalyst on a metallic DPF filter, using an aqueous sol gel dipcoating...
Deposition of a soot catalyst on a metallic DPF filter, using an aqueous sol gel dipcoating
technique.
Els Bruneel, N. Van de Velde …S. Hoste…….., I. Van DriesscheGhent University,
Dep. Inorganic and Physical ChemistryKrijgslaan 281 – S3, 9000 Gent, Belgium
Diesel soot filterElectric regeneration
Bekaert
Feasability study: coating of porous metallic
filter:
(De-NOx) soot oxidation
“Development of a high efficiency diesel particulate filter medium and an adequate coating technology for catalysts”
Pourous filter: three layer mediumFeCralloy: high temperature resistance
Engine design
Fuel technologies
Exhaust after treatment• Ceramic based filters
Wall flow monolithsCeramic fibre filtersCeramic foams
• Metal based filtersSintered metal powderMetal foil based filtersMetal fibre filters
Add some pictures..
Diesel soot filter
Coarse fitler Fine filterLoaded Soot-free
Bekaert
“Development of a high efficiency diesel particulate filter medium and an adequate coating technology for catalysts”
Area: 4 m2/gPress. drop: 670 l/cm2
1 2 3
Pourous filter: three layer mediumFeCralloy: high temperature resistance
UGENT: Aqueous sol-gel chemistry solution composition :
M-salts : inorganic, alkoxides
Solvent : H2O (> 80 v%), EtOH, iPrOH, HOAc ,...
Modifiers : pH adaptation, surfac-tant, polymer
Complexing agents : TEA, EDTA, CA, MEA, DEA
Gelation, T≤60°C
Deposition on substrates by dipcoating, printing
Mn+ Mn+Mn+Mn+Mn+
H2O
Mn+
Mn+Mn+
Mn+
Heat
trea
tmen
t und
er
cont
rolle
d at
mos
pher
e
Cheap, environmentally benign
6
(1) Coating techniquesol gel dipcoating
(2) Catalyst choose catalyst/ synthesis deposition and analysis
(3) Predeposition of Buffer layerchoose buffer layer/synthesisdeposition and analysis
Overview
Diesel soot catalyst
Selection, deposition and improvement
150 200 250 300 350 400 450-1E-10
-5.00000000000003E-11
-3.10192729707385E-25
4.99999999999997E-11
9.99999999999997E-11
1.5E-10
No catalystCu/Mo cata-lyst
Temperature °C
Arb
itra
ry U
nit
s
CO2CO2
oxidation without catalyst
oxidation with catalyst
± 100 °C
NO
• Starting point: Cu and Mo• Selection of precursors:
NaMoO4 , CuCl2 or Cu(NO)3 , KClMolar Ratio Cu/ Mo = 2/1
• Preparation of a Sol gel system addition of citric acid to form stable complexes.
Improvement of the catalyst:better temperature stability remove all chloridesreduce foaming increase activity
Deposition:sol preparationchoice of complexing agentstemperature programm
Diesel soot catalyst
Selection, deposition and improvement
Precursor salts citric acid
pH = 7NH4OH
aqueous precursor-solution
geldrying at 60 °C
Catalyst
Thin layer
thermal treatment
Catalyst
Powder
Dip coating
Gel on filter
Diesel soot catalyst
Thermal stability, improves with addition of Ce
100
95
90
85
80
75
70
m%
1000800600400200
temp (C)
10.441 Ce-ox kat (50/50) 10.442 Ce-ox kat (60/40) 10.439 Ce-ox kat (70/30) 10.438 Ce-ox kat (80/20) 10.453 Ce-ox kat (90/10) 10.447 oxide kat (100/0)
50/50
80/20
Thermal Stability
Ce CuMo catalyst
100% CuMo
TGA mass%
Cu Mo KCl Ce
2 1 2 0 5
100
80
60
40
20
0
massa %
tg
a
50403020100
tijd (min)
100x10-12
80
60
40
20
0
ou
tp
ut m
assasp
ectr
44
34
33
45644346
Cu-Mo Catalyst
Cu-Mo-Ce Catalyst
100
80
60
40
20
0
massa %
tg
a
403020100
tijd (min)
100x10-12
80
60
40
20
0
ou
tpu
t masasap
ectro
mete
r
44
34
3933
Thermal Stability, TGA-MS
m=44
m=44
TGA mass
TGA mass
Thermal Stability
0 100 200 300 400 500 600 700 800 900 100010
30
50
70
90
Cu/Mo/Ce Without Cl
Cu/Mo/Cl no Ce
With cerium, no Cl
Cu Mo KCl Ce
2 (CuCl2) 1 2 -
2 (Cu(NO3)2 ) 1 - 0.8
Catalytic activity
POWDER
TGA analysis: mass loss vs temperatureDTA : exothermic oxidation reaction
Coated filterFlow through reactor: temperature of
soot combustion : thin film on substrate+ de-NOx test
10% O2 in Ar (NOx)
5 x filter4 x 0,01 g roet
massaspectrometerO2 , Ar, KWS, CO2
100
80
60
40
20
mass
a %
800600400200
temp (°C)
1.0
0.8
0.6
0.4
0.2
0.0
tem
p d
iff
501 °C
TGA/DTA
roet
Synergistic effectCatalytic activity
Al2O3
CeO2
Catalyst Cu/Mo
Soot
soot400
450
500
Soot
com
bust
ion
tem
p.
(°C
)
TGA/DTA : Fixed Ratio:
380
400
420
440
460
480
500
520
Cu/Mo/KCl Cu/Mo/Cl and CeO2 Cu/Mo/Ce Soot Linear (Soot )
Max
in D
TA s
igna
l (°C
)Catalytic activity
Catalyst (Cu/Mo/Ce/Cl)
Soot Inert Al2O3
1 2 3
Addition of Ce to a Cu-Mo catalyst
‣Thermal stability ‣Catalytic acitivity ‣Thin layer ??
Diesel soot catalyst
Deposition of the catalyst on a filter
Pretraetment of the substrate was necessary in order to increase the wettibilit
Chemical etching+ ultrasonic treatment+ degreasing
Contact angle measurements
Before treatment Sufficient wettingFeCralloy exhibits low wettability
cleanedsubstrate
solution
liquidprecursor-layer
T>500°C, in air
Thin film
liquidprecursor-layer
Deposition of the catalyst on a filter
Dipcoating
Ce-citrate => autocombutison process Foaming- restriction on the amount of Cerium
in the catalyst- addition of anti-foaming agent
(Si-suspension ©Basildon)
Deposition of the catalyst on a filter
High Ce loading low cerium loading Cu / Mo / Ce
2 / 1 / 0.8
Addition of Ce to a Cu-Mo catalyst
‣Thermal stability ‣Catalytic acitivity ‣Thin layer
‣Corrosion protection ??
Diesel soot catalyst
Choice based on :
- thermal expansion coefficient- thermal stability- solubilty of precursors- temperature of synthesis - chemical properties
- reaction with filter material : unknown- reaction with catalyst: positive effect
Buffer layer : Introduction
CeO2
Applications (other than bufferlayer for catalyst)- Buffer layer for HTS:- Fuel cells- Catalyst- Anti-oxidant (nanoparticles)
Buffer layer CeO2 : precursor solution (1)
Aqueous solutionMetal precursor : Ce(NO3)3 Complexing agent : citric acidpH adaptation : NH4OH
Specific modifications are necessary :
Anti –foaming agents SpeedTemperature programmConcentration
Before
After
precursorsolution
gel oxidecompound
27
Buffer layer CeO2 : precursor solution
Chemical composition precursor solution
Concentration of free Ce(III) and com-plexant based on : theoretic speciation calculations from
complexometry as a function of pH further refinement through trial and error
Uitbreiding van Nigel???
Ce:c.a.
Ce:c.a.
Ce:c.a.
1:1
1:2
1:3
0 2 4 6 8 10pH pH pH pH pH pH
Ce:citric acid (1:1)/(1:2)/(1:3) pH = 0 – 10
Search for a good anti-foaming agent Glycol, butanol, octanol and silicon
suspension: APTS (aminopropyltriethoxysilane)
Buffer layer CeO2 : precursor solution
Ce(NO3)3 citric acid
additives
aqueous precursor-solution
gel
drying at 60 °C
CeO2
thermal treatment
amorphous citrate gel method
Corrosion protection: analysisVisual inspectionNot treated 0,1 mm /min
10 mm/min 20 mm/min
Higher dipping rate: More materialWORSE PROTECTION?
Samples
coated in Ce-nitrate/ Citric acid gel
+
glycol and siliconsuspension
Electrochemical analysis
By Johan Van Brabant (Bekaert)
Determination of corrosion current Analysis of Variance
Corrosion protection: analysis
• Dipping speed : 0.1 to 60 mm/min• Additives
• non• 10 vol% glycol• 10 vol% glycol 10 vol% Sil emulsion
• High temperature process• Slow heating rate• Fast heating rate
2445643N =
VAR00007
60.0040.0020.0010.005.001.00.10
Mean +
- 1
SD
VA
R00004
400
300
200
100
0
Dipcoating speed
With higher speed, corrosion current is higher,Quality is worse
Corrosion protection: analysisC
orr
osi
on
curr
ent
1099N =
VAR00005
3.002.001.00
Mean +
- 1
SD
VA
R00004
300
200
100
0
Corr
osi
on c
urr
ent
Sol Ce/CA Ce/CA + Glycol +
siliconensusp
+ glycol
Differences, concerning the additives
Corrosion protection: analysis
Buffer layer CeO2 : morphology
Optical microscopy
50 mm 50 mm
Electron microscopy
Ce EDX
Top view Back view Cut
36
Diesel soot catalyst
Results
CeO2 buffer layer:air permeability: 88 % good590 l/dm2.min
Cl-free Ce-containing catalystair permeability: 40% improvement required274 l/dm2.min
10% O2 in Ar
5 x filter4 x 0,01 g roet
massaspectrometerO2 , Ar, KWS, CO2
Flow Through reactor: activity on coated filter
Catalytic activity
Filter + Drop in combustion temperature( O2 signal )
No Catalyst - C
Cu/Mo/KCl -50 °C
Cu/Mo / Ce -80 °C
3 layer filter medium(13*13 cm2)
corrosion free combustion temp reduction >100 °C heavy duty diesel oxidation at: 400 - 420 °C air permeability
Conclusion
Besluit
Vlakke filter kan gecoat wordenna cleaning , en afzetten met bufferlaag,traag dipcoaten
(1mm/min)
probleem van corrosie: opgelost door : goede bufferlaag verwijderen Cl uit kat
probleem thermische stabiliteit katalysatoropgelost door verwijderen Clof gebruik van hoeveelheid Ce
probleem schuim: bij bufferlaag: of Ce(NO3)3 + CA + Si-suspensie of Ce(NO3)3 + CA + Tex 1 of Ce(NO3)3 + CA + APTS of Ce(NO3)3 + APTS
bij katalysator:Si-suspensie indien Cl aanwezig is(?????-Cl en -Ce, APTS?????)
0,00
5,00
10,00
15,00
20,00
25,00
0,00 5,00 10,00 15,00
Ico
rr(m
A)
blootgesteld oppervlak(cm2)
blanco zonder plooi
blanco met plooi
With a plead, the corrosion current is higher
Corrosion protection: analysis
Corr
osi
on c
urr
ent
Surface area of sample (cm2)
Composition of the catalyst
Based on XRD and XPS
- CuO (XRD)- NaCl (XRD)- Mo6+ (XPS)
If Ce is present: CeO2 (XRD)
Wat we weten:vereist: bufferlaag
‣Analyse methode voor kwaliteit van de bufferlaagmethode : elektrochemisch
‣Analyse werking katal. : TGA‣Afzetten:
Snelheid: trager -> hogere kwaliteit // vlugger -> meerSol: additieven van belang
+ glycol: goed tegen schuim, maar mindere kwaliteit
+ sil en + glycol: beter dan + glycol probleem : batch II van siliconenen suspensie
is verschillendTemperatuursproces: geen verschil tussen de 2
programma’s
XPSCu: BE typisch voor CuO, + eventueel andere faseO: in CeOxide kat: 1 piek in oxide kat en Chloride kat: 2 pieken
bij hogere BE, eventueel CarbonatenCe: in Ce oxide kat: typisch mengsel van Ce III en Ce IV mengsel door reductie van Ce IV tijdens de XPS meting.
Mo: Relatief lage BE (MoCl5 of molybdaten)C: 1piek
0
100
200
300
400
500
600
700
800
2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
2 theta
cou
nts
CeOx kat 10.248
oxide kat 10.231
chloride kat 10.33
XRDHoofdzakelijk:
KClCuONaClMo: ??? MoO3, MoCl5, mogelijks Molybdaten en
mengmolybdatenIn Ce -oxide kat ook: CeO2
Wat is de rol van Ce bij de thermische stabiliteit van de katalysator ?
Ce-oxide katalysator
Schuimvorming, kroes
Ce-nitraatCitroenzuur+ NH4OH => pH = 7
Na2MoO4
KClCuCl2+ NH4OH => pH = 7
Mengen, gelleren, calcineren
50/50 Schuim60/40 Schuim70/30 Schuim80/20 Geen schuim90/10 Geen schuim100/0 Geen schuim
47
Processing requires good wettability.This depends on :
- substrate (surface tension)
- sol (surface tension, viscosity,…)
cleaning involves : - degreasing - ultrasone step - etching
Buffer layer CeO2 + catalyst layer
Pretreatment of the substrate Processing
cleanedsubstrate
Precursorsolution
liquidprecursor-layer
A. Dipcoating
B. Thermal treatment
liquidprecursor-layer
T>800°C, in air
crystalline CeO2-film