1. 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 Driessche
Ghent University,
Dep. Inorganic and Physical Chemistry
Krijgslaan 281 – S3, 9000 Gent, Belgium

2. Feasability study: coating of porous metallic filter:
“Development of a high efficiency diesel particulate filter medium and an adequate coating technology for catalysts”
Feasability study: coating of porous metallic filter:
(De-NOx) soot oxidation
Diesel soot filter
Electric regeneration
Situering: to control diesel emissions exhaust 3 technologies are important:
Engine design techniques
diesel fuel related technologies:
AND: exhaust after treatment
goal=: to develop a high efficiency diesel particulate filter medium for off road diesel vehicles.(in eerste instantie werd gekeken naar heavy duty vehicles (busses, trucks) dan naar off road diesel engines ( locomotieven, marine, tractors) en eventueel naar passager cars andd low duty commercial vehicles.
Within the project Bekaert company developped an efficient filter medium
That is resistent against thermal mechanical and chemiscal corrosion and excellent characteristics concerning efficiency.
It is composed of three layers of FeCralloy short fibres, each with different fibre sizes and pore diameters. These are sintered together to obtain a filter with a variation in porosity
The top layers , or inlet, has the highest porosity and pore size , the outlet exhibits the lowest porosity and pore size.
The filter exhibits a specific surface area of 4 m2/g. And a small pressure drop of 670 l/cm2.
They start from short fibres , which have a curly structure. And via a mathematical simulation model a multi-stage filter is designed,
Suitable for capturing soot. : the task of the filter is to phisically capture the soot particles.
In the initial setup regeneration of the filter is possible with electric heating. (Daarom gebruiken ze FeCralloy, omdat dit tegen zeer hoge temperaturen bestendig is. Bij elektrisch verwarmen kunnen de piektemperaturen hoog oplopen).
As the dep. Of inorganic chemistry at UGent/ Scripts is very active in the design
Of new ways to deposit thin films from aqueous solutions,
We were asked to deposit a catalyst on this filter.
This catalyst should lower the oxidation temperature of the captured soot. Which would allow to use cheaper or better processable metal-alloys., energy can be saved. (: electric heating is no longer necessary or heating can be reduced.)
Second goal: in principle :
showing that it is possible to coat the filter with a thin layer of ceramic material, throughout the whole filter, without destroying the filter and without blocking the pores
Opgelet: Texaco heeft expleciet gevraagd op geen enkele manier vernoemd te worden.
Bekaert
Pourous filter: three layer medium
FeCralloy: high temperature resistance

3. Exhaust after treatment Ceramic based filters Wall flow monoliths
Engine design
Fuel technologies
Exhaust after treatment
Ceramic based filters
Wall flow monoliths
Ceramic fibre filters
Ceramic foams
Metal based filters
Sintered metal powder
Metal foil based filters
Metal fibre filters
Situering: to control diesel emissions exhaust 3 technologies are important:
Engine design techniques
diesel fuel related technologies:
AND: exhaust after treatment
Different materials have been tested so far as potential DPF materials
In the global particulate filter market, ceramic filtes are most widely spread.
But metal based filters have the benefit of strength and heat properties of metals. : low thermal stresses and good heat conductivity.
And are thus resistant against thermal and mechanical shock.
Among these the metal fibre filters do have a high backpressure performance and ( en plus) exhibit a higher surface area. (then the other metallic filters) Can hav a high porosity of over 95¨% are easy to make and thus are more cost effective then the sintered metal powder and the metal foil based filters
Add some pictures..

4. Coarse fitler Fine filter Loaded Soot-free
“Development of a high efficiency diesel particulate filter medium and an adequate coating technology for catalysts”
Coarse fitler Fine filter
Loaded Soot-free
Within the project Bekaert company developped an efficient filter medium
That is resistent against thermal mechanical and chemiscal corrosion and excellent characteristics concerning efficiency.
It is composed of three layers of FeCralloy short fibres, each with different fibre sizes and pore diameters. These are sintered together to obtain a filter with a variation in porosity
The top layers , or inlet, has the highest porosity and pore size , the outlet exhibits the lowest porosity and pore size.
The filter exhibits a specific surface area of 4 m2/g. And a small pressure drop of 670 l/cm2.
They start from short fibres , which have a curly structure. And via a mathematical simulation model a multi-stage filter is designed,
Suitable for capturing soot. : the task of the filter is to phisically capture the soot particles.
In the initial setup regeneration of the filter is possible with electric heating. (Daarom gebruiken ze FeCralloy, omdat dit tegen zeer hoge temperaturen bestendig is. Bij elektrisch verwarmen kunnen de piektemperaturen hoog oplopen).
Bekaert
Area: 4 m2/g
Press. drop: 670 l/cm2
Diesel soot filter
Pourous filter: three layer medium
FeCralloy: high temperature resistance

5. As the dep. Of inorganic chemistry at UGent/ Scripts is very active in the design
Of new ways to deposit thin films from aqueous solutions,
We were asked to deposit a catalyst on this filter.
This catalyst should lower the oxidation temperature of the captured soot. Which would allow to use cheaper or better processable metal-alloys., energy can be saved. (: electric heating is no longer necessary or heating can be reduced.)
Second goal: in principle :
showing that it is possible to coat the filter with a thin layer of ceramic material, throughout the whole filter, without destroying the filter and without blocking the pores
Opgelet: Texaco heeft expleciet gevraagd op geen enkele manier vernoemd te worden.

6. UGENT: Aqueous sol-gel chemistry solution composition :
M-salts : inorganic, alkoxides
Deposition on substrates by dipcoating, printing
Solvent : H2O (> 80 v%), EtOH, iPrOH, HOAc ,...
Gelation, T≤60°C
Complexing agents : TEA, EDTA, CA, MEA, DEA
H2O
Heat treatment under controlled atmosphere
Modifiers : pH adaptation, surfac-tant, polymer
Mn+
Mn+
Mn+
Mn+
Mn+
Mn+
Mn+
Mn+
Mn+
Cheap, environmentally benign 6

8. Overview (1) Coating technique sol gel dipcoating (2) Catalyst
choose catalyst/ synthesis
deposition and analysis
(3) Predeposition of Buffer layer
choose buffer layer/synthesis
First a coating technique should be selected
We choose sol gel dipcoaten from an aqueous solution for several reasons:
- it is environmentally friendly
- upscaling is ‘easy’
- no high vaccuum is needed
- the proces of dipping in a solution is one of the only which allows to reach the inner part of the filter.
in many coating techniques to deposit thin layers (CVD, sputtering), material comes from one direction,
and it is very hard to avoid pore blocking
- with dipcoating a high reproducibility can be obtained,
- a thin layer can be deposited, so that no obstruction of the pores is generated. and: additionally: when a thin layer is deposited the chances for delamination deminish
: a good adhesion is a prerequisite
- Because we start from a solution, we can obtain in depth coating: not only the outer geometry of the filter is coated.
Opmerking: metaal vezels gedragen zich niet hetzelfde als metaal folie. Gekende pre-treatment technieken, zoals het groeien van een ‘TGO= thermically grown oxide’ laag blijkt niet te werken op de vezels. : op de folie kun je een laag Al2O3 groeien, door de folie op te warmen, het alumina komt dan uit de folie. Bij vezels lukte dit niet.
(maar het zou kunnen dat ze intussen wel gevonden hebben hoe dit haalbaar is).

9. Selection, deposition and improvement
Diesel soot catalyst
Selection, deposition and improvement
Starting point: Cu and Mo
Selection of precursors:
NaMoO4 , CuCl2 or Cu(NO)3 , KCl
Molar Ratio Cu/ Mo = 2/1
Preparation of a Sol gel system
addition of citric acid to form stable complexes.
A catalyst was selected.
We choose for a Cu and Mo containing system
Which has shown to be an active soot catalyst
And de-NOx activity was observed.
Then : select a composition and prepare a sol
That allowes:
- deposition of thin layer, that can be deposited without pore blocking
- thermally stabel in the temperature range used
- does not destroy the filter
Ter info: deNOx werd nooit gemeten na de veranderingen in de samenstelling, omdat de flow through reactor werd afgebroken.
De katalysator in deze figuur is een Cu/Mo/KCl kat, uit een solgel proces (en met een bufferlaag van CeO2)
During the test, temperature was increased. And a gas mixture of 90% Ar, 10 % O2 was preheated and flowed over the filter at a rate of 75mL/min. To illustrate deNOx properties, 100 ppm NO was added to the mixture.)

10. Selection, deposition and improvement
Diesel soot catalyst
Selection, deposition and improvement
Improvement of the catalyst:
better temperature stability
remove all chlorides
reduce foaming
increase activity
Deposition:
sol preparation
choice of complexing agents
temperature programm
A catalyst was selected.
We choose for a Cu and Mo containing system
Which has shown to be an active soot catalyst
And de-NOx activity was observed.
(maar wij hebben daar niet veel op gemeten, alleen bij de eerste testen, toen de reactor nog werkte)
The select a composition and prepare a sol
That allowed :
- deposition of thin layer, that can be deposited without pore blocking
- thermally stabel in the temperature range used
- does not destroy the filter

11. aqueous precursor-solution
Diesel soot catalyst
Precursor salts
citric acid
pH = 7
NH4OH
aqueous precursor-solution
gel
drying at 60 °C
Catalyst
Thin layer
thermal treatment
Dip coating
Gel on filter
Catalyst
Powder

12. Thermal stability, improves with addition of Ce
50/50
80/20 Ce
CuMo catalyst
TGA mass%
100% CuMo
One of the problems with the Cu-Mo- KCl catalyst is its’ thermal stability.
We could improve this, with the addition of cerium to the catalyst.
Without cerium a mass los is observed starting around 550°C.
Addition of cerium, (even as little as 10%) shifts this mass loss towards higher temperatures.
The more Cerium added the smaller the mass loss, but the first mass % have the biggest impact. Cu Mo
KCl Ce 2 1
Thermal stability, improves with addition of Ce

13. Thermal Stability, TGA-MS
Cu-Mo
Catalyst
TGA mass
m=44
Cu-Mo-Ce Catalyst
It is not entirely clear what is happening, but
In the mass signal from the evaporated gasses ,
accompagnying the mass loss in the Cu-Mo catalyst we see a signal of mass 44, (waarschijnlijk CO2 of N2O) (superimposed on the background signal)
this signal dissapears after Ce addition.
Second: a mass loss starting around 800 °C
Allocated to the evaporation of KCl (which is melting at 770 °C).
Therefore chlorides were omitted from the catalyst.
TGA mass
m=44

14. Thermal Stability With cerium, no Cl Cu Mo KCl Ce 2 (CuCl2) 1 2 -
Omitting the Chlorine from the catalyst:
= no addition of KCl , and replacing CuCl2 with Cu(NO3)3
Strongly improves the thermal stability.
The TGA curve is now practically flat. Cu Mo
KCl Ce
2 (CuCl2) 1 2 -
2 (Cu(NO3)2 )
0.8

15. Addition of Ce to a Cu-Mo catalyst
Diesel soot catalyst
Addition of Ce to a Cu-Mo catalyst
Thermal stability 
Catalytic activtiy ??
So far, we have a catalyst
Which has good thermal stability
Due to addition of Cerium and ommitting the Cl
BUT what did this do with our Catalytic activity???

16. Catalytic activity TGA/DTA roet 501 °C POWDER
TGA analysis: mass loss vs temperature
DTA : exothermic oxidation reaction
Coated filter
Flow through reactor: temperature of soot combustion : thin film on substrate
+ de-NOx test
TGA/DTA
10% O2 in Ar
(NOx)
roet
501 °C
5 x filter
4 x 0,01 g roet
The Catalytic activity is used in two different ways.
For powder samples:
TGA / DTA is used in a loose contact mode to evaluate the activity of the catalyst powder.
(The top of the DTA curve is choosen as a point of comparison)
Influence of the composition : next slides)
For coated filters, a flow through reactor was used. (more details furhter on)
massaspectrometer
O2 , Ar, KWS, CO2

17. Catalytic activity Al2O3 CeO2 Catalyst Cu/Mo Soot
Synergistic effect
Al2O3
CeO2
Catalyst Cu/Mo
Soot
The Influence of quantities is illustrated in this graphic representation
In the experement, we have a mixture of 2 parts of soot and 4 parts of inert Al2O3
It shows that as the soot itself decomposes around °C,
Replacing the inert alumina with Cu/Mo containing catalyst , results in a decrease of the combustion temperature,
Then replacing more of the Al2O3 with increasing amounts of CeO2 , results in a further reduction of the combustion temperature, showing that in this setup the CeO2 is not an inert phase , but has some kind of synergsitic efect on the soot combustion.
The origen of this effect is the oxygen storage capacity of CeO2:
CeO2 captures oxygen (as CeO2) on moments when there is plenty of oxygen in the environment, while it gives back the oxygen as (CeO2-x) on moments there is not much oxygen in the environment . In this manner it can promote the conversion of CO into CO2.
Finally, an experiment with soot and CeO2, shows that CeO2 itself is not a good catalyst.
Soot combustion temp. (°C)

18. Catalytic activity TGA/DTA : Fixed Ratio: Catalyst Soot Inert Al2O3 1
(Cu/Mo/Ce/Cl)
Soot
Inert Al2O3 1 2 3
With a fixid ratio of catalytic material towards the soot
We can evaluate how these
changes in composition affect the combustion temperature
In the first composition The catalyst was still containing chlorides and no Ce
Replacing a part of this catalyst with CeO2, (keeping the Soot / catalyst ratio fixed) a clear reduction in combustion temperature was observed.
From °C towards 430 °C
Omitting Chlorine from this mixture did not alter the combustion temeperature.
Showing that we do not need this KCl;

19. Addition of Ce to a Cu-Mo catalyst
Diesel soot catalyst
Addition of Ce to a Cu-Mo catalyst
Thermal stability 
Catalytic acitivity 
Thin layer ??
So far, we have a catalyst
Which has good thermal stability
Due to addition of Cerium and ommitting the Cl
The catalytic activity has been improved,
But can we now make a thin layer ???

20. Deposition of the catalyst on a filter
Pretraetment of the substrate was necessary in order to increase the wettibilit
Contact angle measurements
Chemical etching
+ ultrasonic treatment
+ degreasing
A pretraetment was necessary, to allow wetting of the FeCralloy with the aqueous solution.
In these pictures we see what happens ,using a FeCralloy foil.
Before treatment, a high contact angel is measured
After chemical etching, ultrasonic treatment and degreasing, the wetting sufficiently improved
And we can proceed to the actual dipping proces.
Before treatment Sufficient wetting
FeCralloy exhibits low wettability

21. Deposition of the catalyst on a filter
Dipcoating
liquid
precursor-layer
cleaned
substrate
solution
T>500°C, in air
liquid
precursor-layer
Thin film

22. Deposition of the catalyst on a filter
Ce-citrate => autocombutison process Foaming
- restriction on the amount of Cerium
in the catalyst
- addition of anti-foaming agent
(Si-suspension ©Basildon)
Decomposition of the ceriumcitrate, is an autocombustion reaction and
Results in excessive foam formation
To deal with this problem
The amount of cerium is restricted to 0.8 Ce (relative to 2 Cu and 1 Mo atom%)
Fortunately, ( as seen in slide 9, you don’t need too much Cerium to have a positive effect on the thermal stability).
In addition an anti foaming agent is added to the sol.
On the left a filter coated in a sol with high Cerium loading, on the right low cerium loading. (but enough to be thermally stable, and catalytically active)
But CORROSION is observed!
High Ce loading low cerium loading Cu / Mo / Ce
2 / /

23. Deposition of the catalyst on a filter
Corrosion !

24. Addition of Ce to a Cu-Mo catalyst
Diesel soot catalyst
Addition of Ce to a Cu-Mo catalyst
Thermal stability 
Catalytic acitivity 
Thin layer 
Corrosion protection ??
So far, we have a catalyst
Which has good thermal stability, catalyst is active, a thin layer is deposited
But we need to protect our substrate with a buffer layer

25. Buffer layer : Introduction
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
CeO2
Applications (other than bufferlayer for catalyst)
- Buffer layer for HTS:
Fuel cells
Catalyst
Anti-oxidant (nanoparticles)
CeO2 was choosen as a bufferlayer because it has a high thermal expansion coeficient,
Thus minimizing thermal stresses , (which would appear if the substrate and the buffer layer have a big difference in thermal expansion)
CeO2 is thermally stabele, water soluble inorganic salts are available,
CeO2 can be synthesized at moderate temperatures ( °C)
As the addition of Cerium to the catalyst had a positive effect we don’t expect any negative evolution by using CeO2 as a buffer layer.
CeO2 is chemically rather inert, and thus no or only moderate reaction with the FeCralloy is expected.

26. Buffer layer CeO2 : precursor solution (1)
gel
oxide
compound
Aqueous solution
Metal precursor : Ce(NO3)3
Complexing agent : citric acid
pH adaptation : NH4OH
Specific modifications are necessary :
Anti –foaming agents
Speed
Temperature programm
Concentration
Before
After

27. Chemical composition precursor solution
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
Ce:citric acid (1:1)/(1:2)/(1:3)
pH = 0 – 10
Ce:c.a.
1:1
1:2
1:3 2 4 6 8 10 pH
The same story….
Search for complexing agents,
Hier iets over het uitgebreidere werk van Nigel, indien niet, kan ik ook nog wel uitbreiden.
In the end we choose citric acid,
determined good ratios of Ce / complexant;
This can be done by trial and error or based on stability constants
Uitbreiding van Nigel???

28. aqueous precursor-solution
Buffer layer CeO2 : precursor solution
Search for a good anti-foaming agent
Glycol, butanol, octanol and silicon suspension: APTS (aminopropyltriethoxysilane)
amorphous citrate gel method
Ce(NO3)3
citric acid
additives
aqueous precursor-solution
gel
drying at 60 °C
CeO2
thermal treatment
As , again , we have to deal with the excessive foaming due to the autocombustion proces during decomposition of the Ce-citrate complex.
Several anti foaming agents were evaluated.
Such as Glycol, butanol, octanol, aminopropyltriethoxysilane and Basildon silicone suspension.
Due to the tensio active properties of these substances, foam formation is reduced., but the quality of the bufferlayer had to be good,
Sealing the substrate completely before it comes into contact with the catalyst sol.
Some of them could be easily ruled out by a visual inspection, however…

29. Corrosion protection: analysis
Visual inspection
Not treated
0,1 mm /min
10 mm/min
Samples
coated in Ce-nitrate/ Citric acid gel +
glycol and siliconsuspension
20 mm/min
Visual inspection can alos be tricky
One can make a visual inspection of the coated wires,
From which one can observe that, the higher the dipcoating rate, the more material is on the fibres/
As seen here for samples:
coated in Ce-nitrate/ Citric acid gel with the addition of glycol and siliconsuspension,
After heat treatment
But it turned out that the fast-coated samples were more sensitive corrosion then the slow coated samples !!
So what happened, visual inspection clearly was not sufficient
Higher dipping rate: More material
WORSE PROTECTION?

30. Corrosion protection: analysis Electrochemical analysis
Determination of corrosion current
Analysis of Variance
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
For more profound analysis the material was analysed by linear sweep voltametry in a corrosive solution of CuCl2 (0,625 M). The corrosion current (Icorr) is taken as a point of comparison.
Because of the big spread in results, analysis of variance was used to evaluate the influence of the dipcoating speed, the thermal treatment and the use of additives during synthesis, six series of samples were synthesized
Cleaned filter material is coated at speeds varying from 0,1 to 60 mm/min. The used sols were a citric acid/ Ce-nitrate solution with a) no additives b) with addition of 10 vol % glycol, c) with addition of glycol and silicone emulsion.
The dip-coated substrates and filters were dried at 60 °C, for 60 minutes to convert the liquid layer to a gel. Subsequently, the coated substrates were transferred to a muffle furnace and a high temperature proces was performed,
Either with a fast heating rate (towards 250 °C for 60 °C and subsequently towards 800 °C for 120 minutes)
Or a slow heating rate (to 250 °C with a rate of 1 °C/min, then to 400°C at 0,5°C/ min in order to cross the autocombustion regime slowly. Subsequently the temperature was kept constant at 400 °C for 1h and then raised at 1 °C/min towards 800 °C and kept constant for 2h for the crystallisation process)
No statistical meaning full difference could be observed between the slow and the fast heating process.
By Johan Van Brabant (Bekaert)

31. Corrosion protection: analysis
With higher speed, corrosion current is higher,
Quality is worse
Corrosion current
From this analysis of variance we learned that ,
A smaller corrosion current is observed, when the dipcoating process was slower,
Meaning that, even thought we see less material on the sample, the quality of the thin film is better, an.
Dipcoating speed

32. Corrosion protection: analysis
Differences, concerning the additives
Corrosion current
Sol
Ce/CA
Ce/CA +
Glycol +
siliconensusp
+ glycol
addition of glycol, without adding silicon emulsion is detrimental for the measured corrosion current. (P< 0,01).
Regarding the use of additives, glycol has a negative effect on the porosity, consistent with what was seen in the visible corrosion inspection. From the combined use of glycol and Si-emulsion we see that this negative effect can, at least partially, be compensated by the positive effect of the Si-emulsion.

33. 3 geometrys ‘donut’ ‘spiral’ ‘flat’
An additional problem was the geometry of the samples,
The original setup of the filter is a donut like structure folded as an accordeon, but this showed to be very sensitive towards corrosion at the pleads
(Top figure)
Rolling the filter strip into a spiral partially solved the problem. But with time, corrosion was visible
But in the end we had to stick to flat plates;, these are the only geometry that can be protected from corrosion over a long time (> 2 years).
‘flat’

34. Buffer layer CeO2 : morphology
Optical microscopy
Electron microscopy
Ce EDX
Optical and EDX analysis showed that the layer of CeO2 was very thin,
And that the filter was coated till the center of the filter.
50 mm
50 mm
Top view
Back view
Cut

35. Deposition of the catalyst on a Buffered filterCe
SEM
SEM EDX of the section of the coated filter
Shows a nice distribution of all elements , present on the surface of the sample,
Even on the inside of the filter
The micrograph shows a nice and shiny surface, evenafter prolounged time > 2 years,
Showing that corrosion can be avoided Cu Fe
Microscope Mo

36. Diesel soot catalyst Results Cl-free Ce-containing CeO2 buffer layer:
air permeability: 40%
improvement required
274 l/dm2.min
CeO2 buffer layer:
air permeability: 88 %
good
590 l/dm2.min
Concerning the air permeability some progress is still required.

37. Drop in combustion temperature
Catalytic activity
Filter +
Drop in combustion temperature
( O2 signal )
No Catalyst
- C
Cu/Mo/KCl
-50 °C
Cu/Mo / Ce
-80 °C
Flow Through reactor: activity on coated filter
10% O2 in Ar
5 x filter
4 x 0,01 g roet
massaspectrometer
O2 , Ar, KWS, CO2
Once coated , the catalytic activity was examined in a flow through reactor.
Pieces of filter were cut into plates of 5 mm diameter.
These were stacked into a reactor. In between the stacked filters 0.1 mg of soot was positioned.
During the test, temperature was increased. And a gas mixture of 90% Ar, 10 % O2 was preheated and flew over the filter at a rate of 75mL/min.
A reduction in combustioin temperature was registrated. In the same order of the one seen in the TGA measurements;
Showing that the activity could be transferred on the filter.,
And works in a flow-through set up.

38. Conclusion 3 layer filter medium(13*13 cm2) corrosion free
combustion temp reduction >100 °C
heavy duty diesel oxidation at: °C
air permeability

39. Besluit Vlakke filter kan gecoat worden
na cleaning , en afzetten met bufferlaag,traag dipcoaten (1mm/min)
probleem van corrosie: opgelost door :
goede bufferlaag
verwijderen Cl uit kat
probleem thermische stabiliteit katalysator
opgelost door verwijderen Cl
of 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?????)

40. Aknowledgments

41. Corrosion protection: analysis
With a plead, the corrosion current is higher
Corrosion current
In this figure it’s shown that the corrosion current is always bigger when a plead is present in the sample
Surface area of sample (cm2)

42. Composition of the catalyst
Based on XRD and XPS
- CuO (XRD)
- NaCl (XRD)
- Mo6+ (XPS)
If Ce is present: CeO2 (XRD)

43. Wat we weten:
vereist: bufferlaag
Analyse methode voor kwaliteit van de bufferlaag
methode : elektrochemisch
Analyse werking katal. : TGA
Afzetten:
Snelheid: trager -> hogere kwaliteit // vlugger -> meer
Sol: additieven van belang
+ glycol: goed tegen schuim, maar mindere kwaliteit
+ sil en + glycol: beter dan + glycol
probleem : batch II van siliconenen suspensie is verschillend
Temperatuursproces: geen verschil tussen de 2 programma’s

44. Analysis of Variance for evaluation of the use of APTS
(Aminopropyltriethoxysilane)
Volledig systeem

45. Wat is de rol van Ce bij de thermische stabiliteit van de katalysator ?
XRD
Hoofdzakelijk:
KCl
CuO
NaCl
Mo: ??? MoO3, MoCl5,
mogelijks Molybdaten en mengmolybdaten
In Ce -oxide kat ook: CeO2
XPS
Cu: BE typisch voor CuO, + eventueel andere fase
O: in CeOxide kat: 1 piek
in oxide kat en Chloride kat: 2 pieken
bij hogere BE, eventueel Carbonaten
Ce: 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

46. Ce-oxide katalysator Schuimvorming, kroes Na2MoO4 KCl CuCl2
+ NH4OH => pH = 7
Ce-nitraat
Citroenzuur
+ NH4OH => pH = 7
Mengen, gelleren, calcineren

47. Pretreatment of the substrate
Buffer layer CeO2 + catalyst layer
Pretreatment of the substrate
Processing
Processing requires good wettability.
This depends on :
- substrate (surface tension)
- sol (surface tension, viscosity,…)
cleaning involves :
- degreasing
- ultrasone step
- etching
A. Dipcoating
liquid
precursor-layer
cleaned
substrate
Precursor
solution
B. Thermal treatment
T>800°C, in air
liquid
precursor-layer
crystalline CeO2-film