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


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


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

Addition of Ce to a Cu-Mo catalyst

‣Thermal stability ‣Catalytic activtiy ??


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


‣Thermal stability ‣Catalytic acitivity ‣Thin layer ??


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



Dipcoating

Ce-citrate => autocombutison process Foaming- restriction on the amount of Cerium

in the catalyst- addition of anti-foaming agent

(Si-suspension ©Basildon)


High Ce loading low cerium loading Cu / Mo / Ce

2 / 1 / 0.8


Corrosion !


‣Thermal stability ‣Catalytic acitivity ‣Thin layer

‣Corrosion protection ??


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


‘donut’

‘spiral’

3 geometrys

‘flat’

Buffer layer CeO2 : morphology

Optical microscopy

50 mm 50 mm

Electron microscopy

Ce EDX

Top view Back view Cut

Ce

CuFe

Mo

Deposition of the catalyst on a Buffered filter

SEM

Microscope

36


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?????)

Aknowledgments

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


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

Volledig systeemAnalysis of Variance for evaluation of

the use of APTS(Aminopropyltriethoxysilane)

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


A. Dipcoating

B. Thermal treatment


T>800°C, in air

crystalline CeO2-film

Deposition of a soot catalyst on a metallic DPF filter, using an aqueous sol gel dipcoating...

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