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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.

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Presentation on theme: "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."— Presentation transcript:

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 Diesel soot filter Electric 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 medium FeCralloy: high temperature resistance

3 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 Add some pictures..

4 Diesel soot filter Coarse fitler Fine filter Loaded Soot-free Bekaert “ Development of a high efficiency diesel particulate filter medium and an adequate coating technology for catalysts” Area: 4 m 2 /g Press. drop: 670 l/cm Pourous filter: three layer medium FeCralloy: high temperature resistance

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6 UGENT: Aqueous sol-gel chemistry solution composition : M-salts : inorganic, alkoxides Solvent : H 2 O (> 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 M n+ H2OH2O Heat treatment under controlled atmosphere Cheap, environmentally benign 6

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8 (1) Coating technique sol gel dipcoating (2) Catalyst choose catalyst/ synthesis deposition and analysis (3) Predeposition of Buffer layer choose buffer layer/synthesis deposition and analysis Overview

9 Diesel soot catalyst Selection, deposition and improvement Starting point: Cu and Mo Selection of precursors: NaMoO 4, CuCl 2 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.

10  Improvement of the catalyst: better temperature stability remove all chlorides reduce foaming increase activity  Deposition: sol preparation choice of complexing agents temperature programm Diesel soot catalyst Selection, deposition and improvement

11 Precursor salts citric acid pH = 7 NH 4 OH aqueous precursor-solution gel drying at 60 °C Catalyst Thin layer thermal treatment Catalyst Powder Dip coating Gel on filter Diesel soot catalyst

12 Thermal stability, improves with addition of Ce 50/50 80/20 Thermal Stability Ce CuMo catalyst 100% CuMo TGA mass% CuMoKClCe

13 Cu-Mo Catalyst Cu-Mo-Ce Catalyst Thermal Stability, TGA-MS m=44 TGA mass

14 Thermal Stability With cerium, no Cl CuMoKClCe 2 (CuCl 2 )12- 2 (Cu(NO 3 ) 2 )1-0.8

15 Addition of Ce to a Cu-Mo catalyst ‣ Thermal stability  ‣ Catalytic activtiy ?? Diesel soot catalyst

16 Catalytic activity 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-NO x test 10% O 2 in Ar (NO x ) 5 x filter 4 x 0,01 g roet massaspectrometer O 2, Ar, KWS, CO °C TGA/DTA roet

17 Synergistic effect Catalytic activity Al2O3 CeO2 Catalyst Cu/Mo Soot Soot combustion temp. (°C)

18 TGA/DTA : Fixed Ratio: Catalytic activity Catalyst (Cu/Mo/Ce/Cl) SootInert Al 2 O

19 Addition of Ce to a Cu-Mo catalyst ‣ Thermal stability  ‣ Catalytic acitivity  ‣ Thin layer ?? Diesel soot catalyst

20 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 wetting FeCralloy exhibits low wettability

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

22 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

23 Deposition of the catalyst on a filter Corrosion !

24 Addition of Ce to a Cu-Mo catalyst ‣ Thermal stability  ‣ Catalytic acitivity  ‣ Thin layer  ‣ Corrosion protection ?? Diesel soot catalyst

25 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 CeO 2 Applications (other than bufferlayer for catalyst) - Buffer layer for HTS: - Fuel cells - Catalyst - Anti-oxidant (nanoparticles)

26 Buffer layer CeO 2 : precursor solution (1) Aqueous solution Metal precursor : Ce(NO 3 ) 3 Complexing agent : citric acid pH adaptation : NH 4 OH Specific modifications are necessary : Anti –foaming agents Speed Temperature programm Concentration Before After precursor solution gel oxide compound

27 27 Buffer layer CeO 2 : 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. 1:1 1:2 1: pH Ce:citric acid (1:1)/(1:2)/(1:3) pH = 0 – 10

28 Search for a good anti-foaming agent  Glycol, butanol, octanol and silicon suspension: APTS (aminopropyltriethoxysilane) Buffer layer CeO 2 : precursor solution Ce(NO 3 ) 3 citric acid additives aqueous precursor-solution gel drying at 60 °C CeO 2 thermal treatment amorphous citrate gel method

29 Corrosion protection: analysis Visual inspection Not treated 0,1 mm /min 10 mm/min 20 mm/min Higher dipping rate: More material WORSE PROTECTION? Samples coated in Ce-nitrate/ Citric acid gel + glycol and siliconsuspension

30 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

31 Dipcoating speed With higher speed, corrosion current is higher, Quality is worse Corrosion protection: analysis Corrosion current

32 Sol Ce/CACe/CA + Glycol + siliconensusp + glycol Differences, concerning the additives Corrosion protection: analysis

33 ‘donut’ ‘spiral’ 3 geometrys ‘flat’

34 Buffer layer CeO 2 : morphology Optical microscopy 50  m Electron microscopy Ce EDX Top viewBack viewCut

35 Ce Cu Fe Mo Deposition of the catalyst on a Buffered filter SEM Microscope

36 36 Diesel soot catalyst Results CeO 2 buffer layer: air permeability: 88 % good 590 l/dm 2.min Cl-free Ce-containing catalyst air permeability: 40% improvement required 274 l/dm 2.min

37 10% O 2 in Ar 5 x filter 4 x 0,01 g roet massaspectrometer O 2, Ar, KWS, CO 2 Flow Through reactor: activity on coated filter Catalytic activity Filter +Drop in combustion temperature ( O 2 signal ) No Catalyst - C Cu/Mo/KCl-50 °C Cu/Mo / Ce-80 °C

38 3 layer filter medium(13*13 cm 2 )  corrosion free  combustion temp reduction >100 °C  heavy duty diesel oxidation at: °C  air permeability Conclusion

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(NO 3 ) 3 + CA + Si-suspensie of Ce(NO 3 ) 3 + CA + Tex 1 of Ce(NO 3 ) 3 + CA + APTS of Ce(NO 3 ) 3 + APTS bij katalysator: Si-suspensie indien Cl aanwezig is (?????-Cl en -Ce, APTS?????)

40 Aknowledgments

41 With a plead, the corrosion current is higher Corrosion protection: analysis Corrosion current Surface area of sample (cm 2 )

42 Composition of the catalyst Based on XRD and XPS - CuO (XRD) - NaCl (XRD) - Mo 6+ (XPS) If Ce is present: CeO 2 (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 Volledig systeem Analysis of Variance for evaluation of the use of APTS (Aminopropyltriethoxysilane)

45 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 XRD Hoofdzakelijk: KCl CuO NaCl Mo: ??? MoO3, MoCl5, mogelijks Molybdaten en mengmolybdaten In Ce -oxide kat ook: CeO2 Wat is de rol van Ce bij de thermische stabiliteit van de katalysator ?

46 Ce-oxide katalysator Schuimvorming, kroes Ce-nitraat Citroenzuur + NH 4 OH => pH = 7 Na 2 MoO 4 KCl CuCl 2 + NH 4 OH => pH = 7 Mengen, gelleren, calcineren

47 47 Processing requires good wettability. This depends on : - substrate (surface tension) - sol (surface tension, viscosity,…) cleaning involves : - degreasing - ultrasone step - etching Buffer layer CeO 2 + catalyst layer Pretreatment of the substrate Processing cleaned substrate Precursor solution liquid precursor-layer A. Dipcoating B. Thermal treatment liquid precursor-layer T>800°C, in air crystalline CeO 2 -film


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