TU Bergakademie Freiberg · Institute of Energy Process Engineering and Chemical Engineering · Chair of Reaction Engineering

Reiche Zeche · Fuchsmuehlenweg 9 · 09599 Freiberg · Phone: +49 3731 394551 · Fax: +49 3731 394555 · www.iec.tu-freiberg.de

Soot oxidation on manganese oxide catalysts

in gasoline exhaust gas

O 2r

r 2 (g)O

2

1

2

2

4

3COOCO(g)

r

r 2

6

5

2 CO(g)COr

r

2

O1

11 θcRT

EexpAr

2

2

Oo22

22 θRT

αEexpAr

θOCO

333 θc

RT

EexpAr

2COO44

44 θRT

EexpAr

θc

RT

EexpAr

2CO5

55

O 2

r

r 2 (g)O

2

1

2

4

3OCO(g)

r

r

dTcH

2

1dTcHdTcHΔH

T

T

Op,

0

Of,

T

T

COp,

0

COf,

T

T

COp,

0

COf,0

22

00

22

T

dTcS

2

1

T

dTcS

T

dTcS

1ΔS

T

T

Op,

0

O

T

T

COp,

0

CO

T

T

COp,

0

CO0

22

00

22R

4OFe3OFe2OFe1OFeO

OFeOFe rArAr2Ar2AdT

dΘβΓA

323232323232

3OFe4OFe6OFe5OFe

CO

OFeOFe rArArArAdT

dΘβΓA

32323232

2

3232

6OFe5OFeein(g),,COaus(g),,CO rArAcVcV323222

2OFe1OFeein(g),,Oaus(g),,O rArAcVcV

323222

3OFeein(g),,COaus(g),CO, rAcVcV32

Christian Singer, Maria Nitzer-Noski, Sven Kureti

Development of particulate emission limits

of EU for gasoline cars

2

0

1

2

3

4

5

6 mg/km

EU VI

PN 6E12 #/km

Strategies of particulate filter regeneration

Passive regeneration (T=200…450°C)

2 NO + O2 2 NO2

2 NO2 + “C” CO2 + 2 NO

Fuel Borne Catalyst: metal-organic compounds

“C” + O2 CO2 T > 300°C

Active regeneration (fuel post-injection)

“C” + O2 CO2 T > 600°C

Catalytic GPF (CGPF): CeO2 and Fe2O3 based catalysts

“C” + O2 CO2 T > 500°C

3

Evaluation of MnOx catalysts

DOC DPF

K. Ohno, Ph.D. thesis 2005

Temperature Programmed Oxidation (TPO)

Plug flow reactor with packed bed

4

T

t

DT/Dt=200 K/h

25°C

Evaluation of soot oxidation activity

PC

TI

FIC

Ar

H2

NO

O2

CO

TI TI

FIC

FIC

FIC

FIC

T controller

MFC

FIC

H2O

FICHC

N2

ppm

NOxppm

O2

vol.%

HCppm

COx

ppm

catalystTPO conditions

Laboratory test bench

y(O2)=1%, y(H2O)=2%, y(N2)=97%

F=500 ml/min (STP)

tight contact, loose contact

m=0.9 g (ncat/nsoot=2)

Model soot Printex U

Screening of MnOx catalysts

Physical-chemical characterisation

• XRD

• N2-physisorption (BET, BJH)

• SEM

• NH3-TPD

300

350

400

450

0 25 50 75 100

Tm

ax

/ C

n(NH3) / µmol/g

Structure-activity correlation

5

FSP-MnOx best catalyst

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

200 300 400 500 600 700 800

y(C

O2)

/ v

ol.

%

T / C

Mn3O4 wet

Mn3O4 FSP

Mn2O3 A.A.

Mn2O3 J.M.

Mn2O3 nano

Effect of contact: tight vs. loose

6

FSP-Mn2O3 requires contact to soot particles

0.0

0.2

0.4

0.6

0.8

1.0

0.0

0.2

0.4

0.6

0.8

1.0

200 300 400 500 600 700 800

y(C

Ox)

/ v

ol.

%

y(C

O2)

/ v

ol.

%

T / C

tight contactloose contactbare soot

Tight and loose contact mode

7

Loose contact Tight contact

Effect of O2 on activity of FSP-Mn2O3

8

0

0.2

0.4

0.6

0.8

1

200 300 400 500 600 700 800

y(C

O2)

/ v

ol.

%

T / C

1.0 vol.% O20.8 vol.% O20.5 vol.% O20.4 vol.% O20.3 vol.% O20.2 vol.% O20.1 vol.% O2

0

100

200

300

400

500

600

700

0

0.1

0.2

0.3

0.4

0.5

0.6

300 500 700 900T

/

C

y(C

O2)

/ v

ol.

%

t /s

9

1.0% O2: ΔTmax=25 K

2.5% O2: ΔTmax=70 K

Temperature inside catalyst bed

1.0%O2

Temperature evolution in catalyst bed

Temperature on catalyst surface

2.5%O2

1.0%O2

0

100

200

300

400

500

600

700

0

0.2

0.4

0.6

0.8

1

1.2

1.4

400 540 680 820

T /

C

y(C

O2)

/ vo

l.%

t /s

2.5%O2

10

transfer of ca. 17% of catalyst oxygen

importance of bulk oxygen

TPO

HTPR

Isotopic TPO with 18O2

MnOx

Thermal stability of FSP-Mn2O3

11

0.0

0.2

0.4

0.6

0.8

1.0

200 300 400 500 600 700

y(C

O2)

/ v

ol.

%

T / C

fresh

after 1050°C (4 h)

Activity after exposure for 4 h at 1050°C (static air)

SO2 stability of FSP-Mn2O3

12

Activity after SO2 exposure for 16 h at 250°C

(20 ppm SO2, 5% O2, 8% H2O, N2 balance)

0.0

0.2

0.4

0.6

0.8

1.0

200 300 400 500 600 700

y(C

O2)

/ v

ol.

%

T / C

fresh

after SOxexposure

Oxidation of ethanol-based soot on FSP-Mn2O3

13

very similar oxidation kinetics

of different soot samples

0

0,25

0,5

0,75

1

0 200 400 600 800

y(C

O2)

/ v

ol.

%

T / C

E0 FSP 550

E65 FSP 550

E100 FSP 550

Soot obtained from combustion of iso-octane/ethanol (Prof. Trimis, KIT)

Soot characteristics and catalytic oxidation

Soot d / nm S(BET) / m2/g

PrintexU 25 91

E0 12 425

E65 10 211

E100 6 96

14

Test of catalytic particulate filters

300 cpsi

60% porosity

FSP bench

Lab-GPF

Catalytic coating of lab-GPF Soot deposition on catalytic GPF

TPO conditions

Catalyst loading: 22 g/L

Soot loading: ca. 1.5 g/L

y(O2)=1%, y(H2O)=2%, N2 balance

F=6500 mL/min (S.V.≈20’000/h)

fuel air

N2

GPF

soot generator

1“

2“

1“

15

0

50

100

150

200

250

300

350

100 200 300 400 500 600 700

y(C

O2) / p

pm

T / °C

mit Kat

ohne Kat Effect of catalytic coating

Presence of loose and tight contact mode

Implementation into Three Way Catalysts

0

20

40

60

80

100

150 200 250 300 350 400 450 500 550 600

X / %

T / C

C3H6

ESF5-K1

ESF4g

ESF5-K2

ESF4o

0

20

40

60

80

100

150 200 250 300 350 400 450 500 550 600

X / %

T / C

CO

ESF5-K1

ESF4g

ESF5-K2

ESF4o

0

20

40

60

80

100

150 200 250 300 350 400 450 500 550 600

X / %

T / C

NO

ESF5-K1

ESF4g

ESF5-K2

ESF4o

C3H6 CO NO

catalytic GPF

Activity of GPF coated with FSP catalyst

bare GPF

Summary

16

Manganese oxides are effective in soot oxidation and show high resistance

towards thermal and SOx exposure

Manganese oxide catalyst requires

intimate contact to soot

FSP-Mn2O3 strongly supplies bulk oxygen

to soot

Beneficial effect of FSP catalyst also

occurs onto particulate filters

MnOx

Financial support from German Agency of

Renewable Resources (project BiOtto) is

thankfully acknowledged

Preparation and characterisation of the soot

17

number of primary particles

0 20 40 60 80 100d / nm

fuel air

N2

C3H6/O2 diffusion flame

Adsorbed species: 2.5 wt.%

Chemical composition

98.8 wt.% C

0.7 wt.% O

0.5 wt.% H

<0.1 wt.% N

SBET = 65 m2/g

d = 45 nm (most frequent diameter)

200 nm

Thermal stability of FSP-Mn3O4 catalyst

18

0

4

8

12

16

250 300 350 400 450

y(C

O2)

/ vo

l.%

T / C

fresh

after 4 h at 1050 C (air)

after 16 h at 750 C (10% H2O, 10% O2)

TPO conditions:

y(O2)=10%, N2

DT/Dt=100 K/h

m=0.9 g

ncat/nsoot=2

Performance of lab-DPF coated with FSP-Mn3O4

under diesel conditions

19

0

50

100

150

200

250

300

350

150 250 350 450 550 650 750

y(C

Ox)

/ vo

l.%

T / C

bare DPF

FSP-Mn3O4

@DPF

0

50

100

150

200

250

300

350

150 250 350 450 550 650 750

y(C

Ox)

/ vo

l.%

T / C

bare DPF

Ce@DPFFSP-Mn3O4

@DPF

TPO conditions:

Soot load: ca. 1.5 g/L

Catalyst load: 22 g/L

y(O2)=10%, y(H2O)=2%, N2

DT/Dt=100 K/h

S.V.≈20’000/h

20

0

50

100

150

200

250

300

350

100 200 300 400 500 600 700 800

y(C

Ox)

/ vo

l.%

T / C

diesel conditions

gasoline conditions

TPO conditions:

Soot load: ca. 1.5 g/L

Catalyst load: 22 g/L

y(O2)=1 or 10%, y(H2O)=2%, N2

DT/Dt=100 K/h

S.V.≈20’000/h

Performance of lab-DPF coated with FSP-Mn3O4

under diesel and lean gasoline conditions