DEER 2010 1

Dr. R. Samuel Boorse1, Dr. Martin Dieterle1, Dr. Kenneth Voss1, Dr. Susanne Stiebels2, Dr. Claudia Wendt2, Dr. Torsten Neubauer2

1 BASF Corporation; 25 Middlesex/Essex Turnpike; Iselin, NJ 08830 USA2 BASF Catalysts Germany GmbH; Freundallee 23, 30173 Hannover

Two in One:SCR on Filter

DEER 2010 2

Potential Systems for Diesel Exhaust Control

TODAY

Hydrocarbons soot NO X

CO

fuel urea

Diesel Catalysed Selective oxidation soot catalyticcatalyst filter reduction

DOC CSF SCR

TOMORROW

SCR on fuel urea Filter

DOC SCR on Filter

DEER 2010 3

Requirements for a Combined SCR on Filter System

soot filter high filtration efficiencylow backpressure

high porosity filter

NOx abatement high NOx efficiency

highly thermally stable to withstand soot burnoff

highly active and hydrothermally stable catalyst

* Aging: 850°C 5 hours** Aging 750°C 5 hours

40

60

80

100

0 2000 4000

time [s]

Num

ber

base

d tr

app.

eff.

[%

]

CSF

high porosity filter

0

20

40

60

80

100

150 250 350 450 550Temperature [ºC]

NO

con

vers

ion

[%]

Cu-zeoliteFe-zeolite *

**

DEER 2010 4

void spacecordieritecatalyst

SCR Catalyst Loading into High Porosity Filters

SEM of cordierite wall only SEM of cordierite wall with catalyst

Pore microstructure influences: backpressure of filter

mechanical strength of filter

catalyst distribution and NOx conversion

DEER 2010 5

Comparison of NO Conversion of SCR on Filter Substrate and Flowthrough Substrate

Higher NO conversion observed for filters at comparable washcoat loading.

Better catalyst utilization of filters compared to flowthrough substrates due to larger geometrical surface.0

20

40

60

80

100

NO

con

v. a

t 200

C [%

] filter substrateflowthrough substrate

SV = 37 k h-1 80 kh-1

Aged at 850 C for 5 Hours

DEER 2010 6

Optimization of Catalyst Loading on Different Cordierite Filters with Different Porosity

Combination of conversion and backpressure defines operation window Operation window is determined by filter porosity and pore size distribution

Cordierite B- Cu-Zeolite60% porosity

(Aged 750 C, 5 h)

0

20

40

60

80

100

NO

Con

v. [%

]0

20

40

60

80

100

∆∆

p [%]

NO conv. at 200 C∆∆ p

Cordierite A - Cu-Zeolite65% porosity

(Aged 750 C, 5 h)

0

20

40

60

80

100

Catalyst Loading [g/in3]

NO

Con

v. [%

]

0

20

40

60

80

100

∆∆

p [%]

NO conv. at 200 C∆∆ p

Catalyst Loading [g/in3]

DEER 2010 7

Comparison of Cordierite and Silicon Carbide Filters at Constant Catalyst Loading

Cordierite: A 65 % porosityB 60 % porosity

Silicon Carbide: 59 % porosity

Results are show for samples at a constant catalyst volume and loading.

Silicon carbide microstructure allows greater conversion at equivalent catalyst volume or better catalyst utilization.

Catalyst loading process needs to be developed for each filter type

0

20

40

60

80

SiC Cord. B Cord. A

NO

Con

v. [%

]; ∆∆

p [%

] NO Conv. [%] p [%]

∆∆

DEER 2010 8

Conclusions from Laboratory Reactor Studies

SCR on Filter demands high porosity substrates for acceptably low backpressure.

Backpressure targets and NO conversion targets define catalyst loadings specifically for each filter type.

Catalyst loading processes must be optimized for each filter type and application.

Next Steps:

Proof in engine testing.

Investigation of interaction with soot.

DEER 2010 9

SCR on Filter Performance in NEDC Testing:Test Conditions and Program

System: DOC and SCR on Filter system with Urea injection tested on 2 l engine

DOC 1.2 l 120 g/ft³ for HC and CO conversion

SCR on Filter: Cu-Zeolite on SiC substrate Ø 5.66“x 6“ (2.5 l)

NEDC test program: SCR on Filter Characterization:

fresh and after hydrothermal oven aging 5 h at 750 C.

3 different NO2/NOx ratios at inlet SCR

testing of soot free and with 8 g/L soot loading on SCR on Filter

For comparison with flowthrough catalyst, 2 different temperature profiles

Closed coupled (SCR on Filter) vs.

Underfloor position (SCR on Flowthrough substrate)

DEER 2010 10

NEDC Test Program Parameters:SCR Inlet Temperature Variation and NO2/NOxInlet SCR Variation

Approximately 25 C difference in closed coupled vs. underfloor position of the SCR component

NO2/NOx ratio achieved by changing PGM content of the exhaust system

0

100

200

300

400

0 200 400 600 800 1000 1200

In

let T

empe

ratu

re S

CR

[C

]

colder setup

warmersetup

∆T ~ 25 C

Time [sec]

0

0.2

0.4

0.6

0.8

1.0

NO

2/NO

xR

atio

0 1000400 600 1200Time / s

800200

high NO2

medium NO2

low NO2

DEER 2010 11

SCR and SCR on Filter for Fresh and Aged Catalysts:Low NO2/NOx Ratio, without Soot at Comparable Sizing

Time / s

SCR on FilterFresh (59%)Aged (58%)

Cum

ulat

ive

NO

xEm

issi

ons

/ g

FlowthroughFresh (58%)Aged (62%)

Aging: SCR on Filter: 5 h at 750 C Cumulative raw NOx emission: 2gSCR 40 h at 750 C

No deactivation upon 750 C aging.

Comparable NOx conversion of DOC + SCR on Filter relative to DOC + CSF + SCR system. SCR on Filter is at the warmer position.

0

0.2

0.4

0.6

0.8

1

1.2

0 200 400 600 800 1000 1200

80ve

hicl

e sp

eed

DEER 2010 12

Results NEDC Test Program:Impact of Soot on NOx Conversion at as a Function of NO2/NOx Ratio

Accumulated soot has a small positive impact on the NOx conversion of SCR on Filter at high NO2/NOx ratios.

Cum

ulat

ive

NO

xEm

issi

ons

/ g

Cumulative cycle raw NOx emission: 2g

0

0.3

0.6

0.9

1.2

0 1000400 600 1200Time / s

800200

1.5

high NO2

low NO2

medium NO2

DEER 2010 13

Summary SCR on Filter

SCR on Filter performance comparable to flowthrough at equivalent volume and loading Good catalyst utilization on filters. Catalyst loading and thus NOx conversion of filters is limited due

to backpressure limitations. Filter type, porosity determines catalyst utilization.

NEDC testing with Cu zeolite on Filters High DeNOx activity fresh and after aging.Small impact of soot on NOx conversion.