Diesel Fuel Quality and Sulfur Effects on Catalyst-Based Exhaust Emission Controls:

Manufacturers of Emission Controls Association

May 2000

Presentation Outline

Introduction Impact of Fuel Sulfur on Catalyst Emission Control

Technology Noble Metal Function NOx Control Technology PM Control Technology

Conclusions

Introduction

Fuel Quality Is an Integral Part of a Complete Emission Control System for Both Gasoline and Diesel Powered Vehicles

Although Other Fuel Constituents Affect Engine-Out Emissions, Fuel Sulfur Is the Single Most Important Constituent for Catalyst-Based Emission Control Technology

Sulfur in Diesel Fuel Adversely Affects the Emission Control Performance of All Catalyst-Based Emission Control Technologies

Introduction (cont.)

Near Zero Diesel Sulfur Levels Would Enable the Application of the Full Range of Control Technologies and Would Permit Each Technology to Be Optimized for Maximum Emission Control Performance

EPA Has Proposed Phase 2 On-Road HDE Standards of 0.2 g/bhp-hr NOx and 0.01 g/bhp-hr Particulate to Take Effect in the 2007 Timeframe

Fuel Sulfur Levels Will Be Instrumental in Meeting These Aggressive Targets

Zeolite or refractory oxide support

Precious Metal

SO3

SO4 =

Transition Metal

H2SO4

O2

Sulfate make

Sulfur inhibition

Sulfate Poisoning

SO2

Sulfur Effects

Test procedure: Engine test bench, partial load, 1.9 L TDI engine

Noble Metal Function: Sulfur Increases Light-Off Temperature and Reduces Peak Conversion

80 120 160 200 240

100

80

60

40

20

0 C

O C

onve

rsio

n (%

)

Exhaust temperature before catalytic converter (oC)

Regular Diesel fuel (350 ppm S)

Quissel et al, VDA-Fortschrittsberichte, 12 (348), Bd. 2, 225-246 (1998)

80 120 160 200 240

100

80

60

40

20

0

CO

Con

vers

ion

(%)

Exhaust temperature before catalytic converter (oC)

Sweden Diesel fuel (<10 ppm S)

1/2 hr Conditioned 32 hr Aging

Oxidation Catalyst

Sulfur Adversely Affects Non-Precious Metal

Lean NOx Catalysts

0 5

10 15 20 25 30 35 40 45 50

250 350 450 550 650

Inlet Temperature (C)

NO

x C

onve

rsio

n (%

)

NOx = 500ppm HC/NOx = 5 SV =25,000/hr

1 ppm

350 ppm

NOx Adsorbers: Sulfur Effects

Sulfur Poisoning and Inhibition Inhibits Conversion of Unregulated Emissions (e.g. toxic HC

emissions) Prevents NOx Conversion Increases Fuel Economy Penalty

Sulfate Make

Sulfur Poisons NOx Adsorbers Storage Sites

30s/2s 30hrs at 400 C

0

10

20

30

40

50

60

70

80

90

100

200 250 300 350 400 450 500

Evaluation Temperature (C)

NO

x C

onve

rsio

n (%

) 13

0

20

40

60

80

100

120

1 2 3 4 5 6 7 8 9 10 11 12

Depth into Washcoat

S/B

a M

olar

Rat

io (%

)

200 ppm 100 ppm 0 ppm 40 ppm *equivalent fuel sulfur content*

The extent of poisoning increases with fuel sulfur content and duration of exposure.

Low Levels of Sulfur Are Needed to Maintain NOx Adsorber Catalyst Efficiency

0

20

40

60

80

100

0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000

Miles Traveled

Cat

alys

t NO

x B

reak

thro

ugh,

%

7 ppm Sulfur Fuel Catalyst "A"

150 ppm Sulfur Fuel Catalyst "A"

300 ppm Sulfur Fuel Catalyst "B"

0.1 ppm Sulfur Fuel Catalyst "c"

7 ppm Fuel: 1700 Miles

150 ppm Fuel: 115 Miles

300 ppm Fuel: 55 Miles

Mileage Interval vs Fuel Sulfur Content which Leads to a 5% Decrease in

Catalyst Efficiency (Note: T/P NOx emissions double when catalyst

efficiency drops from 95 to 90% )

0.1 ppm Fuel: >5,000 Miles

0 20 40 60 80 100 120 140 160

100 90 80 70 60 50 40 30 20 10 0

Poisoning period (hr)

NO

x C

onve

rsio

n (%

)

Gasoline fuel: California Phase 2 (ca. 30 ppm S) - Catalytic converter B

Gasoline fuel: Super Plus (130 ppm S) Catalytic converter A

Gasoline fuel: California Phase 2 (ca. 30 ppm S) Catalytic converter A

Cycle during poisoning and measurement: 30/2 S lean/rich

Test Procedure: Engine test bench, partial load operation

Quissel et al, VDA-Fortschrittsberichte, 12 (348), Bd. 2, 225-246 (1998)

Advances in NOx Adsorber Sulfur Resistance

Catalytic Particulate Filters: Sulfur Effects

Sulfur Poisoning and Inhibition Inhibits Control of Unregulated Emissions Increases Regeneration Temperature

Formation of Sulfate

Catalytic Filter Regeneration Is Adversely Affected by Sulfur

A Low Regeneration Temperature Insures Reliable Catalytic Filter Operation and Durability

A Low Regeneration Temperature Allows Filter Technology to Be Applied to a Broad Range of Vehicle Applications

Higher Sulfur Levels in Diesel Fuel Increase a Catalytic Filter’s Regeneration Temperature In the DECSE Program, Increasing the Fuel Sulfur Content from 3

ppm to 30 ppm Increased the Regeneration Temperature of Two Different Catalytic Filter Systems by 23 to Over 30 oC.

Experience in Countries Characterized by Very Cold Temperatures, e.g. Sweden, Indicates that There Have Been No Durability Problems with Systems Having Accumulated in Excess of 475,000 km when Diesel Fuel with <10 ppm Is Used

IMPACT OF FUEL SULFUR ON HEAVY DUTY PM EMISSIONSASSUME: BSFC = 0.355 H2O/SO4 = 1.3

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0 5 10 15 20 25 30 35 40 45 50

FUEL SULFUR, ppm

SULF

UR C

ONTR

IBUT

ION

TO P

M

g/bh

p-hr

40% S CONV 50% S CONV 60% S CONV DECSE SwRI

Impact of Sulfur on Heavy-Duty PM Emissions

90% Reduction from 2004 Std.

CALCULATED IMPACT OF FUEL SULFUR ON LIGHT DUTY DIESEL PM EMISSIONS ASSUME: 25 MPG H20/SO4=1.3

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

0.050

0 5 10 15 20 25 30 35 40 45 50FUEL SULFUR, PPM

SULF

ATE

CONT

RIBU

TION

TO

PM, G

/MIL

E

25% S CONV50% S CONV75% S CONV

TIER II LIMITS BINS 6-7

TIER II LIMITS BINS 2-5

Impact of Sulfur on Light-Duty PM Emissions

The DECSE Study Is Showing That Low Sulfur Is Critical to Achieving a 0.01 g/bhp-hr PM Standard

(System 1)

From DOE website; Diesel Emission Control - Sulfur Effects;

Sponsored by DOE, EMA, MECA, and National Labs

OICA 13-mode cycle; CAT 3126 engine

~95% efficiency at 3 ppm sulfur

~70% efficiency at 30 ppm sulfur

~0% efficiency at 150 ppm sulfur

Negative efficiency at 350 ppm sulfur

00.020.040.060.08

0.10.120.140.160.18

0.2

3 30 150 350

OtherSulfateSolid

The DECSE Study Is Showing That Low Sulfur Is Critical to Achieving a 0.01 g/bhp-hr PM Standard

(System 2)

From DOE website; Diesel Emission Control - Sulfur Effects;

Sponsored by DOE, EMA, MECA, and National Labs

OICA 13-mode cycle; CAT 3126 engine

~95% efficiency at 3 ppm sulfur

~70% efficiency at 30 ppm sulfur

~0% efficiency at 150 ppm sulfur

Negative efficiency at 350 ppm sulfur

0

0.05

0.1

0.15

0.2

0.25

3 30 150 350

OtherSulfateSolid

Status of Reducing Impacts of Sulfur on NOx Adsorbers

MECA Members Continue Research Efforts in Decreasing Sulfur Sensitivity

BUT, Desulfurization Frequency Needs to Be Minimized for Commercial

Viability of NOx Adsorbers Minimize Fuel Economy Penalty Maximizes the Opportunity for Operating Conditions

Conducive to Desulfurization to Be Met Under Normal In-Service Operation

To Meet Very Low Emission Levels Only an Approximately 5% Decrease in Performance Can Be Tolerated

Control of Unregulated Emissions Is Inhibited Off-Cycle Emissions During Desulfurization Inhibition of the Performance of Other Emission Control Devices Sulfur Inhibition Is Cumulative

Status of Reducing Impacts of Sulfur on Catalytic Particulate Filters

MECA Members Continue Research Efforts in Decreasing Sulfur Sensitivity

BUT, Sulfur Significantly Increase the Balance Point Temperature

Due to Sulfur Inhibition which Adversely Affects Filter Regeneration Control of Unregulated Emissions Is Inhibited Cold Climatic Conditions Exasperate the Effects of Sulfur

Inhibition Sulfur Inhibition Is Cumulative

Conclusion

To Help Insure that Diesel Fuel Remains Competitive with Other Fuels, It Is Incumbent on the Engine Manufacturers, the Emission Controls Industry, and the Fuel Providers to Work Together to Provide a “Truly Clean” Diesel Engine so that the Public Accepts the Fuel As an Environmentally Friendly, Safe, and Efficient Means to Meet the Nation’s Transportation Needs