WE START WITH YES.

SOOT OXIDATION IMPACTED BY ENGINE OIL-DERIVED ASH FROM A GASOLINE DIRECT

INJECTION ENGINEApril 8, 2016

Heeje Seong and Seungmok Choi

Argonne National Laboratory

Jimmie L. Williams

Crystalline Materials Research, Corning Incorporated

Jung-Min Seo and Chi-Bum In

Exhaust Emission Engineering Team, Hyundai Motor Company

Bill Lam and Huifang Shao

Afton Chemical

2016 Cross-Cut Lean Exhuast Emissions Reduction Simulations (CLEERS) Workshop

BACKGROUND

2

With the increased PM emissions from GDI engines, GPFs have been

recognized to be enabling technologies to meet future PM emission standards

Considering factors

for particulate filters

Diesel engine

(lean)

GDI engine

(stoichiometric)

Exhaust temperature Low High

Regeneration

Active (post injection

or heater)Passive

Passive (NO2

generation)

Catalysts Oxidation catalysts TWC

Limitation Low temperature

Extremely low O2 &

NO2

Sensitive ∆P

“Add-on” GPF “All-in-one” GPF

Dow, 2010

MECA, 2013

3

BACKGROUND (CONT’D)

0

20

40

60

80

100

0 50 100 150 200

Printex U

LD Diesel_Ash 0.36%GDI_Ash 0.10%GDI_Ash 0.58%GDI_Ash 1.35%GDI_Ash 3.36%GDI_Ash 17.27%

m/m

0 [

%]

Time [min.]

Increase of

ash fraction

TGA isothermal oxidation

(600 °C, 8% O2, pre-treated by N2)

Engine oil-derived ash creates negative impacts on TWC performance and

back-pressure, while it can enhance soot oxidation

ANL, 2014 CLEERS

MIT, SAE 2009-01-1086

POSTECH, 2009 App. Cat. B: Env.

OBJECTIVES

Evaluate ash composition-dependent soot oxidation and find oxidation

mechanisms.

Identify ash chemistries that could influence soot and catalysts.

APPROACH & CHARACTERIZATION

4

Soot oxidation experiments and bench-

scale filter tests (2”(D)x6”(L))2.4L GDI Engine

TGA

DSC

Characterization of GDI soot

and filter substrates

(APS, CNM, UIUC)

Gravimetric

sampling

In-line filter

Formulated engine oils were dosed into fuel

(accelerated oil injection: 2% in fuel)1. Ca-, P- & P-Zn-specific engine oils (ANL only)

2. Ca/Mg/Zn/P formulated experimental engine oils designed by matrix

(Afton supplied)

5

Based on major additive components, Ca-, P- & Zn-P-specific engine oils were formulated (ANL only)

ICP analysis:

0

500

1000

1500

2000

2500

3000

3500

Non-detergent(SAE30)

Gasoline(5W20)Conventional

Gasoline(5W20)Synthetic

Gasoline(5W20)Longer life

Diesel(15W40)

Co

nce

ntr

atio

n (

pp

m)

Na

Ca

Mg

B

Zn

P

Mo

4,659 ppm 3,805 ppm 5,212 ppm 6,780 ppm646 ppm

Ca source: Calcium dodecyl-benzene

sulfonate

P source: Triethyl phosphite

Zn & P: Zinc dithiophosphate

(ZDDP)

Dosage in fuel (ppm) Ca Zn P Na Total

Gasoline Only 0.0

1% Non-detergent oil 0.4 3.3 2.7 6.4

1% Conventional oil 21.2 11.0 9.6 4.6 46.5

Calcium Sulfonate

in 1% non-detergent oil4 – 24 4 – 24

Phosphite

in 1% non-detergent oil18 – 55 18 – 55

Zinc Dialkyl Dithiophosphate (ZDDP)

in 1% non-detergent oil8 – 206 8 – 191 16 – 397

Matrix design of oil formulations helps better understand effects of Ca(Mg)/ZDDP ratios on soot oxidation

6

Experimental Oil

Samples (Afton

Supplied)

Ca-LL Mg-LL Ca-LH Mg-LH Ca-HL Mg-HL Ca-HH Mg-HH

Boron, ppm 180 180 180 180 180 180 190 180

Calcium, ppm 1100 1 780 0 2670 3 2360 1

Magnesium, ppm 8 680 3 480 9 1680 8 1420

Phosphorus, ppm 600 600 1220 1220 600 610 1210 1170

Zinc, ppm 710 710 1430 1430 700 720 1410 1380

Sulfated Ash, % 0.56 0.51 0.65 0.63 1.02 0.93 1.1 0.96

Ca/(P+Zn) or Mg/(P+Zn), molar 0.91 0.93 0.32 0.32 2.21 2.25 0.97 0.97

0

20

40

60

80

100

0 50 100 150

Ca-LL

Ca-HL

Ca-HH

Ca-LH

Mg-HL

Mg-LL

Mg-LH

Mg-HH

So

ot

rem

ain

ing

mass

(%

)

Time (min)

t800

10

20

30

40

50

0 0.5 1 1.5 2 2.5

CaMg

t80

(m

in)

Ca(or Mg)/(P+Zn), molar ratio

More reactive

2016 © Afton Chemical Corporation, All Rights Reserved. Not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation.

7

Soot oxidation enhanced with Ca, while deteriorated with P

TGA: isothermal 600ºC, 8% O2

0

20

40

60

80

100

0 100 200 300 400 500

Non-detergent oil 1%

Conv. oil Ash 3.7%

Conv. oil Ash 23.4%

Ca Ash 3.5%

Ca Ash 5.8%

P Ash 3.2%

P Ash 5.6%

ZDDP Ash 8.5%

ZDDP Ash 16.7%

Carb

on

so

ot

mass (

%)

Time (minutes)

Impact on soot oxidation

by 1.0 wt.% of ash fraction in soot

Ca +14.5%

P -15.4%

ZDDP (Zn+P) -13.7%

Conv. oil +11.1%

Baseline: non-detergent oil 1%

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 0.5 1

△m

/min

stan

t((

mg/

min

)/m

g)

Conversion (α)

Non-detergent oil 1%

Conv. Oil 2% - 93 ppm

Ca 24 ppm

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0 0.5 1

△m

/min

stan

t((

mg/

min

)/m

g)

Conversion (α)

Non-detergent oil 1%

P 36.5 ppm

ZDDP 109.2 ppm

Testing set-up that enables aging test and realistic GPF conditions has been built

8

Engine oil tank

Air heater

GPF

GPF system

In-line GPF setup (2”(D)x6”(L))- No visualization

- Hot exhaust T as actual test

- No sealing problem

Dilution setup and emissions measurements

- Quick access: 3-way valve for fast measurements

Lube-oil injection system

- Aging test enabled

∆P decrease in the initial regeneration stage confirms ash-induced continuous regeneration

9

Ash loading

- Engine oil: conventional 5W20

- Oil consumption rate: 2% in fuel

- Operated at 1250 rpm – 25% load

Continuous regeneration

- When the initial soot loaded was 0.45 g/L, exhaust temperatures were increased by

changing the engine operation mode (2000 rpm – 50% load)

- After soot burning at the initial stage, soot loading resumed

- Slow soot oxidation with no ash even at 550°C due to the extremely low O2 availability

Continuous operation

80

85

90

95

100

0

50

100

150

200

250

300

0 0.1 0.2 0.3 0.4 0.5

Filt

rati

on

eff

icie

ncy

(%

)

Pre

ssu

re d

rop

(kP

a/(m

3/s

ec))

Soot loading (g/L)

△P - W/O Ash

△P - Ash 2.0 g/L

FEmass - W/O Ash

FEmass - Ash 2.0 g/L

Soot mass: 10 mg/m3

Filter: HP200/12-2X

GPF inlet temperature: 550°C

O2, in: 1.5%

Initial soot loading: 0.45 g/L

Soot conc.: 1.0 mg/m3

Synchrotron XRPD indicates that ash derived from Ca sulfonate is CaSO4, which indeed enhances oxidation

10

Sample preparation: - Tight contact: grinding in agate mortar

CaSO4 impact is significant- BET S.A.: Drierite > CaSO4 (S-A)

- BET surface area seems to affect oxidative reactivity

(drierite: 10 m2/g, CaSO4 (S-A): 2 m2/g)

MIT, SAE 2009-01-1086

Ash from field-aged DPF

Sulfur K-edge XANES results suggest that sulfur oxidation states vary during soot oxidation

11

-5.00E-01

0.00E+00

5.00E-01

1.00E+00

1.50E+00

2.00E+00

2.50E+00

3.00E+00

3.50E+00

2460 2470 2480 2490 2500 2510

CaSO4_fresh

CaSO4_50%

CaSO4_100%

-1.00E+00

0.00E+00

1.00E+00

2.00E+00

3.00E+00

4.00E+00

2460 2470 2480 2490 2500 2510

K2SO4_fresh

K2SO4_50%

2471.4 keV

Sample preparation:

- Tight contact by grinding in mortar

- 0%, 50% & 100% oxidized at 600°C

- Ex-situ XANES analysis in APS at ANL

S K-edge XANES:

- 0%-oxidized CaSO4 is actually hydrated form

- 50% oxidized samples only

- Small hump at 2471.4 keV: 1+ oxidation

- Suggest a potential variation of sulfur oxidation

states during oxidation

- In-situ experiments will be performed.

Bare, 2005 APS

However, the presence of sulfur is not clear in GDI engine tests

12

SEM-EDS result of soot collected from Ca-LH case (p. 9)

CaseAtomic %

Ca P Zn S

Ca

additive

1.23 0 0 0

P

additive

0 2.83 0 0

ZDDP 0 2.88 0.08 0

150155160165170175180

S 2P in soot from Ca additiveS 2P in soot from P additiveS 2P in soot from ZDDP

XPS result of soot samples (p. 6)

AlP Ca

Ce

ZrCu(from grid)

Zn

TEM-EDS result of ash taken

from a field-aged GPF

PCa

Cu(from grid)

Zn

TEM-EDS result of ash derived

from engine oil in GDI engine

P

Ca

Zn Ca

Oil matrix dependent on Ca(Mg)/ZDDP ratios affects ash composition and soot residue

13

400 800 1200 1600 2000 2400 2800

Inte

ns

ity

(A

.U.)

Raman shift (cm-1

)

Carbon

Ca-HL

Mg-HH

Ca-HH

Mg-LH

Ca-LH

Mg-HL

ZnO

(M)CO3

Samples:- Ash remained after oxidation completed

UV-Raman (325 nm)

Soot still remained with ash- Except Ca-HL case, soot was present

May contribute to increased ∆P

Ash compositions influenced- High Ca(Mg)/ZDDP cases appear to

generate ZnO.

- Low Ca/ZDDP case generates –CO3

compounds.

2016 © Afton Chemical Corporation, All Rights Reserved. Not to be copied, shared, or reproduced in any media without the express written permission of Afton Chemical Corporation.

Amorphous nuclei particles from engine oil might convert into crystalline agglomerates with oxidation

14

Amorphous particles

(no crystallites)

Metal crystallitesMetal crystallites

Raw particlesash remained after

soot oxidation

The nature of nuclei particles derived from engine oil has been rarely examined.

While most nuclei particles in the sub-20-nm were observed to be amorphous metal

particles, ash agglomerates in the sub-micron were metal crystallites.

Suggest phase conversion from amorphous into crystalline state during oxidation

Major elements of sub-20-nm particles were observed to be P and Ca

Need more investigation when the engine is run at high speed & load

Will inform ash chemistries affecting TWC functionality

1250rpm-25% load

Nuclei particles

(<20nm)

Dark-field STEM

CONCLUSIONS

15

Soot oxidation enhanced by engine oil-derived ash is closely related to

the increased ratio of Ca to Zn & P in engine oil.

− Ca additive is more impactful than Mg additive.

− Soot oxidation reactivity is much dependent on Ca (or Mg) to ZDDP ratios,

regardless of contents of Ca, Mg, Zn and P.

Ash chemistries seem to be appreciably influenced by oil matrix.

− ZnO with high Ca(Mg)/ZDDP

− Carbonate (-CO3) with low Ca/ZDDP

The major ash compound, CaSO4, from diesel engines could contribute

little to ash from GDI engines.

− Sulfur element was rarely observed with XPS, SEM-EDS and TEM-EDS.

Amorphous ash nanoparticles may convert into crystalline agglomerates.

− Nanoparticles in the sub-20-nm range are mostly Ca and P, while S and Zn

were rarely observed.

ACKNOWLEDGEMENTS

Funding

- U.S. DOE Office of Vehicle Technologies, Ken Howden and

Gurpreet Singh

use of the Center for Nanoscale Materials and Advanced Photon

Sources was supported by the U. S. DOE Office of Science,

Office of Basic Energy Sciences, under Contract No. DE-AC02-

06CH11357.

XPS analysis was performed in UIUC-MRL.

All rights from oil matrix and related results are reserved for Afton

Chemical Corporation.

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