john r. lindsay smith, moray s. stark, julian j. wilkinson

Department of Chemistry

John R. Lindsay Smith, Moray S. Stark, Julian J. WilkinsonDepartment of Chemistry, University of York, York YO10 5DD, UK

Peter M. Lee, Martin PriestSchool of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, UK

R. Ian TaylorShell Global Solutions, Shell Research Ltd., Chester, CH1 3SH, UK

Simon ChungInfineum UK Ltd., Milton Hill, Abingdon, Oxfordshire, OX13 6BB, UK

The Degradation of Lubricants in Gasoline Engines

STLE Annual Meeting : Toronto 17th- 20th May 2004


John R. Lindsay Smith, Moray S. Stark, Julian J. Wilkinson*Department of Chemistry, University of York, York YO10 5DD, UK

Peter M. Lee, Martin PriestSchool of Mechanical Engineering, University of Leeds, Leeds, LS2 9JT, UK

R. Ian TaylorShell Global Solutions, Chester, CH1 3SH, UK

Simon ChungInfineum UK Ltd., Milton Hill, Abingdon, Oxfordshire, OX13 6BB, UK

The Degradation of Lubricants in Gasoline Engines

Julian Wilkinson [email protected] www.york.ac.uk/res/gkg

Part 3: Chemical Mechanisms for the Oxidation of Branched Alkanes


Aims

Identify products from micro-reactor oxidation.

Compare results to engine.Use identified products to propose

reaction mechanisms.Ultimately, understand and predict

viscosity increase


Aims


Chemical Mechanisms for the Oxidation of Branched Alkanes

Previous Work

Branched Alkanes as Base Fluid Models

Chemical Analyses

Reaction Mechanisms


Summary of oxidation

Sludge

L ac tones A lcohols K etones Bifunc tiona ls A c ids

Hydroperox ide

A lkane

?

Viscosity Increase


Traditional Model of Hydrocarbon Oxidation

+ ROO . .+ ROOH

Alkane Alkyl radical



+ ROO. .

+ ROOH

.+ O2

OO Alkane Alkyl radical

Hydroperoxy radical



+ ROO. .

+ ROOH

.+ O2

OO

OO

+ RH

OO

H

+ R.

Alkane Alkyl radical

Hydroperoxy radical

Hydroperoxide



OO

H

O

+ .OH

Hydroperoxide Alkoxy radical



OO

H

O

O + H

O

+ RH

OH

+ R.

Alkoxy radical Alcohol



O

+ H2O

OO

H

Hydroperoxide Ketone


Ease of abstraction of H atom

C

H

H

H

C

C

C

C

C

C

C

H

C

H

HH

H H

H

H

H

HH

H

H

H H



H Primary: Difficult



H

H

Primary: Difficult

Secondary: Moderately difficult



H

H

H

Primary: Difficult


Tertiary: Easy



H

H

H

H

Primary: Difficult


Allylic: Very easy

Tertiary: Easy


Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average) 39(random example)



No. of Carbons

XHVI™ 8.2 (average) 39

Trimethylheptane 10

(random example)


Trimethylheptane Oxidation : 100 – 120 °C

OO H

OO

H

OO

OO

H

O

O

H

D. E. Van Sickle, J. Org. Chem., 37, 755 1972



OO H

OO

H

OO

OO

H

O

O

H

OO

H

O

O

H

OO

H

D. E. Van Sickle, J. Org. Chem., 37, 755 1972



OO H

OO

H

OO

OO

H

O

O

H

OO

H

O

O

H

OO

H

D. E. Van Sickle, J. Org. Chem., 37, 755 1972O O

HH

O O O

H H H



No. of Carbons

XHVI™ 8.2 (average) 39

Trimethylheptane 10

Hexadecane 16

(random example)


Hexadecane Oxidation : 120 – 180 °C

Jensen et al, J. Am. Chem. Soc., 103, 1742 1981 and 101, 7574 1979

OO H




OO H

OO

H

OO




OO H

OO

H

OO

OO

H

OO

H




OO H

OO

H

OO

OO

H

OO

H

O OH



No. of Carbons

XHVI™ 8.2 (average)

39 Trimethylheptane

10

Hexadecane

16

Tetramethylpentadecane

19

(random example)

(TMPD)



No. of Carbons

XHVI™ 8.2 (average)

39

Trimethylheptane 10

Hexadecane

16

TMPD

19

Squalane 30

(random example)


Amount of Tertiary Carbons in a Range of Base Fluids

0

5

10

15

20

25

PA

O

Gro

up II

I iso

dew

axed

Gro

up II

I hyd

rocr

acke

dG

roup

IIG

roup

IX

HV

I 8.2

tert

iary

C (

%)

McKenna et al. STLE Annual Meeting, Houston, 2002


Amount of Tertiary Carbons in a Range of Base Fluids

0

5

10

15

20

25

terti

ary

C (%

)

McKenna et al. STLE Annual Meeting, Houston, 2002


Oxidation of TMPD

time (min)

Micro-reactor conditions: 1000 mbar O2, 200 ºC, 1 minute

GC-MS conditions: ZB-5 column, 50-300 ºC, 6 ºC min-1

impurity


Oxidation of TMPD: Ketones

time (min)

O

(m/e = +14)

Ketone

impurity


Oxidation of TMPD: Ketones

time (min)

O

(m/e = +14)

O

O

O


Oxidation of TMPD: Alkanes

time (min)

Alkane


Oxidation of TMPD: Fragmentation

time (min)

O

O

+ .

RH


Oxidation of TMPD: Fragmentation

time (min)

+

O

O


Oxidation of TMPD : Fragmentation

time (min)

+

O

O


Oxidation of TMPD : Alkenes

time (min)


Possible Mechanisms of Alkene Formation

OHH

OH+



OH

O

OH

+ (H+)

OO

+ H2O

Alcohol AcidEster



OO

OH

O

+

Acid

Ester

Alkene


Alkenes and viscosity increase

Very Easy .

Monomer


Alkenes and viscosity increase

.

+ .

• Alkenes could cause large viscosity increase.

Dimer (sludge precursor)


Oxidation of TMPD : Alcohols

time (min)OH OH

OH

OH

Solvent (MeOH)

Conditions: Carbowax column, 50-250 ºC, 4 ºC min-1


Alcohols and viscosity increase

Alkanes

Weak interactions


Alcohols and viscosity increase

OH

OH

Alcohols may cause modest viscosity increase

Strong interactions (Hydrogen bonding)


Oxidation of Squalane

Micro-reactor conditions: 1000 mbar O2, 200 ºC, 2 mins

GC conditions: ZB-5 column, 50-300 ºC, 6 ºC min-1

Time (mins)


Products of Squalane Oxidation in Micro-Reactor: Ketones

O

O

O

O

Time (mins)


Products of Squalane Oxidation in the Micro-Reactor

+ Isomers

Time (mins)

Alkane

Alkene


Oxidation of TMPD : Fragmentation

.

time (min)

O

O

+

RH

O2


Oxidation of TMPD : Carboxylic acids

O

OH

O

OH

GC Conditions: FFAP column, 50-250 ºC4 ºC min-1

Time (mins)


Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids

OO

H O

HH

OH+



O

H

H

O

- .



O

O2

O

OO

. .



O

OO

O

OOH

. RH

O

OOH

O

OH


Oxidation of Squalane: Carboxylic acid detection by GC-MS

Carboxylic acids are difficult to detect directly by GC-MS.

Have been converted to esters.

O

OH

O

OMe

MeOH

H+

Carboxylic acid Ester


Oxidation of Squalane: Carboxylic acid detection by GC-MS

O

O

.O

OHO2

O

OMe

Detected by GC-MS

methylated


Oxidation of Squalane : Formation of Carboxylic Acids and Ketones (Infra-red spectroscopy)

Ketone peak Acid peak


Oxidation of Squalane : Formation of Carboxylic Acids and Ketones (Infra-red spectroscopy)

Ketone peak

After washing with KOH (aq)


XHVI™ 8.2 Oxidation in Engine

Conditions : Sump Oil Samples, 2000 rpm, 50 % throttleLubricant : XHVITM 8.2, 2 % (w/w) sulfonate detergent

0

2

4

6

8

0 20 40 60 80Time (hours)

Con

cent

ratio

n (1

0-3

mol

/ lit

re)

Total Carbonyl


Oxidation in Engine : Carbonyl vs. Acid

Conditions : Sump Oil Samples, 2000 rpm, 50 % loadLubricant : XHVITM 8.2, 2 % (w/w) sulfonate detergent

0

2

4

6

8

0 20 40 60 80Time (hours)

Con

cent

ratio

n (1

0-3

mol

/ lit

re)

Carboxylic AcidTotal Carbonyl


Carboxylic Acid : Total Carbonyl Ratio

0

20

40

60

80

100

0 20 40 60 80Time (hours)

[Ca

rbox

ylic

Aci

d]

[

Tota

l Ca

rbon

yl]

(%

)

Conditions : Sump Oil Samples, 2000 rpm, 50 % throttleLubricant : XHVITM 8.2, 2 % w/w sulfonate detergent


Squalane oxidation: Engine Test

Squalane + detergent was used as the lubricant in Ricardo-Hydra engine.

Samples collected from the sump and ring-pack.


Squalane oxidation: Engine Test

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0 50 100 150 200 250

Time (mins)

Co

nce

ntr

atio

n (

10-3

Mo

l/litr

e)

carb

on

yl

squalane

XHVI


Conclusions

Radical abstraction mainly occurs at tertiary sites. Alkenes very significant, possible sludge

precursors. Alcohols could give modest viscosity increase. Not predicted by previous work on model base

fluids


Conclusions

Radical abstraction mainly occurs at tertiary sites. Alkenes very significant, possible sludge

precursors. Alcohols could give modest viscosity increase. Not predicted by previous work on model base

fluids

Acknowledgements

Shell Global Solutions

john r. lindsay smith, moray s. stark, julian j. wilkinson

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