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

Department of Chemistry

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 jjw102@york.ac.uk www.york.ac.uk/res/gkg

Part 3: Chemical Mechanisms for the Oxidation of Branched Alkanes

Department of Chemistry

Aims

Identify products from micro-reactor oxidation.

Compare results to engine.Use identified products to propose

reaction mechanisms.Ultimately, understand and predict

viscosity increase

Department of Chemistry

Aims

Department of Chemistry

Chemical Mechanisms for the Oxidation of Branched Alkanes

Previous Work

Branched Alkanes as Base Fluid Models

Chemical Analyses

Reaction Mechanisms

Department of Chemistry

Summary of oxidation

Sludge

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

Hydroperox ide

A lkane

?

Viscosity Increase

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

+ ROO . .+ ROOH

Alkane Alkyl radical

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

+ ROO. .

+ ROOH

.+ O2

OO Alkane Alkyl radical

Hydroperoxy radical

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

+ ROO. .

+ ROOH

.+ O2

OO

OO

+ RH

OO

H

+ R.

Alkane Alkyl radical

Hydroperoxy radical

Hydroperoxide

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

OO

H

O

+ .OH

Hydroperoxide Alkoxy radical

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

OO

H

O

O + H

O

+ RH

OH

+ R.

Alkoxy radical Alcohol

Department of Chemistry

Traditional Model of Hydrocarbon Oxidation

O

+ H2O

OO

H

Hydroperoxide Ketone

Department of Chemistry

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

Department of Chemistry

Ease of abstraction of H atom

Department of Chemistry

Ease of abstraction of H atom

H Primary: Difficult

Department of Chemistry

Ease of abstraction of H atom

H

H

Primary: Difficult

Secondary: Moderately difficult

Department of Chemistry

Ease of abstraction of H atom

H

H

H

Primary: Difficult

Secondary: Moderately difficult

Tertiary: Easy

Department of Chemistry

Ease of abstraction of H atom

H

H

H

H

Primary: Difficult

Secondary: Moderately difficult

Allylic: Very easy

Tertiary: Easy

Department of Chemistry

Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average) 39(random example)

Department of Chemistry

Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average) 39

Trimethylheptane 10

(random example)

Department of Chemistry

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

Department of Chemistry

Trimethylheptane Oxidation : 100 – 120 °C

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

Department of Chemistry

Trimethylheptane Oxidation : 100 – 120 °C

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

Department of Chemistry

Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average) 39

Trimethylheptane 10

Hexadecane 16

(random example)

Department of Chemistry

Hexadecane Oxidation : 120 – 180 °C

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

OO H

Department of Chemistry

Hexadecane Oxidation : 120 – 180 °C

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

OO H

OO

H

OO

Department of Chemistry

Hexadecane Oxidation : 120 – 180 °C

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

OO H

OO

H

OO

OO

H

OO

H

Department of Chemistry

Hexadecane Oxidation : 120 – 180 °C

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

OO H

OO

H

OO

OO

H

OO

H

O OH

Department of Chemistry

Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average)

39 Trimethylheptane

10

Hexadecane

16

Tetramethylpentadecane

19

(random example)

(TMPD)

Department of Chemistry

Models of Hydrocarbon Base-Fluids

No. of Carbons

XHVI™ 8.2 (average)

39

Trimethylheptane 10

Hexadecane

16

TMPD

19

Squalane 30

(random example)

Department of Chemistry

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

Department of Chemistry

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

Department of Chemistry

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

Department of Chemistry

Oxidation of TMPD: Ketones

time (min)

O

(m/e = +14)

Ketone

impurity

Department of Chemistry

Oxidation of TMPD: Ketones

time (min)

O

(m/e = +14)

O

O

O

Department of Chemistry

Oxidation of TMPD: Alkanes

time (min)

Alkane

Department of Chemistry

Oxidation of TMPD: Fragmentation

time (min)

O

O

+ .

RH

Department of Chemistry

Oxidation of TMPD: Fragmentation

time (min)

+

O

O

Department of Chemistry

Oxidation of TMPD : Fragmentation

time (min)

+

O

O

Department of Chemistry

Oxidation of TMPD : Alkenes

time (min)

Department of Chemistry

Possible Mechanisms of Alkene Formation

OHH

OH+

Department of Chemistry

Possible Mechanisms of Alkene Formation

OH

O

OH

+ (H+)

OO

+ H2O

Alcohol AcidEster

Department of Chemistry

Possible Mechanisms of Alkene Formation

OO

OH

O

+

Acid

Ester

Alkene

Department of Chemistry

Alkenes and viscosity increase

Very Easy .

Monomer

Department of Chemistry

Alkenes and viscosity increase

.

+ .

• Alkenes could cause large viscosity increase.

Dimer (sludge precursor)

Department of Chemistry

Oxidation of TMPD : Alcohols

time (min)OH OH

OH

OH

Solvent (MeOH)

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

Department of Chemistry

Alcohols and viscosity increase

Alkanes

Weak interactions

Department of Chemistry

Alcohols and viscosity increase

OH

OH

Alcohols may cause modest viscosity increase

Strong interactions (Hydrogen bonding)

Department of Chemistry

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)

Department of Chemistry

Products of Squalane Oxidation in Micro-Reactor: Ketones

O

O

O

O

Time (mins)

Department of Chemistry

Products of Squalane Oxidation in the Micro-Reactor

+ Isomers

Time (mins)

Alkane

Alkene

Department of Chemistry

Oxidation of TMPD : Fragmentation

.

time (min)

O

O

+

RH

O2

Department of Chemistry

Oxidation of TMPD : Carboxylic acids

O

OH

O

OH

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

Time (mins)

Department of Chemistry

Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids

OO

H O

HH

OH+

Department of Chemistry

Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids

O

H

H

O

- .

Department of Chemistry

Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids

O

O2

O

OO

. .

Department of Chemistry

Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids

O

OO

O

OOH

. RH

O

OOH

O

OH

Department of Chemistry

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

Department of Chemistry

Oxidation of Squalane: Carboxylic acid detection by GC-MS

O

O

.O

OHO2

O

OMe

Detected by GC-MS

methylated

Department of Chemistry

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

Ketone peak Acid peak

Department of Chemistry

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

Ketone peak

After washing with KOH (aq)

Department of Chemistry

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

Department of Chemistry

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

Department of Chemistry

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

Department of Chemistry

Squalane oxidation: Engine Test

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

Samples collected from the sump and ring-pack.

Department of Chemistry

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

Department of Chemistry

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

Department of Chemistry

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