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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
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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 [email protected] www.york.ac.uk/res/gkg
Part 3: Chemical Mechanisms for the Oxidation of Branched Alkanes
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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
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Department of Chemistry
Aims
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Department of Chemistry
Chemical Mechanisms for the Oxidation of Branched Alkanes
Previous Work
Branched Alkanes as Base Fluid Models
Chemical Analyses
Reaction Mechanisms
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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
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
+ ROO . .+ ROOH
Alkane Alkyl radical
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
+ ROO. .
+ ROOH
.+ O2
OO Alkane Alkyl radical
Hydroperoxy radical
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
+ ROO. .
+ ROOH
.+ O2
OO
OO
+ RH
OO
H
+ R.
Alkane Alkyl radical
Hydroperoxy radical
Hydroperoxide
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
OO
H
O
+ .OH
Hydroperoxide Alkoxy radical
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
OO
H
O
O + H
O
+ RH
OH
+ R.
Alkoxy radical Alcohol
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Department of Chemistry
Traditional Model of Hydrocarbon Oxidation
O
+ H2O
OO
H
Hydroperoxide Ketone
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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
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Department of Chemistry
Ease of abstraction of H atom
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Department of Chemistry
Ease of abstraction of H atom
H Primary: Difficult
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Department of Chemistry
Ease of abstraction of H atom
H
H
Primary: Difficult
Secondary: Moderately difficult
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Department of Chemistry
Ease of abstraction of H atom
H
H
H
Primary: Difficult
Secondary: Moderately difficult
Tertiary: Easy
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Department of Chemistry
Ease of abstraction of H atom
H
H
H
H
Primary: Difficult
Secondary: Moderately difficult
Allylic: Very easy
Tertiary: Easy
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Department of Chemistry
Models of Hydrocarbon Base-Fluids
No. of Carbons
XHVI™ 8.2 (average) 39(random example)
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Department of Chemistry
Models of Hydrocarbon Base-Fluids
No. of Carbons
XHVI™ 8.2 (average) 39
Trimethylheptane 10
(random example)
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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
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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
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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
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Department of Chemistry
Models of Hydrocarbon Base-Fluids
No. of Carbons
XHVI™ 8.2 (average) 39
Trimethylheptane 10
Hexadecane 16
(random example)
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Department of Chemistry
Hexadecane Oxidation : 120 – 180 °C
Jensen et al, J. Am. Chem. Soc., 103, 1742 1981 and 101, 7574 1979
OO H
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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
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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
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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
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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)
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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)
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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
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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
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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
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Department of Chemistry
Oxidation of TMPD: Ketones
time (min)
O
(m/e = +14)
Ketone
impurity
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Department of Chemistry
Oxidation of TMPD: Ketones
time (min)
O
(m/e = +14)
O
O
O
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Department of Chemistry
Oxidation of TMPD: Alkanes
time (min)
Alkane
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Department of Chemistry
Oxidation of TMPD: Fragmentation
time (min)
O
O
+ .
RH
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Department of Chemistry
Oxidation of TMPD: Fragmentation
time (min)
+
O
O
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Department of Chemistry
Oxidation of TMPD : Fragmentation
time (min)
+
O
O
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Department of Chemistry
Oxidation of TMPD : Alkenes
time (min)
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Department of Chemistry
Possible Mechanisms of Alkene Formation
OHH
OH+
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Department of Chemistry
Possible Mechanisms of Alkene Formation
OH
O
OH
+ (H+)
OO
+ H2O
Alcohol AcidEster
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Department of Chemistry
Possible Mechanisms of Alkene Formation
OO
OH
O
+
Acid
Ester
Alkene
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Department of Chemistry
Alkenes and viscosity increase
Very Easy .
Monomer
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Department of Chemistry
Alkenes and viscosity increase
.
+ .
• Alkenes could cause large viscosity increase.
Dimer (sludge precursor)
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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
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Department of Chemistry
Alcohols and viscosity increase
Alkanes
Weak interactions
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Department of Chemistry
Alcohols and viscosity increase
OH
OH
Alcohols may cause modest viscosity increase
Strong interactions (Hydrogen bonding)
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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)
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Department of Chemistry
Products of Squalane Oxidation in Micro-Reactor: Ketones
O
O
O
O
Time (mins)
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Department of Chemistry
Products of Squalane Oxidation in the Micro-Reactor
+ Isomers
Time (mins)
Alkane
Alkene
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Department of Chemistry
Oxidation of TMPD : Fragmentation
.
time (min)
O
O
+
RH
O2
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Department of Chemistry
Oxidation of TMPD : Carboxylic acids
O
OH
O
OH
GC Conditions: FFAP column, 50-250 ºC4 ºC min-1
Time (mins)
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Department of Chemistry
Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids
OO
H O
HH
OH+
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Department of Chemistry
Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids
O
H
H
O
- .
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Department of Chemistry
Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids
O
O2
O
OO
. .
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Department of Chemistry
Reactions of Primary Alkyl Radicals : Formation of Carboxylic Acids
O
OO
O
OOH
. RH
O
OOH
O
OH
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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
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Department of Chemistry
Oxidation of Squalane: Carboxylic acid detection by GC-MS
O
O
.O
OHO2
O
OMe
Detected by GC-MS
methylated
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Department of Chemistry
Oxidation of Squalane : Formation of Carboxylic Acids and Ketones (Infra-red spectroscopy)
Ketone peak Acid peak
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Department of Chemistry
Oxidation of Squalane : Formation of Carboxylic Acids and Ketones (Infra-red spectroscopy)
Ketone peak
After washing with KOH (aq)
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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
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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
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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
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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.
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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
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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
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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