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Degradation of Ester Lubricants
Department of Chemistry
John R. Lindsay Smith, Edward D. Pritchard,
Moray S. Stark,* David J. Waddington
Department of Chemistry, University of York
York, YO10 5DD, UK
Degradation of Ester Lubricants
Part 2: The Oxidation of Polyol Esters
John R. Lindsay Smith, Edward D. Pritchard,
Moray S. Stark,* David J. Waddington
Department of Chemistry, University of York
York, YO10 5DD, UK
[email protected] www.york.ac.uk/res/gkg
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
Department of Chemistry
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
Model Compounds
O
O
neopentyl hexanoate
Department of Chemistry
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
neopentylglycol dibutanoate
O
O
O
O
Model Compounds
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
O
OO
O
O
O
neopentylglycol dibutanoate
O
O
O
O
TMP tributanoate
Model Compounds
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
O
OO
O
O
OO
OO
O
O
O
neopentylglycol dibutanoate TMP trihexanoate
O
O
O
O
TMP tributanoate
Model Compounds
Oxidation of Ester Lubricants
ReactorSteel : BS 316PTFE Stirrer
Conditions160 ºC0.5 cm3 lubricant4.4 cm3, 5 barA Oxygen
Department of Chemistry
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
O
OO
O
O
OO
OO
O
O
O
neopentylglycol dibutanoate TMP trihexanoate
O
O
O
O
TMP tributanoate
Model Compounds
Oxidation of Neopentylglycol Dibutanoate : GC Trace
O
O
O
O
time (min)
GC: Supelcowax, 30 m, 0.25 mm ID, 0.25 m,FID
time (min)
O
OH
O
OH
O
Oxidation of NPG Dibutanoate : Main Products
time (min)
O
OH
O
OH
O
OH
OH
Oxidation of NPG Dibutanoate : Diol Formation
Oxidation of NPG Dibutanoate : Hydroxyesters
time (min)
O
O
O
O
OH
O
O
O
O
O
O
O
O OH
Oxidation of NPG Dibutanoate : Esters of Hydroxyesters
time (min)
O
O
O
O
O
O
O
O
O
O
O
O
Oxidation of NPG Dibutanoate : α,β-Unsaturated Ester
time (min)
O
O
O
O
O
O
O
O
O
O
O
O
O
O
Formation of α,β-Unsaturated Ester
Department of Chemistry
Formation of α,β-Unsaturated Ester
O
O H
O
O
O O
Department of Chemistry
Formation of α,β-Unsaturated Ester
O
O H
O
O
O O
O
O
O
O
O
O
H+
Department of Chemistry
Oxidation of NPG Dibutanoate : Cyclic Acetal
time (min)
O
O
H
H
Formation of Cyclic Acetals
OH
OH
H H
O
..
Department of Chemistry
Formation of Cyclic Acetals
OH
OH
H H
O
..H
OH2+
OH
OH
..+ H+
Department of Chemistry
Formation of Cyclic Acetals
OH
OH
H H
O
..H
OH2+
OH
OH
..+ H+
O
O H
H
- H2O - H+
Department of Chemistry
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
O
OO
O
O
OO
OO
O
O
O
neopentylglycol dibutanoate TMP trihexanoate
O
O
O
O
TMP tributanoate
Model Compounds
Oxidation of TMP Tributanoate : GC Trace
O
OO
O
O
O
Oxidation of TMP Tributanoate : Main Products
OH
O
O
OO
OH
O
O
OO
O
O
O
Butanoic acid
TMP Dibutanoate
Oxidation of TMP Tributanoate : Transesterification
O
O
R' O
OO
O
O
O
O
OO
O
O
O
O
OO
O
O
O
H
TMP Dibutanoate monomethanoate
TMP Dibutanoate monoethanoate
TMP Dibutanoate monopropanoate
eg. methyl butanoate
Oxidation of TMP Tributanoate : Oxidation Products
OO
OO
O
O
O
O
O
O
O
O
O
O
O
Oxidation of TMP Tributanoate : Cyclic Acetal
O
O
O
H
H
O
0
0.5
1
1.5
0 5 10 15
time (hours)
con
cen
tra
tion
(m
ol/l
)
TMP dibutanoatebutanoic acid
Main Products of TMP Tributanoate Oxidation
O
OO
OH
O
OH
O
Department of Chemistry
0
0.5
1
1.5
2
0 5 10 15
time (hours)
con
cen
tra
tion
(m
ol/l
)
TMP dibutanoatebutanoic acidoxygen
Main Products of TMP Tributanoate Oxidation
O
OO
OH
O
OH
O
Department of Chemistry
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 5 10 15
time (hours)
conc
entr
atio
n (m
ol/l)
TMP dibutanoateTMP monopropanoateTMP monoethanoateTMP monomethanoate
Transesterification Products
O
OO
OH
O
O
OO
O
O
O
H
O
OO
O
O
O
O
OO
O
O
O
0
0.2
0.4
0.6
0.8
1
1.2
0 5 10 15
time (hours)
conc
entr
atio
n (m
ol/l)
butanoic acidpropyl butanoateethyl butanoatemethyl butanoate
Transesterification Products : II
OH
O
O
O
O
O
O
O
Department of Chemistry
Possible Hydrolysis of TMP Tributanoate?
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.2 0.4 0.6 0.8 1 1.2 1.4
butanoic acid + derivatives (mol/l)
TM
P d
ibut
anoa
te +
der
ivat
ives
(m
ol/l)
Department of Chemistry
Water Content During Autoxidation
OH
O
O
OO
OH
O
0
0.5
1
1.5
2
0 5 10 15
time (hours)
con
cen
tra
tion
(m
ol/l
)
TMP dibutanoatebutanoic acidoxygen
Department of Chemistry
0
0.5
1
1.5
2
0 5 10 15
time (hours)
con
cen
tra
tion
(m
ol/l
)
TMP dibutanoatebutanoic acidoxygenwater
Water Content During Autoxidation
OH
O
O
OO
OH
O
Department of Chemistry
TMP Tributanoate Oxidation : Viscosity Increase
8.8
9
9.2
9.4
9.6
0 1 2 3 4 5
time (hours)
visc
osi
ty (
@4
0 C
, cP
)
Viscosity Increase : Correlation with TMP Dibutanoate
O
OO
OH
O
O
OO
O
O
O
8.8
9
9.2
9.4
9.6
0 5 10 15 20
TMP dibutanoate % (mol/mol )
visc
osi
ty (
@4
0 C
, cP
)
Viscosity Increase : Correlation with TMP Dibutanoate
O
OO
OH
O
O
OO
O
O
O
8.8
9
9.2
9.4
9.6
0 5 10 15 20
TMP dibutanoate % (mol/mol )
visc
osi
ty (
@4
0 C
, cP
)
experimentalmodel mixture
Formation of High Molecular Weight Species
O
OO
O
O
O
mass : 344 mass430458516530544610630
Department of Chemistry
Formation of High Molecular Weight Species : II
O
OO
O
O
O
oxidation oxidation
+esterification
(-H2O)
mass : 344
mass : 430
radical attack
O
O
O
O
O
O
O
O
O
OO
O
O
O
O
(+ O2 - O)O
OO
O
O
O
OH
(+ RH)
O
OO
O
O
O
OH
OH
O
Formation of High Molecular Weight Species : III
O
OO
O
O
O
O
OO
O
O
H
oxidation
mass : 344
mass : 458
radical attack
O
OO
OH
O
O
O
O
OH
O
OH
O
O
OO
O
O
H
+
cleavageO
OO
O
O
O
O
O
O
+
(+ O2 - O)
Formation of High Molecular Weight Species : IV
O
OO
O
O
O
O
OO
O
O
H
O
OOH
O
O
O
O
O
O
O
OO
O
O O
oxidation oxidation
+(-H2O)
mass : 344
mass : 544
O
OO
O
O
OH
O
OO
O
O
OH
radical attack
esterification
Trimethylolpropane (TMP) Esters
O
OO
O
O
O
lubricant base fluid : TMP tridodecanoate
O
OO
O
O
OO
OO
O
O
O
neopentylglycol dibutanoate TMP trihexanoate
O
O
O
O
TMP tributanoate
Model Compounds
0
0.2
0.4
0.6
0.8
0 5 10 15
time (hours)
TM
P D
iest
er
(mo
l/l)
TMP Trihexanoate vs. TMP Tributanoate Oxidation
O
OO
O
O
O
O
OO
OH
O
0
0.2
0.4
0.6
0.8
0 5 10 15
time (hours)
TM
P D
iest
er
(mo
l/l)
TMP Trihexanoate vs. TMP Tributanoate Oxidation
O
OO
O
O
O
O
OO
O
O
O
O
OO
OH
O
O
OO
OH
O
Conclusions : Main Oxidation Mechanisms of Polyol Esters
Department of Chemistry
Conclusions : Main Oxidation Mechanisms of Polyol Esters
• Polyol Esters can decompose to the Diol and form Cyclic Acetals
Department of Chemistry
Conclusions : Main Oxidation Mechanisms of Polyol Esters
• Polyol Esters can decompose to the Diol and form Cyclic Acetals
• Triol Ester decomposition dominated by Hydrolysis- Transesterification
Department of Chemistry
Conclusions : Main Oxidation Mechanisms of Polyol Esters
• Polyol Esters can decompose to the Diol and form Cyclic Acetals
• Triol Ester decomposition dominated by Hydrolysis- Transesterification
• High molecular weight species formed by esterification of alcohol oxidation products
Department of Chemistry
Conclusions : Main Oxidation Mechanisms of Polyol Esters
• Polyol Esters can decompose to the Diol and form Cyclic Acetals
• Triol Ester decomposition dominated by Hydrolysis- Transesterification
• High molecular weight species formed by esterification of alcohol oxidation products
Acknowledgements
Peter Smith and Castrol
Department of Chemistry
