Degradation of Ester Lubricants

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Degradation of Ester Lubricants
John R. Lindsay Smith, Edward D. Pritchard,
Moray S. Stark, David J. Waddington Department
of Chemistry, University of York York, YO10
5DD, UK
Department of Chemistry
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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
mss1_at_york.ac.uk
www.york.ac.uk/res/gkg
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Department of Chemistry
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
neopentyl hexanoate
Department of Chemistry
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
neopentylglycol dibutanoate
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
TMP tributanoate
neopentylglycol dibutanoate
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
TMP tributanoate
neopentylglycol dibutanoate
TMP trihexanoate
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Oxidation of Ester Lubricants
Reactor Steel BS 316 PTFE Stirrer Conditions 16
0 ºC 0.5 cm3 lubricant 4.4 cm3, 5 barA Oxygen
Department of Chemistry
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
TMP tributanoate
neopentylglycol dibutanoate
TMP trihexanoate
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Oxidation of Neopentylglycol Dibutanoate GC
Trace
GC Supelcowax, 30 m, 0.25 mm ID, 0.25 ?m,FID
time (min)
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Oxidation of NPG Dibutanoate Main Products
time (min)
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Oxidation of NPG Dibutanoate Diol Formation
time (min)
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Oxidation of NPG Dibutanoate Hydroxyesters
time (min)
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Oxidation of NPG Dibutanoate Esters of
Hydroxyesters
time (min)
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Oxidation of NPG Dibutanoate a,ß-Unsaturated
Ester
time (min)
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Formation of a,ß-Unsaturated Ester
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Formation of a,ß-Unsaturated Ester
Department of Chemistry
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Formation of a,ß-Unsaturated Ester
Department of Chemistry
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Oxidation of NPG Dibutanoate Cyclic Acetal
time (min)
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Formation of Cyclic Acetals
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Formation of Cyclic Acetals
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Formation of Cyclic Acetals
Department of Chemistry
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
TMP tributanoate
neopentylglycol dibutanoate
TMP trihexanoate
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Oxidation of TMP Tributanoate GC Trace
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Oxidation of TMP Tributanoate Main Products
Butanoic acid
TMP Dibutanoate
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Oxidation of TMP Tributanoate
Transesterification
TMP Dibutanoate monoethanoate
TMP Dibutanoate monomethanoate
eg. methyl butanoate
TMP Dibutanoate monopropanoate
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Oxidation of TMP Tributanoate Oxidation Products
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Oxidation of TMP Tributanoate Cyclic Acetal
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Main Products of TMP Tributanoate Oxidation
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Main Products of TMP Tributanoate Oxidation
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Transesterification Products
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Transesterification Products II
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Possible Hydrolysis of TMP Tributanoate?
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Water Content During Autoxidation
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Water Content During Autoxidation
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TMP Tributanoate Oxidation Viscosity Increase
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Viscosity Increase Correlation with TMP
Dibutanoate
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Viscosity Increase Correlation with TMP
Dibutanoate
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Formation of High Molecular Weight Species
mass 430 458 516 530 544 610 630
mass 344
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Formation of High Molecular Weight Species II
oxidation
oxidation
( O2 - O)
( RH)
radical attack
mass 344
esterification

(-H2O)
mass 430
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Formation of High Molecular Weight Species III
oxidation
cleavage
( O2 - O)
mass 344
radical attack


mass 458
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Formation of High Molecular Weight Species IV
oxidation
oxidation
radical attack
mass 344
esterification

(-H2O)
mass 544
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Trimethylolpropane (TMP) Esters
lubricant base fluid TMP tridodecanoate
Model Compounds
TMP tributanoate
neopentylglycol dibutanoate
TMP trihexanoate
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TMP Trihexanoate vs. TMP Tributanoate Oxidation
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TMP Trihexanoate vs. TMP Tributanoate Oxidation
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Conclusions Main Oxidation Mechanisms of Polyol
Esters
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Conclusions Main Oxidation Mechanisms of Polyol
Esters
Polyol Esters can decompose to the Diol and
form Cyclic Acetals
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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
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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
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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
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Abstract for STLE Conference Toronto, 17-20th
May 2004
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 e-mail
mss1_at_york.ac.uk Abstract for STLE Conference,
Toronto, May 2004, Lubricant Fundamentals
Section The oxidation mechanisms of the polyol
ester lubricant, trimethylolpropane (TMP)
tridodecanoate, and representative chemical
models (neopentylglycol dibutanoate, TMP
tributanoate, TMP trihexanoate) have been
studied. The esters of mono-alcohols are known to
decompose mainly via oxidation reactions,
analogous to those of alkanes. However, for diol
and triol esters, following initial oxidation,
the degradation is dominated by hydrolysis and
transesterification, with the acid formed by loss
of the acyl group being the major product. Two
previously unreported degradation/polymerisation
mechanisms of polyol esters have also been
observed. These involve reactions with aldehydes
(primary oxidation products) to form cyclic
acetals and, if the acid group is sufficiently
long, the oxidation of the acid chain to an
alcohol followed by the formation of lactones,
via attack of the hydroxyl group on the ester
linkage. The results from these studies are
important in the search for improved stability of
polyol ester lubricants.