Moray S. Stark,* Max Smethurst and Alexandra Neal

1
Degradation of Methyl Ester Analogues of
Vegetable Oils at Elevated Temperatures
STLE 2006 Calgary 7th- 11th May 2006
Moray S. Stark, Max Smethurst and Alexandra Neal
Department of Chemistry, University of York,
York YO10 5DD, UK
Department of Chemistry
2
Degradation of Methyl Ester Analogues of
Vegetable Oils at Elevated Temperatures
STLE 2006 Calgary 7th- 11th May 2006
Moray S. Stark, Max Smethurst and Alexandra Neal
Department of Chemistry, University of York,
York YO10 5DD, UK
mss1_at_york.ac.uk
www.york.ac.uk/res/gkg
3
Degradation of Methyl Ester Analogues of
Vegetable Oils at Elevated Temperatures

• Degradation of Diesel Biofuels
• In the Sump
• In Fuel Lines
• During Storage
• Models of Degradation of Vegetable Oil Based
  Lubricants
• As Analogues for the Oxidation of Alkenes
• Formed by Aldol Condensation of Aldehydes

Department of Chemistry
4
Oxidation of Methyl Esters

• Derived From Common Commercial Crop Oils

Methyl Palmate (e.g. Palm Oil) (Methyl
Hexadecanoate) Methyl Stearate (Methyl
Octadecanoate) Methyl Oleate (e.g. Olive
Oil) (methyl cis-9-octadecanoate) Methyl
Linoleate (e.g. Soya Oil) (Methyl
cis,cis-9,12-Octadecadienoate)
Department of Chemistry
5
Oxidation of Methyl Esters

• Derived From Common Commercial Crop Oils

Methyl Palmate (e.g. Palm Oil) (Methyl
Hexadecanoate) Methyl Stearate (Methyl
Octadecanoate) Methyl Oleate (e.g. Olive
Oil) (methyl cis-9-octadecanoate) Methyl
Linoleate (e.g. Soya Oil) (Methyl
cis,cis-9,12-Octadecadienoate)
Department of Chemistry
6
Bench-Top Reactors
Oxidation Conditions Sealed Reactor Initial
pressure 1000 mbar O2 Temperature 130 ºC 190
ºC Sampling Throughout the reaction 10 sec
10 hours
Department of Chemistry
7
Traditional Alkane Oxidation Mechanism
Department of Chemistry
8
Traditional Alkane Oxidation Mechanism
Department of Chemistry
9
Traditional Alkane Oxidation Mechanism
Department of Chemistry
10
Traditional Alkane Oxidation Mechanism
Department of Chemistry
11
Traditional Alkane Oxidation Mechanism
Department of Chemistry
12
Traditional Alkane Oxidation Mechanism
?H (C-H) 1 345 ? 5 411 ? 2 kJ
mol-1
1 Handbook of Chemistry and Physics, pp9.64
9.72, Vol 86, CRC, 2005
Department of Chemistry
13
Traditional Alkane Oxidation Mechanism
?H (C-H) 1 345 ? 5 411 ? 2 kJ
mol-1
1 Handbook of Chemistry and Physics, pp9.64
9.72, Vol 86, CRC, 2005
Department of Chemistry
14
Traditional Alkane Oxidation Mechanism
?H (C-H) 1 345 ? 5 411 ? 2 kJ
mol-1
1 Handbook of Chemistry and Physics, pp9.64
9.72, Vol 86, CRC, 2005
Department of Chemistry
15
Oxidation of Methyl Oleate GC Analysis
Oxidation Conditions 170 ºC, 20 minutes GC
conditions ZB-5 column, 50-340 ºC, 6 ºC
min-1 Product Identification EI-MS and CI-MS
Time (min)
Department of Chemistry
16
Oxidation of Methyl Oleate GC Analysis
Oxidation Conditions 170 ºC, 20 minutes GC
conditions ZB-5 column, 50-340 ºC, 6 ºC
min-1 Product Identification EI-MS and CI-MS
Time (min)
Department of Chemistry
17
Oxidation of Methyl Oleate GC Analysis
Oxidation Conditions 170 ºC, 20 minutes GC
conditions ZB-5 column, 50-340 ºC, 6 ºC
min-1 Product Identification EI-MS and CI-MS
x 6
Time (min)
Department of Chemistry
18
Oxidation of Methyl Oleate Epoxides
Time (min)
Department of Chemistry
19
Oxidation of Methyl Oleate Epoxides
Oxidation Conditions 170 ºC
Department of Chemistry
20
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
21
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
22
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
23
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
24
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
25
Epoxide Formation Mechanism
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586 M. S. Stark, J. Am. Chem. Soc. 2000, 122,
4162-4170 G. Lercker, et al., J. Chromatography
A. 2003, 985, 333-342
Department of Chemistry
26
Reactions of Alkoxyl Radicals (e.g. 11-alkoxyl)
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586
Department of Chemistry
27
Reactions of Alkoxyl Radicals (e.g. 11-alkoxyl)
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586
Department of Chemistry
28
Oxidation of Methyl Oleate Ketones and Alcohols
e.g.
e.g.
Time (min)
Department of Chemistry
29
Oxidation of Methyl Oleate Alcohols and Ketones
Oxidation Conditions 170 ºC
e.g.
e.g.
Department of Chemistry
30
Reactions of Alkoxyl Radicals (e.g. 11-alkoxyl)
Methyl-11-oxoundec-9-enoate
Heptyl radical
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586
Department of Chemistry
31
Reactions of Alkoxyl Radicals (e.g. 11-alkoxyl)
Methyl-11-oxoundec-9-enoate
Heptane
Heptanal
C. B. Whitlock, J. Am. Oil Chem. Soc., 1976, 53,
586
Department of Chemistry
32
Oxidation of Methyl Oleate Alkoxyl Fragmentation
Methyl-11-oxoundec-9-enoate
Heptanal
Heptane
Time (min)
Department of Chemistry
33
Oxidation of Methyl Oleate Volatile Products
Oxidation Conditions 170 ºC
Department of Chemistry
34
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
35
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
36
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
37
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
38
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
39
Formation of Alkoxyl Radicals
E. N. Frankel, W. E. Neff, W. K. Rohwedder,
Lipids, 1977, 12, 901-907 E. N. Frankel, et al.,
J. C. S. Perkin Trans. I, 1984, 2233
Department of Chemistry
40
Oxidation of Methyl Oleate Alkoxyl Fragmentation
Time (min)
Department of Chemistry
41
Oxidation of Methyl Oleate Dehydrodimers
e.g.
Time (min)
Department of Chemistry
42
Oxidation of Methyl Oleate Dehydrodimers
Time (min)
Department of Chemistry
43
Oxidation of Methyl Oleate Polymeric Products
Oxidation Conditions 170 ºC
e.g.
Department of Chemistry
44
Simulation of Methyl Oleate Oxidation

• Chemical Mechanism
• Based on 2-Butene Oxidation

Department of Chemistry
45
Simulation of Methyl Oleate Oxidation
MeO O2 gt allyl HO2 allyl O2 gt
allylO2 allylO2 MeO gt allylO2H
allyl allylO2H gt allylO OH allylO2 MeO gt
tepox allylO allylO2 MeO gt cepox
allylO allylO O2 gt allylket HO2 allylO
MeO gt allylOH allyl allyl allyl gt
dimer allylO2 allylO2 gt allylO allylO
O2 allylO2 allylO2 gt allylket allylOH
O2 HO2 MeO gt tepox OH HO2 MeO gt cepox
OH HO2 MeO gt allyl H2O2 OH MeO gt H2O
allyl allylO gt ald1 alkyl alkyl MeO gt
alkane allyl alkyl O2 gt alkylO2 alkylO2
MeO gt tepox alkylO alkylO2 MeO gt cepox
alkylO alkylO O2 gt ald2 HO2

• Chemical Mechanism
• Based on 2-Butene Oxidation
• 24 reactions
• 22 species (7 products)

Department of Chemistry
46
Simulation of Methyl Oleate Oxidation Epoxides
Oxidation Conditions 170 ºC
Department of Chemistry
47
Simulation of Methyl Oleate Oxidation Epoxides
Oxidation Conditions 170 ºC
Department of Chemistry
48
Simulation of Oxidation Alcohols and Ketones
Oxidation Conditions 170 ºC
e.g.
e.g.
Department of Chemistry
49
Simulation of Oxidation Alcohols and Ketones
Oxidation Conditions 170 ºC
e.g.
e.g.
Department of Chemistry
50
Conclusions

• Time Development of Oxidation Products Measured
• Epoxides of Dominant Products
• Epoxidation Dominant Fate of Peroxyl Radicals
• Fragmentation of Alkoxyl Radicals Also
  Significant
• Many Alkane Products Formed, Even in Presence
  of O2
• Chemical Kinetics Model of Oxidation Developed

Department of Chemistry
51
Future Work

• Link Viscosity Change to Product Formation
• Study Polymeric Products by HPLC-GPC
• Complete Computer Simulation of Oxidation
• Acknowledgements
• Trevor Dransfield (University of York) for
  GC-MS

Moray Stark
mss1_at_york.ac.uk
www.york.ac.uk/res/gkg
52
Degradation of Methyl Ester Analogues of
Vegetable Oils at Elevated Temperatures(Abstract
for STLE 2006 Calgary 7th- 11th May 2006)
Degradation of Methyl Ester Analogues of
Vegetable Oils at Elevated Temperatures   (Abstrac
t for Talk for STLE Annual Conference, Calgary,
May 2006)   Moray S. Stark and Alexandra
Neal Department of Chemistry, University of York,
York YO10 5DD, UK     There is great interest in
the development of lubricants derived from
vegetable oils, as these have the potential to
have many benefits in terms of biodegradability,
sustainability and performance. However, the
functional groups of vegetable oil derived
lubricants that give them their biodegradability
can also allow them to degrade during actual use,
via radical oxidation mechanisms. To try to aid
our understanding of the limits of vegetable oil
derived lubricants, the oxidation of methyl ester
analogues of vegetable oils (methyl stearate,
oleate and linoleate) at elevated temperatures
(110 -150ºC) has been examined experimentally
using GC-MS, and their relative rates of
oxidation established. The oxidation products
formed have also been identified, with chemical
mechanisms suggested to account for the observed
products, analogous to mechanisms previously
proposed for low temperature oxidation of
vegetable oils or high (combustion) temperature
mechanisms of alkene oxidation. Biography for
Presenting Author The presenting author has a BSc
and PhD in Physics, but has been working as a
Chemist for longer than he can remember. The past
few years have been spent specialising in the
study of the oxidation mechanisms of hydrocarbon
and ester lubricant base fluids and the effects
that oxidation has on the rheology of lubricants.