Moray S. Stark,* John R. Lindsay Smith, Julian J. Wilkinson

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The Degradation of Hydrocarbons Base Fluids at
Elevated Temperatures
STLE 2006 Calgary 7th- 11th May 2006
Moray S. Stark, John R. Lindsay Smith, Julian J.
Wilkinson Department of Chemistry, University of
York, York YO10 5DD, UK
Department of Chemistry
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The Degradation of Hydrocarbons Base Fluids at
Elevated Temperatures
STLE 2006 Calgary 7th- 11th May 2006
Moray S. Stark, John R. Lindsay Smith, Julian J.
Wilkinson 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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The Degradation of Hydrocarbons Base Fluids at
Elevated Temperatures

• Chemical Mechanisms of Base Fluid Oxidation
• Viscosity Modelling of Oxidised Base Fluid

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Models of Hydrocarbon Base-Fluids
No. of Carbons XHVI 8.2 (average) 39
(random example)
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Models of Hydrocarbon Base-Fluids
No. of Carbons XHVI 8.2
(average) 39 Hexadecane 16
(random example)
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Traditional Alkane Oxidation Mechanism
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Traditional Alkane Oxidation Mechanism
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Traditional Alkane Oxidation Mechanism
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Traditional Alkane Oxidation Mechanism
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Traditional Alkane Oxidation Mechanism
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Traditional Alkane Oxidation Mechanism
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Models of Hydrocarbon Base-Fluids
No. of Carbons XHVI 8.2
(average) 39 Hexadecane 16
(random example)
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Models of Hydrocarbon Base-Fluids
No. of Carbons XHVI 8.2
(average) 39 Hexadecane 16 Pristane 19
(random example)
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Models of Hydrocarbon Base-Fluids
No. of Carbons XHVI 8.2
(average) 39 Hexadecane 16 Pristane
19 Squalane 30
(random example)
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Tertiary Carbons in Base-Fluids
S. McKenna, M. Casserino, K. Ratliff, Comparing
the Tertiary Carbon Content of PAOs and Mineral
Oils Presentation, STLE Annual Meeting, Houston,
2002
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Tertiary Carbons in Base-Fluids
S. McKenna, M. Casserino, K. Ratliff, Comparing
the Tertiary Carbon Content of PAOs and Mineral
Oils Presentation, STLE Annual Meeting, Houston,
2002
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Bench-Top Reactors
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Oxidation of Branched Alkanes GC Analysis
Pristane Oxidation 1000 mbar O2, 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)
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Oxidation of Branched Alkanes Alcohols
e.g.

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Oxidation of Pristane Tertiary Alcohols
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Oxidation of Pristane Secondary Alcohols
e.g.

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Oxidation Products Alcohols, Pristan-2-ol
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Oxidation Products Alcohols, Pristan-6-ol
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Oxidation Products Secondary Alcohols
e.g.
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Oxidation Products Ratio of Alcohols
e.g.
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Oxidation Products Ratio of Alcohols
e.g.
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Formation of Alcohols
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Formation of Alcohols
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Formation of Volatile Products
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Formation of Volatile Products

RH
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Formation of Volatile Products

RH
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Formation of Volatile Products

RH
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Oxidation of Branched Alkanes Pristanones
e.g.

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Formation of Volatile Ketones and Alkanes
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Formation of Volatile Ketones and Alkanes
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Formation of Volatile Ketones and Alkanes

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Reactions of Alkyl Radicals
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Reactions of Alkyl Radicals
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Reactions of Alkyl Radicals
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Reactions of Alkyl Radicals
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Reactions of Alkyl Radicals
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Formation of Volatiles Lactones

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Formation of Volatiles Lactones

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Lubricant Viscosity Increase During Use
Paris Taxis
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Viscosity Increase due to Lubricant Degradation

• Due to Formation of
• Polar Products
• Alcohols, Carboxylic Acids, etc.
• Polymeric Products
• Dimers, Trimers, etc. of Base Fluid
• Insoluble Products
• Aggregating Particles
• e.g. Soot, Micelles of Highly Polar Products

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Viscosity Increase due to Lubricant Degradation
Conditions Pristane (tetramethylpentadecane)
Oxidation in Flow Reactor Continuous O2 flow,
Sampling at 6 minutes, 150 - 210 ºC
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Viscosity Modelling Effect of Polar Products

• dodecane - docecanol model mixtures

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Viscosity Modelling Effect of Polar Products

• dodecane - docecanol model mixtures

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Viscosity Modelling Effect of Polar Products

• dodecane - docecanol model mixtures

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Viscosity Modelling Effect of Polar Products

• dodecane carboxylic acid model mixtures
• 11 propanpoic acid nonanoic acid

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Viscosity Modelling Effect of Polar Products

• dodecane carboxylic acid model mixtures
• 11 propanpoic acid nonanoic acid

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Viscosity Modelling Effect of Polar Products

• dodecane carboxylic acid model mixtures
• 11 propanpoic acid nonanoic acid

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Conclusions

• Chemical Mechanisms for Formation of
• Polar Products
• Volatile Products
• Viscosity Increase during Lubricant Oxidation
• NOT due to Polar Oxidation Products

Future Work

• Quantify Polymeric Products
• Examine Consequent Viscosity Change

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Acknowledgements

• University of Leeds Martin Priest, Peter Lee
• University of York Trevor Dransfield
• Shell Ian Taylor
• Infineum Chris Booth, Simon Chung
• Financial Support
• Shell Global Solutions, Infineum, EPSRC

Moray Stark
mss1_at_york.ac.uk
www.york.ac.uk/res/gkg
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The Degradation of Hydrocarbons Base Fluids at
Elevated Temperatures(Abstract for STLE 2006
Calgary 7th- 11th May 2006)
The Degradation of Hydrocarbons Base Fluids at
Elevated Temperatures   (Abstract for Talk for
STLE Annual Conference, Calgary, May
2006)   Moray S. Stark, John R. Lindsay Smith,
Julian J. Wilkinson Department of Chemistry,
University of York, York YO10 5DD, UK     To help
with the design of the next generation of
lubricants, it is necessary to understand how
they degrade during use as this partly determines
their useful lifetime. As part of a wider study
of this phenomenon, the degradation of
structurally simpler analogues of hydrocarbon
base fluids (branched alkanes squalane, C30H62
and pristine, C19H40) has been investigated under
controlled laboratory conditions at temperatures
representing sump to piston temperatures (100 to
230 C), and this work is reported here.
Degradation products have been identified by
GC-MS and quantified by GC and FTIR, with
chemical mechanisms proposed to account for the
formation of products such as carboxylic acids,
alcohols, ketones and alkenes, mostly formed via
radical attack on tertiary hydrogen atoms. The
viscosity change occurring during the oxidation
of these model base fluids has also been examined
and work is reported on trying to identify which
products cause the viscosity change observed.
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.