Biorefinery~Derived Long
Chain Dibasic Complexing
Agents for Lithium Thickened
Lubricating Grease
Paul A. Bertin, ~ and Paul A. Bessette*
tElevance Renewable Sciences, Woodridge, IL 60517 USA
tTriboscience and Engineering, Inc., Fall River, MA 02740 USA

Abstract
Elevance Renewable Sciences, through recent commercialization of Nobel Prize-winning catalytic
olefin metathesis of natural oils, can access novel long chain dibasic chemical building blocks from a
joint world-scale biorefinery with Wilmar International Limited. In this paper, the authors report the
feasibility of using specific long chain dibasic derivatives as complexing agent alternatives to azelaic
acid in synthetic lithium complex grease.

Introduction
In 2013, Elevance Renewable Sciences (ERS) announced the startup and shipment of commercial
products from a joint world-scale biorefinery with Wilmar International Limited located in Gresik,
Indonesia. The biorefinery was constructed based on proprietary Nobel Prize-winning olefin
metathesis technology capable of converting renewable natural oils (e.g. palm, soybean, canola,
mustard, algal, etc.) into high-value specialty difunctional molecules, olefins, and oleochemicals
with a capacity of 180 kMT. As shown in Figure 1, select ERS biorefinery products with potential
lubricant applications include PAO precursor 1 -decene and dimethyl octadecanedioate (DM-C 18), a
long chain a,w-functionalized linear diester. The objective of this work was to examine the feasibility
of using biorefinery-derived DM-C 18 as a complexing agent in lithium thickened grease. Neat
polyalphaolefin (PAO) was selected as a highly nonpolar base oil matrix to determine if inherent
physicochemical differences, such as reduced water solubility, between DM-C18 and industry
standard azelaic acid (C9) resulted in manifest differentiated base grease performance.
Select ERS

8~o~Derlved Lubn cant
Technoiogies

Products

eta heels
Biorefinery

1-decent

R Renewable Oil

Dtrncthyl Oc~d~canQd~o~atC
(R2 Me~ ~

I

~

I

Grease

Figure 1. (Left) Elevance joint biorefinery. (Right) Select ERS biorefinery products and potential
downstream bio-derived lubricant applications.
– 24 VOLUME 79, NUMBER 5

Background

favorable performance properties and manufacturing
process parameters despite generally less attractive
economics than adipic acid. It is significant to note that
longer chain complexing agents dodecanedioic acid (C12)
and DM-C18 have been reported to yield acceptable
lithium complex greases in mineral oil but widespread
adoption of these technologies have most likely been
hindered by even less favorable economics relative to
mid-chain alternatives. 6,7

Lithium complex greases represent nearly 40% of the
North American market and a minor yet emerging
proportion of global grease production.1 High operating
temperatures accompanying modern transportation
and industrial machinery often demand multipurpose
lithium complex greases to function due to higher
dropping points than simple soap alternatives. Complex
grease properties depend on the nature of the base oil,
thickener, and additive components with thickener
For years, the only commercial route to DM-C18 or
chemistry and process predominantly dictating high
the corresponding C18 diacid has been through a costly
temperature performance. Excluding borate ester
technology,2 thickener systems typically comprise lithium fatty acid fermentation biotechnology process. Metathesis
now provides a competitive industrial-scale alternative
carboxylate salts of 12-HSA and organic dibasic acids
and this preliminary study was initiated to identify if ERS
or esters. The salts are commonly formed in situ via
biorefinery-derived DM-C18 has the potential to expand
neutralization or saponification of the corresponding
the slate of economically viable complexing agents
acids or esters with lithium hydroxide during thickener
available to lithium grease manufacturers.
kettle processing. Since lithium is an alkali metal that
yields monovalent cations, it is generally accepted
Table 1. Physical properties of select linear a,w-diacids.
that “complexing” is not contingent on metaldirected assembly of 12-HSA and dibasic molecules
Water
into higher order networks but rather on strong
Carbon
Melting Point
Solubility
adsorptive interactions between their corresponding
Common Name
No.
(SC)
(gil)”
salts during co-crystallization in base oil. Thus, it
Adipic
6
153.0—153,1
is well-known that the physicochemical properties
Azelaic
9
107—108
2.1
of diacid complexing agents impact finished grease
Sebacic
10
134.0—134.4
1.0
performance characteristics and manufacturing
process parameters (e.g. one-step vs. two-step
Dodecanedioic
12
128.7—129
0.04
thickener formation).3’4
Octadecanedioic
18
124.6—124.8
0.00003c
“At 20-25 ~C unless otherwise noted. L~At 34.1 ~C. CUS EPA
Table 1 lists relevant properties such as melting
predicted value using EPI SuiteTh~.
points and water solubilities for a range of a,w
diacids with increasing chain lengths from adipic
(C6) to octadecanedioic (C18) acid.5 As expected, water
Experimental
solubility drops precipitously as chain length increases
Synfluid” PAO 6 cSt was obtained from Chevron
while melting points plateau between azelaic and sebacic
Phillips. Azelaic acid, 12-HSA, and lithium hydroxide
(C 10) acids with additional influences from even-odd
monohydrate (LiOH.H20) were obtained from
carbon number effects. For grease, it follows then that
commercial sources. Gas chromatography was used to
shorter chain complexing agents such as adipic acid
confirm DM-C18 in sample compositions. Saponification
would be more challenging to process and disperse in
number (SN) values were determined by ASTM D1387.
nonpolar base oils than longer chain counterparts due to
Three different samples of DM-C 18 complexing agents
decreased solubility of the corresponding lithium salts
of variable purity were synthesized from palm oil by
and greater susceptibility toward macroscopic phase
proprietary olefin metathesis biorefinery processes and
separation. Thus, mid-chain azelaic acid and to a lesser
hydrogenation: DM-C18-A (SN = 252), DM-C18-B (SN
extent sebacic acid are prevalent in grease owing to more
– 25 NLGI SPOKESMAN, NOVEMBER/DECEMBER 2015

256), and DM-C18-C (SN = 259). The samples were solids with melting points ranging from 56—60°C.
Fourier transform infrared (FT-IR) spectroscopy of each sample confirmed methyl ester functional groups
at 1739 cm-i.
Four laboratory scale lithium complex base greases were prepared for comparison. An azelaic acid
complex grease (1) served as a reference control for experimental greases (2-4) with the three DM-C18
complexing agents (A-C). For each batch, an open kettle two-step reaction scheme was used with total
thickener content fixed at 20% w/w. Ratios of i2-HSA to complexing agent were fixed at 2.7:1 (% wlw).
Table 2 shows formulation components for each. Grease preparation generally proceeded stepwise as
follows:
1) Total batch size (base oil + thickener) approximately 2500 g.
2) A portion of PAO 6 and all 12-HSA were added to the vessel and heated to 80°C (176°F) till a
homogeneous melt formed.
3) LiOH•H20 (1 equiv to 12-HSA) was mixed with deionized water (100 mL) and gently heated.
4) The aqueous base was then added to the oil solution under constant mechanical stirring and
heated to about 100°C (212°F) for 1 h to complete neutralization (Step 1).
5) The complexing agent was then added to the vessel followed by additional LiOHH2O
necessary to neutralize or saponify this dibasic acid or ester (Step 2).
6) The reaction was gradually heated to 200°C (392°F) to complete lithium soap thickener
formation and facilitate dehydration (and evaporation of methanol for DM-C1 8 samples).
7) Vessel contents were cooled by addition of the remaining PAO 6.
8) Upon cooling, base grease was finished by homogenization at 6000 psi.
Chemical and physical properties of each base grease are shown in Table 3.
=

Table 2. Grease formulations.
Grease 1

Grease 2

Grease 3

Grease 4

Component

Mass (g)

% w/w

Mass (g)

% w/w

Mass (g)

% w/w

Mass (g)

% w/w

PAO 6

2000

76.7

2000

77

2000

76.9

2000

76.9

12-HSA

365

14

365

14

365

14

365

14

LiOH~H2O

110

4.2

100

3.8

101

3.9

102

3.9

Azelaic Acid

134

5.1

DM-C18-A

134

5.2

DM-C18-B

135

5.2

DM-C18-C

134

5.2

Total

2609

100

2599

100

2601

100

2601

100

– 26 VOLUME 79, NUMBER 5

Table 3. Properties of lithium complex base greases in PAO 6.
(DM-C18-A)

Grease 3
(DM-C18-B)

(DM-C18-C)

Property

Method

Grease 1
(Azelaic Acid)

Color

Visuala

Light Gray

Off-White

Off-White

White

Appearance

Visuala

Slightly Grainy

Smooth

Smooth

Smooth

Dropping Point (°C)

ASTM D2265

>260

259

>260

254

Po(dmm)

ASTMD217

245

284

241

282

P50 (dmm)

ASTM D217

259

306

271

291

Plok(dmm)

ASTMD217

324

303

315

347

~ (Pjoic-Pso)

ASTM D217

65

-3

44

56

ASTM D6184

0.00%

0.31%

0.00%

0.00%

ASTM D5483

39.2 mm

37.2 mm

60.2 mm

108.3 mm

ASTM D1264

18.01%

9.63%

Water Spray Off

ASTM D4049

99.4%

90.3%

Thickener Chemistry

FT-IR

1579.7 cm1

1579.8 cm1

1579.9 cm1

1580.0 cm’

Oil Separation
(24 h at 100CC)
Thermo-oxidative
..

Stability
Water Washout
(79CC)

Grease 2

.

°See Figure 2.

Figure 2. Images of lithium complex base greases.
– 27 NLGI SPOKESMAN, NOVEMBER/DECEMBER 2015

Grease 4

Results and Discussion
Figure 2 shows a representative picture of each grease
prepared in this study. Notably, the smooth textures
of greases 2-4 with DM-C18 complex agents were
impressive given the highly nonpolar nature of PAO
6. Azelaic acid control grease 1 was slightly grainier
in comparison despite high pressure homogenization.
These observations suggest the reduced polarity of longer
chain Cl 8 complexing agents enabled greater thickener
dispersability in PAO which may lead to improved
formulation compatibility, manufacturing process
parameters (i.e. lower temperatures), and performance
properties.
All greases were compared by high temperature
performance, unworked and worked penetration, oil
separation, and thermo-oxidative stability using ASTM
methods (Table 3). FT-JR data for all samples confirmed
the formation of lithium carboxylate salt thickeners with
characteristic carbonyl stretching frequencies around
1580 cm-i. A dropping point >260°C (500°F) for baseline
control grease 1 with azelaic acid confirmed viability of
the selected two-step open kettle process for preparing
lithium complex greases. Experimental greases 2-4 had
dropping points well above simple lithium 12-hydroxy
stearate grease with sample 3 performing the best at
a value >260°C (500°F) indicating a thermally robust
thickener network. Furthermore, oil separation values
at elevated temperatures were negligible for all samples.
Greases 1 and 2 displayed similar oxidation onset times
by PDSC (ASTM D4583 @ 150°C and 500 psi) with
values trending higher for 3 and 4, respectively, indicating
improved oxidative stability over the baseline.
Consistencies for each grease were determined by
worked penetration after 60 strokes (P60) by ASTM
D217. Control grease 1 had the highest yield (i.e. the
lowest P60) with a penetration value of 259 dmm just
between NLGI Grade 2 (265—295 dmm) and Grade 3
(220—250 dmm). Greases 3 and 4 were NLGI Grade
2 with a higher yield for 3. Although grease 2 was not
confined to NLGI Grade 2, its mechanical stability
was impressive and noteworthy with a slightly firmer
consistency from 60 strokes to 10,000 strokes (PlOk-P60).

Further work is warranted to validate this result from
DM-Ci8-A.
Water resistance properties were compared between
base greases 1 and 3 with similar consistencies. The water
washout test (ASTM Di264) was used to evaluate the
ability of each lubricating grease to adhere to operating
bearings while a stream of hot water (79°C) impinges
the housing. Grease 3 with long chain complexing agent
DM-Ci8-B displayed a nearly two-fold improved water
washout value over azelaic control grease 1. A similarly
improved water spray off (ASTM D4049) result was also
observed for 3 compared to 1. The relatively poor values
for both samples in these tests were most likely due to low
base oil viscosity. Nevertheless, these data indicate that
the reduced polarity of longer chain complexing agents
(i.e. DM-C18) may enable the development of lithium
greases with improved water resistance.

Conclusions and Outlook
The results presented herein demonstrate that ERS
biorefinery-derived long chain dibasic esters are
attractive complexing agent alternatives to azelaic acid
for the preparation of lithium complex grease. Notably,
in neat PAO at constant soap concentrations and ratios
to 12-hydroxystearic acid (12-HSA), base greases with
DM-C18 exhibited comparable dropping points with
improved water resistance properties and oxidative
stability over an azelate control. Furthermore, the
long chain complexing agents yielded more uniform
and smoother greases than azelaic acid despite high
pressure homogenization suggesting improved thickener
dispersability which may enable less intensive process
parameters (i.e. time and temperature) during grease
manufacturing. Future work will be directed toward
optimization of thickener component ratios and grease
manufacturing processes to improve yields and allow
more extensive testing on fully formulated grease.

Acknowledgements
The authors would like to thank Courtnay Shaner and
Daniel Mubima of Elevance Renewable Sciences for
assistance in purification and characterization of DM-C18
samples.

– 28 VOLUME 79, NUMBER 5

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5)

6)
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29 NLGI SPOKESMAN, NOVEMBER/DECEMBER 2015