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Green Chemistry
Page 5 of 5
DOI: 10.1039/C6GC00579A
Journal Name
COMMUNICATION
The branched alkyl substituted cyclohexane 4i exhibited Octane (5 mL) was added to reduce the viscosity and ensure
higher viscosities but a lower VI than that of the corresponding good mixing in the Parr reactor during the reaction. The
linear alkyl substituted isomer 4e (entries 4 vs. 8). This is a reactor was sealed, flushed with nitrogen gas (2x), hydrogen
consequence of the high dependence of viscosity on gas (3x) and subsequently charged with the required pressure
temperature attributable to excessive branching of the of hydrogen gas. The Parr reactor was stirred at 500 rpm and
molecular structure. Notably, the volatility of 4i is subjected to respective conditions mentioned in Table 1,
exceptionally high (~10 fold) compared to that of 4e due to conditions B. The reaction mixture was cooled to room
decreased intermolecular interactions caused by increased temperature and filtered through a fritted funnel using
branching. The properties of the structurally similar lubricants hexanes as a washing solvent (3x20 mL) to remove the
4b, 4c and 4j, 4k derived from alkyl and furanic precursors, catalyst. The filtrate was concentrated under reduced pressure
respectively, were comparable (entries 1, 2 and 9, 10). Due to to recover cyclic alkanes
the high viscosities associated with 2-methylfuran-derived
4.
lubricant, 4l may be better suited for industrial applications
Acknowledgements
such as in wind turbines and compressors, rather than for
automotive use. Aromatic C30-lubricant 3b and the
corresponding cyclohexane analogue 5b have good viscosity
indices, pour points and oxidation stabilities, but poor
volatilities compared to those of commercial C30PAO (entries
12‒14). A comparison of volatilities of various C30 base-oils
(entries 3, 7, and 12‒14) suggests that this property does not
depend on the molecular weight alone but involves other
functionalities present in the molecular structure.
This work was funded by the Energy Biosciences Institute. The
authors would like to thank the analytical team as well as the
technology team of BP Castrol for evaluating the lubricant
properties of the compounds synthesized.
Notes and references
1
R. Buckhalt, in Society of Tribologists and Lubrication
Engineers, 1st January 2014.
S. Boyde, Green Chem., 2002, 4, 293-307.
P. Nagendramma and S. Kaul, Renewable and Sustainable
Energy Reviews, 2012, 16, 764-774.
In conclusion, we have developed a strategy for the highly
selective trimerization of methyl ketones to produce bio-
lubricants. The alkyl and furan-containing ketones required for
this process can be conveniently obtained from biomass and
the metal oxide catalysts employed are non-corrosive solids
(e.g., MgAlO). The cyclic alkane lubricants derived from this
method possess excellent pour points, viscosity indices, and
oxidation stabilities which are comparable to those of
conventional synthetic lubricants. A systematic structure-
property relationship study indicated that the viscosity index
of these materials increases steadily with length of alkyl side
chain. Conversely, the volatility of these compounds exhibits
an inverse dependence on alkyl chain length. Such
relationships are valuable for directing future research aimed
at developing renewable lubricants.
2
3
4
L. R. Rudnick, Synthetics, Mineral Oils, and Bio-Based
Lubricants: Chemistry and Technology, Second Edition, Taylor
& Francis, 2013.
5
6
S. Ray, P. V. C. Rao and N. V. Choudary, Lubrication Science,
2012, 24, 23-44.
P. Wasserscheid, S. Grimm, Randolf D. Köhn and M. Haufe,
Adv. Synth. Catal., 2001, 343, 814-818.
7
8
9
G. D. Yadav and N. S. Doshi, Green Chem., 2002,
F. Mo and G. Dong, Science, 2014, 345, 68-72.
Y.-F. Wang, Y.-R. Gao, S. Mao, Y.-L. Zhang, D.-D. Guo, Z.-L.
Yan, S.-H. Guo and Y.-Q. Wang, Org. Lett., 2014, 16, 1610-
1613.
4, 528-540.
10 A. Acosta-Ramirez, M. Bertoli, D. G. Gusev and M. Schlaf,
Green Chem., 2012, 14, 1178-1188.
11 J. T. Kozlowski and R. J. Davis, ACS Catalysis, 2013, 3, 1588-
1600.
12 P. Anbarasan, Z. C. Baer, S. Sreekumar, E. Gross, J. B. Binder,
H. W. Blanch, D. S. Clark and F. D. Toste, Nature, 2012, 491,
235-239.
13 E.-B. Goh, E. E. K. Baidoo, J. D. Keasling and H. R. Beller, Appl.
Environ. Microbiol., 2012, 78, 70-80.
14 M. Balakrishnan, E. R. Sacia, S. Sreekumar, G. Gunbas, A. A.
Gokhale, C. D. Scown, F. D. Toste and A. T. Bell, Proceedings
of the National Academy of Sciences, 2015, 112, 7645-7649.
15 E. R. Sacia, M. Balakrishnan, M. H. Deaner, K. A. Goulas, F. D.
Toste and A. T. Bell, ChemSusChem, 2015, 8, 1726-1736.
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Experimental
General procedure for MgAlO-catalyzed self-condensation of
ketones: A solution of
1 (20 g) in toluene (200 mL) was added
with MgAlO (20 g) in a 500 mL round bottom flask equipped
with a magnetic spin bar. The flask was then attached to the
Dean-Stark apparatus and refluxed with stirring (800 rpm) in a
pre-heated oil bath at conditions A given in Table 1. A
collection of by-product water was observed in the side-arm of
the apparatus during the course of the reaction. The product
mixture was then cooled to room temperature and filtered
through a fritted funnel by washing the catalyst using ethyl
17 H.-J. Chae, T.-W. Kim, Y.-K. Moon, H.-K. Kim, K.-E. Jeong, C.-
U. Kim and S.-Y. Jeong, Applied Catalysis B: Environmental,
acetate (3x100 mL). The products (2) in the filtrate were
2014, 150
18 W. Xu, Q. Xia, Y. Zhang, Y. Guo, Y. Wang and G. Lu,
ChemSusChem, 2011, , 1758-1761.
–151, 596-604.
recovered after evaporation of the solvents and used for the
next step without further purification.
4
General
procedure
for
hydrodeoxygenation
of
condensates: A solution of
2
(5 mmol) was added with
respective hydrogenation catalysts (metal loadings are
calculated with respect to ) in a 25 mL Parr reactor vessel.
2
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