Mineral-based lubricants are being supplanted by bio-based lubricants because of environmental concerns and the depletion of fossil resources. The derivatives of edible and non-edible oils are considered potential alternatives to existing natural mineral oil base stocks in certain lubricant applications, where immediate intraction with the environment is predicted. A new class of epoxides were synthesized from the undecylenic esters of 2-ethyl hexanol, neopentyl glycol (NPG), and trimethylolpropane (TMP). These unsaturated esters were epoxidized by using meta chloro perbenzoic acid. The synthesized epoxides were characterized by spectral studies (1HNMR, 13CNMR, IR) physio-chemical (density, specific gravity) and lubricant properties (kinematic viscosity, viscosity index, flash point, fire point, cloud point, pour point, copper strip corrosion). TMP epoxide has a high viscosity index, high flash point, and low pour point compared to 2-ethyl hexyl epoxide and NPG epoxide.
Los lubricantes de base biológica están reemplazando a los lubricantes de base mineral debido a preocupaciones ambientales y al agotamiento de los recursos fósiles. Los derivados de aceite comestible y no comestible se consideran alternativas potenciales a las existencias base de aceite mineral natural existentes en ciertas aplicaciones de lubricantes, donde se predice una interacción inmediata con el medio ambiente. Se preparó una nueva clase de epóxidos a partir de ésteres a base de ácido undecilénico de 2-etilhexanol, neopentilglicol (NPG) y trimetilolpropano (TMP) mediante epoxidación con ácido metacloroperbenzoico como catalizador. Los epóxidos sintetizados se caracterizaron mediante estudios espectrales (1HNMR, 13CNMR, IR) las propiedades fisicoquímicas (densidad, densidad específica) y lubricantes (viscosidad cinemática, índice de viscosidad, punto de inflamación, punto de combustión, punto de enturbiamiento, punto de fluidez, tira de cobre). corrosión). El epóxido a base de éster de TMP tiene un índice de viscosidad alto, un punto de inflamación alto y un punto de fluidez bajo en comparación con el epóxido a base de éster 2-etilhexílico y el epóxido a base de éster NPG.
Lubricants have a tremendous application in day-to-day life, machine-driven and automobile industries. Most of the existing lubricant oils are non-degradable, causing a tremendous effect on the environment. There has been considerable interest in biodegradable lubricants from renewable resources as substitutes for conventional non-renewable mineral-based lubricants. Environmental concerns and the decrease of fossil fuel reserves have triggered great interest in developing bio-based lubricants from renewable resources.
The performance of an engine can be improved by using various edible and non-edible oil-based lubricants. Vegetable oils are renewable resources and are eco-friendly. Synthesized or modified vegetable oil lubricants have been proven to possess excellent lubricant properties for various applications (
The double bonds present in synthesized esters undergo auto-oxidation which is susceptible to degradation on prolonged use, thus decreasing the lubricant efficiency. To improve the lubricant efficiency, double bonds present in esters can be modified chemically by epoxidation reaction.
Oils with unsaturated fatty acids were epoxidized using different catalysts. H2SO4 was an effective catalyst for forming an oxirane ring in the presence of H2O2 across the double bonds in vegetable oils (
Epoxidized soybean oil exhibited improved low-temperature stability, thermo-oxidative stability friction and wear properties compared to existing lubricants (
2-Ethylhexanol, 2,2-Dimethylpropane-1, 3-diol (NPG) and 2-ethyl2-(hydroxyl methyl)-1, and 3-propanediol (TMP) were supplied by ACRO Organics, India. Basic aluminum oxide, dichloromethane (DCM), ethyl acetate, hexane and toluene were supplied by Finar, India. mCPBA (m-chloro per benzoic acid) was supplied by LOBA Chemie, India. Undecylenic acid (UDA) was supplied by SDFCL, Mumbai, India. Silica gel (60-120 mesh) was supplied by Fisher Scientifics, Ahmadabad, India. Sodium thiosulphate (Hypo) and anhydrous sodium sulphate were supplied by Fisher Scientifics, Mumbai, India. Sodium bicarbonate (NaHCO3) was supplied by Merck Specialties Pvt. Ltd., Mumbai, India. p-toluene sulphonic acid (pTSA) was supplied by AVRA labs, Hyderabad, India. All the above chemicals, required for synthesis, were used directly and without further purification.
A 1600 FT-IR Perkin-Elmer spectrometer (Norwalk, CT) was used for recording Infrared (IR) spectra with a liquid film between the NaCl cells. The streching frequencies of the IR spectra were measured in cm-1. A Brucker AVANCE 400 MHz spectrometer was used to record proton and Carbon - 13 Nuclear Magnetic Resonance Spectra (1H and 13C NMR) with respect to tetra methyl silane (TMS) an internal standard. The CDCl3 was used as solvent in 1H, 13 C NMR. The
Physico-chemical, and lubricant properties of synthesized esters and epoxy compounds were determined by standard ASTM (American standard testing method) methods. The density and specific gravity were tested by pycnometer at room temperature. The Kinematic viscosity at various temperatures (40 oC, 100 oC) was tested in a Kinematic viscosity bath. Flash point, and fire point were tested in a Clevland flash and fire point apparatus. Cloud, and pour point were tested in the automatic cloud and pour point apparatus. Copper strip corrosion was tested in the Copper strip corrosion bath. All the above apparatus were procured from culture instruments India LLP, Bengaluru, India.
1HNMR spectra: 0.8-9.0 (t, 6H, -CH3), 1.2-1.6 (m, 18H, -CH2-), 2.0-2.1 (m, 3H, C=C-CH2) and -CH(CH2)3), 2.3-2.4 (t, 2H, -CO-CH2-), 3.9-4.0 (m, 2H, -O-CH2-), 4.9-5.0 (m, 2H, CH=CH2), 5.7-5.8 (m, 1H, -CH=CH2).
13C NMR spectra: 66.5 (O-CH2), 115.10 (CH=CH2), 139.27 (CH=CH2), 173.44(C=O).
IR spectra: 3020 (str, C=C-H), 2929-2857 (str, -C-H), 1727 (str, C=O), 1217 (str, C-O-C), 771 (C-C).
1HNMR spectra: 0.9 (s, 6H, -CH3), 1.2-1.4(m, 20H, -CH2-), 1.5-1.6(m, 4H, -CO-CH2-CH2-), 2.0-2.1(q, 4H, -CH2-CH=CH2), 2.3-2.4(t, 4H, -CO-CH2-), 3.9(s, 4H, -O-CH2-), 4.9-5.0(m, 4H, -CH=CH2), 5.7-5.9 (m, 2H, -CH=CH2).
13C NMR spectra: 68.76 (O-CH2), 114.78 (CH=CH2), 139.09 (CH=CH2), 172.76 (C=O).
IR spectra: 3021(str, C=CH), 2927 (str, C-H), 1736 (str, C=O), 1214(str, COC), 755 (C-C).
1HNMR spectra: 0.8-1.0 (t, 3H, -CH3), 1.2-1.3(m, 30H, -CH2-), 1.3-1.4(m, 2H, CH3-CH2-), 1.5-1.7 (m, 6H, -CO-CH2-CH2-), 2.0-2.1 (q, 6H, -CH2-CH=CH2), 2.3-2.4 (t, 6H, -CO-CH2-), 3.9 (s, 6H, -O-CH2-), 4.9-5.0 (m, 6H, -CH=CH2), 5.7-5.8 (m, 3H, -CH=CH2).
13C NMR spectra: 63.32 (O-CH2), 114.20 (CH=CH2), 138.69 (CH=CH2), 171.97 (C=O).
IR spectra: 3021(str, C=CH), 2927 (str, C-H), 1741 (str, C=O), 1162 (str, COC), 758 (C-C).
1HNMR spectra: 0.9 -1.0 (t, 6H, -CH3), 1.2-1.4 (m, 19H, -CH2- and -CH(CH2-)3), 1.5-1.7 (m,2H,
13C NMR spectra: 68.17 (O-CH2), 46.43 (CHOCH2), 51.85 (CHOCH2), 173.20 (C=O).
IR spectra: 1724 (str, C=O), 1216 (str,
1HNMR spectra: 0.98 (s, 6H, -CH3), 1.3-1.4 (m, 24H, -CH2-), 1.4-1.5 (m, 4H,
13C NMR spectra: 68.56 (O-CH2), 46.44 (CHOCH2), 51.86 (CHOCH2), 172.94 (C=O).
IR spectra: 1727 (str, C=O), 1258 (str,
1HNMR spectra: 0.9 (t, 3H, -CH3), 1.3-1.4 (m, 32H,-CH2-), 1.4-1.5 (m, 6H,
13C NMR spectra: 68.19 (O-CH2), 46.49 (CHOCH2), 51.92 (CHOCH2), 172.89 (C=O).
IR spectra: 1738 (str, C=O), 1256 (str,
Vegetable oils and synthesized polyol esters possess good lubricity, high viscosity index, and flash point along with lower volatility. In vegetable oils, the presence of a high degree of unsaturation lowers thermal and oxidative stability, which can be improved by the chemical modification of unsaturation such as epoxidation. Epoxidized castor oil possesses enhanced lubricity properties such as high density, viscosity and low pour point (
1) 2-ethyl hexyl ester, 2) NPG ester and 3) TMP ester
1) 2-ethyl hexyl ester, 2) NPG ester and 3) TMP ester
1) 2-ethyl hexyl ester, 2) NPG ester and 3) TMP este
These esters were epoxidized using mCPBA in the presence of DCM. TLC is used to monitor the progress of the reaction. After completion, the reaction mixture was quenched with hypo and extracted with ethyl acetate. The organic layer (Ethyl acetate) was concentrated using a high vacuum to afford crude epoxide, and was purified by column chromatography.
The yields of synthesized epoxides were in the range of 70-75%. The epoxidized 2-ethyl hexanol, NPG and TMP based esters (Scheme-1) were characterized using 1HNMR (
a) 2-ethyl hexyl epoxide, b) NPG epoxide and c) TMP epoxide
a) 2-ethyl hexyl epoxide, b) NPG epoxide and c) TMP epoxide
a) 2-ethyl hexyl epoxide, b) NPG epoxide and c) TMP epoxide
The existence of
Properties | Methods | 2-ethyl hexyl epoxide* | NPG epoxide* | TMP epoxide* |
---|---|---|---|---|
Density (g/cc) | - | 1.0351 ± 0.0004 | 1.0446 ± 0.0006 | 1.1606 ± 0.0006 |
Specific gravity | - | 1.0351 ± 0.0004 | 1.0446 ± 0.0006 | 1.1606 ± 0.0006 |
Moisture | - | 0.0025 | 0.0021 | 0.002 |
Viscosity (40oC) cSt | ASTM D445 | 10.08 ± 0.025 | 37.34 ± 0.32 | 260 ± 0.325 |
Viscosity (100oC) cSt | ASTM D445 | 2.98 ± 0.269 | 7.6 ± 0.16 | 39.3 ± 0.485 |
Viscosity index (VI) | ASTM D2270 | 169 | 177 | 204 |
Flash point (oC) | ASTM D92 | 164 ± 2 | 270 ± 6 | 308 ± 2.1 |
Fire point (oC) | ASTM D92 | 173 ± 2.2 | 285 ± 0.066 | 314 ± 0.0723 |
Cloud point (oC) | ASTM D2500 | -3.9 ± 0.1 | -1.8 ± 0.2 | 3 ± 0.152 |
Pour point (oC) | ASTM D97 | -35 ± 4 | -25 ± 1.96 | -12.5 ± 1.75 |
Copper strip Corrosion | ASTM-D-130 | 1a | 1a | 1a |
*Data correspond to the mean of three determinations plus or minus standard deviation. The values are expressed as mean ± standard deviation (n=3)
The values are expressed as mean ± standard deviation (n=3).
The results of inhibition zone values for 2-ethyl hexanol ester, NPG ester and TMP ester and corresponding epoxides against bacterial strains such as
The synthesized epoxides showed an excessive viscosity index, flash point and lower volatility than the respective esters (
Properties | 2-ethyl hexyl ester* | NPG Esters* | TMP ester* |
---|---|---|---|
Density (g/cc) | 0.9051 ± 0.0002 | 0.9283 ± 0.0001 | 1.0046 ± 0.0001 |
Viscosity (40oC) cSt | 1.89 ± 0.01 | 10.51 ± 0.02 | 17.52 ± 0.02 |
Viscosity (100oC) cSt | 0.89 ± 0.01 | 3.31 ± 0.02 | 4.71 ± 0.02 |
Viscosity index | 47.08 | 212.89 | 207.619 |
Flash point (oC) | 138 ± 0.82 | 254 ± 0.82 | 286 ± 0.82 |
Fire point (oC) | 147.75 ± 0.96 | 263.75 ± 0.96 | 294 ± 0.82 |
Cloud point (oC) | -10.78 ± 0.19 | -8.43 ± 0.10 | -0.65 ± 0.13 |
Pour point (oC) | -38.50 ± 0.29 | -35.53 ± 0.38 | -33.48 ± 0.28 |
Copper strip Corrosion | 1a | 1a | 1a |
*Data correspond to the mean of three determinations plus or minus standard deviation. The values are expressed as mean ± standard deviation (n=3)
Properties | Castor methyl estera | Rapeseed oilb | Karanja oilc | HP Lube parthan SL220@ |
---|---|---|---|---|
Viscosity at 40oC (cSt) | 35.81 | 86.74 | 256 | 241.9 |
Viscosity at 100oC (cSt) | - | 12.72 | 28 | 31.34 |
Viscosity index | - | 145 | - | 173 |
Pour point(oC) | 8 | -12 | 3 | -45 |
Flash point(oC) | 138 | 239 | - | 250 |
Copper strip Corrosion | 1ª | 1a | 1a | 1a |
a
Kinematic viscosity at 40 oC for NPG epoxide is 37.34 cSt. It is in the range of ISO VG 32 and 46 grades. Standard ISO VG 32 and 46 grades are widely used machinery lubricating oil and turbine oil. Kinematic viscosity at 40 oC for TMP epoxide is 260 cSt, which is in the range of standard ISO VG 220 and 320 grades. The Standard ISO VG 220 and 320 grades are widely used in machinery lubricating oil, bearing oils for steel plants and industrial gear oils.
The synthesized 2-ethyl hexanol epoxide, NPG epoxide and TMP epoxide can replace the existing mineral-based lubricating oils of ISO VG 32-46, ISO VG 220-320 grades in the market for machinery, turbine and industrial gear oil applications. The synthesized 2-ethyl hexanol epoxide, NPG epoxide and TMP epoxide is from a renewable source and is biodegradable without polluting the environment. These are recommended for all industrial machinery and other machine parts lubricated by a thin film of oil for anti-friction bearings, plain bearings, drive gears and the pinions of steel mills, where operating conditions are moderate.
The study involved a new class of epoxides synthesized from undecylenic esters as a bio lubricant base-stock. Undecylenic esters of 2-ethyl hexanol, NPG and TMP were epoxidized using mCPBA. The yields of 2-ethyl hexanol epoxide, NPG epoxide and TMP epoxide were in the range of 70-75%.
TMP epoxide showed higher viscosity, higher viscosity indices, higher cloud point, lower pour point, higher flash point, and higher fire point than 2-ethyl hexyl and NPG epoxide. 2-ethyl hexanol epoxide, NPG epoxide and TMP epoxide have superior lubricant properties compared to their corresponding esters.
2-ethyl hexanol epoxide, NPG epoxide and TMP epoxide with high viscosity indices, higher flash point, and lower pour points can be exploited for automotive and hydraulic fluid formulations. Undecylenic esters and their epoxides can be used for numerous applications due to their non-toxicity and biodegradability.
The authors sincerely thank the management, GITAM (Deemed to be University), Department of chemistry and acknowledge the Department of Science and Technology (DST), Technology System Development Programme (TSDP) Government of India, for financial assistance to Synthesis of Renewable Non-Toxic Bio-Degradable Lubricants for Engine Application (DST/TSG/AF/2014/01) and also the Department of Lipid Science and Technology, Indian Institute of Chemical Science (IICT), Hyderabad for 1H and 13CNMR and IR spectral data.