Synthesis and Characterization of Iso-Undecenoic and Iso

Chemical Sciences Division, CSIR-Indian Institute of Petroleum (CSIR-IIP), Dehradun 248005, Uttarakhand, India. Ind. Eng. Chem. Res. , 2017, 56 (26), ...
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Synthesis and Characterization of Iso-Undecenoic and IsoUndecanoic Acids Based Polyol Esters Sathyam Reddy Yasa,*,†,‡ Saravanan Krishnasamy,† Raj Kumar Singh,‡ and Vijayalakshmi Penumarthy*,† †

Centre for Lipid Research, CSIR-Indian Institute of Chemical Technology (CSIR-IICT), Hyderabad 500007, Telangana, India Chemical Sciences Division, CSIR-Indian Institute of Petroleum (CSIR-IIP), Dehradun 248005, Uttarakhand, India

‡

S Supporting Information *

ABSTRACT: The polymerization of 10-undecenoic acid (UDA) was carried out in the presence of montmorillonite K10 clay catalyst (5% of UDA) and deionized water (2.5% of UDA) at a temperature of 250 °C in an autoclave. The UDA polymerized product is a mixture of monomer acids (47−51%), dimer acids (30−32%), and higher polymeric acids (17−23%). The present study describes the isolation of less valuable monomer acids fraction (iso-undecenoic acid) through distillation from polymerization reaction product. This monomer acids fraction was found to be a mixture of iso-undecenoic acid (93−96%) and γ-undecalactone (4−7%) when analyzed by GC-MS. Monomer acids fraction was hydrogenated to also give hydrogenated monomer acids (iso undecanoic acids). Finally, the esterification of monomer and hydrogenated monomer acids fractions were done by the reaction with different polyols like neopentyl glycol (NPG), trimethylol propane (TMP), trimethylolhexane (TMH), and pentaerythritol (PE). Physicochemical and lubricant properties of all the synthesized polyol esters were evaluated including density, kinematic viscosity, pour point, flash point, thermal stability (TGA), oxidation stability (DSC), copper corrosion, weld load, and wear. All the synthesized polyol esters were found to be suitable as hydraulic fluids and automotive lubricants base stocks. Comparatively the iso-undecenoic acid based polyol esters were showed excellent pour point, viscosity-temperature properties, and good thermal stabilities, while the iso-undecanoic acid polyol esters showed good oxidation stability.

1. INTRODUCTION Polyol esters with aliphatic monocarboxylic acids are wellknown to be used as base stocks for the automotive, industrial, and turbine lubricants.1−3 However, they have lower thermo oxidative and hydrolytic stability than the mineral lubricant base stocks. Many type of polyols have been exploited so far such as neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol, tripentaerythritol, or mixtures thereof. As far as aliphatic monocarboxylic acids are concerned, many saturated and unsaturated fatty acids and their mixtures having the same or different chain lengths were reported to be used, but the polyol ester products with branched saturated and unsaturated fatty acids (iso-acids) exhibit many advantages over the simple straight chain saturated and unsaturated fatty acid esters, e.g., good oxidative and thermal stability.4−7 The branched fatty acid based polyol esters could be effectively utilized in hightemperature applications for lubrication resulting in extended equipment life, reduced maintenance, and increased efficiency.8−10 Because iso-unsaturated fatty acids (IUFAs) can be easily obtained by zeolite catalyzed skeletal isomerization of unsaturated fatty acids (UFAs) and also as byproducts in clay catalyzed polymerization of (UFAs) at high temperatures in the oleochemical industry,11−13 synthesis of polyol esters using © XXXX American Chemical Society

these iso-unsaturated fatty acids has become the area of interest for researchers in recent past, e.g., Ngo et al., have used isooleic acid to synthesize iso-oleic acid esters as lubricant base stocks by the reaction of different fatty alcohols, and they observed that the synthesized iso-oleic acid esters showed a lower pour point and cold flow properties and high thermal and oxidative stabilities.14 Beimesch et al. synthesized and studied lubricant properties of di- and tripentaerythritol esters of isostearic acid.15 10-Undecenoic acid (UDA) is a C11-carbon terminal monounsaturated fatty acid and is produced by pyrolysis of ricinoleic acid, the major fatty acid present in castor oil.16 Several studies showed that polymerization UDA and its methyl ester could be easily achieved in the presence of heat and lewis acid catalyst.17−20 Castor oil is readily available in India, so isoundecenoic monomer acids obtained as byproduct along with useful dimer and polymerized product could be a good feedstock for the polyol ester based base oil synthesis. To date, the isolation of a particular monomer acid (iso-undecenoic Received: April 26, 2017 Revised: June 5, 2017 Accepted: June 12, 2017

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DOI: 10.1021/acs.iecr.7b01760 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research

100 psi pressure, and stirred (500 rpm) at room temperature for 6−8 h, until the H2 gas was consumed. Excess H2 gas was discharged from the reactor, and the reaction mixture was filtered through Celite to remove the Pd−C catalyst. The Celite bed was washed with 200 mL of methanol. The hydrogenated monomer acid was concentrated under reduced pressure, and methanol was removed. The obtained hydrogenated monomer acid or iso-undecanoic acid was analyzed for iodine value (3−5 mg I2/100 g). 2.4. Synthesis of Polyol Esters of Iso-Undecenoic and Iso-Undecanoic Acids. NPG (100 g, 0.96 mol), monomer acid (531 g, 2.88 mol), and xylene (200 mL) were charged into a 2 L three-necked round-bottomed flask equipped with a thermometer, condenser, and a Dean−Stark apparatus. The reaction mixture was stirred at a temperature of 135−140 °C in the presence of PTSA (5.3 g, 1 wt % based on monomer acid) as a catalyst until the theoretical amount of water (34.6 mL) was collected. Then, the reaction mixture was cooled to 110− 115 °C, and xylene was removed under reduced pressure (0.01 kPa). The crude reaction product was extracted with ethyl acetate, washed with water to remove PTSA acid catalyst, passed through anhydrous sodium sulfate, concentrated using a rotary evaporator, and dried under reduced pressure. The obtained crude reaction product was subjected to short path distillation to remove excess monomer acid followed by passing through a basic alumina column to remove traces of monomer acid. The final compound MNPG, i.e., neopentyl ester of isoundecenoic acid, was obtained as a light yellow color viscous liquid (418.5 g, 96% yield). The product was analyzed for acid and hydroxyl values. A similar procedure was followed for synthesis of the TMP esters of iso-undecenoic acid (MTMP, 94% yield), TMH esters of iso-undecenoic acid (MTMH, 93% yield), and PE esters of iso-undecenoic acid (MPE, 93% yield). Further similar procedures were followed for the synthesis of the NPG esters of iso-undecanoic acid (HMNPG, 95% yield), TMP esters of iso-undecanoic acid (HMTMP, 94% yield), TMH esters of isoundecanoic acid (HMTMH, 94% yield), and PE esters of isoundecanoic acid (HMPE, 93% yield). 2.5. Characterizations. The synthesized monomer acids and polyolesters were characterized by FT-IR, 1H NMR, 13C NMR, and ESI-MS spectral methods. 1H NMR spectra were recorded using a Bruker AR-X 400 spectrometer (500 and 400 MHz). 13C NMR spectra were recorded in CDCl3 on a Varian spectrometer (125 MHz), and TMS was used as an internal standard. IR spectra were recorded in chloroform on a Thermo Nicolet Nexus 670 FTIR spectrometer or neat as thin film on NaCl transparent plates. The spectrum was recorded using DTGS KB detector in absorbance mode with the resolution of 4 cm−1. ESI-MS spectra were recorded on Waters (Model: QSTAR XL, Applied Biosystems, USA) Mass Spectrometer equipped with an Electrospray Ionization source. HPLC analysis was performed on Waters 2424 ELS, auto sampler 2707, pump-600 controller system equipped with an evaporative light-scattering detector (Alltech ELSD 2000, Deerfield, IL, USA). C-18 reverse phase column (250 mm × 4.5 mm, 5.0 μ particle size, Merck) was used for the analysis of the polyol esters of iso-undecenoic and iso-undecanoic acids by using the solvent system of acetonitrile and dichloromethane (60:40) at a flow rate of 1 mL/min, 30 min.2 2.5.1. Characterization of Monomer and Hydrogenated Monomer Acids. The distilled monomer fraction was characterized by converting it into a methyl ester. Distilled

acid) from the UDA polymerization reaction product and their characterization as well as the synthesis of iso-undecenoic acid (C11-iso-unsaturated fatty acid) polyol esters is not yet reported. In the present study, we have done the isolation of iso-undecenoic acid from the polymerized product of 10undecenoic acid. Iso-undecenoic acid was also hydrogenated to iso-undecanoic acid. Iso-undecenoic and iso-undecenoic acids based polyol esters were synthesized by reacting with neopentyl glycol (NPG), trimethylolpropane (TMP), trimethylolhexane (TMH), and pentaerythritol (PE), and after characterization, some physicochemical and lubricants properties of all these esters were evaluated.

2. MATERIALS AND METHODS 2.1. Materials. 10-Undecenoic acid, methanol, p-toluene sulfonic acid monohydrate (PTSA), xylene, aluminum oxide active basic, iodine monochloride (ICl), potassium hydroxide, potassium iodide, sodium thiosulfate, hydrochloric acid, sulfuric acid, sodium hydroxide (NaOH), and anhydrous sodium sulfate were procured from M/s SD. Fine chemicals Pvt., Ltd. (Mumbai, India). Neopentyl glycol (NPG), trimethylolpropane (TMP), and pentaerythritol (PE) were procured from SigmaAldrich (St. Louis, MO, USA). Trimethylolhexane (TMH) was synthesized in our lab by using reported method for synthesis of trimethylolpropane.21 Montmorillonite K10 (MK 10) clay was purchased from Fluka Chemika (USA). All solvents and chemicals were of reagent grade and used directly without further purification. Silica gel (60−120 mesh) for column chromatography was purchased from Acme Synthetic Chemicals, Mumbai, India. Precoated TLC plates were procured from Merck, Darmstadt, Germany. 2.2. Isolation of Monomer Acids from Polymerization Product of 10-Undecenoic Acid. 10-Undecenoic acid (800 g, 4.35 mol), MK 10 clay (40 g, 5 wt %), and deionized water (25 mL, 2.5 wt %) were placed into a 2 L high-pressure stainless-steel vessel (Parr Instrument, Moline, IL, USA) equipped with a mechanical stirrer and an electric heating mantle with a temperature controller. The vessel was sealed and purged with nitrogen gas (3 times), then heated to 250 °C, and the reaction continued for 6 h. Then, the reaction mixture was cooled to room temperature, MK 10 clay catalyst separated from the crude product by filtration through G3 funnel, and the catalyst residue washed with acetone (200 mL). The filtrate was dried by passing through anhydrous Na2SO4 and the solvent removed under reduced pressure to give the crude polymerized product as a light brown liquid (785 g).20 Short path distillation (SPD) was used to separate the low and high boiling components present in the reaction crude polymerized product. SPD unit (KDL 5) used was procured from M/s UIC-GmbH, Germany. The crude reaction mixture was subjected to SPD to separate monomeric fraction at a temperature of 160 °C with a vacuum of 1 × 10−3 kPa and yield was obtained in the range of 47−51%. The distillate collected in the SPD operation at 160 °C is a monomeric fraction, and the residue obtained in the SPD process mainly consists of a mixture of dimer, trimer, and higher poly acids. 2.3. Hydrogenation of Monomer Acid. The distilled monomer acid (or) iso-undecenoic acid (800 g, 4.30 mol) was transferred to a 2 L high-pressure stainless-steel autoclave along with 5 wt % Pd on activated carbon (40 g, 0.37 mol) and 200 mL of methanol. The reactor was attached to a hydrogen cylinder through a gauge (Parr Instrument), purged with hydrogen gas (H2) three times at 40 psi, charged with H2 to B

DOI: 10.1021/acs.iecr.7b01760 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

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Industrial & Engineering Chemistry Research

2.5.1.3. Iso-Undecanoic Acid Methyl Ester. Colorless liquid; neat FT-IR (cm−1, CHCl3): 2929, 2855, 1744 (−CO stretch of ester), 1436, 1194, 962; 1H NMR (CDCl3, 500 MHz) δ ppm: 0.91−0.81 (3.7H, m, (3.7 protons indicates the presence of branched and terminal methyl group)), 1.35−1.1.19 (14H, m), 1.67−1.54 (2H, m), 2.26 (2H, t, J = 8.0 Hz, CH2CO−), 3.64 (3H, s, −COOCH3); 13C NMR (CDCl3, 75 MHz) δ ppm: 174.24, 51.33, 39.32, 38.95, 36.78, 36.64, 36.48, 34.32, 34.05, 32.51, 32.37, 31.84, 29.65, 29.50, 29.40, 29.25, 29.21, 29.10, 27.90, 27.27, 26.84, 26.63, 25.34, 25.23, 24.91, 22.97, 22.62, 20.06, 19.54, 19.13, 14.31, 14.03, 11.32; ESI-MS (m/z) (M + K)+ (C12H24O2 + K)+ calculated 239.14; found 239.15. 2.5.2. Characterization of NPG, TMP, TMH, and PE Esters of Monomer Acid of UDA (or) Iso-Undecenoic Acid. 2.5.2.1. NPG Diester of Iso-Undecenoic Acid (MNPG). Light brown viscous liquid; yield 95.0%; FT-IR (cm−1, CHCl3): 2927, 2858, 1740, 1464, 1377, 1160; 1H NMR (400 MHz, CDCl3) δ ppm: 0.92−0.82 (br.t, 5H), 0.96 (s, 6H), 1.41−1.20 (m, 14H), 1.68−1.55 (m, 4H), 2.08−1.91 (m, 6H), 2.31 (t, 4H, J = 7.48 Hz, 2(−CH2−CO−)), 3.88 (s, 4H), 5.47−5.28 (m, 4H, (−CHCH−)2); 13C NMR (125 MHz, CDCl3) δ ppm: 13.62, 13.93, 13.96, 14.04, 14.07, 21.74, 22.16, 22.50, 22.61, 22.69, 24.42, 24.79, 24.94, 25.57, 26.97, 27.92, 28.61, 28.71, 28.79, 28.94, 29.05, 29.10, 29.15, 29.19, 29.27, 29.33, 29.39, 29.44, 29.49, 29.53, 31.37, 31.75, 31.91, 32.13, 32.22, 32.35, 34.13, 33.57, 34.27, 34.61, 68.99, 123.65, 124.59, 128.24, 127.17, 127.75, 131.73, 131.90, 132.01,173.69; ESI-MS (m/z): (M + Na)+ (C27H48O4 + Na)+ calculated 459.34, found 459.23. 2.5.2.2. TMP Triester of Iso-Undecenoic Acid (MTMP). Light brown viscous liquid; yield 94.0%; FT-IR (cm−1, CHCl3): 2927, 2858, 1742, 1462, 1383, 1157; 1H NMR (400 MHz, CDCl3) δ ppm: 0.92−0.82 (br.t, 10.6H), 1.41−1.21 (m, 22H), 1.70−1.55 (m, 8.5H), 2.08−1.91 (m, 8.6H), 2.30 (t, 6H, J = 7.48 Hz, 3(−CH2−CO−)), 4.01 (s, 6H), 5.49−5.27 (m, 6H, (−CH CH−)2); 13C NMR (125 MHz, CDCl3) δ ppm: 13.60, 13.94, 14.02, 14.05, 22.15, 22.59, 22.63, 22.97, 24.34, 24.75, 24.89, 25.54, 27.28, 27.80, 27.91, 28.57, 28.78, 28.92, 29.00, 29.10, 29.25, 29.23, 29.35, 29.42, 29.51, 29.67, 31.35, 31.45, 31.68, 31.71, 31.84, 32.09, 32.20, 32.32, 32.40, 32.48, 33.46, 34.01, 34.17, 34.64, 38.94, 40.54, 63.64, 123.62, 124.56, 129.38, 128.59, 128.11, 127.58, 126.98, 131.46, 131.78, 131.97, 131.99, 173.43; ESI-MS (m/z): (M + Na)+ (C39H68O6 + Na)+ calculated 655.50, found 655.41. 2.5.2.3. TMH Triester of Iso-Undecenoic Acid (MTMH). Light brown viscous liquid; yield 93.0%; ; FT-IR (cm−1, CHCl3): 2928, 2858, 1742, 1462, 1382, 1157; 1H NMR (500 MHz, CDCl3) δ ppm: 0.92−0.80 (br.t, 13H), 1.44−1.18 (m, 36H), 1.0−0.93 (m, 2H), 1.71−1.54 (m, 10H), 2.09−1.91 (m, 10H), 2.30 (t, 6H, J = 7.48 Hz, 3(−CH2−CO−)), 4.01 (s, 6H), 5.49−5.28 (m, 6H, (−CHCH−)2); 13C NMR (125 MHz, CDCl3) δ ppm: 13.95, 14.08, 22.42, 22.66, 24.94, 26.89, 27.33, 27.93, 29.15, 29.28, 29.46, 29.55, 29.71, 30.44, 31.38, 31.74, 31.87, 32.45, 33.52, 34.06, 34.34, 34.22, 38.97, 40.49, 64.05, 129.40, 129.07, 128.62, 127.61, 130.06, 130.43, 131.49, 131.80, 132.00, 173.47 ESI-MS (m/z): (M + Na)+ (C42H74O6 + Na)+ calculated 697.54, found 697.49. 2.5.2.4. PE Tetraester of Iso-Undecenoic Acid (MPE). Light brown viscous liquid; yield 95.0%; FT-IR (cm−1, CHCl3): 2927, 2858, 1745, 1462, 1384, 1155; 1H NMR (400 MHz, CDCl3) δ ppm: 0.92−0.82 (br.t, 10H), 1.0−0.93 (m, 2H), 1.44−1.20 (m, 29H), 1.72−1.54 (m, 11H), 2.09−1.91 (m, 12H), 2.30 (t, 8H, J = 7.48 Hz, 4(−CH2−CO−)), 4.11 (s, 8H), 5.49−5.27 (m, 8H, (−CHCH−)2); 13C NMR (125 MHz, CDCl3) δ ppm: 13.60,

monomer fraction (2 g) and methanol (50 mL) containing concentrated sulfuric acid (5 wt % based on monomer acid) were transferred into RB flask (100 mL), and the mixture was heated to reflux for 2−3 h and then cooled to RT. The mixture was then neutralized with the saturated Na2CO3 solution (50 mL) and extracted with ethyl acetate (2 × 50 mL), and the combined ethyl acetate extracts were washed with water. The organic layer was dried over anhydrous Na2SO4, and the solvent was removed by rota evaporator. The methyl ester of monomer fraction was checked by GC-MS. GC-MS analysis of iso-undecenoic acids fraction was performed on Agilent 6890 gas chromatograph with an HP-1 MS capillary column (30 m × 0.25 mm × 0.5 μm) connected to an Agilent 5973 mass spectrophotometer at 70 eV (m/z 50−600; source at 300 °C, and quadruple at 60 °C) in the EI mode. The oven temperature was programmed for methyl ester analysis of monomer acid as 60 °C for 2 min, raised at 10 °C/min to 300 °C, and then held for 20 min at 300 °C. The carrier gas helium at a flow rate of 1.0 mL/min was used for methyl ester of iso-undecenoic acid analysis. The pure monomer acid methyl ester was separated from the above-converted methyl ester of distilled monomer fraction by column chromatography using silica gel (60−120 mesh) with a hexane and ethyl acetate (99:1, v/v) solvent system as eluent, and γ-undecalactone was eluted with hexane and ethyl acetate (97.5:2.5, v/v). The column chromatography was monitored by TLC (SiO2) using hexane and ethyl acetate (9:1, v/v) as a solvent system, and the spots were identified by iodine vapor. The resultant methyl iso-undecenoate (93−95% yield) and γundecalactone (5−7% yield) were characterized by 1H and 13C NMR, ESI-MS, and GC-MS. 2.5.1.1. Iso-Undecenoic Acid Methyl Ester. Light yellow liquid; neat FT-IR (cm−1, CHCl3): 3005, 2928, 2856, 1742 (−CO stretch of ester), 1438, 1199, 968; 1H NMR (CDCl3, 500 MHz) δ ppm: 0.99−0.81 (4H, m, (4 protons indicates the presence of branched and terminal methyl groups formed during reaction)), 1.42−1.20 (8H, m), 1.72−1.55 (2.9 H, m), 2.09−1.91 (2.3H, m), 2.30 (2H, t, J = 7.5 Hz, CH2CO−), 3.67 (3H, s, −COOCH3), 5.49−5.27 (2H, m, allylic −CHCH−); 13 C NMR (CDCl3, 75 MHz) δ ppm: 11.3, 13.5, 13.8, 13.9, 14.0, 14.3, 17.8, 19.1, 22.1, 22.4, 22.5, 24.3, 24.6, 24.7, 24.9, 25.5, 26.8, 27.1, 27.2, 27.8, 27.9, 28.5, 28.6, 28.7, 28.9, 28.9, 29.0, 29.1, 29.1, 29.2, 29.5, 29.2, 29.3, 29.3, 29.4, 29.5, 29.6, 31.3, 31.6, 31.8, 32.1, 32.3, 32.4, 33.3, 33.9, 34.0, 34.1, 34.3, 34.6, 36.4, 38.9, 39.3,51.3, 127.7, 128.2, 128.7, 129.0, 129.0, 129.4, 129.6, 129.8, 130.1, 130.3, 130.8, 131.1, 131.4, 131.6, 131.8, 131.9, (−CHCH−, isomerized double bonded carbons), 174.2 (−CO); ESI-MS (m/z) (M + K)+ (C12H22O2 + K)+ calculated 237.12; found 237.08. 2.5.1.2. γ-Undecalactone (or) 5-Heptyldihydrofuran-2(3H)one. Colorless liquid; yield 5%; neat FT-IR (cm−1, CHCl3): 2927, 2856, 1777 (−CO stretch of γ-lactone), 1462, 1180, 1018; 1H NMR (CDCl3, 500 MHz) δ ppm: 0.82 (3H, t, J = 7.0 Hz), 1.58−1.46 (1H, m), 1.46−1.14 (10H, m), 1.70−1.61 (1H, m), 1.82−1.72 (1H, m), 2.27−2.18 (1H, m), 2.41 (2H, t, J = 9.3 Hz, OC−CH2), 4.37 (1H, quintet, J = 7.0 Hz, −CH−O); 13 C NMR (CDCl3, 75 MHz) δ ppm: 13.9, 22.4, 25.1, 27.8, 28.7, 29.0, 29.1, 31.6, 35.4, 80.9, 177.1; ESI-MS (m/z) (M + Na)+ (C11H20O2 + Na)+ calculated 207.13; found 207.14. Similarly, the obtained hydrogenated monomer acid or iso-undecanoic acid was analyzed by converting it in the corresponding methyl ester. C

DOI: 10.1021/acs.iecr.7b01760 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Figure 1. Diagrammatical representation for the synthesis of polyol esters of iso-undecenoic and iso-undecanoic acids.

26.65, 26.86, 27.30, 27.90, 29.11, 29.23, 29.25, 29.43, 29.52, 30.42, 31.84, 32.42, 32.51, 34.19, 34.30, 34.55, 36.50, 36.80, 38.94, 39.30, 40.46, 41.27, 41.46, 64.02, 173.42; ESI-MS (m/z): (M + Na)+ (C42H80O6 + Na)+ calculated 703.58, found 703.40. 2.5.3.4. PE Tetraester of Iso-Undecanoic Acid (HMPE). Light brown viscous liquid; yield 94.0%; FT-IR (cm−1, CHCl3): 2926, 2855, 1745, 1464, 1383, 1154; 1H NMR (500 MHz, CDCl3) δ ppm: 0.91−0.82 (m, 14H), 1.36−1.18 (m, 57H), 1.67−1.54 (m, 9H), 2.30 (t, 8H, J = 7.48 Hz, 4(−CH2− CO−)), 4.11 (s, 8H, 4 c −OCH2); 13C NMR (125 MHz, CDCl3) δ ppm: 11.25, 13.96, 14.26, 19.11, 19.53, 20.05, 22.58, 22.94, 24.82, 25.15, 26.61, 26.84, 27.26, 27.90, 29.09, 29.18, 29.22, 29.39, 29.49, 31.82, 32.40, 32.56, 34.04, 34.33, 36.51, 36.81, 38.95, 39.33, 41.93, 62.16, 173.03; ESI-MS (m/z): (M + Na)+ (C49H92O8 + Na)+ calculated 831.66, found 831.70. 2.6. Physico-Chemical Characteristics and Lubricant Properties. The synthesized polyol esters of iso-undecenoic and iso-undecanoic acids were evaluated for their physicochemical characteristics like acid value, hydroxyl value, density, specific gravity, kinematic viscosity, pour point, flash point, and copper corrosion using standard AOCS and ASTM methods. 2.6.1. Thermal Stability. Thermogravimetric analysis (TGA) studies were carried out in a nonisothermal mode using Q-500 TGA instrument of M/s TA Instruments to get the decomposition pattern of the base stocks. About 5 mg of the sample was taken in an aluminum crucible and heated slowly to 500 °C at a rate of 10 °C min−1 under a nitrogen atmosphere. The TGA degradation onset temperature was obtained by extrapolating the horizontal baseline and the intercept line with the tangent to the downward portion of the weight curve. 2.6.2. Oxidation Stability. Oxidation onset temperature of the synthesized polyol esters gives the oxidation stability in the presence of oxygen with respect to temperature, and it was determined with differential scanning calorimeter (DSC) according to ASTM E 2009−08. DSC analyses were conducted on Q-100 thermal analyzer M/s TA Instruments, under oxygen atmosphere. The DSC instrument was calibrated with pure

13.94, 14.05, 22.16, 22.59, 24.82, 24.78, 25.54, 27.29, 27.73, 27.91, 28.56, 28.68, 28.79, 28.98, 29.15, 29.24, 29.42, 29.52, 29.67, 31.36, 31.71, 31.84, 32.09, 32.30, 32.40, 32.48, 33.34, 33.88, 34.04, 38.94, 41.79, 62.08, 124.57, 127.46, 129.33, 128.50, 128.85, 129.03, 131.46, 131.86, 132.00, 132.08, 173.17; ESI-MS (m/z): (M + Na)+ (C49H84O8 + Na)+ calculated 823.61, found 823.79. 2.5.3. Characterization of NPG, TMP, TMH, and PE Esters of Iso-Undecanoic Acid (or) Hydrogenated Monomer Acid of UDA. 2.5.3.1. NPG Diester of Iso-Undecanoic Acid (HMNPG). Light brown viscous liquid; yield 96.0%; FT-IR (cm−1, CHCl3): 2926, 2855, 1741, 1464, 1378, 1160; 1H NMR (500 MHz, CDCl3) δ ppm: 0.88−0.82 (m, 7H), 0.96 (s, 6H), 1.35−1.20 (m, 26H), 1.66−1.58 (m, 4H), 2.31 (t, 4H, J = 7.48 Hz, 2(−CH2−CO−)), 3.88 (s, 4H, 2 × −OCH2); 13C NMR (125 MHz, CDCl3) δ ppm: 11.33, 14.05, 19.13, 21.71, 22.62, 24.94, 26.86, 27.28, 29.12, 29.21, 29.25, 29.42, 29.50, 31.83, 34.25, 36.49, 34.58, 68.95, 173.69; ESI-MS (m/z): (M + Na)+ (C27H52O4 + Na)+ calculated 463.37, found 463.34. 2.5.3.2. TMP Triester of Iso-Undecanoic Acid (HMTMP). Light brown viscous liquid; yield 94.0%; FT-IR (cm−1, CHCl3): 2926, 2855, 1743, 1464, 1382, 1156; 1H NMR (400 MHz, CDCl3) δ ppm: 0.93−0.82 (m, 14H), 1.52−1.18 (m, 42H), 1.66−1.54 (m, 7H), 2.30 (t, 6H, J = 7.48 Hz, 3(−CH2−CO−), 4.02 (s, 6H, 3 × −OCH2); 13C NMR (125 MHz, CDCl3) δ ppm: 11.33, 14.04, 19.13, 19.55, 20.07, 22.62, 22.97, 24.89, 25.22, 25.33, 26.63, 26.86, 27.28, 27.90, 29.10, 29.21, 29.25, 29.43, 29.51, 31.84, 32.38, 34.17, 36.49, 36.80, 38.93, 39.30, 40.53, 63.65, 173.43; ESI-MS (m/z): (M + Na)+ (C39H74O6 + Na)+ calculated 661.53, found 661.51. 2.5.3.3. TMH Triester of Iso-Undecanoic Acid (HMTMH). Light brown viscous liquid; yield 94.0%; FT-IR (cm−1, CHCl3): 2926, 2855, 1742, 1462, 1464, 1380, 1156; 1H NMR (400 MHz, CDCl3) δ ppm: 0.92−0.82 (m, 16H), 1.42−1.19 (m, 57H), 1.66−1.54 (m, 10H), 2.30 (t, 6H, J = 7.48 Hz, 3(−CH2− CO−)), 4.01 (s, 6H, 3 × −OCH2); 13C NMR (125 MHz, CDCl3) δ ppm: 11.33, 13.90, 14.04, 22.38, 22.62, 24.91, 25.06, D

DOI: 10.1021/acs.iecr.7b01760 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Figure 2. 1H NMR spectra of methyl iso-undecenoate.

Figure 3. 13C NMR spectra of methyl iso-undecenoate.

increment of 10 kg for a period of 1 min. The load at which the balls are welded or fused together is taken as the weld load of the product. 2.6.4. Wear. Wear of the products was determined by using a four-ball tester manufactured by Stanhope-Seta, U.K. as per ASTM D 4172 method. The point contact interface is obtained by rotating a 12.7 mm diameter steel ball under load against three stationary steel balls immersed in the lubricant. To evaluate the antiwear characteristics of lubricants, following wear scar diameters on the balls is measured.

indium, and an empty open aluminum pan was used to obtain the baseline correction. A small amount of sample (2.5−4.0 mg) was placed in open aluminum pan and oxygen flow was maintained at 50 mL min−1. The cell temperature was raised to 400 °C, at a heating rate of 10 °C min−1. The analysis was carried out in duplicate and the average of two measurements is reported. 2.6.3. Weld Load. Weld load of the products was determined by using a four-ball tester manufactured by Stanhope-Seta, U.K. as per IP 239 method. Out of four balls, three clean balls are placed in the ball cup securely, and the fourth ball is placed into the upper ball chuck. After the ball cup vessel filling with lubricant sample (7−8 g), the ball cup assembly is positioned centrally under the spindle in contact with the fourth ball. Then, the series of loads are applied on the weight pan with an

3. RESULTS AND DISCUSSION Iso-unsaturated fatty acids are important chemical intermediates were obtained by isomerization of unsaturated fatty acids in the presence of clay or zeolite catalyzed reactions. In this E

DOI: 10.1021/acs.iecr.7b01760 Ind. Eng. Chem. Res. XXXX, XXX, XXX−XXX

Article

Industrial & Engineering Chemistry Research

Scheme 1. Schematic Representation for the Synthesis of NPG, TMP, TMH, and PE Esters of Iso-Undecenoic and IsoUndecanoic Acids

Table 1. Physicochemical and Lubricant Properties of NPG, TMP, TMH, and PE Esters of Iso-Undecenoic Acid polyol esters of iso-undecenoic acid test total acid number (mg KOH/g) hydroxyl value (mg KOH/g) density (g/cm3) at 15 °C specific gravity (g/cm3) at 15 °C kinematic viscosity at (cSt) viscosity index (VI) pour point (°C) flash point (°C) copper corrosion weld load (kg) wear (mm) DSC oxidative onset temp. (°C) TGA degradation onset temp. (°C)

40 °C 100 °C

method

MNPG

MTMP

MTMH

MPE

AOCS Te 2a-64 AOCS Cd 13−60 ASTM D 4052 ASTM D 4052

0.5 0.5 0.9198 0.9206 13.20 3.49 150