Fat-Based synthetic lubricants

Synthetic lubricants derived from fat-based materials are almost exclusively esters of the following type: (a) mono and dibasic acid esters, e.g., laurates, stearates of short chain aliphatic alcohols, azelates and sebacates of oxo alcohols; (b) polyalkylene glycols and glycol esters, e.g., triethyleneglycol dicaprylate caprate and others; (c) branched polyol or nucleic polyol esters derived from pentaerythritol or trimethylol alkanes and saturated short chained acid of the C₆, C₈, C₉ type; (d) triglycerides, specifically tailored by the rearrangement of two or more naturally occurring triglycerides. Among the unique but desirable characteristics of synthetic lubricants are: good lubricity, minimum viscosity change with temperature (high VI), low temperature fluidity, high thermal and oxidation stability, low volatility, excellent additive response, seal and gasket compatability and high fire and flash points.     

邻苯二甲酸酯的合成及其性能研究

以邻苯二甲酸酐和脂肪醇为原料,硫酸氢钠为催化剂酯化合成了一系列邻苯二甲酸酯。考察了脂肪醇的链长度、类型及支链醇含量等因素对合成酯性能的影响,进而得出其结构与性能的变化规律,并为高性能油品的合成提供理论依据。结果表明,随着脂肪醇链长的增加,合成酯的粘度和粘度指数逐渐增大,倾点和闪点也呈升高趋势;碳原子数目相同的支链醇酯较直链醇酯具有更高的粘度、倾点和闪点以及更低的粘度指数;在直链醇中引入支链醇,所得合成酯的粘度增大,粘度指数减小,倾点和闪点升高;且随着支链醇含量的增加,合成酯的粘度总体呈增大趋势,粘度指数逐渐减小,倾点和闪点呈锯齿型变化。     

Synthesis and physical properties of isostearic acids and their esters

Saturated branched‐chain fatty acids (sbc‐FAs) are found as minor constituents in several natural fats and oils. Sbc‐FAs are of interest since they have lower melting points than their linear counterparts and exhibit good oxidative stability; properties that make them ideally suited in a number of applications. We (and others) have previously synthesized sbc‐FAs by clay‐ or zeolite‐catalyzed isomerization of unsaturated linear‐chain fatty acids (ulc‐FAs) to unsaturated branched‐chain fatty acids (ubc‐FAs) that were subsequently hydrogenated to the desired sbc‐FAs. These acid‐catalyzed isomerization reactions, however, proceed in moderate conversion and selectivity. Recently, our group found that H‐Ferrierite zeolite catalyst isomerized ulc‐FAs to their branched‐chain counterparts in high conversion (>95%) and selectivity (85%). This paper reports the use of this type of catalyst for the preparation of a series of sbc‐FAs and their ester derivatives. Selected physical properties of these branched acids and esters such as cloud point (CP) and pour point (PP), cold filter plugging point (CFPP), viscosity index (VI), thermo‐oxidation stability, iodine value, and lubricity are also reported.     

Synthetic Base Stock Based on Guerbet Alcohols

Guerbet (β branched) alcohols of varying chain length of even carbon numbers were synthesized by using single linear fatty alcohols ranging from 1-octanol to 1-dodecanol. All Guerbet alcohols having fewer than 28 carbon atoms and are liquid at 0 °C due to β branching. Synthetic base oils were prepared by reacting commonly available unsaturated fatty acids and dicarboxylic acids with Guerbet alcohols using p-toluenesulfonic acid as a catalyst. These base oils were characterized by physical and tribological properties like viscosity, viscosity index, pour point, flash point, wear scar, weld load, coefficient of friction etc. and compared with commercially available 150 and 500 N base oils.     

The chemistry of dibasic and polybasic fatty acids

Current processes to produce dibasic and polybasic fatty acids including azelaic, sebacic, dodecanedioic, C₂₁ diacid, fatty dimer and trimer acids are discussed. A number of alternative routes to produce azelaic, sebacic and fatty dimers are also discussed, includeding the preparation of azelaic and sebacic acids from butadiene and sebacic acid from adipic acid. Physical properties of the various dibasic acids are compared. Preparation of important derivatives and their applications is discussed, including: (a) esters and polyesters as vinyl plasticizers and as base stocks for synthetic lubricants; (b) polyamide resins in coatings, fibres, inks and adhesives; (c) salts as surfactants; and (d) amido amines and imidazolines as corrosion inhibitors. Dimer acids have found application in the petroleum industry as drilling mud thickeners in oil recovery.     

Some fatty esters as plasticizers and fungicides for natural rubber

The prepared n-fatty alcohols from petroleum sources are esterified with a dibasic acid series (malonic, succinic, glutaric and adipic) or phthalic anhydride, giving the corresponding C₁₂ fatty esters. The prepared C₁₂ fatty esters were formulated with natural rubber. The drying time, some mechanical properties and fungitoxicity of the prepared film samples were examined. The conventional dibutyl phthalate plasticizer was used for the purpose of comparison. The data obtained indicate that the prepared fatty esters can be used as plasticizers with antifungal activity for natural rubber. ©1997 SCI     

Branched chain derivatives of alkyl oleates: Tribological,rheological, oxidation,and low temperature properties

We report the evaluation of four previously prepared oleochemical branched chain ethers (1–4) and soybean oil methyl esters (SME) against cloud point, pour point, oxidation stability, kinematic viscosity, specific gravity, lubricity, and surface tension. Ethers 1–4 exhibited excellent low temperature, oxidation stability, and lubricity behavior; however, at low blend levels (0.5, 1.0, 2.0 wt%) in SME, 1–4 had minimal impact on cloud point and pour point of SME. The specific gravity and surface tension behavior of 1–4 are nearly identical to SME. Ethers 1–4 displayed increased viscosity when compared to SME, but were still within ASTM D 6751 specifications at low blend levels in SME. Conversely, ethers 3 and 4 at 2.0% in SME were out of specification for kinematic viscosity in EN 14214. Both SME and 1–4 exhibited excellent tribological properties, as evidenced by HFRR wear scar behavior well within prescribed ASTM and CEN petrodiesel specifications.     

Application of metal triflate catalysts for the trans-esterification of Jatropha curcas L. oil with methanol and higher alcohols

This paper describes an experimental study on the application of metal triflate salts for the (trans‐) esterification of fatty esters (triolein, methyl oleate, methyl linoleate), fatty acid (oleic acid), as well as Jatropha curcas L. oil with methanol and higher alcohols (ethanol, n‐propanol, iso‐propanol, iso‐butanol, tert‐butanol). The effect of the metal type (scandium, bismuth, aluminium, lanthanum, copper, zinc) and process conditions on reaction performance were evaluated. Highest conversions were obtained with Al(OTf)₃. Reaction of triolein with methanol gave 99 mol% conversion at 165 °C for 1 h and the main product was the methyl ester. In addition, partial methoxylation of the carbon–carbon double bonds in the fatty acid chains was observed, though their fraction in the mixture was less than 20 mol%. The trans‐esterification reaction was also successfully performed using higher alcohols, giving >95 % conversions for ethanol, n‐propanol, iso‐propanol and iso‐butanol, whereas tert‐butanol was not reactive. For the reaction of oleic acid with methanol, quantitative esterification, partial methoxylation of the carbon–carbon double bonds and the formation of small amounts of a lactone was observed. The methodology using Al(OTf)₃ was successfully performed on the trans‐esterification reaction of JO (FFA content of 2.1 wt%) with various alcohols. Key properties (viscosity, pour point and cloud points) of the (branched) Jatropha esters were determined. The best cold‐flow properties were obtained for the iso‐propyl esters of JO, with cloud point and pour point of ?3 and ?24 °C, respectively.     

Use of branched-chain esters to reduce the crystallization temperature of biodiesel

To reduce the tendency of biodiesel to crystallize at low temperatures, branched-chain alcohols were used to esterify various fats and oils, and the crystallization properties of the branched esters were compared with those of methyl esters by using differential scanning calorimetry (DSC), cloud point, and pour point. Compared with the methyl esters that are commonly used in biodiesel, branched-chain esters greatly reduced the crystallization onset temperature (T_CO) of neat esters and their corresponding ester diesel fuel blends. Isopropyl and 2-butyl esters of normal (∼10 wt% palmitate) soybean oil (SBO) crystallized 7–11 and 12–14°C lower, respectively, than the corresponding methyl esters. The benefit of the branched-chain esters in lowering T_CO increased when the esters were blended with diesel fuel. Esters made from a low-palmitate (3.8%) SBO crystallized 5–6°C lower than those of normal SBO. Isopropyl esters of lard and tallow had T_CO values similar to that of methyl esters of SBO. DSC provided an accurate means of monitoring crystallization, and the DSC results correlated with cloud and pour point measurements.     

Lubricity-Enhancing Low-Temperature Diesel Fuel Additives

Branched chain alkyl esters have lower crystallization temperatures than those with straight chain headgroups. We investigated the effect of branched chain headgroups on the cold flow properties and lubricity of alkyl esters. Commercial grade canola methyl ester was transformed into branched chain alkyl esters through a two or three-stage base-catalyzed transesterification reaction with 1-methoxy-2-propanol and 3-methyl-1-butanol. Conversion rates between 85 and 95% were achieved. The alkyl esters exhibited improved cold flow properties. The pour points were reduced from −12 to −27 °C as a result of incorporating branched headgroups. Addition of 0.1 or 0.2% (v/v) 1-methoxy-2-propyl alkyl ester improved the lubricity of a commercial pre-production ultra low sulfur diesel (ULSD) fuel, as determined by increased lubricity number and reduced wear scar diameter. The inclusion of methyl-tert butyl ether or ethanolamides additives to ULSD containing alkyl esters had an antagonistic effect on lubricity. The branched-chain alkyl esters have the potential to be used as lubricity-enhancing and low-temperature fuel additives.     

Synthesis and Characterization of Potential Bio-Based Lubricant Basestocks via Epoxidation Process

Chemical modifications of vegetable oils may be applied for the purpose of improving their physicochemical properties in their usage for the bio-based lubricants. The vegetable oils with a high percentage of oleic acid, such as soybeans and rapeseed oils, are important raw materials to obtain the biolubricants. In this particular study, the oleic acid was esterified with 1-octanol, followed by epoxidation. The oxirane ring opening reaction was performed using different alcohol structures (linear, branched, and cyclic), in order to evaluate their influence on the final physicochemical properties with the synthesized samples. These aforesaid reaction steps were followed by ¹H nuclear magnetic resonance and the main physicochemical properties in the intermediate and final samples were assessed. The highest oxidative stability was observed for the samples obtained, using a cyclic alcohol at the oxirane ring opening reaction (230 min), followed by the linear alcohols with the branched alcohol presenting the lowest oxidative stability (124 min). The pour point values for the samples synthesized with the branched alcohol were slightly better than those with the linear and cyclic alcohols. All the synthesized samples showed high viscosity indexes (>130) and kinematic viscosities at 40 °C, ranging from 30 to 33 cSt (application degree ISO VG-32), which are adequate for their use in the formulation of bio-based lubricants.     

Synthesis of azelaic acid and suberic acid fromVernonia galamensis oil

We have demonstrated the potential ofVernonia galamensis seed oil as a source of dibasic acids. Reaction of nitric acid withV. galamensis oil afforded a homologous series of dibasic acids that include butanedioic acid, pentanedioic acid, hexanedioic acid (adipic), heptanedioic acid (pimelic), octanedioic acid (suberic), nonanedioic acid (azelaic), decanedioic acid (sebacic), and undecanedioic acid. Using a combination of chloroform extraction and subsequent water crystallizations, we have isolated suberic acid (∼95% purity by GC) and azelaic acid (∼95% purity by GC). The isolated yield of suberic acid is 15% and of azelaic acid is 11%. Reported reaction of nitric acid with ricinoleic acid (from castor oil) gave 8.8% suberic acid and 7.2% of a mixture of suberic and azelaic acids.     

Melting Points and Viscosities of Fatty Acid Esters that are Potential Targets for Engineered Oilseed

Our previous isolation of branched-chain fatty acid (BCFA) methyl esters from lanolin was improved and scaled up. Also, oleate esters of isopropanol, oleyl alcohol and normal alcohols of 1–12 carbons chain lengths were prepared. Esters were made by interesterification with sodium alcoholates and by esterification with Candida antarctica lipase. It proved easier to obtain pure esters by the enzymatic synthesis. Melting points and viscosities over the range of 0–70 °C were determined in order to better identify potential lubricant targets that might be produced by genetically modified oilseed crops. Isopropyl and butyl oleate have melting points of −33 and −32 °C, respectively and viscosities that range from ~17 cp (0 °C) to ~2.5 cp (70 °C). They should have suitable stability for lubricants. BCFA esters had viscosities similar to their straight chain analogs. Viscosities increased with alcohol chain length and decreased with temperature. The dependence of viscosity on temperature was fit with an equation based on Erying’s rate equation. Some esters with branched acid or branched alcohol moieties, and some oleate esters might be utilized as biolubricants or biofuels on the basis of their melting points and viscosities.     

Half esters of dibasic acids as additives in water-based cutting fluids

Several half esters from long chain dibasic acids were prepared, and corrosion and lubricity tests for these products as water-based cutting fluid additives were made. Triethanolamine salts of half esters of sebacic acid and dodecanedioic acid showed effective rust-inhibiting and anti-wear properties for water-based cutting fluids.     

甘油支化聚酯聚氯乙烯增塑剂的制备与性能研究

通过熔融缩聚的方法,以己二酸、二元醇、甘油作为第三单体合成了含有支化结构的聚酯增塑剂,探究了不同二元醇合成的支化聚酯,并按照一定配方将聚酯加入到聚氯乙烯（PVC）中制得PVC试片,利用傅里叶红外光谱分析、热重分析、高效凝胶色谱分析对支化聚酯进行了表征,对PVC试片进行拉伸性能、热稳定性能、耐抽出性能等性能测试。结果表明,二元醇为二缩三乙二醇时,产品相对分子质量为4871,分散系数为2.26,黏度为11.20 Pa·s,支化聚酯增塑的PVC试片断裂伸长率高于400 %,吸水量低,热稳定性高,耐抽出性能良好。     

Synthesis and Physical Properties of Tallow-Oleic Estolide 2-Ethylhexyl Esters

Tallow-oleic estolide 2-ethylhexyl (2-EH) esters were synthesized in a perchloric acid catalyzed one-pot process from industrial 90% oleic and tallow fatty acids at various ratios, while varying the ratio of tallow and oleic fatty acids, with the esterification process incorporated into an in situ second step to provide a functional fluid. Their viscosities ranged 57–80 cSt at 40 °C and 10.8–14.0 cSt at 100 °C with viscosity index (VI) 169–185. The 100% tallow estolide 2-EH ester had modest low-temperature properties (pour point = −15 °C and cloud point = −14 °C), while the 50:50 mixture of oleic and tallow fatty acids produced an estolide that had better low-temperature properties (pour point = −21 °C and cloud point = −21 °C) without a large negative effect on the oxidative stability. The oxidative stability increased as the amount of saturation increased (rotating pressurized vessel oxidation test (RPVOT) × 165–274 min). The tallow-oleic estolide 2-EH esters have shown remarkably low evaporative losses of only 1% loss compared to a 15–17% loss for commercial materials of similar viscosity grade. Along with expected good biodegradability, these tallow-oleic estolide 2-EH esters had acceptable properties that should provide a specialty niche. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Synthesis and Physicochemical Properties of Low Viscosity 2-Ethylhexyl Alkyl Ethers Made from Palm-Based Esters as Potential Biolubricant

A series of 2-ethylhexyl alkyl ethers (EHAE) are synthesized from palm-based esters via a one-step reaction under mild reaction conditions for potential usage as biolubricant. In this work, 2-ethylhexyl esters with varying fatty acid chain lengths are reacted with 1,1,3,3-tetramethyldisiloxane (TMDS), catalyzed by indium bromide (InBr₃) at 40 °C to afford EHAE with lauryl, palmityl, stearyl, and oleyl alkyl chain with 55–68% isolated yield. These compounds are characterized using Fourier-transform infrared (FTIR) and NMR spectroscopic methods and are evaluated for their viscosity, thermal, cold-flow, oxidative, and anti-wear properties. The synthesized EHAEs demonstrate low viscosity (1.65–2.55 cSt at 100 °C) with excellent viscosity indices (130–182). These EHAEs show comparable wear scar diameter (0.6–1.0 mm) in comparison with commercial mineral oil base stock (group I SN150) in the four-ball wear test. Thermal-oxidative investigation of the EHAE reveals that the thermal degradation temperatures are in the range of 200–250 °C and oxidation onset temperatures are between 165 and 184 °C. Among the EHAEs, 2-ethylhexyl lauryl ether with the shortest alkyl chain has the lowest pour point of ?27 °C. The physicochemical properties of synthesized EHAEs indicate that they are potential as biolubricant base stocks. Practical Applications : The EHAEs produced from this work exhibit promising physicochemical and lubricity properties, which offer great potential to be used as lubricant base stock especially for internal engine oil application.     

Potential synthetic lubricants: Esters of C18-saturated cyclic acids

A series of 16 esters of C₁₈-saturated cyclic acids (HCal) were prepared, and partial evaluation showed that several have qualities that recommend them as potential low-temp lubricants. Starting materials used were primary, straight, and branched chain alcohols C₄–C₇; perfluoro alcohols; phenol; cyclohexanol; and C₁₈-saturated cyclic alcohols prepared from cyclic acids. Viscosities were measured at −40, 100, and 210F. Their viscosity indexes ranged from 26 to 143. Pour points or melting points of the esters ranged from −27 to −96F. The oxidative stability of these esters measured at 347F according to a modification of the test method for military specification MIL-L-7808 was in nearly all cases equal or superior to the control bis-2-ethylhexyl sebacate. More severe oxidation tests showed the esters of HCal to be slower than the control in the development of acidic decomposition products. Presented at AOCS meeting, New Orleans, La., April 1964. A laboratory of the No. Utiliz. Res. and Dev. Div., ARS, USDA.     

Lubrication properties of trimethylolpropane esters based on palm oil and palm kernel oils

Due to the global drive towards biodegradable products, trimethylolpropane [2‐ethyl‐2‐(hydroxymethyl)‐1, 3‐propanediol] (TMP) esters based on palm and palm kernel oils were synthesized, their lubrication properties evaluated, and their potential as base stock for biodegradable lubricants assessed. Two types of TMP esters were considered: palm kernel (PKOTE) and palm oil (PPOTE) TMP esters, derived from palm oil and palm kernel methyl esters, respectively. Lubrication properties such as viscosity, viscosity index (VI) and pour point (PP) were determined according to methods of the American Society for Testing and Materials. Wear and friction properties were evaluated using a four‐ball test machine, while oxidative stability was studied with the Penn State Micro‐oxidation thin‐film test. High VI ranges between 170 to 200 were recorded for these base stocks. PP were relatively high, between 4 to —1 °C, but were improved to at least —33 °C in high oleic palm oil TMP esters. The effects of chemical structure and impurities on wear properties and oxidative stability were also studied. The presence of methyl esters was found to improve wear, but hydroxyl groups in mono‐ and diesters had negative effects at high concentrations. Differences in chemical structures of PKOTE and PPOTE were shown to affect friction and wear results. Both base fluids exhibit oxidative stability comparable to other high oleic base fluids.     

Synthesis and evaluation of some fatty esters as plasticizers and fungicides for poly(vinyl acetate) emulsion

n-Fatty alcohols (average molecular weight 187), prepared from n-paraffins, were treated with a series of dibasic acids such as malonic, succinic, glutaric, adipic and phthalic anhydride to give the corresponding fatty esters. The prepared fatty esters were formulated with poly(vinyl acetate) emulsion and used as films or textile coatings. Tests such as rate of drying, mechanical properties and resistance to micro-organisms were carried out. Samples of poly(vinyl acetate) plasticized with dibutyl phthalate were also prepared and evaluated for the purpose of comparison. The antifungal activity of these compounds was studied. The results obtained indicate that the prepared fatty esters can be used not only as plasticizers but also as fungicides and in some respects they are better than the conventional dibutyl phthalate plasticizer.