Low-temperature properties of alkyl esters of tallow and grease

The low-temperature properties of mono-alkyl esters derived from tallow and recycled greases were determined for neat esters and 20% ester blends in No. 2 low-sulfur diesel fuel. Properties studied included cloud point, pour point, cold filter plugging point, low-temperature flow test, crystallization onset temperature, and kinematic viscosity. Compositional properties of the alkyl esters determined included water, residual free fatty acids, and free glycerol content. In general, the secondary alkyl esters of tallow showed significantly improved cold-temperature properties over the normal tallow alkyl ester derivatives. The low-temperature flow test did not show a 1:1 correlation with cloud point as previously observed with methyl soyate and methyl tallowate. For the homologous series methyl to n-butyl tallowate, ethyl tallowate had the best broad-spectrum low-temperature properties, both neat and when blended in diesel fuel. For the greases studied, both the normal and branched alkyl ester derivatives showed improved properties over corresponding tallow esters, especially with neat esters.     

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.     

Reducing the crystallization temperature of biodiesel by winterizing methyl soyate

Methyl soyate, made from typical soybean varieties, has a crystallization onset temperature (T _co) of 3.7°C and, as a biodiesel fuel, is prone to crystallization of its high-melting saturated methyl esters at cold operating temperatures. Removal of saturated esters by winterization was assessed as a means of reducing theT _co of methyl soyate. Winterizing neat methyl esters of typical soybean oil produced aT _co of −7.1°C, but this was not an efficient way of removing saturated methyl esters because of the low yield (26%) of the separated liquid fraction. However, aT _co of −6.5°C with 86% yield was obtained by winterizing the neat methyl esters of a low-palmitate soybean oil; aT _co of −5.8°C with 77% yield was obtained by winterizing methyl esters of normal soybean oil diluted with hexane.     

Thermal analysis of alternative diesel fuels from vegetable oils

The relatively poor cold-flow properties of monoalkyl esters of vegetable oils and animal fats (biodiesel) present a major obstacle to their development as alternative fuels and extenders for combustion in direct injection compressionignition (diesel) engines. In this work, differential scanning calorimetry (DSC) heating and cooling curves of methyl soyate (SME), methyl tallowate (TME), SME/TME admixtures, and winterized SME were analyzed. Completion of melt, crystallization onset (Onset), and other temperatures corresponding to melting and freezing peaks were correlated to predict cloud point (CP), pour point (PP), cold filter plugging point (CFPP), and low-temperature flow test (LTFT) data. Effects of treating methyl esters with cold-flow improvers were examined. Low-temperature flow properties of biodiesel may be accurately inferred from subambient DSC analyses of high-melting or freezing (β-form) peaks. The temperature of maximal heat flow for freezing peaks gave the best accuracy for predicting CP, PP, and CFPP, while freezing point gave the best accuracy for predicting LTFT. Onset also gave good correlations with respect to predicting PP, CFPP, and LTFT. Cooling scan parameters were more reliable than heating scan parameters. Presented at the 88th American Oil Chemists’ Society’s Annual Meeting & Expo, Seattle, Washington, May 11–14, 1997.     

Glycerolysis of fats and methyl esters

The glycerolysis of methyl esters and triglycerides with crude glycerol, a coproduct from the transesterification of triglycerides, was studied. Three procedures were followed for this conversion. The first procedure was a one-step glycerolysis with methyl esters. The second procedure was a two-step process. This procedure involved an initial partial glycerolysis with methyl esters, followed by fat glycerolysis. The third procedure was a simultaneous glycerolysis with methyl esters and triglycerides. In the glycerolysis with methyl esters, the removal of methanol is vital to the production of mono- and diglycerides. Methanol was removed either by drawing vacuum on the reactor or by stripping methanol out by means of an inert carrier gas (nitrogen). Different molar ratios of methyl esters to glycerol were tested in the first two processes. At low concentration of methyl esters, total conversion of methyl esters to mono- and diglycerides was achieved. As the concentration of methyl esters was increased, the conversion of methyl esters to mono- and diglycerides was decreased. Furthermore, the ratio of mono- to diglycerides was also higher at lower concentrations of methyl esters. The conversion of triglycerides in the two-step process with crude glycerol was similar to a one-step fat glycerolysis with pure glycerol. The composition of different components and the ratio of mono- to diglycerides were also comparable.     

Thermodynamic study on cloud point of biodiesel with its fatty acid composition

A thermodynamic study was made for binary mixture of various fatty acid methyl esters to establish a prediction model for the cloud point of actual biodiesel fuel from various feedstocks. When considering a eutectic system for ester mixture, measured values of cloud point were fitted well with a theoretical curve according to solid–liquid equilibria, even though an ideal solution was assumed. A simple model to agree with experimental results was, thus, proposed for predicting the cloud point of actual biodiesel. Through this study, it was found that cloud point of biodiesel could be determined only by the amount of saturated fatty acid methyl esters regardless of composition of unsaturated esters.     

Biodiesel production from waste frying oil in sub- and supercritical methanol on a zeolite Y solid acid catalyst

Waste frying oil (WFO) is a very important feedstock for obtaining biodiesel at low cost and using WFO in transesterification reactions to produce biodiesel helps eliminate local environmental problems. In this study biodiesel was produced from WFO in sub- and super-critical methanol on a zeolite Y solid acid catalyst. The procedure was optimized using a design of experiments by varying the methanol to WFO molar ratio, the reaction temperature, and the amount of catalyst. Typical biodiesel yields varied from 83 to nearly 100% with methyl esters content ranging from 1.41–1.66 mol·L^-1 and typical dynamic viscosities of 22.1-8.2 cP. Gas chromatography was used to determine the molecular composition of the biodiesel. The reaction products contained over 82 wt-% methyl esters, 4.2 wt-% free acids, 13.5 wt-% monoglycerides, and 0.3 wt-% diglycerides. The transesterification of WFO with methanol around its critical temperature combined with a zeolite Y as an acid catalyst is an efficient approach for the production of biodiesel with acceptable yields.     

The addition of alkoxy side-chains to biodiesel and the impact on flow properties

Butyl biodiesel was synthesised from canola oil and subsequently epoxidised via the in situ peroxyacetic acid method converting 45% of the unsaturated portion. Alkoxy butyl biodiesel was synthesised under acid conditions with a range of both straight-chain and branched alcohols. Alkoxylation of butyl biodiesel with methanol, ethanol and n-propanol did not improve the cloud or pour point over that for conventional methyl biodiesel. Alkoxylation with alcohols larger than butanol including n-pentanol, n-hexanol and n-octanol produced cloud points that were 5 °C lower than that for methyl biodiesel. The lowest cloud point achieved was for 2-ethylhexoxy butyl biodiesel at −6 °C, representing a 6 °C reduction in cloud point over methyl biodiesel. Alkoxylation did not have a significant effect on the pour point of biodiesel. Alkoxylation of butyl biodiesel resulted in significant increases in viscosity. The kinematic viscosity generally increased with increasing alkoxy chain length and ranged from 6.67 mm² s⁻¹ for methoxy butyl biodiesel to 9.76 mm² s⁻¹ for ethylhexoxy butyl biodiesel, more than double the value for methyl biodiesel. The improved low-temperature properties of the longer-chain alkoxy biodiesel were most likely due to the protruding alkoxy chain, which also resulted in an increase in viscosity. The use of alcohols larger than pentanol does not provide significant benefit in terms of low-temperature properties, and results in an undesirable increase in viscosity.     

Minimizing the Cost of Biodiesel Blends for Specified Cloud Points

When used as a biodiesel fuel, isopropyl esters are expensive compared to the more common methyl esters. However, isopropyl esters have better cold flow properties than methyl esters, allowing the use of highly saturated feedstocks such as tallow or lard. It has not been determined if isopropyl esters can be part of an economical biodiesel (B100) blend for a specified cloud point, which allows for an objective material cost comparison. This work explores this question through the use of an empirical cloud point model that has been developed and validated. Constrained cost minimization was performed using the cloud point model and historical prices for alcohols and triglycerides. Case studies using 2003 and 2006 average prices are presented. The results indicate that an expensive component such as isopropyl ester can be part of an economical blend under the market conditions. For isopropyl esters to be feasible as an economical blend component, they have to be derived from a highly saturated feedstock that is less expensive than soybean oil by $0.10/lb. This price differential is most applicable to a biodiesel blend that has a cloud point between 5 and 10 °C.     

Production of biodiesel through optimized alkaline-catalyzed transesterification of rapeseed oil

Present work reports an optimized protocol for the production of biodiesel through alkaline-catalyzed transesterification of rapeseed oil. The reaction variables used were methanol/oil molar ratio (3:1-21:1), catalyst concentration (0.25-1.50%), temperature (35-65 °C), mixing intensity (180-600 rpm) and catalyst type. The evaluation of the transesterification process was followed by gas chromatographic analysis of the rapeseed oil fatty acid methyl esters (biodiesel) at different reaction times. The biodiesel with best yield and quality was produced at methanol/oil molar ratio, 6:1; potassium hydroxide catalyst concentration, 1.0%; mixing intensity, 600 rpm and reaction temperature 65 °C. The yield of the biodiesel produced under optimal condition was 95-96%. It was noted that greater or lower the concentration of KOH or methanol than the optimal values, the reaction either did not fully occur or lead to soap formation.The quality of the biodiesel produced was evaluated by the determinations of important properties such as density, specific gravity, kinematic viscosity, higher heating value, acid value, flash point, pour point, cloud point, combustion point, cold filter plugging point, cetane index, ash content, sulphur content, water content, copper strip corrosion value, distillation temperature and fatty acid composition. The produced biodiesel was found to exhibit fuel properties within the limits prescribed by the latest American Standards for Testing Material (ASTM) and European EN standards.     

Branched‐Chain Fatty Acid Methyl Esters as Cold Flow Improvers for Biodiesel

Biodiesel is an alternative diesel fuel derived mainly from the transesterification of plant oils with methanol or ethanol. This fuel is generally made from commodity oils such as canola, palm or soybean and has a number of properties that make it compatible in compression‐ignition engines. Despite its many advantages, biodiesel has poor cold flow properties that may impact its deployment during cooler months in moderate temperature climates. This work is a study on the use of skeletally branched‐chain‐fatty acid methyl esters (BC‐FAME) as additives and diluents to decrease the cloud point (CP) and pour point (PP) of biodiesel. Two BC‐FAME, methyl iso‐oleate and methyl iso‐stearate isomers (Me iso‐C_18:1 and Me iso‐C_18:0), were tested in mixtures with fatty acid methyl esters (FAME) of canola, palm and soybean oil (CaME, PME and SME). Results showed that mixing linear FAME with up to 2 mass% BC‐FAME did not greatly affect CP, PP or kinematic viscosity (ν) relative to the unmixed biodiesel fuels. In contrast, higher concentrations of BC‐FAME, namely between 17 and 39 mass%, significantly improved CP and PP without raising ν in excess of limits in the biodiesel fuel standard specification ASTM D 6751. Furthermore, it is shown that biodiesel/Me iso‐C_18:0 mixtures matched or exceeded the performance of biodiesel/Me iso‐C_18:1 mixtures in terms of decreasing CP and PP under certain conditions. This was taken as evidence that additives or diluents with chemical structures based on long‐chain saturated chains may be more effective at reducing the cold flow properties of mixtures with biodiesel than structures based on long‐chain unsaturated chains.     

Evaluation of biodiesel obtained from cottonseed oil

Esters from vegetable oils have attracted a great deal of interest as substitutes for petrodiesel to reduce dependence on imported petroleum and provide a fuel with more benign environmental properties. In this work biodiesel was prepared from cottonseed oil by transesterification with methanol, using sodium hydroxide, potassium hydroxide, sodium methoxide and potassium methoxide as catalysts. A series of experiments were conducted in order to evaluate the effects of reaction variables such as methanol/oil molar ratio (3:1–15:1), catalyst concentration (0.25–1.50%), temperature (25–65 °C), and stirring intensity (180–600 rpm) to achieve the maximum yield and quality. The optimized variables of 6:1 methanol/oil molar ratio (mol/mol), 0.75% sodium methoxide concentration (wt.%), 65 °C reaction temperature, 600 rpm agitation speed and 90 min reaction time offered the maximum methyl ester yield (96.9%). The obtained fatty acid methyl esters (FAME) were analyzed by gas chromatography (GC) and ¹H NMR spectroscopy. The fuel properties of cottonseed oil methyl esters (COME), cetane number, kinematic viscosity, oxidative stability, lubricity, cloud point, pour point, cold filter plugging point, flash point, ash content, sulfur content, acid value, copper strip corrosion value, density, higher heating value, methanol content, free and bound glycerol were determined and are discussed in the light of biodiesel standards such as ASTM D6751 and EN 14214.     

Methyl Esters (Biodiesel) from and Fatty Acid Profile of Gliricidia sepium Seed Oil

Increasing the supply of biodiesel by defining and developing additional feedstocks is important to overcome the still limited amounts available of this alternative fuel. In this connection, the methyl esters of the seed oil of Gliricidia sepium were synthesized and the significant fuel‐related properties were determined. The fatty acid profile was also determined with saturated fatty acids comprising slightly more than 35 %, 16.5 % palmitic, 14.5 % stearic, as well as lesser amounts of even longer‐chain fatty acids. Linoleic acid is the most prominent acid at about 49 %. Corresponding to the high content of saturated fatty acid methyl esters, cold flow is the most problematic property as shown by a high cloud point of slightly >20 °C. Otherwise, the properties of G. sepium methyl esters are acceptable for biodiesel use when comparing them to specifications in biodiesel standards but the problematic cold flow properties would need to be observed. The ¹H‐ and ¹³C‐NMR spectra of G. sepium methyl esters are reported.     

Crystallization Behavior of Fatty Acid Methyl Esters

Biodiesel from most agricultural feedstocks has flow properties that are prone to startup and operability problems during cold weather. Biodiesel from soybean oil is generally a mixture of long-chain fatty acid alkyl esters composed of 0.15–0.20 mass fraction saturated esters (melting point [MP] ≫ 0 °C) mixed with unsaturated esters (MP < 0 °C). This work investigates the crystallization properties of two saturated fatty acid methyl esters (FAME) commonly found in biodiesel from soybean oil. Differential scanning calorimetry (DSC) heating and cooling scans of methyl palmitate (MeC16), methyl stearate (MeC18) and methyl oleate (MeC18:1) in pure form were analyzed. Crystallization behavior in ternary FAME mixtures was inferred by the application of thermodynamic models based on ideal solution and freezing-point depression theories. Activity coefficients for MeC16 and MeC18 in MeC18:1 solvent were determined by analyzing DSC cooling curves for binary FAME mixtures. Eutectic points were predicted by both models. Crystallization onset temperatures inferred from freezing point depression theory were more accurate than those for ideal solutions with respect to a direct DSC cooling curve analysis of corresponding ternary mixtures. This work shows that the crystallization onset temperature (cloud point) of biodiesel may be predicted by freezing-point depression theory if the activity coefficients of the component FAME are known. The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by USDA or ARS of any product or service to the exclusion of others that may be suitable.     

Optimization of transesterification for methyl ester production from chicken fat

In this study, low cost feedstock chicken fat was used to produce methyl ester. After reducing the free fatty acid level of the chicken fat less than 1%, the transesterification reaction was completed with alkaline catalyst. Potassium hydroxide, sodium hydroxide, potassium methoxide and sodium methoxide were used as catalyst and methanol was used as alcohol for transesterification reactions. The effects of catalyst type, reaction temperature and reaction time on the fuel properties of methyl esters were investigated. The produced chicken fat methyl esters were characterized by determining their viscosity, density, pour point, flash point, acid value, methanol content, heat of combustion value, total-free glycerin, mono-di-tri glycerides, copper strip corrosion and ester yield values. The measured fuel properties of the chicken fat methyl ester met EN 14214 and ASTM D6751 biodiesel specifications when using potassium hydroxide and sodium hydroxide catalysts with high ester yield.     

Alkali catalyzed transesterification of safflower seed oil assisted by microwave irradiation

The safflower (Carthamus tinctorius L.) oil was extracted from the seeds of the safflower that grows in Diyarbakir, SE Anatolia of Turkey. Biodiesel has been prepared from safflower seed by transesterification of the crude oil under microwave irradiation, with methanol to oil molar ratio of 10:1, in the presence of 1.0% NaOH as catalyst. The conversion of C. tinctorius oil to methyl ester was over 98.4% at 6 min. The important fuel properties of safflower oil and its methyl ester (biodiesel) such as density, kinematic viscosity, flash point, iodine number, neutralization number, pour point, cloud point, cetane number are found out and compared to those of no. 2 petroleum diesel, ASTM and EN biodiesel standards. Compared with conventional heating methods, the process using microwaves irradiation proved to be a faster method for alcoholysis of triglycerides with methanol, leading to high yields of biodiesel.     

Flow properties of biodiesel fuel blends at low temperatures

The dynamic viscosities of biodiesel derived from ethyl esters of fish oil, no. 2 diesel fuel, and their blends were measured from 298 K down to their respective pour points. Blends of B80 (80 vol.% biodiesel–20 vol.% no. 2 diesel), B60, B40 and B20 were investigated. All the viscosity measurements were made with a Bohlin VOR Rheometer. Cloud point and pour point measurements were made according to ASTM standards. Arrhenius equations were used to predict the viscosities of the pure Biodiesel (B100), no. 2 diesel fuel (B0) and the biodiesel blends (B80, B60, B40, and B20) as a function of temperature. The predicted viscosities agreed well with measured values. An empirical equation for calculating the dynamic viscosity of these blends as a function of both temperature and blend has been developed. Furthermore, based on the kinematic viscosity and density measurements of B100 up to 573 K by Tate et al. [Tate RE, Watts KC, Allen CAW, Wilkie KI. The viscosities of three biodiesel fuels at temperatures up to 300 °C. Fuel 2006;85:1010–5; Tate RE, Watts KC, Allen CAW, Wilkie KI. The densties of three biodiesel fuels at temperatures up to 300 °C. Fuel 2006;85:1004–9] an empirical equation for predicting the dynamic viscosity of pure biodiesel for temperatures from 277 K to 573 K is given. Empirical equations for predicting the cloud and pour point for a given blend give values in good agreement with experiments. The dynamic viscosity of biodiesel and its blends increases as temperature decreases and show Newtonian behaviour down to the pour point. Dynamic viscosity, cloud point and pour point decreases with an increase in concentration of no. 2 diesel in the blend.     

Improving the low-temperature properties of alternative diesel fuels: Vegetable oil-derived methyl esters

This work explores near-term approaches for improving the low-temperature properties of triglyceride oil-derived fuels for direct-injection compression-ignition (diesel) engines. Methyl esters from transesterified soybean oil were evaluated as a neat fuel and in blends with petroleum middle distillates. Winterization showed that the cloud point (CP) of methyl soyate may be reduced to −16°C. Twelve cold-flow additives marketed for distillates were tested by standard petroleum methodologies, including CP, pour point (PP), kinematic viscosity, cold filter plugging point (CFPP), and low-temperature flow test (LTFT). Results showed that additive treatment significantly improves the PP of distillate/methyl ester blends; however, additives do not greatly affect CP or viscosity. Both CFPP and LTFT were nearly linear functions of CP, a result that compares well with earlier studies with untreated distillate/methyl ester blends. In particular, additives proved capable of reducing LTFT of neart methyl esters by 5–6°C. This work supports earlier research on the low-temperature properties; that is, approaches for improving the cold flow of methyl ester-based diesel fuels should continue to focus on reducing CP.     

The fatty acids of menhaden oil

Summary The methyl esters of menhaden oil have been separated into three fractions by low temperature crystallization; saturated esters, monoethylenic esters, and polyethylenic esters, the contents of the fractions being roughly 30.9, 15.1 and 54.0%, respectively. The saturated fraction was contaminated with about 5% of the ME esters. The ME fraction, in turn, contained small amounts of methyl myristate and PE esters; further, the recovery of ME esters by the procedure was incomplete. The saturated and ME fractions were separately distilled, and observations were made on the nature and amounts of the acids in the resulting fractions. The low temperature crystallization technic was shown to be useful in the separation of the complex mixtures of esters found in fish oils. Presented in partial fulfillment of the requirements for the degree of doctor of philosophy in the Graduate school.     

Biodiesel production from high FFA rubber seed oil

Currently, most of the biodiesel is produced from the refined/edible type oils using methanol and an alkaline catalyst. However, large amount of non-edible type oils and fats are available. The difficulty with alkaline-esterification of these oils is that they often contain large amounts of free fatty acids (FFA). These free fatty acids quickly react with the alkaline catalyst to produce soaps that inhibit the separation of the ester and glycerin. A two-step transesterification process is developed to convert the high FFA oils to its mono-esters. The first step, acid catalyzed esterification reduces the FFA content of the oil to less than 2%. The second step, alkaline catalyzed transesterification process converts the products of the first step to its mono-esters and glycerol. The major factors affect the conversion efficiency of the process such as molar ratio, amount of catalyst, reaction temperature and reaction duration is analyzed. The two-step esterification procedure converts rubber seed oil to its methyl esters. The viscosity of biodiesel oil is nearer to that of diesel and the calorific value is about 14% less than that of diesel. The important properties of biodiesel such as specific gravity, flash point, cloud point and pour point are found out and compared with that of diesel. This study supports the production of biodiesel from unrefined rubber seed oil as a viable alternative to the diesel fuel.