Improvement of Palm Oil Biodiesel Filterability by Adsorption Methods

Palm oil biodiesel (POB) is characterized by a very high cold soak filtration time (CSFT), which places the acceptability of this biofuel at risk. Therefore, the effect of four adsorbents, namely diatomaceous earth, natural silicate (NS), neutral bleaching earth (NBE), and acid activated bleaching earth (AABE), at two levels of addition (1 and 5 wt%) or two temperatures (25 and 110 °C) on the precipitate content and CSFT of POB was investigated. The impact on total glycerin content, moisture content, and oxidative stability was also examined. All treatments significantly decreased the precipitate content, total glycerin content, and moisture content, but only treatments with NS, NBE, and AABE at 5 wt% and 25 °C achieved acceptable filterability. The OSI value was also decreased; however, it remained above the ASTM limit. Operational conditions of treatment with AABE were further optimized in a two‐factor, five‐level center composite design. The combination of 0.65 wt% AABE and 10 min at 25 °C decreased CSFT to below the ASTM limit. Lower adsorbent concentrations could be effective down to 0.44 wt%, given a corresponding increase in the contact time up to 30 min.     

Implementing an In Situ Alkaline Transesterification Method for Canola Biodiesel Quality Screening

Increasing demand for canola (Brassica napus) as an edible oil crop and biodiesel (B100) feedstock has encouraged genetic development for increased oil yields and expanded acreage in the US Northern Plains. Crop production environment and plant genetics influence metabolism and fatty acid composition, but the influence of this interaction on the resulting fatty acid methyl esters (FAME) is not clearly understood. The objective of this study was to develop a canola in situ transesterification (TE) method for facilitating the identification of genetic, abiotic or biotic factors impacting B100 quality, and to evaluate FAME quality properties from conventional TE (degummed oil) and in situ TE methods. In situ reactions containing 40 g canola flour conducted for 6 h at 60 °C with a 275:1:1.05 M ratio of methanol:triacylglycerol (TAG):KOH provided 80% conversion of seed lipid to FAME. Replicated reactions provided sufficient FAME volume for measuring several ASTM D6751-09 standards including cloud point, kinematic viscosity, acid value, moisture content, oxidative stability, and total glycerin, but adjustments are necessary to provide sufficient volumes for routine analysis of cold soak filtration test. The established in situ protocol would permit weekly analysis of 40 samples and the in situ TE method provides an opportunity to evaluate the impact of genetic or environmental factors on B100 quality.     

Impact of the North Dakota Growing Location on Canola Biodiesel Quality

Canola biodiesel (fatty acid methyl esters, FAME) may have superior cold flow properties when compared to other biodiesel feedstocks, which is attributed to canola’s high unsaturated and low saturated fat content. The objective of this study was to evaluate canola biodiesel fatty acid composition, cloud point (CP) and oil stability index (OSI) among several ND locations and production years. In Experiment 1, bulked canola varieties from seven growing seasons (2003–2009) were analyzed and in Experiment 2 a single canola variety (Interstate Hyola 357RR) harvested at two locations (2003–2005, and 2007) were analyzed. FAME was produced directly from seed via in situ alkaline transesterification methods. CP ranged from −0.1 to −2.4 °C and was significantly impacted by year and location. FAME generally met the ASTM B100 specification for OSI (3 h), but increased seed storage decreased stability. No significant differences were detected in FAME composition, and iodine value ranged from 108 to 123 g I₂/100 g. A significant relationship between fat saturation and location with CP and stability was not detected among the samples in this study. Variation in fatty acid composition was small; thus, the significant variability in CP and OSI suggests either differences in minor constituents (antioxidants, waxes) or environmental seed stress impacted biodiesel quality. Our study supports the value of examining biodiesel quality in a canola breeding program.     

A Simple Standardization Method for the Biodiesel Cold Soak Filtration Apparatus

Commercially available refined vegetable oils were investigated as calibration standards for the filtration device and protocol specified by ASTM D7501 for conducting the biodiesel cold soak filtration test. Filtration time was determined to be a function of the amount of vacuum applied during filtration, with an 8 % change in the filtration time of soybean oil occurring across the vacuum range specified by ASTM D7501. At a constant vacuum of 57 cm Hg the mean filtration time of 150 mL of soybean oil was independent of operator, device, and oil lot number. Mean filtration time was also largely independent of brand: the average of the mean filtration times of replicate samples of seven brands of soybean oil was 396 s with a minimum significant difference (MSD) of 28 s, and the filtration times of seven of eight brands of soybean oil tested fell within this MSD. Refined edible‐grade corn, canola, peanut, safflower and sunflower oils gave reliable filtration times and would be suitable standards. Each oil exhibited a characteristic filtration time, all greater than that for soy oil. Filtration times were an approximately linear function of kinematic viscosities, as predicted by Darcy's Law. Edible vegetable oils can serve as reliable, affordable, consistent and generally available materials for confirming the operability of the filtration device used in the biodiesel cold soak filtration test.     

A Quantitative Method of Analysis for Sterol Glycosides in Biodiesel and FAME Using GC-FID

Sterol glycosides (SG) are known to cause filter blocking problems in biodiesel use. The extraction and quantitative analysis of SG is difficult due to its low problematic concentration and its compatibility with biodiesel. The purpose of this study is to develop a method to quantify SG in FAME and biodiesel using gas chromatography and other equipment found in laboratories performing routine biodiesel analyses. SG was isolated from FAME using n‐dodecane, acidification and cold soaking, followed by cold centrifugation at ?8 to ?15 °C. The solids obtained were further separated by phase partition with a Folch wash, followed by a final n‐dodecane rinse. This solution was analyzed by GC‐FID using the operating conditions outlined in ASTM D6584. A calibration curve for SG was produced and a first order fit gave a value of r² = 0.992. Reproducibility tests were performed on soybean FAME and B100 canola biodiesel samples spiked with SG. The recovery of SG by the new method was found to be 99 % for soy FAME with a standard deviation of 0.7 and 100 % for B100 canola with a standard deviation of 3.5 %. The reproducibility based on two standard deviations of the predicted concentration for all 12 spiked samples studied in this work was 2.4 ppm.     

Evaluation of Biodiesel Derived from <Emphasis Type="Italic">Camelina sativa</Emphasis> Oil

Biodiesel derived from camelina as well as other feedstocks including palm, mustard, coconut, sunflower, soybean and canola were prepared via the conventional base-catalyzed transesterification with methanol. Fatty acid profiles and the fuel properties of biodiesel from different vegetable oils were analyzed and tested in accordance with ASTM D6751. Camelina biodiesel contains 10–12%, 37–40%, and 48–50% saturated, monounsaturated and polyunsaturated components, respectively. Some fuel properties of camelina biodiesel are comparable to that of sunflower biodiesel including kinematic viscosity (40 °C), flash point, cloud point, cold filter plugging point, and oil stability index. However, camelina biodiesel exhibited the poorest oxidative stability, highest distillation temperature and has the highest potential to form coke during combustion, all of which are attributed to the high amounts of n-3-fatty acids in camelina oil. While neat camelina biodiesel may exhibit undesirable fuel properties, it is very comparable with soybean biodiesel at the B20 level.     

Quality analysis of wintertime B6-B20 biodiesel blend samples collected in the United States

A survey of the quality of biodiesel blends in the United States was conducted in the winter of 2009-2010. Forty samples were collected in the study; two-thirds of the samples collected were from areas with a 10th percentile minimum ambient temperature below − 12 °C. Fuel properties were measured and compared to the relevant ASTM D7467-09 specification properties. The B6-B20 study shows increased compliance with the blend level requirements to 72.5% of samples tested, with a cold state average biodiesel content of 12% and a warm state average biodiesel content of 19%. The decreased biodiesel content in cold states is likely to due to deliberate reductions to meet the cloud point expectations. Continuing problems were noted with induction period stability for B6-B20 blends, with a failure rate of 24%. Samples collected from cold weather states had a failure rate of only 18%, likely because of the reduced biodiesel content; the failure rate from warm weather states rose to 57%. Samples failed the induction period stability specification before the acid value increased to the point of failure and no acid value failures were recorded. No failures were observed water and sediment. A single failure was noted for flash point, likely due to external contamination during fuel handling. Cloud point and cold filter plugging points are reported.     

Determination of Acid Number of Biodiesel and Biodiesel Blends

Due to an increase in the commercial use of biodiesel and biodiesel blends, both ASTM D 6751 and EN 14214 include the acid number (AN) as an important quality parameter. It was found that determination of AN of biodiesel and biodiesel blends using the ASTM D 974 results in large values of repeatability (up to 73.41%) and larger percentage error (up to 42.88%). Therefore, ASTM D 974 has been modified using a lower concentration of base (0.02 M KOH instead of 0.1 M KOH) as well as reducing the amount of toxic titration solvent from 100 mL to only 10 mL. This makes the modified ASTM D 974 as a green analytical method which uses a reduced amount of toxic solvent. This modified method significantly reduced the maximum percentage error from 42.88 to 5.92%. The application of this modified ASTM D 974 for the determination of AN of biodiesel and biodiesel blends was studied. The accuracy of this modified ASTM D 974 for biodiesel (B100) was measured to be within 3.51% over the AN range of 0.313–0.525 mg KOH/g and maximum repeatability was decreased from 8.37 to 2.75% within this AN range which is far below the ASTM D 974 stated repeatability specifications. For B20, B10, B5, B2, and B1, the most accurate values were measured at AN values of 0.177, 0.067, 0.072, 0.126, and 0.096 mg KOH/g, respectively. Excellent linearity values of R ² for calculated and experimentally determined AN were obtained. The difference between the experimental and the calculated AN for all biodiesel and biodiesel blend samples was within ± 0.018 mg KOH/g. This extensive study has demonstrated that this modified ASTM D 974 is a reliable method for the determination of AN and could be used for establishing the specifications of AN for biodiesel and biodiesel blends ranging from B1 to B20 in quality standards.     

Comparing Process Efficiency in Reducing Steryl Glucosides in Biodiesel

A significant obstacle to the commercial acceptance of biodiesel is the potential for filter plugging due to precipitates in the fuel. The majority of these precipitates can be attributed to either steryl glucosides (SGs) or monoacylglycerols in biodiesel. A GC–FID method to quantify minor components content in biodiesel is presented. The effectiveness of room temperature and cold soak filtration, adsorbent treatment, centrifuge, and vacuum distillation processes for SG removal was studied. The vacuum distillation process is the most effective method of removing the SG from biodiesel.     

Optimization of biodiesel production from edible and non-edible vegetable oils

The non-edible vegetable oils such as Jatropha curcas and Pongamia glabra (karanja) and edible oils such as corn and canola were found to be good viable sources for producing biodiesel. Biodiesel production from different edible and non-edible vegetable oils was compared in order to optimize the biodiesel production process. The analysis of different oil properties, fuel properties and process parameter optimization of non-edible and edible vegetable oils were investigated in detail. A two-step and single-step transesterification process was used to produce biodiesel from high free fatty acid (FFA) non-edible oils and edible vegetable oils, respectively. This process gives yields of about 90-95% for J. curcas, 80-85% for P. glabra, 80-95% for canola, and 85-96% for corn using potassium hydroxide (KOH) as a catalyst. The fuel properties of biodiesel produced were compared with ASTM standards for biodiesel.     

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.     

Formation of Insolubles in Palm Oil-, Yellow Grease-, and Soybean Oil-Based Biodiesel Blends After Cold Soaking at 4 °C

The insolubles formed in biodiesel blends can cause operation problems because they can plug the fuel lines and filters. The formation of insolubles in soybean oil (SBO-), yellow grease (YG-), and palm oil (PO-) based biodiesel blends after cold soaking at 4 °C was investigated. PO-based biodiesel blends displayed a much higher time to filter (TTF) and greater insoluble mass, compared to SBO-, and YG-based biodiesel blends. Fourier transform infrared (FTIR) spectra and gas chromatography-flame ionization detector (GC-FID) chromatograms indicated that PO-based biodiesel insolubles can be attributed to monoglycerides, while SBO-based biodiesel insolubles are due to steryl glucosides (SG). A simple analytical method for identification of SG in biodiesel samples was established by GC-FID.     

Comparisons of Biodiesel Produced from Unrefined Oils of Different Peanut Cultivars

Biodiesels were prepared according to standard procedures from unrefined oils of eight commercially available peanut cultivars and compared for differences in physical properties important to fuel performance. Dynamic viscosity, kinematic viscosity and density were measured from 100 to 15 °C, and differences (p < 0.05) in these physical properties occurred more frequently at lower temperatures when comparing the different cultivars. Unlike data for the oil feedstocks, no meaningful correlations among biodiesel fatty acid profiles and either fuel viscosity or density were observed. Low temperature crystallization of the peanut biodiesels was measured via differential scanning calorimetry. Increased concentrations of long chain saturated fatty acid methyl esters (FAME) were associated with an increased propensity for low temperature crystallization, and the single FAME category most associated with low temperature crystallization was C:24. Tempering at 10 °C followed by analysis of the soluble fractions (winterization), improved crystallization properties and confirmed the importance that long chain saturated FAMEs play in the final functionality of peanut biodiesel. Peanut data is also compared to data for canola and soy biodiesels, as these feedstocks are more common worldwide for biodiesel production. Overall, this work suggests that minimizing the concentration of long chain saturated FAMEs within peanut biodiesel, either through processing and/or breeding efforts would improve the low temperature performance of peanut biodiesel.     

Roselle (Hibiscus sabdariffa L.) oil as an alternative feedstock for biodiesel production in Thailand

The production of biodiesel fuel from crude roselle oil was evaluated in this study. The process of alkali-catalyzed transesterification with methanol was carried out to examine the effects of reaction variables on the formation of methyl ester: variables which included methanol-to-oil molar ratios of 4:1-10:1, catalyst concentrations of 0.25-2.0% w/w of oil, reaction temperatures of 32-60 °C, and reaction times of 5-80 min. The methyl ester content from each reaction condition was analyzed by gas chromatography (GC), the optimum condition having been achieved at a methanol-to-oil molar ratio of 8:1, a catalyst concentration of 1.5% w/w of oil, a reaction temperature of 60 °C, and a reaction time of 60 min. The resultant methyl ester content of 99.4% w/w, plus all of the other measured properties of the roselle biodiesel, met the Thai biodiesel (B100) specifications and international standards EN 14214:2008 (E) and ASTM D 6751-07b, with the exception of a higher carbon residue and lower oxidation stability.     

Biodiesel production from mixtures of canola oil and used cooking oil

Used cooking oil (UCO) was mixed with canola oil at various ratios in order to make use of used cooking oil for production of biodiesel and also lower the cost of biodiesel production. Methyl and ethyl esters were prepared by means of KOH-catalyzed transesterification from the mixtures of both the oils. Water content, acid value and viscosity of most esters met ASTM standard except for ethyl esters prepared from used cooking oil. Canola oil content of at least 60% in the used cooking oil/canola oil feedstock is required in order to produce ethyl ester satisfying ASTM specifications. Although ethanolysis was proved to be more challenging, ethyl esters showed reduced crystallization temperature (−45.0 to −54.4 °C) as compared to methyl esters (−35.3 to −43.0 °C). A somewhat better low-temperature property of ester was observed at higher used cooking oil to canola oil ratio in spite of similar fatty acid compositions of both oils.     

Development and Scale-up of Aqueous Surfactant-Assisted Extraction of Canola Oil for Use as Biodiesel Feedstock

Aqueous surfactant-assisted extraction (ASE) has been proposed as an alternative to n-hexane for extraction of vegetable oil; however, the use of inexpensive surfactants such as sodium dodecyl sulfate (SDS) and the effect of ASE on the quality of biodiesel from the oil are not well understood. Therefore, the effects on total oil extraction efficiency of surfactant concentration, extraction time, oilseed to liquid ratio and other parameters were evaluated using ASE with ground canola and SDS in aqueous solution. The highest total oil extraction efficiency was 80 %, and was achieved using 0.02 M SDS at 20 °C, solid–liquid ratio 1:10 (g:mL), 1,000 rpm stirring speed and 45 min contact time. Applying triple extraction with three stages reduced the amount of SDS solution needed by 50 %. The ASE method was scaled up to extract 300 g of ground canola using the best combination of extraction conditions as described above. The extracted oil from the scale-up of the ASE method passed the recommendation for biodiesel feedstock quality with respect to water content, acid value and phosphorous content. Water content, kinematic viscosity, acid value and oxidative stability index of ASE biodiesel were within the ASTM D6751 biodiesel standards.     

Utilization of green seed canola oil for biodiesel production

Increasing percentage of green canola seed every year is a serious problem for canola growers. Chlorophyll content of this oil is very high, which makes it more susceptible to photo‐oxidation and ultimately the oxidation stability of the oil is very reduced. Hence green seed canola oil is underutilized for edible purposes. The present work is an attempt to produce high‐quality biodiesel from green seed canola oil and methanol, ethanol and various mixtures of methanol and ethanol using KOH as a catalyst. A mixture of alcohols improved the rate of reaction. After transesterification of green seed canola oil using KOH, the chlorophyll content of the oil was decreased substantially (from 22.1 ppm to 10.3 ppm). Characteristics of the esters prepared from green seed canola oil were well within the limits of ASTM standards. Lubricity of the green seed oil esters was excellent (20% decrease in wear scar area) when added at 1 vol% to the base fuel. Oxidation stability is crucial for long‐term storage of the fuel. Oxidation stability index (OSI) of green seed esters was 4.9 h at 110 °C, which is much less than the European Standard (6 h at 100 °C). The low oxidation stability of green seed esters is attributed to its higher chlorophyll (10.3 ppm) content. An attempt was also made to reduce the chlorophyll content of the oil before transesterification using activated carbon treatment, and it was observed that chlorophyll content was reduced from 22.1 to 2.2 ppm. Copyright © 2006 Society of Chemical Industry     

Total Acid Number Determination of Biodiesel and Biodiesel Blends

The repeatability and accuracy of the total acid number (TAN) measurement for soy oil-based biodiesel–diesel blends using the ASTM D664 method was studied. ASTM D664 is the standard reference method for measuring the acid number of both biodiesel and petroleum-derived diesel, which specifies procedures for the determination of acidic components in biodiesel and diesel, and claims good repeatability and mediocre reproducibility during application, but cites no information on accuracy. However, the accuracy of this method is very important for setting the specifications for biodiesel blends, especially for B20 (a mixture composed of 20% biodiesel with 80% diesel) because of its wide commercial production. The accuracy of ASTM D664 was measured to be within 4.13% for B20 in the acid number range of 0.123–0.332 mg KOH/g. The maximum repeatability was approximately 5.21% at an acid number of 0.123 mg KOH/g. Within the ASTM D6751-07b specification for TAN (0.5 mg KOH/g), good accuracy and repeatability were also obtained. Accuracy specification and electrode operation suggestions for ASTM D664 are also given.     

Oxidative stability of soybean oils with altered fatty acid compositions

The oxidative stabilities of one canola oil and six soybean oils of various fatty acid compositions were compared in terms of peroxide values, conjugated dienoic acid values and sensory evaluations. Two of the soybean oils (Hardin and BSR 101) were from common commercial varieties. The other four soybean oils were from experimental lines developed in a mutation breeding program at Iowa State University that included A17 with 1.5% linolenate and 15.2% palmitate; A16 with 2% linolenate and 10.8% palmitate; A87-191039 with 2% linolenate and 29.6% oleate; and A6 with 27.5% stearate. Seed from the soybean genotypes was cold pressed. Crude canola oil was obtained without additives. All oils were refined, bleached and deodorized under laboratory conditions with no additives and stored at 60°C for 15 days. The A17, A16, A87-191039 and A6 oils were generally more stable to oxidation than the commercial soybean varieties and canola oil as evaluated by chemical and sensory tests. Canola oil was much less stable than Hardin and BSR 101 oils by both chemical and sensory tests. The peroxide values and flavor scores of oils were highly correlated with the initial amounts of linolenate (r=0.95, P=0.001). Flavor quality and flavor intensity had negative correlations with linolenate, (r=−0.89, P=0.007) and (r=−0.86, P=0.013), respectively.     

Effects of partial hydrogenation, epoxidation, and hydroxylation on the fuel properties of fatty acid methyl esters

The properties of biodiesel depend on the chemical structure of individual fatty acid methyl esters (FAME). In this work the chemical structure of fatty acid chains was modified by catalytic hydrogenation, epoxidation and hydroxylation under controlled conditions. Hydrolysis of ester functionality or oxidation of fatty acid chain was not observed during these reactions. The properties of hydrogenated FAME strongly depend on the hydrogenation time. The total saturated fatty acid (SFA) percentage increased from 29.3% to 76.2% after 2 h of hydrogenation. This hydrogenated FAME showed higher oxidation stability and higher cetane number but poor cold flow properties. Formation of trans FAME was observed during hydrogenation. Both hydroxylation and epoxidation resulted in a decrease of unsaturated fatty acid methyl ester (UFA) fraction. The percentages of total unsaturated FAME decreased 39% in the epoxidation reaction and 44% in the hydroxylation reaction. The addition of hydroxyl groups to the unsaturated regions of the fatty acid chain yields biodiesel with better cold flow properties, increased lubricity and slightly increased oxidative stability. However, epoxy FAME shows some interesting properties such as higher oxidation stability, higher cetane number and acceptable cold flow properties, which met the limits of ASTM D6751 biodiesel specifications.