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Biodiesel Production Publicaitons

This page lists all biodiesel production journal publications from University of Idaho. Please provide us a feedback feedback if you see any error in this listing or you would like to report and articles that should have been in this section. Your help will make this a great place to find articles about biodiesel feedstock.

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  1. Characterization of Microalgae for the Purpose of Biofuel Production
    Abstract

    Bi, Z.; He, B. B. 2013. Characterization of Microalgae for the Purpose of Biofuel Production. Transactions of the Asabe. 56(4) 1529-1539

    It is now widely accepted that microalgae are promising candidate feedstocks for biofuel production, especially for biodiesel. Microalgae consist of a vast number of species that contain complex chemical constituents and physical structures. The purpose of this study is to understand the physical and chemical properties of selected microalgae, which is critical to the design of appropriate processes for commercial biofuel production. ASTM standard methods were implemented to examine the microalgae properties, including proximate and ultimate analyses. Among the microalgae studied, green microalgae have more volatile matter than brown microalgae, while the latter contain much higher ash content (as high as 43.4%wt +/- 0.20%wt dry basis). The lowest ash content was found in the samples of green microalgae (14.3%wt +/- 0.10%wt dry basis). Ultimate analysis showed that brown microalgae have less carbon content (approx. 25%wt dry basis) as compared to green microalgae (49%wt to 58%wt dry basis). All samples of microalgae were high in sulfur content (0.4%wt to 1.0%wt dry basis). Mineral contents of all microalgal samples were similar to those commonly present in other biomass. Brown microalgae contain significantly higher amounts of carbohydrates (72.9%wt to 75.5%wt dry basis) than green microalgae. On the other hand, green microalgae contain more crude fat (17.1%wt to 27.8%wt dry basis) than brown microalgae. The fatty acid profiles show that the primary fatty acids in microalgal lipids are similar to those of vegetable oils such as soybean oil. However, there are also many odd-numbered fatty acids, such as C15:0, C17:0, and C19:0, which are not typically seen in other seed oils.
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  2. Biodiesel production via acid catalysis
    Abstract

    Canakci, M.; Van Gerpen, J. 1999. Biodiesel production via acid catalysis. Transactions of the ASAE. 42(5) 1203-1210

    Vegetable oils and animal fats can be transesterified to biodiesel for use as an alternative diesel fuel. Conversion of low cost feedstocks such as used frying oils is complicated if the oils contain large amounts of free fatty acids that will form soaps with alkaline catalysts. The soaps can prevent separation of the biodiesel from the glycerin fraction. Alternative processes are available that use an acid catalyst The objective of this study was to investigate the effect of process variables on acid-catalyzed transesterification. The molar ratio of alcohol, reaction temperature, catalyst amount, reaction time, water content, and free fatty acids were investigated to determine the best strategy for producing biodiesel. Food grade soybean oil was used to prepare esters using excess methanol and sulfuric acid as a catalyst. To compare the effect of different alcohol types on ester formation, methanol, ethanol, 2-propanol, and n-butanol were compared. The American Oil Chemists' Society Method Ca 14-56 was used to measure the biodiesel's total glycerin amount as an indicator of the completeness of the reaction. It was found that acid catalysis can provide high conversion rates but much longer times are required than for alkaline catalysts. The acid catalyst also requires the concentration of water to be less than 0.5%, which is about the same as is required for alkaline catalysts. Water formed by the esterification of free fatty acids limited their presence in the oil to 5%
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  3. Biodiesel production from oils and fats with high free fatty acids
    Abstract

    Canakci, M.; Van Gerpen, J. 2001. Biodiesel production from oils and fats with high free fatty acids. Transactions of the ASAE. 44(6) 1429-1436

    Biodiesel is an alternative fuel for diesel engines consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Most of the biodiesel that is currently made uses soybean oil, methanol, and an alkaline catalyst. The high value of soybean oil as a food product makes production of a cost-effective fuel very challenging. However there are large amounts of low-cost oils and fats such as restaurant waste and animal fats that could be converted to biodiesel. The problem with processing these low cost oils and fats is that they often contain large amounts of free fatty acids (FFA) that cannot be converted to biodiesel using an alkaline catalyst. In this study, a technique is described to reduce the free fatty acids content of these feedstocks using an acid-catalyzed pretreatment to esterify the free fatty acids before transesterifying the triglycerides with an alkaline catalyst to complete the reaction. Initial process development was performed with synthetic mixtures containing 20% and 40% free fatty acids, prepared using palmitic acid. Process parameters such as the molar ratio of alcohol, type of alcohol, acid catalyst amount, reaction time, and free fatty acids level were investigated to determine the best strategy for converting the free fatty acids to usable esters. The work showed that the acid level of the high free fatty acids feedstocks could be reduced to less than 1% with a 2-step pretreatment reaction. The reaction mixture was allowed to settle between steps so that the water-containing alcohol phase could be removed. The 2-step pretreatment reaction was demonstrated with actual feedstocks, including yellow grease with 12% free fatty acids and brown grease with 33% free fatty acids. After reducing the acid levels of these feedstocks to less than 1%, the transesterification reaction was completed with an alkaline catalyst to produce fuel-grade biodiesel
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  4. A pilot plant to produce biodiesel from high free fatty acid feedstocks
    Abstract

    Canakci, M.; Van Gerpen, J. 2003. A pilot plant to produce biodiesel from high free fatty acid feedstocks. Transactions of the ASAE. 46(4) 945-954

    Biodiesel is an alternative diesel fuel consisting of the alkyl monoesters of fatty acids from vegetable oils or animal fats. Currently, most biodiesel is made from soybean oil, methanol, and an alkaline catalyst. However, there are large amounts of fats and oils that are unsuitable for human consumption that could be converted to biodiesel at lower cost. The problem with processing these waste oils is that they often contain large amounts of free fatty acids that cannot be converted to biodiesel using an alkaline catalyst. These free fatty acids react with the alkaline catalyst to produce soaps that inhibit the separation of the biodiesel, glycerin, and wash water. Previous research has developed a process for pretreating these high free fatty acid feedstocks using acid catalysts, which do not form soaps. The objective of this study was to construct a pilot plant to produce biodiesel from a wide variety of feedstocks including those with high free fatty acids. A 190 L batch pilot plant has been built that can process high free fatty acid feedstocks using an acid-catalyzed pretreatment followed by an alkaline-catalyzed transesterification. Case studies of pilot plant-scale production of biodiesel from soybean oil, yellow grease with 9% free fatty acids, and brown grease with 40% free fatty acids are presented. The effect of varying the reaction parameters is discussed, and the separation and washing processes are described. Estimates of the fuel cost using different feedstocks are also provided
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  5. Experimental optimization of a continuous-flow reactive distillation reactor for biodiesel production
    Abstract

    He, B. B.; Singh, A. P.; Thompson, J. C. 2005. Experimental optimization of a continuous-flow reactive distillation reactor for biodiesel production. Transactions of the Asae. 48(6) 2237-2243

    A comprehensive study of biodiesel preparation from canola oil was performed on a continuous-flow reactive distillation (RD) reactor system. Optimization of six process variables was studied experimentally and analyzed statistically on the overall performance of the RD reactor system. These variables include the feed methanol to triglycerides molar ratio, reaction time, reboiler temperature, catalyst concentration, methanol circulation mode, and catalyst formulation. An experimental design was used in the experiments, and statistical multiple response regression models were employed for process optimization. Under the operating conditions explored, product yields ranged from 41.5% to 94.9%, productivity ranged from 16 to 55.8 kmol/m(3.)h (5.6 to 19.5 m(3/)m(3.)h), and soap formation varied from 4.44 to 29.1 mol/100 mol (0.19 to 1.27%wt.). For different optimization criteria, the following optimum variable ranges were found: feed molar ratio from 3.65:1 to 4.50:1, reaction time from 3.76 to 5.56 min, reboiler temperature from 100 degrees C to 130 degrees C, and catalyst concentration from 0.13 to 0.24 mol/mol. Although the process variables individually affected the system performance to a certain extent, the interactive effect of the process variable combinations affected the system efficiency more significantly. When maximized, the product yields and productivity were 98.8% and 55.6 kmol/m(3.)h (18.5 m(3)/m(3.)h), respectively. However when soap formation was minimized, the yield and productivity were 72% and 9.3 kmol/m(3.)h (3.1 m(3)/m(3.)h), respectively. It is recommended that the optimization of the RD reactor system be based on the maximization of product yield and reactor productivity.
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  6. A novel continuous-flow reactor using reactive distillation for biodiesel production
    Abstract

    He, B. B.; Singh, A. P.; Thompson, J. C. 2006. A novel continuous-flow reactor using reactive distillation for biodiesel production. Transactions of the Asabe. 49(1) 107-112

    The production of biodiesel through batch and existing continuous flow processes requires the use of a much higher excess alcohol, typically 100%, than the stoichiometric molar requirement in order to drive the transesterification reaction to completion. This excess alcohol must be recovered in a separate process, which involves additional capital and operating costs. In this study, a novel reactor system using reactive distillation (RD) was developed and investigated for biodiesel preparation from canola oil and methanol. The goal was to significantly reduce the use of excess methanol while maintaining a high methanol: glyceride molar ratio inside the RD reactor by recycling a small amount of methanol within the system. Reactant conversion rate and product yield were used as the criteria for the reactor evaluation. The effect of the methanol: glyceride ratio was studied on a laboratory-scale perforated-tray RD reactor system. Product parameters such as methyl ester content, glycerides, and methanol content were analyzed. Preliminary results showed that the RD reactor with a methanol: glyceride ratio of 4:1 (molar), in which the use of methanol was cut down by 66%, gave a satisfactory biodiesel yield and oil conversion rate at a column temperature of 65 degrees C. Total reaction time in the pre-reactor and RD column was about 3 min, which is 20 to 30 times shorter than in typical batch processes. The productivity of the RD reactor system was about 6.6 m(3) biodiesel per m(3) reactor volume per hour, which is 6 to 10 times higher than that of batch and existing continuous flow processes.
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  7. Function and performance of a pre-reactor to a reactive distillation column for biodiesel production
    Abstract

    He, B. B.; Singh, A. P.; Thompson, J. C. 2007. Function and performance of a pre-reactor to a reactive distillation column for biodiesel production. Transactions of the Asabe. 50(1) 123-128

    This article describes an in-depth follow-up to previous studies showing that an oil-methanol mixer prior to an RD reactor played an important role in enhancing the overall performance of the RD reactor system. An in-line static mixer was used for the purpose of providing initial mixing of the reactants, heating the mixture up to the desired operating temperature, and carrying out a substantial part of the transesterification reaction in the early stage. It performed three functions: a reactant mixer, a heat exchanger, and a pre-reactor. This article reports the systematic investigations of the pre-reactor performance by examining the effects of process variables on the process evaluating parameters, and the operating conditions for optimum operation. A wide range of results was observed under different operating conditions. The product yield was as high as 84.60% and as low as 1.63%. The soap formation was in the range of 2.80% to 10.37%. The feed molar ratio, reaction time, and catalyst concentration all contributed positively to the product yield and soap formation. Although an optimum condition produced a product yield of 80.46% and soap formation of 5.18% with a 1.33 min reaction time, the optimization should be based on the integration of the whole RD reactor system rather than a collection of individually optimized components. This study of the pre-reactor serves as an analysis tool for part of the RD reactor system.
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  8. Catalytic Thermochemical Conversion of Glycerol to Simple and Polyhydric Alcohols Using Raney Nickel Catalyst
    Abstract

    Maglinao, R. L.; He, B. B. 2011. Catalytic Thermochemical Conversion of Glycerol to Simple and Polyhydric Alcohols Using Raney Nickel Catalyst. Industrial & Engineering Chemistry Research. 50(10) 6028-6033

    The crude glycerol from biodiesel production possesses low economic values and alternative ways of converting it to valuable chemicals are needed to sustain the biodiesel industry. This study aimed to investigate the production of primary alcohols and propylene glycol from glycerol through a catalytic thermochemical process without an external supply of hydrogen. The effects of reaction time, water to glycerol ratio, and doses of catalyst on glycerol conversion and alcohol yields were investigated using a batch pressure reactor and Raney nickel catalyst. The presence of alcohols and gases in the products confirmed that hydrogen was produced and was utilized in the formation of propylene glycol through hydrogenolysis. Ethanol and propylene glycol yields of up to 10.4 +/- 0.2 and 33.2 +/- 1.4 mol %, respectively, were observed. It was also concluded that ethanol is formed through hydrogenolysis of propylene glycol and its yield improves at extended reaction time and increased initial water content of the feed.
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  9. Investigation of biodiesel thermal stability under simulated in-use conditions
    Abstract

    Monyem, A.; Canakci, M.; Van Gerpen, J. H. 2000. Investigation of biodiesel thermal stability under simulated in-use conditions. Applied Engineering in Agriculture. 16(4) 373-378

    Biodiesel is an alternative diesel fuel produced by transesterification of vegetable oils or animal fats. While biodiesel products numerous environmental benefits such as reduced exhaust emissions, it is more prone to oxidation than petroleum-based diesel fuel and this can alter its properties. When oxidation occurs at ordinary temperatures, the initial products are hydroperoxides. As the oxidation continues, the peroxides may split and form aldehydes, ketones, and short chain acids that produce unpleasant odors. Sediment and gums are formed through polymerization of the peroxides and can cause fuel filter plugging. The objective of this study was to relate the chemical and physical processes associated with biodiesel oxidation to the conditions that affect diesel fuel system performance. A relationship was sought between the test that is used by the engine industry to define engine fuel stability requirements (ASTM D2274) and the tests used by the fats and oils industry to characterize oxidation (Peroxide Value and Acid Value). It was found during the course of this study that the ASTM fuel stability method is not suitable for biodiesel. While oxidation causes the fuel viscosity to increase, fuel filter plugging was not necessarily a natural consequence of biodiesel oxidation even when the fuel was oxidized to a level beyond what would be observed in practice. The effect of fuel temperature and blending with diesel fuel on the oxidation was investigated and the interrelationship between the fuel's acid value and viscosity is shown.
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  10. Experiments with vegetable oil expression
    Abstract

    Peterson, C. L.; Auld, D. L.; Thompson, J. C. 1983. Experiments with vegetable oil expression. Transactions of the ASAE. 26(5) 1298-1302

    University of Idaho seed processing research in centered about a CeCoCo oil expeller. A seed preheater-auger, seed bin, meal auger, and oil pump have been constructed to complete the system, which is automated and instrumented. Extracted oil weight, meal weight, process temperature, and input energy are all recorded during operation. The oil is transferred to tanks where it settles for 48 h or more. It is then pumped through a filtering system and stored ready to be used as an engine fuel. The equipment has processed over 11,000 kg of seed with an average extraction efficiency of 78% . Winter rape, safflower, and sunflower have been the principle crops used in the study.
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  11. Continuous flow biodiesel production
    Abstract

    Peterson, C. L.; Cook, J. L.; Thompson, J. C.; Taberski, J. S. 2002. Continuous flow biodiesel production. Applied Engineering in Agriculture. 18(1) 5-11

    Biodiesel, which consists of the fatty acid esters of simple alcohols, is a potential replacement for a portion of the diesel fuel used in transportation. It is produced from both used (oil that has been utilized for frying and discarded) and new vegetable and animal fats and oils. It has several advantages. Among these advantages are its classification as a renewable resource, its ability to reduce HC, CO, and CO2 exhaust emissions, its non-toxic character, and its biodegradability. One of the keys to making biodiesel a viable and profitable energy source is the use of a continuous flow transesterification process to reduce time and cost, thereby increasing production and profit. A continuous flow esterification process for producing biodiesel from rapeseed oil and ethanol was investigated. The equipment consisted of an oil metering pump, centrifugal mixing pump, ethanol and catalyst metering pump, static mixers, "ladder" type retention reactor, water injection system, and continuous flow centrifugal separating system. The oil feed rate was 0.38 L/min that yields about three times the weekly production of the existing batch type transesterification system that produces 945 L (250 gal) per batch. It was anticipated that if methanol were used instead of ethanol that the flow, rate could be considerably increased. The system in its present configuration has met ASTM PS121-99 standard for free and total glycerol. The centrifugal separation resulted in release of excessive alcohol vapors. A vapor recovery and condensing system should be installed. This latter system could help further reduce costs of the biodiesel produced by recycling some of the alcohol used
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  12. Processing, characterization, and performance of eight fuels from lipids
    Abstract

    Peterson, C. L.; Reece, D. L.; Hammond, B. L.; Thompson, J. C.; Beck, Sidney M. 1997. Processing, characterization, and performance of eight fuels from lipids. Applied Engineering in Agriculture. 13(1) 71-79

    Test quantities of ethyl and methyl esters of four renewable fuels were processed, characterized and performance tested. Canola, rapeseed, soybean oils, and beef tallow were the feedstocks for the methyl and ethyl esters. A complete set of fuel properties and a comparison of each fuel in engine performance tests are reported. The study examines short term engine tests with both methyl and ethyl ester fuels compared to number 2 diesel fuel (D2). Three engine performance tests were conducted including an engine mapping procedure, an injector coking screening test, and an engine power study. The gross heat contents of the biodiesel fuels, on a mass basis, were 9 to 13% lower than D2. The viscosities of biodiesel were twice that of diesel. The cloud and pour points of D2 were significantly lower than the biodiesel fuels. The biodiesel fuels produced slightly lower power and torque and higher fuel consumption than D2. In general, the physical and chemical properties and the performance of ethyl esters were comparable to those of the methyl esters. Ethyl and methyl esters have almost the same energy. The viscosity of the ethyl esters is slightly higher and the cloud and pour points are slightly lower than those of methyl esters. Engine tests demonstrated that methyl esters produced slightly higher power and torque than ethyl esters. Fuel consumption when using the methyl and ethyl esters is nearly identical. Some desirable attributes of the ethyl esters over methyl esters were: significantly lower smoke opacity, lower exhaust temperatures, and lower pour point. The ethyl esters tended to have more injector coking than the methyl esters, and the ethyl esters had a higher glycerol content than the methyl esters
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  13. Process optimization of biodiesel production using alkaline catalysts
    Abstract

    Singh, A.; He, B.; Thompson, J.; Van Gerpen, J. 2006. Process optimization of biodiesel production using alkaline catalysts. Applied Engineering in Agriculture. 22(4) 597-600

    The most commonly used method for biodiesel preparation is via transesterfication of vegetable oil using alkaline catalysts. Biodiesel yield and oil conversion are affected by operating conditions including the catalyst formulation and concentration. Application of alkaline catalysts can also lead to undesired soap formation. This study evaluated the alkaline catalyst effects on biodiesel yield and soap formation in transesterifying methanol and canola oil at different catalyst concentrations, reaction temperatures, and methanol-to-oil molar ratios. Four different alkaline catalysts, i.e., potassium hydroxide, sodium hydroxide, potassium methoxide, and sodium methoxide, were studied and compared on molar basis through a 4-factor 3-level experimental design. It was observed that methoxide catalysts led to better biodiesel yields than hydroxide catalysts. The methoxide catalysts not only accelerated the reaction but also elevated the conversion equilibrium. Based on statistical optimization, the operating conditions for maximizing biodiesel yield and minimizing soap formation were potassium methoxide as catalyst at 0.2 mol/mol (1.59% wt), reaction temperature of 50 degrees C, and methanol-to-oil molar ratio of 4.5: 1. Experimental verification gave 95.8% biodiesel yield and 0.75%wt soap.
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  14. Process study on enzymatic hydrolysis of crambe oil for erucic acid isolation 2
    Abstract

    Tao, C.; He, B. 2007. Process study on enzymatic hydrolysis of crambe oil for erucic acid isolation 2. Transactions of the ASABE. 50(1) 167-174

    High erucic acid (HEA) seed oils can be processed enzymatically to produce biodiesel and erucic acid (EA), a valuable industrial feedstock. This study aimed to conduct a research on an effective reaction pathway to isolate EA from other fatty acids in HEA oils utilizing appropriate lipase specificities. Crambe oil was chosen as the model working feedstock. Rhizomucor miehei lipase was chosen to selectively hydrolyze crambe oil to liberate EA from the HEA oil directly into free EA. The effects of reaction parameters, including water content, lipase concentration, mixing intensity, and reaction temperature, were studied. Experimental results of an orthogonal design showed that the effect of process parameters was significant for the reaction rate, but insignificant for the reaction selectivity. Further statistical analysis revealed that lipase concentration had the most significant effect on the reaction rate, while water content showed a negative effect on the hydrolysis. Individual effects of aqueous phase ratio, initial lipase concentration, and mixing intensity were further investigated separately at the optimal lipase activity temperature. Results showed that water played a role mainly in affecting the specific interfacial area in the heterogeneous process of crambe oil hydrolysis. The interfacial reaction rate increased with the increase in initial lipase concentration, but was limited by a critical value. Mixing intensity affected the hydrolysis to a certain extent and then leveled off due to the lack of further size reduction of the discrete phase
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  15. Characterization of crude glycerol from biodiesel production from multiple feedstocks
    Abstract

    Thompson, J. C.; He, B. B. 2006. Characterization of crude glycerol from biodiesel production from multiple feedstocks. Applied Engineering in Agriculture. 22(2) 261-265

    Glycerol is the principal by-product of biodiesel production. For each gallon of biodiesel produced, approximately 0.3 kg of crude glycerol accompanies. Such crude glycerol possesses very low value because of the impurities contained. As the demand and production of biodiesel grow exponentially, the utilization of the glycerol becomes an urgent topic. The make-up of crude glycerol varies depending on the parent feedstock and the biodiesel production process. Before the crude glycerol could be considered for possible value-added utilizations, it is necessary to characterize it on its physical, chemical, and nutritional properties. This article reports the characterization of crude glycerol obtained from different seed oil feedstocks of mustard, rapeseed, canola, crambe, soybean, and waste cooking oils. Batch processes of biodiesel production were used as the means of crude, glycerol preparation using unrefined vegetable oils, methanol, and sodium methylate as the catalyst. After separation from biodiesel, the crude glycerol from each of the oils was analyzed using ASTM and other standard test methods. Elemental impurities, nutritional value, and other chemical properties were tested.
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  16. Biodiesel production using static mixers
    Abstract

    Thompson, J. C.; He, B. B. 2007. Biodiesel production using static mixers. Transactions of the Asabe. 50(1) 161-165

    Static mixers, devices used for mixing immiscible liquids in a compact configuration, were found to be effective in carrying out initial transesterification reactions of canola oil and methanol. The objective of this study was to explore the possibilities of using static mixers as a continuous-flow reactor for biodiesel production. Biodiesel (canola methyl ester) was produced under varying conditions using a closed-loop static mixer system. Sodium methoxide was used as the catalyst. Process parameters of flow rate or mixing intensity, catalyst concentration, reaction temperature, and reaction time were studied. A full-factorial experimental design was employed, and samples were analyzed for unreacted glycerides as an indicator for biodiesel quality control. It was found that static mixers can be used for biodiesel production. In fact, given enough residence time, appropriate temperature, and high mixing rate, a reactor could consist solely of static mixers and pumps in a continuous-flow design. Temperature and catalyst concentration had the most influence on the transesterification reaction. The data clearly indicates separate inverse linear relationships between temperature and catalyst concentration verses total glycerin. The ASTM D6584 specification for total glycerin (0.24% wt, max.) was met at three of the four temperatures tested, utilizing two of the four catalyst concentrations. The most favorable conditions for completeness of reaction were at 60 degrees C and 1.5% catalyst for 30 min.
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  17. Biodiesel processing and production
    Abstract

    Van Gerpen, J. 2005. Biodiesel processing and production. Fuel Processing Technology. 86(10) 1097-1107

    Biodiesel is an alternative diesel fuel that is produced from vegetable oils and animal fats. It consists of the monoalkyl esters formed by a catalyzed reaction of the triglycerides in the oil or fat with a simple monohydric alcohol. The reaction conditions generally involve a trade-off between reaction time and temperature as reaction completeness is the most critical fuel quality parameter. Much of the process complexity originates from contaminants in the feedstock, such as water and free fatty acids, or impurities in the final product, such as methanol, free glycerol, and soap. Processes have been developed to produce biodiesel from high free fatty acid feedstocks, such as recycled restaurant grease, animal fats, and soapstock. (c) 2004 Elsevier B.V. All rights reserved
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  18. Improving the Fuel Properties of Soy Biodiesel
    Abstract

    Wang, P. S.; Thompson, J.; Clemente, T. E.; Van Gerpen, J. H. 2010. Improving the Fuel Properties of Soy Biodiesel. Transactions of the Asabe. 53(6) 1853-1858

    Certain undesirable characteristics are associated with the use of soy methyl esters as a direct replacement for petroleum diesel fuel. When compared to petroleum diesel, soy methyl esters have higher NOx emissions, poorer cold flow, and a shorter shelf life. This article investigates whether the careful choice of alcohol and triglyceride feedstocks can improve these fuel properties. Three different triglyceride feedstocks with three different levels of oleic acid were examined. It was determined that a high amount of oleic acid in the triglyceride feedstock eliminates the tradeoff between cold flow and oxidative stability. The study also examined the role of three different alkyl groups (methyl, ethyl, and isopropyl) on the high-oleic feedstock. In NOx emissions testing, no significant difference was found between the alkyl groups. Isopropyl esters had the best cold flow properties, while methyl esters had the poorest cold flow properties for the three different alkyl groups. The induction periods for the methyl and ethyl esters from the high-oleic feedstock were 14 and 26 h, respectively, according to the Rancimat method. These numbers are in close agreement with the oxidative stability index. Isopropyl esters from the high-oleic feedstock had an induction period of less than an how; which was unexpected. Further investigation revealed that the high-oleic isopropyl esters had no vitamin E in the form of alpha-tocopherol, and it was speculated that the washing step in the manufacture of the fuel removed all vitamin E content.
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