Proposal to Determine Various Properties of Biodiesel Fuels Based on Methyl Ester. Composition. Jason Freischlag. Dr. Porter Chem /25/2013

Transcription

1 1 Proposal to Determine Various Properties of Biodiesel Fuels Based on Methyl Ester Composition Jason Freischlag Dr. Porter Chem /25/2013

2 2 Specific Aims Biodiesel is an alternative fuel source that can be produced from vegetable oil, animal fat oil, or used cooking oil. It is different from diesel in that biodiesel is produced from renewable resources. Diesel on the other hand is produced from petroleum oil, a fossil fuel. Biodiesel fuels have great potential as they are much cleaner than typical diesel fuels and can reduce the huge dependency of the world on fossil fuels. Although in theory biodiesel usage seems to have tremendous advantages, it does not come without its disadvantages, including, but not limited to, a higher cloud point which leads to engine filters becoming clogged due to cold temperatures. This leads to biodiesel blends that reduce the dependency on fossil fuels while maintaining some of the advantages they offer as far as climate issues. Using simple separatory techniques on a feedstock yields an organic oil comprised of a triglyceride mixture. Many methyl esters may result from this process with the only difference being the length of the carbon chain and the degree of unsaturation in this chain. Although there are many molecules the four most predominant are palmitic acid, stearic acid, lineolic acid, and oleic acid. Transesterification is an effective method for creating biodiesel from this oil with minimal lab preparation. Gas chromatography using a flame ionization detector is an ideal method for determining biodiesel content because biodiesel consists mostly of a variety of the carboxylic acids discussed above and their methyl ester derivatives. A flame ionization detector is suitable because it is extremely sensitive to organic molecules and the fact that it is destructive is not a limiting disadvantage. Other important fuel properties include cloud point, heat of combustion, pour point, cetane index, acid value, and iodine value. This research will look

3 3 to examine these properties with respect to the concentrations of the four molecules discussed above. The methods and instruments for determining these values experimentally are documented below. Introduction Pyrolysis is the thermochemical decomposition of organic compounds in the absence of oxygen. This process has gained increasing attention as an efficient method for the creation of biofuels. Pyrolysis is useful because it can convert different feedstocks into useable fuels in a simple process that is the same regardless of stock, thereby wasting as little energy as possible. Pyrolysis of feedstock into biodiesel is similar to the epoxide chemistry that is used to convert crude oil into petroleum. Both processes require a final reduction step in order to create the diesel or biodiesel fuel. Transesterification is the process of exchanging the R group of an ester with the R group of an alcohol; thereby resulting in a different ester and a different alcohol. This process is an Sn 2 reaction that can be catalyzed with either an acid or a base. Acid catalyzing results in a protonated carbonyl of the ester which makes it a better electrophile for attack by the alcohol whereas base catalyzing deprotonates the alcohol making it an excellent nucleophile. Transesterification is a useful process in that it allows for bulk quantities of biodiesel to be easily produced from triglycerides leaving behind a liquid glycerine by product. The cetane index of a fuel is a measure of its ignition quality and indicates the ability to ignite spontaneously in the combustion chamber. The higher the cetane index, the shorter the ignition delay and the easier the fuel is to ignite; the higher the cetane index, the

4 4 chemical equation for transesterification better the ignition quality of the fuel. The cloud point is the temperature at which a fuel begins to form wax crystals. The lower the cloud point the better the fuel because the environment could be colder before crystals start to form. These crystals very easily clog up filters. Cloud point is directly attributed to the saturated methyl ester content because saturated fats solidify faster than unsaturated fats. The pour point is the temperature at which a fuel loses its flow characteristic. The lower the pour point the better the fuel for the same reasons seen in the cloud point. As the temperature of a fuel approaches the pour point it will no longer be able to flow. Heat of combustion is the energy released per mol of fuel when the fuel is burned. This is one of the most important properties of fuel and is the basis for dealing with fuel efficiency. A large heat of combustion means more energy is released and it is a more efficient fuel source than that with a lower heat of combustion. Acid value refers to the mass of potassium hydroxide, in milligrams, that is required to neutralize one gram of a chemical substance and is useful in determining the number of carboxylic acid functional groups on a molecule. Acid value is measured by dissolving a

5 5 known amount of sample in an organic solvent and titrating it with a solution of known concentration of KOH with phenolphthalein indicator. The Iodine value is the mass of iodine in grams that can be consumed by 100 g of a substance. This is a way to measure unsaturation of a molecule as the carbon carbon double bonds react with the iodine compounds. The higher the iodine value the more double bonds present in a molecule. Structures of Protonated Methyl Esters in Biodiesel and in Diesel Literature Review Biodiesel fuel has been receiving major attention as a potentially viable green alternative to gasoline and traditional fossil fuels. While biodiesel is unlikely to completely replace traditional gasoline there is no doubt in its potential to lessen the dependence of

6 6 industrialized societies on fossil fuels. Because biodiesel simply refers to diesel made from renewable vegetable oil or animal fat it follows that there are many forms of biodiesel. Each form of biodiesel is a mixture of various hydrocarbons and methyl esters which causes the chemical properties of each form to vary. In order to evaluate the applications of biodiesel it is essential to first establish which properties accurately describe a mixtures efficiency as a fuel. This literature review will look to address many topics involved in the determination of biodiesel fuel efficiency including which properties best best describe a viable fuel, how these properties relate to fuel efficiency, which methods are best to determine the quantitative values of these properties, as well as which feedstocks are most currently used in biodiesel production. Article 1 Liquid Hydrocarbons from Catalytic Pyrolysis of Sewage Sludge Lipid and Canola Oil: Evaluation of Fuel Properties 1 This research examined the physical properties associated with diesel compared to biodiesel, specifically that made from sewer sludge or canola oil. The chemical properties selected for comparison in this research were cloud point, pour point, specific gravity, viscosity, distillation range, cetane index, flash point, heat of combustion, water and sediment, ash, carbon residue, and elemental analysis. Pyrolysis products were also analyzed using gas chromatography, IR spectroscopy, and 13 C NMR. The cloud point, spectra, and chromatograms all suggested that these sources may be be able to provide a capable replacement to diesel fuel. Following sewage sludge lipid and canola oil pyrolysis the gas chromatographic

7 7 analyses for the liquid products were performed with a flame ionization detector and fused silica column using the following parameters: detector temperature 250 *C; injector temperature 250 *C; temperature program, 5 min at 50 *C; heated at a rate of 50 *C/min to 210 *C; hold for 30 min. The carrier gas (He) flow rate was 8 ml/min. The products were analyzed using 13 C NMR and IR, specifically looking for carbonyl groups. All fuel properties were determined using the American Society for Testing and Materials (ASTM) standard methods including cetane index (D 976), cloud point (D 2500), pour point (D 97), and heat of combustion (D 240). Each test was run on sludge lipid and canola oil biodiesels as well as regular diesel fuel. The cetane index of both the biodiesels were found to be higher than that of regular diesel indicating that biodiesel is actually better at igniting than diesel fuel. The cloud point of both biodiesels was higher than the diesel counterpart which indicates that biodiesels are not as applicable for colder weather climates. The pour point of both biodiesels was greater than of regular diesel. The heats of combustions for both biodiesels were comparable to that of biodiesel and indicate either could be used as an efficient alternative. IR of both biodiesels showed a weak carbonyl peak at 1720 cm 1 which is indicative of a carboxylic acid. 13 C NMR of both products showed exclusively hydrocarbon signals with a touch of residual solvent toluene. No carbonyl signal was seen for either biodiesel NMR confirming that both biodiesel reactions were run to completion. Gas chromatography of the both biodiesels resulted in a fairly uniform hydrocarbon chain length distribution of chains of 7 to 17 carbons. The Chromatogram of diesel shows a similar distribution to that

8 8 of the biodiesels, only lacking the 7 to 9 carbon length chains. This research shows that all the physical properties associated with biodiesel are intertwined and that the difficulty in interpreting these results comes mostly in understanding the relationships between the values. According to this experiment biodiesel shows great potential as an alternative fuel source as it mirrors many of the key chemical properties of diesel. Furthermore, the differences between sewer sludge and canola oil biodiesels were negligible in most cases. Article 2 Thermodynamic Study on Cloud Point of Biodiesel with its Fatty Acid Composition 2 This thermodynamic study used various fatty acid methyl esters to establish a prediction model for the cloud point of actual biodiesel made from different feedstocks based on their chemical composition. This study found that the cloud point of a biodiesel mixture could be determined by the amount of saturated fatty acid methyl esters regardless of composition of unsaturated esters. Biodiesel naturally borrows chemical characteristics from the oils and fats it was made from. Saturated fats have high melting points which means the biodiesel produced from these fats would likewise have a high melting point. This is a severe concern during cold weather as freezing gas could destroy an engine. Unsaturated fats have a lower melting point but at the same time are more likely to undergo oxidation. This oxidation of fuel can cause engine damage as well so a balance between these two properties is desired; for this reason biodiesel is usually synthesized from semi drying oils like rapeseed and soybean oils. Base catalyzed transesterification was used to synthesize biodiesel fuel from

9 9 sunflower oil, coconut oil, rapeseed oil, soybean oil, olive oil, peanut oil, beef tallow, and palm oil. Each of the products were classified based on weight percent of various fatty acids present. Based on the data from this experiment it can be seen that these biodiesels consist mostly of palmitic acid, stearic acid, oleic acid, and linoleic acid. These four methyl esters were chosen to make standards in various molar ratios for use as a model for predicting the behavior of biodiesel fuel. Composition of each biodiesel in relation to methyl ester composition were analyzed using HPLC with the following conditions: column, STR ODS II; flow rate, 1mL/min; eluent, methanol; detector, refractive index detector; temperature, 40 *C. Cloud point of both biodiesels and methyl ester mixtures were measured using the MPC 102 cloud point tester covering a range from 60 *C to 51 *C. The range of recorded cloud points went from 270 K to 290 K which is a noticeable difference in a crucial temperature range when dealing with natural environments. Furthermore, it was found that cloud point could be predicted based on molar ratios using known enthalpy values, assuming a eutectic system. The data supports the notion that cloud point is based primarily on the ratios of saturated esters; unsaturated esters have a negligible effect on cloud point because once one component of a mixture begins to crystallize the entire solution becomes cloudy. Oxidation and polymerization of the fuel caused by unsaturation can be remedied by using mono unsaturated esters as opposed to those with higher degrees. This experiment shows that there is a tool to accurately estimate fuel properties and a way to determine optimal fatty acid methyl ester composition. Article 3 Few Physical, Chemical and Fuel Related Properties of Honne Oil and its blends

10 10 with diesel fuel for their use in diesel engines 3 This study examines the viability of honne oil feedstock as a potential renewable diesel alternative. Based on the information presented in this article honne oil offers a viable alternative that matches many of the desired properties of diesel fuel when used in a biodiesel diesel blend. Cetane number was calculated using the formula CN = (5458)/SV 0.225*IV where SV is the saponification value and IV is the iodine value. Saponification value and iodine value as well as acid value were all measured using titrimetric methods. Cloud point and pour point were measured using a cloud apparatus and a pour apparatus. Viscosity was measured using a redwood viscometer. heating value was determined using a bomb calorimeter. Ash was quantitated using an ash content apparatus. The distillation temperature was found using a distillation apparatus. Article 4 Calculation of Higher Heating Values of Biomass Fuels 4 Heating values of biomass, or heats of combustion, can be determined experimentally or calculated. The goal of this work was to determine new formula for calculating heating values of fuels by their proximate analysis data. Proximate analysis resulted in values for weight fraction of moisture, volatile matter, fixed carbon, and ash as set up by ASTM method E It was also found that the yield of volatile materials can be increased by increasing the heating rate and the temperature of the pyrolysis process. Heating values of fuels were measured using a bomb calorimeter and ASTM method D2015. Article 5 Physical, Chemical, and Fuel Related Properties of Tomato Seed Oil for

11 11 Evaluating its Direct use in Diesel Engines 5 Food industries naturally produce substantial amounts of inedible waste. Processing these unwanted byproducts can result in a product of value with potential as a biodiesel fuel. Tomato seed is the major byproduct of tomato paste manufacturing and shows potential as a raw material capable of producing biodiesel. Tomato seeds were separated from pulp and dried using a silica gel desiccant. Oil was then extracted from the seeds using hexane and a soxhlet extractor and purified by rotary vacuum evaporation. Fatty acid composition was determined using gas chromatography. A flame ionization detector was used with helium carrier gas. The sample was injected at 230*C while the oven temperature was kept at 175*C for 30 minutes before being raised at a rate of 3*C/min up to a temperature of 220*C. The contents were quantified and identified using the external larodan standard Cetane index was found using the same formula above and other fuel related properties were determined based on ASTM procedures as per the other articles. 16 fatty acids were present in the oil according to GC results but the same four as previously mentioned were predominant, with linoleic acid comprising 56% of the oil. Iodine value is the measure of unsaturation of a fuel and the value found for tomato oil (124) is well within the recommended range (80 145). Instrumentation GC with flame ionization detector Bomb calorimeter Cloud point apparatus

12 12 Pour point apparatus Rotavap Methods and results Feedstocks will be ground and soaked in hexane to dissolve all oil. This oil will be rotary vacuum filtered and processed via transesterification to yield a biodiesel product. GC will be used to identify methyl ester composition in the biodiesel. A flame ionization detector will be used because of cost efficiency as well as specificity to these molecules. Cloud point of these biodiesels will be determined using a cloud point apparatus, pour point will be found using a pour point apparatus. A bomb calorimeter can be used to find the heat of combustion of the powdered form. Based on the information obtained in the literature review It is estimated that there will be a correlation between the unsaturation degree and the values of these fuel properties. Biodiesel offers some positive benefits while regular diesel comes with others. The future of fuel comes in understanding the best relationship between these two. Also based on these reviews it can be seen that there is a methodical approach to understanding how the chemical composition of biodiesels affect their properties and that transesterification is a common mode of synthesis when dealing with biodiesel. It can be observed that the most common feedstocks used to produce biofuel are rapeseed oil and olive oil because they produce a good combination of desirable physical properties. The cloud points of the biodiesel products from rapeseed oil and olive oil are lower than the competing versions that were tested. Bomb calorimetry is the standard means of measuring heat of combustion, although there are multiple standard methods available to follow. HPLC offers a method for determining the chemical

13 13 composition of the biodiesel fuels. Titration is a possible means of finding acid value, saponification value, and iodine value. Literature Cited (1) Bahadur, N., D. Boocock, and S. Konar (1994) Liquid Hydrocarbons from Catalytic Pyrolysis of Sewage Sludge Lipid and Canola Oil: Evaluation of Fuel Properties. Energy & Fuels 9(1995): (2) Imahara, H., E. Minami, and S. Saka (2006) Thermodynamic Study on Cloud Point of Biodiesel with its Fatty Acid Composition. Fuel 85(2006): (3) Belagur, V., and V. Chitimi (2013) Few Physical, Chemical and Fuel Related Properties of Honne Oil and its Blends with Diesel Fuel for their Use in Diesel Engines. Fuel 109(2013): (4) Demirbas, A. (1996) Calculation of Higher Heating Values of Biomass Fuels. Fuel 76(1996): (5) Giannelos, P.N., S. Sxizas, F. Zannikos, and G. Anastopoulos (2004) Physical, Chemical, and Fuel Related Properties of Tomato Seed Oil for Evaluating its Direct use in Diesel Engines. Industrial Crops and Products 22(2005):