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Soap and Biodiesel Synthesis Abstract The purpose of this study is to determine how the characteristics of different oils affect the properties of the biodiesel produced by them, specifically which oil characteristics lead to lower freezing points, viscosity, and higher energy per gram of fuel for the biodiesel the oil produces. This was done by synthesizing both soap and biodiesel from a variety of different oils, since both procedures involve the same chemicals and would therefore give two different references to determine the relationship between oil characteristics and product properties. The result of this study was that the unsaturated:saturated ratio of the oil significantly impacts the melting point of the resulting biodiesel (meaning it does the same for freezing point), with higher unsaturated:saturated ratios resulting in higher IMFs, meaning higher melting and freezing points. The unsaturated:saturated ratios of the feedstock oils also directly impacted the viscosity of the biodiesel synthesized with them, with higher amounts of carbon double bonds (from unsaturated fatty acids) resulting in higher viscosities. Finally, the higher energy per gram of fuel is also influenced by the feedstock oil used. While these conclusions are drawn from molecular understanding inferences with examples from the data to back them, there are exceptions to these conclusions that are most likely a result of the synthesis process and human error during experimentation. Introduction The goal of this lab is to explore the relationship between molecular structure and physical properties using the synthesis of soap and biodiesel. One common approach to making soaps is the reaction of triglycerides with a concentrated strong base, in a process known as saponification. This is a type of chemical reaction in which ester molecules are broken to create a functional group of carboxylic acid and alcohol. Fats and oils are composed mainly of triglycerides, three fatty acids joined together by a glycerol backbone. During the synthesis of soaps, triglycerides are converted to fatty acid salts and glycerol; the properties of a fatty acid salt depend on the triglycerides from which they came from. In order to separate out the salts from the rest of the reaction products, a saturated NaCl solution is added. This forces the soap to coagulate without dissolving in the water. It can then be collected by filtration and washed to remove the excess base. Biodiesel is made by a reaction very similar to that of soaps where a triglyceride is reacted but biodiesel needs esterification. Esterification is the process of combining a carboxylic acid with an alcohol to form an ester and water. One very important property of biodiesel is its viscosity, a fluid's resistance to flow. Although these two substances are made in very similar manners, they have very different properties which will be explored in this lab.

Methods/procedure Soap Synthesis Protocol: 20 ml of canola oil were prepared 20 ml of ethanol were prepared 50 ml of a 10 M NaOH solution were gathered All of the above reactants were combined then placed on a hot plate The reactants were stirred on the hotplate until all the ethanol was dissolved and the product looked like a gummy marshmallow The beaker was removed and cooled before we added 100 ml of a saturated NaCl and mixed The beaker was covered properly and rested for 2 weeks Soap drying procedure: The products that were stored from week one was poured through a mesh screen to separate the soap from the remaining liquid The soap was then rinsed with water to ensure all excess liquids were gone The soap was then dried with paper towels and weighed Testing of Soap and Biodiesel: The soap was tested for foam deflation distance by adding 5 ml of DI water and a pea sized amount of soap and shaking to see the height difference in the bubbles To find the density 10 g of soap was submerged in water and the volume change was recorded The pH of the soap was found using pH paper Emulsification was found using a small amount of soap and 5 ml of DI water with 10 drops of mineral oil It was shaken and examined to see if the layers remained The biodiesel was tested using calorimetry A pop can was filled with 200g of water and 1.5 g of biodiesel was measured into a crucible A wick was placed into the oil and then lit, the flames was touching can and a thermometer was placed into the can without touching the bottom 2

The temperature was monitored, being watched to not go over 80C The time was measured for the biodiesel to be fully consumed and then calculated into J/g using q water (J) = m (g) * C (J/g.K) * ΔT (K) m = mass of water used C = heat capacity of water ΔT =change in temperature of water Biodiesel was also tested for presence of soap 2 ml of biodiesel and 5 ml of water were placed in a test tube and mixed If 2 distinct layers were formed no soap was present and if 3 layers were formed then soap was present Viscometry was tested using a Varnish Viscometer Tube where the time was recorded for the bubble to travel from the 27 line to the 100 line for both canola oil and glycerol The melting point of canola oil was found through attaching the thermocouple to the Pasco SparkLink interface and recording the range of temperatures on the thermocouple Results Table 1: Soap Summary of Properties Feedstock Oil Physical Characteristics Molecular Weight of Soap (g/mol) Theoretical Yield of Soap (g) Calculated Yield of Soap (%) Foam Deflation Distance (Inches) Calculated Density (g/mL) pH Emulsif -ication Olive Off white, chunky, soft, damp 300.64 18.987 237.26 0.82 1.11 9 No Sunflower White, chunky, moist, malleable 299.30 18.41 228.19 1.5 1.13 11 No Safflower Chunky, hard, white, and dry 300.97 19 250.89 2.2 1.12 11 No Canola Off white, soft, stringy, pliable 302.64 18.15 440 0.75 1.25 12 No Soybean Off white, chunky, damp 300.30 19.82 312.76 1.25 1.11 11 No 3

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Table 2: Biodiesel Summary of Properties Feedstock Oil Physical Qualities Calculated J/g Biodiesel 3 layers of soap? (if yes, time in seconds to separate) Viscosity Trial 1 (bubble seconds) Viscosity Trial 2 (bubble seconds) Average Viscosity (bubble seconds) Glycerol Control (bubble seconds) Melting Point Range Olive White, soft, chunky -15,627.73 Yes, 10 seconds 1.12 1.15 1.135 9.51 15 Sunflower White, chunky, soft, malleable -18,418 Yes, 20 seconds 1.13 1.1 1.115 9.47 14.9 Safflower Chunky, solid, white, dry 35,162.40 No (2 layers) 1.18 1.1 1.14 9.51 16 Canola White/yell ow, soft, smooth, stringy -14,511.47 Yes, 38 seconds 1.08 1.07 1.075 9.51 18.1 Soybean Yellow, soft, smooth -13,047.27 No (2 layers) 1.08 1 1.04 9.51 13.6 Table 3: Unsaturated: Saturated Ratio Feedstock Oil Unsaturated: Saturated Ratio Olive 4.6 Sunflower 7.3 Safflower 10.1 Canola 15.7 Soybean 5.7 Examples of Calculations (Using Canola Oil Results) Molecular Weight of Soap (g/mol) ((880-89.09)/3)+39= 302.64 g/mol 4

Calculated Percent Yield of Soap (79.86/18.15) times 100= 440 Calculated Density of Soap 10.0034g/8mL= 1.25g/mL Calculated J/g of Biodiesel 200 times 4.186 times 26= 21,767.2 -21,767.2/1.5= -14,511.4667 Average Viscosity of Biodiesel (1.08+1.07)/2= 1.075 Melting Point Range of Biodiesel 14.4+3.7= 18.1 Discussion Question 1 One connection between the soap structure and its properties is that the molecular structure of soap has a polar side and a nonpolar side to allow for emulsification. The COONa end is meant to attract water molecules and form hydrogen bonds since both are polar, while the nonpolar end is meant to form IMFs with nonpolar molecules that are dirt on the skin. In the case of this experiment, no soap was able to emulsify. This may be due to the large amount of excess NaOH added to the soap. As seen in the table, the pH of the soaps varied from olive oil soap’s pH of 9 to canola oil soap’s pH of 12. Since NaOH is a strong base, having too much NaOH that did not react during the saponification process will greatly affect the pH of the solution, which will prevent the soap from properly attaching to the dirt. As seen in the table, every soap could not emulsify the mineral oil with the water. High pH is the reasoning behind this. Another connection between soap structure and properties is that the higher the unsaturated:saturated ratio (or the more unsaturated fatty acids contained in the oil to make the soap), the less lather produced in the form of foam. This is shown most clearly between canola oil, which has the highest unsaturated:saturated ratio of 15.7 and the lowest foam deflation distance of 0.75, and soybean oil, which has a ratio of 5.7 and a foam deflation rate of 1.25. This is because the shorter and more saturated fatty acid chains are more easily dissolved in water, since the nonpolar portion of the fatty acid is smaller and more manageable than the unsaturated carbon chains with double bonds (Vidal, et. al., 2018). This pattern is not followed by all the soaps however, as seen with safflower oil with the 10.1 ratio and the 2.2 foam deflation rate. This is because how much foam is produced depends on multiple factors, such as the other non-water solutes in the solution such as the Na and Cl ions that were used to store the soap and again, the excess NaOH. 5

Question 2 The structure of biodiesel directly impacts the different properties of biodiesel. The main biodiesel properties that we tested are unsaturated/saturated ratio, calorimetry (specifically J/g of biodiesel), presence of soap, viscosity, and melting point range. All of the evidence related to biodiesel can be located in table 2. Canola oil had the highest unsaturated: saturated ratio at 15.7, while olive oil had the lowest at 4.6, and soybean had 5.7. All of the feedstock oils had similar physical characteristics. The lowest calculated J/g of biodiesel was sunflower oil at -18,418, while the highest calculated J/g of biodiesel was safflower oil at 35,162.40. Soybean oil had -13,047.27 and canola oil had a J/g ratio of -14,511.47. Olive, sunflower, and canola oil all had 3 layers of soap, while safflower and soybean oil only had two layers in their biodiesel. The longest time to see full separation of the layers of soap was 38 seconds for canola oil, and the quickest time to clearly see the layers was olive oil at 10 seconds. The highest average viscosity in bubble seconds was 1.14 for safflower, while the lowest was 1.04 for soybean oil. Canola had an average viscosity of 1.075 bubble seconds. The largest melting point range was seen by canola oil at 18.1 and the smallest melting point range was 13.6 for soybean oil. Biodiesel is made through the process of transesterification where an oil/fat (triglyceride) reacts with an alcohol. Biodiesel has a very low solubility in water because it is non-polar with the exception of two polar C-O bonds, so the strongest IMF in biodiesel is weak dipole-dipole, meaning biodiesel cannot dissolve in a polar solvent like water. One of the main ways to determine the structure of a fatty acid is to look at the unsaturated to saturated ratio. This is because it tells us the length of a carbon chain and if there are any double bonds. Canola oil had the highest unsaturated to saturated ratio because it had the highest number of oleic acid, linoleic acid, and alpha linoleic acid (all of which are unsaturated fats). Soybean oil had a lower unsaturated to saturated ratio because it had less unsaturated fats compared to canola oil (except for polyunsaturated fat). This means that canola oil would typically have longer carbon chains than soybean oil. Viscosity has a direct correlation with the number of carbon atoms. The double bond in unsaturated fatty acids produces a bend in the carbon chain that is more pronounced in cis configurations than trans configurations. Because of this, cis configurations cannot line up next to one another neatly, and that means molecules are more tightly packed in trans carbon chains, resulting in a higher viscosity. (Gopinath et al., 2014). This can be seen when comparing the average viscosity of canola oil (1.075 bubble seconds) to soybean oil (1.04 bubble seconds). Canola oil had the largest melting point range because the melting point increases with chain length for saturated compounds (Gopinath et al., 2014). Canola oil also had a higher calculated J/g of biodiesel than soybean oil because it had a greater total change in the temperature of the water by 2 degrees celsius. Finally, soybean oil did not have the presence of soap but canola oil did. According to an article by the National Library of Medicine, the saponification value was 189-195 for soybean oil and 188-193 for canola oil (Neupane, 2022). The ranges from the study are just small enough that it passes biodiesel soap percentage standards, so our results could be from canola oil or soybean oil having slightly more soap in the experiment conducted by the class. In conclusion, the properties found in biodiesel are different when created with contrasting feedstock oils. Question 3 All oils melted at a relatively consistent range, but canola oil melting lowest, at -3.7 C. The melting point of oils is affected by the length of the fatty acid chain. Canola oil has the largest unsaturated to saturated ratio (15.7), so it would have the lowest melting point. This 6

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would be beneficial in biodiesel because it wouldn't freeze as quickly when used in containers. Canola oil also has the second highest energy per gram. At -14511.4667J/G, it would combust energy more efficiently in comparison to the other oils tested. This would improve usage and efficiency when using biodiesel. Lastly, canola oil has low viscosity. While all tested oils are significantly similar, it does have the second lowest. This is also because of the high unsaturated ratio, making the oil not have significant viscosity. Question 4 (bonus) Canola oil would make a good soap, if treated properly. In the experiment, the soap had a pH of 12, but if cleaned and dried thoroughly, this could be down to 10. Canola oil has the lowest deflation of all oils tested, as well as no layers of emulsification. It would be beneficial to run the experiment again before concluding that it is safe, however with the data provided, canola oil would be a good candidate for soap making. Conclusion In order to determine how the characteristics of different oils affect the properties of the biodiesel produced by them, an experiment was conducted to produce soap with triglycerides. Oil characteristics with long fatty acid chains have lower freezing points. High unsaturated to saturated ratios lead to low viscosity. High energy per gram of fuel is directly related to the energy per bonds. In order to test these conclude these properties, experiments were conducted on the physical properties and compared to the molecular properties of oils. References Gopinath, A., Sairam, K., Velraj, R., & Kumaresan, G. (2014). Effects of the properties and the structural configurations of fatty acid methyl esters on the properties of biodiesel fuel: a review. Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering , 229 (3), 357–390. https://doi.org/10.1177/0954407014541103 Neupane, D. (2022). Biofuels from Renewable Sources, a Potential Option for Biodiesel Production. Bioengineering , 10 (1), 29. https://doi.org/10.3390/bioengineering10010029 Prieto Vidal N, Adeseun Adigun O, Pham TH, Mumtaz A, Manful C, Callahan G, Stewart P, Keough D, Thomas RH. The Effects of Cold Saponification on the Unsaponified Fatty Acid Composition and Sensory Perception of Commercial Natural Herbal Soaps. Molecules. 2018 Sep 14;23(9):2356. doi: 10.3390/molecules23092356. PMID: 30223479; PMCID: PMC6225244 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6225244/#B2-molecules-23-02356 . 7