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Synthesis of Biodiesel Fuel

Synthesis of Biodiesel Fuel. Synthesis of Biodiesel Fuel from Vegetable Oil References: Pavia - p. 207 – 216 - p. 194 – 202 (Essay – Petroleum and Fossil Fuels Schornick

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Synthesis of Biodiesel Fuel

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  1. Synthesis of Biodiesel Fuel Synthesis of Biodiesel Fuel from Vegetable Oil References: • Pavia - p. 207 – 216 - p. 194 – 202 (Essay – Petroleum and Fossil Fuels • Schornick http://classweb.gmu.edu/jschorni/chem318

  2. Synthesis of Biodiesel Fuel • Background • Fossil fuels • Slow decay of marine animal and plant organisms over periods of millions of years • Significant source of pollution • Significant contributor to green house gases, principally CO2 • High potential for environmental disasters such as oil spills, drilling rig failures, chemical plant explosions & fire, etc. • Finite – We are depleting this non recoverable supply

  3. Synthesis of Biodiesel Fuel • Background • Biofuels: Fuels produced from biological materials • Ethanol (Gasohol) • Starch (polymer of Glucose) • Corn (Enzymes catalyze corn starch into glucose • Expensive to produce • Energy inefficient • Produces more green house gases • Sucrose (Fermentation of Sugar Cane & Beets) • Cellulose • Switchgrass • Agricultural waste, including corn stalks • Waste wood from milling

  4. Synthesis of Biodiesel Fuel • Background • Biofuels • Ethanol • Syngas (CO & Hydrogen converted to Alcohol) • Utilizes wide array of Carbon-containing matter • Municipal Waste • Old Tires • Agricultural Waste • More Energy Efficient Than Ethanol • Produces less greenhouse gases

  5. Synthesis of Biodiesel Fuel • Background • Biofuels • Biodiesel (from fats & oils, including vegetable oil) • Farm products • Large investment in farmland not dedicated to food production • Net energy produced is greater than from Ethanol but less than for cellulose • Produces more greenhouse gases than fossil fuels • Destruction of forested areas to establish farmland (loss of forest’s capacity to absorb CO2) • New higher efficiency method emerging utilizing a Sulfated Zirconia catalyst

  6. Synthesis of Biodiesel Fuel • Background • Biofuels • Biodiesel (from fats & oils, including vegetable oil) • Algae • Can produce oils for making biodiesel • Grown in ponds or sewage waste water • Several approaches, catalysts, self-contained manufacturing facilities, etc. are being investigated in search of economically viable processes

  7. Synthesis of Biodiesel Fuel • The Experiment • In the Banana Oil experiment, an organic acid is combined with an alcohol in a catalyzed Fischer Esterification (condensation) reaction to produce a mono ester • In this experiment the reverse of the process (hydrolysis by H2O, Acid or OH- to the alcohol and acid) is modified in a transesterification reaction, in which an original trimester is converted to three (3) mono esters by reaction with an alkoxide base

  8. Synthesis of Biodiesel Fuel • Analysis of Biodiesel product • The trimester is cleaved sequentially by the alkoxide base (a mixture of Potassium Hydroxide and Methyl Alcohol), liberating the mono-esters and glycerol • The Mono esters are produced sequentially because the Alcohol/Alkoxide base has only one Hydroxyl group • The mono esters are Fatty Acid Methyl Esters (FAME) • The Vegetable oil and biodiesel product molecules have variable composition • Three Methyl esters of fatty acids are formed each with a different “R” group consisting of 12-18 carbons arranged in straight chains

  9. Synthesis of Biodiesel Fuel • Analysis of Biodiesel product • Thus, the computation of moles directly from the peanut oil mass is not practical • Show the stoichiometric and mechanism reactions • The Methyl Alcohol is in excess, but the theoretical yield cannot be determined; omit summary table • Calculate a “percent yield” from the initial mass of the Vegetable oil and the mass of the diesel fuel product • Compare the original IR of the vegetable oil (seep. 102 in Slayden Manual) to the biodiesel IR

  10. Synthesis of Biodiesel Fuel • Reaction Alkoxide Fatty Acid Methyl Esters (FAME) An Alkoxide is the Conjugate Base of an Alcohol It consists of an organic group bonded to a negatively charged Oxygen atom Alkoxides are strong Bases and, when R is not bulky, good nucleophiles and good ligands

  11. Synthesis of Biodiesel Fuel • Reaction – Mechanism Trimester of Glycerol (1,2,3-propanetriol)and a long chain fatty acid The negative charge of the Alkoxide (Methoxide) ion attacks the positive charge of the carbonyl carbon atom (from the resonance dipole form of the carbonyl group) Alkoxide ion Fatty Acid Methyl Ester (FAME) Tetrahedral (sp3)Intermediate 1st Stage Repeat for stages 2 & 3 The same mechanism is repeated two more times on the 2 other ester groups of the trimester until the final product is 3 Fatty Acid Methyl esters (FAME) and one glycerol.The three reactions occur sequentially.

  12. Synthesis of Biodiesel Fuel • Procedure • Reagents • 10 mL Vegetable Oil (Crisco) – A Trimester • 2.0 mL Potassium Hydroxide/Methyl Alcohol solution (forms Methoxide ion, an Alkoxide ion) • Prepare a water bath in a 150 mL beaker on a hot plate • Heat the water bath to a temperature of 55oC • Tare weight an empty 100 mL beaker or small cork ring sitting on the balance to the nearest 0.001 g • Place an empty 25 mL round-bottom flask onto the beaker top or on the cork ring • Determine the mass of the empty flask by difference

  13. Synthesis of Biodiesel Fuel • Procedure (con’t) • Place 10 mL of vegetable oil into the pre-weighed distillation flask • Determine the mass of the flask and vegetable oil • Determine the mass of the vegetable oil by difference • Add ~2.0 mL of the fresh KOH/CH3OH solution to the distillation flask • Swirl the mixture to ensure a uniform solution • Insert a small magnetic stir bar into the flask • Attach and secure (with a blue plastic clamp) the flask to a water-jacket condenser clamped vertically to a ring stand Note: No need to run water through the condenser • Lower the distillation flask into the water bath

  14. Synthesis of Biodiesel Fuel Condenser No Water Flow Mixture of vegetable oil, Methyl Alcohol, and Potassium Hydroxide Blue Plastic Clamp Water Bath 55oC

  15. Synthesis of Biodiesel Fuel • Procedure (con’t) • Turn on the magnetic stirrer (Left knob on hot plate)to the highest level possible that allows the bar to spin smoothly • Stir for 30 minutes • Transfer all of the liquid in the flask to a 15-mL centrifuge tube with a cap • Let the mixture sit for about 20 minutes • Two layers should form • The top layer is the biodiesel product • The lower layer is mainly glycerol • Using a plastic pipet, carefully remove the top layer and transfer product to a pre-weighed 50-mL beaker (leave a little product behind with the bottom layer to avoid contamination)

  16. Synthesis of Biodiesel Fuel • Procedure (con’t) • Place the beaker on the hot plate and insert a thermometer into the biodiesel, holding the thermometer in place with a clamp • Heat the biodiesel to about 70oC for 15-20 minutes to remove all the Methyl Alcohol • Remove the beaker from the hot plate and allow it to cool to room temperature • Weigh the beaker and obtain the mass of biodiesel produced • Record the appearance of the biodiesel • Obtain an IR spectrum • CAS No. for diesel fuel – 68476-34-6

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