Synthesis of Biodiesel Fuel

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

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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

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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

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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 forests 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

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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

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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

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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

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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
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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.
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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

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Synthesis of Biodiesel Fuel

• Procedure (cont)
• 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

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

• Procedure (cont)
• 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)

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Synthesis of Biodiesel Fuel

• Procedure (cont)
• 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