Synthesis of Biodiesel Fuel

Synthesis of Biodiesel Fuelfrom 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

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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 forest’s capacity to absorb CO2)

New higher efficiency method emerging utilizing a Sulfated Zirconia catalyst

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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

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Alkoxide

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

Fatty Acid Methyl Esters (FAME)

Synthesis of Biodiesel Fuel Reaction – Mechanism

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The same mechanism is repeated two more times on the 2 other ester groups of the trimester until the final product is3 Fatty Acid Methyl esters (FAME) and one glycerol.The three reactions occur sequentially.

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)

Fatty Acid Methyl Ester (FAME)

Tetrahedral (sp3)Intermediate

Alkoxide ion

Trimester of Glycerol (1,2,3-propanetriol)and a long chain fatty acid

1st Stage

Repeat for stages 2 & 3

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 (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 standNote: No need to run water through the condenser

Lower the distillation flask into the water bath

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Synthesis of Biodiesel Fuel

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Mixture of vegetable oil,Methyl Alcohol, andPotassium Hydroxide

CondenserNo Water Flow

Blue PlasticClamp

Water Bath55oC

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)

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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 – 68476-34-604/18/23 16