Lab 9 Biodiesel For Environmental Science

M500

Lab9BiodieselForEnvironmentalScience.pdf

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Synthesis of Biodiesel Carolina Distance Learning

Investigation Manual

Table of Contents

Overview ......................................................................................................... 4

Objectives ....................................................................................................... 4

Time Requirements ........................................................................................ 4

Background .................................................................................................... 5

Materials .......................................................................................................... 9

Safety ............................................................................................................. 10

Activity 1: Synthesis of Biodiesel ................................................................ 11

Activity 2: Testing for Quality ..................................................................... 12

Disposal and Cleanup ................................................................................ 12

Data Table .................................................................................................... 13

Overview

In this investigation, students will perform a transesterification of vegetable oil in the

presence of a solid catalyst to produce biodiesel. Students will test for the presence of

contaminants such as soap to determine the purity of their sample.

Objectives

 Synthesize biodiesel using a solid-state catalyst.

 Test synthesized biodiesel for quality.

 Describe the synthesis pathway for biodiesel.

Time Requirements

Preparation .............................................................................................10 minutes

Activity 1 .................................................................................................60 minutes + 1 day

Activity 2 .................................................................................................90 minutes

Background

Renewable sources of energy and fuel are becoming increasingly valuable. Unlike the

most common form of diesel, which is distilled from petroleum, biodiesel can be

produced from a variety of renewable sources. The adoption of alternative fuel

sources, such as biodiesel, can help reduce our dependence on fossil fuels.

Biodiesel has several advantages over traditional petroleum diesel. It is cleaner burning,

producing less particulate matter and less carbon monoxide. In post 2010 vehicles with

modern emission control technologies, nitrogen oxides (NOx) emissions are comparable

to traditional diesel. Though biodiesel still releases carbon dioxide into the atmosphere,

that carbon had to be recently sequestered into the tissues of the plants from which the

oil was made, so there is no net increase of carbon dioxide in the atmosphere. Biodiesel

is biodegradable and non-toxic, and can be used in several ways. Diesel engines

require no modifications in order to use it as a fuel, though engines that have run on

petroleum diesel may experience clogged filters and pipes since biodiesel strips

deposits left behind by other petroleum diesel. Biodiesel can also be used in place of

heating oil in homes.

The biodiesel production process has surprisingly few steps. Generally, all that is required

is a pure vegetable oil, a solid base like potassium hydroxide or calcium hydroxide, and

methanol. Calcium hydroxide, for example, is mixed thoroughly with methanol to

produce calcium methoxide. Vegetable oil is then added to the methoxide and mixed.

The triglycerides in the oil react with the methoxide through a transesterification

reaction to create methyl esters (biodiesel) and glycerol. The solution then separates

into a layer of biodiesel and a layer of glycerol, which facilitates the easy collection of

the biodiesel.

Unfortunately, there are some drawbacks to biodiesel as a fuel as well. It does not

perform well at low temperatures, making it unsuitable for some climates. It is more

expensive than traditional fuels. The most energy efficient source of oil is virgin oil, often

derived from animal fats, corn, canola, or soy. Land used to generate biodiesel crops is

not being used for food crops. This can cause food prices to rise. One solution is to use

recycled oil. The use of oil that is recycled, such as from a deep fryer, has more

contaminants that need to be removed through filtration or other chemical processes.

The oil must also be subjected to a drying process to remove excess water, reducing

the efficiency of the process.

Another potential contaminant can arise in the oil itself, in the form of free fatty acids.

These fatty acids can interfere with the transesterification reaction and generate soap

instead of biodiesel.

In this investigation, corn oil will be used for the creation of your biodiesel. Because the

oil was not previously used, filtration will not be necessary before the synthesis.

The provided methanol is a required reagent for the transesterification reaction. The

calcium hydroxide reacts with the methanol (CH3OH) to yield calcium methoxide,

Ca(OCH3)2, which acts as a catalyst for the subsequent reaction.

Detailed Synthesis

The first reaction in this activity is the synthesis of calcium methoxide. Calcium hydroxide

is added to methanol where it reacts to form calcium methoxide. In the second

reaction, the calcium methoxide acts as a catalyst, facilitating the transesterification of

methanol with triglycerides, to produce glycerol and fatty acid esters.

Methoxide Synthesis

Biodiesel Synthesis

First, the calcium methoxide reacts with the methanol, creating a negative dipole at an

oxygen, and a positive dipole at a hydrogen. This molecule will react in the last step of

the process.

A second calcium methoxide then reacts with a fatty acid on a triglyceride, with the

calcium associating with the oxygen of the ester, and an oxygen of the calcium

methoxide reacting with the carbon of the ester. This product is then used in the final

step of the reaction.

In the third step of the reaction, the step one product, reacts with the step two product

to form the methyl ester (biodiesel) a diglyceride and regenerate the two catalyst

molecules of calcium methoxide. The process then repeats until each fatty acid is used

up and the end products are three methyl esters, and a glycerol molecule.

Typically, after a batch of biodiesel is created, a bevy of tests are conducted on the

sample, testing for the presence of a multitude of molecules and properties. For the

purposes of this investigation, pH, density and the presence of triglycerides will be

tested for. pH tests for free fatty acids that have not reacted in the process, these are

indicated by a lower pH and typically are the result of a lower quality stock oil. Density is

a test of biodiesel quality as the density of biodiesel of 0.88 g/mL. The final test is for the

presence of unreacted triglycerides, or intermediates such as a diglyceride. The

presence of these indicates an incomplete reaction.

Materials

Included in the materials kit:

Calcium hydroxide

Methanol

Vegetable oil

pH paper

3-dram vial

Needed from the equipment kit:

Balance

Test tube

10-mL graduated cylinder

Needed, but not supplied:

Paper towel

Water, bottled or purified

Reorder Information: Replacement supplies for the Synthesis of Biodiesel investigation

can be ordered from Carolina Biological Supply Company, kit 580372.

Call 1-800-334-5551 to order.

Safety

Wear your goggles, gloves, and lab

apron at all times while conducting this

investigation.

Read all the instructions for this laboratory activity before beginning the procedure.

Follow the instructions closely and observe established laboratory safety practices,

including the use of appropriate personal protective equipment (PPE) as described

in the Safety and Procedure sections.

Methanol is flammable. Keep this chemical away from any heat or

flame sources.

Calcium hydroxide causes skin irritation.

Calcium hydroxide is a corrosive material and can cause serious eye

damage.

Methanol can cause organ damage if ingested. Keep away from

food sources.

Methanol may be toxic if in contact with skin.

Do not eat, drink, or chew gum while performing this activity. Wash your hands with

soap and water before and after performing the activity. Clean up the work area

with soap and water after completing the investigation. Keep pets and children

away from lab materials and equipment.

Activity 1: Synthesis of Biodiesel

1. On the balance weigh approximately 0.02 grams of calcium hydroxide into the 3-

dram vial.

2. Measure 8 mL of methanol with a graduated cylinder.

3. Add methanol to the vial.

4. Cap vial and shake vigorously. Allow vial to sit for 10 minutes, shaking occasionally.

5. Carefully open cap away from your face as some pressure may build up.

6. Measure 1 mL of vegetable oil with a graduated cylinder.

7. Add vegetable oil to the vial, and cap the vial.

8. Shake vial vigorously.

9. Allow the reaction to occur over 48 hours. Shake the vial occasionally to allow the

solid calcium methoxide to react with the triglycerides.

Activity 2: Testing for Quality

1. Weigh an empty 10-mL graduated cylinder and record the mass in Data Table 1.

2. Using a pipet, extract some biodiesel from the vial. The biodiesel should be the top

liquid layer.

3. Dispense ~1 mL of biodiesel into the graduated cylinder. Record the exact volume

in Data Table 1.

4. Weigh the graduated cylinder with biodiesel and record the mass in Data Table 1.

5. Calculate the mass of the biodiesel.

6. Calculate the density of the biodiesel.

7. Take a strip of pH paper and dip it in the biodiesel.

8. Record the pH in Data Table 1.

9. Dispense ~1 mL of biodiesel into a test tube.

10. Measure 7 mL of methanol and add it to the test tube.

11. With a gloved hand, place your thumb over the mouth of the test tube and shake

vigorously.

12. Place the test tube in the test tube rack and allow it to sit for 10 minutes.

13. Record whether an insoluble layer forms. This layer contains unreacted triglycerides

or intermediates.

Disposal and Cleanup

1. Dispose of solutions down the drain with the water running. Allow the faucet to run a

few minutes to dilute the solutions.

2. Rinse and dry the lab equipment and return the materials to your equipment kit.

3. Sanitize the workspace.

Optional Extension Activity

1. Repeat Activities 1 and 2 using

Data Table

Data Table 1

Mass of

Graduated

Cylinder

Volume of

Biodiesel

Mass of G.C.

+ Biodisel

Mass of

Biodiesel

Density of

Biodiesel

pH of

Biodiesel

Presence of

Intermediates? (y/n)