Laboratory Investigation on Synthesis and analysis
of Biodiesel
Aims
i)
To prepare a sample of biodiesel from vegetable oil
ii)
To measure some of the properties of the biodiesel and compare these to that of
petrodiesel.
Part A Synthesis of biodiesel
• vegetable oil (100 mL)
• methanol (20 mL)
• sodium hydroxide (solid, 0.25 g)
• 250 mL beaker
• 500 mL beaker
• glass stirring-rod
• weighing boat
• electronic balance
•spatula
•2 x 100 measuring cylinder
•1 litre plastic bottle with cap
•safety glasses
•lab coat
• gloves
• Funnel
Safety
Risk assessment table
Material or procedure
Potassium
Hazard
Management
hydroxide Corrosive (toxic) to skin and Wear gloves, lab coat and
pallets
eyes. Harmful if swallowed.
Methanol
Highly flammable,
toxic
safety gloves.
if
Wear gloves, lab coat and
inhales, toxic with contact with safety
gloves,
wear
skin, toxic if swallowed and breathing apparatus. Work
causes damage to organs.
in
well
ventilated
area
(fume cupboard).
Biodiesel
Flammable liquid and vapor, Wear gloves, lab coat,
skin/eye irritant, harmful if
safety gloves.
inhaled, fatal if swallowed
(causes damage to organs).
Petrodiesel
Flammable liquid and vapor, Wear gloves, lab coat,
skin/eye irritant, harmful if
safety gloves.
inhaled, fatal if swallowed
(causes damage to organs).
Procedure
1. Using a measuring cylinder, measure 50 mL of vegetable oil (canola or peanut). Transfer it to
the 500 mL beaker.
2. Using a clean measuring cylinder, measure 10 mL of methanol. Transfer it to the 250mL beaker.
• Caution: methanol is poisonous and can be absorbed through the skin.
3. Using an electric balance, weigh out 0.25 g of sodium hydroxide.
• Caution: sodium hydroxide is a corrosive chemical. Avoid skin contact.
4. Slowly add the solid sodium hydroxide to the methanol.
• Caution: the product of this reaction, sodium methoxide, is poisonous. Avoid skin
contact.
• Gloves and safety glasses are essential during this phase of the preparation.
• This step should be conducted in a well-ventilated area or a fume cupboard to avoid
inhalation of the fumes.
5. Stir the methanol/sodium hydroxide mixture gently with a glass rod until the solid sodium
hydroxide is completely dissolved. Sodium hydroxide is slow to dissolve, so patience is required.
6. Add the methanol/sodium hydroxide mixture to the vegetable oil. Transfer the mixture to a 2 L
plastic drink bottle. Seal and shake gently for several minutes to mix thoroughly.
7. Leave the mixture to settle overnight. The lighter coloured layer on the surface is biodiesel. The
darker coloured layer at the bottom is glycerol.
8. Decant the biodiesel from the glycerol into a clean 500 mL beaker. The biodiesel will need
further processing before it can be used in an engine.
Part B: Properties of Biodiesel
(a) Density
1. Weigh a 10 mL measuring cylinder
2. Add 10 mL of the biodiesel to the measuring cylinder
3. Reweigh the measuring cylinder and the biodiesel
Table of mass results
Item
Mass in grams
mass of empty measuring cylinder
mass of measuring cylinder plus 10 mL biodiesel
mass of 10 mL of biodiesel
(i) Determine the density of biodiesel in g mL-1
(b) Effect of temperature on flow rates
1. Fill one test tube with Biodiesel nearly filled up to about 1.0 cm from the top
2. Fill another test tube to the same level with petrodiesel (do this step in a fume
cupboard).
3. Securely place a rubber stopper in each test tube.
4. Measure the temperature of the room and invert each test tube, recording the time it
takes for the air bubble to reach the top of the test tube in your results table.
5. Place each test tube into an ice/water bath and allow the temperature to equilibrate
(around 10 mins), then repeat step 4 at the lower temperature (record the temperature
of the ice/water bath).
6. Place each test tube into a beaker of warm water (around 35˚C) and allow the
temperature to equilibrate. Measure the temperature of the water, then repeat step 4.
Table of time taken (sec) for bubble to reach top of test tube when inverted for biodiesel
and petrodiesel at various temperatures.
Temperature (˚C)
Ice/Water bath (3˚C)
Room temperature
Warm water (51˚C)
Biodiesel
Petrodiesel
00.00.65 sec
00.43.10 sec
00.00.79 sec
00.01.17 sec
00.00.75 sec
00.00.78 sec
00.00.65 sec
00.00.69 sec
00.00.75 sec
00.00.79 sec
00.00.78 sec
00.00.94 sec
Biodiesel produced by transesterification of triglycerides