Extracting Limonene from Orange Peel

Aim

To extract the essential oil limonene (D-limonene) from orange peel using steam distillation.
Note: there are two isomers of limonene, D-limonene and L-limonene. They are stereo-isomers. D-limonene smells like citrus while L-limonene smells like turpentine.

Procedure

1. Cut and discard away the white pith from the orange peel, leaving the orange rind, as the orange portion contains the limonene.

2. Measure and record the mass of the orange peel in a clean pre-weighed container.

3. Blend the orange peel with a suitable amount of distilled water until a smooth, thick texture is achieved.

4. Transfer all the blended mixture into a clean 250ml round-bottomed flask using a spoon and filter funnel.

5. Set the steam distillation apparatus as shown. Turn on the hotplate and tap water for the condenser. Observe the temperature of the vapour as indicated in the thermometer.

6. Collect the distillate in a clean beaker.

7. Transfer the distillate into a clean boiling tube and immerse it into a hot water bath of 80°C. When distillate settles, the limonene will rise to the top of the tube, forming two distinct layers with water at the bottom.

8. Pour the limonene at the top of the tube into a clean pre-weighed test tube. Measure and record the mass of the limonene.

Results

Mass of orange peel used/g = 50.50g
Mass of D-limonene extracted/g = 1.20g

Percentage yield = 1.20/50.50 x 100 = 2.38% (2 d.p.)

Although the process is not very efficient, D-limonene is considered to have a rather high percentage yield as most essential oils usually have a percentage yield of 0.5% to 2%.

Behind the scenes

Essential oils like D-limonene are beneficial because they carry anti-carcinogenic properties and have multiple purposes, such as in cleansing products. Furthermore, the orange peel that we usually throw away can now be reused to produce D-limonene, a biofuel.

The process used in extraction of D-limonene is steam distillation. This does not denature the existing structure of D-limonene, but instead the hot steam opens up pockets in the orange peel containing the oils. Aromatic molecules of the volatile oil then escapes from the peel, forming vapours before condensing.