Separation of 3-carene and limonene by azeotropic distillation

3-Carene and limonene cannot be separated from each other by rectification because of the closeness of their boiling points. They are readily separated by azeotropic distillation. Effective agents are: cyclopentanol, 2-nitropropane, ethyl formate amyl acetate dimethyl carbonate, tetrahydrofuran, acetic acid and 2-amino-amethyl-1-propanol.

WORKING EXAMPLES 
1. One hundred grams of a crude turpentine mixture containing principally 
3-carene, limonene and phellandrene and 100 grams of amyl acetate were 
charged to the stillpot of five theoretical plate glass perforated plate 
rectification column and operated at total reflux for nine hours. The 
overhead composition was 94% 3-carene, 4% limonene and 2% phellandrene; 
the stillpot composition was 48% 3-carene, 32.1& limonene and 19.9% 
phellandrene. This indicates a relative volatility of 3-carene to limonene 
of 1.65 and limonene to phellandrene of 1.04. 
2. Twenty grams of 3-carene, 80 grams of limonene and 100 grams of 
cyclopentanol were charged to the five theoretical plate perforated plate 
rectification column and operated at total reflux for nine hours. The 
overhead composition was 74.9% 3-carene, 25.1% limonene; the stillpot 
composition was 21.6% 3-carene, 78.4% limonene. This indicates a relative 
volatility of 1.6. 
3. One hundred grams of the crude turpentine mixture of 3-carene, limonene 
and phellandrene and 100 grams of dimethylformamide were charged to the 
five theoretical plate rectification column and refluxed for nine hours. 
The overhead composition was 88.9% 3-carene, 8.3% limonene and 2.8% 
phellandrene; the stillpot composition was 51.6% 3-carene, 13.7% limonene 
and 34.7% phellandrene. This indicates a relative volatility of 3-carene 
to limonene of 1.24 and of limonene to phellandrene of 1.5.