Environmental Engineering Reference
In-Depth Information
α
-Pinene
β
-Pinene
3-Carene
Camphene
Myrcene
Limonene
HO
O
α
-Terpinene
Carvone
Menthol
O
Te rpenoids
p
-Cymene
Dihydrocarvone
Figure 5.3
Structures of common monoterpenes and terpenoids, all produced by manipula-
tion of pinenes [117-119].
5.4.1
Production of Turpentine
Turpentine is a mixture of mainly α-pinene and β-pinene and other monoterpe-
nes that constitute only a small fraction of the mixture [117]. Turpentine is the
volatile fraction of pine resin and is obtained by steam-distillation of the resin;
the non-volatile residue left after this process is rosin (Section 5.5). Turpentine
is classified by the method used to isolate the pine resin. The two main classes
are gum pine resin, acquired by tapping living trees, and sulphate pine resin,
obtained during the Kraft pulping of pine wood [117]. The majority of the pine
resin is isolated using the latter technique [117]. The composition of turpentine
is dependent on a number of factors, including tree species, geographic loca-
tion, and isolation method. Typical compositions range from α-pinene between
45 and 95% and β-pinene between 0.5 and 28% [117]. Approximately
300,000 tons of turpentine are produced annually, though currently a large
portion of the turpentine produce is not used as a monomeric material [117]. A
number of interesting terpenes can be isolated from the volatile fractions of
plant oils, such as: caryophyllene and humulene from clove or hop oils;
carvone, a terpenoid, from spearmint and caraway oils; and limonene from
citrus peel oil [123-125]. These oils are produced on an industrial scale of
10
4
tons per year [123, 124].
