3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
Results and Discussion
P r e p a r a t i o n o f T O
TO was prepared by TS acidification by sulphuric acid
at conditions given in Table I. Sulphuric acid was added
in excess. Reaction mixture undergoes vigorous agitation
during the process.
At the beginning, about 1,000 g TS (one batch) was
heated in a 4,000 ml beaker in water bath. Temperature of
water bath was kept in the range of 90–95 °C by adjustable
cooker. After heating of TS at the water bath temperature,
sulphuric acid was added and a blender activated. The blender
ensured intensive agitation during the whole process. At
TO preparation, the following reaction proceeded:
R—COOna + H 3 O + → R—COOH + H 2 O + na +
Scheme 1
Conversion of saponified HFA to acid form
Volume of obtained tall oil after separation of aqueous and
a lignin phase from one batch was 482 ml or 465 g, and the yield
in % wt. was 70.9.
Having concluded the process, phase separation was
performed. TO was separated from aqueous and lignin phases
by separatory. Subsequently, warm water was used to wash
TO, until pH of waste water reached ∼ 6–7 due to necessity
to eliminate H 2 SO 4 residues from esterified oil. Finally, TO
was dehydrated in a vacuum rotary evaporator.
Preparation of tall oil was performed using two apparatus
simultaneously. For totally 3.3 h, 2 × 482 ml of oil after
separation of aqueous and lignin phase was obtained. This
process was repeated 6 times and a total amount of prepared
oil was ~ 5,784 ml (5,580 g). A total amount of TS used in the
process was ~ 7,867 g (besides moisture).
Average batch yield reached 70.93 % wt. Theoretical
yield was 84.0 % wt., i.e. weight loss was 13.07 % wt. This
amount included the matter remaining on the beaker and funnels
walls owing to a decrease in temperature and increase in
viscosity of tall oil. The inner surface of 4,000 ml beaker and
2,000 ml separatory funnel was significant.
Moreover, not all saponificed HFA and RA were converted
to their acid form by the reaction shown in Scheme 1.
G C / M S A n a l y s i s o f T O
The prepared TO contained 30 % wt. HFA, 20 % wt.
RA, ~ 18.5 % sterols. non-analysed portion represented
~ 44.2 % wt. and contained higher fatty alcohols, hydrocarbons,
lignin and cellulose fragments, non-methylated fatty
and resin acids and inorganic compounds. These substances
cannot be classified into the above three groups. In addition,
these substances could be modified by the preparation process
or its conditions.
s553
Table IV
GC/MS analysis – composition of tall oil
Extractives [% wt.]
Fatty acids 29.8
Resin acids 20.0
Sterols 6.0
Analysed portion 55.8
non-analysed portion 44.2
Total 100.0
E s t e r i f i c a t i o n o f T a l l O i l
– P r e p a r a t i o n o f T a l l O i l
M e t h y l e s t e r s ( T O M E )
The prepared TO, after washing by water and dehydratation
were subjected to esterification at optimal conditions
based on neaves D.E. 11 .
R C
O
O H
R C
+
-
H +
H -
OH
O +
OH
H
OH
R C +
H
- H2O -
H +
O
R C
Mechanism of acid catalysed esterification by methanol
is proposed in Scheme 2. Conditions of esterification are
summarized in Table II.
1,000 g TO with HFA content ~ 30 % wt. i.e. ~ 300 g
was processed. As catalyst, suphuric acid ~ 15 g (8.2 ml at
density 1.835 g cm –3 ) was used. The total amount of methanol
added to the reactor was ~ 204.8 ml (methanol was added
in excess to HFA, in molar ratio 6 : 1)
Average molar mass of fatty acids was estimated as
281.55 g mol –1 . Stemming from the fact that optimal conditions
(time 2–3 h) given by literature concern only the fraction
HFA isolated from TO and not the fraction included in
TO, reaction time was prolonged to 5.5 h to ensure maximum
conversion.
The process was repeated 3 times and total volume of
prepared TOME approached 3,000 ml (2,835 g).
H
O
CH 3
H3C Scheme 2
Mechanism of HFA esterification with methanol in acid media
+
O
O CH 3