Chemistry Reference
In-Depth Information
Table 15.5
Comparison of different degumming methods.
PLA/PLC
enzymatic
refining
Caustic
refining
PLA enzymatic
refining
Starting phos. level in crude oil
500 ppm
500 ppm
500 ppm
Phos. level after centrifuge
2 ppm
2 ppm
2 ppm
Centrifuge discharge (dry %)
3.19
1.13
0.62
Yield of oil (%)
96.5
97.4
98.3
degumming step but still gives an overall good reduction in phosphorus content. Table
15.5 compares the original caustic process with the two enzymatic options and suggests
that combined enzyme addition may be a useful route until more efficient phospholipase C
enzymes become available.
15.7
ESTER SYNTHESIS
Fatty acid esters are produced from vegetable oil and some are used as ingredients in skin
care and other cosmetic products. The conventional production of fatty acid esters is based
on catalysis with either tin or acid at high temperature. Novozym 435 is a lipase that is able
to catalyze the conversion of vegetable oil to specific fatty acid esters. In this approach, the
traditional tin catalyzed process can be substituted with an enzymatic process using Novozym
435 (Fig. 15.16).
The advantages of this approach are considerably lower operating temperatures, a reduced
energy demand and less formation of by-products. When operating this type of synthesis, the
released water must be removed as this will limit the conversion to the ester. As water levels
build up within the system, the synthesis reaction slows and eventually hydrolysis of the
ester will occur (Fig. 15.17). In industrial operation this is achieved by operating at reduced
pressure or by the addition of molecular sieves (MS) to remove the water.
The purity of the products produced by enzymatic synthesis is much higher than from the
conventional chemical process. A comparison of the purity of myristyl myristate produced
by tin or enzyme-catalyzed reactions was made by Thum
26
and is shown in Table 15.6.
The product from enzymatic synthesis had the same melting properties as the conventional
one but the colour formation was lower and the overall yield higher. The production of cetyl
ricinoleate was also considered and an overall yield improvement noted (93% compared to
61%). In addition, not only was the synthesis of dimer reduced but the level of unknown
materials as illustrated by the base line on the chromatograph was also lower, indicating an
overall purer product (Fig. 15.18).
Lipase
Isopropylalcohol
O
O
OH
O
H
2
O
Fig. 15.16
Lipase catalyzed ester synthesis of isopropyl myristate.
