Chemistry Reference
In-Depth Information
Bio-diesel production generates about 10% (w/w) glycerol as its main by-
product. For every gallon of bio-diesel produced, approximately 1.05 pounds
of glycerol is generated. By 2016, 37 billion gallons of bio-diesel will be pro-
duced which translates into the production of 4 billion gallons (38.8 billion
pounds) of crude glycerol.
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Refined glycerol sells for about US$0.30 per lb,
compared to the US$0.70 it sold for prior to the expansion of the USA bio-
diesel market. The price of crude glycerol is about US$0.05 per lb.
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Crude
glycerol is currently being used as a feedstock for production of other value-
added chemicals and animal feeds.
57,58
Utilization of crude glycerol to pro-
duce citrate glycerides has been demonstrated and will go further towards
decreasing the cost of manufacturing this polyester.
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Citric acid has wide applications in numerous fields and can be produced
from a variety of low-cost sugar substrates by fermentation.
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Citric acid is
inexpensive, bio-degradable and non-toxic.
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Citric acid is one of most
widely produced organic chemical commodities. Global production of citric
acid was 1.5million tons in 2005 and steadily increased to 1.8million tons in
2010.
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Because of its ease of manufacturing by fermentation it is con-
siderably less expensive than other tri- or diacids which are more complex to
manufacture and employ higher priced ingredients (Table 7.3). Clearly,
coupling these two low-cost ingredients to produce low-priced polyesters is a
way of competing with current bio- and petroleum-based plastics.
7.4 Preparation of Carboxylic acid Glycerol Polyesters
Several novel carboxylic acid glycerol polyesters have been produced with
unique thermal and mechanical properties.
24,26,35,41,43,44,64
Generally, the
procedurefollowedtoproducedpolyesters, see Scheme 7.1, involves mix-
ing the carboxylic acid and glycerol in various monomeric ratios (usually
1 : 1 M), and heating close to the melting point of the carboxylic acid until
the polycondensation reaction has occurred suciently to allow for
Scheme 7.1 Esterification of glycerol and citric acid to produce citrate glycerides.
The citrate glyceride structure presented is theoretical.
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