Page 235 - Refining Biomass Residues for Sustainable Energy and Bioproducts

Assessment of crude glycerol utilization for sustainable development of biorefineries 205

Almena and Martı ´n (2015) stated that epichlorohydrin formation consists of four
stages: purification of crude glycerol, its reaction to mono and dichlorohydrins and
their separation, epichlorohydrin production, and final product purification. On
using the process integrated MATLAB 10% higher yield (80.5% vs 73% related to
the mass of pure glycerol fed to the plant) was achieved in the proposed current
industrial process. Lari et al. (2018) stated in his study that solid and recyclable
base can be used as an alternative source to alkali hydroxide catalyst for the epi-
chlorohydrin production from dehydrochlorination of glycerol. The optimization of
space velocity and controlling the temperature below 423K enable the yield as high
as 60%. In the established technologies the production of epichlorohydrin by using
a heterogeneous catalyst such as heteropolyacid at 110 C and 5 bar pressure in 5 h

reaction time could convert 49.7% of dihydrochloride (Lee et al., 2008).
Comparably, Song et al. (2010) achieved 50.9% of epichlorohydrin from dihy-
drochloride in the presence of a heteropolyacid catalyst in a solid phase gas reactor

at 250 C.
9.4.2.3 Triacetin
Triacetin is also known as 1,2,3-triacetoypropane or glycerin triacetate. It is the
ester of glycerol that forms with acetic acid. Triacetin can be produced through the
acid-catalyzed reaction of acetic acid or acetic anhydride with glycerol. Triacetin
finds its application in pharmaceutical, cosmetic, and fuel additives as an anti-
knocking agent to minimize the engine knocking. It is used in biofuel to increase in
cetane number and to decrease the nitrogen oxide emission (Melero et al., 2007).
Zhu et al. (2013) proposed silver-exchanged phosphotungstic acid (AgPW) cata-
lysts for glycerol acetylation with acetic acid. Partially, silver-exchanged phospho-
tungstic acid (Ag1PW) showed high activity and good performance in the reaction.

The conversion of glycerol is 96.8% at 120 C within 15 min of reaction time. The
reason is that Ag1PW shows remarkable stability, unique kegging structure, high
acidity, and excellent water-tolerance property. The selectivity of acetylated pro-
ducts is 5.2% for triacetin, 46.4% for diacetin, and 48.4% for monoacetin. Mufrodi
et al. (2012) stated that the crude glycerol and acetic acid in the presence of the sul-
furic acid catalyst at the temperature of 111 C on the reaction time 90 min yields

selectivity of triacetin 77.84%. In the exothermic reaction the production of triace-
tin increases with increase in reaction temperature since acetic acid starts to evapo-
rate when the temperature is decreased. Sun et al. (2016) investigated that the use
of magnetic solid acid catalyst for efficient conversion of glycerol to triacetin with
22
acetic anhydride. Stannic chloride pentahydrate Fe Sn Ti (SO ) catalyst aids
4
100% conversion of glycerol and 99% selectivity of triacetin under an optimized
temperature of 80 C and reaction time 30 min.

9.4.3 Alternate uses

The crude glycerol, as a major byproduct during biodiesel production, consists of a
copious amount of impurities which inhibits its direct usage in industries. However,