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Assessment of crude glycerol utilization for sustainable development of biorefineries 203

Citric acid is widely used organic acid in the field of food industry as a flavoring
agent and in pharmaceutical industry as a polishing agent (Handojo et al., 2019).
Yarrowia lipolytica is the most commonly studied organism for the production of
citric acid from glycerol. The maximum yield of 62.5 g/L of citric acid was pro-
duced by Y. lipolytica under nitrogen limitation condition (Papanikolaou et al.,
2008). Higher citric acid concentrations (more than 100 g/L) were attained with
acetate-negative mutants strain of Y. lipolytica using crude glycerol as the substrate
(Rymowicz et al., 2010; Rywinska and Rymowicz, 2010). Many other products,
such as succinic acid, dihydroxyactone, and pigments, can also be produced from
the glycerol. The value-added products produced through microbial fermentation of
glycerol are displayed in Table 9.2.

9.4.2 Chemical route

9.4.2.1 Acrolein
Acrolein is the simplest unsaturated aldehyde also known as 2-propenal or acrylic
aldehyde (Fan et al., 2010). It can be produced from glycerol via aqueous dehydra-
tion process with the presence of the catalyst (Alhanash et al., 2010). Acrolein finds
its application as a raw material of acrylic acid, medicines, fiber treatment, methio-
nine, fragrance, and dyes, as a slimicide in the production of paper and as a micro-
bicide in oil wells (Kong et al., 2016). A percentage of 85 acrylic acid is produced
through conventional acrolein oxidation in the world and mostly used in hygienic
pads and diapers by exhibit super adsorbent properties.
Watanabe et al. (2007) produced acrolein from glycerol in hot compressed water
using a batch and flow apparatus. The addition of acid catalyst helps to maintain
the rate constant of acrolein formation which is always higher than that of decom-
position. Percentages of 74 acrolein yield and 81 its selectivity were obtained with
the catalyst in the supercritical condition. Cheng et al. (2013) comparatively recon-
noitered impurities effect on the direct conversion of pure and crude glycerol to
acrolein using sulfuric acid under subcritical water condition. Less than 80 mol% of
acrolein yield was obtained in both crude and pure glycerol at the temperature rang-

ing 335 C 380 C in the presence of 45 50 mM H 2 SO 4 . Bub et al. (2006) reported
that dehydration of glycerol is carried out at 300 C with Zr as a catalyst. A percent-

age of 72 gas phase dehydration of glycerol conversion of acrolein is achieved.
9.4.2.2 Epichlorohydrin

Epichlorohydrin is an organochlorine compound and an epoxide and was first
described in 1848 by Marcellin Berthelot. The compound was isolated on reactions
between glycerol and gaseous hydrogen chloride. It is a colorless liquid with pun-
gent order, moderately soluble in water and miscible with the most polar organic
solvent. It acts as a building block for the manufacture of epoxy resins and also pre-
cursors for monomer and polymer of other resins.