Food Waste and Catering Waste; Focus on Valorisation of Used Cooking Oil and Recovered Triglycerides - The Economic Utilisation of Food Co-Products - page 125

OH

O

HO OH

O HO

O

+H 2 O

OH

H+/Heat

ACROLEIN

2-ethylen-1,3-dioxolane
-4-methanol

OH

HO

d n 9 r 3 n g | 0

H+/Heat

+H 2 O

O

GLYCEROL

H 2 /catalyst

HO

ACETOL

O

HO

d y y f n n 3 .

O

2-ethyl-1,3-dioxolane
-4-methanol

Scheme 6.18 General conditions for the one-pot 1) dehydration/ acetalisation; 2)
hydrogenolysis of glycerol.

would be achieved by reacting the triol into acrolein or acetol at high working
temperatures followed by further condensation with the remaining glycerol, as
shown in Scheme 6.18.
The synthesis would combine the dehydration of glycerol to a carbonyl
compound with the formation of acetal/hydrogenation or vice versa.
Both the hydrogenation/acetalisation and condensation of glycerol with
carbonyl compounds have been reported in literature. Pd/C catalysts have been
employed for the hydrogenolysis of glycerol and conversion into hemiacetals at
mild temperature and H 2 pressure conditions. 191 Another interesting process
published by Mota is the use of zeolites with medium Si/Al ratio leading to
the acetalisation of glycerol with carbonyl compounds such as acetone or
formic acid. 192 In addition, Peinado also reported a combined acetalisation/
esterification process using acid conditions and producing interesting chemicals
for potential use as fuel additives. 193

6.6.11 Glycerol Carbonate
Glycerol carbonate is another chemical worthy of note. It has the potential to
substitute petrochemically derived propylene carbonate in applications such as
a green solvents, or precursors for epoxy resins and polyurethanes, (poly-
urethane market demand is estimated to be d 4.9 billion in the U.S. alone 194 and
it keeps increasing in emerging economies). Glycerol carbonate can also be
employed for the production of oligoglycerols and oligoglycerol esters (with
application as antifogging agents) and for the production of chemicals such as
glycidol. Its current production involves the hydrolysis of epichlorohydrin, via
the glycerol (Epicerol process), or from propylene. Established routes to
glycerol carbonate from glycerol may involve the use of noxious chemicals such
as phosgene, 195 therefore new and greener routes are desirable. Examples of
such routes could include the use of organic carbonates [Dimethyl carbonate
(DMC): (Scheme 6.19)], supercritical CO 2 (Scheme 6.21) or urea (Scheme 6.22)